Author name code: schmieder ADS astronomy entries on 2022-09-14 =author:"Schmieder, B." OR =author:"Schmieder, Brigitte" ------------------------------------------------------------------------ Title: Solar jets observed with the Interface Region Imaging Spectrograph (IRIS) Authors: Schmieder, Brigitte; Joshi, Reetika; Chandra, Ramesh Bibcode: 2022AdSpR..70.1580S Altcode: 2021arXiv211109002S Solar jets are impulsive, collimated plasma ejections that are triggered by magnetic reconnection. They are observed for many decades in various temperatures and wavelengths, therefore their kinematic characteristics, such as velocity and recurrence, have been extensively studied. Nevertheless, the high spatial resolution of the Interface Region Imaging Spectrograph (IRIS) launched in 2013 allowed us to make a step forward in the understanding of the relationship between surges and hot jets. In this paper we report on several results of recent studies of jets observed by IRIS. Cool and hot plasma have been detected with ejections of cool blobs having a speed reaching 300 km s-1 during the impulsive phase of jet formation and slow velocity surges surrounding hot jets after the reconnection phase. Plasma characteristics of solar jets, such as the emission measure, temperature, and density have been quantified. A multi-layer atmosphere at the reconnection site based on observed IRIS spectra has been proposed. IRIS evidenced bidirectional flows at reconnection sites, and tilt along the spectra which were interpreted as the signature of twist in jets. The search of possible sites for reconnection could be achieved by the analysis of magnetic topology. Combining Solar Dynamics Observatory/Helioseismic Magnetic Imager (SDO/HMI) vector magnetograms and IRIS observations, it was found that reconnection site could be located at null points in the corona as well as in bald patch regions low in the photosphere. In one case study a magnetic sketch could explain the initiation of a jet starting in a bald patch transformed to a current sheet in a dynamical way, and the transfer of twist from a flux rope to the jet during the magnetic reconnection process. Title: Over-expansion of coronal mass ejections modelled using 3D MHD EUHFORIA simulations Authors: Verbeke, Christine; Schmieder, Brigitte; Démoulin, Pascal; Dasso, Sergio; Grison, Benjamin; Samara, Evangelia; Scolini, Camilla; Poedts, Stefaan Bibcode: 2022AdSpR..70.1663V Altcode: 2022arXiv220703168V Coronal mass ejections (CMEs) are large scale eruptions observed close to the Sun. They are travelling through the heliosphere and possibly interacting with the Earth environment creating interruptions or even damaging new technology instruments. Most of the time their physical conditions (velocity, density, pressure) are only measured in situ at one point in space, with no possibility to have information on the variation of these parameters during their journey from Sun to Earth. Our aim is to understand the evolution of internal physical parameters of a set of three particular fast halo CMEs. These CMEs were launched between 15 and 18 July 2002. Surprisingly, the related interplanetary CMEs (ICMEs), observed near Earth, have a low, and in one case even very low, plasma density. We use the EUropean Heliosphere FORecasting Information Asset (EUHFORIA) model to simulate the propagation of the CMEs in the background solar wind by placing virtual spacecraft along the Sun--Earth line. We set up the initial conditions at 0.1 au, first with a cone model and then with a linear force free spheromak model. A relatively good agreement between simulation results and observations concerning the speed, density and arrival times of the ICMEs is obtained by adapting the initial CME parameters. In particular, this is achieved by increasing the initial magnetic pressure so that a fast expansion is induced in the inner heliosphere. This implied the develop First, we show that a magnetic configuration with an out of force balance close to the Sun mitigates the EUHFORIA assumptions related to an initial uniform velocity. Second, the over-expansion of the ejected magnetic configuration in the inner heliosphere is one plausible origin for the low density observed in some ICMEs at 1 au. The in situ observed very low density has a possible coronal origin of fast expansion for two of the three ICMEs. Title: Prominence oscillations activated by an EUV wave Authors: Devi, Pooja; Chandra, Ramesh; Joshi, Reetika; Chen, P. F.; Schmieder, Brigitte; Uddin, Wahab; Moon, Yong-Jae Bibcode: 2022AdSpR..70.1592D Altcode: 2022arXiv220213147D Prominence oscillations are one of interesting phenomena in the solar atmosphere, which can be utilized to infer the embedded magnetic field magnitude. We present here the transverse oscillations of two different prominences located at the East solar limb on 2011 February 11 using the multi-wavebands data of the Atmospheric Imaging Assembly (AIA) on-board the Solar Dynamics Observatory (SDO) satellite. A prominence eruption was observed towards the east direction with an average speed of ≈ 275 km s-1. The eruption is fitted with the combination of a linear and an exponential functions of time. An extreme ultraviolet (EUV) wave event was associated with the prominence eruption. This EUV wave triggered the oscillations of both prominences on the East limb. We computed the period of each prominence using the wavelet analysis method. The oscillation period varies from 14 to 22 min. The magnetic field of the prominences was derived, which ranges from 14 to 20 G. Title: Preface: Magnetic flux ropes in solar environments Authors: Mandrini, Cristina H.; Schmieder, Brigitte Bibcode: 2022AdSpR..70.1547M Altcode: Magnetic flux bundles or ropes are the main building blocks forming active regions. Their destabilization can lead to the most violent events - flares, coronal mass ejections (CMEs), and energetic particle events. After eruption, they are observed over a wide range of spatial scales throughout the heliosphere. Specific configurations of these structures can produce the strongest geomagnetic storms as they impact the Earth's magnetosphere. Title: New Insight into UV Compact Bursts - Statistical Analysis of IRIS Data Authors: Berlicki, Arkadiusz; Heinzel, Petr; Schmieder, Brigitte; Michalina Litwicka, M. Bibcode: 2022cosp...44.2532B Altcode: UV small-scale brightenings have been frequently observed by IRIS in both NUV and FUV channels. They appear as compact and intense, but short lived bursts visible within the solar active regions. Some of them seem to be closely connected with the well-known Ellerman bombs and so-called IRIS bombs. Based on the IRIS observations of many compact bursts obtained in chromospheric Mg II h and k lines, Mg II triplet and FUV lines we present detailed statistical analysis of these phenomena. In the work of Grubecka et al. (2016), five different compact bursts (CBs) were selected and analysed in detail. NLTE semi-empirical models of them were constructed based on their spectral characteristics in the Mg II h and k lines. In addition, they were preliminarily categorised into three types. In present work we extend previous analysis and investigate statistical diversity of Mg II lines of UV bursts and their visibility in FUV lines such as Si IV or C II. IRIS database from 2013-2018 was searched for dense rasters of active and emerging flux regions containing spectra in Mg II, C II and Si IV. A next step was to reconstruct full rasters in which we were looking for compact brightenings with size of the order of one arcsec. We found more than two thousands CBs using criteria based on specific parameters of the Mg II k line profile. In addition, we analysed also the emission of Mg II UV triplet and some parameters of Si IV and C II lines. This database allowed us to make a novel statistical analysis of all bursts and we categorised them in previously defined three types, depending on their Mg II line profiles shapes. We also investigated the correlations between the emission of Mg II lines, "hotter" Si IV lines, and C II lines in order to find which of these events are linked with IRIS bombs (Peter et al. 2014). Finally, we analysed some observables of those UV bursts, which can be defined as candidates for Ellerman bombs. Title: EUHFORIA modeling of slow CMEs with well-defined magnetic signatures Authors: Prete, Giuseppe; Carbone, Vincenzo; Wijsen, Nicolas; Poedts, Stefaan; Schmieder, Brigitte; Esteban Niemela, Antonio; Lepreti, Fabio Bibcode: 2022cosp...44.2467P Altcode: Coronal mass ejections (CMEs) are one of the main drivers of strong space weather disturbances. The interaction between CMEs and the Earth's magnetic field can cause a wide range of phenomena and the magnetic configuration and orientation are key factors in determining the geo-effectiveness of this type of events. Modeling these events accurately is an ongoing challenge, and data-driven simulations are a valuable operational and research tool, widely used by the community. Using the 3D data-driven magneto-hydrodynamical (MHD) heliospheric solar wind and CME evolution model EUHFORIA (European Heliospheric FORecasting Information Asset), our aim is to model two CME events previously investigated by Al-Haddad et al. (2018). These particular events are characterized by propagation slow velocities and well-organized magnetic field characteristics. We also explore how these structures affect Earth, even in the absence of an ICME. Title: Fan-shaped jet close to a light bridge Authors: Liu, Y.; Ruan, G. P.; Schmieder, B.; Masson, S.; Chen, Y.; Su, J. T.; Wang, B.; Bai, X. Y.; Su, Y.; Cao, Wenda Bibcode: 2022arXiv220713246L Altcode: On the Sun,jets in light bridges are frequently observed with high-resolution instruments.The respective roles played by convection and the magnetic field in triggering such jets are not yet clear.We report a small fan-shaped jet along a LB observed by the 1.6m Goode Solar Telescope(GST) with the TiO Broadband Filter Imager(BFI),the Visible Imaging Spectrometer(VIS) in H{\alpha},and the Near-InfraRed Imaging Spectropolarimeter(NIRIS),along with the Stokes parameters.The high spatial and temporal resolution of those instruments allowed us to analyze the features identified during the jet event.By constructing the H{\alpha} Dopplergrams,we found that the plasma is first moving upward,whereas during the second phase of the jet,the plasma is flowing back.Working with time slice diagrams,we investigated the propagation-projected speed of the fan and its bright base.The fan-shaped jet developed within a few minutes,with diverging beams. At its base,a bright point was slipping along the LB and ultimately invaded the umbra of the sunspot.The H{\alpha} profiles of the bright points enhanced the intensity in the wings, similarly to the case of Ellerman bombs.Co-temporally,the extreme ultraviolet brightenings developed at the front of the dark material jet and moved at the same speed as the fan, leading us to propose that the fan-shaped jet material compressed and heated the ambient plasma at its extremities in the corona.Our multi-wavelength analysis indicates that the fan-shaped jet could result from magnetic reconnection across the highly diverging field low in the chromosphere,leading to an apparent slipping motion of the jet material along the LB.However,we did not find any opposite magnetic polarity at the jet base,as would typically be expected in such a configuration.We therefore discuss other plausible physical mechanisms,based on waves and convection, that may have triggered the event. Title: Coronal Seismology using the loops Oscillations triggered by an EUV wave Authors: Devi, Pooja; Awasthi, Arun Kumar; Chandra, Ramesh; Joshi, Reetika; Schmieder, Brigitte Bibcode: 2022cosp...44.2489D Altcode: Coronal seismology is widely utilized to infer the magnetic field characteristics in the solar corona. Here, we investigate multiple aspects of the eruptive activities that occurred in active region NOAA 12287 during a GOES X1.0 class flare on October 28, 2021. This includes a filament eruption and associated Extreme Ultraviolet (EUV) wave. The erupted filament material apparently perturbed the surrounding coronal structures. Interestingly, the associated EUV wave triggered oscillations in several nearby loop systems. By probing various oscillation characteristics e.g. time period, amplitude, density, temperature, decay time etc., in the different loops systems, we infer the characteristics of the magnetic field that essentially surrounds the eruptive active region and compare it with the previous observations and theories. Title: Solar prominence diagnostics from non-LTE modelling of Mgii h&k line profiles Authors: Peat, Aaron; Labrosse, Nicolas; Barczynski, Krzysztof; Schmieder, Brigitte Bibcode: 2022cosp...44.2542P Altcode: We investigate a new method to obtain the plasma parameters of solar prominences observed in the Mg II h&k spectral lines by comparing line profiles from the IRIS satellite to a bank of profiles computed with a one-dimensional non-LTE radiative transfer code. The prominence observations were carried out by the IRIS satellite on 19th April 2018. Using a grid of 22933 one-dimensional non-LTE radiative transfer models, some including a prominence-corona transition region (PCTR), we are able to recover satisfactory matches in areas of the prominence where single-line profiles are observed. Large values of ionization degree are found by the procedure in areas where the line of sight crosses mostly plasma from the PCTR, correlating with high mean temperatures and correspondingly no H$\alpha$α emission. The models were unable to recover satisfactory fits in the regions where we see H$\alpha$ emission. This is due to the complex line shapes manifesting from many unresolved independently moving threads. This new method naturally returns information on how closely the observed and computed profiles match, allowing the user to identify areas where no satisfactory match between models and observations can be obtained. The inclusion of the PCTR was found to be important, as regions where satisfactory fits were found were more likely to contain a model encompassing a PCTR. Title: Detection of Large Amplitude Oscillations in Solar Filaments Caused by Jets Authors: Joshi, Reetika; Chandra, Ramesh; Moreno-Insertis, . Fernando, , Prof; Luna, Manuel; Schmieder, Brigitte Bibcode: 2022cosp...44.2417J Altcode: Large amplitude oscillations (LAOs) are often observed in prominences/filaments. Their origin has been associated with shock waves or their interaction with jets and other eruptions. In this study, we present two examples of LAOs due to the interaction of solar jets with filaments on February 3-5 2015 and March 14 2015. The filament eruption on March 14 was followed by a two step filament eruption along with a CME which led to the strongest geomagnetic storm of Solar Cycle 24 on 17 March 2015. These LAOs are analysed by using time-distance diagnostics. The detected LAOs have periods of around 60 minutes and are damped after three oscillations. The observations are consistent with the results of a recent developed theoretical model of jet and filament/fluxrope interaction. The jets are associated with very weak flares which did not initiate any EUV wave. The role of waves as trigger of these oscillations can be discarded for these two events. Title: Formation of a flux rope inside an active region and its failed eruption Authors: Schmieder, Brigitte; Mandrini, Cristina H.; Chandra, Ramesh; Mac Cormack, Cecilia; Joshi, Reetika; Cristiani, German Bibcode: 2022cosp...44.2418S Altcode: In the standard flare model a flux rope is formed in an active region. After reconnection of the magnetic field lines, the flux rope rises and is expelled as a coronal mass ejection and ribbons are formed at the feet of the reconnected loops. We observed such a case, just more complicated because the region AR that we observed on May 9 2020 is a quadrupolar region . We explored the data of SDO/AIA, SDO/HMI and the high resolution IRIS slit jaws . Therefore we analyzed this case to understand the formation of the flux rope and its failed eruption. The flux rope (filament) is formed by squeezed chromospheric fibrils due flux cancellation and the eruption is also due to flux cancellation. We conjecture that the failed eruption is due to the magnetic strength of large scale loops overlaying the active region and connecting with the edge of a coronal hole. Title: Analysis of the Evolution of a Multi-Ribbon Flare and Failed Filament Eruption Authors: Joshi, Reetika; Mandrini, Cristina H.; Chandra, Ramesh; Schmieder, Brigitte; Cristiani, Germán D.; Mac Cormack, Cecilia; Démoulin, Pascal; Cremades, Hebe Bibcode: 2022SoPh..297...81J Altcode: 2022arXiv220600531J How filaments form and erupt are topics about which solar researchers have wondered for more than a century and they are still open to debate. We present observations of a filament formation, its failed eruption, and the associated flare (SOL2019-05-09T05:51) that occurred in active region (AR) 12740 using data from the Solar Dynamics Observatory (SDO), the Solar-Terrestrial Relations Observatory A (STEREO-A), the Interface Region Imaging Spectrograph (IRIS) and the Learmonth Solar Observatory (LSO) of the National Solar Observatory/Global Oscillation Network Group (NSO/GONG). AR 12740 was a decaying region formed by a very disperse following polarity and a strong leading spot, surrounded by a highly dynamic zone where moving magnetic features (MMFs) were seen constantly diverging from the spot. Our analysis indicates that the filament was formed by the convergence of fibrils at a location where magnetic flux cancellation was observed. Furthermore, we conclude that its destabilisation was also related to flux cancellation associated with the constant shuffling of the MMFs. A two-ribbon flare occurred associated with the filament eruption; however, because the large-scale magnetic configuration of the AR was quadrupolar, two additional flare ribbons developed far from the two main ones. We model the magnetic configuration of the AR using a force-free field approach at the AR scale size. This local model is complemented by a global potential-field source-surface one. Based on the local model, we propose a scenario in which the filament failed eruption and the flare are due to two reconnection processes, one occurring below the erupting filament, leading to the two-ribbon flare, and another one above it between the filament flux-rope configuration and the large-scale closed loops. Our computation of the reconnected magnetic flux added to the erupting flux rope, compared to that of the large-scale field overlying it, allows us to conclude that the latter was large enough to prevent the filament eruption. A similar conjecture can be drawn from the computation of the magnetic tension derived from the global field model. Title: Mini solar flare and jet due to small scale surface motions Authors: Joshi, Reetika; Vilmer, Nicole; Chandra, Ramesh; Heinzel, Petr; Bommier, Veronique; Schmieder, Brigitte; Aulanier, Guillaume; Tomin, James Bibcode: 2022cosp...44.2535J Altcode: Here we present the study of the fine structure and dynamics of the plasma at a jet base forming a mini-flare between two emerging magnetic fluxes (EMFs) observed with Interface Region Imaging Spectrograph (IRIS) and the Solar Dynamics Observatory instruments. This active region is an outcome of the collapse of two EMFs overlaid by arch filament systems. We observed that, before the jet an extension of the flux rope was present and a part of it was detached and formed a small bipole with a bald patch region, which dynamically became an X-current sheet over the dome of one EMF where the reconnection took place. At the time in the site of reconnection, the IRIS C II, Si IV, and Mg II line profiles present bi directional flows in a tiny region. These types of spectra are typically associated with twist, rotation, or the presence of plasma in helical structures. The tilt observed in our spectra can be explained by the presence of a helical structure at the jet base during the reconnection process due to a transfer of the twist from a flux rope in the vicinity of the jet. We also combined the observations of the Balmer continuum obtained with the IRIS (spectra and SJIs 2832 Å). The calibrated Balmer continuum was compared to non-local thermodynamic equilibrium radiative transfer flare models and the radiated energy was estimated. Assuming thick target HXR emission, we calculated the energy of the non thermal electrons detected by the Fermi/GBM and compared it to the radiated energy. The electron-beam flux estimated from Fermi/GBM between 10$ ^{9}$ and 10$ ^{10}$ erg s$ ^{-1}$ cm$ ^{-2}$ is consistent with the beam flux required in non-LTE radiative transfer models to obtain the excess of Balmer continuum emission observed in this IRIS spectra. We conclude that the bombardment of electrons could be in a region smaller than the IRIS spatial resolution. Title: Impact of the solar activity cycle on the propagation of ICMEs Authors: Perri, Barbara; Poedts, Stefaan; Schmieder, Brigitte Bibcode: 2022cosp...44.2444P Altcode: The propagation of ICMEs in the heliosphere is influenced by a great number of physical phenomena, related both to the internal structure of the ICME but also to its interaction with the ambient solar wind and heliospheric current sheet. The understanding of such phenomena is crucial to be able to improve numerical modelling and provide better space weather forecasts for the time of arrival of perturbations at Earth. As individual structures of the solar wind such as helmet streamers of high-speed streams have begun to be discussed, the influence of the long-term variability of solar activity on transient events is still not clear. Indeed, the solar magnetic field is modulated by the 11-year dynamo cycle generated inside the Sun, and then affecting the entire heliosphere structure by means of the Parker spiral and its shaping of the solar corona. We know that there are more transient events at maximum of activity and that they are usually more intense, but the exact influence of solar activity on their propagation remains to be discussed. It is becoming even more important to assess these differences as solar cycle 25 is rising, and thus many models calibrated on the minimum of activity between cycles 24 and 25 may become less accurate. We perform a theoretical study to try to answer these questions. We begin by trying to define what is an average CME at 0.1 AU, using both observations and numerical simulations. We choose a spheromak to model the CME, as it allows us to explore also the magnetic interactions along its propagation. We then use the heliospheric propagator EUHFORIA to inject the same CME in two different background wind environments: the first corresponds a very quiet minimum of activity in December 2008, the other one to a maximum of activity during a solar eclipse as seen form Earth in March 2015. We then study how the flows and magnetic structures impact the propagation of the ICME towards Earth. We also discuss the influence of the injection point with regards to specific structures such as the position of the current sheet. Title: Implementation of the Soloviev equilibrium as a new CME model in EUHFORIA Authors: Linan, Luis; Keppens, Rony; Maharana, Anwesha; Poedts, Stefaan; Schmieder, Brigitte Bibcode: 2022cosp...44.2431L Altcode: The EUropean Heliosphere FORecasting Information Asset (EUHFORIA) is designed to model the evolution of solar eruptions in the heliosphere and to accurately forecast their geo-effectiveness. In EUHFORIA, Coronal Mass Ejections (CMEs) are superposed on a steady background solar wind and injected at $r=0.1\;AU$ into a 3D time-dependent ideal magnetohydrodynamics heliospheric domain. Our study focuses on the implementation of a new CME model to improve and extend the CME models that are currently implemented, for instance by providing a more realistic geometry or a faster execution time. The novel CME model is based on an analytical solution of the Grad-Shafranov equation, called the Soloviev solution, which describes a plasma equilibrium in a toroidal geometry (Soloviev, Reviews of Plasma Physics, 1975). One of the main advantages is that magnetic field and other physical quantities like pressure and density can be determined in terms of an analytic magnetic flux formula. This flux being a polynomial function of the local coordinates, we can directly control the interior properties (in terms of shape and topology) within the cross-section of the toroid with the spherical inner boundary at $r=0.1\;AU$. Hence, in practice, the numerical computation of this model is less time consuming than the FRi3D CME model that requires the numerical solution of differential equations in each time step (Isavnin, Astrophys. J., 2016). Furthermore, our implementation offers a wide range of free parameters, including the shape of the model (aspect ratio, shape of the poloidal cross-section) to the distribution and strength of the magnetic field lines in the torus. This suffices to approach the geometry and characteristics of observed CMEs. Some parameters are limited well-defined ranges, to ensure basic physical aspects like positivity of thermodynamic quantities. After the Soloviev CME is injected into the heliospheric domain of EUHFORIA as a time-dependent boundary condition, it is self-consistently evolved by the magnetohydrodynamics equations to Earth. Finally, we present a test case CME modelled with Soloviev and compare the plasma and magnetic field predictions with the observations. This research has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0) Title: Modelling the geoeffectiveness of the CME-CME interaction event of early September 2014 Authors: Maharana, Anwesha; Scolini, Camilla; Poedts, Stefaan; Schmieder, Brigitte Bibcode: 2022cosp...44.1391M Altcode: Coronal mass ejections (CMEs) undergo interaction with other CMEs and the structures in the solar wind like high-speed streams, co-rotating interaction regions and stream interaction regions, while propagating through the heliosphere. In this study, we present the evolution of two successive CMEs that erupted from the Sun on September 8, 2014, and September 10, 2014, respectively, from AR12158. The first CME was a side hit on Earth and provided preconditioning in the heliosphere for the second CME's propagation. The second CME was predicted to be geoeffective based on the remote observations of the CME chirality and tilt. However, a mismatch in the tilt of the second CME was observed close to Earth (Cho et al., 2017), pointing to CME rotation during its propagation. The magnetic ejecta, unexpectedly, resulted in positive Bz but a geoeffective sheath was developed during the evolution and the interaction in the heliosphere that resulted in a minimum Dst ~ -100nT at Earth. Hence, the geoeffectiveness of the various sub-structures involved in this event was mis-predicted. In-situ observations taken at sparse localized points in the heliosphere pose a challenge in capturing the complete picture of the CME and solar wind dynamics. Therefore, we perform 3D MHD simulations that provide a global picture, making it convenient to probe into the interesting phenomena of this event. We use the EUropean Heliosphere FORecasting Information Asset (EUHFORIA) to model the background solar wind in 3D, launch the flux rope CMEs in it and let the CMEs evolve till Earth. In this work, we aim to reproduce the observed plasma and magnetic field properties, especially the negative Bz of the sheath and the positive Bz of the ejecta at Earth. We investigate the possible factors and processes responsible for the development of geoeffectiveness, such as CME rotation, the interplay of the two CMEs, and the interaction with the surrounding solar wind. This research has received funding from the European Union's Horizon 2020 research and innovation programme under grant agreement No 870405 (EUHFORIA 2.0) Title: Pressure balance of coronal mass ejections during their Sun-Earth journey modelled by 3D MHD EUHFORIA simulations Authors: Schmieder, Brigitte; Dasso, Sergio; Grison, Benjamin; Demoulin, Pascal; Verbeke, Christine; Scolini, Camilla; Samara, Evangelia; Poedts, Stefaan Bibcode: 2022cosp...44.2474S Altcode: The aim of this work is to understand the signatures of three coronal mass ejections (CMEs) at the Lagrange point L1 launched from the Sun between 15 and 18 July 2002. We use the EUropean Heliosphere FORecasting Information Asset (EUHFORIA) model to simulate their propagation and interaction in the background solar wind. The approach is to place virtual spacecraft along the Sun-Earth line. We set up the initial conditions at 0.1 au, modelling each CME using the linear force free spheromak model. We perform an analysis on the pressures acting within the first and the last CMEs of the series (CME1 and CME3) and investigate the role of pressure (un)balance in their expansion, while the second CME (CME2) was too compressed to be able to expand its ejecta during propagation. We find that the magnetic pressure within CME1 and CME3 was prominent at 0.1 au and rapidly decreased between 0.1 au and Earth, so that the gas pressure was progressively dominating in their extended ejecta. Title: Chromospheric Recurrent Jets in a Sunspot Group and Their Intergranular Origin Authors: Zhao, Jie; Su, Jiangtao; Yang, Xu; Li, Hui; Schmieder, Brigitte; Ahn, Kwangsu; Cao, Wenda Bibcode: 2022ApJ...932...95Z Altcode: 2022arXiv220506981Z We report on high-resolution observations of recurrent fan-like jets by the Goode Solar Telescope in multiple wavelengths inside a sunspot group. The dynamics behavior of the jets is derived from the Hα line profiles. Quantitative values for one well-identified event have been obtained, showing a maximum projected velocity of 42 km s-1 and a Doppler shift of the order of 20 km s-1. The footpoints/roots of the jets have a lifted center on the Hα line profile compared to the quiet Sun, suggesting a long-lasting heating at these locations. The magnetic field between the small sunspots in the group shows a very high resolution pattern with parasitic polarities along the intergranular lanes accompanied by high-velocity converging flows (4 km s-1) in the photosphere. Magnetic cancellations between the opposite polarities are observed in the vicinity of the footpoints of the jets. Along the intergranular lanes horizontal magnetic field around 1000 G is generated impulsively. Overall, all the kinetic features at the different layers through the photosphere and chromosphere favor a convection-driven reconnection scenario for the recurrent fan-like jets and evidence a site of reconnection between the photosphere and chromosphere corresponding to the intergranular lanes. Title: Non-LTE Inversion of Prominence Spectroscopic Observations in Hα and Mg II h&k lines Authors: Jejčič, Sonja; Heinzel, Petr; Schmieder, Brigitte; Gunár, Stanislav; Mein, Pierre; Mein, Nicole; Ruan, Guiping Bibcode: 2022ApJ...932....3J Altcode: We continued our investigation of the plasma characteristics of a quiescent prominence that occurred on 2017 March 30. The prominence was observed simultaneously by several instruments, including the Interface Region Imaging Spectrograph (IRIS) and the Multichannel Subtractive Double Pass (MSDP) spectrograph operating at the Meudon solar tower. We focused on IRIS Mg II h&k and MSDP Hα spectra, selecting 55 well-coaligned points within the prominence. We computed an extensive grid of 63,000 isothermal and isobaric 1D-slab prominence models with a non-LTE (i.e., departures from the local thermodynamic equilibrium) radiative transfer code. We then performed a 1.5D spectral inversion searching for an optimal model that best fits five parameters of the observed profiles (observables), namely, the integrated intensity of the Hα and Mg II k lines, the FWHM of both lines, and the ratio of intensities of the Mg II k and Mg II h lines. The latter is sensitive to temperature. Our results show that the prominence is a low-temperature structure, mostly below 10,000 K, with some excursions to higher values (up to 18,000 K) but also rather low temperatures (around 5000 K). The microturbulent velocity is typically low, peaking around 8 km s-1, and electron density values are of the order of 1010 cm-3. The peak effective thickness is 500 km, although the values range up to 5000 km. The studied prominence is rather optically thin in the Hα line and optically thick in the Mg II h&k lines. Title: First high resolution interferometric observation of a solar prominence with ALMA Authors: Labrosse, Nicolas; Rodger, Andrew S.; Radziszewski, Krzysztof; Rudawy, Paweł; Antolin, Patrick; Fletcher, Lyndsay; Levens, Peter J.; Peat, Aaron W.; Schmieder, Brigitte; Simões, Paulo J. A. Bibcode: 2022MNRAS.513L..30L Altcode: 2022arXiv220212434L; 2022MNRAS.tmpL..22L We present the first observation of a solar prominence at 84 - 116 GHz using the high resolution interferometric imaging of ALMA. Simultaneous observations in Hα from Białkaw Observatory and with SDO/AIA reveal similar prominence morphology to the ALMA observation. The contribution functions of 3 mm and Hα emission are shown to have significant overlap across a range of gas pressures. We estimate the maximum millimetre-continuum optical thickness to be τ3mm ≍ 2, and the brightness temperature from the observed Hα intensity. The brightness temperature measured by ALMA is ~6000 - 7000 K in the prominence spine, which correlates well with the estimated brightness temperature for a kinetic temperature of 8000 K. Title: HiRISE - High-Resolution Imaging and Spectroscopy Explorer - Ultrahigh resolution, interferometric and external occulting coronagraphic science Authors: Erdélyi, Robertus; Damé, Luc; Fludra, Andrzej; Mathioudakis, Mihalis; Amari, T.; Belucz, B.; Berrilli, F.; Bogachev, S.; Bolsée, D.; Bothmer, V.; Brun, S.; Dewitte, S.; de Wit, T. Dudok; Faurobert, M.; Gizon, L.; Gyenge, N.; Korsós, M. B.; Labrosse, N.; Matthews, S.; Meftah, M.; Morgan, H.; Pallé, P.; Rochus, P.; Rozanov, E.; Schmieder, B.; Tsinganos, K.; Verwichte, E.; Zharkov, S.; Zuccarello, F.; Wimmer-Schweingruber, R. Bibcode: 2022ExA...tmp...21E Altcode: Recent solar physics missions have shown the definite role of waves and magnetic fields deep in the inner corona, at the chromosphere-corona interface, where dramatic and physically dominant changes occur. HiRISE (High Resolution Imaging and Spectroscopy Explorer), the ambitious new generation ultra-high resolution, interferometric, and coronagraphic, solar physics mission, proposed in response to the ESA Voyage 2050 Call, would address these issues and provide the best-ever and most complete solar observatory, capable of ultra-high spatial, spectral, and temporal resolution observations of the solar atmosphere, from the photosphere to the corona, and of new insights of the solar interior from the core to the photosphere. HiRISE, at the L1 Lagrangian point, would provide meter class FUV imaging and spectro-imaging, EUV and XUV imaging and spectroscopy, magnetic fields measurements, and ambitious and comprehensive coronagraphy by a remote external occulter (two satellites formation flying 375 m apart, with a coronagraph on a chaser satellite). This major and state-of-the-art payload would allow us to characterize temperatures, densities, and velocities in the solar upper chromosphere, transition zone, and inner corona with, in particular, 2D very high resolution multi-spectral imaging-spectroscopy, and, direct coronal magnetic field measurement, thus providing a unique set of tools to understand the structure and onset of coronal heating. HiRISE's objectives are natural complements to the Parker Solar Probe and Solar Orbiter-type missions. We present the science case for HiRISE which will address: i) the fine structure of the chromosphere-corona interface by 2D spectroscopy in FUV at very high resolution; ii) coronal heating roots in the inner corona by ambitious externally-occulted coronagraphy; iii) resolved and global helioseismology thanks to continuity and stability of observing at the L1 Lagrange point; and iv) solar variability and space climate with, in addition, a global comprehensive view of UV variability. Title: Solar Jets: SDO and IRIS Observations in the Perspective of New MHD Simulations Authors: Schmieder, Brigitte Bibcode: 2022FrASS...920183S Altcode: 2022arXiv220111541S Solar jets are observed as collimated plasma beams over a large range of temperatures and wavelengths. They have been observed in H α and optical lines for more than 50 years and called surges. The term "jet" comes from X-ray observations after the launch of the Yohkoh satellite in 1991. They are the means of transporting energy through the heliosphere and participate to the corona heating and the acceleration of solar wind. Several characteristics have been derived about their velocities, their rates of occurrence, and their relationship with CMEs. However, the initiation mechanism of jets, e.g. emerging flux, flux cancellation, or twist, is still debated. In the last decade coordinated observations of the Interface Region Imaging Spectrograph (IRIS) with the instruments on board the Solar Dynamic Observatory (SDO) allow to make a step forward for understanding the trigger of jets and the relationship between hot jets and cool surges. We observe at the same time the development of 2D and 3D MHD numerical simulations to interpret the results. This paper summarizes recent studies of jets showing the loci of magnetic reconnection in null points or in bald patch regions forming a current sheet. In the pre-jet phase a twist is frequently detected by the existence of a mini filament close to the dome of emerging flux. The twist can also be transferred to the jet from a flux rope in the vicinity of the reconnection by slippage of the polarities. Bidirectional flows are detected at the reconnection sites. We show the role of magnetic currents detected in the footprints of flux rope and quasi-separatrix layers for initiating the jets. We select a few studies and show that with the same observations, different interpretations are possible based on different approaches e.g. non linear force free field extrapolation or 3D MHD simulation. Title: Empirical atmosphere model in a mini flare during magnetic reconnection Authors: Schmieder, Brigitte; Joshi, Reetika; Chandra, Ramesh; Aulanier, Guillaume; Tei, Akiko; Heinzel, Petr; Tomin, James; Vilmer, Nicole; Bommier, Veronique Bibcode: 2021arXiv211206790S Altcode: A spatio-temporal analysis of IRIS spectra of MgII, CII, and SiIV ions allows us to study the dynamics and the stratification of the flare atmosphere along the line of sight during the magnetic reconnection phase at the jet base. Strong asymmetric MgII and CII line profiles with extended blue wings observed at the reconnection site are interpreted by the presence of two chromospheric temperature clouds: one explosive cloud with blueshifts at 290 km/s and one cloud with smaller Doppler shift (around 36 km/s). Simultaneously at the same location a mini flare was observed with strong emission in multi temperatures (AIA), in several spectral IRIS lines (e.g. Oiv and Siiv, Mgii), absorption of identified chromospheric lines in Siiv line profile, enhancement of the Balmer continuum and X-ray emission by FERMI/GBM. With the standard thick-target flare model we calculate the energy of non thermal electrons observed by FERMI and compare it to the energy radiated by the Balmer continuum emission. We show that the low energy input by non thermal electrons above 20 keV was still sufficient to produce the excess of Balmer continuum. Title: Filament Eruption Driving EUV Loop Contraction and Then Expansion above a Stable Filament Authors: Chandra, Ramesh; Démoulin, Pascal; Devi, Pooja; Joshi, Reetika; Schmieder, Brigitte Bibcode: 2021ApJ...922..227C Altcode: 2021arXiv210907821C We analyze the observations of EUV loop evolution associated with the filament eruption located at the border of an active region (AR). The event SOL2013-03-16T14:00 was observed with a large difference in view point by the Solar Dynamics Observatory and Solar Terrestrial Relations Observatory. The filament height is fitted with the sum of a linear and exponential function. These two phases point to different physical mechanisms such as tether-cutting reconnection and a magnetic instability. While no X-ray emission is reported, this event presents classical eruption features like separation of double ribbons and the growth of flare loops. We report the migration of the southern foot of the erupting filament flux rope due to the interchange reconnection with encountered magnetic loops of a neighboring AR. Parallel to the erupting filament, a stable filament remains in the core of the AR. The specificity of this eruption is that coronal loops, located above the nearly joining ends of the two filaments, first contract in phase, then expand and reach a new stable configuration close to the one present at the eruption onset. Both contraction and expansion phases last around 20 minutes. The main difference with previous cases is that the PIL bent about 180° around the end of the erupting filament because the magnetic configuration is at least tripolar. These observations are challenging for models that interpreted previous cases of loop contraction within a bipolar configuration. New simulations are required to broaden the complexity of the configurations studied. Title: Balmer continuum enhancement detected in a mini flare observed with IRIS Authors: Joshi, Reetika; Schmieder, Brigitte; Heinzel, Petr; Tomin, James; Chandra, Ramesh; Vilmer, Nicole Bibcode: 2021A&A...654A..31J Altcode: 2021arXiv210711651J Context. Optical and near-UV continuum emissions in flares contribute substantially to the flare energy budget. Two mechanisms play an important role for continuum emission in flares: hydrogen recombination after sudden ionization at chromospheric layers, and transportation of the energy radiatively from the chromosphere to lower layers in the atmosphere, the so-called back-warming.
Aims: The aim of the paper is to distinguish between these two mechanisms for the excess of the Balmer continuum observed in a flare.
Methods: We combined the observations of the Balmer continuum obtained with the Interface Region Imaging Spectrograph (IRIS) (spectra and slit-jaw images (SJIs) 2832 Å) and hard X-ray (HXR) emission detected by the Fermi/Gamma Burst Monitor (GBM) during a mini flare. The calibrated Balmer continuum was compared to non-local thermodynamic equilibrium (LTE) radiative transfer flare models, and the radiated energy was estimated. Assuming thick target HXR emission, we calculated the energy of the nonthermal electrons detected by the Fermi/GBM and compared it to the radiated energy.
Results: The favorable argument of a relation between the Balmer continuum excess and the HXR emission is that there is a good time coincidence between them. In addition, the shape of the maximum brightness in the 2832 SJIs, which is mainly due to this Balmer continuum excess, is similar to that of the Fermi/GBM light curve. The electron-beam flux estimated from Fermi/GBM between 109 and 1010 erg s−1 cm−2 is consistent with the beam flux required in non-LTE radiative transfer models to obtain the excess of Balmer continuum emission observed in this IRIS spectra.
Conclusions: The low-energy input by nonthermal electrons above 20 keV is sufficient to produce the enhancement in the Balmer continuum emission. This could be explained by the topology of the reconnection site. The reconnection starts in a tiny bald-patch region, which is transformed dynamically into an X-point current sheet. The size of the interacting region would be below the spatial resolution of the instrument. Title: Spectro-imagery of an active tornado-like prominence: Formation and evolution Authors: Barczynski, Krzysztof; Schmieder, Brigitte; Peat, Aaron W.; Labrosse, Nicolas; Mein, Pierre; Mein, Nicole Bibcode: 2021A&A...653A..94B Altcode: 2021arXiv210604259B Context. The dynamical nature of fine structures in prominences remains an open issue, including rotating flows in tornado prominences. While the Atmospheric Imaging Assembly imager aboard the Solar Dynamics Observatory allowed us to follow the global structure of a tornado-like prominence for five hours, the Interface Region Imaging Spectrograph, and the Multichannel Subtractive Double Pass spectrograph permitted to obtain plasma diagnostics of its fine structures.
Aims: We aim to address two questions. Firstly, is the observed plasma rotation conceptually acceptable in a flux rope magnetic support configuration with dips? Secondly, how is the plasma density distributed in the tornado-like prominence?
Methods: We calculated line-of-sight velocities and non-thermal line widths using Gaussian fitting for Mg II lines and the bisector method for Hα line. We determined the electron density from Mg II line integrated intensities and profile fitting methods using 1D non-LTE radiative transfer theory models.
Results: The global structure of the prominence observed in Hα, and Mg II h, and k line fits with a magnetic field structure configuration with dips. Coherent Doppler shifts in redshifted and blueshifted areas observed in both lines were detected along rapidly-changing vertical and horizontal structures. However, the tornado at the top of the prominence consists of multiple fine threads with opposite flows, suggesting counter-streaming flows rather than rotation. Surprisingly we found that the electron density at the top of the prominence could be larger (1011 cm−3) than in the inner part of the prominence.
Conclusions: We suggest that the tornado is in a formation state with cooling of hot plasma in a first phase, and following that, a phase of leakage of the formed blobs with large transverse flows of material along long loops extended away from the UV prominence top. The existence of such long magnetic field lines on both sides of the prominence would stop the tornado-like prominence from really turning around its axis.

Movies are available at https://www.aanda.org Title: Solar prominence diagnostics from non-LTE modelling of Mg II h&k line profiles Authors: Peat, A. W.; Labrosse, N.; Schmieder, B.; Barczynski, K. Bibcode: 2021A&A...653A...5P Altcode: 2021arXiv210610351P
Aims: We investigate a new method to for obtaining the plasma parameters of solar prominences observed in the Mg II h&k spectral lines by comparing line profiles from the IRIS satellite to a bank of profiles computed with a one-dimensional non-local thermodynamic equilibrium (non-LTE) radiative transfer code.
Methods: Using a grid of 1007 one-dimensional non-LTE radiative transfer models, some including a prominence-corona transition region (PCTR), we carry out this new method to match computed spectra to observed line profiles while accounting for line core shifts not present in the models. The prominence observations were carried out by the IRIS satellite on 19 April 2018.
Results: The prominence is very dynamic with many flows, including a large arm extending from the main body seen near the end of the observation. This flow is found to be redshifted, as is the prominence overall. The models are able to recover satisfactory matches in areas of the prominence where single line profiles are observed. We recover: mean temperatures of 6000-50 000 K; mean pressures of 0.01-0.5 dyne cm−2; column masses of 3.7 × 10−8-5 × 10−4 g cm−2; a mean electron density of 7.3 × 108-1.8 × 1011 cm−3; and an ionisation degree nHII/nHI = 0.03 − 4500. The highest values for the ionisation degree are found in areas where the line of sight crosses mostly plasma from the PCTR, correlating with high mean temperatures and correspondingly no Hα emission.
Conclusions: This new method naturally returns information on how closely the observed and computed profiles match, allowing the user to identify areas where no satisfactory match between models and observations can be obtained. The inclusion of the PCTR was found to be important when fitting models to data as regions where satisfactory fits were found were more likely to contain a model encompassing a PCTR. The line core shift can also be recovered from this new method, and it shows a good qualitative match with that of the line core shift found by the quantile method. This demonstrates the effectiveness of the approach to line core shifts in the new method.

Movies associated to Figs. 10 and A.1 are available at https://www.aanda.org Title: Fine Structures of an EUV Wave Event from Multi-viewpoint Observations Authors: Chandra, Ramesh; Chen, P. F.; Devi, Pooja; Joshi, Reetika; Schmieder, Brigitte; Moon, Yong-Jae; Uddin, Wahab Bibcode: 2021ApJ...919....9C Altcode: 2021arXiv210614024C In this study, we investigate an extreme ultraviolet (EUV) wave event on 2010 February 11, which occurred as a limb event from the Earth viewpoint and a disk event from the Solar Terrestrial Relations Observatory-Behind viewpoint. We use the data obtained by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory in various EUV channels. The EUV wave event was launched by a partial prominence eruption. Compared with some EUV wave events in previous works, this EUV wave event contains a faster wave with a speed of ~445 ± 6 km s-1, which we call a coronal Moreton wave, and a slower wave with a speed of ~298 ± 5 km s-1, which we call the Extreme Ultraviolet Imaging Telescope (EIT) wave. The coronal Moreton wave is identified as a fast-mode wave and the EIT wave is identified as an apparent propagation due to successive field-line stretching. We also observe a stationary front associated with the fast-mode EUV wave. This stationary front is explained as mode conversion from the coronal Moreton wave to a slow-mode wave near a streamer. Title: ICMEs and low plasma density in the solar wind observed at L1 Authors: Schmieder, Brigitte; Verbeke, Christine; Chané, Emmanuel; Démoulin, Pascal; Poedts, Stefaan; Grison, Benjamin Bibcode: 2021EGUGA..23.1799S Altcode: Different regimes of the solar wind have been observed at L1 during and after the passage of ICMEs, particularly anomalies with very low plasma density. From the observations at L1 (ACE) we identified different possible cases. A first case was explained by the evacuation of the plasma due over expansion of the ICME (May 2002). The second case on July 2002 is intriguing.In July 2002, three halo fast speed ICMEs, with their origin in the central part of the Sun, have surprisingly a poor impact on the magnetosphere (Dst > -28 nT). Analyzing the characteristics of the first ICME at L1, we conclude that the spacecraft crosses the ICME with a large impact (Bx component in GSE coordinates is dominant). The plasma density is low, just behind this first ICME. Next, we explore the generic conditions of low density formation in the EUHFORIA simulations.The very low density plasma after the sheath could be explained by the spacecraft crossing, on the side of the flux rope, while behind the front shock. We investigate two possible interpretations. The shock was able to compress and accelerate so much the plasma that a lower density is left behind. This can also be due to an effect of the sheath magnetic field which extends the flux rope effect on the sides of it, so a decrease of plasma density could occur like behind a moving object (here the sheath field). The following ICME, with also a low density, could be an intrinsic case with the formation in the corona of a cavity. Finally, we present some runs of EUHFORIA which fit approximately these data and argue in favor of the possible interpretations detailed above. Title: Over-expansion of a coronal mass ejection generates sub-Alfvénic plasma conditions in the solar wind at Earth Authors: Chané, E.; Schmieder, B.; Dasso, S.; Verbeke, C.; Grison, B.; Démoulin, P.; Poedts, S. Bibcode: 2021A&A...647A.149C Altcode: Context. From May 24-25, 2002, four spacecraft located in the solar wind at about 1 astronomical unit (au) measured plasma densities one to two orders of magnitude lower than usual. The density was so low that the flow became sub-Alfvénic for four hours, and the Alfvén Mach number was as low as 0.4. Consequently, the Earth lost its bow shock, and two long Alfvén wings were generated.
Aims: This is one of the lowest density events ever recorded in the solar wind at 1 au, and the least documented one. Our goal is to understand what caused the very low density.
Methods: Large Angle and Spectrometric Coronagraph (LASCO) and in situ data were used to identify whether something unusual occurred that could have generated such low densities
Results: The very low density was recorded inside a large interplanetary coronal mass ejection (ICME), which displayed a long, linearly declining velocity profile, typical of expanding ICMEs. We deduce a normalised radial expansion rate of 1.6. Such a strong expansion, occurring over a long period of time, implies a radial size expansion growing with the distance from the Sun to the power 1.6. This can explain a two-orders-of-magnitude drop in plasma density. Data from LASCO and the Advanced Composition Explorer show that this over-expanding ICME was travelling in the wake of a previous ICME.
Conclusions: The very low densities measured in the solar wind in May 2002 were caused by the over-expansion of a large ICME. This over-expansion was made possible because the ICME was travelling in a low-density and high-velocity environment present in the wake of another ICME coming from a nearby region on the Sun and ejected only three hours previously. Such conditions are very unusual, which explains why such very low densities are almost never observed. Title: Observations of a prominence eruption and loop contraction Authors: Devi, Pooja; Démoulin, Pascal; Chandra, Ramesh; Joshi, Reetika; Schmieder, Brigitte; Joshi, Bhuwan Bibcode: 2021A&A...647A..85D Altcode: 2021arXiv210107682D Context. Prominence eruptions provide key observations to understand the launch of coronal mass ejections as their cold plasma traces a part of the unstable magnetic configuration.
Aims: We select a well observed case to derive observational constraints for eruption models.
Methods: We analyze the prominence eruption and loop expansion and contraction observed on 02 March 2015 associated with a GOES M3.7 class flare (SOL2015-03-02T15:27) using the data from Atmospheric Imaging Assembly (AIA) and the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). We study the prominence eruption and the evolution of loops using the time-distance techniques.
Results: The source region is a decaying bipolar active region where magnetic flux cancellation is present for several days before the eruption. AIA observations locate the erupting prominence within a flux rope viewed along its local axis direction. We identify and quantify the motion of loops in contraction and expansion located on the side of the erupting flux rope. Finally, RHESSI hard X-ray observations identify the loop top and two foot-point sources.
Conclusions: Both AIA and RHESSI observations support the standard model of eruptive flares. The contraction occurs 19 min after the start of the prominence eruption indicating that this contraction is not associated with the eruption driver. Rather, this prominence eruption is compatible with an unstable flux rope where the contraction and expansion of the lateral loop is the consequence of a side vortex developing after the flux rope is launched.

Movies are available at https://www.aanda.org Title: Multi-thermal atmosphere of a mini-solar flare during magnetic reconnection observed with IRIS Authors: Joshi, Reetika; Schmieder, Brigitte; Tei, Akiko; Aulanier, Guillaume; Lörinčík, Juraj; Chandra, Ramesh; Heinzel, Petr Bibcode: 2021A&A...645A..80J Altcode: 2020arXiv201015401J Context. The Interface Region Imaging Spectrograph (IRIS) with its high spatial and temporal resolution facilitates exceptional plasma diagnostics of solar chromospheric and coronal activity during magnetic reconnection.
Aims: The aim of this work is to study the fine structure and dynamics of the plasma at a jet base forming a mini-flare between two emerging magnetic fluxes (EMFs) observed with IRIS and the Solar Dynamics Observatory instruments.
Methods: We proceed to a spatio-temporal analysis of IRIS spectra observed in the spectral ranges of Mg II, C II, and Si IV ions. Doppler velocities from Mg II lines were computed using a cloud model technique.
Results: Strong asymmetric Mg II and C II line profiles with extended blue wings observed at the reconnection site (jet base) are interpreted by the presence of two chromospheric temperature clouds: one explosive cloud with blueshifts at 290 km s-1 and one cloud with smaller Doppler shift (around 36 km s-1). Simultaneously at the same location (jet base), strong emission of several transition region lines (e.g. O IV and Si IV), emission of the Mg II triplet lines, and absorption of identified chromospheric lines in Si IV broad profiles have been observed and analysed.
Conclusions: Such observations of IRIS line and continuum emissions allow us to propose a stratification model for the white light, mini-flare atmosphere with multiple layers of different temperatures along the line of sight in a reconnection current sheet. It is the first time that we could quantify the fast speed (possibly Alfvénic flows) of cool clouds ejected perpendicularly to the jet direction via the cloud model technique. We conjecture that the ejected clouds come from plasma which was trapped between the two EMFs before reconnection or be caused by chromospheric-temperature (cool) upflow material similar to a surge during reconnection.

Movies are available at https://www.aanda.org Title: Spectral inversion of H-alpha and MgII lines in quiescent prominences Authors: Heinzel, Petr; Schmieder, Brigitte; Ruan, Guiping; Mein, Pierre; Gunár, Stanislav; Jejcic, Sonja; Mein, Nicole Bibcode: 2021cosp...43E1764H Altcode: Recent spectral analysis of simultaneous H-alpha (MSDP) and MgII lines (IRIS) (Guiping et al. 2019) has revealed certain bifurcation in resulting models. Two solutions were found from the line inversions using the non-LTE modeling: relatively high kinetic temperature and low non-thermal motions or temperatures mostly compatible with standard ones plus non-thermal motions of the order of 16 km/sec. Here we will present an improved spectral line inversion technique which clearly prefers the latter solution. Strong non-thermal motions are then interpreted as a mixture of microturbulence and the line-of-sight dynamics of prominence fine-structure threads. A detailed multithread modeling with the 2D non-LTE code and stochastic distributions of threads (position, dynamics) is now in progress and we will show our preliminary results. Title: Magnetic support of the solar filaments Authors: Schmieder, Brigitte; Aulanier, Guillaume; Gunár, Stanislav; Dudik, Jaroslav; Heinzel, Petr Bibcode: 2021cosp...43E1766S Altcode: The scale height in prominence is 500 km at maximum. However, non activated prominences can reach an altitude of 50000 km or more. Hanging filaments observed over the limb give the impression of quasi vertical structures. It was already the view in the past but reactivated by the movies of Hinode in Ca II line showing fuzzing vertical structures. In the corona it is not possible to measure the magnetic field supporting prominences. Only extrapolations of the photospheric magnetic field explain how cool plasma embedded in the dips of the magnetic field lines can be supported in the hot corona. I will review a few papers showing the distribution of the cool plasma dips and the observations of filaments on the disk visible in H$\alpha$ and in UV. A recent paper shows how a 3D extrapolation model and a radiative-transfer based H$\alpha$ visualization method leads to H$\alpha$ prominence fine structures. Finally, I will discuss the perspective effects on the perceived morphology of observed and modeled prominences. Title: Active tornado in a prominence observed in H-alpha with MSDP and Mg II with IRIS Authors: Barczynski, Krzysztof; Schmieder, Brigitte; Mein, Pierre; Labrosse, Nicolas; Mein, Nicole; Peat, Aaron Bibcode: 2021cosp...43E.973B Altcode: Large prominences with highly dynamic plasma features expand outwards in the solar atmosphere, often in loop or arch-shape or as a tornado. The origin of the rotating flow in prominence tornadoes is not fully understood yet. We aim to find an answer to two long-standing questions: what is the nature of the plasma flow and rotation in the prominence, and the role of the magnetic field configuration in the prominence dynamics? To this aim, we use observations from the Atmospheric Imaging Assembly (AIA) imager aboard the Solar Dynamics Observatory (SDO) to follow the plasma dynamics related to magnetic field. Simultaneous observations from the Interface Region Imaging Spectrograph (IRIS) and the Multi subtractive Double pass spectrograph (MSDP) allow us to study the plasma properties (intensity, Doppler velocity, non-thermal line broadening) of a tornado-like structure. We calculate line-of-sight velocities and non-thermal line width using Gaussian fitting for Mg II lines (IRIS) and a bisector method for H$\alpha$ line (MSDP). We determine the electron density and temperature from Mg II line integrated intensities using radiative transfer theory. We find that the red and blue Doppler-shifted areas present a coherent position in H$\alpha$ and Mg II h\&k lines along the fast-evolving prominence features. The EUV observations suggest long magnetic field lines on the sides of the prominence. The tornado-like at the top of the prominence consists of multiplefine threads with opposite flows, all of them being supported in dips of long magnetic field lines. From time to time, condensed blobs escape along these field lines. We conjecture that micro or macro turbulence exists at the top of the prominence and could form the small threads giving the impression of rotation. Title: Twist transfer to a solar jet from a big flux rope detected in the HMI magnetogram Authors: Joshi, Reetika; Schmieder, Brigitte; Aulanier, Guillaume; Chandra, Ramesh; Bommier, Veronique Bibcode: 2021cosp...43E1752J Altcode: Solar jets often have a helical structure containing both hot and cool ejected plasma. Different mechanisms are proposed to trigger jets by magnetic reconnection between the emergence of magnetic flux and environment, or induced by twisted photospheric motions bringing the system to instability. Multi-wavelength observations of a twisted jet observed with the AIA and IRIS is presented to understand how the twist was injected in the jet from a flux rope, fortunately, IRIS spectrographic slit was just crossing the reconnection site. This active region is a result of the collapse of two emerging magnetic fluxes (EMFs) overlaid by arch filament systems. In the magnetic field maps, we evidenced the pattern of a long sigmoidal flux rope along the polarity inversion line between the two EMFs which is the site of the reconnection. Before the jet, there was an extension of the flux rope, and a part of it was detached and formed a small bipole with a bald patch region which dynamically became an X-current sheet over the dome of one EMF where the reconnection took place. At the time of the reconnection, the Mg II spectra exhibited a strong extension of the blue wing which is decreasing over a distance of 10 Mm (from -300 km/s to a few km/s). This is the signature of the transfer of the twist to the jet. Comparison with numerical magnetohydrodynamics simulations confirmed the existence of the long flux rope in the neighborhood of the jet. We conjecture that there is a transfer of twist to the jet during the extension of the flux rope to the reconnection site without the flux rope eruption. The reconnection would start in the low atmosphere in the bald patch reconnection region and extend at an X-point along the current sheet formed above. Title: Initiation of CMEs and their geo-effectiveness Authors: Schmieder, Brigitte; Poedts, Stefaan; Grison, Benjamin; Demoulin, Pascal; Kim, Rok-Soon; Verbeke, Christine Bibcode: 2021cosp...43E1013S Altcode: Physical conditions of solar eruptions triggering coronal mass ejections (CMEs) have been determined by recent multi-wavelength observations as well by numerical simulations (e.g. OHM). CMEs and flares are the seeds of the Space Weather. Our analyze consists on a few case studies of CMEs which have all the good proxies for inducing geo-effectivity e.g. fast halo CME, central solar disk source. We follow the CMEs surfing in the solar wind as interplanetary coronal mass ejections (ICME) or magnetic clouds. We use numerical simulations (EUHFORIA) to investigate the geo-effectiveness of these ICMEs We study the degree of deviation of these halo CMEs from the Sun-Earth axis as well as their deformation and erosion due to their interaction with the ambient solar wind resulting in magnetic reconnections according to the input of parameters and their chance to hit other planets. The inhomogeneous nature of the solar wind and encounters are also important parameters influencing the impact of CMEs on planetary magnetospheres Title: Modeling Coronal Mass Ejections with EUHFORIA Authors: Verbeke, Christine; Schmieder, Brigitte; Rodriguez, Luciano; Poedts, Stefaan; Magdalenic, Jasmina; Pomoell, Jens; Temmer, Manuela; Asvestari, Eleanna; Scolini, Camilla; Heinemann, Stephan; Hinterreiter, Jürgen; Samara, Evangelia Bibcode: 2021cosp...43E2358V Altcode: Fully understanding the origin and evolution of Coronal Mass Ejections (CMEs) from the Sun to the Earth remains a major topic in current solar-terrestrial physics and is of key importance to improve our space weather prediction capabilities. CMEs can drive strong space weather disturbances at Earth, and their dynamical pressure, magnetic field configuration and interaction with the solar wind can significantly alter their arrival time and impact at Earth. One of the key parameters that determine the geo-effectiveness of the CME is its internal magnetic configuration. With the EUHFORIA inner-heliosphere magnetohydrodynamics model, we can model a magnetised CME using a Linear Force Free Spheromak (LFFS) model, in order to model the internal magnetic structure of the CME throughout the inner heliosphere. In this talk, we present an overview of the model assessment efforts that have been made with EUHFORIA over the past years. We discuss the validation of the solar wind, as well as the development of the LFFS model. We focus on determining the sensitivity of the LFFS model input parameters, as well as some case studies to show our improved modeling of the CME magnetic field structures at Earth. Finally, we discuss current limitations and future improvements of the EUHFORIA model. Title: Signature of the expansion of eruptive flux ropes measured by electric currents Authors: Schmieder, Brigitte; Aulanier, Guillaume; Janvier, Miho; Masson, Sophie; Barczynski, Krzysztof Bibcode: 2021cosp...43E1758S Altcode: MHD models demonstrate that hooks of flare ribbons are the footprints of eruptive flux ropes and that a decrease of the electric currents could be the signature of the evolution of the coronal magnetic field, e.g. the expansion of a line-tied flux rope with constant end-to-end external twist during the eruption. However in circuit models the surface electric current has a subsurface fixed source and therefore the currents should be constant . We analyze 19 X-class flares observed by Solar Dynamics Observatory (SDO) from 2011 to 2016, where flare ribbons with hooks are identifiable. For the first time fine measurements of time-evolution of electric currents inside the hooks in the observations as well as in the OHM 3D MHD simulation are performed. Our analysis shows a decrease of the electric current in the area surrounded by the ribbon hooks during and after the eruption. In the simulation the rate of current deceasing is similar to that of the field line elongation. So we interpret the decrease of the electric currents as due to the expansion of the flux rope in the corona during the eruption. Our analysis brings a new stone to the standard flare model in 3D. Title: Imaging Evidence for Solar Wind Outflows Originating from a Coronal Mass Ejection Footpoint Authors: Lörinčík, Juraj; Dudík, Jaroslav; Aulanier, Guillaume; Schmieder, Brigitte; Golub, Leon Bibcode: 2021ApJ...906...62L Altcode: 2020arXiv201004250L We report on Atmospheric Imaging Assembly observations of plasma outflows originating in a coronal dimming during a 2015 April 28 filament eruption. After the filament started to erupt, two flare ribbons formed, one of which had a well-visible hook enclosing a core (twin) dimming region. Along multiple funnels located in this dimming, a motion of plasma directed outward started to be visible in the 171 and 193 Å filter channels of the instrument. In time-distance diagrams, this motion generated a strip-like pattern, which lasted for more than 5 hr and whose characteristics did not change along the funnel. We therefore suggest the motion is a signature of outflows corresponding to velocities ranging between ≍70 and 140 km s-1. Interestingly, the pattern of the outflows and their velocities were found to be similar to those we observed in a neighboring ordinary coronal hole. Therefore, the outflows were most likely a signature of a coronal mass ejection-induced solar wind flowing along the open-field structures rooted in the dimming region. Further, the evolution of the hook encircling the dimming region was examined in the context of the latest predictions imposed for 3D magnetic reconnection. The observations indicate that the filament's footpoints were, during their transformation to the dimming region, reconnecting with surrounding canopies. To our knowledge, our observations present the first imaging evidence for outflows of plasma from a dimming region. Title: Links between prominence/filament magnetic field and plasma: What can 3D WPFS models teach us? Authors: Gunár, Stanislav; Schmieder, Brigitte; Aulanier, Guillaume; Heinzel, Petr; Mackay, Duncan; Dudik, Jaroslav Bibcode: 2021cosp...43E1769G Altcode: The magnetic field constitutes the skeleton and the driving force of prominences/filaments. It supports the dense prominence plasma against gravity and insulates it from the hot, coronal environment. The magnetic field is also responsible for the prominence stability, evolution and eruptions which affect the heliosphere and ultimately the Earth. However, a strong imbalance exists between the numerous efforts in detailed modelling of prominence magnetic field and its understanding from observations. That is due to the complex nature of the direct (and indirect) observations of solar magnetic fields which are challenging at the best of times and even more so in prominences or filaments. The direct observations of the prominence magnetic field require high-precision spectro-polarimetric measurements and realistic assumptions about the plasma structure which allow us to infer the field configuration from its effect on the polarized light emergent from the observed structures. The indirect observations rely on the perceived location, shape and dynamics of the prominence or filament plasma, often using moving small-scale plasma structures as tracers guided by the field lines. Both methods thus rely on the presence of observable plasma in the magnetic field configuration, and on the radiation which carries the information about the in-situ conditions to the observer. No prominence/filament magnetic field measurements are made without these two additional components, which are sometimes an afterthought in the magnetic field models. We have developed 3D Whole-Prominence Fine Structure (WPFS) models to illuminate the links between the prominence magnetic field, its plasma distributed among numerous fine structures and the radiation which carries the information about the prominence physical conditions to the observer. What can we learn from these 3D models? For example, we can see that a small change of the magnetic field configuration can have a large effect on the perceived structure of prominences and filaments visible in the H-alpha line. Consequently, this means that significant changes observed in prominences or filaments do not need to suggest that equally large changes in the underlying magnetic field configuration had to occur. In another example, we see that seemingly incomparable differences in the morphological look of prominences (long horizontal fine structures versus small blobs of plasma arranged into more-less vertical features) may not need to imply the existence of radically different magnetic field configurations. Rather, they might simply be manifestations of projection effects that can differ greatly depending on the viewing angle under which we observe the naturally three-dimensional prominences/filaments. Title: The role of small-scale surface motions in the transfer of twist to a solar jet from a remote stable flux rope Authors: Joshi, Reetika; Schmieder, Brigitte; Aulanier, Guillaume; Bommier, Véronique; Chandra, Ramesh Bibcode: 2020A&A...642A.169J Altcode: 2020arXiv200806887J Context. Jets often have a helical structure containing ejected plasma that is both hot and also cooler and denser than the corona. Various mechanisms have been proposed to explain how jets are triggered, primarily attributed to a magnetic reconnection between the emergence of magnetic flux and environment or that of twisted photospheric motions that bring the system into a state of instability.
Aims: Multi-wavelength observations of a twisted jet observed with the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics Observatory and the Interface Region Imaging Spectrograph (IRIS) were used to understand how the twist was injected into the jet, thanks to the IRIS spectrographic slit fortuitously crossing the reconnection site at that time.
Methods: We followed the magnetic history of the active region based on the analysis of the Helioseismic and Magnetic Imager vector magnetic field computed with the UNNOFIT code. The nature and dynamics of the jet reconnection site are characterised by the IRIS spectra.
Results: This region is the result of the collapse of two emerging magnetic fluxes (EMFs) overlaid by arch filament systems that have been well-observed with AIA, IRIS, and the New Vacuum Solar Telescope in Hα. In the magnetic field maps, we found evidence of the pattern of a long sigmoidal flux rope (FR) along the polarity inversion line between the two EMFs, which is the site of the reconnection. Before the jet, an extension of the FR was present and a part of it was detached and formed a small bipole with a bald patch (BP) region, which dynamically became an X-current sheet over the dome of one EMF where the reconnection took place. At the time of the reconnection, the Mg II spectra exhibited a strong extension of the blue wing that is decreasing over a distance of 10 Mm (from -300 km s-1 to a few km s-1). This is the signature of the transfer of the twist to the jet.
Conclusions: A comparison with numerical magnetohydrodynamics simulations confirms the existence of the long FR. We conjecture that there is a transfer of twist to the jet during the extension of the FR to the reconnection site without FR eruption. The reconnection would start in the low atmosphere in the BP reconnection region and extend at an X-point along the current sheet formed above.

Movies attached to Figs. 1, 3, 4, and 7 are available at https://www.aanda.org Title: Case study of multi-temperature coronal jets for emerging flux MHD models Authors: Joshi, Reetika; Chandra, Ramesh; Schmieder, Brigitte; Moreno-Insertis, Fernando; Aulanier, Guillaume; Nóbrega-Siverio, Daniel; Devi, Pooja Bibcode: 2020A&A...639A..22J Altcode: 2020arXiv200506064J Context. Hot coronal jets are a basic observed feature of the solar atmosphere whose physical origin is still actively debated.
Aims: We study six recurrent jets that occurred in active region NOAA 12644 on April 4, 2017. They are observed in all the hot filters of AIA as well as cool surges in IRIS slit-jaw high spatial and temporal resolution images.
Methods: The AIA filters allow us to study the temperature and the emission measure of the jets using the filter ratio method. We studied the pre-jet phases by analysing the intensity oscillations at the base of the jets with the wavelet technique.
Results: A fine co-alignment of the AIA and IRIS data shows that the jets are initiated at the top of a canopy-like double-chambered structure with cool emission on one and hot emission on the other side. The hot jets are collimated in the hot temperature filters, have high velocities (around 250 km s-1) and are accompanied by cool surges and ejected kernels that both move at about 45 km s-1. In the pre-phase of the jets, we find quasi-periodic intensity oscillations at their base that are in phase with small ejections; they have a period of between 2 and 6 min, and are reminiscent of acoustic or magnetohydrodynamic waves.
Conclusions: This series of jets and surges provides a good case study for testing the 2D and 3D magnetohydrodynamic emerging flux models. The double-chambered structure that is found in the observations corresponds to the regions with cold and hot loops that are in the models below the current sheet that contains the reconnection site. The cool surge with kernels is comparable with the cool ejection and plasmoids that naturally appears in the models.

Movies are available at https://www.aanda.org Title: Role of the Coronal Environment in the Formation of Four Shocks Observed without Coronal Mass Ejections at Earth's Lagrangian Point L1 Authors: Pick, M.; Magdalenić, J.; Cornilleau-Wehrlin, N.; Grison, B.; Schmieder, B.; Bocchialini, K. Bibcode: 2020ApJ...895..144P Altcode: The main goal of this study is to determine the solar origin of four single shocks observed at the Lagrange point L1 and followed by storm sudden commencements (SSCs) during 2002. We look for associated coronal mass ejections (CMEs), starting from estimates of the transit time from Sun to Earth. For each CME, we investigate its association with a radio type II burst, an indicator of the presence of a shock wave. For three of the events, the type II burst is shown to propagate along the same, or a similar, direction as the fastest segment of the CME leading edge. We analyze for each event the role of the coronal environment in the CME development, the shock formation, and their propagation, to finally identify its complex evolution. The ballistic velocity of these shocks during their propagation from the corona to L1 is compared to the shock velocity at L1. Based on a detailed analysis of the shock propagation and possible interactions up to 30 solar radii, we find a coherent velocity evolution for each event, in particular for one event, the 2002 April 14 SSC, for which a previous study did not find a satisfactory CME source. For the other three events, we observe the formation of a white-light shock overlying the different sources associated with those events. The localization of the event sources over the poles, together with an origin of the shocks being due to encounters of CMEs, can explain why at L1 we observe only single shocks and not interplanetary CMEs. Title: Quasi Periodic Oscillations in the Pre Phases of Recurrent Jets Highlighting Plasmoids in Current Sheet Authors: Joshi, Reetika; Chandra, Ramesh; Schmieder, Brigitte; Aulanier, Guillaume; Devi, Pooja; Moreno-Insertis, Fernando; Nóbrega-Siverio, Daniel Bibcode: 2020EGUGA..2222351J Altcode: Solar jets observed at the limb are important to determine the location of reconnection sites in the corona. In this study, we investigate six recurrent hot and cool jets occurring in the active region NOAA 12644 as it is crossing the west limb on April 04, 2017. These jets are observed in all the UV/EUV filters of SDO/AIA and in cooler temperature formation lines in IRIS slit jaw images. The jets are initiated at the top of a double chamber vault with cool loops on one side and hot loops on the other side. The existence of such double chamber vaults suggests the presence of emerging flux with cool loops, the hot loops being the reconnected loops similarly as in the models of Moreno-Insertiset al. 2008, 2013 and Nóbrega-Siverio et al. 2016. In the preliminary phase of the main jets, quasi periodic intensity oscillations accompanied by smaller jets are detected in the bright current sheet between the vault and the preexisting magnetic field. Individual kernels and plasmoids are ejected in open field lines along the jets. Plasmoids may launch torsional Alfven waves and the kernels would be the result of the untwist of the plasmoids in open magnetic field as proposed in the model of Wyper et al. 2016. Title: Can we explain the low geo-effectiveness of the fast halo CMEs in 2002 with EUHFORIA? Authors: Schmieder, Brigitte; Poedts, Stefaan; Verbeke, Christine Bibcode: 2020EGUGA..22.5543S Altcode: In 2002 (Cycle 23), a weak impact on the magnetosphere of the Earth has been reported for six halo CMEs related to six X-class flares and with velocities higher than 1000 km/s. The registered Dst minima are all between -17 nT and -50 nT. A study of the Sun-Earth chain of phenomena related to these CMEs reveals that four of them have a source at the limb and two have a source close to the solar disk center (Schmieder et al., 2020). All of CME magnetic clouds had a low z-component of the magnetic field, oscillating between positive and negative values.We performed a set of EUHFORIA simulations in an attempt to explain the low observed Dst and the observed magnetic fields. We study the degree of deviation of these halo CMEs from the Sun-Earth axis and as well as their deformation and erosion due to their interaction with the ambient solar wind (resulting in magnetic reconnections) according to the input of parameters and their chance to hit other planets. The inhomogeneous nature of the solar wind and encounters are also important parameters influencing the impact of CMEs on planetary magnetospheres. Title: Modelling and observations: Comparison of the magnetic field properties in a prominence Authors: Mackay, D. H.; Schmieder, B.; López Ariste, A.; Su, Y. Bibcode: 2020A&A...637A...3M Altcode: Context. Direct magnetic field measurements in solar prominences occur infrequently and are difficult to make and interpret. As a consequence, alternative methods are needed to derive the main properties of the magnetic field that supports the prominence mass. This is important for our understanding of solar prominences, but also for understanding how eruptive prominences may affect space weather.
Aims: We present the first direct comparison of the magnetic field strength derived from spectro-polarimetric observations of a solar prominence, with corresponding results from a theoretical flux rope model constructed from on-disc normal component magnetograms.
Methods: We first used spectro-polarimetric observations of a prominence obtained with the magnetograph THEMIS operating in the Canary Islands to derive the magnetic field of the observed prominence by inverting the Stokes parameters measured in the He D3 line. Next, we constructed two data-constrained non-linear force-free field (NLFFF) models of the same prominence. In one model we assumed a strongly twisted flux rope solution, and in the other a weakly twisted flux rope solution.
Results: The physical extent of the prominence at the limb (height and length) is best reproduced with the strongly twisted flux rope solution. The line-of-sight average of the magnetic field for the strongly twisted solution results in a magnetic field that has a magnitude of within a factor of 1-2 of the observed magnetic field strength. For the peak field strength along the line of sight, an agreement to within 20% of the observations is obtained for the strongly twisted solution. The weakly twisted solution produces significantly lower magnetic field strengths and gives a poor agreement with the observations.
Conclusions: The results of this first comparison are promising. We found that the flux rope insertion method of producing a NLFFF is able to deduce the overall properties of the magnetic field in an observed prominence. Title: Electric Current Evolution at the Footpoints of Solar Eruptions Authors: Barczynski, Krzysztof; Aulanier, Guillaume; Janvier, Miho; Schmieder, Brigitte; Masson, Sophie Bibcode: 2020ApJ...895...18B Altcode: 2020arXiv200407990B Electric currents play a critical role in the triggering of solar flares and their evolution. The aim of the present paper is to test whether the surface electric current has a surface or subsurface fixed source as predicted by the circuit approach of flare physics, or is the response of the surface magnetic field to the evolution of the coronal magnetic field as the MHD approach proposes? Out of all 19 X-class flares observed by SDO from 2011 to 2016 near the disk center, we analyzed the only nine eruptive flares for which clear ribbon hooks were identifiable. Flare ribbons with hooks are considered to be the footprints of eruptive flux ropes in MHD flare models. For the first time, fine measurements of the time evolution of electric currents inside the hooks in the observations as well as in the OHM 3D MHD simulation are performed. Our analysis shows a decrease of the electric current in the area surrounded by the ribbon hooks during and after the eruption. We interpret the decrease of the electric currents as due to the expansion of the flux rope in the corona during the eruption. Our analysis brings a new contribution to the standard flare model in 3D. Title: Low Geo-Effectiveness of Fast Halo CMEs Related to the 12 X-Class Flares in 2002 Authors: Schmieder, B.; Kim, R. -S.; Grison, B.; Bocchialini, K.; Kwon, R. -Y.; Poedts, S.; Démoulin, P. Bibcode: 2020JGRA..12527529S Altcode: 2020arXiv200310777S It is generally accepted that extreme space weather events tend to be related to strong flares and fast halo coronal mass ejections (CMEs). In the present paper, we carefully identify the chain of events from the Sun to the Earth induced by all 12 X-class flares that occurred in 2002. In this small sample, we find an unusual high rate (58%) of solar sources with a longitude larger than 74°. Yet all 12 X-class flares are associated with at least one CME. The fast halo CMEs (50%) are related to interplanetary CMEs (ICMEs) at L1 and weak Dst minimum values (more than -51 nT), while five (41%) of the 12 X-class flares are related to solar proton events (SPEs). We conclude that (i) all 12 analyzed solar events, even those associated with fast halo CMEs originating from the central disk region, and those ICMEs and SPEs were not very geo-effective. This unexpected result demonstrates that the suggested events in the chain (fast halo CME, X-class flares, central disk region, ICME, and SPE) are not infallible proxies for geo-effectiveness. (ii) The low value of integrated and normalized southward component of the interplanetary magnetic field (Bz*) may explain the low geo-effectiveness for this small sample. In fact, Bz* is well correlated to the weak Dst and low auroral electrojet activity. Hence, the only space weather impact at Earth in 2002 we can explain is based on Bz* at L1. Title: Observation of All Pre- and Post-reconnection Structures Involved in Three-dimensional Reconnection Geometries in Solar Eruptions Authors: Dudík, Jaroslav; Lörinčík, Juraj; Aulanier, Guillaume; Zemanová, Alena; Schmieder, Brigitte Bibcode: 2019ApJ...887...71D Altcode: 2019arXiv191008620D We report on observations of the two newly identified reconnection geometries involving erupting flux ropes. In 3D, a flux rope can reconnect either with a surrounding coronal arcade (recently named “ar-rf” reconnection) or with itself (“rr-rf” reconnection), and both kinds of reconnection create a new flux-rope field line and a flare loop. For the first time, we identify all four constituents of both reconnections in a solar eruptive event, the filament eruption of 2011 June 7 observed by Solar Dynamics Observatory/Atmospheric Imaging Assembly. The ar-rf reconnection manifests itself as shift of one leg of the filament by more than 25″ northward. At its previous location, a flare arcade is formed, while the new location of the filament leg previously corresponded to a footpoint of a coronal loop in 171 Å. In addition, the evolution of the flare ribbon hooks is also consistent with the occurrence of ar-rf reconnection as predicted by MHD simulations. Specifically, the growing hook sweeps footpoints of preeruptive coronal arcades, and these locations become inside the hook. Furthermore, the rr-rf reconnection occurs during the peak phase above the flare arcade, in an apparently X-type geometry involving a pair of converging bright filament strands in the erupting filament. A new flare loop forms near the leg of one of the strands, while a bright blob, representing a remnant of the same strand, is seen ascending into the erupting filament. All together, these observations vindicate recent predictions of the 3D standard solar-flare model. Title: Diagnostics of the Prominence Plasma from Hα and Mg II Spectral Observations Authors: Ruan, Guiping; Jejčič, Sonja; Schmieder, Brigitte; Mein, Pierre; Mein, Nicole; Heinzel, Petr; Gunár, Stanislav; Chen, Yao Bibcode: 2019ApJ...886..134R Altcode: The goal of this paper is to derive the physical conditions of the prominence observed on 2017 March 30. To do so, we use a unique set of data in Mg II lines obtained with the space-borne Interface Region Imaging Spectrograph (IRIS) and in Hα line with the ground-based Multi-Channel Subtractive Double Pass spectrograph operating at the Meudon solar tower. Here, we analyze the prominence spectra of Mg II h and k lines, and the Hα line in the part of the prominence which is visible in both sets of lines. We compute a grid of 1D NLTE (i.e., departures from the local thermodynamical equilibrium) models providing synthetic spectra of Mg II k and h, and Hα lines in a large space of model input parameters (temperature, density, pressure, and microturbulent velocity). We compare Mg II and Hα line profiles observed in 75 positions of the prominence with the synthetic profiles from the grid of models. These models allow us to compute the relationships between the integrated intensities and between the optical thickness in Hα and Mg II k lines. The optical thickness τ Hα is between 0.05 and 2, and {τ }Mg{{II}}{{k}}} is between 3 and 200. We show that the relationship of the observed integrated intensities agrees well with the synthetic integrated intensities for models with a higher microturbulence (16 km s-1) and T around 8000 K, ne = 1.5 × 1010 cm-3, p = 0.05 dyne. In this case, large microturbulence values could be a way to take into account the large mixed velocities existing in the observed prominence. Title: Bidirectional Reconnection Outflows in an Active Region Authors: Ruan, Guiping; Schmieder, Brigitte; Masson, Sophie; Mein, Pierre; Mein, Nicole; Aulanier, Guillaume; Chen, Yao Bibcode: 2019ApJ...883...52R Altcode: We report on bidirectional coronal reconnection outflows reaching ±200 km s-1 as observed in an active region with the Si IV and C II spectra of the Interface Region Imaging Spectrograph (IRIS). The evolution of the active region with an emerging flux, a failed filament eruption, and a jet is followed in Solar Dynamical Observatory (SDO)/Atmospheric Imaging Assembly (AIA) filters from 304 to 94 Å, IRIS slit jaw images, and SDO/Helioseismic and Magnetic Imager movies. The bidirectional outflow reconnection is located at a bright point visible in multiwavelength AIA filters above an arch filament system. This suggests that the reconnection occurs between rising loops above the emergence of magnetic bipoles and the longer, twisted magnetic field lines remnant of the failed filament eruption one hour before. The reconnection occurs continuously in the corona between quasi-parallel magnetic field lines, which is possible in a 3D configuration. The reconnection also triggers a jet with transverse velocities around 60 km s-1. Blueshifts and redshifts along its axis confirm the existence of a twist along the jet, which could have been transferred from the filament flux rope. The jet finally blows up the material of the filament before coming back during the second phase. In the Hα Dopplergrams provided by the MSDP spectrograph, we see more redshift than blueshift, indicating the return of the jet and filament plasma. Title: Vortex Formations and Its Associated Surges in a Sunspot Light Bridge Authors: Yang, Heesu; Lim, Eun-Kyung; Iijima, Haruhisa; Yurchyshyn, Vasyl; Cho, Kyung-Suk; Lee, Jeongwoo; Schmieder, Brigitte; Kim, Yeon-Han; Kim, Sujin; Bong, Su-Chan Bibcode: 2019ApJ...882..175Y Altcode: We report on the successive occurrence of 0.″5 wide photospheric vortices with strong transverse shear flows at the edge of a sunspot light bridge (LB), and the subsequent ejection of chromospheric surges observed using a Visible Inteferometry Spectrograph, a broadband TiO filter, and a Near InfRared Imaging Spectrograph of the Goode Solar Telescope operating at Big Bear Solar Observatory. The Hα surges ejected at the location of the vortices often appeared in a hollow cylindrical structure. We also observed quasi-periodic vortex-associated bright Hα plasma blobs moving upward with a speed of up to 4 km s-1. In view of the strong shear flow at the edge of the LB, it is likely that the vortices form under the Kelvin-Helmholtz instability. The surges may result from either the magnetic tension generated after magnetic reconnection or an acoustic impulse of a fast photospheric transverse flow. Otherwise, the surges could also be associated with Alfvénic waves, in which case their origin could be torsional magnetic fields generated in the process of the vortex formation. Title: Reminiscences Authors: Schmieder, Brigitte Bibcode: 2019SoPh..294...53S Altcode: 2019arXiv190304036S I would like to thank my Solar Physics colleagues for asking me to write this chapter on my professional life. My main interest has always been focused on the Sun, our star, from the heating of the corona, to the dynamics of prominences and their eruptions, flares and coronal mass ejections to their impact on the Earth. I built a new group in solar physics and gave to them my enthusiasm. They brought to me a lot of satisfaction. We have made important advances in solar physics with a step forward to understand the triggers of solar activity and their terrestrial effects. Our avant-garde research and discoveries have opened new topics for the solar community. Mixing observations obtained on the ground and in space with theory and numerical simulations brings about a new perspective in research. Title: Geoeffectiveness of the 12 X-class flares in 2002 Authors: Schmieder, Brigitte; Kim, Rocksoon; Grison, Benjamin; Bocchialini, Karine; Kwon, Young Bibcode: 2019EGUGA..21.1876S Altcode: We analyze systematically the chain of events related to the 12 X-ray flares of X class occurring in 2002: source region, CME, ICME, magnetic field at L1, geomagnetic indices, and SEP to determine if we could explain their weak geo-effectiveness by usual criteria. No intense geomagnetic storm is related to any of these flares. Only one of them is associated with a moderate storm. The three others are associated with a weak storm (-50 nT < min(Dst) < -30 nT). 75 % of the flares are associated with a halo CME with a good correlation rate for the speed/flux of the flare. The flare sources are mainly close to the limb (70%). We conclude that the association of big flares and strong geomagnetic disturbances may be valid only for extreme or intense geomagnetic storms. Otherwise the magnetic energy of active regions is released in an unexpected way into thermal energy and kinetic energy or in ejections of energetic particles. The most important parameter is the Bz value and its orientation. It seems that the CMEs launched with high speed (around 2000 km/s) avoid the Earth in our sample. The location of the solar source, the shape of the CME, and the shock front have a direct impact on the geo-effectiveness. Title: Erratum: Correction to: Statistical Analysis of Solar Events Associated with Storm Sudden Commencements over One Year of Solar Maximum During Cycle 23: Propagation from the Sun to the Earth and Effects Authors: Bocchialini, K.; Grison, B.; Menvielle, M.; Chambodut, A.; Cornilleau-Wehrlin, N.; Fontaine, D.; Marchaudon, A.; Pick, M.; Pitout, F.; Schmieder, B.; Régnier, S.; Zouganelis, I. Bibcode: 2019SoPh..294...38B Altcode: Correction to: Solar Phys (2018) 293:75https://doi.org/10.1007/s11207-018-1278-5

Please find in this correction document the correct versions of abstract, Sect. 3.1 and Figs. 3 and 12. Title: Exploration of long-period oscillations in an Hα prominence Authors: Zapiór, M.; Schmieder, B.; Mein, P.; Mein, N.; Labrosse, N.; Luna, M. Bibcode: 2019A&A...623A.144Z Altcode: 2019arXiv190300230Z Context. In previous work, we studied a prominence which appeared like a tornado in a movie made from 193 Å filtergrams obtained with the Atmospheric Imaging Assembly (AIA) imager aboard the Solar Dynamics Observatory (SDO). The observations in Hα obtained simultaneously during two consecutive sequences of one hour with the Multi-channel Subtractive Double Pass Spectrograph (MSDP) operating at the solar tower in Meudon showed that the cool plasma inside the tornado was not rotating around its vertical axis. Furthermore, the evolution of the Dopplershift pattern suggested the existence of oscillations of periods close to the time-span of each sequence.
Aims: The aim of the present work is to assemble the two sequences of Hα observations as a full data set lasting two hours to confirm the existence of oscillations, and determine their nature.
Methods: After having coaligned the Doppler maps of the two sequences, we use a Scargle periodogram analysis and cosine fitting to compute the periods and the phase of the oscillations in the full data set.
Results: Our analysis confirms the existence of oscillations with periods between 40 and 80 min. In the Dopplershift maps, we identify large areas with strong spectral power. In two of them, the oscillations of individual pixels are in phase. However, in the top area of the prominence, the phase is varying slowly, suggesting wave propagation.
Conclusions: We conclude that the prominence does not oscillate as a whole structure but exhibits different areas with their own oscillation periods and characteristics: standing or propagating waves. We discuss the nature of the standing oscillations and the propagating waves. These can be interpreted in terms of gravito-acoustic modes and magnetosonic waves, respectively.

Movie attached to Fig. 2 is available at https://www.aanda.org Title: Generalization of the Magnetic Field Configuration of Typical and Atypical Confined Flares Authors: Joshi, Navin Chandra; Zhu, Xiaoshuai; Schmieder, Brigitte; Aulanier, Guillaume; Janvier, Miho; Joshi, Bhuwan; Magara, Tetsuya; Chandra, Ramesh; Inoue, Satoshi Bibcode: 2019ApJ...871..165J Altcode: 2018arXiv181101228J Atypical flares cannot be naturally explained with standard models. To predict such flares, we need to define their physical characteristics, in particular, their magnetic environment, and identify pairs of reconnected loops. Here, we present in detail a case study of a confined flare preceded by flux cancellation that leads to the formation of a filament. The slow rise of the noneruptive filament favors the growth and reconnection of overlying loops. The flare is only of C5.0 class but it is a long duration event. The reason is that it is comprised of three successive stages of reconnection. A nonlinear force-free field extrapolation and a magnetic topology analysis allow us to identify the loops involved in the reconnection process and build a reliable scenario for this atypical confined flare. The main result is that a curved magnetic polarity inversion line in active regions is a key ingredient for producing such atypical flares. A comparison with previous extrapolations for typical and atypical confined flares leads us to propose a cartoon for generalizing the concept. Title: Solar Ultraviolet Bursts Authors: Young, Peter R.; Tian, Hui; Peter, Hardi; Rutten, Robert J.; Nelson, Chris J.; Huang, Zhenghua; Schmieder, Brigitte; Vissers, Gregal J. M.; Toriumi, Shin; Rouppe van der Voort, Luc H. M.; Madjarska, Maria S.; Danilovic, Sanja; Berlicki, Arkadiusz; Chitta, L. P.; Cheung, Mark C. M.; Madsen, Chad; Reardon, Kevin P.; Katsukawa, Yukio; Heinzel, Petr Bibcode: 2018SSRv..214..120Y Altcode: 2018arXiv180505850Y The term "ultraviolet (UV) burst" is introduced to describe small, intense, transient brightenings in ultraviolet images of solar active regions. We inventorize their properties and provide a definition based on image sequences in transition-region lines. Coronal signatures are rare, and most bursts are associated with small-scale, canceling opposite-polarity fields in the photosphere that occur in emerging flux regions, moving magnetic features in sunspot moats, and sunspot light bridges. We also compare UV bursts with similar transition-region phenomena found previously in solar ultraviolet spectrometry and with similar phenomena at optical wavelengths, in particular Ellerman bombs. Akin to the latter, UV bursts are probably small-scale magnetic reconnection events occurring in the low atmosphere, at photospheric and/or chromospheric heights. Their intense emission in lines with optically thin formation gives unique diagnostic opportunities for studying the physics of magnetic reconnection in the low solar atmosphere. This paper is a review report from an International Space Science Institute team that met in 2016-2017. Title: The nature of imploding loops during solar eruptions as revealed by MHD simulations and AIA observations Authors: Aulanier, Guillaume; Dudik, Jaroslav; Zucarello, F. P.; Demoulin, Pascal; Schmieder, Brigitte Bibcode: 2018csc..confE..19A Altcode: Over the last years AIA revealed the frequent occurence of contracting loops at the flanks of erupting active regions. Those have often been interpreted as an evidence of the implosion conjecture that relates magnetic energy decreases with volume contractions in the Sun's corona. So as to unveil the physical nature of these features we carried out observational analyses of two solar eruptions observed with AIA with different projection angles, which we coupled with new analyses of a generic zero-beta MHD simulation of an asymmetric eruption driven by the torus instability, that was not designed for this particular study. The simulation does display contracting loops in general. And the synthetic time-slices of the simulation, when rotated to the right projections, do match the observed ones. But in the simulation these inward motions are not due to any volume contraction. Instead they are associated with two large-scale quasi-incompressible coronal-vortices. Those develop at the flanks of the erupting flux ropes, as most of the compressive component of the flow is evacuated away by an Alfven wave in the early stages of the eruption. We argue that this behavior is merely a magnetic version of the usual pressure-driven formation of vortex rings in hydrodyanmics. This result implies that during a solar eruption, the free magnetic-energy from the pre-erupting active-region is converted not only in the flare and the CME, but is also "lost" in the generation of these two large-scale coronal vortices. Title: Importance of the Hα Visibility and Projection Effects for the Interpretation of Prominence Fine-structure Observations Authors: Gunár, Stanislav; Dudík, Jaroslav; Aulanier, Guillaume; Schmieder, Brigitte; Heinzel, Petr Bibcode: 2018ApJ...867..115G Altcode: We construct a new 3D Whole-prominence Fine-structure (WPFS) model based on a prominence magnetic field configuration designed to qualitatively approximate the morphology of a quiescent prominence observed on 2010 June 22. The model represents an entire prominence with its numerous fine structures formed by a prominence plasma located in dips in the prominence magnetic field. We use the constructed 3D model and employ a radiative-transfer-based Hα visualization method to analyze the Hα visibility of prominence fine structures and its effect on the perceived morphology of observed and modeled prominences. We qualitatively compare three techniques used for visualization of modeled prominences—visualizations drawing magnetic dips up to a height of 1 pressure scale height, drawing the full extent of magnetic dips, and the synthetic Hα visualization—and discuss their suitability for direct comparison between models and observations of prominences and filaments. We also discuss the role of visibility of the prominence fine structures in the estimation of the total height of prominences, which may indicate the height of pre-erupting flux ropes. This parameter is critical for the observational determination of the flux-rope stability. In addition, we employ the WPFS model to assess the effects caused by a projection of the naturally three-dimensional and heterogeneous prominences onto a two-dimensional plane of the sky. We discuss here how the morphological structures of prominences differ when observed in projections from different viewing angles. We also discuss the shapes of the dipped magnetic field lines and the perceived projection of motions of prominence fine structures along such field lines. Title: Extreme solar storms based on solar magnetic field Authors: Schmieder, Brigitte Bibcode: 2018JASTP.180...46S Altcode: 2017arXiv170801790S Many questions have to be answered before understanding the relationship between the emerging magnetic flux through the solar surface and the extreme geoeffective events. Which threshold determines the onset of the eruption? What is the upper limit in energy for a flare? Is the size of sunspot the only criteria to get extreme solar events?

Based on observations of previous solar cycles, and theory, the main ingredients for getting X ray class flares and large Interplanetary Corona Mass Ejections e.g. the built up of the electric current in the corona, are presented such as the existence of magnetic free energy, magnetic helicity, twist and stress in active regions. The upper limit of solar flare energy in space research era and the possible chances to get super-flares and extreme solar events can be predicted using MHD simulation of coronal mass ejections. Title: Horizontal photospheric flows trigger a filament eruption Authors: Roudier, T.; Schmieder, B.; Filippov, B.; Chandra, R.; Malherbe, J. M. Bibcode: 2018A&A...618A..43R Altcode: 2018arXiv180802272R Context. A large filament composed principally of two sections erupted sequentially in the southern hemisphere on January 26, 2016. The central, thick part of the northern section was first lifted up and lead to the eruption of the full filament. This event was observed in Hα with the Global Oscillation Network Group (GONG) and Christian Latouche IMageur Solaire (CLIMSO), and in ultraviolet (UV) with the Atmospheric Imaging Assembly (AIA) imager on board the Solar Dynamic Observatory (SDO).
Aims: The aim of the paper is to relate the photospheric motions below the filament and its environment to the eruption of the filament.
Methods: An analysis of the photospheric motions using Solar Dynamic Observatory Helioseismic and Magnetic Imager (SDO/HMI) continuum images with the new version of the coherent structure tracking (CST) algorithm developed to track granules, as well as large-scale photospheric flows, has been performed. Following velocity vectors, corks migrate towards converging areas.
Results: The supergranule pattern is clearly visible outside the filament channel but difficult to detect inside because the modulus of the vector velocity is reduced in the filament channel, mainly in the magnetized areas. The horizontal photospheric flows are strong on the west side of the filament channel and oriented towards the filament. The ends of the filament sections are found in areas of concentration of corks. Whirled flows are found locally around the feet.
Conclusions: The strong horizontal flows with an opposite direction to the differential rotation create strong shear and convergence along the magnetic polarity inversion line (PIL) in the filament channel. The filament has been destabilized by the converging flows, which initiate an ascent of the middle section of the filament until the filament reaches the critical height of the torus instability inducing, consequently, the eruption. The n decay index indicated an altitude of 60 Mm for the critical height. It is conjectured that the convergence along the PIL is due to the large-scale size cells of convection that transport the magnetic field to their borders.

The movies associated to Figs. 1, 2, 4 and 5 are available at https://www.aanda.org. Title: On the Dynamic Nature of a Quiescent Prominence Observed by IRIS and MSDP Spectrographs Authors: Ruan, Guiping; Schmieder, Brigitte; Mein, Pierre; Mein, Nicole; Labrosse, Nicolas; Gunár, Stanislav; Chen, Yao Bibcode: 2018ApJ...865..123R Altcode: Quiescent solar prominences are generally considered to have a stable large-scale structure. However, they consist of multiple small-scale structures that are often significantly dynamic. To understand the nature of prominence plasma dynamics we use the high spatial, temporal, and spectral resolution observations obtained by Interface Region Imaging Spectrograph (IRIS) during a coordinated campaign with the Multichannel Subtractive Double Pass spectrograph at the Meudon Solar Tower. Detailed analysis of the IRIS observations of Mg II lines, including the analysis of Dopplershift and line width obtained with two different methods (quantile method and Gaussian-fit method) are discussed in the frame of the dynamic nature of the structures. Large-scale coherent blueshift and redshift features are observed in Mg II lines and Hα exhibiting a slow evolution during 1:40 hr of observations. We explain the presence of several significantly asymmetric peaks in the observed Mg II line profiles by the presence of several prominence fine structures moving with different velocities located along the line of sight (LOS). In such a case, the decrease of the intensity of individual components of the observed spectra with the distance from the central wavelength can be explained by the Doppler dimming effect. We show that C II line profiles may be used to confirm the existence of multi-components along the LOS. Title: Observations of Two Successive EUV Waves and Their Mode Conversion Authors: Chandra, Ramesh; Chen, P. F.; Joshi, Reetika; Joshi, Bhuwan; Schmieder, Brigitte Bibcode: 2018ApJ...863..101C Altcode: 2018arXiv180611350C In this paper, we present the observations of two successive fast-mode extreme ultraviolet (EUV) wave events observed on 2016 July 23. Both fast-mode waves were observed by the Atmospheric Imaging Assembly instrument on board the Solar Dynamics Observatory satellite, with a traveling speed of ≈675 and 640 km s-1, respectively. These two wave events were associated with two filament eruptions and two GOES M-class solar flares from the NOAA active region 12565, which was located near the western limb. The EUV waves mainly move toward the south direction. We observed the interaction of the EUV waves with a helmet streamer further away to the south. When either or one of the EUV waves penetrates into the helmet streamer, a slowly propagating wave with a traveling speed of ≈150 km s-1 is observed along the streamer. We suggest that the slowly moving waves are slow-mode waves, and interpret this phenomenon as the magnetohydrodynamic wave-mode conversion from the fast mode to the slow mode. Furthermore, we observed several stationary fronts to the north and south of the source region. Title: Signature of flux ropes before and after eruptions: electric currents in active regions Authors: Schmieder, Brigitte; Aulanier, Guillaume; Dalmasse, Kévin; Janvier, Miho; Gilchrist, Stuart; Zhao, Jie; Dudik, Jaroslav Bibcode: 2018cosp...42E3026S Altcode: Solar observations, nonlinear force-free field extrapolations relying on these observations, and three-dimensional magnetohydrodynamic (MHD) models indicate the presence of electric currents in the pre-eruption state and in the course of eruptions of solar magnetic structures which are interpreted as flux ropes (sigmoids, filaments, cavities).The MHD models are able to explain the net currents in active regions by the existence of strong magnetic shear along the polarity inversion lines, thus confirming previous observations. The models have also captured the essence of the behavior of electric currents in active regions during solar eruptions, predicting current-density increases and decreases inside flare ribbons and in the interior of expanding flux ropes, respectively.The observed photospheric current-density maps, inferred from vector magnetic field observations, exhibit whirling ribbon patterns similar to the MHD model results, which are interpreted as the signatures of flux ropes and of quasi-separatrix layers (QSLs) between the magnetic systems in active regions. We will show how observations can confirm enhancement of the total current in these QSLs during the eruptions, and how these observations can be used to investigate whether current density decrease can be seen at the footpoints of erupting flux ropes Title: Dynamics in quiescent prominences observed by the IRIS and MSDP spectrographs Authors: Gunár, Stanislav; Schmieder, Brigitte; Ruan, Guiping; Mein, Pierre; Heinzel, Petr Bibcode: 2018cosp...42E1314G Altcode: Quiescent solar prominences are generally considered to be stable. However, these prominences consist of a multitude of small-scale structures or threads that are often significantly dynamic. To understand the nature of the plasma dynamics we use the high spatial, temporal and spectral resolution observations obtained by IRIS during coordinated campaign with the MSDP spectrograph at the Meudon Solar Tower. Mg II h and k lines observed by IRIS represent a good diagnostic tool for investigation of the prominence fine structure dynamics, as they are optically thick under the prominence conditions. We will present detailed IRIS observations of Mg II lines. We explain significant asymmetries in the observed Mg II spectra by the presence of several threads located along the line of sight with different velocities. In such a case, the decrease of the intensity of individual components of the observed spectra with the distance from the central wavelength can be explained by the Doppler dimming effect. To interpret the observed Mg II profiles in terms of dynamics we use 1D or 2D radiative transfer models including a prominence-corona transition region. We also show that the H-alpha line which is optically thinner than the Mg II doublet is an important constrain for the radiative transfer radiation modelling. Title: Prominence/Tornado plasma parameters Authors: Schmieder, Brigitte; Mein, Pierre; Zapior, Maciej; Labrosse, Nicolas; Lopez Ariste, Arturo Bibcode: 2018cosp...42E3025S Altcode: We present a comparison of the plasma physical parameters in prominences and tornadoes using IRIS data and ground based polarimetry measurements obtained with THEMIS. Mg II lines give a good diagnostics of the temperature and optical thickness of the structures. The Stokes parameters from the He D3 line allow to distinguish the behaviour of the magnetic field in typical prominences and atypical prominences (e.g. bubbles, eruptive prominence). We concentrate on the Dopplershifts in a tornado observed in transition region lines and in Halpha. Our results support the existence of oscillations in tornadoes but not rotation.A reconstruction of the 3D geometry of a helical prominence obtained by following the trajectory of kernels yields surprising results. The loops are shown to be quasi-horizontal structures with no curvature.We conclude that it is important to take into account the 3D structure of the prominence to study the dynamics of the prominence plasma. Title: Can 3D whole-prominence fine structure models be used for assessment of the prominence plasma mass and distribution prior to the onset of CMEs? Authors: Gunár, Stanislav; Schmieder, Brigitte; Aulanier, Guillaume; Anzer, Ulrich; Heinzel, Petr; Mackay, Duncan; Dudik, Jaroslav Bibcode: 2018cosp...42E1316G Altcode: Two complex 3D models of entire prominences including their numerous fine structures were recently developed. The first 3D Whole-Prominence Fine Structure (WPFS) model was developed by Gunár and Mackay. The second 3D WPFS model was put forward by Gunár, Aulanier, Dudík, Heinzel, and Schmieder. These 3D prominence models combine simulations of the 3D magnetic field configuration of an entire prominence with a detailed description of the prominence plasma. The plasma is located in magnetic dips in hydrostatic equilibrium and is distributed along hundreds of fine structures. The assumed prominence plasma has realistic density and temperature distributions including the prominence-corona transition region.These 3D WPFS models allow us to study the distribution and the mass of the prominence plasma contained in prominence magnetic field configurations. These can be crucial during the onset and early evolution of CMEs. Moreover, prominence plasma represents a bulk of the material ejected by CMEs into the interplanetary space. Here, we investigate the potential of using the 3D WPFS models for assessment of the role the prominence plasma plays in the initiation and evolution of CMEs. Title: Statistical Analysis of Solar Events Associated with Storm Sudden Commencements over One Year of Solar Maximum During Cycle 23: Propagation from the Sun to the Earth and Effects Authors: Bocchialini, K.; Grison, B.; Menvielle, M.; Chambodut, A.; Cornilleau-Wehrlin, N.; Fontaine, D.; Marchaudon, A.; Pick, M.; Pitout, F.; Schmieder, B.; Régnier, S.; Zouganelis, I. Bibcode: 2018SoPh..293...75B Altcode: 2018arXiv180307593B Taking the 32 storm sudden commencements (SSCs) listed by the International Service of Geomagnetic Indices (ISGI) of the Observatory de l'Ebre during 2002 (solar activity maximum in Cycle 23) as a starting point, we performed a multi-criterion analysis based on observations (propagation time, velocity comparisons, sense of the magnetic field rotation, radio waves) to associate them with solar sources, identified their effects in the interplanetary medium, and looked at the response of the terrestrial ionized and neutral environment. We find that 28 SSCs can be related to 44 coronal mass ejections (CMEs), 15 with a unique CME and 13 with a series of multiple CMEs, among which 19 (68%) involved halo CMEs. Twelve of the 19 fastest CMEs with speeds greater than 1000 km s−1 are halo CMEs. For the 44 CMEs, including 21 halo CMEs, the corresponding X-ray flare classes are: 3 X-class, 19 M-class, and 22 C-class flares. The probability for an SSC to occur is 75% if the CME is a halo CME. Among the 500, or even more, front-side, non-halo CMEs recorded in 2002, only 23 could be the source of an SSC, i.e. 5%. The complex interactions between two (or more) CMEs and the modification of their trajectories have been examined using joint white-light and multiple-wavelength radio observations. The detection of long-lasting type IV bursts observed at metric-hectometric wavelengths is a very useful criterion for the CME-SSC events association. The events associated with the most depressed Dst values are also associated with type IV radio bursts. The four SSCs associated with a single shock at L1 correspond to four radio events exhibiting characteristics different from type IV radio bursts. The solar-wind structures at L1 after the 32 SSCs are 12 magnetic clouds (MCs), 6 interplanetary coronal mass ejections (ICMEs) without an MC structure, 4 miscellaneous structures, which cannot unambiguously be classified as ICMEs, 5 corotating or stream interaction regions (CIRs/SIRs), one CIR caused two SSCs, and 4 shock events; note than one CIR caused two SSCs. The 11 MCs listed in 3 or more MC catalogs covering the year 2002 are associated with SSCs. For the three most intense geomagnetic storms (based on Dst minima) related to MCs, we note two sudden increases of the Dst, at the arrival of the sheath and the arrival of the MC itself. In terms of geoeffectiveness, the relation between the CME speed and the magnetic-storm intensity, as characterized using the Dst magnetic index, is very complex, but generally CMEs with velocities at the Sun larger than 1000 km s−1 have larger probabilities to trigger moderate or intense storms. The most geoeffective events are MCs, since 92% of them trigger moderate or intense storms, followed by ICMEs (33%). At best, CIRs/SIRs only cause weak storms. We show that these geoeffective events (ICMEs or MCs) trigger an increased and combined auroral kilometric radiation (AKR) and non-thermal continuum (NTC) wave activity in the magnetosphere, an enhanced convection in the ionosphere, and a stronger response in the thermosphere. However, this trend does not appear clearly in the coupling functions, which exhibit relatively weak correlations between the solar-wind energy input and the amplitude of various geomagnetic indices, whereas the role of the southward component of the solar-wind magnetic field is confirmed. Some saturation appears for Dst values <−100 nT on the integrated values of the polar and auroral indices. Title: Solar Active Region Electric Currents Before and During Eruptive Flares Authors: Schmieder, Brigitte; Aulanier, Guillaume Bibcode: 2018GMS...235..391S Altcode: 2019arXiv190304050S This chapter discusses electric currents in the preeruption state and in the course of eruptions of solar magnetic structures, using information from solar observations, nonlinear force-free field extrapolations relying on these observations, and three-dimensional magnetohydrodynamic (MHD) models. The discussion addresses the issue of neutralized versus nonneutralized currents in active regions and concludes that MHD models are able to explain nonneutralized currents in active regions by the existence of strong magnetic shear along the polarity inversion lines, thus confirming previous observations that already contained this result. The models have also captured the essence of the behavior of electric currents in active regions during solar eruptions, predicting current-density increases and decreases inside flare ribbons and in the interior of expanding flux ropes, respectively. The observed photospheric current-density maps, inferred from vector magnetic field observations, exhibit whirling ribbon patterns similar to the MHD model results, which are interpreted as the signatures of flux ropes and of quasi-separatrix layers (QSLs) between the magnetic systems in active regions. Enhancement of the total current in these QSLs during the eruptions and decreasing current densities at the footpoint of erupting flux ropes, has been confirmed in the observations. Title: Kinematic and magnetic coherent structures in solar and stellar turbulence Authors: Chian, Abraham C. -L.; Miranda, Rodrigo A.; Rempel, Erico L.; Schmieder, Brigitte Bibcode: 2018IAUS..340..285C Altcode: We show that on-off intermittency in solar and stellar cycles is a result of amplitude-phase synchronization in multiscale interactions in solar/stellar dynamos or magnetorotational instability which leads to the formation of kinematic and magnetic coherent structures, and the novel techniques of Lagrangian coherent structures can detect transport barriers and vortices such as magnetic flux tubes/ropes in solar and stellar turbulence with high accuracy. Title: Geoeffective events through solar cycles Authors: Schmieder, Brigitte; Aulanier, Guillaume Bibcode: 2018IAUS..340..255S Altcode: Extreme solar storms are well known in the historical databases. Since the modern era, it has been possible to associate clearly geomagnetic disturbances with solar events (flares, SEP, CMEs). In the recent solar cycles the geoeffective events (number and strength) are decreasing. As an example, in the 2002 maximum activity year, we present how many flares, and CMEs were geoeffective. Based on observations and simulations, we discuss on the size of sunspots and the field strength to get more energetic flares (> 1032 ergs) in the near future. Title: Large-amplitude Longitudinal Oscillations Triggered by the Merging of Two Solar Filaments: Observations and Magnetic Field Analysis Authors: Luna, M.; Su, Y.; Schmieder, B.; Chandra, R.; Kucera, T. A. Bibcode: 2017ApJ...850..143L Altcode: 2017arXiv171101038L We follow the eruption of two related intermediate filaments observed in Hα (from GONG) and EUV (from Solar Dynamics Observatory SDO/Atmospheric Imaging assembly AIA) and the resulting large-amplitude longitudinal oscillations of the plasma in the filament channels. The events occurred in and around the decayed active region AR12486 on 2016 January 26. Our detailed study of the oscillation reveals that the periods of the oscillations are about one hour. In Hα, the period decreases with time and exhibits strong damping. The analysis of 171 Å images shows that the oscillation has two phases: an initial long-period phase and a subsequent oscillation with a shorter period. In this wavelength, the damping appears weaker than in Hα. The velocity is the largest ever detected in a prominence oscillation, approximately 100 {km} {{{s}}}-1. Using SDO/HMI magnetograms, we reconstruct the magnetic field of the filaments, modeled as flux ropes by using a flux-rope insertion method. Applying seismological techniques, we determine that the radii of curvature of the field lines in which cool plasma is condensed are in the range 75-120 Mm, in agreement with the reconstructed field. In addition, we infer a field strength of ≥7 to 30 Gauss, depending on the electron density assumed, that is also in agreement with the values from the reconstruction (8-20 Gauss). The poloidal flux is zero and the axis flux is on the order of 1020 to 1021 Mx, confirming the high shear existing even in a non-active filament. Title: Statistical analysis of solar events associated with SSC over year of solar maximum during cycle 23: 2. Characterisation on the Sun-Earth path - Geoeffectiveness Authors: Cornilleau-Wehrlin, N.; Bocchialini, K.; Menvielle, M.; Fontaine, D.; Grison, B.; Marchaudon, A.; Pick, M.; Pitout, F.; Schmieder, B.; Regnier, S.; Zouganelis, Y.; Chambodut, A. Bibcode: 2017AGUFMSH31A2712C Altcode: Taking the 32 sudden storm commencements (SSC) listed by the observatory de l'Ebre / ISGI over the year 2002 (maximal solar activity) as a starting point, we performed a statistical analysis of the related solar sources, solar wind signatures, and terrestrial responses. For each event, we characterized and identified, as far as possible, (i) the sources on the Sun (Coronal Mass Ejections -CME-), with the help of a series of criteria (velocities, drag coefficient, radio waves, magnetic field polarity), as well as (ii) the structure and properties in the interplanetary medium, at L1, of the event associated to the SSC: magnetic clouds -MC-, non-MC interplanetary coronal mass ejections -ICME-, co-rotating/stream interaction regions -SIR/CIR-, shocks only and unclear events that we call "miscellaneous" events. The geoeffectiveness of the events, classified by category at L1, is analysed by their signatures in the Earth ionized (magnetosphere and ionosphere) and neutral (thermosphere) environments, using a broad set of in situ, remote and ground based instrumentation. The role of the presence of a unique or of a multiple source at the Sun, of its nature, halo or non halo CME, is also discussed. The set of observations is statistically analyzed so as to evaluate and compare the geoeffectiveness of the events. The results obtained for this set of geomagnetic storms started by SSCs is compared to the overall statistics of year 2002, relying on already published catalogues of events, allowing assessing the relevance of our approach ; for instance all the 12 well identified Magnetic Clouds of 2002 give rise to SSCs. Title: Statistical Analysis of Solar Events Associated with Storm Sudden Commencements over One Year of Solar Maximum during Cycle 23: Propagation and Effects from the Sun to the Earth. Authors: Bocchialini, K.; Grison, B.; Menvielle, M.; Chambodut, A.; Cornilleau-Wehrlin, N.; Fontaine, D.; Marchaudon, A.; Pick, M.; Pitout, F.; Schmieder, B.; Régnier, S.; Zouganelis, I. Bibcode: 2017sf2a.conf..181B Altcode: From the list of 32 SSCs over the year 2002, we performed a multi-criteria analysis based on propagation time, velocity comparison, sense of the magnetic field rotation, radio waves to associate them with solar sources, identify their causes in the interplanetary medium and then look at the response of the terrestrial ionized and neutral environment to them. The complex interactions between two (or more) CMEs and the modification in their trajectory have been examined using joint white light and multiple-wavelength radio observations. The structures at L_1 after the 32 SSCs are regarded as Magnetic Clouds (MCs), ICMEs without a MC structure, Miscellaneous structures, CIRs/SIRs, and shock-only events. In terms of geoeffectivity, generally CMEs with velocities at the Sun larger than 1000 km.s-1 have larger probabilities to trigger moderate or intense storms. The most geoeffective events are MCs, since 92% of them trigger moderate or intense storms. The geoeffective events trigger an increased and combined AKR and NTC wave activity in the magnetosphere, an enhanced convection in the ionosphere and a stronger response in the thermosphere. Title: Statistical Analysis of Solar Events Associated with SSC over Year of Solar Maximum during Cycle 23: 1. Identification of Related Sun-Earth Events Authors: Grison, B.; Bocchialini, K.; Menvielle, M.; Chambodut, A.; Cornilleau-Wehrlin, N.; Fontaine, D.; Marchaudon, A.; Pick, M.; Pitout, F.; Schmieder, B.; Regnier, S.; Zouganelis, Y. Bibcode: 2017AGUFMSH31A2711G Altcode: Taking the 32 sudden storm commencements (SSC) listed by the observatory de l'Ebre / ISGI over the year 2002 (maximal solar activity) as a starting point, we performed a statistical analysis of the related solar sources, solar wind signatures, and terrestrial responses. For each event, we characterized and identified, as far as possible, (i) the sources on the Sun (Coronal Mass Ejections -CME-), with the help of a series of herafter detailed criteria (velocities, drag coefficient, radio waves, polarity), as well as (ii) the structure and properties in the interplanetary medium, at L1, of the event associated to the SSC: magnetic clouds -MC-, non-MC interplanetary coronal mass ejections -ICME-, co-rotating/stream interaction regions -SIR/CIR-, shocks only and unclear events that we call "miscellaneous" events. The categorization of the events at L1 is made on published catalogues. For each potential CME/L1 event association we compare the velocity observed at L1 with the one observed at the Sun and the estimated balistic velocity. Observations of radio emissions (Type II, Type IV detected from the ground and /or by WIND) associated to the CMEs make the solar source more probable. We also compare the polarity of the magnetic clouds with the hemisphere of the solar source. The drag coefficient (estimated with the drag-based model) is calculated for each potential association and it is compared to the expected range values. We identified a solar source for 26 SSC related events. 12 of these 26 associations match all criteria. We finally discuss the difficulty to perform such associations. Title: Reconstruction of a helical prominence in 3D from IRIS spectra and images Authors: Schmieder, B.; Zapiór, M.; López Ariste, A.; Levens, P.; Labrosse, N.; Gravet, R. Bibcode: 2017A&A...606A..30S Altcode: 2017arXiv170608078S Context. Movies of prominences obtained by space instruments e.g. the Solar Optical Telescope (SOT) aboard the Hinode satellite and the Interface Region Imaging Spectrograph (IRIS) with high temporal and spatial resolution revealed the tremendous dynamical nature of prominences. Knots of plasma belonging to prominences appear to travel along both vertical and horizontal thread-like loops, with highly dynamical nature.
Aims: The aim of the paper is to reconstruct the 3D shape of a helical prominence observed over two and a half hours by IRIS.
Methods: From the IRIS Mg II k spectra we compute Doppler shifts of the plasma inside the prominence and from the slit-jaw images (SJI) we derive the transverse field in the plane of the sky. Finally we obtain the velocity vector field of the knots in 3D. Results.We reconstruct the real trajectories of nine knots travelling along ellipses.
Conclusions: The spiral-like structure of the prominence observed in the plane of the sky is mainly due to the projection effect of long arches of threads (up to 8 × 104 km). Knots run along more or less horizontal threads with velocities reaching 65 km s-1. The dominant driving force is the gas pressure.

Movies associated to Figs. 1, 9, 10, and 13 are available at http://www.aanda.org Title: Comparing UV/EUV line parameters and magnetic field in a quiescent prominence with tornadoes Authors: Levens, P. J.; Labrosse, N.; Schmieder, B.; López Ariste, A.; Fletcher, L. Bibcode: 2017A&A...607A..16L Altcode: 2017arXiv170804606L Context. Understanding the relationship between plasma and the magnetic field is important for describing and explaining the observed dynamics of solar prominences.
Aims: We determine if a close relationship can be found between plasma and magnetic field parameters, measured at high resolution in a well-observed prominence.
Methods: A prominence observed on 15 July 2014 by the Interface Region Imaging Spectrograph (IRIS), Hinode, the Solar Dynamics Observatory (SDO), and the Télescope Héliographique pour l'Étude du Magnétisme et des Instabilités Solaires (THEMIS) is selected. We perform a robust co-alignment of data sets using a 2D cross-correlation technique. Magnetic field parameters are derived from spectropolarimetric measurements of the He I D3 line from THEMIS. Line ratios and line-of-sight velocities from the Mg II h and k lines observed by IRIS are compared with magnetic field strength, inclination, and azimuth. Electron densities are calculated using Fe xii line ratios from the Hinode Extreme-ultraviolet Imaging Spectrometer, which are compared to THEMIS and IRIS data.
Results: We find Mg II k/h ratios of around 1.4 everywhere, similar to values found previously in prominences. Also, the magnetic field is strongest ( 30 G) and predominantly horizontal in the tornado-like legs of the prominence. The k3 Doppler shift is found to be between ±10 km s-1 everywhere. Electron densities at a temperature of 1.5 × 106 K are found to be around 109 cm-3. No significant correlations are found between the magnetic field parameters and any of the other plasma parameters inferred from spectroscopy, which may be explained by the large differences in the temperatures of the lines used in this study.
Conclusions: This is the first time that a detailed statistical study of plasma and magnetic field parameters has been performed at high spatial resolution in a prominence. Our results provide important constraints on future models of the plasma and magnetic field in these structures. Title: Slippage of Jets Explained by the Magnetic Topology of NOAA Active Region 12035 Authors: Joshi, R.; Schmieder, B.; Chandra, R.; Aulanier, G.; Zuccarello, F. P.; Uddin, W. Bibcode: 2017SoPh..292..152J Altcode: 2017arXiv170902791J We present the investigation of 11 recurring solar jets that originated from two different sites (site 1 and site 2) close to each other (≈11 Mm) in NOAA active region (AR) 12035 during 15 - 16 April 2014. The jets were observed by the Atmospheric Imaging Assembly (AIA) telescope on board the Solar Dynamics Observatory (SDO) satellite. Two jets were observed by the telescope of the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital, India, in Hα . On 15 April, flux emergence is strong in site 1, while on 16 April, flux emergence and cancellation mechanisms are involved in both sites. The jets of both sites have parallel trajectories and move to the south with a speed between 100 and 360 km s−1. The jets of site 2 occurred during the second day have a tendency to move toward the jets of site 1 and merge with them. We conjecture that the slippage of the jets could be explained by the complex topology of the region, which included a few low-altitude null points and many quasi-separatrix layers (QSLs), which could intersect with one another. Title: Prominence and tornado dynamics observed with IRIS and THEMIS Authors: Schmieder, Brigitte; Levens, Peter; Labrosse, Nicolas; Mein, Pierre; Lopez Ariste, Arturo; Zapior, Maciek Bibcode: 2017SPD....4820104S Altcode: Several prominences were observed during campaigns in September 2013 and July 2014 with the IRIS spectrometer and the vector magnetograph THEMIS (Tenerife). SDO/AIA and IRIS provided images and spectra of prominences and tornadoes corresponding to different physical conditions of the transition region between the cool plasma and the corona. The vector magnetic field was derived from THEMIS observations by using the He D3 depolarisation due to the magnetic field. The inversion code (PCA) takes into account the Hanle and Zeeman effects and allows us to compute the strength and the inclination of the magnetic field which is shown to be mostly horizontal in prominences as well as in tornadoes. Movies from SDO/AIA in 304 A and Hinode/SOT in Ca II show the highly dynamic nature of the fine structures. From spectra in Mg II and Si IV lines provided by IRIS and H-alpha observed by the Multi-channel Subtractive Double Pass (MSDP) spectrograph in the Meudon Solar Tower we derived the Doppler shifts of the fine structures and reconstructed the 3D structure of tornadoes. We conclude that the apparent rotation of AIA tornadoes is due to large-scale quasi-periodic oscillations of the plasma along more or less horizontal magnetic structures. Title: Expanding and Contracting Coronal Loops as Evidence of Vortex Flows Induced by Solar Eruptions Authors: Dudík, J.; Zuccarello, F. P.; Aulanier, G.; Schmieder, B.; Démoulin, P. Bibcode: 2017ApJ...844...54D Altcode: 2017arXiv170604783D Eruptive solar flares were predicted to generate large-scale vortex flows at both sides of the erupting magnetic flux rope. This process is analogous to a well-known hydrodynamic process creating vortex rings. The vortices lead to advection of closed coronal loops located at the peripheries of the flaring active region. Outward flows are expected in the upper part and returning flows in the lower part of the vortex. Here, we examine two eruptive solar flares, the X1.1-class flare SOL2012-03-05T03:20 and the C3.5-class SOL2013-06-19T07:29. In both flares, we find that the coronal loops observed by the Atmospheric Imaging Assembly in its 171 Å, 193 Å, or 211 Å passbands show coexistence of expanding and contracting motions, in accordance with the model prediction. In the X-class flare, multiple expanding and contracting loops coexist for more than 35 minutes, while in the C-class flare, an expanding loop in 193 Å appears to be close by and cotemporal with an apparently imploding loop arcade seen in 171 Å. Later, the 193 Å loop also switches to contraction. These observations are naturally explained by vortex flows present in a model of eruptive solar flares. Title: Two-Step Filament Eruption During 14 - 15 March 2015 Authors: Chandra, R.; Filippov, B.; Joshi, R.; Schmieder, B. Bibcode: 2017SoPh..292...81C Altcode: 2017arXiv170408860C We present here an interesting two-step filament eruption during 14 - 15 March 2015. The filament was located in NOAA AR 12297 and associated with a halo Coronal Mass Ejection (CME). We use observations from the Atmospheric Imaging Assembly (AIA) and Heliospheric Magnetic Imager (HMI) instruments onboard the Solar Dynamics Observatory (SDO), and from the Solar and Heliospheric Observatory (SOHO) Large Angle and Spectrometric Coronagraph (LASCO). We also use Hα data from the Global Oscillation Network Group (GONG) telescope and the Kanzelhoehe Solar Observatory. The filament shows a first step eruption on 14 March 2015 and it stops its rise at a projected altitude ≈125 Mm on the solar disk. It remains at this height for ≈12 hrs. Finally it erupts on 15 March 2015 and produces a halo CME. We also find jet activity in the active region during both days, which could help the filament de-stabilization and eruption. The decay index is calculated to understand this two-step eruption. The eruption could be due to the presence of successive instability-stability-instability zones as the filament is rising. Title: Transition from eruptive to confined flares in the same active region Authors: Zuccarello, F. P.; Chandra, R.; Schmieder, B.; Aulanier, G.; Joshi, R. Bibcode: 2017A&A...601A..26Z Altcode: 2017arXiv170202477Z Context. Solar flares are sudden and violent releases of magnetic energy in the solar atmosphere that can be divided into two classes: eruptive flares, where plasma is ejected from the solar atmosphere resulting in a coronal mass ejection (CME), and confined flares, where no CME is associated with the flare.
Aims: We present a case study showing the evolution of key topological structures, such as spines and fans, which may determine the eruptive versus non-eruptive behavior of the series of eruptive flares followed by confined flares, which all originate from the same site.
Methods: To study the connectivity of the different flux domains and their evolution, we compute a potential magnetic field model of the active region. Quasi-separatrix layers are retrieved from the magnetic field extrapolation.
Results: The change in behavior of the flares from one day to the next - from eruptive to confined - can be attributed to the change in orientation of the magnetic field below the fan with respect to the orientation of the overlaying spine rather than an overall change in the stability of the large-scale field.
Conclusions: Flares tend to be more confined when the field that supports the filament and the overlying field gradually becomes less anti-parallel as a direct result of changes in the photospheric flux distribution, being themselves driven by continuous shearing motions of the different magnetic flux concentrations.

Movies associated to Figs. 2, 3, and 5 are available at http://www.aanda.org Title: Solar filament eruptions and their physical role in triggering Coronal Mass Ejections Authors: Schmieder, Brigitte Bibcode: 2017EGUGA..19.2767S Altcode: Both filaments and CMEs have been related to twisted magnetic fields. Therefore, nearly all the MHD CME models include a twisted flux tube, called a flux rope. Either the flux rope is present before the eruption, or it is built up by reconnection of a sheared arcade from the beginning of the eruption. Combining observations of SDO and STEREO and CME theoretical models we have investigated different mechanisms initiating eruptions : new emergence of flux, shear motions, and dispersion of the external magnetic field, and/or reconnection of field lines below or above the flux rope. Their impacts is mainly to break the overlying magnetic tension and/or to favor the rise of the flux rope until the torus instability. We used the MHD simulation (OHM) as a tool to explain the different phases of eruptive flares: e.g. postflare loops. The prediction of enhancement of electric current during reconnection is confirmed in the observations. Title: Statistical analysis of solar events associated with SSC over one year of solar maximum during cycle 23: propagation and effects from the Sun to the Earth Authors: Cornilleau-Wehrlin, Nicole; Bocchialini, Karine; Menvielle, Michel; Chambodut, Aude; Fontaine, Dominique; Grison, Benjamin; Marchaudon, Aurélie; Pick, Monique; Pitout, Frédéric; Schmieder, Brigitte; Régnier, Stéphane; Zouganelis, Yannis Bibcode: 2017EGUGA..19.3689C Altcode: Taking the 32 sudden storm commencements (SSC) listed by the observatory de l'Ebre / ISGI over the year 2002 (maximal solar activity) as a starting point, we performed a statistical analysis of the related solar sources, solar wind signatures, and terrestrial responses. For each event, we characterized and identified, as far as possible, (i) the sources on the Sun (Coronal Mass Ejections -CME-), with the help of a series of criteria (velocities, drag coefficient, radio waves, helicity), as well as (ii) the structure and properties in the interplanetary medium, at L1, of the event associated to the SSC: magnetic clouds -MC-, non-MC interplanetary coronal mass ejections -ICME-, co-rotating/stream interaction regions -SIR/CIR-, shocks only and unclear events that we call "miscellaneous" events. The observed Sun-to-Earth travel times are compared to those estimated using existing simple models of propagation in the interplanetary medium. This comparison is used to statistically assess performances of various models. The geoeffectiveness of the events, classified by category at L1, is analysed by their signatures in the Earth ionized (magnetosphere and ionosphere) and neutral (thermosphere) environments, using a broad set of in situ, remote and ground based instrumentation. The role of the presence of a unique or of a multiple source at the Sun, of its nature, halo or non halo CME, is also discussed. The set of observations is statistically analyzed so as to evaluate and compare the geoeffectiveness of the events. The results obtained for this set of geomagnetic storms started by SSCs is compared to the overall statistics of year 2002, relying on already published catalogues of events, allowing assessing the relevance of our approach (for instance the all 12 well identified Magnetic Clouds of 2002 give rise to SSCs). Title: Vortex and Sink Flows in Eruptive Flares as a Model for Coronal Implosions Authors: Zuccarello, F. P.; Aulanier, G.; Dudík, J.; Démoulin, P.; Schmieder, B.; Gilchrist, S. A. Bibcode: 2017ApJ...837..115Z Altcode: 2017arXiv170200199Z Eruptive flares are sudden releases of magnetic energy that involve many phenomena, several of which can be explained by the standard 2D flare model and its realizations in 3D. We analyze a 3D magnetohydrodynamics simulation, in the framework of this model, that naturally explains the contraction of coronal loops in the proximity of the flare sites, as well as the inflow toward the region above the cusp-shaped loops. We find that two vorticity arcs located along the flanks of the erupting magnetic flux rope are generated as soon as the eruption begins. The magnetic arcades above the flux rope legs are then subjected to expansion, rotation, or contraction depending on which part of the vortex flow advects them. In addition to the vortices, an inward-directed magnetic pressure gradient exists in the current sheet below the magnetic flux rope. It results in the formation of a sink that is maintained by reconnection. We conclude that coronal loop apparent implosions observed during eruptive flares are the result of hydromagnetic effects related to the generation of vortex and sink flows when a flux rope moves in a magnetized environment. Title: Blowout jets and impulsive eruptive flares in a bald-patch topology Authors: Chandra, R.; Mandrini, C. H.; Schmieder, B.; Joshi, B.; Cristiani, G. D.; Cremades, H.; Pariat, E.; Nuevo, F. A.; Srivastava, A. K.; Uddin, W. Bibcode: 2017A&A...598A..41C Altcode: 2016arXiv161001918C Context. A subclass of broad extreme ultraviolet (EUV) and X-ray jets, called blowout jets, have become a topic of research since they could be the link between standard collimated jets and coronal mass ejections (CMEs).
Aims: Our aim is to understand the origin of a series of broad jets, some of which are accompanied by flares and associated with narrow and jet-like CMEs.
Methods: We analyze observations of a series of recurrent broad jets observed in AR 10484 on 21-24 October 2003. In particular, one of them occurred simultaneously with an M2.4 flare on 23 October at 02:41 UT (SOLA2003-10-23). Both events were observed by the ARIES Hα Solar Tower-Telescope, TRACE, SOHO, and RHESSI instruments. The flare was very impulsive and followed by a narrow CME. A local force-free model of AR 10484 is the basis to compute its topology. We find bald patches (BPs) at the flare site. This BP topology is present for at least two days before to events. Large-scale field lines, associated with the BPs, represent open loops. This is confirmed by a global potential free source surface (PFSS) model. Following the brightest leading edge of the Hα and EUV jet emission, we can temporarily associate these emissions with a narrow CME.
Results: Considering their characteristics, the observed broad jets appear to be of the blowout class. As the most plausible scenario, we propose that magnetic reconnection could occur at the BP separatrices forced by the destabilization of a continuously reformed flux rope underlying them. The reconnection process could bring the cool flux-rope material into the reconnected open field lines driving the series of recurrent blowout jets and accompanying CMEs.
Conclusions: Based on a model of the coronal field, we compute the AR 10484 topology at the location where flaring and blowout jets occurred from 21 to 24 October 2003. This topology can consistently explain the origin of these events.

The movie associated to Fig. 1 is available at http://www.aanda.org Title: Observational Evidence of Magnetic Reconnection for Brightenings and Transition Region Arcades in IRIS Observations Authors: Zhao, Jie; Schmieder, Brigitte; Li, Hui; Pariat, Etienne; Zhu, Xiaoshuai; Feng, Li; Grubecka, Michalina Bibcode: 2017ApJ...836...52Z Altcode: 2017arXiv170108356Z By using a new method of forced-field extrapolation, we study the emerging flux region AR11850 observed by the Interface Region Imaging Spectrograph and Solar Dynamical Observatory. Our results suggest that the bright points (BPs) in this emerging region exhibit responses in lines formed from the upper photosphere to the transition region, which have relatively similar morphologies. They have an oscillation of several minutes according to the Atmospheric Imaging Assembly data at 1600 and 1700 Å. The ratio between the BP intensities measured in 1600 and 1700 Å filtergrams reveals that these BPs are heated differently. Our analysis of the Helioseismic and Magnetic Imager vector magnetic field and the corresponding topology in AR11850 indicates that the BPs are located at the polarity inversion line and most of them are related to magnetic reconnection or cancelation. The heating of the BPs might be different due to different magnetic topology. We find that the heating due to the magnetic cancelation would be stronger than the case of bald patch reconnection. The plasma density rather than the magnetic field strength could play a dominant role in this process. Based on physical conditions in the lower atmosphere, our forced-field extrapolation shows consistent results between the bright arcades visible in slit-jaw image 1400 Å and the extrapolated field lines that pass through the bald patches. It provides reliable observational evidence for testing the mechanism of magnetic reconnection for the BPs and arcades in the emerging flux region, as proposed in simulation studies. Title: Successive Magnetic Reconnections Observed during Sympathetic Eruptions Authors: Chandra Joshi, Navin; Schmieder, Brigitte; Magara, Tetsuya; Guo, Yang; Aulanier, Guillaume Bibcode: 2017psio.confE.120C Altcode: No abstract at ADS Title: Hα Doppler shifts in a tornado in the solar corona Authors: Schmieder, B.; Mein, P.; Mein, N.; Levens, P. J.; Labrosse, N.; Ofman, L. Bibcode: 2017A&A...597A.109S Altcode: 2016arXiv161202232S Context. High resolution movies in 193 Å from the Atmospheric Imaging Assembly (AIA) on the Solar Dynamic Observatory (SDO) show apparent rotation in the leg of a prominence observed during a coordinated campaign. Such structures are commonly referred to as tornadoes. Time-distance intensity diagrams of the AIA data show the existence of oscillations suggesting that the structure is rotating.
Aims: The aim of this paper is to understand if the cool plasma at chromospheric temperatures inside the tornado is rotating around its central axis.
Methods: The tornado was also observed in Hα with a cadence of 30 s by the MSDP spectrograph, operating at the Solar Tower in Meudon. The MSDP provides sequences of simultaneous spectra in a 2D field of view from which a cube of Doppler velocity maps is retrieved.
Results: The Hα Doppler maps show a pattern with alternatively blueshifted and redshifted areas of 5 to 10'' wide. Over time the blueshifted areas become redshifted and vice versa, with a quasi-periodicity of 40 to 60 min. Weaker amplitude oscillations with periods of 4 to 6 min are superimposed onto these large period oscillations.
Conclusions: The Doppler pattern observed in Hα cannot be interpreted as rotation of the cool plasma inside the tornado. The Hα velocity observations give strong constraints on the possible interpretations of the AIA tornado. Title: Heating Mechanisms in the Low Solar Atmosphere through Magnetic Reconnection in Current Sheets Authors: Ni, Lei; Lin, Jun; Roussev, Ilia I.; Schmieder, Brigitte Bibcode: 2016ApJ...832..195N Altcode: 2016arXiv161101746N We simulate several magnetic reconnection processes in the low solar chromosphere/photosphere; the radiation cooling, heat conduction and ambipolar diffusion are all included. Our numerical results indicate that both the high temperature (≳8 × 104 K) and low temperature (∼104 K) magnetic reconnection events can happen in the low solar atmosphere (100-600 km above the solar surface). The plasma β controlled by plasma density and magnetic fields is one important factor to decide how much the plasma can be heated up. The low temperature event is formed in a high β magnetic reconnection process, Joule heating is the main mechanism to heat plasma and the maximum temperature increase is only several thousand Kelvin. The high temperature explosions can be generated in a low β magnetic reconnection process, slow and fast-mode shocks attached at the edges of the well developed plasmoids are the main physical mechanisms to heat the plasma from several thousand Kelvin to over 8 × 104 K. Gravity in the low chromosphere can strongly hinder the plasmoid instability and the formation of slow-mode shocks in a vertical current sheet. Only small secondary islands are formed; these islands, however, are not as well developed as those in the horizontal current sheets. This work can be applied to understand the heating mechanism in the low solar atmosphere and could possibly be extended to explain the formation of common low temperature Ellerman bombs (∼104 K) and the high temperature Interface Region Imaging Spectrograph (IRIS) bombs (≳8 × 104) in the future. Title: Height formation of bright points observed by IRIS in Mg II line wings during flux emergence Authors: Grubecka, M.; Schmieder, B.; Berlicki, A.; Heinzel, P.; Dalmasse, K.; Mein, P. Bibcode: 2016A&A...593A..32G Altcode: Context. A flux emergence in the active region AR 111850 was observed on September 24, 2013 with the Interface Region Imaging Spectrograph (IRIS). Many bright points are associated with the new emerging flux and show enhancement brightening in the UV spectra.
Aims: The aim of this work is to compute the altitude formation of the compact bright points (CBs) observed in Mg II lines in the context of searching Ellerman bombs (EBs).
Methods: IRIS provided two large dense rasters of spectra in Mg II h and k lines, Mg II triplet, C II and Si IV lines covering all the active region and slit jaws in the two bandpasses (1400 Å and 2796 Å) starting at 11:44 UT and 15:39 UT, and lasting 20 min each. Synthetic profiles of Mg II and Hα lines are computed with non-local thermodynamic equlibrium (NLTE) radiative transfer treatment in 1D solar atmosphere model including a hotspot region defined by three parameters: temperature, altitude, and width.
Results: Within the two IRIS rasters, 74 CBs are detected in the far wings of the Mg II lines (at +/-1 Å and 3.5 Å). Around 10% of CBs have a signature in Si IV and CII. NLTE models with a hotspot located in the low atmosphere were found to fit a sample of Mg II profiles in CBs. The Hα profiles computed with these Mg II CB models are consistent with typical EB profiles observed from ground based telescopes e.g. THEMIS. A 2D NLTE modelling of fibrils (canopy) demonstrates that the Mg II line centres can be significantly affected but not the peaks and the wings of Mg II lines.
Conclusions: We conclude that the bright points observed in Mg II lines can be formed in an extended domain of altitudes in the photosphere and/or the chromosphere (400 to 750 km). Our results are consistent with the theory of heating by Joule dissipation in the atmosphere produced by magnetic field reconnection during flux emergence. Title: Magnetic Field in Atypical Prominence Structures: Bubble, Tornado, and Eruption Authors: Levens, P. J.; Schmieder, B.; López Ariste, A.; Labrosse, N.; Dalmasse, K.; Gelly, B. Bibcode: 2016ApJ...826..164L Altcode: 2016arXiv160505964L Spectropolarimetric observations of prominences have been obtained with the THEMIS telescope during four years of coordinated campaigns. Our aim is now to understand the conditions of the cool plasma and magnetism in “atypical” prominences, namely when the measured inclination of the magnetic field departs, to some extent, from the predominantly horizontal field found in “typical” prominences. What is the role of the magnetic field in these prominence types? Are plasma dynamics more important in these cases than the magnetic support? We focus our study on three types of “atypical” prominences (tornadoes, bubbles, and jet-like prominence eruptions) that have all been observed by THEMIS in the He I D3 line, from which the Stokes parameters can be derived. The magnetic field strength, inclination, and azimuth in each pixel are obtained by using the inversion method of principal component analysis on a model of single scattering in the presence of the Hanle effect. The magnetic field in tornadoes is found to be more or less horizontal, whereas for the eruptive prominence it is mostly vertical. We estimate a tendency toward higher values of magnetic field strength inside the bubbles than outside in the surrounding prominence. In all of the models in our database, only one magnetic field orientation is considered for each pixel. While sufficient for most of the main prominence body, this assumption appears to be oversimplified in atypical prominence structures. We should consider these observations as the result of superposition of multiple magnetic fields, possibly even with a turbulent field component. Title: Evidence of flux rope and sigmoid in Active Regions prior eruptions Authors: Schmieder, Brigitte; Aulanier, Guillaume; Janvier, Miho; Bommier, Veronique; Dudik, Jaroslav; Gilchrist, Stuart; Zhao, Jie Bibcode: 2016cosp...41E1750S Altcode: In the solar corona, the magnetic field is dominant, and the current density vector is nearly aligned with the magnetic field lines for strong and stressed field regions. Stressed and highly twisted flux ropes are at the origin of eruptive events such as flares and coronal mass ejections, which inject material into the interplanetary medium. The standard three dimensional (3D) flare model predicts the complex evolution of flare loops and the flux rope before the eruption. Flux ropes are not directly observed in the corona, however it has started to be possible to detect their footprints in the photosphere. Recent high spatial and temporal resolution spectro-polarimeters have allowed us to compute the photospheric electric currents and follow their evolution. Characteristics pattern like J-shaped ribbons indicate the presence of a flux rope before the flare. The results confirm the predictions of the 3D MHD standard model of eruptive flares. It is interesting to compare the magnetic helicity of the ejected flux rope with the in situ measurements of the corresponding ICME at L1. We will show some examples (February 15 2011, July 12 2012, Sept 10 2014). Title: Erratum: "Hooked Flare Ribbons and Flux-rope Related QSL Footprints"(2016, ApJ, 823, 62) Authors: Zhao, Jie; Gilchrist, Stuart A.; Aulanier, Guillaume; Schmieder, Brigitte; Pariat, Etienne; Li, Hui Bibcode: 2016ApJ...825...80Z Altcode: No abstract at ADS Title: Statistical analysis of CMEs' geoeffectiveness over one year of solar maximum during cycle 23 Authors: Schmieder, Brigitte; Bocchialini, Karine; Menvielle, Michel Bibcode: 2016cosp...41E1751S Altcode: Using different propagation models from the Sun to the Earth, we performed a statistical analysis over the year 2002 on CME's geoeffectiveness linked to sudden storm commencements (ssc). We also classified the perturbations of the interplanetary medium that trigger the sscs. For each CME, the sources on the Sun of the CME are identified as well as the properties of the parameters deduced from spacecraft measurements along the path of the CME related event, in the solar atmosphere, the interplanetary medium, and the Earth ionized (magnetosphere and ionosphere) and neutral (thermosphere) environments. The set of observations is statistically analysed so as to evaluate the geoeffectiveness of CMEs in terms of ionospheric and thermospheric signatures, with attention to possible differences related to different kinds of solar sources. The observed Sun-to-Earth travel times are compared to those estimated using the existing models of propagation in the interplanetary medium, and this comparison is used to statistically assess the performances of the various models. Title: Prominence plasma and magnetic field structure - A coordinated observation with IRIS, Hinode and THEMIS Authors: Schmieder, Brigitte; Labrosse, Nicolas; Levens, Peter; Lopez Ariste, Arturo Bibcode: 2016cosp...41E1749S Altcode: During an international campaign in 2014, utilising both space-based (IRIS and Hinode) and ground-based (THEMIS) instruments, we focused on observing prominences. We compare IRIS observations with those of Hinode (EIS and SOT) in order to build a more complete picture of the prominence structure for a quiescent prominence observed on 15 July 2014, identified to have tornado-like structure. THEMIS provides valuable information on the orientation and strength of the internal magnetic field. Here we find there is almost ubiquitously horizontal field with respect to the local limb, with possibly a turbulent component. The Mg II lines form the majority of our IRIS analysis, with a mixture of reversed and non-reversed profiles present in the prominence spectra. Comparing the differences between the Mg II data from IRIS and the Ca II images from Hinode/SOT provides an intriguing insight into the prominence legs in these channels. We present plasma diagnostics from IRIS, with line of sight velocities of around 10 km/s in either direction along the magnetic loops of material in the front of the prominence, and line widths comparable to those found for prominences by previous authors (e.g. Schmieder et al. 2014). We also take a look into the lines formed at higher, coronal plasma temperatures, as seen by Hinode/EIS, to compare plasma structures at a full range of temperatures. Title: Interaction of Two Filament Channels of Different Chiralities Authors: Joshi, Navin Chandra; Filippov, Boris; Schmieder, Brigitte; Magara, Tetsuya; Moon, Yong-Jae; Uddin, Wahab Bibcode: 2016ApJ...825..123J Altcode: 2016arXiv160501812J We present observations of the interactions between the two filament channels of different chiralities and associated dynamics that occurred during 2014 April 18-20. While two flux ropes of different helicity with parallel axial magnetic fields can only undergo a bounce interaction when they are brought together, the observations at first glance show that the heated plasma is moving from one filament channel to the other. The SDO/AIA 171 Å observations and the potential-field source-surface magnetic field extrapolation reveal the presence of a fan-spine magnetic configuration over the filament channels with a null point located above them. Three different events of filament activations, partial eruptions, and associated filament channel interactions have been observed. The activation initiated in one filament channel seems to propagate along the neighboring filament channel. We believe that the activation and partial eruption of the filaments brings the field lines of flux ropes containing them closer to the null point and triggers the magnetic reconnection between them and the fan-spine magnetic configuration. As a result, the hot plasma moves along the outer spine line toward the remote point. Utilizing the present observations, for the first time we have discussed how two different-chirality filament channels can interact and show interrelation. Title: Hooked Flare Ribbons and Flux-rope-related QSL Footprints Authors: Zhao, Jie; Gilchrist, Stuart A.; Aulanier, Guillaume; Schmieder, Brigitte; Pariat, Etienne; Li, Hui Bibcode: 2016ApJ...823...62Z Altcode: 2016arXiv160307563Z We studied the magnetic topology of active region 12158 on 2014 September 10 and compared it with the observations before and early in the flare that begins at 17:21 UT (SOL2014-09-10T17:45:00). Our results show that the sigmoidal structure and flare ribbons of this active region observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly can be well reproduced from a Grad-Rubin nonlinear force-free field extrapolation method. Various inverse-S- and inverse-J-shaped magnetic field lines, which surround a coronal flux rope, coincide with the sigmoid as observed in different extreme-ultraviolet wavelengths, including its multithreaded curved ends. Also, the observed distribution of surface currents in the magnetic polarity where it was not prescribed is well reproduced. This validates our numerical implementation and setup of the Grad-Rubin method. The modeled double inverse-J-shaped quasi-separatrix layer (QSL) footprints match the observed flare ribbons during the rising phase of the flare, including their hooked parts. The spiral-like shape of the latter may be related to a complex pre-eruptive flux rope with more than one turn of twist, as obtained in the model. These ribbon-associated flux-rope QSL footprints are consistent with the new standard flare model in 3D, with the presence of a hyperbolic flux tube located below an inverse-teardrop-shaped coronal QSL. This is a new step forward forecasting the locations of reconnection and ribbons in solar flares and the geometrical properties of eruptive flux ropes. Title: Slipping Magnetic Reconnection, Chromospheric Evaporation, Implosion, and Precursors in the 2014 September 10 X1.6-Class Solar Flare Authors: Dudík, Jaroslav; Polito, Vanessa; Janvier, Miho; Mulay, Sargam M.; Karlický, Marian; Aulanier, Guillaume; Del Zanna, Giulio; Dzifčáková, Elena; Mason, Helen E.; Schmieder, Brigitte Bibcode: 2016ApJ...823...41D Altcode: 2016arXiv160306092D We investigate the occurrence of slipping magnetic reconnection, chromospheric evaporation, and coronal loop dynamics in the 2014 September 10 X-class flare. Slipping reconnection is found to be present throughout the flare from its early phase. Flare loops are seen to slip in opposite directions toward both ends of the ribbons. Velocities of 20-40 km s-1 are found within time windows where the slipping is well resolved. The warm coronal loops exhibit expanding and contracting motions that are interpreted as displacements due to the growing flux rope that subsequently erupts. This flux rope existed and erupted before the onset of apparent coronal implosion. This indicates that the energy release proceeds by slipping reconnection and not via coronal implosion. The slipping reconnection leads to changes in the geometry of the observed structures at the Interface Region Imaging Spectrograph slit position, from flare loop top to the footpoints in the ribbons. This results in variations of the observed velocities of chromospheric evaporation in the early flare phase. Finally, it is found that the precursor signatures, including localized EUV brightenings as well as nonthermal X-ray emission, are signatures of the flare itself, progressing from the early phase toward the impulsive phase, with the tether-cutting being provided by the slipping reconnection. The dynamics of both the flare and outlying coronal loops is found to be consistent with the predictions of the standard solar flare model in three dimensions. Title: Magnetic Field and Plasma Diagnostics from Coordinated Prominence Observations Authors: Schmieder, B.; Levens, P.; Dalmasse, K.; Mein, N.; Mein, P.; Lopez-Ariste, A.; Labrosse, N.; Heinzel, P. Bibcode: 2016ASPC..504..119S Altcode: We study the magnetic field in prominences from a statistical point of view, by using THEMIS in the MTR mode, performing spectropolarimetry of the He I D3 line. Combining these measurements with spectroscopic data from IRIS, Hinode/EIS as well as ground-based telescopes, such as the Meudon Solar Tower, we infer the temperature, density, and flow velocities of the plasma. There are a number of open questions that we aim to answer: - What is the general direction of the magnetic field in prominences? Is the model using a single orientation of magnetic field always valid for atypical prominences? %- Does this depend on the location of the filament on the disk (visible in Hα, in He II 304 Å) over an inversion line between weak or strong network ? - Are prominences in a weak environment field dominated by gas pressure? - Measuring the Doppler shifts in Mg II lines (with IRIS) and in Hα can tell us if there are substantial velocities to maintain vertical rotating structures, as has been suggested for tornado-like prominences. We present here some results obtained with different ground-based and space-based instruments in this framework. Title: Chain Reconnections Observed in Sympathetic Eruptions Authors: Joshi, Navin Chandra; Schmieder, Brigitte; Magara, Tetsuya; Guo, Yang; Aulanier, Guillaume Bibcode: 2016ApJ...820..126J Altcode: 2016arXiv160207792J The nature of various plausible causal links between sympathetic events is still a controversial issue. In this work, we present multiwavelength observations of sympathetic eruptions, associated flares, and coronal mass ejections (CMEs) occurring on 2013 November 17 in two close active regions. Two filaments, I.e., F1 and F2, are observed in between the active regions. Successive magnetic reconnections, caused for different reasons (flux cancellation, shear, and expansion) have been identified during the whole event. The first reconnection occurred during the first eruption via flux cancellation between the sheared arcades overlying filament F2, creating a flux rope and leading to the first double-ribbon solar flare. During this phase, we observed the eruption of overlying arcades and coronal loops, which leads to the first CME. The second reconnection is believed to occur between the expanding flux rope of F2 and the overlying arcades of filament F1. We suggest that this reconnection destabilized the equilibrium of filament F1, which further facilitated its eruption. The third stage of reconnection occurred in the wake of the erupting filament F1 between the legs of the overlying arcades. This may create a flux rope and the second double-ribbon flare and a second CME. The fourth reconnection was between the expanding arcades of the erupting filament F1 and the nearby ambient field, which produced the bi-directional plasma flows both upward and downward. Observations and a nonlinear force-free field extrapolation confirm the possibility of reconnection and the causal link between the magnetic systems. Title: Structure of Prominence Legs: Plasma and Magnetic Field Authors: Levens, P. J.; Schmieder, B.; Labrosse, N.; López Ariste, A. Bibcode: 2016ApJ...818...31L Altcode: 2015arXiv151204727L We investigate the properties of a “solar tornado” observed on 2014 July 15, and aim to link the behavior of the plasma to the internal magnetic field structure of the associated prominence. We made multi-wavelength observations with high spatial resolution and high cadence using SDO/AIA, the Interface Region Imaging Spectrograph (IRIS) spectrograph, and the Hinode/Solar Optical Telescope (SOT) instrument. Along with spectropolarimetry provided by the Télescope Héliographique pour l’Etude du Magnétisme et des Instabilités Solaires telescope we have coverage of both optically thick emission lines and magnetic field information. AIA reveals that the two legs of the prominence are strongly absorbing structures which look like they are rotating, or oscillating in the plane of the sky. The two prominence legs, which are both very bright in Ca II (SOT), are not visible in the IRIS Mg II slit-jaw images. This is explained by the large optical thickness of the structures in Mg II, which leads to reversed profiles, and hence to lower integrated intensities at these locations than in the surroundings. Using lines formed at temperatures lower than 1 MK, we measure relatively low Doppler shifts on the order of ±10 km s-1 in the tornado-like structure. Between the two legs we see loops in Mg II, with material flowing from one leg to the other, as well as counterstreaming. It is difficult to interpret our data as showing two rotating, vertical structures that are unrelated to the loops. This kind of “tornado” scenario does not fit with our observations. The magnetic field in the two legs of the prominence is found to be preferentially horizontal. Title: Role of "X point'' in Flares and Filament Interactions Authors: Schmieder, B.; Zuccarello, F. P.; Aulanier, G.; Chandra, R.; Joshi, N. C.; Filippov, B. Bibcode: 2016CEAB...40...35S Altcode: Explaining the trigger and energy release processes of flares is a fundamental problem of solar physics. It is commonly held that magnetic reconnection plays a key role in converting magnetic energy into other forms of energy. In 2D magnetic field configurations, when oppositely directed magnetic fields are brought together they may reconnect thereby releasing stored magnetic energy eventually resulting in a flare. In 3D configurations, the magnetic topology should be considered and the reconnection is favored at the intersection of magnetic quasi-separatrix layers, which is an extension of what is called "X point" in 2D. The evolution of key topological structures, such as null point, spines and fans may determine the eruptive behavior of a flare. The presence of a null point can be very important. We present a few examples, i.e., a flare with a circular flare ribbon and the interaction of two parallel filaments.

In the case of flux rope destabilization and triggering eruption due to the torus instability, the important parameter is the decay index and not the topology itself. However the complexity of active regions leads to interpretations where different mechanisms may be intermixed. The breakout mechanism, which requires a quadrupolar configuration with QSLs and separator where the reconnection can occur, is present in many models. That is not always a sufficient condition to explain the eruptive flares. For one case study, the different behaviour of a series of eruptive flares followed by confined flares, all originating in the same site has been attributed to the change of orientation of the magnetic field below the fan with respect to the orientation of the spine. Flares tend to be more confined when the two fields become less antiparallel. Title: ALMA Observations of the Sun in Cycle 4 and Beyond Authors: Wedemeyer, S.; Fleck, B.; Battaglia, M.; Labrosse, N.; Fleishman, G.; Hudson, H.; Antolin, P.; Alissandrakis, C.; Ayres, T.; Ballester, J.; Bastian, T.; Black, J.; Benz, A.; Brajsa, R.; Carlsson, M.; Costa, J.; DePontieu, B.; Doyle, G.; Gimenez de Castro, G.; Gunár, S.; Harper, G.; Jafarzadeh, S.; Loukitcheva, M.; Nakariakov, V.; Oliver, R.; Schmieder, B.; Selhorst, C.; Shimojo, M.; Simões, P.; Soler, R.; Temmer, M.; Tiwari, S.; Van Doorsselaere, T.; Veronig, A.; White, S.; Yagoubov, P.; Zaqarashvili, T. Bibcode: 2016arXiv160100587W Altcode: This document was created by the Solar Simulations for the Atacama Large Millimeter Observatory Network (SSALMON) in preparation of the first regular observations of the Sun with the Atacama Large Millimeter/submillimeter Array (ALMA), which are anticipated to start in ALMA Cycle 4 in October 2016. The science cases presented here demonstrate that a large number of scientifically highly interesting observations could be made already with the still limited solar observing modes foreseen for Cycle 4 and that ALMA has the potential to make important contributions to answering long-standing scientific questions in solar physics. With the proposal deadline for ALMA Cycle 4 in April 2016 and the Commissioning and Science Verification campaign in December 2015 in sight, several of the SSALMON Expert Teams composed strategic documents in which they outlined potential solar observations that could be feasible given the anticipated technical capabilities in Cycle 4. These documents have been combined and supplemented with an analysis, resulting in recommendations for solar observing with ALMA in Cycle 4. In addition, the detailed science cases also demonstrate the scientific priorities of the solar physics community and which capabilities are wanted for the next observing cycles. The work on this White Paper effort was coordinated in close cooperation with the two international solar ALMA development studies led by T. Bastian (NRAO, USA) and R. Brajsa, (ESO). This document will be further updated until the beginning of Cycle 4 in October 2016. In particular, we plan to adjust the technical capabilities of the solar observing modes once finally decided and to further demonstrate the feasibility and scientific potential of the included science cases by means of numerical simulations of the solar atmosphere and corresponding simulated ALMA observations. Title: Flare-CME Models: An Observational Perspective (Invited Review) Authors: Schmieder, B.; Aulanier, G.; Vršnak, B. Bibcode: 2015SoPh..290.3457S Altcode: 2015SoPh..tmp...64S Eruptions, flares, and coronal mass ejection (CMEs) are due to physical phenomena mainly driven by an initially force-free current-carrying magnetic field. We review some key observations relevant to the current theoretical trigger mechanisms of the eruption and to the energy release via reconnection. Sigmoids observed in X-rays and UV, as well as the pattern (double J-shaped) of electric currents in the photosphere show clear evidence of the existence of currents parallel to the magnetic field and can be the signature of a flux rope that is detectable in CMEs. The magnetic helicity of filaments and active regions is an interesting indirectly measurable parameter because it can quantify the twist of the flux rope. On the other hand, the magnetic helicity of the solar structures allows us to associate solar eruptions and magnetic clouds in the heliosphere. The magnetic topology analysis based on the 3D magnetic field extrapolated from vector magnetograms is a good tool for identifying the reconnection locations (null points and/or the 3D large volumes - hyperbolic flux tube, HFT). Flares are associated more with quasi-separatrix layers (QSLs) and HFTs than with a single null point, which is a relatively rare case. We review various mechanisms that have been proposed to trigger CMEs and their observable signatures: by "breaking" the field lines overlying the flux rope or by reconnection below the flux rope to reduce the magnetic tension, or by letting the flux rope to expand until it reaches a minimum threshold height (loss of equilibrium or torus instability). Additional mechanisms are commonly operating in the solar atmosphere. Examples of observations are presented throughout the article and are discussed in this framework. Title: Nonlinear MHD Waves in a Prominence Foot Authors: Ofman, L.; Knizhnik, K.; Kucera, T.; Schmieder, B. Bibcode: 2015ApJ...813..124O Altcode: 2015arXiv150907911O We study nonlinear waves in a prominence foot using a 2.5D MHD model motivated by recent high-resolution observations with Hinode/Solar Optical Telescope in Ca ii emission of a prominence on 2012 October 10 showing highly dynamic small-scale motions in the prominence material. Observations of Hα intensities and of Doppler shifts show similar propagating fluctuations. However, the optically thick nature of the emission lines inhibits a unique quantitative interpretation in terms of density. Nevertheless, we find evidence of nonlinear wave activity in the prominence foot by examining the relative magnitude of the fluctuation intensity (δI/I ∼ δn/n). The waves are evident as significant density fluctuations that vary with height and apparently travel upward from the chromosphere into the prominence material with quasi-periodic fluctuations with a typical period in the range of 5-11 minutes and wavelengths <2000 km. Recent Doppler shift observations show the transverse displacement of the propagating waves. The magnetic field was measured with the THEMIS instrument and was found to be 5-14 G. For the typical prominence density the corresponding fast magnetosonic speed is ∼20 km s-1, in qualitative agreement with the propagation speed of the detected waves. The 2.5D MHD numerical model is constrained with the typical parameters of the prominence waves seen in observations. Our numerical results reproduce the nonlinear fast magnetosonic waves and provide strong support for the presence of these waves in the prominence foot. We also explore gravitational MHD oscillations of the heavy prominence foot material supported by dipped magnetic field structure. Title: A solar tornado observed by EIS. Plasma diagnostics Authors: Levens, P. J.; Labrosse, N.; Fletcher, L.; Schmieder, B. Bibcode: 2015A&A...582A..27L Altcode: 2015arXiv150801377L Context. The term "solar tornadoes" has been used to describe apparently rotating magnetic structures above the solar limb, as seen in high resolution images and movies from the Atmospheric Imaging Assembly (AIA) aboard the Solar Dynamics Observatory (SDO). These often form part of the larger magnetic structure of a prominence, however the links between them remain unclear. Here we present plasma diagnostics on a tornado-like structure and its surroundings, seen above the limb by the Extreme-ultraviolet Imaging Spectrometer (EIS) aboard the Hinode satellite.
Aims: We aim to extend our view of the velocity patterns seen in tornado-like structures with EIS to a wider range of temperatures and to use density diagnostics, non-thermal line widths, and differential emission measures to provide insight into the physical characteristics of the plasma.
Methods: Using Gaussian fitting to fit and de-blend the spectral lines seen by EIS, we calculated line-of-sight velocities and non-thermal line widths. Along with information from the CHIANTI database, we used line intensity ratios to calculate electron densities at each pixel. Using a regularised inversion code we also calculated the differential emission measure (DEM) at different locations in the prominence.
Results: The split Doppler-shift pattern is found to be visible down to a temperature of around log T = 6.0. At temperatures lower than this, the pattern is unclear in this data set. We obtain an electron density of log ne = 8.5 when looking towards the centre of the tornado structure at a plasma temperature of log T = 6.2, as compared to the surroundings of the tornado structure where we find log ne to be nearer 9. Non-thermal line widths show broader profiles at the tornado location when compared to the surrounding corona. We discuss the differential emission measure in both the tornado and the prominence body, which suggests that there is more contribution in the tornado at temperatures below log T = 6.0 than in the prominence.

A movie is available in electronic form at http://www.aanda.org Title: Polarimetric measurements in prominences and "tornadoe" observed by THEMIS Authors: Schmieder, Brigitte; López Ariste, Arturo; Levens, Peter; Labrosse, Nicolas; Dalmasse, Kévin Bibcode: 2015IAUS..305..275S Altcode: Since 2013, coordinated campaigns with the THEMIS spectropolarimeter in Tenerife and other instruments (space based: Hinode/SOT, IRIS or ground based: Sac Peak, Meudon) are organized to observe prominences. THEMIS records spectropolarimetry at the He I D3 and we use the PCA inversion technique to derive their field strength, inclination and azimuth. Title: Coronal Mass Ejections from the Same Active Region Cluster: Two Different Perspectives Authors: Cremades, H.; Mandrini, C. H.; Schmieder, B.; Crescitelli, A. M. Bibcode: 2015SoPh..290.1671C Altcode: 2015arXiv150501384C; 2015SoPh..tmp...86C The cluster formed by active regions (ARs) NOAA 11121 and 11123, approximately located on the solar central meridian on 11 November 2010, is of great scientific interest. This complex was the site of violent flux emergence and the source of a series of Earth-directed events on the same day. The onset of the events was nearly simultaneously observed by the Atmospheric Imaging Assembly (AIA) telescope onboard the Solar Dynamics Observatory (SDO) and the Extreme-Ultraviolet Imagers (EUVI) on the Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI) suite of telescopes onboard the Solar-Terrestrial Relations Observatory (STEREO) twin spacecraft. The progression of these events in the low corona was tracked by the Large Angle Spectroscopic Coronagraphs (LASCO) onboard the Solar and Heliospheric Observatory (SOHO) and the SECCHI/COR coronagraphs on STEREO. SDO and SOHO imagers provided data from the Earth's perspective, whilst the STEREO twin instruments procured images from the orthogonal directions. This spatial configuration of spacecraft allowed optimum simultaneous observations of the AR cluster and the coronal mass ejections that originated in it. Quadrature coronal observations provided by STEREO revealed many more ejective events than were detected from Earth. Furthermore, joint observations by SDO/AIA and STEREO/SECCHI EUVI of the source region indicate that all events classified by GOES as X-ray flares had an ejective coronal counterpart in quadrature observations. These results directly affect current space weather forecasting because alarms might be missed when there is a lack of solar observations in a view direction perpendicular to the Sun-Earth line. Title: Understanding the Mg II and Hα Spectra in a Highly Dynamical Solar Prominence Authors: Heinzel, P.; Schmieder, B.; Mein, N.; Gunár, S. Bibcode: 2015ApJ...800L..13H Altcode: Mg ii h and k and Hα spectra in a dynamical prominence have been obtained along the slit of the Interface Region Imaging Spectrograph (IRIS) and with the Meudon Multi-channel Subtractive Double Pass spectrograph on 2013 September 24, respectively. Single Mg ii line profiles are not much reversed, while at some positions along the IRIS slit the profiles show several discrete peaks that are Doppler-shifted. The intensity of these peaks is generally decreasing with their increasing Doppler shift. We interpret this unusual behavior as being due to the Doppler dimming effect. We discuss the possibility to interpret the unreversed single profiles by using a two-dimensional (2D) model of the entire prominence body with specific radiative boundary conditions. We have performed new 2D isothermal-isobaric modeling of both Hα and Mg ii lines and show the ability of such models to account for the line profile variations as observed. However, the Mg ii line-center intensities require the model with a temperature increase toward the prominence boundary. We show that even simple one-dimensional (1D) models with a prominence-to-corona transition region (PCTR) fit the observed Mg ii and Hα lines quite well, while the isothermal-isobaric models (1D or 2D) are inconsistent with simultaneous observations in the Mg ii h and k and Hα lines, meaning that the Hα line provides a strong additional constraint on the modeling. IRIS far-UV detection of the C ii lines in this prominence seems to provide a direct constraint on the PCTR part of the model. Title: Can we explain atypical solar flares? Authors: Dalmasse, K.; Chandra, R.; Schmieder, B.; Aulanier, G. Bibcode: 2015A&A...574A..37D Altcode: 2014arXiv1410.8194D Context. We used multiwavelength high-resolution data from ARIES, THEMIS, and SDO instruments to analyze a non-standard, C3.3 class flare produced within the active region NOAA 11589 on 2012 October 16. Magnetic flux emergence and cancellation were continuously detected within the active region, the latter leading to the formation of two filaments.
Aims: Our aim is to identify the origins of the flare taking the complex dynamics of its close surroundings into account.
Methods: We analyzed the magnetic topology of the active region using a linear force-free field extrapolation to derive its 3D magnetic configuration and the location of quasi-separatrix layers (QSLs), which are preferred sites for flaring activity. Because the active region's magnetic field was nonlinear force-free, we completed a parametric study using different linear force-free field extrapolations to demonstrate the robustness of the derived QSLs.
Results: The topological analysis shows that the active region presented a complex magnetic configuration comprising several QSLs. The considered data set suggests that an emerging flux episode played a key role in triggering the flare. The emerging flux probably activated the complex system of QSLs, leading to multiple coronal magnetic reconnections within the QSLs. This scenario accounts for the observed signatures: the two extended flare ribbons developed at locations matched by the photospheric footprints of the QSLs and were accompanied with flare loops that formed above the two filaments, which played no important role in the flare dynamics.
Conclusions: This is a typical example of a complex flare that can a priori show standard flare signatures that are nevertheless impossible to interpret with any standard model of eruptive or confined flare. We find that a topological analysis, however, permitted us to unveil the development of such complex sets of flare signatures.

Movies associated to Figs. 1, 3, and 9 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/574/A37 Title: Magnetic Flux Emergence Along the Solar Cycle Authors: Schmieder, B.; Archontis, V.; Pariat, E. Bibcode: 2015sac..book..227S Altcode: No abstract at ADS Title: VizieR Online Data Catalog: Movies of 2012-10-16 solar flare (Dalmasse+, 2015) Authors: Dalmasse, K.; Chandra, R.; Schmieder, B.; Aulanier, G. Bibcode: 2015yCat..35740037D Altcode: 2015yCat..35749037D Part of the observations of NOAA 11589 presented here were obtained with the Atmospheric Imaging Assembly imager (AIA) and the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamic Observatory (SDO) satellite. The AIA instrument observes the Sun over a wide range of temperatures from the photosphere to the corona. The pixel size of the AIA images is 0.6". In this study, we considered the 1600, 304, 193, and 171Å data. The magnetic field in the AR was studied by using the line-of-sight magnetograms of the HMI instrument, which observes the full disk with a pixel size of 0.5".

We also used ground-based observations of the AR obtained with the Indian telescope from the Aryabhatta Research Institute of observational Sciences (ARIES) and with the French Telescope Heliographique pour l'Etude du Magnetisme et des Instabilites Solaires (THEMIS). The 15-cm f/15 Coude telescope of the ARIES, operating in Nainital (India), observes in the Hα line with a spatial resolution of 0.58". The THEMIS telescope, operating in Tenerife (Canary Islands), allows a simultaneous mapping of the Hα emission and the full Stokes parameters in the Fe 6302.5Å of a field of view of about 240"x100" in one hour.

(2 data files). Title: Magnetic Flux Emergence Along the Solar Cycle Authors: Schmieder, B.; Archontis, V.; Pariat, E. Bibcode: 2014SSRv..186..227S Altcode: 2014SSRv..tmp...47S Flux emergence plays an important role along the solar cycle. Magnetic flux emergence builds sunspot groups and solar activity. The sunspot groups contribute to the large scale behaviour of the magnetic field over the 11 year cycle and the reversal of the North and South magnetic polarity every 22 years. The leading polarity of sunspot groups is opposite in the North and South hemispheres and reverses for each new solar cycle. However the hemispheric rule shows the conservation of sign of the magnetic helicity with positive and negative magnetic helicity in the South and North hemispheres, respectively. MHD models of emerging flux have been developed over the past twenty years but have not yet succeeded to reproduce solar observations. The emergence of flux occurs through plasma layers of very high gradients of pressure and changing of modes from a large β to a low β plasma (<1). With the new armada of high spatial and temporal resolution instruments on the ground and in space, emergence of magnetic flux is observed in tremendous detail and followed during their transit through the upper atmosphere. Signatures of flux emergence in the corona depend on the pre-existing magnetic configuration and on the strength of the emerging flux. We review in this paper new and established models as well as the recent observations. Title: Recurrent Coronal Jets Induced by Magnetic Emergence in the Solar Atmosphere Authors: Guo, Y.; Démoulin, P.; Schmieder, B.; Ding, M. D.; Vargas Domínguez, S.; Liu, Y. Bibcode: 2014RMxAC..44...45G Altcode: Jets are part of the observed phenomenology in the solar corona. They are thought to be a consequence of magnetic reconnection but the physics involved is not completely understood. We study some recurrent jetting events with unprecedented temporal and spatial resolutions. Title: Open questions on prominences from coordinated observations by IRIS, Hinode, SDO/AIA, THEMIS, and the Meudon/MSDP Authors: Schmieder, B.; Tian, H.; Kucera, T.; López Ariste, A.; Mein, N.; Mein, P.; Dalmasse, K.; Golub, L. Bibcode: 2014A&A...569A..85S Altcode: 2014arXiv1407.3171S Context. A large prominence was observed by multiple instruments on the ground and in space during an international campaign on September 24, 2013, for three hours (12:12 UT -15:12 UT). Instruments used in the campaign included the newly launched (June 2013) Interface Region Imaging Spectrograph (IRIS), THEMIS (Tenerife), the Hinode Solar Optical Telescope (SOT), the Solar Dynamic Observatory's Atmospheric Imaging Assembly (SDO/AIA), and the Multichannel Subtractive Double Pass spectrograph (MSDP) in the Meudon Solar Tower. The movies obtained in 304 Å with the EUV imager SDO/AIA, and in Ca II line by SOT show the dynamic nature of the prominence.
Aims: The aim of this work is to study the dynamics of the prominence fine structures in multiple wavelengths to understand their formation.
Methods: The spectrographs IRIS and MSDP provided line profiles with a high cadence in Mg II h (2803.5 Å) and k (2796.4 Å) lines along four slit positions (IRIS), and in Hα in a 2D field of view (MSDP). The spectropolarimetry of THEMIS (Tenerife) allowed us to derive the magnetic field of the prominence using the He D3 line depolarization (Hanle effect combined with the Zeeman effect).
Results: The magnetic field is found to be globally horizontal with a relatively weak field strength (8-15 Gauss). On the other hand, the Ca II movie reveals turbulent-like motion that is not organized in specific parts of the prominence. We tested the addition of a turbulent magnetic component. This model is compatible with the polarimetric observations at those places where the plasma turbulence peaks. On the other hand, the Mg II line profiles show multiple peaks well separated in wavelength. This is interpreted by the existence of small threads along the line of sight with a large dispersion of discrete values of Doppler shifts, from 5 km s-1 (a quasi-steady component) to 60-80 km s-1. Each peak corresponds to a Gaussian profile, and not to a reversed profile as was expected by the present non-LTE radiative transfer modeling. This is a very surprising behavior for the Mg II line observed in prominences.
Conclusions: Turbulent fields on top of the macroscopic horizontal component of the magnetic field supporting the prominence give rise to the complex dynamics of the plasma. The plasma with the high velocities (70 km s-1 to 100 km s-1 if we take into account the transverse velocities) may correspond to condensation of plasma along more or less horizontal threads of the arch-shape structure visible in 304 Å. The steady flows (5 km s-1) would correspond to a more quiescent plasma (cool and prominence-corona transition region) of the prominence packed into dips in horizontal magnetic field lines. The very weak secondary peaks in the Mg II profiles may reflect the turbulent nature of parts of the prominence.

Movies are available in electronic form at http://www.aanda.org Title: Magnetic field and radiative transfer modelling of a quiescent prominence Authors: Gunár, S.; Schwartz, P.; Dudík, J.; Schmieder, B.; Heinzel, P.; Jurčák, J. Bibcode: 2014A&A...567A.123G Altcode:
Aims: The aim of this work is to analyse the multi-instrument observations of the June 22, 2010 prominence to study its structure in detail, including the prominence-corona transition region and the dark bubble located below the prominence body.
Methods: We combined results of the 3D magnetic field modelling with 2D prominence fine structure radiative transfer models to fully exploit the available observations.
Results: The 3D linear force-free field model with the unsheared bipole reproduces the morphology of the analysed prominence reasonably well, thus providing useful information about its magnetic field configuration and the location of the magnetic dips. The 2D models of the prominence fine structures provide a good representation of the local plasma configuration in the region dominated by the quasi-vertical threads. However, the low observed Lyman-α central intensities and the morphology of the analysed prominence suggest that its upper central part is not directly illuminated from the solar surface.
Conclusions: This multi-disciplinary prominence study allows us to argue that a large part of the prominence-corona transition region plasma can be located inside the magnetic dips in small-scale features that surround the cool prominence material located in the dip centre. We also argue that the dark prominence bubbles can be formed because of perturbations of the prominence magnetic field by parasitic bipoles, causing them to be devoid of the magnetic dips. Magnetic dips, however, form thin layers that surround these bubbles, which might explain the occurrence of the cool prominence material in the lines of sight intersecting the prominence bubbles.

Movie and Appendix A are available in electronic form at http://www.aanda.org Title: Time Evolution of the Altitude of an Observed Coronal Wave Authors: Delannée, C.; Artzner, G.; Schmieder, B.; Parenti, S. Bibcode: 2014SoPh..289.2565D Altcode: 2014SoPh..tmp...49D; 2013arXiv1310.5623D The nature of coronal wave fronts is intensely debated. They are observed in several wavelength bands and are frequently interpreted as magnetosonic waves propagating in the lower solar atmosphere. However, they can also be attributed to the line-of-sight projection of the edges of coronal mass ejections. Therefore, estimating the altitude of these features is crucial for deciding in favor of one of these two interpretations. We took advantage of a set of observations obtained from two different view directions by the EUVI instrument onboard the STEREO mission on 7 December 2007 to derive the time evolution of the altitude of a coronal wave front. We developed a new technique to compute the altitude of the coronal wave and found that the altitude increased during the initial 5 min and then slightly decreased back to the low corona. We interpret the evolution of the altitude as follows: the increase in the altitude of the wave front is linked to the rise of a bubble-like structure depending on whether it is a magnetosonic wave front or a CME in the initial phase. During the second phase, the observed brightness of the wave front was mixed with the brightening of the underlying magnetic structures as the emission from the wave front faded because the plasma became diluted with altitude. Title: Electric Currents in Flare Ribbons: Observations and Three-dimensional Standard Model Authors: Janvier, M.; Aulanier, G.; Bommier, V.; Schmieder, B.; Démoulin, P.; Pariat, E. Bibcode: 2014ApJ...788...60J Altcode: 2014arXiv1402.2010J We present for the first time the evolution of the photospheric electric currents during an eruptive X-class flare, accurately predicted by the standard three-dimensional (3D) flare model. We analyze this evolution for the 2011 February 15 flare using Helioseismic and Magnetic Imager/Solar Dynamics Observatory magnetic observations and find that localized currents in J-shaped ribbons increase to double their pre-flare intensity. Our 3D flare model, developed with the OHM code, suggests that these current ribbons, which develop at the location of extreme ultraviolet brightenings seen with Atmospheric Imaging Assembly imagery, are driven by the collapse of the flare's coronal current layer. These findings of increased currents restricted in localized ribbons are consistent with the overall free energy decrease during a flare, and the shapes of these ribbons also give an indication of how twisted the erupting flux rope is. Finally, this study further enhances the close correspondence obtained between the theoretical predictions of the standard 3D model and flare observations, indicating that the main key physical elements are incorporated in the model. Title: Topological Analysis of Emerging Bipole Clusters Producing Violent Solar Events Authors: Mandrini, C. H.; Schmieder, B.; Démoulin, P.; Guo, Y.; Cristiani, G. D. Bibcode: 2014SoPh..289.2041M Altcode: 2013arXiv1312.3359M During the rising phase of Solar Cycle 24 tremendous activity occurred on the Sun with rapid and compact emergence of magnetic flux leading to bursts of flares (C to M and even X-class). We investigate the violent events occurring in the cluster of two active regions (ARs), NOAA numbers 11121 and 11123, observed in November 2010 with instruments onboard the Solar Dynamics Observatory and from Earth. Within one day the total magnetic flux increased by 70 % with the emergence of new groups of bipoles in AR 11123. From all the events on 11 November, we study, in particular, the ones starting at around 07:16 UT in GOES soft X-ray data and the brightenings preceding them. A magnetic-field topological analysis indicates the presence of null points, associated separatrices, and quasi-separatrix layers (QSLs) where magnetic reconnection is prone to occur. The presence of null points is confirmed by a linear and a non-linear force-free magnetic-field model. Their locations and general characteristics are similar in both modelling approaches, which supports their robustness. However, in order to explain the full extension of the analysed event brightenings, which are not restricted to the photospheric traces of the null separatrices, we compute the locations of QSLs. Based on this more complete topological analysis, we propose a scenario to explain the origin of a low-energy event preceding a filament eruption, which is accompanied by a two-ribbon flare, and a consecutive confined flare in AR 11123. The results of our topology computation can also explain the locations of flare ribbons in two other events, one preceding and one following the ones at 07:16 UT. Finally, this study provides further examples where flare-ribbon locations can be explained when compared to QSLs and only, partially, when using separatrices. Title: Temporal Evolution of the Magnetic Topology of the NOAA Active Region 11158 Authors: Zhao, Jie; Li, Hui; Pariat, Etienne; Schmieder, Brigitte; Guo, Yang; Wiegelmann, Thomas Bibcode: 2014ApJ...787...88Z Altcode: 2014arXiv1404.5004Z We studied the temporal evolution of the magnetic topology of the active region (AR) 11158 based on the reconstructed three-dimensional magnetic fields in the corona. The non-linear force-free field extrapolation method was applied to the 12 minute cadence data obtained with the Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory during 5 days. By calculating the squashing degree factor Q in the volume, the derived quasi-separatrix layers (QSLs) show that this AR has an overall topology, resulting from a magnetic quadrupole, including a hyperbolic flux tube (HFT) configuration that is relatively stable at the timescale of the flare (~1-2 hr). A strong QSL, which corresponds to some highly sheared arcades that might be related to the formation of a flux rope, is prominent just before the M6.6 and X2.2 flares, respectively. These facts indicate the close relationship between the strong QSL and the high flare productivity of AR 11158. In addition, with a close inspection of the topology, we found a small-scale HFT that has an inverse tear-drop structure above the aforementioned QSL before the X2.2 flare. It indicates the existence of magnetic flux rope at this place. Even though a global configuration (HFT) is recognized in this AR, it turns out that the large-scale HFT only plays a secondary role during the eruption. In conclusion, we dismiss a trigger based on the breakout model and highlight the central role of the flux rope in the related eruption. Title: Detection of Coherent Structures in Photospheric Turbulent Flows Authors: Chian, Abraham C. -L.; Rempel, Erico L.; Aulanier, Guillaume; Schmieder, Brigitte; Shadden, Shawn C.; Welsch, Brian T.; Yeates, Anthony R. Bibcode: 2014ApJ...786...51C Altcode: 2013arXiv1312.2405C We study coherent structures in solar photospheric flows in a plage in the vicinity of the active region AR 10930 using the horizontal velocity data derived from Hinode/Solar Optical Telescope magnetograms. Eulerian and Lagrangian coherent structures (LCSs) are detected by computing the Q-criterion and the finite-time Lyapunov exponents of the velocity field, respectively. Our analysis indicates that, on average, the deformation Eulerian coherent structures dominate over the vortical Eulerian coherent structures in the plage region. We demonstrate the correspondence of the network of high magnetic flux concentration to the attracting Lagrangian coherent structures (aLCSs) in the photospheric velocity based on both observations and numerical simulations. In addition, the computation of aLCS provides a measure of the local rate of contraction/expansion of the flow. Title: Slipping Magnetic Reconnection during an X-class Solar Flare Observed by SDO/AIA Authors: Dudík, J.; Janvier, M.; Aulanier, G.; Del Zanna, G.; Karlický, M.; Mason, H. E.; Schmieder, B. Bibcode: 2014ApJ...784..144D Altcode: 2014arXiv1401.7529D We present SDO/AIA observations of an eruptive X-class flare of 2012 July 12, and compare its evolution with the predictions of a three-dimensional (3D) numerical simulation. We focus on the dynamics of flare loops that are seen to undergo slipping reconnection during the flare. In the Atmospheric Imaging Assembly (AIA) 131 Å observations, lower parts of 10 MK flare loops exhibit an apparent motion with velocities of several tens of km s-1 along the developing flare ribbons. In the early stages of the flare, flare ribbons consist of compact, localized bright transition-region emission from the footpoints of the flare loops. A differential emission measure analysis shows that the flare loops have temperatures up to the formation of Fe XXIV. A series of very long, S-shaped loops erupt, leading to a coronal mass ejection observed by STEREO. The observed dynamics are compared with the evolution of magnetic structures in the "standard solar flare model in 3D." This model matches the observations well, reproducing the apparently slipping flare loops, S-shaped erupting loops, and the evolution of flare ribbons. All of these processes are explained via 3D reconnection mechanisms resulting from the expansion of a torus-unstable flux rope. The AIA observations and the numerical model are complemented by radio observations showing a noise storm in the metric range. Dm-drifting pulsation structures occurring during the eruption indicate plasmoid ejection and enhancement of the reconnection rate. The bursty nature of radio emission shows that the slipping reconnection is still intermittent, although it is observed to persist for more than an hour. Title: Proper horizontal photospheric flows in a filament channel Authors: Schmieder, B.; Roudier, T.; Mein, N.; Mein, P.; Malherbe, J. M.; Chandra, R. Bibcode: 2014A&A...564A.104S Altcode: Context. An extended filament in the central part of the active region NOAA 11106 crossed the central meridian on Sept. 17, 2010 in the southern hemisphere. It has been observed in Hα with the THEMIS telescope in the Canary Islands and in 304 Å with the EUV imager (AIA) onboard the Solar Dynamic Observatory (SDO). Counterstreaming along the Hα threads and bright moving blobs (jets) along the 304 Å filament channel were observed during 10 h before the filament erupted at 17:03 UT.
Aims: The aim of the paper is to understand the coupling between magnetic field and convection in filament channels and relate the horizontal photospheric motions to the activity of the filament.
Methods: An analysis of the proper photospheric motions using SDO/HMI continuum images with the new version of the coherent structure tracking (CST) algorithm developed to track granules, as well as the large scale photospheric flows, was performed for three hours. Using corks, we derived the passive scalar points and produced a map of the cork distribution in the filament channel. Averaging the velocity vectors in the southern hemisphere in each latitude in steps of 3.5 arcsec, we defined a profile of the differential rotation.
Results: Supergranules are clearly identified in the filament channel. Diverging flows inside the supergranules are similar in and out of the filament channel. Converging flows corresponding to the accumulation of corks are identified well around the Hα filament feet and at the edges of the EUV filament channel. At these convergence points, the horizontal photospheric velocity may reach 1 km s-1, but with a mean velocity of 0.35 km s-1. In some locations, horizontal flows crossing the channel are detected, indicating eventually large scale vorticity.
Conclusions: The coupling between convection and magnetic field in the photosphere is relatively strong. The filament experienced the convection motions through its anchorage points with the photosphere, which are magnetized areas (ends, feet, lateral extensions of the EUV filament channel). From a large scale point-of-view, the differential rotation induced a shear of 0.1 km s-1 in the filament. From a small scale point-of-view, any convective motions favored the interaction of the parasitic polarities responsible for the anchorages of the filament to the photosphere with the surrounding network and may explain the activity of the filament.

Two movies are available in electronic form at http://www.aanda.org Title: Erratum: "Propagating Waves Transverse to the Magnetic Field in a Solar Prominence" (2013, ApJ, 777, 108) Authors: Schmieder, B.; Kucera, T. A.; Knizhnik, K.; Luna, M.; Lopez-Ariste, A.; Toot, D. Bibcode: 2014ApJ...781..129S Altcode: No abstract at ADS Title: Propagating waves transverse to the magnetic field in a solar prominence Authors: Kucera, Therese; Schmieder, Brigitte; Knizhnik, Kalman; Lopez-Ariste, Arturo; Luna, Manuel; Toot, David Bibcode: 2014IAUS..300..435K Altcode: We have observed a quiescent prominence with the Hinode Solar Optical Telescope (SOT) (Ca II and Hα lines), Sacramento Peak Dunn Solar Telescope using the Universal Birefringent Filter (DST/UBF, in Hα, Hβ and Sodium-D lines), THEMIS (Télescope Héliographique pour l Etude du Magnétisme et des Instabilités Solaires/MTR (Multi Raies) spectromagnetograph (He D3), and the Solar Dynamics Observatory Atmospheric Imaging Assembly (SDO/AIA) in EUV over a 4 hour period on 2012 October 10. The small fields of view of the SOT, DST, and MTR are centered on a large prominence footpoint extending towards the surface. This feature appears in the larger field of view of the AIA/304 Å filtergram as a large, quasi-vertical pillar with loops on each side. The THEMIS/MTR data indicate that the magnetic field in the pillar is essentially horizontal and the observations in the optical domain show a large number of horizontally aligned features in the pillar. The data are consistent with a model of cool prominence plasma trapped in the dips of horizontal field lines. The SOT and DST data show what appear to be moving wave pulses. These pulses, which include a Doppler signature, move vertically, perpendicular to the field direction, along quasi-vertical columns of horizontal threads in the pillar. The pulses have a velocity of propagation of about 10 km/s, a wavelength about 2000 km in the plane of the sky, and a period about 280 sec. We interpret these waves in terms of fast magnetosonic waves. Title: Magnetic flux emergence, flares, and coronal mass ejections Authors: Mandrini, Cristina H.; Schmieder, Brigitte; Cristiani, Germán; Demoulin, Pascal; Guo, Yang Bibcode: 2014cosp...40E1980M Altcode: We study the violent events occurring in the cluster of two active regions (ARs), NOAA numbers 11121 and 11123, observed in November 2010 with instruments onboard the Solar Dynamics Observatory and from Earth. Within one day the total magnetic flux increased by 70 per cent with the emergence of new groups of bipoles in AR 11123. These emergences led to a very complex magnetic configuration in which around ten solar flares, some of them accompanied by coronal mass ejections (CMEs), occurred. A magnetic-field topology somputation indicates the presence of null points, associated separatrices and quasi-separatrix layers (QSLs) where magnetic reconnection is prone to occur. Based on this analysis, we propose a scenario to explain the origin of a low-energy event preceding a filament eruption, which is accompanied by a two-ribbon flare and CME, and a consecutive confined flare in AR 11123. The results of our topology computation can also explain the locations of flare ribbons in two other events, one preceding and one following the ones just mentioned. Title: Dynamics of a prominence observed in Mg II lines by IRIS Authors: Schmieder, Brigitte; Mein, Pierre; Dalmasse, Kévin; Tian, Hui; Kucera, Therese; Lopez-Ariste, Arturo Bibcode: 2014cosp...40E2927S Altcode: In September 2013 several prominences were observed with the IRIS spectrograph during a 60 day-long international program. We will present one set of observations obtained using multiple instruments on September 24. SDO/AIA and IRIS slit jaws provided images of the prominence corresponding to different physical conditions of the transition region between the cool plasma and the corona. The vector magnetic field was derived from THEMIS (Tenerife) observations using the He D3 depolarisation due to the magnetic field. The inversion code (CPA) takes into account the Hanle and the Zeeman effects. Movies from SDO/AIA in 304 A and Hinode/SOT in Ca II show the dynamics of the fine structures in the plane of the sky. From Mg II and Si IV line spectra observed by IRIS and H-alpha observed by the Multi-channel subtractive spectrograph (MSDP) in the Meudon solar tower we derived the Dopplershifts of the fine structures. The profiles of the Mg II lines are narrow (FHWM =0.15 A) and not reversed, contrary to the predictions of the theoretical models (Paletou et al 1993). We could resolve the velocity of several structures along the LOS with Dopplershifts as high as 60 km/s. Title: Electric current variations and 3D magnetic configuration of coronal jets Authors: Schmieder, Brigitte; Harra, Louise K.; Aulanier, Guillaume; Guo, Yang; Demoulin, Pascal; Moreno-Insertis, Fernando, , Prof Bibcode: 2014cosp...40E2928S Altcode: Coronal jets (EUV) were observed by SDO/AIA on September 17, 2010. HMI and THEMIS measured the vector magnetic field from which we derived the magnetic flux, the phostospheric velocity and the vertical electric current. The magnetic configuration was computed with a non linear force-free approach. The phostospheric current pattern of the recurrent jets were associated with the quasi-separatrix layers deduced from the magnetic extrapolation. The large twisted near-by Eiffel-tower-shape jet was also caused by reconnection in current layers containing a null point. This jet cannot be classified precisely within either the quiescent or the blowout jet types. We will show the importance of the existence of bald patches in the low atmosphere Title: A confined flare above filaments Authors: Dalmasse, K.; Chandra, R.; Schmieder, B.; Aulanier, G. Bibcode: 2014IAUS..300..227D Altcode: 2013arXiv1310.0667D We present the dynamics of two filaments and a C-class flare observed in NOAA 11589 on 2012 October 16. We used the multi-wavelength high-resolution data from SDO, as well as THEMIS and ARIES ground-based observations. The observations show that the filaments are progressively converging towards each other without merging. We find that the filaments have opposite chirality which may have prevented them from merging. On October 16, a C3.3 class flare occurred without the eruption of the filaments. According to the standard solar flare model, after the reconnection, post-flare loops form below the erupting filaments whether the eruption fails or not. However, the observations show the formation of post-flare loops above the filaments, which is not consistent with the standard flare model. We analyze the topology of the active region's magnetic field by computing the quasi-separatrix layers (QSLs) using a linear force-free field extrapolation. We find a good agreement between the photospheric footprints of the QSLs and the flare ribbons. We discuss how slipping or slip-running reconnection at the QSLs may explain the observed dynamics. Title: Einar Tandberg-Hanssen Authors: Schmieder, Brigitte; Pecker, Jean-Claude; Gary, Allen; Wu, S. T.; Moore, Ronald; Biesmann, Else Bibcode: 2014IAUS..300....4S Altcode: I would like to report first on the scientific career of Einar Tandberg-Hanssen: how he became a Solar Physicist particularly interested in prominences. In the second part of my talk I will show what he brought to the French community from the science perspective. Title: Clarifying some issues on the geoeffectiveness of limb halo CMEs Authors: Cid, Consuelo; Cremades, Hebe; Aran, Angels; Mandrini, Cristina; Sanahuja, Blai; Schmieder, Brigitte; Menvielle, Michel; Rodriguez, Luciano; Saiz, Elena; Cerrato, Yolanda; Dasso, Sergio; Jacobs, Carla; Lathuillere, Chantal; Zhukov, Andrei Bibcode: 2014IAUS..300..285C Altcode: A recent study by Cid et al. (2012) showed that full halo coronal mass ejections (CMEs) coming from the limb can disturb the terrestrial environment. Although this result seems to rise some controversies with the well established theories, the fact is that the study encourages the scientific community to perform careful multidisciplinary analysis along the Sun-to-Earth chain to fully understand which are the solar triggers of terrestrial disturbances. This paper aims to clarify some of the polemical issues arisen by that paper. Title: Dynamics in the filament of september 17 2010 and in its channel Authors: Mein, Nicole; Mein, Pierre; Schmieder, Brigitte; Malherbe, Jean-Marie; Roudier, Thierry Bibcode: 2014IAUS..300..451M Altcode: Dynamics of a filament is investigated in Hα. Counterstreaming flows are observed along the filament. Photospheric horizontal motions have been computed by using a Coherent Structure Tracking algorithm in the filament environment. Title: Proper horizontal photospheric flows below an eruptive filament Authors: Schmieder, Brigitte; Mein, Pierre; Mein, Nicole; Roudier, Thierry; Chandra, Ramseh Bibcode: 2014cosp...40E2926S Altcode: An analysis of the proper motions using SDO/HMI continuum images with the new version of the coherent structure tracking (CST) algorithm developed to track the granules as well as the large scale photospheric flows, was perfomed during three hours in a region containing a large filament channel on September 17, 2010. Supergranules were idenfied in the filament channel. Diverging flows inside the supergranules are similar in and out the filament channel. Using corks, we derived the passive scalar points and produced maps of cork distribution. The anchorage structures with the photosphere (feet) of the filament are located in the areas of converging flows with accumulations of corks. Averaging the velocity vectors for each latitude we defined a profile of the differential rotation. We conclude that the coupling between the convection and magnetic field in the photosphere is relatively strong. The filament experienced the convection motions through its feet. On a large scale point-of-view the differential rotation induced a shear of 0.1 km/s in the filament. On a small scale point-of-view convection motions favored the interaction/cancellation of the parasitic polarities at the base of the feet with the surrounding network explaining the brightenings,/jets and the eruption that were observed in the EUV filament. Title: Nature of Prominences and their role in Space Weather Authors: Schmieder, Brigitte; Malherbe, Jean-Marie; Wu, S. T. Bibcode: 2014IAUS..300.....S Altcode: No abstract at ADS Title: Topological study of active region 11158 Authors: Zhao, Jie; Li, Hui; Pariat, Etienne; Schmieder, Brigitte; Guo, Yang; Wiegelmann, Thomas Bibcode: 2014IAUS..300..479Z Altcode: With the cylindrical equal area (CEA) projection data from the Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO), we reconstructed the three-dimensional (3D) magnetic fields in the corona, using a non-linear force-free field (NLFFF) extrapolation method every 12 minutes during five days, to calculate the squashing degree factor Q in the volume. The results show that this AR has an hyperbolic flux tube (HFT) configuration, a typical topology of quadrupole, which is stable even during the two large flares (M6.6 and X2.2 class flares). Title: Nonlinear MHD waves in a Prominence Foot: Observations and Models Authors: Ofman, Leon; Schmieder, Brigitte; Kucera, Therese; Knizhnik, Kalman Bibcode: 2014cosp...40E2338O Altcode: Recent high-resolution observations with Hinode/SOT in Ca II emission of a prominence on October 12, 2012 show highly dynamic small-scale motions in the prominence material. Observations in Hα and of Doppler shifts show similar propagating fluctuations. However the optically thick nature of the emission lines inhibits unique quantitative interpretation in terms of density. Nevertheless, we find evidence of nonlinear wave activity in the prominence foot by examining the relative magnitude of the fluctuation intensity (dI/I~ dn/n). The waves are evident as significant density fluctuations (dn/n~O(1)) with weak height dependence, and apparently travel upward from the chromosphere into the prominence material with quasi-periodic fluctuations on the order of 5 minutes, and wavelengths ~<2000 km. Doppler shift observations show the transverse displacement of the propagating waves. The magnetic field is measured with THEMIS and is found to be 5-14 G. For the typical prominence density the corresponding fast magnetosonic speed is ~20 km/s in qualitative agreement with the propagation speed of the detected wave. We use 2D and 3D MHD numerical models to reproduce the nonlinear magnetosonic waves with the typical parameters of the prominence guided by observations. We investigate the parameter range of the model that fits the observed properties of the waves in order confirm the identification of the wave nature of these observations. Title: Recurrent filament eruptions and associated CMEs Authors: Schmieder, Brigitte; Cremades, Hebe; Mandrini, Cristina; Démoulin, Pascal; Guo, Yang Bibcode: 2014IAUS..300..489S Altcode: We investigate the violent events in the cluster of two active regions (ARs), NOAA numbers 11121 and 11123, observed on 11 November 2010 by the Solar Dynamics Observatory (SDO). Within one day the magnetic field intensity increased by 70% with the emergence of new groups of bipoles in AR 11123, where three filaments are seen along the complex inversion line. The destabilization of the filaments led to flares and CMEs. The CMEs around 08:24 UT and 17:00 UT are directly related to the partial eruption of one filament in the new AR, as shown by a topology computation and analysis. The other CMEs on this day are due to either other ARs or to the destabilization of the global magnetic configuration of the two ARs. This conclusion can be only reached by using the three eyes of SOHO, STEREO and SDO. Title: Twisting solar coronal jet launched at the boundary of an active region Authors: Schmieder, B.; Guo, Y.; Moreno-Insertis, F.; Aulanier, G.; Yelles Chaouche, L.; Nishizuka, N.; Harra, L. K.; Thalmann, J. K.; Vargas Dominguez, S.; Liu, Y. Bibcode: 2013A&A...559A...1S Altcode: 2013arXiv1309.6514S
Aims: A broad jet was observed in a weak magnetic field area at the edge of active region NOAA 11106 that also produced other nearby recurring and narrow jets. The peculiar shape and magnetic environment of the broad jet raised the question of whether it was created by the same physical processes of previously studied jets with reconnection occurring high in the corona.
Methods: We carried out a multi-wavelength analysis using the EUV images from the Atmospheric Imaging Assembly (AIA) and magnetic fields from the Helioseismic and Magnetic Imager (HMI) both on-board the Solar Dynamics Observatory, which we coupled to a high-resolution, nonlinear force-free field extrapolation. Local correlation tracking was used to identify the photospheric motions that triggered the jet, and time-slices were extracted along and across the jet to unveil its complex nature. A topological analysis of the extrapolated field was performed and was related to the observed features.
Results: The jet consisted of many different threads that expanded in around 10 minutes to about 100 Mm in length, with the bright features in later threads moving faster than in the early ones, reaching a maximum speed of about 200 km s-1. Time-slice analysis revealed a striped pattern of dark and bright strands propagating along the jet, along with apparent damped oscillations across the jet. This is suggestive of a (un)twisting motion in the jet, possibly an Alfvén wave. Bald patches in field lines, low-altitude flux ropes, diverging flow patterns, and a null point were identified at the basis of the jet.
Conclusions: Unlike classical λ or Eiffel-tower-shaped jets that appear to be caused by reconnection in current sheets containing null points, reconnection in regions containing bald patches seems to be crucial in triggering the present jet. There is no observational evidence that the flux ropes detected in the topological analysis were actually being ejected themselves, as occurs in the violent phase of blowout jets; instead, the jet itself may have gained the twist of the flux rope(s) through reconnection. This event may represent a class of jets different from the classical quiescent or blowout jets, but to reach that conclusion, more observational and theoretical work is necessary. Title: Propagating Waves Transverse to the Magnetic Field in a Solar Prominence Authors: Schmieder, B.; Kucera, T. A.; Knizhnik, K.; Luna, M.; Lopez-Ariste, A.; Toot, D. Bibcode: 2013ApJ...777..108S Altcode: 2013arXiv1309.1568S We report an unusual set of observations of waves in a large prominence pillar that consist of pulses propagating perpendicular to the prominence magnetic field. We observe a huge quiescent prominence with the Solar Dynamics Observatory Atmospheric Imaging Assembly in EUV on 2012 October 10 and only a part of it, the pillar, which is a foot or barb of the prominence, with the Hinode Solar Optical Telescope (SOT; in Ca II and Hα lines), Sac Peak (in Hα, Hβ, and Na-D lines), and THEMIS ("Télescope Héliographique pour l' Etude du Magnétisme et des Instabilités Solaires") with the MTR (MulTi-Raies) spectropolarimeter (in He D3 line). The THEMIS/MTR data indicates that the magnetic field in the pillar is essentially horizontal and the observations in the optical domain show a large number of horizontally aligned features on a much smaller scale than the pillar as a whole. The data are consistent with a model of cool prominence plasma trapped in the dips of horizontal field lines. The SOT and Sac Peak data over the four hour observing period show vertical oscillations appearing as wave pulses. These pulses, which include a Doppler signature, move vertically, perpendicular to the field direction, along thin quasi-vertical columns in the much broader pillar. The pulses have a velocity of propagation of about 10 km s-1, a period of about 300 s, and a wavelength around 2000 km. We interpret these waves in terms of fast magnetosonic waves and discuss possible wave drivers. Title: Propagating Waves Transverse to the Magnetic Field in a Solar Prominence Authors: Kucera, Therese A.; Knizhnik, K.; Lopez Ariste, A.; Luna Bennasar, M.; Schmieder, B.; Toot, D. Bibcode: 2013SPD....4410403K Altcode: We have observed a quiescent prominence with the Hinode Solar Optical Telescope (SOT, in Ca II and H-alpha lines), Sacramento Peak Observatory (in H-alpha, H-beta and Sodium-D lines), and THEMIS/MTR (Télescope Héliographique pour l'Étude du Magnétisme et des Instabilités Solaires/MulTi Raies, providing vector magnetograms), and SDO/AIA (Solar Dynamics Observatory Atmospheric Imaging Assembly, in EUV) over a 4 hour period on 2012 October 10. The small fields of view of SOT, Sac Peak and THEMIS are centered on a large pillar-like prominence footpoint extending towards the surface. This feature appears in the larger field of view of the 304 Å band, as a large, quasi-vertical column with material flowing horizontally on each side. The THEMIS/MTR data indicate that the magnetic field in the pillar is essentially horizontal and the observations in the optical wavelengths show a large number of horizontally aligned features on a much smaller scale than the pillar as a whole. The data are consistent with a model of cool prominence plasma trapped in the dips of horizontal field lines. The SOT and Sac Peak data show what appear to be moving wave pulses. These pulses, which include a Doppler signature, move vertically, perpendicular to the field direction, along quasi-vertical columns. The pulses have a velocity of propagation of about 10 km/s, a period about 260 sec, and a wavelength around 2000 km. We interpret these waves in terms of fast magneto-sonic waves and discuss possible wave drivers. Title: Recurrent coronal jets induced by repetitively accumulated electric currents Authors: Guo, Y.; Démoulin, P.; Schmieder, B.; Ding, M. D.; Vargas Domínguez, S.; Liu, Y. Bibcode: 2013A&A...555A..19G Altcode: 2013arXiv1305.0902G Context. Jets of plasma are frequently observed in the solar corona. A self-similar recurrent behavior is observed in a fraction of them.
Aims: Jets are thought to be a consequence of magnetic reconnection; however, the physics involved is not fully understood. Therefore, we study some jet observations with unprecedented temporal and spatial resolutions.
Methods: The extreme-ultraviolet (EUV) jets were observed by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory (SDO). The Helioseismic and Magnetic Imager (HMI) on board SDO measured the vector magnetic field, from which we derive the magnetic flux evolution, the photospheric velocity field, and the vertical electric current evolution. The magnetic configuration before the jets is derived by the nonlinear force-free field extrapolation.
Results: Three EUV jets recurred in about one hour on 17 September 2010 in the following magnetic polarity of active region 11106. We derive that the jets are above a pair of parasitic magnetic bipoles that are continuously driven by photospheric diverging flows. The interaction drove the buildup of electric currents, which we observed as elongated patterns at the photospheric level. For the first time, the high temporal cadence of the HMI allows the evolution of such small currents to be followed. In the jet region, we found that the integrated absolute current peaks repetitively in phase with the 171 Å flux evolution. The current buildup and its decay are both fast, about ten minutes each, and the current maximum precedes the 171 Å also by about ten minutes. Then, the HMI temporal cadence is marginally fast enough to detect such changes.
Conclusions: The photospheric current pattern of the jets is found to be associated with the quasi-separatrix layers deduced from the magnetic extrapolation. From previous theoretical results, the observed diverging flows are expected to continuously build such currents. We conclude that the magnetic reconnection occurs periodically, in the current layer created between the emerging bipoles and the large-scale active region field. The periodic magnetic reconnection induced the observed recurrent coronal jets and the decrease of the vertical electric current magnitude.

Two movies are available in electronic form at http://www.aanda.org Title: Solar filament eruptions and their physical role in triggering coronal mass ejections Authors: Schmieder, B.; Démoulin, P.; Aulanier, G. Bibcode: 2013AdSpR..51.1967S Altcode: 2012arXiv1212.4014S Solar filament eruptions play a crucial role in triggering coronal mass ejections (CMEs). More than 80% of eruptions lead to a CME. This correlation has been studied extensively during the past solar cycles and the last long solar minimum. The statistics made on events occurring during the rising phase of the new solar cycle 24 is in agreement with this finding. Both filaments and CMEs have been related to twisted magnetic fields. Therefore, nearly all the MHD CME models include a twisted flux tube, called a flux rope. Either the flux rope is present long before the eruption, or it is built up by reconnection of a sheared arcade from the beginning of the eruption. Title: The geoeffectiveness of Halo CMEs far from central meridian Authors: Schmieder, Brigitte Bibcode: 2013EGUGA..15.1537S Altcode: Fast halo CMEs are considered as the most geoeffective solar events. When the halo CME comes with velocities higher than 1000 km/s and originating from the Western hemisphere close to the solar center, a large disturbance is expected at terrestrial environment. However, large disturbances have been also associated to halo CMEs from regions located far from central solar meridian, as Hallowing storm, related to CMEs from active regions farther than W80 and resulting a Dst index below -400 nT. In this work we have studied all halo CMEs of solar cycle 23, as observed by the Solar and Heliospheric Observatory (SOHO) mission, with solar source close to solar limb, from 60° up to 90° far from central meridian. For this task, we have analyzed not only solar atmosphere and the terrestrial surface, but every link in the Sun-Earth chain. The results of this work are useful, not only for understanding solar-terrestrial interaction, but also in order to establish the requirements of space weather models based on solar observations. Title: SDO/AIA Prominence physical conditions Authors: Schmieder, B.; Parenti, S.; Dudik, J.; Aulanier, G.; Heinzel, P.; Zapior, M.; Golub, L. Bibcode: 2013enss.confE..27S Altcode: SDO/AIA has carried out continuous observations of prominences in multiple wavelengths, with high spatial and temporal resolution. These data provide us an opportunity to understand the physical conditions and dynamics of prominences. The surprising brightness of prominences in some coronal lines has been well explained by the presence of transition region lines in the bandpass of the filters (171 A, 131 A), a result that leads us to revise our model of the transition region of prominences and to consider a relatively dense transition region in some prominence evolutionary phases or in some viewing orientation. An additional aspect of prominence dynamics will be presented with a new quasi-static MHD model proposed for bubbles and plumes. We propose an alternative to the interpretation that thermal instabilities are responsible for the formation of bubbles. The bubbles are found to correspond to magnetic separatrices formed by emerging magnetic field close to prominence footpoints. Title: The standard flare model in three dimensions. II. Upper limit on solar flare energy Authors: Aulanier, G.; Démoulin, P.; Schrijver, C. J.; Janvier, M.; Pariat, E.; Schmieder, B. Bibcode: 2013A&A...549A..66A Altcode: 2012arXiv1212.2086A Context. Solar flares strongly affect the Sun's atmosphere as well as the Earth's environment. Quantifying the maximum possible energy of solar flares of the present-day Sun, if any, is thus a key question in heliophysics.
Aims: The largest solar flares observed over the past few decades have reached energies of a few times 1032 erg, possibly up to 1033 erg. Flares in active Sun-like stars reach up to about 1036 erg. In the absence of direct observations of solar flares within this range, complementary methods of investigation are needed to assess the probability of solar flares beyond those in the observational record.
Methods: Using historical reports for sunspot and solar active region properties in the photosphere, we scaled to observed solar values a realistic dimensionless 3D MHD simulation for eruptive flares, which originate from a highly sheared bipole. This enabled us to calculate the magnetic fluxes and flare energies in the model in a wide paramater space.
Results: Firstly, commonly observed solar conditions lead to modeled magnetic fluxes and flare energies that are comparable to those estimated from observations. Secondly, we evaluate from observations that 30% of the area of sunspot groups are typically involved in flares. This is related to the strong fragmentation of these groups, which naturally results from sub-photospheric convection. When the model is scaled to 30% of the area of the largest sunspot group ever reported, with its peak magnetic field being set to the strongest value ever measured in a sunspot, it produces a flare with a maximum energy of ~6 × 1033 erg.
Conclusions: The results of the model suggest that the Sun is able to produce flares up to about six times as energetic in total solar irradiance fluence as the strongest directly observed flare of Nov. 4, 2003. Sunspot groups larger than historically reported would yield superflares for spot pairs that would exceed tens of degrees in extent. We thus conjecture that superflare-productive Sun-like stars should have a much stronger dynamo than in the Sun. Title: A Multi-spacecraft View of a Giant Filament Eruption during 2009 September 26/27 Authors: Gosain, Sanjay; Schmieder, Brigitte; Artzner, Guy; Bogachev, Sergei; Török, Tibor Bibcode: 2012ApJ...761...25G Altcode: 2012arXiv1210.6686G We analyze multi-spacecraft observations of a giant filament eruption that occurred during 2009 September 26 and 27. The filament eruption was associated with a relatively slow coronal mass ejection. The filament consisted of a large and a small part, and both parts erupted nearly simultaneously. Here we focus on the eruption associated with the larger part of the filament. The STEREO satellites were separated by about 117° during this event, so we additionally used SoHO/EIT and CORONAS/TESIS observations as a third eye (Earth view) to aid our measurements. We measure the plane-of-sky trajectory of the filament as seen from STEREO-A and TESIS viewpoints. Using a simple trigonometric relation, we then use these measurements to estimate the true direction of propagation of the filament which allows us to derive the true R/R ⊙-time profile of the filament apex. Furthermore, we develop a new tomographic method that can potentially provide a more robust three-dimensional (3D) reconstruction by exploiting multiple simultaneous views. We apply this method also to investigate the 3D evolution of the top part of filament. We expect this method to be useful when SDO and STEREO observations are combined. We then analyze the kinematics of the eruptive filament during its rapid acceleration phase by fitting different functional forms to the height-time data derived from the two methods. We find that for both methods an exponential function fits the rise profile of the filament slightly better than parabolic or cubic functions. Finally, we confront these results with the predictions of theoretical eruption models. Title: Magnetic Topology of Bubbles in Quiescent Prominences Authors: Dudík, J.; Aulanier, G.; Schmieder, B.; Zapiór, M.; Heinzel, P. Bibcode: 2012ApJ...761....9D Altcode: We study a polar-crown prominence with a bubble and its plume observed in several coronal filters by the SDO/AIA and in Hα by the MSDP spectrograph in Białków (Poland) to address the following questions: what is the brightness of prominence bubbles in EUV with respect to the corona outside of the prominence and the prominence coronal cavity? What is the geometry and topology of the magnetic field in the bubble? What is the nature of the vertical threads seen within prominences? We find that the brightness of the bubble and plume is lower than the brightness of the corona outside of the prominence, and is similar to that of the coronal cavity. We constructed linear force-free models of prominences with bubbles, where the flux rope is perturbed by inclusion of parasitic bipoles. The arcade field lines of the bipole create the bubble, which is thus devoid of magnetic dips. Shearing the bipole or adding a second one can lead to cusp-shaped prominences with bubbles similar to the observed ones. The bubbles have complex magnetic topology, with a pair of coronal magnetic null points linked by a separator outlining the boundary between the bubble and the prominence body. We conjecture that plume formation involves magnetic reconnection at the separator. Depending on the viewing angle, the prominence can appear either anvil-shaped with predominantly horizontal structures, or cusp-shaped with predominantly vertical structuring. The latter is an artifact of the alignment of magnetic dips with respect to the prominence axis and the line of sight. Title: Study of an Extended EUV Filament Using SoHO/SUMER Observations of the Hydrogen Lyman Lines. II. Lyman α Line Observed During a Multi-wavelength Campaign Authors: Schwartz, P.; Schmieder, B.; Heinzel, P.; Kotrč, P. Bibcode: 2012SoPh..281..707S Altcode: 2012SoPh..tmp..201S A filament and its channel close to the solar disk were observed in the complete hydrogen Lyman spectrum, and in several EUV lines by the SUMER (Solar Ultraviolet Measurement of Emitted Radiation) and CDS (Coronal Diagnostic Spectrometer) spectrographs on the SoHO satellite, and in Hα by ground-based telescopes during a multi-instrument campaign in May 2005. It was a good opportunity to get an overview of the volume and the density of the cold plasma in the filament channel; these are essential parameters for coronal mass ejections. We found that the width of the filament depends on the wavelength in which the filament is observed (around 15 arcsec in Hα, 30 arcsec in Lα, and 60 arcsec in EUV). In Lα the filament is wider than in Hα because cool plasma, not visible in Hα, is optically thick at the Lα line center, and its presence blocks the coronal emission. We have derived physical plasma properties of this filament fitting the Lyman spectra and Hα profiles by using a 1D isobaric NLTE model. The vertical temperature profile of the filament slab is flat (T≈7000 K) with an increase to ≈ 20 000 K at the top and the bottom of the slab. From an analysis of the Lα and Hα source functions we have concluded that these lines are formed over the whole filament slab. We have estimated the geometrical filling factor in the filament channel. Its low value indicates the presence of multi-threads. Title: Can a halo CME from the limb be geoeffective? Authors: Cid, C.; Cremades, H.; Aran, A.; Mandrini, C.; Sanahuja, B.; Schmieder, B.; Menvielle, M.; Rodriguez, L.; Saiz, E.; Cerrato, Y.; Dasso, S.; Jacobs, C.; Lathuillere, C.; Zhukov, A. Bibcode: 2012JGRA..11711102C Altcode: The probability for a halo coronal mass ejection (CME) to be geoeffective is assumed to be higher the closer the CME launch site is located to the solar central meridian. However, events far from the central meridian may produce severe geomagnetic storms, like the case in April 2000. In this work, we study the possible geoeffectiveness of full halo CMEs with the source region situated at solar limb. For this task, we select all limb full halo (LFH) CMEs that occurred during solar cycle 23, and we search for signatures of geoeffectiveness between 1 and 5 days after the first appearance of each CME in the LASCO C2 field of view. When signatures of geomagnetic activity are observed in the selected time window, interplanetary data are carefully analyzed in order to look for the cause of the geomagnetic disturbance. Finally, a possible association between geoeffective interplanetary signatures and every LFH CME in solar cycle 23 is checked in order to decide on the CME's geoeffectiveness. After a detailed analysis of solar, interplanetary, and geomagnetic data, we conclude that of the 25 investigated events, there are only four geoeffective LFH CMEs, all coming from the west limb. The geoeffectiveness of these events seems to be moderate, turning to intense in two of them as a result of cumulative effects from previous mass ejections. We conclude that ejections from solar locations close to the west limb should be considered in space weather, at least as sources of moderate disturbances. Title: Velocity Vector, Ionization Degree, and Temperature of Prominence Fine Structures Observed by Hinode/SOT Authors: Schmieder, B.; Mein, P.; Chandra, R.; Molodij, G.; Heinzel, P.; Berlicki, A.; Schwartz, P.; Fárník, F.; Labrosse, N.; Anzer, U.; Watanabe, T. Bibcode: 2012ASPC..454..107S Altcode: Prominences have been successfully observed by Hinode in April 2007 exhibiting a strong dynamics of their fine structures. The dynamics of a prominence is a challenge to understand the formation of cool prominence plasma embedded in the hot corona. Combining simultaneous observations obtained in Hα with Hinode/SOT and the MSDP spectrograph operating at the Meudon solar tower, velocity vectors have been derived. The Doppler-shifts of bright threads are of the same order as the velocities measured perpendicular to the line of sight. This suggests that the vertical structures of the prominence could be a pile up of dips in magnetic field lines viewed in 3D. Using Hα, Hinode/XRT and TRACE data, the hydrogen ionization degree has been determined to be 0.5-0.8, and the optical thickness in Hα between 0.2 and 1.3. The Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode produced images of the prominence in 11 selected lines with formation temperatures between log(T) = 4.7 and log(T) = 6.1. We comment on the absorption, emissivity blocking and emission involved for interpreting the different structures of the prominence in terms of the temperature and density. Title: Reconstruction of 3D Coronal Magnetic Structures from THEMIS/MTR and Hinode/SOT Vector Maps Authors: Schmieder, B.; Guo, Y.; Aulanier, G.; Démoulin, P.; Török, T.; Bommier, V.; Wiegelmann, T.; Gosain, S. Bibcode: 2012ASPC..454..363S Altcode: Coordinated campaigns using THEMIS, Hinode, and other instruments have allowed us to study the magnetic fields of faculae, filaments, and active regions. In a first case, we modelled the 3D magnetic field in a flaring active region with a nonlinear force-free field extrapolation, using magnetic vectors observed by THEMIS/MTR as boundary condition. In order to construct a consistent bottom boundary for the model, we first removed the 180 degree ambiguity of the transverse fields and minimized the force and torque in the observed vector fields. We found a twisted magnetic flux rope, well aligned with the polarity inversion line and a part of an Hα filament, and located where a large flare is initiated about two hours later. In a second case, Hinode/SOT allowed us to detect fine flux concentrations in faculae, while MTR provided us with magnetic information at different levels in the atmosphere. The polarimetry analysis of the MTR and SOT data gave consistent results, using both UNNOFIT and MELANIE inversion codes. Title: Prominences observations with SDO/AIA Authors: Parenti, Susanna; Schmieder, Brigitte; Golub, Leon; Heinzel, Petr Bibcode: 2012cosp...39.1447P Altcode: 2012cosp.meet.1447P The Prominence-Corona-Transition-Region (PCTR) plays a key role in the thermal and pressure equilibrium of prominences. However, several open issues limit our knowledge of this important interface. Among them we find the thermal structure and the maximum temperature of its emitting plasma. This work is a new step toward resolving these issues. By noting that prominences may be observed in emission in the 171 and 131 SDO/AIA images, while they are seen in absorption in others (e.g. 193) we investigate the temperature content of these channels. Using the CHIANTI atomic database and previously derived prominence DEMs, we built synthetic spectra in these AIA channels to establish the main contributors. We find that the Fe IX line always dominates the 171 band, even in absence of a coronal plasma, while the 131 channel is dominated by Fe VIII. Our conclusion is that the PCTR reaches, at least, 4x 10^5 K. Title: On the Nature of Prominence Emission Observed by SDO/AIA Authors: Parenti, S.; Schmieder, B.; Heinzel, P.; Golub, L. Bibcode: 2012ApJ...754...66P Altcode: 2012arXiv1205.5460P The prominence-corona transition region (PCTR) plays a key role in the thermal and pressure equilibrium of solar prominences. Our knowledge of this interface is limited and several major issues remain open, including the thermal structure and, in particular, the maximum temperature of the detectable plasma. The high signal-to-noise ratio of images obtained by the Atmospheric Imaging Assembly (AIA) on NASA's Solar Dynamics Observatory clearly shows that prominences are often seen in emission in the 171 and 131 bands. We investigate the temperature sensitivity of these AIA bands for prominence observations, in order to infer the temperature content in an effort to explain the emission. Using the CHIANTI atomic database and previously determined prominence differential emission measure distributions, we build synthetic spectra to establish the main emission-line contributors in the AIA bands. We find that the Fe IX line always dominates the 171 band, even in the absence of plasma at >106 K temperatures, while the 131 band is dominated by Fe VIII. We conclude that the PCTR has sufficient plasma emitting at >4 × 105 K to be detected by AIA. Title: Can bubbles in quiescent prominences be purely magnetic phenomena? Authors: Dudik, Jaroslav; Schmieder, Brigitte; Aulanier, Guillaume; Zapior, Maciej; Heinzel, Petr Bibcode: 2012cosp...39..486D Altcode: 2012cosp.meet..486D We present a model of the magnetic field constituting quiescent prominences. The model assumes a linear force-free field with a weakly twisted flux-tube in an OX/OF topology perturbed by presence of parasitic polarities within the filament channel. The parasitic polarities locally create the cusp-shaped prominences with bubbles exactly as those observed by the SDO/AIA and Bialkow Observatory. We find that the observations are best reproduced if the parasitic bipoles are sheared with respect to the main inversion line. We show that the bubbles are in fact constituted by the arcade-like field lines, as opposed to that of the prominence, which is created by magnetic dips. A pair of null points is always associated with the parasitic bipole. These null points are connected by a separator passing through the prominence bubble. We show how the presence of an additional parasitic bipole moves the separator to the boundary between the bubble and the rest of the prominence, producing a topology favorable for reconnection and possibly for the formation of plumes. Title: Prominence fine-structure dynamics as inferred from 2D non-LTE models Authors: Gunar, Stanislav; Schmieder, Brigitte; Mein, Pierre; Heinzel, Petr Bibcode: 2012cosp...39..683G Altcode: 2012cosp.meet..683G 2D multi-thread prominence fine structure models are able to produce synthetic Lyman spectra in very good agreement with spectral observations by SOHO/SUMER including the spectral line asymmetries. The synthetic differential emission measure curves derived from these models are also in a good agreement with observations. Now we show that these models are also able to produce synthetic H-alpha line profiles in very good agreement with observations which allows us to analyze not only the physical parameters of the prominence fine-structure plasma but also some aspects of its dynamical behaviour. We compare the synthetic H-alpha spectra with the observed spectra of the April 26, 2007 prominence using three statistical parameters: the line integrated intensity, the line full-width at the half-maximum (FWHM), and the Doppler velocity derived from shifts of the line profiles. This statistical analysis allows us to conclude that the overall statistical distribution of the LOS velocities in the April 26, 2007 prominence at the time of the observations was below +/-15 km/s and in the prominence core was close to +/-10 km/s. In combination with the analysis of the Lyman spectra we determine several physical parameters of the observed prominence fine structures which show that the April 26, 2007 prominence was relatively less massive. We are also able to put some constrains on the prominence core temperature that might be relatively low, reaching values below 6000 K. Title: Impulsive Eruptive Flare on 23 October, 2003, from NOAA AR 10484 Authors: Chandra, Ramesh; Schmieder, Brigitte; Cristiani, Germán.; Mandrini, Cristina H.; Joshi, Bhuwan; Srivastava, Abhishek K.; Uddin, Wahab Bibcode: 2012cosp...39..302C Altcode: 2012cosp.meet..302C No abstract at ADS Title: Solar filament eruptions and their physical role in triggering CMEs Authors: Schmieder, Brigitte Bibcode: 2012cosp...39.1723S Altcode: 2012cosp.meet.1723S CMEs are due to physical phenomena that drive both, eruptions and flares in active regions. Eruptions/CMEs must be driven from initially force-free current-carrying magnetic field. Twisted flux ropes, sigmoids, current lanes and pattern in photospheric current maps show a clear evidence of currents parallel to the magnetic field. Eruptions occur starting from equilibriums , which have reached some instability threshold. Boundary motions related to magnetic flux emergence and shearing favour the increase of coronal currents leading to the large flares. On the other hand, during the rising solar cycle phase, filament eruptions are characterized by a gradual (slow) and weak acceleration and therefore not accompanied by significant flaring. The gradual acceleration is due to a rather shallow profile of the overlying magnetic field. As the solar cycle is progressing, the magnetic field increases and stronger flares may occur due to the diffusion of the magnetic field, then reducing the magnetic tension. The basic driving mechanism is the torus instability or loss of equilibrium in both types of eruptions. Title: The standard flare model in three dimensions. I. Strong-to-weak shear transition in post-flare loops Authors: Aulanier, G.; Janvier, M.; Schmieder, B. Bibcode: 2012A&A...543A.110A Altcode: Context. The standard CSHKP model for eruptive flares is two-dimensional. Yet observational interpretations of photospheric currents in pre-eruptive sigmoids, shear in post-flare loops, and relative positioning and shapes of flare ribbons, all together require three-dimensional extensions to the model.
Aims: We focus on the strong-to-weak shear transition in post-flare loops, and on the time-evolution of the geometry of photospheric electric currents, which occur during the development of eruptive flares. The objective is to understand the three-dimensional physical processes, which cause them, and to know how much the post-flare and the pre-eruptive distributions of shear depend on each other.
Methods: The strong-to-weak shear transition in post-flare loops is identified and quantified in a flare observed by STEREO, as well as in a magnetohydrodynamic simulation of CME initiation performed with the OHM code. In both approaches, the magnetic shear is evaluated with field line footpoints. In the simulation, the shear is also estimated from ratios between magnetic field components.
Results: The modeled strong-to-weak shear transition in post-flare loops comes from two effects. Firstly, a reconnection-driven transfer of the differential magnetic shear, from the pre- to the post-eruptive configuration. Secondly, a vertical straightening of the inner legs of the CME, which induces an outer shear weakening. The model also predicts the occurrence of narrow electric current layers inside J-shaped flare ribbons, which are dominated by direct currents. Finally, the simulation naturally accounts for energetics and time-scales for weak and strong flares, when typical scalings for young and decaying solar active regions are applied.
Conclusions: The results provide three-dimensional extensions to the standard flare model. These extensions involve MHD processes that should be tested with observations. Title: Topology analysis of emerging bipole clusters producing violent solar events observed by SDO Authors: Schmieder, Brigitte; Demoulin, Pascal; Mandrini, Cristina H.; Guo, Yang Bibcode: 2012cosp...39.1724S Altcode: 2012cosp.meet.1724S During the rising phase of Solar Cycle 24, tremendous magnetic solar activity occurs on the Sun with fast and compact emergence of magnetic flux leading to burts of flares (C to M and even X class) . We have investigated the violent events occuring in the cluster of two active regions AR 11121 and AR11123 observed in November by SDO. In less than two days the magnetic field increases by a factor of 10 with the emergence of groups of bipoles. A topology analysis demonstrates the formation of multiple separatrices and quasi-separatrix layers explaining possible mechanisms for destabilization of the magnetic structures such as filaments and coronal loops. Title: Slip-running reconnection and evolution of shear in post-flare loops Authors: Janvier, Miho; Schmieder, Brigitte; Pariat, Etienne; Aulanier, Guillaume Bibcode: 2012cosp...39..816J Altcode: 2012cosp.meet..816J We analyze the physical mechanisms of an eruptive flare via 3D magnetohydrodynamic simulations of a flux rope. We focus on the relaxation process associated with the reconnection of magnetic field lines driven by the free expansion of the magnetic field. First, the origin of the shearing of post-flare magnetic loops is investigated in relation to the pre-flare geometry of the magnetic field. Indeed, space-borne satellites can observe the temporal changes of post-flare structures that are important observational manifestations of the solar flare phenomenon. As such, understanding the evolution of post-flare loops can reveal the characteristics of the pre-flare magnetic field. Here, we introduce different proxies to quantify the shear angle. We show that strong geometrical similarities exist between the initial magnetic field and the post-flare loops. Analysis of the eruption dynamics shows that magnetic reconnection at the origin of the post-flare field lines forms less and less sheared magnetic loops on top of one another. We confirm this tendency by direct measurements of the shear angle seen in flare events such as that of May 9, 2011 recorded by STEREO-B/EUVI. Our results also highlight that vertical stretching of the magnetic field lines may play a role in the shear angle evolution of post-flare loops. The analysis of the eruptive flare evolution is followed by a detailed investigation of the flux rope growth and of the post-flare loops formation due to coronal slip-running reconnection. For that, we study the dynamics of different regions around two ribbons of opposite current. We find that these ribbons correspond to quasi-separatrix layers (QSLs), associated with J-shaped pre-flare magnetic field lines, reconnected S-shaped flux rope lines and post-flare loops. Simulations with very small time steps are required so as to show the detailed time evolution of those QSLs as well as the time variations of the slip-running velocities. Our results provide a fully 3D extension of the standard 2D flare model. Title: Dynamics of quiescent prominence fine structures analyzed by 2D non-LTE modelling of the Hα line Authors: Gunár, S.; Mein, P.; Schmieder, B.; Heinzel, P.; Mein, N. Bibcode: 2012A&A...543A..93G Altcode:
Aims: We analyze the dynamics of the prominence fine structures of a quiescent prominence observed on April 26, 2007 during a coordinated campaign of several spaceborne and ground-based instruments. We use Lyman spectra observed by SOHO/SUMER and the Hα line spectra obtained by MSDP spectrograph working at the Meudon Solar Tower.
Methods: We employ the 2D multi-thread prominence fine-structure modelling that includes randomly distributed line-of-sight (LOS) velocities of individual threads to derive models producing synthetic Lyman lines in good agreement with the SOHO/SUMER observations. We then use these models to produce synthetic Hα line spectra that we compare with the observed spectra using three statistical parameters: the line integrated intensity, the line full-width at half-maximum (FWHM), and the Doppler velocity derived from shifts of the line profiles.
Results: We demonstrate that the 2D multi-thread models that produce synthetic Lyman spectra in agreement with observations also generate synthetic Hα spectra in good agreement with the observed ones. The statistical analysis of the FWHM and Doppler velocities of the synthetic Hα line profiles show that the overall LOS velocities in the April 26, 2007 prominence at the time of the observations were below 15 km s-1 and in the prominence core were close to 10 km s-1. In combination with the analysis of the Lyman spectra, we determine several physical parameters of the observed prominence fine-structures that show that the April 26, 2007 prominence had a relatively low-mass weakly magnetized structure. We are also able to impose some constraints on the prominence core temperature, which may be relatively low, with values below 6000 K.
Conclusions: The combination of 2D non-LTE prominence fine-structure modelling with the statistical analysis of the observed and synthetic Lyman and Hα spectra allows us to analyze the influence of the model input parameters and the velocity fields on the synthetic Hα line profiles, thus determine the overall dynamics of the observed prominence as well as the physical parameters of its plasma.

Appendix A is available in electronic form at http://www.aanda.org Title: Resistive magnetic flux emergence and formation of solar active regions Authors: Pariat, E.; Schmieder, B.; Masson, S.; Aulanier, G. Bibcode: 2012EAS....55..115P Altcode: Magnetic flux emergence as the mechanism leading to the formation of magnetized structures in the solar atmosphere plays a key role in the dynamic of the Sun. Observed as a whole, emerging flux regions show clear signs of twisted structure, bearing the magnetic free energy necessary to power active events. The high resolution observations of the recent solar observatories (e.g. Hinode, SDO) have revealed how intermittent the magnetic field appears and how various active events induced by flux emergence are. Magnetic field reconstructions methods show that the topology of the field in interspot regions presents a serpentine structure, i.e. field lines having successive U and Ω parts. Associated with the appearance of magnetic polarities, a tremendous number of brief small scale brightening are observed in different photospheric and chromospheric lines, e.g. Ellerman Bombs, along with small scale jet-like structures. These events are believed to be the observational signatures of the multiple magnetic reconnections which enable the magnetic field to emerge further up and magnetically structure the corona above active region. Meanwhile a world-wide effort to numerically model the emergence of magnetic field forming solar active region is been carried on. Using different types of physical paradigm - e.g. idealized magnetohydrodynamic model, advanced treatment of the physical equations, data-driven simulations - these numerical experiments highlight how electric currents can build-up during flux emergence, lead to reconnection and thus explain the formation of the different observed transients. Title: What are the physical mechanisms of eruptions and CMEs? Authors: Schmieder, Brigitte; Aulanier, Guillaume Bibcode: 2012AdSpR..49.1598S Altcode: CMEs are due to physical phenomena that drive both, eruptions and flares in active regions. Eruptions/CMEs must be driven from initially force-free current-carrying magnetic field. Twisted flux ropes, sigmoids, current lanes and pattern in photospheric current maps show a clear evidence of currents parallel to the magnetic field. Eruptions occur starting from equilibria which have reached some instability threshold. Revisiting several data sets of CME observations we identified different mechanisms leading to this unstable state from a force free field. Boundary motions related to magnetic flux emergence and shearing favor the increase of coronal currents leading to the large flares of November 2003. On the other hand, we demonstrated by numerical simulations that magnetic flux emergence is not a sufficient condition for eruptions. Filament eruptions are interpreted either by a torus instability for an event occurring during the minimum of solar activity either by the diffusion of the magnetic flux reducing the tension of the restraining arcade. We concluded that CME models (tether cutting, break out, loss of equilibrium models) are based on these basic mechanisms for the onset of CMEs. Title: Observations of Multiple Surges Associated with Magnetic Activities in AR 10484 on 2003 October 25 Authors: Uddin, Wahab; Schmieder, B.; Chandra, R.; Srivastava, Abhishek K.; Kumar, Pankaj; Bisht, S. Bibcode: 2012ApJ...752...70U Altcode: 2012arXiv1204.2053U We present a multi-wavelength study of recurrent surges observed in Hα, UV (Solar and Heliospheric Observatory (SOHO)/EIT), and Radio (Learmonth, Australia) from the super-active region NOAA 10484 on 2003 October 25. Several bright structures visible in Hα and UV corresponding to subflares are also observed at the base of each surge. Type III bursts are triggered and RHESSI X-ray sources are evident with surge activity. The major surge consists of bunches of ejective paths forming a fan-shaped region with an angular size of (≈65°) during its maximum phase. The ejection speed reaches up to ~200 km s-1. The SOHO/Michelson Doppler Imager magnetograms reveal that a large dipole emerges from the east side of the active region on 2003 October 18-20, a few days before the surges. On 2003 October 25, the major sunspots were surrounded by "moat regions" with moving magnetic features (MMFs). Parasitic fragmented positive polarities were pushed by the ambient dispersion motion of the MMFs and annihilated with negative polarities at the borders of the moat region of the following spot to produce flares and surges. A topology analysis of the global Sun using Potential Field Source Surface shows that the fan structures visible in the EIT 171 Å images follow magnetic field lines connecting the present active region to a preceding active region in the southeast. Radio observations of Type III bursts indicate that they are coincident with the surges, suggesting that magnetic reconnection is the driver mechanism. The magnetic energy released by the reconnection is transformed into plasma heating and provides the kinetic energy for the ejections. A lack of a radio signature in the high corona suggests that the surges are confined to follow the closed field lines in the fans. We conclude that these cool surges may have some local heating effects in the closed loops, but probably play a minor role in global coronal heating and the surge material does not escape to the solar wind. Title: Electric current density and related sigmoid in an active region Authors: Joulin, V.; Schmieder, B.; Aulanier, G.; Bommier, V. Bibcode: 2012EAS....55..143J Altcode: Using THEMIS vector magnetograms we measured vertical electric current density in the leading sunspot of NOAA 11127 active region during its disk passage. The current structures evolve versus time. MHD modelling allows us to explain the spiral pattern by torsion. We found observational visible counterparts in the SDO/AIA 335 A images. The field lines are visible as loops in the AIA images. When the torsion is increasing, a sigmoid is observed. In the present event observed on November 24th 2010, we find that reconnection is also necessary to explain their sigmoidal shape. Title: New perspectives on solar prominences Authors: Schmieder, B.; Aulanier, G. Bibcode: 2012EAS....55..149S Altcode: Recent observations of prominences obtained with high spatial and temporal resolution instruments, on board satellites (Hinode, SDO) as well as on the ground (SST) have provided very intriguing movies and open a new area for understanding the nature of prominences. The main topics are still debate: formation, dynamics, and characteristics of the plasma in the core and in the transition zone between the prominence and corona. We will review briefly the recent advances made in these topics, observationally as well as theoretically. Title: Magnetic Field Structures in a Facular Region Derived from THEMIS and Hinode Vector Magnetic Field Authors: Guo, Y.; Schmieder, B.; Bommier, V.; Mein, P. Bibcode: 2012ASPC..456...55G Altcode: In order to compare vector magnetic fields obtained by two spectral polarimeters (THEMIS/MTR and Hinode SOT/SP) and two inversion codes (UNNOFIT and MELANIE), we observed a facular region in the active region NOAA 10996 on 2008 May 23. We found that they give consistent results concerning the distributions of field strengths, azimuth and inclination angles. SOT/SP could resolve small magnetic polarities with sizes of 1'' to 2'', and detect convergence and divergence of the horizontal components of magnetic fields in the facular cells. These findings support the models suggesting the existence of flux tube bundles in faculae. With this model and multi spectral line observations, we could infer the relative formation heights of those spectral lines. Title: On the Visibility of Solar Prominences in SDO/AIA Channels Authors: Heinzel, P.; Schmieder, B.; Parenti, S.; Golub, L. Bibcode: 2012ASPC..456...75H Altcode: Prominences in EUV lines are observed as dark structures over the limb due absorption and emission blocking mechanisms. However, at 171 Å is observed emission in prominences with TRACE and SDO/AIA, and it is believed to be due to the prominence-corona transition region (PCTR) emitting in cool lines. To check this, we use the Differential Emission Measure (DEM) recently obtained for quiescent prominences using SOHO/SUMER spectra (Parenti and Vial 2007) and compute the synthetic spectra in selected AIA channels. We then compare 171 Å and 195 Å channels and derive conclusions concerning the PCTR emissivity, as well well as the absorption and blocking. The emission seen in the 171 Å channel can be used to better constrain prominence DEM curves. Title: On the Nature of Prominence Bubbles and Plumes Authors: Schmieder, B.; Zapior, M.; Heinzel, P.; Aulanier, G. Bibcode: 2012ASPC..456...77S Altcode: An example of bubble and related plume, using time series in selected SDO/AIA channels and co-temporal MSDP observations in the Hα line obtained at Wroclaw-Bialkow observatory on April 20, 2011 is presented. The formation of bubbles may be due to emerging arcades in the filament channel, below the prominence. After discussing on MHD modeling, we conclude that bubbles and plumes are parts of the corona observed through gaps/windows in the prominence. Title: Temperature Diagnostic of a Brightening Observed by Hinode/XRT Authors: Dudík, J.; Reeves, K. K.; Schmieder, B.; Dzifčáková, E.; Golub, L. Bibcode: 2012ASPC..456..137D Altcode: We analyze the temperature distribution of the active region brightening observed by HINODE/XRT. The temperature structure is derived using various filter-ratio techniques and DEM analysis. The results are compared and it is found that the filter-ratio techniques are accurate only for relatively narrow DEMs. Title: Evolution of Hard X-Ray Sources and Ultraviolet Solar Flare Ribbons for a Confined Eruption of a Magnetic Flux Rope Authors: Guo, Y.; Ding, M. D.; Schmieder, B.; Démoulin, P.; Li, H. Bibcode: 2012ApJ...746...17G Altcode: 2011arXiv1111.1790G We study the magnetic field structures of hard X-ray (HXR) sources and flare ribbons of the M1.1 flare in active region NOAA 10767 on 2005 May 27. We have found in a nonlinear force-free field extrapolation over the same polarity inversion line, a small pre-eruptive magnetic flux rope located next to sheared magnetic arcades. RHESSI and the Transition Region and Coronal Explorer (TRACE) observed this confined flare in the X-ray bands and ultraviolet (UV) 1600 Å bands, respectively. In this event magnetic reconnection occurred at several locations. It first started at the location of the pre-eruptive flux rope. Then, the observations indicate that magnetic reconnection occurred between the pre-eruptive magnetic flux rope and the sheared magnetic arcades more than 10 minutes before the flare peak. This implies the formation of the larger flux rope, as observed with TRACE. Next, HXR sources appeared at the footpoints of this larger flux rope at the peak of the flare. The associated high-energy particles may have been accelerated below the flux rope in or around a reconnection region. Still, the close spatial association between the HXR sources and the flux rope footpoints favors an acceleration within the flux rope. Finally, a topological analysis of a large solar region, including active regions NOAA 10766 and 10767, shows the existence of large-scale Quasi-Separatrix Layers (QSLs) before the eruption of the flux rope. No enhanced emission was found at these QSLs during the flare, but the UV flare ribbons stopped at the border of the closest large-scale QSL. Title: Multi-wavelength observations to understand the solar magnetic activity and its feedback on the interplanetary medium Authors: Molodij, G.; Schmieder, B.; Bommier, V. Bibcode: 2012mfu3.conf...93M Altcode: No abstract at ADS Title: A filament supported by different magnetic field configurations Authors: Guo, Y.; Schmieder, B.; Démoulin, P.; Wiegelmann, T.; Aulanier, G.; Török, T.; Bommier, V. Bibcode: 2011IAUS..273..328G Altcode: A nonlinear force-free magnetic field extrapolation of vector magnetogram data obtained by THEMIS/MTR on 2005 May 27 suggests the simultaneous existence of different magnetic configurations within one active region filament: one part of the filament is supported by field line dips within a flux rope, while the other part is located in dips within an arcade structure. Although the axial field chirality (dextral) and the magnetic helicity (negative) are the same along the whole filament, the chiralities of the filament barbs at different sections are opposite, i.e., right-bearing in the flux rope part and left-bearing in the arcade part. This argues against past suggestions that different barb chiralities imply different signs of helicity of the underlying magnetic field. This new finding about the chirality of filaments will be useful to associate eruptive filaments and magnetic cloud using the helicity parameter in the Space Weather Science. Title: Solar activity due to magnetic complexity of active regions Authors: Schmieder, Brigitte; Mandrini, Cristina; Chandra, Ramesh; Démoulin, Pascal; Török, Tibor; Pariat, Etienne; Uddin, Wahab Bibcode: 2011IAUS..273..164S Altcode: Active regions (ARs), involved in the Halloween events during October-November 2003, were the source of unusual activity during the following solar rotation. The flares on 18-20 November 2003 that occur in the AR NOAA10501 were accompanied by coronal mass ejections associated to some particularly geoeffective magnetic clouds.

Our analysis of the magnetic flux and helicity injection revealed that a new emerging bipole and consequent shearing motions continuously energized the region during its disk passage. The stored energy was eventually released through the interaction of the various systems of magnetic loops by several magnetic reconnection events. Active events on November 18 (filament eruptions and CMEs) were originated by shearing motions along a section of the filament channel that injected magnetic helicity with sign opposite to that of the AR. Two homologous flares, that occurred on November 20, were apparently triggered by different mechanisms as inferred from the flare ribbons evolution (filament eruption and CMEs). We studied in detail the behaviour of two North-South oriented filaments on November 20 2003. They merged and split following a process suggestive of `sling-shot' reconnection between two coronal flux ropes. We successfully tested this scenario in a 3D MHD simulation that is presented in this paper. Title: Vector magnetic field and vector current density in and around the δ-spot NOAA 10808† Authors: Bommier, Véronique; Landi Degl'Innocenti, Egidio; Schmieder, Brigitte; Gelly, Bernard Bibcode: 2011IAUS..273..338B Altcode: The context is that of the so-called ``fundamental ambiguity'' (also azimuth ambiguity, or 180° ambiguity) in magnetic field vector measurements: two field vectors symmetrical with respect to the line-of-sight have the same polarimetric signature, so that they cannot be discriminated. We propose a method to solve this ambiguity by applying the ``simulated annealing'' algorithm to the minimization of the field divergence, added to the longitudinal current absolute value, the line-of-sight derivative of the magnetic field being inferred by the interpretation of the Zeeman effect observed by spectropolarimetry in two lines formed at different depths. We find that the line pair Fe I λ 6301.5 and Fe I λ 6302.5 is appropriate for this purpose. We treat the example case of the δ-spot of NOAA 10808 observed on 13 September 2005 between 14:25 and 15:25 UT with the THEMIS telescope. Besides the magnetic field resolved map, the electric current density vector map is also obtained. A strong horizontal current density flow is found surrounding each spot inside its penumbra, associated to a non-zero Lorentz force centripetal with respect to the spot center (i.e., oriented towards the spot center). The current wrapping direction is found to depend on the spot polarity: clockwise for the positive polarity, counterclockwise for the negative one. This analysis is made possible thanks to the UNNOFIT2 Milne-Eddington inversion code, where the usual theory is generalized to the case of a line (Fe I λ 6301.5) that is not a normal Zeeman triplet line (like Fe I λ 6302.5). Title: EUV lines observed with EIS/Hinode in a solar prominence Authors: Labrosse, N.; Schmieder, B.; Heinzel, P.; Watanabe, T. Bibcode: 2011A&A...531A..69L Altcode: 2011arXiv1105.1400L Context. During a multi-wavelength observation campaign with Hinode and ground-based instruments, a solar prominence was observed for three consecutive days as it crossed the western limb of the Sun in April 2007.
Aims: We report on observations obtained on 26 April 2007 using EIS (Extreme ultraviolet Imaging Spectrometer) on Hinode. They are analysed to provide a qualitative diagnostic of the plasma in different parts of the prominence.
Methods: After correcting for instrumental effects, the rasters at different wavelengths are presented. Several regions within the same prominence are identified for further analysis. Selected profiles for lines with formation temperatures between log (T) = 4.7 and log (T) = 6.3, as well as their integrated intensities, are given. The profiles of coronal, transition region, and He ii lines are discussed. We pay special attention to the He ii line, which is blended with coronal lines.
Results: Some quantitative results are obtained by analysing the line profiles. They confirm that depression in EUV lines can be interpreted in terms of two mechanisms: absorption of coronal radiation by the hydrogen and neutral helium resonance continua, and emissivity blocking. We present estimates of the He ii line integrated intensity in different parts of the prominence according to different scenarios for the relative contribution of absorption and emissivity blocking to the coronal lines blended with the He ii line. We estimate the contribution of the He ii 256.32 Å line to the He ii raster image to vary between ~44% and 70% of the raster's total intensity in the prominence according to the different models used to take into account the blending coronal lines. The inferred integrated intensities of the He ii 256 Å line are consistent with the theoretical intensities obtained with previous 1D non-LTE radiative transfer calculations, yielding a preliminary estimate of the central temperature of 8700 K, a central pressure of 0.33 dyn cm-2, and a column mass of 2.5 × 10-4 g cm-2. The corresponding theoretical hydrogen column density (1020 cm-2) is about two orders of magnitude higher than those inferred from the opacity estimates at 195 Å. The non-LTE calculations indicate that the He ii 256.32 Å line is essentially formed in the prominence-to-corona transition region by resonant scattering of the incident radiation.

The movie associated to Fig. 2 is available in electronic form at http://www.aanda.org Title: 2D radiative-magnetohydrostatic model of a prominence observed by Hinode, SoHO/SUMER and Meudon/MSDP Authors: Berlicki, A.; Gunar, S.; Heinzel, P.; Schmieder, B.; Schwartz, P. Bibcode: 2011A&A...530A.143B Altcode:
Aims: Prominences observed by Hinode show very dynamical and intriguing structures. To understand the mechanisms that are responsible for these moving structures, it is important to know the physical conditions that prevail in fine-structure threads. In the present work we analyse a quiescent prominence with fine structures, which exhibits dynamic behaviour, which was observed in the hydrogen Hα line with Hinode/SOT, Meudon/MSDP and Ondřejov/HSFA2, and simultaneously in hydrogen Lyman lines with SoHO/SUMER during a coordinated campaign. We derive the fine-structure physical parameters of this prominence and also address the questions of the role of the magnetic dips and of the interpretation of the flows.
Methods: We calibrate the SoHO/SUMER and Meudon/MSDP data and obtain the line profiles of the hydrogen Lyman series (Lβ to L6), the Ciii (977.03 Å) and Svi (933.40 Å), and Hα along the slit of SoHO/SUMER that crosses the Hinode/SOT prominence. We employ a complex 2D radiation-magnetohydrostatic (RMHS) modelling technique to properly interpret the observed spectral lines and derive the physical parameters of interest. The model was constrained not only with integrated intensities of the lines, but also with the hydrogen line profiles.
Results: The slit of SoHO/SUMER is crossing different prominence structures: threads and dark bubbles. Comparing the observed integrated intensities, the depressions of Hα bubbles are clearly identified in the Lyman, Ciii, and Svi lines. To fit the observations, we propose a new 2D model with the following parameters: T = 8000 K, pcen = 0.035 dyn cm-2, B = 5 Gauss, ne = 1010 cm-3, 40 threads each 1000 km wide, plasma β is 3.5 × 10-2.
Conclusions: The analysis of Ciii and Svi emission in dark Hα bubbles allows us to conclude that there is no excess of a hotter plasma in these bubbles. The new 2D model allows us to diagnose the orientation of the magnetic field versus the LOS. The 40 threads are integrated along the LOS. We demonstrate that integrated intensities alone are not sufficient to derive the realistic physical parameters of the prominence. The profiles of the Lyman lines and also those of the Hα line are necessary to constrain 2D RMHS models. The magnetic field in threads is horizontal, perpendicular to the LOS, and in the form of shallow dips. With this geometry the dynamics of fine structures in prominences could be interpreted by a shrinkage of the quasi-horizontal magnetic field lines and apparently is not caused by the quasi-vertical bulk flows of the plasma, as Hinode/SOT movies seemingly suggest. Title: Actors of the main activity in large complex centres during the 23 solar cycle maximum Authors: Schmieder, B.; Démoulin, P.; Pariat, E.; Török, T.; Molodij, G.; Mandrini, C. H.; Dasso, S.; Chandra, R.; Uddin, W.; Kumar, P.; Manoharan, P. K.; Venkatakrishnan, P.; Srivastava, N. Bibcode: 2011AdSpR..47.2081S Altcode: During the maximum of Solar Cycle 23, large active regions had a long life, spanning several solar rotations, and produced large numbers of X-class flares and CMEs, some of them associated to magnetic clouds (MCs). This is the case for the Halloween active regions in 2003. The most geoeffective MC of the cycle (Dst = -457) had its source during the disk passage of one of these active regions (NOAA 10501) on 18 November 2003. Such an activity was presumably due to continuous emerging magnetic flux that was observed during this passage. Moreover, the region exhibited a complex topology with multiple domains of different magnetic helicities. The complexity was observed to reach such unprecedented levels that a detailed multi-wavelength analysis is necessary to precisely identify the solar sources of CMEs and MCs. Magnetic clouds are identified using in situ measurements and interplanetary scintillation (IPS) data. Results from these two different sets of data are also compared. Title: Magnetic Field, Density Current, and Lorentz Force Full Vector Maps of the NOAA 10808 Double Sunspot: Evidence of Strong Horizontal Current Flows in the Penumbra Authors: Bommier, V.; Landi Degl'Innocenti, E.; Schmieder, B.; Gelly, B. Bibcode: 2011ASPC..437..491B Altcode: The context is that of the so-called “fundamental ambiguity” (also azimuth ambiguity, or 180° ambiguity) in magnetic field vector measurements: two field vectors symmetrical with respect to the line-of-sight have the same polarimetric signature, so that they cannot be discriminated. We propose a method to solve this ambiguity by applying the “simulated annealing” algorithm to the minimization of the field divergence, added to the longitudinal current absolute value, the line-of-sight derivative of the magnetic field being inferred by the interpretation of the Zeeman effect observed by spectropolarimetry in two lines formed at different depths. We find that the line pair Fe I λ 6301.5 and Fe I λ 6302.5 is appropriate for this purpose. We treat the example case of the δ-spot of NOAA 10808 observed on 13 September 2005 between 14:25 and 15:25 UT with the THEMIS telescope. Besides the magnetic field resolved map, the electric current density vector map is also obtained. A strong horizontal current density flow is found surrounding each spot inside its penumbra, associated to a non-zero Lorentz force centripetal with respect to the spot center (i.e., oriented towards the spot center). The current wrapping direction is found to depend on the spot polarity: clockwise for the positive polarity, counterclockwise for the negative one. This analysis is made possible thanks to the UNNOFIT2 Milne-Eddington inversion code, where the usual theory is generalized to the case of a line Fe I λ 6301.5) that is not a normal Zeeman triplet line (like Fe I λ 6302.5). Title: Homologous Flares and Magnetic Field Topology in Active Region NOAA 10501 on 20 November 2003 Authors: Chandra, R.; Schmieder, B.; Mandrini, C. H.; Démoulin, P.; Pariat, E.; Török, T.; Uddin, W. Bibcode: 2011SoPh..269...83C Altcode: 2010arXiv1011.1187C; 2010SoPh..tmp..249C We present and interpret observations of two morphologically homologous flares that occurred in active region (AR) NOAA 10501 on 20 November 2003. Both flares displayed four homologous Hα ribbons and were both accompanied by coronal mass ejections (CMEs). The central flare ribbons were located at the site of an emerging bipole in the centre of the active region. The negative polarity of this bipole fragmented in two main pieces, one rotating around the positive polarity by ≈ 110° within 32 hours. We model the coronal magnetic field and compute its topology, using as boundary condition the magnetogram closest in time to each flare. In particular, we calculate the location of quasi-separatrix layers (QSLs) in order to understand the connectivity between the flare ribbons. Though several polarities were present in AR 10501, the global magnetic field topology corresponds to a quadrupolar magnetic field distribution without magnetic null points. For both flares, the photospheric traces of QSLs are similar and match well the locations of the four Hα ribbons. This globally unchanged topology and the continuous shearing by the rotating bipole are two key factors responsible for the flare homology. However, our analyses also indicate that different magnetic connectivity domains of the quadrupolar configuration become unstable during each flare, so that magnetic reconnection proceeds differently in both events. Title: Filament Interaction Modeled by Flux Rope Reconnection Authors: Török, T.; Chandra, R.; Pariat, E.; Démoulin, P.; Schmieder, B.; Aulanier, G.; Linton, M. G.; Mandrini, C. H. Bibcode: 2011ApJ...728...65T Altcode: Hα observations of solar active region NOAA 10501 on 2003 November 20 revealed a very uncommon dynamic process: during the development of a nearby flare, two adjacent elongated filaments approached each other, merged at their middle sections, and separated again, thereby forming stable configurations with new footpoint connections. The observed dynamic pattern is indicative of "slingshot" reconnection between two magnetic flux ropes. We test this scenario by means of a three-dimensional zero β magnetohydrodynamic simulation, using a modified version of the coronal flux rope model by Titov and Démoulin as the initial condition for the magnetic field. To this end, a configuration is constructed that contains two flux ropes which are oriented side-by-side and are embedded in an ambient potential field. The choice of the magnetic orientation of the flux ropes and of the topology of the potential field is guided by the observations. Quasi-static boundary flows are then imposed to bring the middle sections of the flux ropes into contact. After sufficient driving, the ropes reconnect and two new flux ropes are formed, which now connect the former adjacent flux rope footpoints of opposite polarity. The corresponding evolution of filament material is modeled by calculating the positions of field line dips at all times. The dips follow the morphological evolution of the flux ropes, in qualitative agreement with the observed filaments. Title: Driving mechanism of a failed eruption Authors: Guo, Y.; Ding, M. D.; Schmieder, B.; Li, H.; Törö, T.; Wiegelmann, T. Bibcode: 2011ASInC...2..307G Altcode: We find a magnetic flux rope before the M1.1 flare in active region 10767 on 2005 May 27 by a nonlinear force-free field extrapolation. TRACE observations of the filament eruption show that the erupting structure performed a writhing deformation and stopped rising at a certain height, suggesting that the flux rope converted some of its twist into writhe and was confined in the corona. After calculating the twist of the flux rope, we find that it was comparable to thresholds of the helical kink instability found in numerical simulations. We conclude that the activation and rise of the flux rope were triggered and initially driven by the kink instability. The decay index of the external magnetic field stays below the threshold for the torus instability within a long height range. The confinement of the eruption could be explained by the failure of the torus instability. Hard X-ray sources at the peak of the M1.1 flare coincided with the footpoints of the erupting helical structure, which indicates a high possibility that hard X-ray sources were produced more efficiently in the flux rope. Title: Study of solar flares and filament interaction in NOAA 10501 on 20 November, 2003 Authors: Chandra, R.; Schmieder, B.; Mandrini, C. H.; Démoulin, P.; Pariat, E.; Török, T.; Aulanier, G.; Uddin, W.; Linton, M. G. Bibcode: 2011ASInC...2..323C Altcode: We analyze the observations of two flares from NOAA AR 10501 on 20 November, 2003. The flares are homologous, exhibit four ribbons and are located in a quadrupolar magnetic configuration. The evolution of the ribbons suggests that the first eruption is triggered by "tether cutting" (with subsequent quadrupolar reconnection as in the "magnetic breakout" model), whereas the second one is consistent with the "magnetic breakout" model. Another interesting feature of our observations is the interaction of two filaments elongated in the north-south direction. The filaments merge at their central parts and afterwards change their orientation to the east-west direction. This merging and splitting is closely related to the evolution found in an MHD simulation as a result of reconnection between two flux ropes. Title: Three-dimensional morphology of a coronal prominence cavity Authors: Gibson, S. E.; Kucera, T. A.; Rastawicki, D.; Dove, J.; de Toma, G.; Hao, J.; Hill, S. M.; Hudson, H. S.; Marque, C.; McIntosh, P. S.; Rachmeler, L.; Reeves, K. K.; Schmieder, B.; Schmit, D. J.; Sterling, A.; Tripathi, D.; Williams, D. R.; Zhang, M. Bibcode: 2010AGUFMSH51A1667G Altcode: We present a three-dimensional density model of coronal prominence cavities, and a morphological fit that has been tightly constrained by a uniquely well-observed cavity. Observations were obtained as part of an International Heliophysical Year campaign by instruments from a variety of space- and ground-based observatories, spanning wavelengths from radio to soft-X-ray to integrated white light. From these data it is clear that the prominence cavity is the limb manifestation of a longitudinally-extended polar-crown filament channel, and that the cavity is a region of low density relative to the surrounding corona. As a first step towards quantifying density and temperature from campaign spectroscopic data, we establish the three-dimensional morphology of the cavity. This is critical for taking line-of-sight projection effects into account, since cavities are not localized in the plane of the sky and the corona is optically thin. We have augmented a global coronal streamer model to include a tunnel-like cavity with elliptical cross-section and a Gaussian variation of height along the tunnel length. We have developed a semi-automated routine that fits ellipses to cross-sections of the cavity as it rotates past the solar limb, and have applied it to Extreme Ultraviolet Imager (EUVI) observations from the two Solar Terrestrial Relations Observatory (STEREO) spacecraft. This defines the morphological parameters of our model, from which we reproduce forward-modeled cavity observables. We find that cavity morphology and orientation, in combination with the viewpoints of the observing spacecraft, explains the observed variation in cavity visibility for the east vs. west limbs. Title: Three-dimensional Morphology of a Coronal Prominence Cavity Authors: Gibson, S. E.; Kucera, T. A.; Rastawicki, D.; Dove, J.; de Toma, G.; Hao, J.; Hill, S.; Hudson, H. S.; Marqué, C.; McIntosh, P. S.; Rachmeler, L.; Reeves, K. K.; Schmieder, B.; Schmit, D. J.; Seaton, D. B.; Sterling, A. C.; Tripathi, D.; Williams, D. R.; Zhang, M. Bibcode: 2010ApJ...724.1133G Altcode: We present a three-dimensional density model of coronal prominence cavities, and a morphological fit that has been tightly constrained by a uniquely well-observed cavity. Observations were obtained as part of an International Heliophysical Year campaign by instruments from a variety of space- and ground-based observatories, spanning wavelengths from radio to soft X-ray to integrated white light. From these data it is clear that the prominence cavity is the limb manifestation of a longitudinally extended polar-crown filament channel, and that the cavity is a region of low density relative to the surrounding corona. As a first step toward quantifying density and temperature from campaign spectroscopic data, we establish the three-dimensional morphology of the cavity. This is critical for taking line-of-sight projection effects into account, since cavities are not localized in the plane of the sky and the corona is optically thin. We have augmented a global coronal streamer model to include a tunnel-like cavity with elliptical cross-section and a Gaussian variation of height along the tunnel length. We have developed a semi-automated routine that fits ellipses to cross-sections of the cavity as it rotates past the solar limb, and have applied it to Extreme Ultraviolet Imager observations from the two Solar Terrestrial Relations Observatory spacecraft. This defines the morphological parameters of our model, from which we reproduce forward-modeled cavity observables. We find that cavity morphology and orientation, in combination with the viewpoints of the observing spacecraft, explain the observed variation in cavity visibility for the east versus west limbs. Title: Driving Mechanism and Onset Condition of a Confined Eruption Authors: Guo, Y.; Ding, M. D.; Schmieder, B.; Li, H.; Török, T.; Wiegelmann, T. Bibcode: 2010ApJ...725L..38G Altcode: We study a confined eruption accompanied by an M1.1 flare in solar active region (AR) NOAA 10767 on 2005 May 27, where a pre-eruptive magnetic flux rope was reported in a nonlinear force-free field (NLFFF) extrapolation. The observations show a strong writhing motion of the erupting structure, suggesting that a flux rope was indeed present and converted some of its twist into writhe in the course of the eruption. Using the NLFFF extrapolation, we calculate the twist of the pre-eruptive flux rope and find that it is in very good agreement with thresholds of the helical kink instability found in numerical simulations. We conclude that the activation and rise of the flux rope were triggered and driven by the instability. Using a potential field extrapolation, we also estimate the height distribution of the decay index of the external magnetic field in the AR 1 hr prior to the eruption. We find that the decay index stays below the threshold for the torus instability for a significant height range above the erupting flux rope. This provides a possible explanation for the confinement of the eruption to the low corona. Title: Flare Energy Build-Up in a Decaying Active Region Near a Coronal Hole Authors: Su, Yingna; van Ballegooijen, Adriaan; Schmieder, Brigitte; Berlicki, Arkadiusz; Guo, Yang; Golub, Leon; Huang, Guangli Bibcode: 2010shin.confE.131S Altcode: A B1.7 two-ribbon flare occurred in a highly non-potential decaying active region near a coronal hole at 10:00 UT on May 17, 2008. This flare is large in the sense that it involves the entire region, and it is associated with both a filament eruption and a CME. We present multi-wavelength observations from EUV (TRACE, STEREO/EUVI), X-rays (Hinode/XRT), and H-alpha (THEMIS, BBSO) prior to, during and after the flare. Prior to the flare, the region contained two filaments. The long J-shaped sheared loops corresponding to the southern filament were evolved from two short loop systems, which happened around 22:00 UT after a filament eruption on May 16. Formation of highly sheared loops in the south eastern part of the region was observed by STEREO 8 hours before the flare. We also perform non-linear force free field (NLFFF) modeling for the region at two times prior to the flare, using the flux rope insertion method. The models include the non-force-free effect of magnetic buoyancy in the photosphere. The best-fit NLFFF models show good fit to observations both in the corona (X-ray and EUV loops) and chromosphere (H-alpha filament). We find that the horizontal fields in the photosphere are relatively insensitive to the present of flux ropes in the corona. The axial flux of the flux rope in the NLFFF model on May 17 is twice that on May 16, and the model on May 17 is only marginally stable. We also find that the quasi-circular flare ribbons are associated with the separatrix between open and closed fields. This observation and NLFFF modeling suggest that this flare may be triggered by the reconnection at the null point on the separatrix surface. Title: Statistical comparison of the observed and synthetic hydrogen Lyman line profiles in solar prominences Authors: Gunár, S.; Schwartz, P.; Schmieder, B.; Heinzel, P.; Anzer, U. Bibcode: 2010A&A...514A..43G Altcode:
Aims: We analyse a unique set of prominence SOHO/SUMER Lyman spectra by comparing it with synthetic spectra obtained by 2D multi-thread prominence fine-structure models.
Methods: We employed a novel statistical approach to the analysis of the observed and synthetic Lyman spectra. We compared the statistical distributions of the line properties of the observed and synthetic Lyman spectra using a set of four statistical criteria.
Results: We demonstrate the very good agreement between the observed Lyman spectra and synthetic spectra obtained by modelling.
Conclusions: Our set of statistical criteria is well-suited to analyses of the prominence Lyman spectra because of its sensitivity to a number of different parameters governing the conditions in the prominence fine structures. Title: Velocity vectors of a quiescent prominence observed by Hinode/SOT and the MSDP (Meudon) Authors: Schmieder, B.; Chandra, R.; Berlicki, A.; Mein, P. Bibcode: 2010A&A...514A..68S Altcode: 2009arXiv0911.5091S Context. The dynamics of prominence fine structures present a challenge to our understanding of the formation of cool plasma prominence embedded in the hot corona.
Aims: Observations performed by the high resolution Hinode/SOT telescope allow us to compute velocities perpendicular to the line-of-sight or transverse velocities. Combining simultaneous observations obtained in Hα with Hinode/SOT and the MSDP spectrograph operating in the Meudon solar tower, we derive the velocity vectors of a quiescent prominence.
Methods: The velocities perpendicular to the line-of-sight are measured using a time-slice technique and the Doppler shifts velocity using the bisector method.
Results: The Doppler shifts of bright threads derived from the MSDP show counterstreaming of the order of 5 km s-1 in the prominence and reaching 15 km s-1 at the edges of the prominence. Even though they are minimum values because of seeing effects, they are of the same order as the transverse velocities.
Conclusions: These measurements are very important because they suggest that the vertical structures detected by SOT may not be true vertical magnetic structures in the sky plane. The vertical structures could be a pile up of dips in more or less horizontal magnetic field lines in a 3D perspective, as proposed by many MHD modelers. In our analysis, we also calibrate the Hinode Hα data using MSDP observations obtained simultaneously.

A movie is available in electronic form at http://www.aanda.org Title: Coexisting Flux Rope and Dipped Arcade Sections Along One Solar Filament Authors: Guo, Y.; Schmieder, B.; Démoulin, P.; Wiegelmann, T.; Aulanier, G.; Török, T.; Bommier, V. Bibcode: 2010ApJ...714..343G Altcode: We compute the three-dimensional magnetic field of an active region in order to study the magnetic configuration of active region filaments. The nonlinear force-free field model is adopted to compute the magnetic field above the photosphere, where the vector magnetic field was observed by THEMIS/MTR on 2005 May 27. We propose a new method to remove the 180° ambiguity of the transverse field. Next, we analyze the implications of the preprocessing of the data by minimizing the total force and torque in the observed vector fields. This step provides a consistent bottom boundary condition for the nonlinear force-free field model. Then, using the optimization method to compute the coronal field, we find a magnetic flux rope along the polarity inversion line. The magnetic flux rope aligns well with part of an Hα filament, while the total distribution of the magnetic dips coincides with the whole Hα filament. This implies that the magnetic field structure in one section of the filament is a flux rope, while the other is a sheared arcade. The arcade induced a left-bearing filament in the magnetic field of negative helicity, which is opposite to the chirality of barbs that a flux rope would induce in a magnetic field of the same helicity sign. The field strength in the center of the flux rope is about 700 G, and the twist of the field lines is ~1.4 turns. Title: Physics of Solar Prominences: I—Spectral Diagnostics and Non-LTE Modelling Authors: Labrosse, N.; Heinzel, P.; Vial, J. -C.; Kucera, T.; Parenti, S.; Gunár, S.; Schmieder, B.; Kilper, G. Bibcode: 2010SSRv..151..243L Altcode: 2010SSRv..tmp...34L; 2010arXiv1001.1620L This review paper outlines background information and covers recent advances made via the analysis of spectra and images of prominence plasma and the increased sophistication of non-LTE ( i.e. when there is a departure from Local Thermodynamic Equilibrium) radiative transfer models. We first describe the spectral inversion techniques that have been used to infer the plasma parameters important for the general properties of the prominence plasma in both its cool core and the hotter prominence-corona transition region. We also review studies devoted to the observation of bulk motions of the prominence plasma and to the determination of prominence mass. However, a simple inversion of spectroscopic data usually fails when the lines become optically thick at certain wavelengths. Therefore, complex non-LTE models become necessary. We thus present the basics of non-LTE radiative transfer theory and the associated multi-level radiative transfer problems. The main results of one- and two-dimensional models of the prominences and their fine-structures are presented. We then discuss the energy balance in various prominence models. Finally, we outline the outstanding observational and theoretical questions, and the directions for future progress in our understanding of solar prominences. Title: A Technique for Removing Background Features in SECCHI - EUVI He II 304 Å Filtergrams: Application to the Filament Eruption of 22 May 2008 Authors: Artzner, G.; Gosain, S.; Schmieder, B. Bibcode: 2010SoPh..262..437A Altcode: 2010SoPh..tmp...41A; 2010SoPh..tmp...53A; 2010arXiv1001.4884A The STEREO mission has been providing a stereoscopic view of filament eruptions in the EUV. The clearest view during a filament eruption is seen in He II 304 Å observations. One of the main problems in visualizing filament dynamics in He II 304 Å is the strong background contrast due to surface features. We present a technique that removes background features and leaves behind only the filamentary structure, as seen by STEREO-A and -B. The technique uses a pair of STEREO He II 304 Å images observed simultaneously. The STEREO-B image is geometrically transformed to a STEREO-A view so that the background images appear similar. Filaments, being elevated structures, i.e., not lying on the same spherical surface as background features, do not appear similar in the transformed view. Thus, subtracting the two images cancels the background but leaves behind the filament structure. We apply this technique to study the dynamics of the filament-eruption event of 22 May 2008, which was observed by STEREO and followed by several ground-based observatories participating in the Joint Observing Programme (JOP 178). Title: Physics of Solar Prominences: II—Magnetic Structure and Dynamics Authors: Mackay, D. H.; Karpen, J. T.; Ballester, J. L.; Schmieder, B.; Aulanier, G. Bibcode: 2010SSRv..151..333M Altcode: 2010SSRv..tmp...32M; 2010arXiv1001.1635M Observations and models of solar prominences are reviewed. We focus on non-eruptive prominences, and describe recent progress in four areas of prominence research: (1) magnetic structure deduced from observations and models, (2) the dynamics of prominence plasmas (formation and flows), (3) Magneto-hydrodynamic (MHD) waves in prominences and (4) the formation and large-scale patterns of the filament channels in which prominences are located. Finally, several outstanding issues in prominence research are discussed, along with observations and models required to resolve them. Title: Magnetic Field Structures in a Facular Region Observed by THEMIS and Hinode Authors: Guo, Y.; Schmieder, B.; Bommier, V.; Gosain, S. Bibcode: 2010SoPh..262...35G Altcode: 2010SoPh..tmp...30G; 2010arXiv1002.4355G The main objective of this paper is to build and compare vector magnetic maps obtained by two spectral polarimeters, i.e. THEMIS/MTR and Hinode SOT/SP, using two inversion codes (UNNOFIT and MELANIE) based on the Milne - Eddington solar atmosphere model. To this end, we used observations of a facular region within active region NOAA 10996 on 23 May 2008, and found consistent results concerning the field strength, azimuth and inclination distributions. Because SOT/SP is free from the seeing effect and has better spatial resolution, we were able to resolve small magnetic polarities with sizes of 1″ to 2″, and we could detect strong horizontal magnetic fields, which converge or diverge in negative or positive facular polarities. These findings support models which suggest the existence of small vertical flux tube bundles in faculae. A new method is proposed to get the relative formation heights of the multi-lines observed by MTR assuming the validity of a flux tube model for the faculae. We found that the Fe I 6302.5 Å line forms at a greater atmospheric height than the Fe I 5250.2 Å line. Title: How do unresolved motions affect the prominence hydrogen Lyman spectrum. Authors: Gunar, Stanislav; Schwartz, Pavol; Schmieder, Brigitte; Heinzel, Petr; Anzer, Ulrich Bibcode: 2010cosp...38.2830G Altcode: 2010cosp.meet.2830G Space-born observations of quiescent prominences in the hydrogen Lyman line series provide a considerable amount of information about their structure and physical properties. Lyman line series thus represents a focus of several detailed studies. However, the substantial asymmetries exhibited by considerable number of observed Lyman line profiles present a strong indication for the existence of hidden fine-structure dynamics. If attributed merely to the Doppler shift effect, these asymmetries would correspond to radial velocities of the order of 100 km/s. Such high velocities, however, were never observed in quiescent prominences. Typical fine-structure velocities are of the order of 10 km/s. To tackle this problem, we have modified our 2D multi-thread prominence models and randomly assigned line-of-sight (LOS) velocities of the order of 10 km/s to each thread. The obtained synthetic Lyman spectrum exhibits substantial asymme-tries of the line profiles comparable with SOHO/SUMER observations. Moreover, our results do indicate that the synthetic Lyman-α profiles may exhibit an opposite asymmetry to that of the higher Lyman lines. This is consistent with observations which often show opposite asym-metries of these lines at the same prominence location. We have demonstrated the agreement of synthetic and observed spectra not only by comparing asymmetries of individual profiles but also by exploiting statistically significant sets of the observed and synthetic data. These results represent an important step in our understanding of hidden fine-structure dynamics of quiescent prominences. Title: Counterstreaming in quiescent prominences observed by Hinode/SOT and Meudon/MSDP Authors: Schmieder, Brigitte; Chandra, Ramesh; Berlicki, Arkadiusz; Mein, Pierre Bibcode: 2010cosp...38.2943S Altcode: 2010cosp.meet.2943S Prominences have been successfully observed by Hinode in April 2007 exhibiting a strong dy-namics of their fine structures. The dynamics of a prominence is a challenge to understand the formation of cool prominence plasma embedded in the hot corona. Combining simultaneous observations obtained in Hα with Hinode/SOT and the MSDP spectrograph operating at the Meudon solar tower, velocity vectors have been derived. The Doppler-shifts of bright threads are of the same order as the transverse velocities measured perpendicularly to the line of sight. Counterstreamings are detected at the top of the prominence. The vertical structures of the prominence could be a pile up of dips in magnetic field lines viewed in 3D Title: How Can a Negative Magnetic Helicity Active Region Generate a Positive Helicity Magnetic Cloud? Authors: Chandra, R.; Pariat, E.; Schmieder, B.; Mandrini, C. H.; Uddin, W. Bibcode: 2010SoPh..261..127C Altcode: 2009arXiv0910.0968C The geoeffective magnetic cloud (MC) of 20 November 2003 was associated with the 18 November 2003 solar active events in previous studies. In some of these, it was estimated that the magnetic helicity carried by the MC had a positive sign, as did its solar source, active region (AR) NOAA 10501. In this article we show that the large-scale magnetic field of AR 10501 has a negative helicity sign. Since coronal mass ejections (CMEs) are one of the means by which the Sun ejects magnetic helicity excess into interplanetary space, the signs of magnetic helicity in the AR and MC must agree. Therefore, this finding contradicts what is expected from magnetic helicity conservation. However, using, for the first time, correct helicity density maps to determine the spatial distribution of magnetic helicity injections, we show the existence of a localized flux of positive helicity in the southern part of AR 10501. We conclude that positive helicity was ejected from this portion of the AR leading to the observed positive helicity MC. Title: Estimation of width and inclination of a filament sheet using He II 304 Å observations by STEREO/EUVI Authors: Gosain, S.; Schmieder, B. Bibcode: 2010AnGeo..28..149G Altcode: 2010arXiv1001.3004G The STEREO mission has been providing stereoscopic view of the filament eruptions in EUV wavelengths. The most extended view during filament eruptions is seen in He II 304 Å observations, as the filament spine appears darker and sharper. The projected filament width appears differently when viewed from different angles by STEREO satellites. Here, we present a method for estimating the width and inclination of the filament sheet using He II 304 Å observations by STEREO-A and B satellites from the two viewpoints. The width of the filament sheet, when measured from its feet to its apex, gives estimate of filament height above the chromosphere. Title: A Flaring Twisted Emerging Flux Region Authors: Chandra, R.; Schmieder, B.; Aulanier, G.; Malherbe, J. M. Bibcode: 2010ASSP...19..523C Altcode: 2010mcia.conf..523C We present signatures of the emergence of a twisted flux tube in decaying active region NOAA AR10365 on 27 May 2003. When the magnetic flux tube is twisted, an asymmetry appears in the magnetogram because of the contribution of the azimuthal component to the observed vertical component of the field. In this case, the vertical component produces two "tongues" (Fig. 1, left). The twist of the flux tube is revealed by the photospheric longitudinalmagnetic field pattern: diverging flows of opposite polarities, elongated polarities with a "tongue" shape. The asymmetry of the opposite polarities is interpreted as right-hand twist of the emerging flux tube. Title: Vector Magnetic Field in Emerging Flux Regions Authors: Schmieder, B.; Pariat, E. Bibcode: 2010ASSP...19..505S Altcode: 2010mcia.conf..505S A crucial phase in magnetic flux emergence is the rise of magnetic flux tubes through the solar photosphere, which represents a severe transition between the very different environments of the solar interior and corona. Multi-wavelength observations with Flare Genesis, TRACE, SoHO, and more recently with the vector magnetographs at THEMIS and Hida (DST) led to the following conclusions. The fragmented magnetic field in the emergence region - with dipped field lines or bald patches - is directly related with Ellerman bombs, arch filament systems, and overlying coronal loops. Measurements of vector magnetic fields have given evidence that undulating "serpentine" fields are present while magnetic flux tubes cross the photosphere. See the sketch below, and for more detail see Pariat et al. (2004, 2007); Watanabe et al. (2008): Title: Title: Can purely emissive Ly_beta prominence spectra be caused by the line of sight oriented parallelly to the magnetic field? Authors: Schwartz, Pavol; Gunar, Stanislav; Heinzel, Petr; Schmieder, Brigitte Bibcode: 2010cosp...38.2852S Altcode: 2010cosp.meet.2852S Small bright prominence was observed on the SW limb on April 26, 2007 between 13:01 and 23:50 UT by SUMER spectrograph on-board SoHO in hydrogen Lyman line series except the Lyα line. Profiles of the Lyβ line are peculiar for a prominence because they do not exhibit any central reversals (dips in cores of the lines). This could be explained by the fact that the line of sight is parallel with the direction of the magnetic field in the prominence. We can investigate this fact by a statistical comparison of observed profiles with the synthetic ones computed using the 2D multi-thread model of the prominence. We use synthetic profiles obtained for various orientations of the line of sight with respect to the magnetic field, ranging from perpendicular to parallel. Profiles are compared statistically using their characteristics such as integral intensities, so-called Lyman decrement (ratio of integral intensity of the line to integral intensity of the Lyβ line, etc.). Title: Ejective events from a complex active region Authors: Mandrini, Cristina H.; Chandra, Ramesh; Pariat, Etienne; Schmieder, Brigitte; Demoulin, Pascal; Toeroek, Tibor; Uddin, Wahab Bibcode: 2010cosp...38.1886M Altcode: 2010cosp.meet.1886M On 18 and 20 November 2003 active region (AR) 10501 produced a series of M flares all of them associated with coronal mass ejections (CMEs). The particularity of this AR is that while observational tracers of the magnetic helicity sign indicate that the large scale field in the region had a negative magnetic helicity sign, the MC associated to the most intense flare/CME on November 18 showed the opposite sign. Furthermore, the filaments observed on November 20 present morphological characteristics that correspond to a negative magnetic helicity sign, the rotation of the polarities of an emerging bipole indicate negative magnetic helicity sign injection; however, the flare ribbons observed after two homologous events can be connected either by field lines computed using a positive or a negative helicity sign magnetic field. We combine Hα, EUV, hard X-rays, and magnetic field data analysis with magnetic field modelling, and magnetic helicity injection computations to understand the origin of the helicity sign discrepancies discussed above. On November 20 magnetic field modeling and topology computations (in particular, the location of quasi-separatrix layers in relation to flare ribbons and evolution) give us clues about the CME initiation process. Title: Relations between theoretical and observational plasma parameters and the radiation of the prominence Authors: Berlicki, Arkadiusz; Schwartz, Pavol; Schmieder, Brigitte; Heinzel, Petr; Gunar, Stanislav Bibcode: 2010cosp...38.2945B Altcode: 2010cosp.meet.2945B On April 26, 2007 the quiescent prominence was observed during the coordinated campaign of prominence studies icluding SOT, XRT, and EIS on Hinode, MDI, EIT, SUMER, and CDS on SOHO, TRACE, and several ground-based observatories. This was the first Hinode-SUMER ob-serving campaign. In this analysis we use the data obtained with Hinode/SOT, SOHO/SUMER and Multichannel Spectrograph MSDP (Meudon, France). The SUMER instrument provide us the UV spectra of the prominence in several spectral lines along the 120 arcsec slit crossing the prominence. We used the following lines: Lβ, Lγ, Lδ, L , C III and S VI. Using these spectra we calculated the integrated intensities along the slit for all these lines. We also calculated the integrated intensity of the Hα line from the spectroscopic ground-based MSDP observations for the same parts of the prominence observed at the same time. These intensities were used to calibrate the Hinode/SOT data. Next, we analyzed the relations between different observed intensities in these lines and compared them with the values obtained from the theoretical simulations. We analyzed the correlations between observations and theoretical modeling and as a results we estimated the different physical parameters of the prominence plasma. Title: A 3D view of eruptive filaments by STEREO Authors: Gosain, Sanjay; Schmieder, Brigitte; Venkatakrishnan, P.; Chandra, Ramesh; Artzner, Guy Bibcode: 2010cosp...38.2916G Altcode: 2010cosp.meet.2916G STEREO/SECHI/EUVI A and B observe different views of the eruption of a quiescent filament. We will concentrate on two events: (i) May 20 to 22, 2008 event (A and B separated by 52.4 degrees from each other), and (ii) September 25 to 26, 2009 event (A and B more than 100 degrees from each other. After using different techniques of reconstruction we obtained a 3 dimensional view of untwisted flux ropes in He II 304 Angstrom, with fine structures. The entire disappearance phase lasted more than ten hours. The filament evolved very slowly ( 5 km/s) from a dense structure with a thick spine into fine threads. Individual threads are seen to be oscillating and rising to an altitude of about 150 Mm with velocities of about 100 km/s. The plasma disappears by diffusion in the corona. Weak CME events are recorded by LASCO at the beginning of the disappearance. In this paper we shall present the dynamics of the filament eruptions as viewed in 3D by STEREO using different methods. We shall explore the causes and consequences of the filament disappearance. Title: Actors of the main activity of large complex centres during the 23 Solar Cycle maximum Authors: Schmieder, Brigitte; Chandra, Ramesh; Demoulin, Pascal; Mandrini, Cristina H.; Venkatakrishnan, P.; Manoharan, P. K.; Uddin, Wahab; Pariat, Etienne; Toeroek, Tibor; Molodij, Guillaume; Kumar, P. Bibcode: 2010cosp...38.1861S Altcode: 2010cosp.meet.1861S During the maximum of the last Solar Cycle solar cycle 23, large active regions had a long life spanning several solar rotations and produced a large number of X-ray class flares, CMEs and Magnetic clouds (MC). This was the case for the Halloween active regions in 2003. The most geoeffective magnetic cloud of the cycle (Dst=-457) has its source in one passage of the active region (NOAA 10501) on November 18, 2003. Such an activity is presumably due to continuous emerging magnetic flux that was observed during this passage. Moreover, the region exhibited a complex topology with multiple domains of distinct magnetic helicities. The complexity is observed to reach such unprecedented levels that a detailed multi wavelength analysis is necessary to precisely identify the sources of CMEs and MCs. Title: Hinode/SOT Measurements of Flows and Waves in Solar Prominences Authors: Berger, Thomas; Okamoto, Takenori; Schmieder, Brigitte Bibcode: 2010cosp...38.2913B Altcode: 2010cosp.meet.2913B We review Hinode Solar Optical Telescope (SOT) measurements of flows and waves in quies-cent and active solar prominences. In quiescent prominences, Hinode/SOT observations have revealed a new mode of buoyant transport in the form of dark upflows that originate at the chromospheric base of the prominence. The upflows can take the form of large-scale (10 Mm) "bubbles" that rise through the entire prominence into the overlying coronal cavity, or they can take the form of numerous small-scale (1 Mm) plumes that generate from an apparent Rayleigh-Taylor instability on the boundary between the prominence and the impinging buoy-ant flow system. The episodic flows directly inject mass, magnetic flux, and helicity into the overlying coronal cavity, moving the system towards destabilization and eruption in the form of CMEs. Hinode/SOT quiescent prominence observations have also verified the existence of ubiquitous downflow streams and vortex flows confirming that prominences are far from magne-tostatic conditions. Tracking and doppler measurements of prominence downflows find speeds of 5-15 km s-1 and imply that the trajectories are not strictly vertical. Active region promi-nence studies find counter-streaming flows along horizontal magnetic field lines with velocities of 20-30 km s-1 ; upflows, downflow streams, and rotational flows have not been observed in these systems. Active Region prominence field lines exhibit transverse oscillations indicative of Alfv`n waves with periods of several minutes, amplitudes of 1 Mm, and wavelengths of 250 Mm or more. These properties are consistent with magnetic field strengths of 50 gauss or more at typical prominence density conditions and carry enough energy to heat the surrounding prominence/corona transition region (PCTR). Title: Flare Energy Build-up in a Decaying Active Region Near a Coronal Hole Authors: Su, Yingna; van Ballegooijen, Adriaan; Schmieder, Brigitte; Berlicki, Arkadiusz; Guo, Yang; Golub, Leon; Huang, Guangli Bibcode: 2009ApJ...704..341S Altcode: A B1.7 two-ribbon flare occurred in a highly non-potential decaying active region near a coronal hole at 10:00 UT on 2008 May 17. This flare is "large" in the sense that it involves the entire region, and it is associated with both a filament eruption and a coronal mass ejection. We present multi-wavelength observations from EUV (TRACE, STEREO/EUVI), X-rays (Hinode/XRT), and Hα (THEMIS, BBSO) prior to, during and after the flare. Prior to the flare, the region contained two filaments. The long J-shaped sheared loops corresponding to the southern filament were evolved from two short loop systems, which happened around 22:00 UT after a filament eruption on May 16. Formation of highly sheared loops in the southeastern part of the region was observed by STEREO 8 hr before the flare. We also perform nonlinear force-free field (NLFFF) modeling for the region at two times prior to the flare, using the flux rope insertion method. The models include the non-force-free effect of magnetic buoyancy in the photosphere. The best-fit NLFFF models show good fit to observations both in the corona (X-ray and EUV loops) and chromosphere (Hα filament). We find that the horizontal fields in the photosphere are relatively insensitive to the present of flux ropes in the corona. The axial flux of the flux rope in the NLFFF model on May 17 is twice that on May 16, and the model on May 17 is only marginally stable. We also find that the quasi-circular flare ribbons are associated with the separatrix between open and closed fields. This observation and NLFFF modeling suggest that this flare may be triggered by the reconnection at the null point on the separatrix surface. Title: 3D Evolution of a Filament Disappearance Event Observed by STEREO Authors: Gosain, S.; Schmieder, B.; Venkatakrishnan, P.; Chandra, R.; Artzner, G. Bibcode: 2009SoPh..259...13G Altcode: 2009arXiv0910.0786G A filament disappearance event was observed on 22 May 2008 during our recent campaign JOP 178. The filament, situated in the Southern Hemisphere, showed sinistral chirality consistent with the hemispheric rule. The event was well observed by several observatories, in particular by THEMIS. One day, before the disappearance, Hα observations showed up- and down-flows in adjacent locations along the filament, which suggest plasma motions along twisted flux rope. THEMIS and GONG observations show shearing photospheric motions leading to magnetic flux canceling around barbs. STEREO A, B spacecraft with separation angle 52.4°, showed quite different views of this untwisting flux rope in He II 304 Å images. Here, we reconstruct the three-dimensional geometry of the filament during its eruption phase using STEREO EUV He II 304 Å images and find that the filament was highly inclined to the solar normal. The He II 304 Å movies show individual threads, which oscillate and rise to an altitude of about 120 Mm with apparent velocities of about 100 km s−1 during the rapid evolution phase. Finally, as the flux rope expands into the corona, the filament disappears by becoming optically thin to undetectable levels. No CME was detected by STEREO, only a faint CME was recorded by LASCO at the beginning of the disappearance phase at 02:00 UT, which could be due to partial filament eruption. Further, STEREO Fe XII 195 Å images showed bright loops beneath the filament prior to the disappearance phase, suggesting magnetic reconnection below the flux rope. Title: Fan-Spine Topology Formation Through Two-Step Reconnection Driven by Twisted Flux Emergence Authors: Török, T.; Aulanier, G.; Schmieder, B.; Reeves, K. K.; Golub, L. Bibcode: 2009ApJ...704..485T Altcode: 2009arXiv0909.2235T We address the formation of three-dimensional nullpoint topologies in the solar corona by combining Hinode/X-ray Telescope (XRT) observations of a small dynamic limb event, which occurred beside a non-erupting prominence cavity, with a three-dimensional (3D) zero-β magnetohydrodynamics (MHD) simulation. To this end, we model the boundary-driven "kinematic" emergence of a compact, intense, and uniformly twisted flux tube into a potential field arcade that overlies a weakly twisted coronal flux rope. The expansion of the emerging flux in the corona gives rise to the formation of a nullpoint at the interface of the emerging and the pre-existing fields. We unveil a two-step reconnection process at the nullpoint that eventually yields the formation of a broad 3D fan-spine configuration above the emerging bipole. The first reconnection involves emerging fields and a set of large-scale arcade field lines. It results in the launch of a torsional MHD wave that propagates along the arcades, and in the formation of a sheared loop system on one side of the emerging flux. The second reconnection occurs between these newly formed loops and remote arcade fields, and yields the formation of a second loop system on the opposite side of the emerging flux. The two loop systems collectively display an anenome pattern that is located below the fan surface. The flux that surrounds the inner spine field line of the nullpoint retains a fraction of the emerged twist, while the remaining twist is evacuated along the reconnected arcades. The nature and timing of the features which occur in the simulation do qualititatively reproduce those observed by XRT in the particular event studied in this paper. Moreover, the two-step reconnection process suggests a new consistent and generic model for the formation of anemone regions in the solar corona. Title: Evidence of Magnetic Helicity in Emerging Flux and Associated Flare Authors: Chandra, R.; Schmieder, B.; Aulanier, G.; Malherbe, J. M. Bibcode: 2009SoPh..258...53C Altcode: 2009arXiv0906.1210C The aim of this paper is to look at the magnetic helicity structure of an emerging active region and show that both emergence and flaring signatures are consistent with a same sign for magnetic helicity. We present a multiwavelength analysis of an M1.6 flare occurring in the NOAA active region 10365 on 27 May 2003, in which a large new bipole emerges in a decaying active region. The diverging flow pattern and the "tongue" shape of the magnetic field in the photosphere with elongated polarities are highly suggestive of the emergence of a twisted flux tube. The orientation of these tongues indicates the emergence of a flux tube with a right-hand twist (i.e., positive magnetic helicity). The flare signatures in the chromosphere are ribbons observed in Hα by the MSDP spectrograph in the Meudon solar tower and in 1600 Å by TRACE. These ribbons have a J shape and are shifted along the inversion line. The pattern of these ribbons suggests that the flare was triggered by magnetic reconnection at coronal heights below a twisted flux tube of positive helicity, corresponding to that of the observed emergence. It is the first time that such a consistency between the signatures of the emerging flux through the photosphere and flare ribbons has been clearly identified in observations. Another type of ribbons observed during the flare at the periphery of the active region by the MSDP and SOHO/EIT is related to the existence of a null point, which is found high in the corona in a potential field extrapolation. We discuss the interpretation of these secondary brightenings in terms of the "breakout" model and in terms of plasma compression/heating within large-scale separatrices. Title: Three frontside full halo coronal mass ejections with a nontypical geomagnetic response Authors: Rodriguez, L.; Zhukov, A. N.; Cid, C.; Cerrato, Y.; Saiz, E.; Cremades, H.; Dasso, S.; Menvielle, M.; Aran, A.; Mandrini, C.; Poedts, S.; Schmieder, B. Bibcode: 2009SpWea...7.6003R Altcode: Forecasting potential geoeffectiveness of solar disturbances (in particular, of frontside full halo coronal mass ejections) is important for various practical purposes, e.g., for satellite operations, radio communications, global positioning system applications, power grid, and pipeline maintenance. We analyze three frontside full halo coronal mass ejections (CMEs) that occurred in the year 2000 (close to the activity maximum of solar cycle 23), together with associated solar and heliospheric phenomena as well as their impact on the Earth's magnetosphere. Even though all three were fast full halos (with plane of the sky speeds higher than 1100 km/s), the geomagnetic response was very different for each case. After analyzing the source regions of these halo CMEs, it was found that the halo associated with the strongest geomagnetic disturbance was the one that initiated farther away from disk center (source region at W66); while the other two CMEs originated closer to the central meridian but had weaker geomagnetic responses. Therefore, these three events do not fit into the general statistical trends that relate the location of the solar source and the corresponding geoeffectivity. We investigate possible causes of such a behavior. Nonradial direction of eruption, passage of the Earth through a leg of an interplanetary flux rope, and strong compression at the eastern flank of a propagating interplanetary CME during its interaction with the ambient solar wind are found to be important factors that have a direct influence on the resulting north-south interplanetary magnetic field (IMF) component and thus on the CME geoeffectiveness. We also find indications that interaction of two CMEs could help in producing a long-lasting southward IMF component. Finally, we are able to explain successfully the geomagnetic response using plasma and magnetic field in situ measurements at the L1 point. We discuss the implications of our results for operational space weather forecasting and stress the difficulties of making accurate predictions with the current knowledge and tools at hand. Title: Magnetic Nonpotentiality Accumulation Prior to a "Large" B1.7 Two-Ribbon Flare Authors: Su, Yingna; van Ballegooijen, A.; Schmieder, B.; Berlicki, A.; Guo, Y.; Golub, L. Bibcode: 2009SPD....40.2002S Altcode: A B1.7 two-ribbon flare occurred in a highly non-potential decaying active region near a coronal hole at 10:00 UT on May 17, 2008. This flare is "large" in the sense that it involves the entire region, and it is associated with both a filament eruption and a CME. We present multi-wavelength observations from EUV (TRACE, STEREO/EUVI), X-rays (Hinode/XRT), and H-alpha (THEMIS, BBSO) prior to, during and after the flare. Prior to the flare, the observed coronal loops are mainly two sets of highly sheared loops surrounding two filaments. The sheared loops in the southern part of the region appeared in TRACE around 22:00 UT after a filament ejection on May 16. We also performed non-linear force free field (NLFFF) modeling for the region prior to the flare, using the flux rope insertion method. The model at 11:42 UT on May 16 is based on THEMIS (vector) and MDI magnetograms, and the model at 08:03 UT on May 17 is based only on MDI magnetogram. The best-fit NLFFF models show good fit to observations both in the corona (X-ray and EUV loops) and chromosphere (H-alpha filament). In the photosphere, the vectors in the best-fit NLFFF model are similar to those in the potential model. However, in the chromosphere, the vectors in the best-fit NLFFF model present strong non-potentiality, especially at the end of the inserted flux rope. We also found that the axial flux of the flux rope in the NLFFF model on May 17 is much higher than that on May 16. Title: Coronal loops, flare ribbons and aurora during slip-running Authors: Schmieder, Brigitte; Aulanier, Guillaume; Démoulin, Pascal; Pariat, Etienne Bibcode: 2009EP&S...61..565S Altcode: 2009EP&S...61L.565S Solar two ribbon flares are commonly explained by magnetic field reconnections in the low corona. During the reconnection energetic particles (electrons and protons) are accelerated from the reconnection site. These particles are following the magnetic field lines down to the chromosphere. As the plasma density is higher in these lower layers, there are collisions and emission of radiation. Thus bright ribbons are observed at both ends of flare loops. These ribbons are typically observed in Hα and in EUV with SoHO and TRACE. As the time is going, these ribbons are expanding away of each other. In most studied models, the reconnection site is a separator line, where two magnetic separatrices intersect. They define four distinct connectivity domains, across which the magnetic connectivity changes discontinuously. In this paper, we present a generalization of this model to 3D complex magnetic topologies where there are no null points, but quasi-separatrices layers instead. In that case, while the ribbons spread away during reconnection, we show that magnetic field lines can quickly slip along them. We propose that this new phenomenon could explain fast extension of Hα and TRACE 1600 Å ribbons, fast moving HXR footpoints along the ribbons as observed by RHESSI, and that it is observed in soft X rays with Hinode/XRT. Title: Evidence for a Pre-Eruptive Twisted Flux Rope Using the Themis Vector Magnetograph Authors: Canou, A.; Amari, T.; Bommier, V.; Schmieder, B.; Aulanier, G.; Li, H. Bibcode: 2009ApJ...693L..27C Altcode: Although there is evidence that twisted structures form during large-scale eruptive events, it is not yet clear whether these exist in the pre-eruptive phase as twisted flux ropes (TFRs) in equilibrium. This question has become a major issue since several theoretical mechanisms can lead to the formation of TFRs. These models consider either the evolution of a coronal configuration driven by photospheric changes or the emergence of TFR from the convection zone. We consider as a target for addressing this issue the active region NOAA AR 10808 known at the origin of several large-scale eruptive phenomena, and associated with the emergence of a δ-spot. Using the THEMIS vector magnetogram as photospheric boundary conditions for our nonlinear force-free reconstruction model of the low corona and without any other assumption, we show that the resulting pre-eruptive configuration exhibits a TFR above the neutral line of the emerging δ-spot. In addition, the free magnetic energy of this configuration could even be large enough to explain such resulting large-scale eruptive events. Title: Solar prominences Authors: Schmieder, Brigitte; Aulanier, Guillaume; Török, Tibor Bibcode: 2009IAUS..257..223S Altcode: Solar filaments (or prominences) are magnetic structures in the corona. They can be represented by twisted flux ropes in a bipolar magnetic environment. In such models, the dipped field lines of the flux rope carry the filament material and parasitic polarities in the filament channel are responsible for the existence of the lateral feet of prominences.

Very simple laws do exist for the chirality of filaments, the so-called “filament chirality rules”: commonly dextral/sinistral filaments corresponding to left- (resp. right) hand magnetic twists are in the North/South hemisphere. Combining these rules with 3D weakly twisted flux tube models, the sign of the magnetic helicity in several filaments were identified. These rules were also applied to the 180° disambiguation of the direction of the photospheric transverse magnetic field around filaments using THEMIS vector magnetograph data (López Ariste et al. 2006). Consequently, an unprecedented evidence of horizontal magnetic support in filament feet has been observed, as predicted by former magnetostatic and recent MHD models.

The second part of this review concerns the role of emerging flux in the vicinity of filament channels. It has been suggested that magnetic reconnection between the emerging flux and the pre-existing coronal field can trigger filament eruptions and CMEs. For a particular event, observed with Hinode/XRT, we observe signatures of such a reconnection, but no eruption of the filament. We present a 3D numerical simulation of emerging flux in the vicinity of a flux rope which was performed to reproduce this event and we briefly discuss, based on the simulation results, why the filament did not erupt. Title: Linking two consecutive nonmerging magnetic clouds with their solar sources Authors: Dasso, S.; Mandrini, C. H.; Schmieder, B.; Cremades, H.; Cid, C.; Cerrato, Y.; Saiz, E.; Démoulin, P.; Zhukov, A. N.; Rodriguez, L.; Aran, A.; Menvielle, M.; Poedts, S. Bibcode: 2009JGRA..114.2109D Altcode: 2009JGRA..11402109D; 2012arXiv1212.5546D On 15 May 2005, a huge interplanetary coronal mass ejection (ICME) was observed near Earth. It triggered one of the most intense geomagnetic storms of solar cycle 23 (Dst peak = -263 nT). This structure has been associated with the two-ribbon flare, filament eruption, and coronal mass ejection originating in active region 10759 (NOAA number). We analyze here the sequence of events, from solar wind measurements (at 1 AU) and back to the Sun, to understand the origin and evolution of this geoeffective ICME. From a detailed observational study of in situ magnetic field observations and plasma parameters in the interplanetary (IP) medium and the use of appropriate models we propose an alternative interpretation of the IP observations, different to those discussed in previous studies. In our view, the IP structure is formed by two extremely close consecutive magnetic clouds (MCs) that preserve their identity during their propagation through the interplanetary medium. Consequently, we identify two solar events in Hα and EUV which occurred in the source region of the MCs. The timing between solar and IP events, as well as the orientation of the MC axes and their associated solar arcades are in good agreement. Additionally, interplanetary radio type II observations allow the tracking of the multiple structures through inner heliosphere and pin down the interaction region to be located midway between the Sun and the Earth. The chain of observations from the photosphere to interplanetary space is in agreement with this scenario. Our analysis allows the detection of the solar sources of the transients and explains the extremely fast changes of the solar wind due to the transport of two attached (though nonmerging) MCs which affect the magnetosphere. Title: Magnetic helicity and solar prominence formation Authors: Aulanier, G.; Schmieder, B. Bibcode: 2008sf2a.conf..543A Altcode: Simple laws have long-since been put forward from the chirality of observed features to derive the direction of the axial magnetic field inside solar filaments. These are the so-called ``filament chirality rules''. Here, we report on two uses of these rules applied to THEMIS and SVST observations and to MHD simulations. Being the first to apply these rules to the 180° disambiguation of the direction of the photospheric transverse magnetic field around filaments, we found the unprecedented evidence of magnetic support in filament feet, as predicted by former magnetostatic and recent MHD models. By combining these rules with 3D weakly twisted flux tube models, we identified the sign of the magnetic helicity in several filaments. Following their interactions with one another over a few days, we found that the observational condition for two filaments to merge is that their flux tubes must have the same helicity sign. We theoretically recovered these results, by conducting a parametric study of 3D numerical MHD simulations of sheared bipoles. This study also provided new conditions for filament merging, in yet-unobserved configurations in which sheared bipoles are oppositely oriented. Title: Photospheric flows around a quiescent filament at Large and small scale and their ffects on filament destabilization Authors: Roudier, Th.; Malherbe, J. M.; Švanda, M.; Molodij, G.; Keil, S.; Sütterlin, P.; Schmieder, B.; Bommier, V.; Aulanier, G.; Meunier, N.; Rieutord, M.; Rondi, S. Bibcode: 2008sf2a.conf..569R Altcode: We study the influence of large and small scales photospheric motions on the destabilization of an eruptive filament, observed on October 6, 7, and 8, 2004 as part of an international observing campaign (JOP 178). Large-scale horizontal flows are invetigated from a series of MDI/SOHO full-disc Dopplergrams and magnetograms from THEMIS. Small-scale horizontal flows were derived using local correlation tracking on TRACE satellite, Dutch Open Telescope (DOT) and The Dunn Solar telescope (DST) data. The topology of the flow field changed significantly during the filament eruptive phase, suggesting a possible coupling between the surface flow field and the coronal magnetic field. We measured an increase of the shear below the point where the eruption starts and a decrease in shear after the eruption. We conclude that there is probably a link between changes in surface flow and the disappearance of the eruptive filament. Title: On Lyman-line asymmetries in quiescent prominences Authors: Gunár, S.; Heinzel, P.; Anzer, U.; Schmieder, B. Bibcode: 2008A&A...490..307G Altcode: Aims: We study the asymmetries of the synthetic hydrogen Lyman lines and the process responsible for their formation.
Methods: To obtain the synthetic Lyman line profiles, we use a multi-thread prominence fine-structure model consisting of identical 2D threads. The 2D thread models are in MHS equilibrium, include an empirical prominence-corona transition region, and solve consistently 2D non-LTE radiative transfer. Each thread of the multi-thread model has a randomly assigned line-of-sight (LOS) velocity.
Results: The synthetic Lyman spectrum obtained by multi-thread modelling exhibits substantial asymmetries of the line profiles, even though the LOS velocities of individual threads are only of the order of 10 km s-1. Moreover, our results indicate that the synthetic Lyman-α profiles may exhibit an opposite asymmetry to that of the higher Lyman lines.
Conclusions: The presence and behaviour of the asymmetrical profiles of the synthetic Lyman lines agree with observed profiles acquired by SUMER.

Appendix A is only available in electronic form at http://www.aanda.org Title: NLTE modelling of the flaring atmosphere above sunspot Authors: Berlicki, A.; Heinzel, P.; Schmieder, B.; Li, H. Bibcode: 2008A&A...490..315B Altcode: Aims: We performed an analysis of the solar flaring atmosphere above sunspots. During the flare on October 20, 2003 many flaring structures were observed projected onto the sunspots. We analysed the Hα and Ca II line profiles emitted by the ribbons partially overlapping the sunspots. In the penumbra, the line intensity in the far wings is lower than in a typical quiet Sun profile but the core emission of Hα and Ca II lines is typical for flares. We tried to find the structure of the flare observed above the sunspot penumbra using the observations of these chromospheric line profiles.
Methods: NLTE radiative transfer techniques allowed us to model the atmosphere of flaring structures and fit both the synthetic Hα and Ca II line profiles to the observed ones. We have derived semiempirical models of the flaring structure observed above sunspots.
Results: Our analysis shows that the flare emission observed within the sunspot penumbra comes from geometrically thin loop-like structures (cool flare loops) located above the fibrils of the penumbra. The structure of the penumbra located below the flare is almost not affected by the flare i.e. the flare emission in Hα and Ca II comes not from the upper chromosphere but from the structures that are higher in the corona. Therefore, a two-component modelling is necessary to reproduce the flare emission above the sunspot penumbra detected in our observations. Title: Hinode, TRACE, SOHO, and Ground-based Observations of a Quiescent Prominence Authors: Heinzel, P.; Schmieder, B.; Fárník, F.; Schwartz, P.; Labrosse, N.; Kotrč, P.; Anzer, U.; Molodij, G.; Berlicki, A.; DeLuca, E. E.; Golub, L.; Watanabe, T.; Berger, T. Bibcode: 2008ApJ...686.1383H Altcode: A quiescent prominence was observed by several instruments on 2007 April 25. The temporal evolution was recorded in Hα by the Hinode SOT, in X-rays by the Hinode XRT, and in the 195 Å channel by TRACE. Moreover, ground-based observatories (GBOs) provided calibrated Hα intensities. Simultaneous extreme-UV (EUV) data were also taken by the Hinode EIS and SOHO SUMER and CDS instruments. Here we have selected the SOT Hα image taken at 13:19 UT, which nicely shows the prominence fine structure. We compare this image with cotemporaneous ones taken by the XRT and TRACE and show the intensity variations along several cuts parallel to the solar limb. EIS spectra were obtained about half an hour later. Dark prominence structure clearly seen in the TRACE and EIS 195 Å images is due to the prominence absorption in H I, He I, and He II resonance continua plus the coronal emissivity blocking due to the prominence void (cavity). The void clearly visible in the XRT images is entirely due to X-ray emissivity blocking. We use TRACE, EIS, and XRT data to estimate the amount of absorption and blocking. The Hα integrated intensities independently provide us with an estimate of the Hα opacity, which is related to the opacity of resonance continua as follows from the non-LTE radiative-transfer modeling. However, spatial averaging of the Hα and EUV data have quite different natures, which must be taken into account when evaluating the true opacities. We demonstrate this important effect here for the first time. Finally, based on this multiwavelength analysis, we discuss the determination of the column densities and the ionization degree of hydrogen in the prominence. Title: Modelling of the Flare Observed Above Sunspot Penumbra Authors: Berlicki, A.; Heinzel, P.; Schmieder, B.; Li, H. Bibcode: 2008ESPM...12.3.19B Altcode: The solar flaring atmosphere above sunspot observed during the event on October 20, 2003 was analysed. Many flaring structures were visible in projection onto the sunspot penumbra. We analysed the H? and Ca II line profiles emitted by the ribbons partially overlapping the sunspots. These observations were performed with the Multi-channel Infrared Solar Spectrograph (MISS) at Purple Mountain Observatory (PMO, China).

In the sunspot penumbra, the line intensity in far wings is lower than in a typical quiet-Sun profile but in the line centre the intensity of H? and Ca II lines is typical for flares. Using 1D approximation we tried to find the vertical structure of the flare observed above sunspot penumbra using the observations of these chromospheric line profiles.

NLTE radiative transfer techniques allowed us to model the atmosphere of flaring structures and fit both the synthetic H? and Ca II line profiles to the observed ones. We have determined semiempirical models of the flaring structure observed above sunspots.

In our analysis we showed that the flare emission observed within sunspot penumbra comes from geometrically thin loop-like structures located above the fibrils of the penumbra. The structure of the penumbra located below the flare is almost not affected by the flare. The flare emission in chromospheric lines comes not from the upper chromosphere but from the structures located higher in the corona. Therefore, we performed two-component modelling which well reproduce the flare emission above sunspot penumbra. In our model of the flaring layer we included the transition region which is necessary to obtain agreement between the observed and calculated line profiles. Title: Prominence and its Coronal Cavity Observed by Hinode, TRACE and SOHO Authors: Schmieder, B.; Heinzel, P.; Schwartz, P.; Gunar, S. Bibcode: 2008ESPM...12.2.95S Altcode: We will first give a definition of what is a prominence according to the glossary of Solar Physicists. A prominence is a filament observed at the limb. A filament lies over the inversion line of photospheric longitudinal magnetic field and is supported in dips of horizontal magnetic field lines. Recent models of flux tubes prove that fine structures of prominences could be represented by vertical structures embedded in dips of horizontal field lines.

Observations of a prominence observed in H? by Hinode/SOT and the solar tower of Meudon show a very high dynamic nature. SUMER spectra in Lyman series show no reverse profiles indicating a large prominence corona transition region.

This prominence is surrounded by a large coronal cavity as show spatial telescopes (TRACE, XRT).

These results will be discussed in term of different formation models. Title: On Lyman-line Asymmetries in Quiescent Prominences Authors: Gunár, S.; Heinzel, P.; Anzer, U.; Schmieder, B. Bibcode: 2008ESPM...12.3.18G Altcode: We present a new study of the asymmetries of synthetic hydrogen Lyman line profiles and suggest the mechanism of their formation.

In order to obtain the synthetic Lyman line profiles, we use multi-thread prominence fine-structure model consisting of identical vertical 2D threads. The 2D thread models are in magnetohydrostatic (MHS) equilibrium, include an empirical prominence-corona transition region (PCTR) and consistently solve the 2D non-LTE radiative transfer. Individual threads of the multi-thread fine-structure model have a randomly assigned LOS velocities.

The synthetic Lyman spectrum obtained by our multi-thread modelling exhibits substantial asymmetries of the line profiles even thought the LOS velocities of individual threads are only of the order of 10 km s-1. Moreover, our results show that the synthetic Lyman-? profiles may exhibit an opposite asymmetry as compared to higher Lyman lines. These results are in agreement with the observed Lyman line profiles from SOHO/SUMER.

The presence and the behaviour of the asymmetrical profiles of the synthetic Lyman spectrum is in agreement with observed profiles taken by SUMER. Title: Solar Prominence Diagnostic with Hinode/EIS Authors: Labrosse, N.; Schmieder, B.; Heinzel, P.; Gunar, S. Bibcode: 2008ESPM...12.2.21L Altcode: We report here on observations of a solar prominence obtained on 26 April 2007 using the Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode. Selected profiles for lines with formation temperatures between log(T)=4.7 and log(T)=6.3 are given and are used to explain the existence of dark features in the raster images. We estimate the contribution of the He II 256.32 Å line in the raster image at 256 Å in the prominence region. We compare the observed prominence profiles with theoretical profiles from non-LTE radiative transfer models and deduce the contribution of resonant scattering in the He II 256 Å emission. Title: Magnetic field changes preceding filament eruptions and coronal mass ejections Authors: Schmieder, B.; Török, T.; Aulanier, G. Bibcode: 2008AIPC.1043..260S Altcode: Solar filaments (or prominences) can be represented by twisted flux ropes in a bipolar magnetic environment. In such models, the dipped field lines of the flux rope carry the filament material and parasitic polarities in the filament channel are responsible for the existence of the lateral feet of filaments. Most filaments eventually erupt, in many cases as part of a coronal mass ejection (CME). Such eruptions are often preceded by detectable changes in the photospheric magnetic field in the vicinity of the filament. We first review recent observations of such changes due to large-scale flows or variations of the background magnetic field, and we discuss their role in eruptions. We then focus on emerging flux in the vicinity of filament channels. It has been suggested that magnetic reconnection between the emerging flux and the pre-existing coronal field can trigger filament eruptions and CMEs. For a particular event, observed with Hinode/XRT, we observe signatures of such reconnection, but no eruption of the filament. We present a numerical simulation of this event and we briefly argue why no eruption took place in this case. Title: Multiple Ribbons of a M1.6 Flare Related to the Magnetic Configuration of the NOAA AR 365 Authors: Chandra, R.; Schmieder, B.; Aulanier, G.; Malherbe, M. J. Bibcode: 2008ESPM...12.2.65C Altcode: The aim of this paper is to understand the magnetic configuration of an active region NOAA 365 and its evolution before and after the occurrence of a M1.6 flare in order to understand the magnetic origin of the flare and its development at particularly the ribbons.

We analyze a M1.6 flare occurring in the active region NOAA 365, using space instruments (SOHO/MDI, EIT, TRACE, RHESSI) as well as ground based instruments i.e. the MSDP spectrograph of the Meudon solar tower. The analysis of the magnetic topology of the region is done by using a force-free field linear extrapolation code of the photospheric field proposed in the database FROMAGE.

Two series of ribbons are identified, signature of the reconnection, the main ribbons in the center of the active region and secondary ribbons at the periphery of the active region. The main ribbons have a `J' shape, typical shape for large emerging flux tube. The secondary ribbons are explained by the magnetic configuration. Title: Topological Departures from Translational Invariance along a Filament Observed by THEMIS Authors: Dudík, J.; Aulanier, G.; Schmieder, B.; Bommier, V.; Roudier, T. Bibcode: 2008SoPh..248...29D Altcode: 2008SoPh..tmp...53D We study the topology of the 3D magnetic field in a filament channel to address the following questions: Is a filament always formed in a single flux tube? How does the photospheric magnetic field lead to filament interruptions and to feet formation? What is the relation between feet-related field lines and the parasitic polarities? What can topological analyses teach us about EUV filament channels? To do so, we consider a filament observed on 6 October 2004 with THEMIS/MTR, in Hα with the full line profile simultaneously and cospatially with its photospheric vector magnetic field. The coronal magnetic field was calculated from a "linear magnetohydrostatic" extrapolation of a composite THEMIS-MDI magnetogram. Its free parameters were adjusted to get the best match possible between the distribution of modeled plasma-supporting dips and the Hα filament morphology. The model results in moderate plasma β≤1 at low altitudes in the filament, in conjunction with non-negligible departures from force-freeness measured by various metrics. The filament here is formed by a split flux tube. One part of the flux tube is rooted in the photosphere aside an observed interruption in the filament. This splitted topology is due to strong network polarities on the edge of the filament channel, not to flux concentrations closer to the filament. We focus our study to the northwest portion of the filament. The related flux tube is highly fragmented at low altitudes. This fragmentation is due to small flux concentrations of two types. First, some locally distort the tube, leading to noticeable thickness variations along the filament body. Second, parasitic polarities, associated with filament feet, result in secondary dips above the related local inversion line. These dips belong to long field lines that pass below the flux tube. Many of these field lines are not rooted near the related foot. Finally, the present model shows that the coronal void interpretation cannot be ruled out to interpret the wideness of EUV filament channels. Title: Large-scale horizontal flows in the solar photosphere. III. Effects on filament destabilization Authors: Roudier, T.; Švanda, M.; Meunier, N.; Keil, S.; Rieutord, M.; Malherbe, J. M.; Rondi, S.; Molodij, G.; Bommier, V.; Schmieder, B. Bibcode: 2008A&A...480..255R Altcode: 2007arXiv0711.3112R Aims:We study the influence of large-scale photospheric motions on the destabilization of an eruptive filament, observed on October 6, 7, and 8, 2004, as part of an international observing campaign (JOP 178).
Methods: Large-scale horizontal flows were investigated from a series of MDI full-disc Dopplergrams and magnetograms. From the Dopplergrams, we tracked supergranular flow patterns using the local correlation tracking (LCT) technique. We used both LCT and manual tracking of isolated magnetic elements to obtain horizontal velocities from magnetograms.
Results: We find that the measured flow fields obtained by the different methods are well-correlated on large scales. The topology of the flow field changed significantly during the filament eruptive phase, suggesting a possible coupling between the surface flow field and the coronal magnetic field. We measured an increase in the shear below the point where the eruption starts and a decrease in shear after the eruption. We find a pattern in the large-scale horizontal flows at the solar surface that interact with differential rotation.
Conclusions: We conclude that there is probably a link between changes in surface flow and the disappearance of the eruptive filament. Title: Magnetic Causes of the Eruption of a Quiescent Filament Authors: Schmieder, B.; Bommier, V.; Kitai, R.; Matsumoto, T.; Ishii, T. T.; Hagino, M.; Li, H.; Golub, L. Bibcode: 2008SoPh..247..321S Altcode: 2007SoPh..tmp..213S During the JOP178 campaign in August 2006, we observed the disappearance of our target, a large quiescent filament located at S25°, after an observation time of three days (24 August to 26 August). Multi-wavelength instruments were operating: THEMIS/MTR ("MulTi-Raies") vector magnetograph, TRACE ("Transition Region and Coronal Explorer") at 171 Å and 1600 Å and Hida Domeless Solar telescope. Counter-streaming flows (+/−10 km s−1) in the filament were detected more than 24 hours before its eruption. A slow rise of the global structure started during this time period with a velocity estimated to be of the order of 1 km s−1. During the hour before the eruption (26 August around 09:00 UT) the velocity reached 5 km s−1. The filament eruption is suspected to be responsible for a slow CME observed by LASCO around 21:00 UT on 26 August. No brightening in Hα or in coronal lines, no new emerging polarities in the filament channel, even with the high polarimetry sensitivity of THEMIS, were detected. We measured a relatively large decrease of the photospheric magnetic field strength of the network (from 400 G to 100 G), whose downward magnetic tension provides stability to the underlying stressed filament magnetic fields. According to some MHD models based on turbulent photospheric diffusion, this gentle decrease of magnetic strength (the tension) could act as the destabilizing mechanism which first leads to the slow filament rise and its fast eruption. Title: Magnetic clouds seen at different locations in the heliosphere Authors: Rodriguez, L.; Zhukov, A. N.; Dasso, S.; Mandrini, C. H.; Cremades, H.; Cid, C.; Cerrato, Y.; Saiz, E.; Aran, A.; Menvielle, M.; Poedts, S.; Schmieder, B. Bibcode: 2008AnGeo..26..213R Altcode: We analyze two magnetic clouds (MCs) observed in different points of the heliosphere. The main aim of the present study is to provide a link between the different aspects of this phenomenon, starting with information on the origins of the MCs at the Sun and following by the analysis of in-situ observations at 1 AU and at Ulysses. The candidate source regions were identified in SOHO/EIT and SOHO/MDI observations. They were correlated with H-α images that were obtained from ground-based observatories. Hints on the internal magnetic field configuration of the associated coronal mass ejections are obtained from LASCO C2 images. In interplanetary space, magnetic and plasma moments of the distribution function of plasma species (ACE/Ulysses) were analyzed together with information on the plasma composition, and the results were compared between both spacecraft in order to understand how these structures interact and evolve in their cruise from the Sun to 5 AU. Additionally, estimates of global magnitudes of magnetic fluxes and helicity were obtained from magnetic field models applied to the data in interplanetary space. We have found that these magnetic characteristics were well kept from their solar source, up to 5 AU where Ulysses provided valuable information which, together with that obtained from ACE, can help to reinforce the correct matching of solar events and their interplanetary counterparts. Title: Magnetic Field Vector Measurements with THEMIS Authors: Bommier, V.; González, M. J. M.; Schmieder, B.; Landi Degl'Innocenti, E. Bibcode: 2008ASPC..383..123B Altcode: The aim of the present work is twofold: a) to validate the Milne-Eddington UNNOFIT inversion by comparing its results with those of the SIR inversion, which is in LTE but does not assumes the Milne-Eddington atmosphere; b) to present a decrease of the network local average magnetic field strength in the vicinity of a filament/prominence, observed before its disppearance, suggesting that the disappearance results from a weakening of the magnetic support. Title: Interaction of magnetic field systems leading to an X1.7 flare due to large-scale flux tube emergence Authors: Li, H.; Schmieder, B.; Song, M. T.; Bommier, V. Bibcode: 2007A&A...475.1081L Altcode: Aims:The aim of this paper is to understand the magnetic configuration and evolution of an active region, which permitted an X1.7 flare to be observed during the decaying phase of a long-duration X1.5 flare on 2005 September 13.
Methods: We performed a multi-wavelength analysis using data from space-borne (Solar and Heliospheric Observatory (SOHO), Transition Region and Coronal Explorer (TRACE), Reuven Ramaty High-Energy Solar Spectroscopic Imager (RHESSI), GOES) and ground-based (the French-Italian THEMIS telescope and the Huairou Video Vector Magnetograph (HVVM)) instruments. We coaligned all the data in order to study the origin of the flare by comparing the observed magnetic field structures with the emissions detected by different instruments.
Results: Reconstructed RHESSI images show three hard X-ray (HXR) sources. In TRACE 195 Å images, two loops are seen: a short bright loop and a longer one. Five ribbons are identified in Hα images, with two of them remnant ribbons of the previous flare. We propose the following scenario to explain the X1.7 flare. A reconnection occurs between the short loop system and the longer loops (TRACE 195 Å). Two X-ray sources could be the footpoints of the short loop, while the third one between the two others is the site of the reconnection. The Hα ribbons are the footprints in the chromosphere of the reconnected loops. During the reconnection, the released energy is principally nonthermal according to the RHESSI energy spectrum analysis (two orders of magnitude higher than the maximum thermal energy). The proposed scenario is confirmed by a nonlinear force-free field (NLFFF) extrapolation, which shows the presence of short sheared magnetic field lines before the eruption and less sheared ones after the reconnection, and the connectivity of the field lines involved in the flaring activity is modified after the reconnection process. The evolution of the photospheric magnetic field over a few days shows the continuous emergence of a large-scale magnetic flux tube, the tongue-shape of the two main polarities of the active region being the signature of such an emergence. After the previous X1.5 flare, the emergence of the tube continues and favors new magnetic energy storage and the onset of the X1.7 flare. Title: Division II / Working Group International Collaboration in Space Weather Authors: Webb, David F.; Gopalswamy, Nat; Liu, William; Sibeck, David G.; Schmieder, Brigitte; Wang, Jingxiu; Wang, Chi Bibcode: 2007IAUTB..26..107W Altcode: The IAU Division II WG on International Collaboration in Space Weather has as its main goal to help coordinate the many activities related to space weather at an international level. The WG currently includes the international activities of the International Heliospheric Year (IHY), the International Living with a Star (ILWS) program, the CAWSES (Climate and Weather of the Sun-Earth System) Working Group on Sources of Geomagnetic Activity, and Space Weather Studies in China. The coordination of IHY activities within the IAU is led by Division II under this working group. The focus of this half-day meeting was on the activities of the IHY program. About 20 people were in attendance. The Chair of the WG, David F. Webb, gave a brief introduction noting that the meeting would have two parts: first, a session on IHY activities emphasizing IHY Regional coordination and, second, a general discussion of the other programs of the WG involving international Space Weather activities. Title: Spectrophotometric analysis of Ellerman bombs in the Ca II, Hα, and UV range Authors: Pariat, E.; Schmieder, B.; Berlicki, A.; Deng, Y.; Mein, N.; López Ariste, A.; Wang, S. Bibcode: 2007A&A...473..279P Altcode: Context: Even if Ellerman bombs have been observed in the Hα line within emerging magnetic flux regions since the early 20th century, their origin and the mechanisms that lead to their formation have been strongly debated. Recently, new arguments in favor of chromospheric magnetic reconnection have been advanced. Ellerman bombs seem to be the signature of reconnections that take place during the emergence of the magnetic field.
Aims: We have observed an active region presenting emergence of magnetic flux. We detected and studied Ellerman bombs in two chromospheric lines: Ca ii 8542 Å and Hα. We investigated the link between Ellerman bombs and other structures and phenomena appearing in an emerging active region: UV bright points, arch filament systems, and magnetic topology.
Methods: On August 3, 2004, we performed multi-wavelength observations of the active region NOAA 10655. This active region was the target of SoHO Joint Observation Program 157. Both SoHO/MDI and TRACE (195 Å and 1600 Å) were used. Simultaneously, we observed in the Ca ii and Na D1 lines with the spectro-imager MSDP mode of THEMIS. Alternately to the MSDP, we used the MTR spectropolarimeter on THEMIS to observe in Hα and in the Fe i doublet at 6302 Å. We derived the magnetic field vectors around some Ellerman bombs.
Results: We present the first images of EBs in the Ca ii line and confirm that Ellerman bombs can indeed be observed in the Ca ii line, presenting the same “moustache” geometry profiles as in the Hα line, but with a narrower central absorption in the Ca ii line, in which the peaks of emission are around ±0.35 Å. We noticed that the Ellerman bombs observed in the wings of Ca ii line have an elongated shape - the length about 50% greater than the width. We derived mean semi-axis lengths of 1.4'' × 2.0''. In the UV time profiles of the Ellerman bombs, we noticed successive enhanced emissions. The distribution of lifetimes of these individual impulses presents a strong mode around 210 s. Study of the magnetic topology shows that 9 out of the 13 EBs are located on the inversion line of the longitudinal field and that some typical examples might be associated with a bald patch topology.
Conclusions: We provide new arguments in favor of the reconnection origin of Ellerman bombs. The different individual impulses observed in UV may be related to a bursty mode of reconnection. We also show that this Ca ii 8542 Å chromospheric line is a good indicator of Ellerman bombs and can bring new information about these phenomena. Title: What can We learn about Filaments from Vector Magnetograms? Authors: Schmieder, B.; Aulanier, G.; Lopez Ariste, A. Bibcode: 2007ASPC..369..137S Altcode: Theoretical MHD models of filaments have predicted the existence of dips in magnetic field lines supporting the cool filament plasma. Condensation would be one of the possible mechanism of filament formation. The controversy is still alive. Filament fine structures are of dynamical nature and injection of cold material (like surges) from the photosphere would be the proposed mechanism. With the presence of dips, the magnetic lines are predicted to be tangent to the photosphere, near the barbs, footpoints of the prominences. The injection model predicted nearly vertical structures of the barbs rooted in the minority polarities.

Measurements of vector magnetic field in filament channels can answer to these questions and will be possible with Solar-B.

Recent results have been obtained with THEMIS vector magnetograph in Tenerife, suggesting that dips are really present in filament channel leading to the conclusion that the observed magnetic topology in the photosphere fully supports models of prominences based on dips. Title: Eruptive and Compact Flares Authors: Schmieder, B.; Aulanier, G.; Delannée, C.; Berlicki, A. Bibcode: 2007AIPC..934...22S Altcode: Solar two ribbon flares are commonly explained by magnetic field reconnections in the high corona. During the reconnection energetic particles (electrons and protons) are accelerated from the reconnection site. These particles are following the magnetic field lines down to the chromosphere. As the plasma density is higher in these lower layers, there are collisions and emission of radiation. Thus after the flare bright ribbons are observed at both ends of loops. These ribbons are typically observed in Hα and in EUV with SoHO and TRACE. As the time is going, these ribbons are expanding away of each other. In most studied models, the reconnection site is an X-point, where two magnetic separatrices intersect. They define four distinct connectivity domains, across which the magnetic connectivity changes discontinuously. In this paper, we present a generalization of this model to 3D complex magnetic topologies where there are no null points, but quasi-separatrices layers instead. In that case, while the ribbons spread away during reconnection, we show that magnetic field lines can quickly slip along them. We propose that this new phenomenon could explain fast extension of Hα and TRACE 1600 Å ribbons, fast moving HXR footpoints as observed by RHESSI, and that it is observed in soft X rays with Hinode/XRT. We also show how this concept can be applied to model the non-wave nature of EIT waves. Title: Properties of prominence fine-structure threads derived from SOHO/SUMER hydrogen Lyman lines Authors: Gunár, S.; Heinzel, P.; Schmieder, B.; Schwartz, P.; Anzer, U. Bibcode: 2007A&A...472..929G Altcode: Context: The SOHO/SUMER observations provide us for the first time with the prominence spectra in the Lyman-α line outside the attenuator together with the higher members of the hydrogen Lyman series.
Aims: We derive the prominence fine-structure thread properties by comparing the SOHO/SUMER hydrogen Lyman series observations with the synthetic Lyman lines.
Methods: To obtain the synthetic profiles of the Lyman lines, we used 2D prominence fine-structure thread models with a PCTR and consistently solved the 2D non-LTE multilevel radiative transfer. The trial-and-error method was applied to find the model with the best agreement between the synthetic Lyman line profiles and the observed ones.
Results: The properties of the resulting model with the best match of the synthetic and observed line profiles are central (minimum) temperature T0 = 7000 K, maximum column mass in the centre of the thread M0 = 1.1×10-4 g cm-2, horizontal field strength in the middle of the thread Bx(0) = 6 Gauss and the boundary pressure p0 = 0.015 dyn cm-2.
Conclusions: The Lyman line profiles observed by SOHO/SUMER can be better reproduced by using multi-thread models consisting of a set of the 2D prominence fine-structure threads placed perpendicularly to the line-of-sight, rather than with the single-thread model. Title: Photospheric flows around a quiescent filament Authors: Rondi, S.; Roudier, Th.; Molodij, G.; Bommier, V.; Keil, S.; Sütterlin, P.; Malherbe, J. M.; Meunier, N.; Schmieder, B.; Maloney, P. Bibcode: 2007A&A...467.1289R Altcode: Context: The horizontal photospheric flows below and around a filament are one of the components in the formation and evolution of filaments. Few studies exist because they require multiwalength time sequences at high spatial resolution.
Aims: Our objective is to measure the horizontal photospheric flows associated with the evolution and eruption of a filament.
Methods: We present observations obtained in 2004 during the international JOP 178 campaign which involved eleven instruments both in space and at ground based observatories. We use TRACE WL, DOT and DST observation to derive flow maps which are then coaligned with intensity images and with the vector magnetic field map obtained with THEMIS/MTR.
Results: Several supergranulation cells cross the Polarity Inversion Line (PIL) and can transport magnetic flux through the PIL, in particular parasitic polarities. We present a detailed example of the formation of a secondary magnetic dip at the location of a filament footpoint. Large-scale converging flows, which could exist along the filament channel and contribute to its formation, are not observed. Before the filament's eruptive phase, we observe both parasitic and normal polarities being swept by a continuously diverging horizontal flow located in the filament gap. The disappearance of the filament initiates in this gap. Such purely horizontal motions could lead to destabilization of the filament and could trigger the sudden filament disappearance. Title: Prominence Parameters from 2D Modeling of Lyman Lines Measured with SUMER Authors: Gunár, S.; Heinzel, P.; Schmieder, B.; Anzer, U. Bibcode: 2007ASPC..368..317G Altcode: We present SOHO/SUMER observations of a solar prominence in the hydrogen Lyman series lines and compare the line profiles with the synthetic ones obtained using our 2D prominence modeling. The observations contain the Ly-β, Ly-γ, and Ly-δ lines on 25 May 2005.

In order to derive the prominence parameters we used our 2D fine structure models of vertical threads in magnetohydrostatic (MHS) equilibrium. By varying the input model parameters (central temperature, boundary pressure, magnetic field, central column mass and turbulent velocity) we obtained a model having the synthetic Lyman line profiles in good agreement with the observed ones. In this way we are able to determine the structure of the magnetic dip and the thermodynamical parameters in the observed prominence. Title: Spectrophotometry of Ellerman Bombs with THEMIS Authors: Pariat, E.; Schmieder, B.; Berlicki, A.; López Ariste, A. Bibcode: 2007ASPC..368..253P Altcode: During coordinated campaigns with THEMIS and space missions (TRACE, SOHO) emerging flux was observed in multi-wavelengths. Ellerman bombs (EBs) have been identified in TRACE 1600 Å and in chromospheric lines. The Hα and Ca II 8542 Å lines present two enhanced emission peaks respectively at 1 Å and at 0.35 Å which are signatures of EBs. Vector magnetic field measured in the photosphere are consistent with previous results indicating the presence of bald-patches under the EBs and consequently the emergence of horizontal flux tubes from below the photosphere. Title: Slip running reconnection in the Sun's atmosphere observed by RHESSI, SOHO, TRACE and Hinode Authors: Schmieder, B.; Aulanier, G.; Démoulin, P.; Pariat, E.; Golub, L. Bibcode: 2007AGUSMSH22A..01S Altcode: Solar double ribbon flares are commonly explained by magnetic field reconnections in the high corona. The bright ribbons, typically observed in Halpha, in EUV with SoHO, TRACE correspond to the ends of the reconnected loops. In most studied cases, the reconnection site is an X-point, where two magnetic separatrices intersect. In this presentation, we show a generalization of this model to 3D complex magnetic topologies where there are no null points, but quasi-separatrices layers instead. In that case, while the ribbons spread away during reconnection, we show that magnetic field lines can quickly slip along them. We propose that this new phenomenon could explain also fast moving HXR footpoints as observed by RHESSI, and that it may be observed in soft X rays with XRT. Title: Non-LTE Analysis of Lyman-Line Observations of a Filament with SUMER Authors: Schwartz, P.; Schmieder, B.; Heinzel, P. Bibcode: 2007ASPC..368..359S Altcode: 2007arXiv0704.3539S We present non-LTE diagnostics of the filament observed by SOHO/SUMER on May 27, 2005 in the whole Lyman series. The filament was situated close to the disk center. The Lα observations were carried out with normal voltage of detector A. The slit was placed at the central part of the detector -- outside the Lα attenuator. Therefore, the observed profiles of this line could be calibrated reliably. Title: Improvement of the Coimbra Spectroheliograph (1988 -- 1992) Authors: Bualé, I.; Mouradian, Z.; Schmieder, B. Bibcode: 2007ASPC..368...15B Altcode: We summarize the parallel modernization of the identical spectroheliographs at Coimbra and Meudon. Title: Spectral Diagnostics of the Magnetic Field Orientation in a Prominence Observed with SOHO/SUMER Authors: Schmieder, B.; Gunár, S.; Heinzel, P.; Anzer, U. Bibcode: 2007SoPh..241...53S Altcode: During several campaigns focused on prominences we have obtained coordinated spectral observations from the ground and from space. The SOHO/SUMER spectrometer allows us to observe, among others, the whole Lyman series of hydrogen, while the Hα line was observed by the MSDP spectrograph at the VTT. For the Lyman lines, non-LTE radiative-transfer computations have shown the importance of the optical thickness of the prominence - corona transition region (PCTR) and its relation to the magnetic field orientation for the explanation of the observed line profiles. Moreover, Heinzel, Anzer, and Gunár (2005, Astron. Astrophys.442, 331) developed a 2D magnetostatic model of prominence fine structures that demonstrates how the shapes of Lyman lines vary, depending on the orientation of the magnetic field with respect to the line of sight. To support this result observationally, we focus here on a round-shaped filament observed during three days as it was crossing the limb. The Lyman profiles observed on the limb are different from day to day. We interpret these differences as being due to the change of orientation of the prominence axis (and therefore the magnetic field direction) with respect to the line of sight. The Lyman lines are more reversed if the line of sight is across the prominence axis as compared to the case when it is aligned along its axis. Title: The dynamic solar chromosphere Authors: Schmieder, B. Bibcode: 2007AIPC..895...49S Altcode: With the new ground-based and space instrumentation observing the solar atmosphere, it is clear nowadays that the quiet sun is of dynamical nature. The Swedish 1m telescope (SST) with its spatial resolution better than 0.2 arc sec. allows us to follow the dynamics of the fine structures observed in photospheric, as well in chromospheric lines. THEMIS with its high magnetic sensitivity reaching 10-5 permits to relate the dynamics of fine structures of spicules and prominences to the small scale magnetic evolution: i.e. canceling and emerging flux. Space instruments (SOHO/MDI, TRACE 1600 Å) observe the activity of the photosphere/chromosphere with high cadence (< 10 sec) and high resolution (larger than 0.5 arc sec).

This review concerns observations of spicules, mottles and filaments obtained in chromospheric lines. The dynamics is obtained by measuring the flows using Dopplershifts and horizontal displacements by time slice methods. The observed velocities are interpreted either by acoustic shock wave or magnetic reconnection models. Title: What is the role of magnetic null points in large flares? Authors: Schmieder, B.; Mandrini, C. H.; Démoulin, P.; Aulanier, G.; Li, H.; Berlicki, A. Bibcode: 2007AdSpR..39.1840S Altcode: We have performed the analysis of the magnetic topology of active region NOAA 10486 before two large flares occurring on October 26 and 28, 2003. The 3D extrapolation of the photospheric magnetic field shows the existence of magnetic null points when using two different methods. We use TRACE 1600 Å and 195 Å brightenings as tracers of the energy release due to magnetic reconnections. We conclude on the three following points: The small events observed before the flares are related to low lying null points. They are long lasting and associated with low energy release. They are not triggering the large flares.

On October 26, a high altitude null point is found. We look for bright patches that could correspond to the signatures of coronal reconnection at the null point in TRACE 1600 Å images. However, such bright patches are not observed before the main flare, they are only observed after it.

On October 28, four ribbons are observed in TRACE images before the X17 flare. We interpret them as due to a magnetic breakout reconnection in a quadrupolar configuration. There is no magnetic null point related to these four ribbons, and this reconnection rather occurs at quasi-separatrix layers (QSLs).

We conclude that the existence of a null point in the corona is neither a sufficient nor a necessary condition to give rise to large flares. Title: New results and future perspectives of THEMIS . Authors: Schmieder, B. Bibcode: 2007MmSAI..78..191S Altcode: We reported on scientific results obtained during the run of two Joint Observing Programs in 2003, 2004 concerning ``New emergence flux and active regions `` (JOP157), ``Filaments and their environment'' (JOP178) and preliminary results of more recent campaigns. Results concerning filament support show the capability of THEMIS/MTR to detect weak magnetic polarities and measure the vector magnetic field curvature. Tangent magnetic field lines to the solar surface were found at the feet of filaments and also in Halpha +/-0.35 Å bright points close to penumbra. The bright points would be not due to high magnetic field concentration (1 KG) but to magnetic reconnection. The stability of filaments could be due to the existence of constant flux in its corridor where overlying arcades are anchored.

The comparison between THEMIS/MSDP and MDI shows the gain that we get. THEMIS is well adapted for measurements of weak field, the noise is much reduce compared to other instruments. For future campaigns we recommand to use alternatively the two modes: MSDP and MTR. Title: Photospheric flows around a quiescent filament and CALAS first results . Authors: Rondi, S.; Roudier, Th.; Molodij, G.; Bommier, V.; Malherbe, J. M.; Schmieder, B.; Meunier, N.; Rieutord, M.; Beigbeder., F. Bibcode: 2007MmSAI..78..114R Altcode: The horizontal photospheric flows below and around a filament are one of the components in the formation and evolution of filaments. Few studies have been done so far because this requires multiwalength time sequences with high spatial resolution. We present observations obtained in 2004 during the international JOP 178 campaign in which eleven instruments were involved, from space and ground based observatories. Several supergranulation cells are crossing the Polarity Inversion Line (PIL) allowing the transport of magnetic flux through the PIL, in particular the parasitic polarities. Before the filament eruptive phase, parasitic and normal polarities are swept by a continuous diverging horizontal flow located in the filament gap where the disappearance of the filament starts. In the future, observations at high spatial resolution on a large field-of-view would be very useful to study filaments, as they are very large structures. We also present the first images obtained with the use of our new 14 MPixel camera CALAS (CAmera for the LArge Scales of the Solar Surface) (10 arcmin× 6.7 arcmin) . These are the first large-scale and high-resolution images of the solar surface ever made. Title: Magnetic Support of Prominences Authors: Schmieder, Brigitte Bibcode: 2007RoAJ...17S..53S Altcode: No abstract at ADS Title: The Gradual Phase of the X17 Flare on October 28, 2003 Authors: del Zanna, G.; Schmieder, B.; Mason, H.; Berlicki, A.; Bradshaw, S. Bibcode: 2006SoPh..239..173D Altcode: 2006SoPh..239..173Z; 2006SoPh..tmp...74Z We present SOHO/CDS observations taken during the gradual phase of the X17 flare that occurred on October 28, 2003. The CDS data are supplemented with TRACE and ground-based observations. The spectral observations allow us to determine velocities from the Doppler shifts measured in the flare loops and in the two ribbon kernels, one hour and a half after the flare peak. Strong downflows (>70 km s-1) are observed along the loop legs at transition-region temperatures. The velocities are close to those expected for free fall. Observations and results from a hydrodynamic simulation are consistent with the heating taking place for a short time near the top of the arcade. Slight upflows are observed in the outer edges of the ribbons (<60 km s-1) in the EUV lines formed at log T < 6.3. These flows could correspond to the so-called “gentle evaporation.” At “flare” temperatures (Fe xix, log T = 6.9), no appreciable flows are observed. The observations are consistent with the general standard reconnection models for two-ribbons flares. Title: Companion Event and Precursor of the X17 Flare on 28 October 2003 Authors: Mandrini, C. H.; Demoulin, P.; Schmieder, B.; Deluca, E. E.; Pariat, E.; Uddin, W. Bibcode: 2006SoPh..238..293M Altcode: 2006SoPh..tmp...79M A major two-ribbon X17 flare occurred on 28 October 2003, starting at 11:01 UT in active region NOAA 10486. This flare was accompanied by the eruption of a filament and by one of the fastest halo coronal mass ejections registered during the October-November 2003 strong activity period. We focus on the analysis of magnetic field (SOHO/MDI), chromospheric (NainiTal observatory and TRACE), and coronal (TRACE) data obtained before and during the 28 October event. By combining our data analysis with a model of the coronal magnetic field, we concentrate on the study of two events starting before the main flare. One of these events, evident in TRACE images around one hour prior to the main flare, involves a localized magnetic reconnection process associated with the presence of a coronal magnetic null point. This event extends as long as the major flare and we conclude that it is independent from it. A second event, visible in Hα and TRACE images, simultaneous with the previous one, involves a large-scale quadrupolar reconnection process that contributes to decrease the magnetic field tension in the overlaying field configuration; this allows the filament to erupt in a way similar to that proposed by the breakout model, but with magnetic reconnection occurring at Quasi-Separatrix Layers (QSLs) rather than at a magnetic null point. Title: Study of an extended EUV filament using SoHO/SUMER observations of the hydrogen Lyman lines Authors: Schwartz, P.; Heinzel, P.; Schmieder, B.; Anzer, U. Bibcode: 2006A&A...459..651S Altcode: Context: .In previous work we determined the 3D structure of an EUV extension of the filament observed by SoHO/CDS on 15 October 1999. The determination of the 3D structure depends on the optical thickness τ912 at the hydrogen Lyman-continuum edge at 912 Å. The τ912 value was unknown, therefore it was taken as a free parameter for the 3D-structure determinations.
Aims: .The plasma properties (including τ912) of this EUV filament are estimated using non-LTE modelling of profiles of the hydrogen Lyman lines.
Methods: .The lines Lβ, Lδ, L ɛ, L6 and L7 were observed by SoHO/SUMER with the slit positioned across the EUV filament. In our modelling the EUV filament was approximated by a horizontal 1D slab with constant pressure and the temperature decreasing vertically from the edges to interior of the slab. The values of the geometrical thickness of the slab in the EUV extension were taken from its 3D structure determined for the τ912 values estimated iteratively. The synthetic profiles were fitted to observed ones using the χ2 minimization.
Results: .For the Hα-filament part we obtained the expected results: a small geometrical thickness between several thousand and 15 000 km, temperatures around 5000 K in the interior and around 20 000 K in PCTRs, and pressure ~0.1~dyn~cm-2. That leads to an optical thickness in the Hα line center larger than 1. In the EUV extension, temperatures of 10 000-40 000 K in the interior and 35 000-50 000 K in the vertically extended PCTRs and a pressure of ~0.01~dyn~cm-2 were determined. Such large variations of the temperature lead to large variations of τ912.
Conclusions: .The EUV extension is inhomogeneous - areas both optically thick and thin at 912 Å are present close to each other. Parts optically thick at 912 Å are visible also in Hα as faint and tiny dark structures around the very dark and well pronounced Hα filament. The volume blocking mechanism is an important mechanism throughout the whole EUV extension even in its optically thick parts. The absorption dominates only in the Hα-filament part of the EUV filament. Title: Evolving Photospheric Flux Concentrations and Filament Dynamic Changes Authors: Schmieder, B.; Aulanier, G.; Mein, P.; Ariste, A. López Bibcode: 2006SoPh..238..245S Altcode: 2006SoPh..tmp...64S We analyze the role of weak photospheric flux concentrations that evolve in a filament channel, in the triggering of dynamic changes in the shape of a filament. The high polarimetric sensitivity of THEMIS allowed us to detect weak flux concentrations (few Gauss) associated with the filament development. The synoptic instruments (MDI, SOLIS) even if their sensitivity is much less than THEMIS were useful to follow any subsequent strengthening of these flux concentrations after their identification in the THEMIS magnetograms. We found that (1) the northern part of the filament develops an Hα barb at the same time that weak minority polarity elements develop near a plage; (2) a section in the southern part of the Hα filament gradually disappears and later reforms at the same time that several mixed-polarity magnetic elements appear, then subsequently cancel or spread away from each other. These changes correspond to increases in EUV emission, as observed by TRACE, EIT, and CDS. This suggests that the plasma is temporarily heated along the filament spine. An idealized sequence of force-free models of this filament channel, based on plasma-supporting magnetic dips occurring in the windings of a very weakly twisted flux tube, naturally explains the evolution of its southern part as being due to changes in the topology of the coronal magnetic field as the photospheric flux concentrations evolve. Title: Magnetic Source Regions of Coronal Mass Ejections Authors: Schmieder, Brigitte Bibcode: 2006JApA...27..139S Altcode: The majority of flare activity arises in active regions which contain sunspots, while Coronal Mass Ejection (CME) activity can also originate from decaying active regions and even so-called quiet solar regions which contain a filament. Two classes of CME, namely flare-related CME events and CMEs associated with filament eruption are well reflected in the evolution of active regions. The presence of significant magnetic stresses in the source region is a necessary condition for CME. In young active regions magnetic stresses are increased mainly by twisted magnetic flux emergence and the resulting magnetic footpoint motions. In old, decayed active regions twist can be redistributed through cancellation events. All the CMEs are, nevertheless, caused by loss of equilibrium of the magnetic structure. With observational examples we show that the association of CME, flare and filament eruption depends on the characteristics of the source regions: - the strength of the magnetic field, the amount of possible free energy storage, - the small- and large-scale magnetic topology of the source region as well as its evolution (new flux emergence, photospheric motions, cancelling flux), and - the mass loading of the configuration (effect of gravity). These examples are discussed in the framework of theoretical models. %k Coronal mass ejection,flare,filament eruption Title: First observation of bald patches in a filament channel and at a barb endpoint Authors: López Ariste, A.; Aulanier, G.; Schmieder, B.; Sainz Dalda, A. Bibcode: 2006A&A...456..725L Altcode: The 3D magnetic field topology of solar filaments/prominences is strongly debated, because it is not directly measureable in the corona. Among various prominence models, several are consistent with many observations, but their related topologies are very different. We conduct observations to address this paradigm. We measure the photospheric vector magnetic field in several small flux concentrations surrounding a filament observed far from disc center. Our objective is to test for the presence/absence of magnetic dips around/below the filament body/barb, which is a strong constraint on prominence models, and that is still untested by observations. Our observations are performed with the THEMIS/MTR instrument. The four Stokes parameters are extracted, from which the vector magnetic fields are calculated using a PCA inversion. The resulting vector fields are then deprojected onto the photospheric plane. The 180° ambiguity is then solved by selecting the only solution that matches filament chirality rules. Considering the weakness of the resulting magnetic fields, a careful analysis of the inversion procedure and its error bars was performed, to avoid over-interpretation of noisy or ambiguous Stokes profiles. Thanks to the simultaneous multi-wavelength THEMIS observations, the vector field maps are coaligned with the Hα image of the filament. By definition, photospheric dips are identifiable where the horizontal component of the magnetic field points from a negative toward a positive polarity. Among six bipolar regions analyzed in the filament channel, four at least display photospheric magnetic dips, i.e. bald patches. For barbs, the topology of the endpoint is that of a bald patch located next to a parasitic polarity, not of an arcade pointing within the polarity. The observed magnetic field topology in the photosphere tends to support models of prominence based on magnetic dips located within weakly twisted flux tubes. Their underlying and lateral extensions form photospheric dips both within the channel and below barbs. Title: Is Pre-Eruptive Null Point Reconnection Required for Triggering Eruptions? Authors: Li, Hui; Schmieder, Brigitte; Aulanier, Guillaume; Berlicki, Arkadiusz Bibcode: 2006SoPh..237...85L Altcode: 2006SoPh..tmp...22L; 2006SoPh..tmp...18L We study the magnetic field evolution and topology of the active region NOAA 10486 before the 3B/X1.2 flare of October 26, 2003, using observational data from the French-Italian THEMIS telescope, the Michelson Doppler Imager (MDI) onboard Solar and Heliospheric Observatory (SOHO), the Solar Magnetic Field Telescope (SMFT) at Huairou Solar Observation Station (HSOS), and the Transition Region and Coronal Explorer (TRACE). Three dimensional (3D) extrapolation of photospheric magnetic field, assuming a potential field configuration, reveals the existence of two magnetic null points in the corona above the active region. We look at their role in the triggering of the main flare, by using the bright patches observed in TRACE 1600 Å images as tracers at the solar surface of energy release associated with magnetic reconnection at the null points. All the bright patches observed before the flare correspond to the low-altitude null point. They have no direct relationship with the X1.2 flare because the related separatrix is located far from the eruptive site. No bright patch corresponds to the high-altitude null point before the flare. We conclude that eruptions can be triggered without pre-eruptive coronal null point reconnection, and the presence of null points is not a sufficient condition for the occurrence of flares. We propose that this eruptive flare results from the loss of equilibrium due to persistent flux emergence, continuous photospheric motion and strong shear along the magnetic neutral line. The opening of the coronal field lines above the active region should be a byproduct of the large 3B/X1.2 flare rather than its trigger. Title: What We Have Learned about Prominences and Filaments from SOHO/SUMER and CDS Spectral Observations Authors: Heinzel, P.; Schmieder, B.; Vial, J. -C. Bibcode: 2006ESASP.617E..65H Altcode: 2006soho...17E..65H No abstract at ADS Title: Importance of Absorption and Volume Blocking for Line Intensity Depression in EUV Filaments Authors: Schwartz, P.; Schmieder, B.; Heinzel, P. Bibcode: 2006ESASP.617E..75S Altcode: 2006soho...17E..75S No abstract at ADS Title: Magnetic Sources of Flares and CMEs from Multi-Wavelength Flare Studies Authors: Schmieder, B.; Mandrini, C.; Berlicki, A.; Démoulin, P.; Li, H. Bibcode: 2006ESASP.617E.145S Altcode: 2006soho...17E.145S No abstract at ADS Title: New perspectives on prominences as observed by SOHO/SUMER Authors: Schmieder, B.; Vial, J. -C.; Heinzel, P. Bibcode: 2006sf2a.conf..563S Altcode: We summarize the results of our prominence and filament studies based on extensive spectral observations with SOHO/SUMER and CDS instruments. During the past decade we have gathered several sets of UV and EUV spectral data, containing various emission lines of different species. Our main objective was to better understand the formation of hydrogen Lyman lines and continuum (using the results of complex non-LTE transfer simulations). However we have also analysed also UV and EUV lines formed under transition-region and coronal conditions. Some highlights of our studies are: reproduction of Lyman-line profiles with partial redistribution, understanding the role of prominence-corona interface in the formation of Lyman-line cores, establishing the effect of the magnetic-field orientation on the shape of Lyman lines, discovery of EUV filament extensions (invisible in the Hα line) and their explanation, reconstruction of a 3D topology of the filament using EUV coronal lines, temperature diagnostics based on measurements of the hydrogen Lyman continuum, proper explanation of a prominence darkening detected in coronal lines. Title: Magnetic Sources of flares and CMEs in October 2003 Authors: Schmieder, B.; Démoulin, P.; Berlicki, A.; Mandrini, C.; Hui, Li Bibcode: 2006sf2a.conf..565S Altcode: We present the data analysis of an observing campaign on October 2003 with the objective of understanding the onset of Coronal Mass Ejections (CME) and solar flares. The magnetic field was observed with THEMIS and MDI, the chromosphere with the MSDP operating on THEMIS, the EUV images with SOHO/EIT and TRACE, the X-rays with RHESSI. Two examples of flares will be presented: the 28 Oct 2003 X17 flare and the 20 October 2003 M1.9 flare. The magnetic field analysis of the active regions is done using a linear-force-free field code. The X17 flare is at the origin of a halo CME while the M1.9 flare has no corresponding CME. Before the X17 flare there was a pre-flare event which allowed to change the connectivities in a first phase and to destabilize the stressed field in a second phase producing the X17 flare. A compact twisted emerging flux was responsible of the M1.9 flare, which remains a compact flare due to very tied overlaying loops. These two examples illustrate the major role of the magnetic configuration involved on the flare physical characteristics. Title: A Multi-Wavelength Study of the Compact M1 Flare on October 22, 2002 Authors: Zanna, G. Del; Berlicki, A.; Schmieder, B.; Mason, H. E. Bibcode: 2006SoPh..234...95Z Altcode: In this paper we present a further study of the Ml class flare observed on October 22, 2002. We focus on the SOHO Coronal Diagnostic Spectrometer (CDS) spectral observations performed during a multi-wavelength campaign with TRACE and ground-based instruments (VTT, THEMIS). Strong blue-shifts are observed in the CDS coronal lines in flare kernels during the impulsive phase of this flare. From a careful wavelength calibration we deduce upflows of 140 km/s for the Fe XIX flare emission, with a pattern of progressively smaller flows at lower temperatures. Large line-widths were observed, especially for the Fe XIX line, which indicate the existence of turbulent velocities. The strong upflows correspond to full shifts of the line profiles. These flows are observed at the initial phase of the flare, and correspond to the "explosive evaporation". The regions of the blueshifted kernels, a few arc seconds away from the flare onset location, could be explained by the chain reaction of successive magnetic reconnections of growing emerging field line with higher and higher overlying field. This interpretation is evidenced by the analysis of the magnetic topology of the active region using a linear force-free-field extrapolation of THEMIS magnetograms. Title: A Multi-Wavelength Study of the Compact M1 Flare on October 22, 2002 Authors: del Zanna, G.; Berlicki, A.; Schmieder, B.; Mason, H. E. Bibcode: 2006SoPh..234...95D Altcode: 2006SoPh..234...95Z In this paper we present a further study of the Ml class flare observed on October 22, 2002. We focus on the SOHO Coronal Diagnostic Spectrometer (CDS) spectral observations performed during a multi-wavelength campaign with TRACE and ground-based instruments (VTT, THEMIS). Strong blue-shifts are observed in the CDS coronal lines in flare kernels during the impulsive phase of this flare. From a careful wavelength calibration we deduce upflows of 140 km/s for the Fe XIX flare emission, with a pattern of progressively smaller flows at lower temperatures. Large line-widths were observed, especially for the Fe XIX line, which indicate the existence of turbulent velocities. The strong upflows correspond to full shifts of the line profiles. These flows are observed at the initial phase of the flare, and correspond to the “explosive evaporation”. The regions of the blueshifted kernels, a few arc seconds away from the flare onset location, could be explained by the chain reaction of successive magnetic reconnections of growing emerging field line with higher and higher overlying field. This interpretation is evidenced by the analysis of the magnetic topology of the active region using a linear force-free-field extrapolation of THEMIS magnetograms. Title: IHY Science and Organization in Europe Authors: Bougeret, J. -L.; Briand, C.; Bonet Navaro, J. A.; Breen, A.; Candidi, M.; Georgevia, K.; Harrison, R.; Marsden, R.; Schmieder, B.; von Steiger, R. Bibcode: 2006cosp...36.3226B Altcode: 2006cosp.meet.3226B We present the scientific and organizational approach to the International Heliophysical Year in Europe A summary is given of the First European General Assembly of the IHY that was held in Paris in January 2006 Initiatives and expected returns are described Title: THEMIS/MSDP magnetic field measurements Authors: Berlicki, A.; Mein, P.; Schmieder, B. Bibcode: 2006A&A...445.1127B Altcode: We present an analysis of longitudinal magnetic field measurements using the spectral data obtained with the French - Italian polarisation free telescope THEMIS working in Multichannel Subtractive Double Pass (MSDP) mode. We also used SOHO/MDI data to extend our analysis. THEMIS observations in the MSDP mode allows us to perform imaging spectropolarimetry characterized by high spatial and time resolution. In our analysis we used the observations of solar active region NOAA 10484 performed on October 20, 2003. From THEMIS 2D spectral images recorded in Na D1 5896 Å line we obtained the longitudinal magnetic field in the active region. The value of the magnetic field was calculated at different distances from the Na D1 line centre. We determine the LOS magnetic field at different heights in the solar atmosphere. SOHO/MDI observations provide the longitudinal magnetic field in Ni I (6768 Å) line. THEMIS/MSDP measurements at Δλ= 0.30 Å are similar to SOHO/MDI results. Gradients of longitudinal magnetic fields derived from MSDP measurements at Δλ= 0.08 and Δλ=0.24 Å exhibit different behaviours according to solar targets. A decrease with height is seen in spot umbrae and penumbrae, while the gradient in facular and network areas suggests a slight increase of the longitudinal magnetic field, which might be explained by the 3D-structure of canopies. Title: Magnetic Topology before a 3B/X1.2 Flare and the Associated CME Authors: Li, H.; Schmieder, B.; Aulanier, G.; Berlicki, A. Bibcode: 2006IAUS..233..399L Altcode: We extrapolated observed photospheric magnetic field before the 3B/X1.2 flare occurred in NOAA 10486 on 2003 October 26. Two magnetic null points exist above the active region, which have no crucial role in triggering the flare, even though enhanced TRACE EUV/UV emission was observed before the main flare due to magnetic reconnection near the lower-altitude null point. We conclude that this flare results from the loss of equilibrium due to persistent flux emergence and photospheric motion, and strong shear. The accompanying fast CME with velocity of ∼ 800 km s^{-1} shows quick mass pickup and energy increase in the low corona. Its kinetic energy is always larger than its potential energy. Title: Multi-wavelength Observations of the solar eruptive activity Authors: Schmieder, Brigitte Bibcode: 2006IAUS..233..472S Altcode: We review what we have learnt about flares and prominences using multi-wavelength observations in the perspective of testing theoretical models. Title: Magnetic reconfiguration before the X 17 Solar flare of October 28 2003 Authors: Schmieder, B.; Mandrini, C. H.; Démoulin, P.; Pariat, E.; Berlicki, A.; Deluca, E. Bibcode: 2006AdSpR..37.1313S Altcode: An active region (AR) NOAA 10486, which produced a large number of X-ray flares during October November 2003, was observed during a multi-wavelength campaign with ground based and space instruments. We focus our analysis on the observations of October 28, 2003. The magnetic field was observed with THEMIS (Na D1) and MDI (Ni I), the chromosphere with THEMIS (Ca II 8542 Å) and with the Meudon heliograph in Hα, the EUV images with SOHO/EIT and TRACE. Two pre-events started just before the major X 17 flare. One was related to localized flux emergence and lasted until the decay phase of the X flare; while the second one involved a large scale quadrupolar reconnection, that we infer by modeling the AR magnetic field. Extended dimming areas across the equator (EIT), large arcades of post-flare loops (TRACE 195 Å) and a halo CME (LASCO) were observed consequently after the flare. We perform an extrapolation of the magnetic field above the photosphere using a linear force-free-field approximation that allows us to find the connectivity among the four polarities that would be involved in the quadrupolar reconnection event. The X 17 flare is plausibly due to the destabilisation of a twisted flux tube, the bottom part of this magnetic structure can be visualized by the presence of a filament. The destabilization is caused by converging and shearing photospheric motions towards the main magnetic inversion line. The large scale quadrupolar reconnection related to the second pre-event would favour the opening of the field above the twisted flux tube and, consequently, the coronal mass ejection. Title: On the origin of the 28 October 2003 X17 event and its companion event Authors: Mandrini, C. H.; Demoulin, P.; Schmieder, B.; de Luca, E. E.; Pariat, E.; Uddin, W. Bibcode: 2006BAAA...49..109M Altcode: An X17 flare started at 11:01 UT on 28 October, 2003, in active region (AR) NOAA 10486. This event was accompanied by a filament eruption and one of the fastest coronal mass ejections (CMEs) observed during the extreme activity period of October-November 2003. Combining chromospheric, coronal and magnetic field data with modeling, we concentrate in the study of two events that started before the X17 flare. One of them, which appears in UV images one hour before the major event, is associated with localized magnetic reconnection occurring at a magnetic mull point. T his event lasts as long as the X17 flare and our analysis indicates that it is independent of it. The other one, visible in Hα and UV images and simultaneous with the previous one, is related to a large scale quadrupolar reconnection process. This process is similar to the one proposed by the breakout model for the initiation of CMEs, but it takes place at quasiseparatrices and not in null points. These results will be published in Solar Physics. Title: Emergence of undulatory magnetic flux tubes by small scale reconnections Authors: Pariat, E.; Aulanier, G.; Schmieder, B.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2006AdSpR..38..902P Altcode: With Flare Genesis Experiment (FGE), a balloon borne observatory launched in Antarctica on January 2000, series of high spatial resolution vector magnetograms, Dopplergrams, and Hα filtergrams have been obtained in an emerging active region (AR 8844). Previous analyses of this data revealed the occurence of many short-lived and small-scale H α brightenings called 'Ellerman bombs' (EBs) within the AR. We performed an extrapolation of the field above the photosphere using the linear force-free field approximation. The analysis of the magnetic topology reveals a close connexion between the loci of EBs and the existence of "Bald patches" (BP) regions (BPs are regions where the vector magnetic field is tangential to the photosphere). Some of these EBs/BPs are magnetically connected by low-lying field lines, presenting a serpentine shape. This results leads us to conjecture that arch filament systems and active regions coronal loops do not result from the smooth emergence of large scale Ω-loops, but rather from the rise of flat undulatory flux tubes which get released from their photospheric anchorage by reconnection at BPs, which observational signature is Ellerman bombs. Title: The International Heliophysical Year in France Authors: Schmieder, B. Bibcode: 2006cosp...36..978S Altcode: 2006cosp.meet..978S We are preparing in France the anniversary of IGY 50 We are gathering our efforts around few actions 1 We planned to follow the international campaigns with our solar Telescope THEMIS in Tenerife with the spacecrafts SOHO Cluster and the magnetometers of Superdarn A group is already formed with C Hanuise as responsible to understand some physical processes involved in these phenomena by using former data 2 On the initiative of CAWSES SCOSTEP program we plan to rehabilitate our heliograph in Meudon in order to be able to participate to the international network of flare survey The Japonese are leading this program Shibata and Kurokawa 3 We are developping lectures for students in different places in France We planned to work on the development of a DVD and video games in a IHY European context 4 We have also an outreach program which consists of an exhibition This exibition could be duplicated in France and for French speaking countries Title: The role of null points in large flares Authors: Schmieder, B.; Mandrini, C.; Démoulin, P.; Aulanier, G.; Li, H. Bibcode: 2006cosp...36..156S Altcode: 2006cosp.meet..156S We have performed the analysis of the magnetic topology of the active region NOAA 10486 before two large flares occurring on October 26 and 28 2003 The 3D extrapolation of photospheric magnetic field show the existence of magnetic null points We used TRACE 1600 A brightenings as tracers of the energy release during magnetic reconnections We conclude on the three following points 1 The observed small pre-events observed before the flares were related to low lying null points They were long lasting and associated with low energy release They were not triggering of the large flares 2 On October 26 a high altitude null point was detected We looked at the TRACE 1600 A images for bright patches corresponding to a possible coronal reconnection at the null point However no bright patch was observed before the main flare 3 On October 28 a breakout of the large scale overlaying magnetic field lines occurred but without the presence of a null point in the corona So the existence of a null point in the corona is not a sufficient and or necessary condition for getting large flares Title: Active Region Magnetic Field Observed with Themis/msdp and Soho/mdi Instruments Authors: Berlicki, A.; Mein, P.; Schmieder, B. Bibcode: 2005ESASP.600E..57B Altcode: 2005ESPM...11...57B; 2005dysu.confE..57B No abstract at ADS Title: Multi-Wavelength Analysis of Plasma Flows during Solar Flares Authors: Berlicki, A.; Schmieder, B.; Heinzel, P.; Li, H.; Del Zanna, G.; Rudawy, P. Bibcode: 2005ESASP.600E..58B Altcode: 2005dysu.confE..58B; 2005ESPM...11...58B No abstract at ADS Title: A Multi-Wavelength Study of the 3B/X1.2 Flare Observed on 2003 October 26 Authors: Li, Hui; Li, Jian-Ping; Fang, Cheng; Schmieder, Brigitte; Berlicki, Arkadiusz; Du, Qiu-Sheng Bibcode: 2005ChJAA...5..645L Altcode: We report results from a multi-wavelength study of the 3B/X1.2 two-ribbon disk flare (S15E44), which was well observed by both ground-based and space-borne instruments. Two pairs of conjugate kernels K1 and K4, and K2 and K3 in the Hα images are identified. These kernels are linked by two different systems of EUV loops. K1 and K4 correspond to the two 17 GHz and 34 GHz microwave sources observed by the Nobeyama Radioheliograph (NoRH), while K2 and K3 have no corresponding microwave sources. Optical spectroscopic observations suggest that all the four kernels are possible precipitating sites of non-thermal electrons. Thus the energy of electron deposited in K2 and K3 should be less than 100 keV. Two-dimensional distributions of the full widths at half maximum (FWHM) of the Hα profiles and the line-of-sight (LOS) velocities derived from the Ca II 8542 Å profiles indicate that the largest FWHM and LOS velocity tends to be located near the outer edges of Hα kernels, which is consistent with the scenario of current two-ribbon flare models and previous results. When non-thermal electron bombardment is present, the observed Hα and Ca II 8542 Å profiles are similar to previous observational and theoretical results, while the He I 10830 Å profiles are different from the theoretical ones. This puts some constraints on future theoretical calculation of the He I 10830 Å line. Title: Non-Lte Modelling of the EUV Filament Based on Soho/sumer Observations of the Hydrogen Lyman Lines Authors: Schwartz, P.; Heinzel, P.; Schmieder, B. Bibcode: 2005ESASP.600E..97S Altcode: 2005dysu.confE..97S; 2005ESPM...11...97S No abstract at ADS Title: Observation of Small Scale Reconnection Role in Undulated Flux Tube Emergence Authors: Pariat, E.; Aulanier, G.; Schmieder, B.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2005ESASP.596E..34P Altcode: 2005ccmf.confE..34P No abstract at ADS Title: Observational Evidence of Photoshperic Magnetic Dips in Filament Channels Authors: Schmieder, B.; López Ariste, A.; Aulanier, G. Bibcode: 2005ESASP.596E..19S Altcode: 2005ccmf.confE..19S No abstract at ADS Title: Flows and Heating of the Solar Atmosphere during Solar Flares Authors: Schmieder, B.; Berlicki, A.; Li, H.; Del Zanna, G.; Mason, H. Bibcode: 2005ESASP.592..543S Altcode: 2005soho...16E.102S; 2005ESASP.592E.102S No abstract at ADS Title: Thermal and non-thermal effects driven by magnetic reconnections observed in a confined flare Authors: Li, H.; Berlicki, A.; Schmieder, B. Bibcode: 2005A&A...438..325L Altcode: In order to better understand the energy processes occurring during the impulsive phase of solar flares we compare observations with our magnetic model calculations. We study the 1N/M1.9 confined flare of 20 October 2003 observed during a Joint Observation Program (JOP157), and concentrate on the spectral analysis of the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI). These X-ray observations are combined with those from the Solar and Heliospheric Observatory (SOHO) instruments, the French Italian magnetograph (THEMIS), and the Multi-channel Infrared Solar Spectrograph (MISS). The flare occurred in a complex active region, NOAA 10484, with a δ configuration. For model calculations we extrapolate magnetic field lines, which allows us to understand the magnetic topology of the region. This topology and the long impulsive phase of the flare with numerous peaks (GOES, RHESSI) suggest multiple magnetic field reconnection processes. The RHESSI images show a bright structure in hard X-rays (HXR) that could be the tops of the loops. We measure a significant displacement of this structure between the two main maxima of emission, which infers different sites for the reconnection process. The energy release processes can be understood by analyzing the RHESSI spectra using different models. First, using the thermal plus broken power law non-thermal component, we derive the low energy cutoff for the power law distribution of the high-energy electrons (≈25 keV). Then, we apply two models (thermal plus thick-target and thermal plus thin-target non-thermal component) that allow us to fit the observations. These two models lead to similar results; non-thermal energy contributes a significant amount (approximately 20%) of the total flare energy only during the first peak of the impulsive phase. This suggests that the energy that heats the chromosphere is transported mainly by thermal conduction. The temperature of the thermal plasma is 34 MK and 20 MK at the first and second peaks, respectively. Title: Non-LTE diagnostics of velocity fields during the gradual phase of a solar flare Authors: Berlicki, A.; Heinzel, P.; Schmieder, B.; Mein, P.; Mein, N. Bibcode: 2005A&A...430..679B Altcode: We perform an analysis of the velocity field within the Hα ribbons during the gradual phase of an M 1.0 solar flare observed on October 22, 2002. We use spectroscopic observations performed with the German VTT (Vacuum Tower Telescope) working in the MSDP (Multichannel Subtractive Double Pass spectrograph) observing mode. From these observations the Hα line profiles in chosen areas of the flare ribbons were reconstructed and these observational profiles were compared with a grid of synthetic Hα line profiles calculated by the non-LTE radiative-transfer code. This code allows us to calculate different models of the chromosphere with a prescribed velocity field. By optimising the best fit between the observed and synthetic profiles we find the most appropriate models of the chromosphere and vertical structure of the velocity field in the analysed areas of the flare ribbons. By means of the non-LTE radiative-transfer calculations we show that in most analysed areas of the Hα flare ribbons the chromospheric plasma exhibited upward motion with a mean velocity of a few km;s-1. These results are consistent with previous estimates and support the scenario of a gentle evaporation during the gradual phase. Title: Source Regions of Coronal Mass Ejections Authors: Schmieder, Brigitte; van Driel-Gesztelyi, L. Bibcode: 2005IAUS..226..149S Altcode: The majority of flare activity arises in active regions which contain sunspots, while CME activity can also originate from decaying active regions and even so-called quiet solar regions which contain a filament. Two classes of CME, namely flare-related CME events and CMEs associated with filament eruption are well reflected in the evolution of active regions, flare related CMEs mainly occur in young active regions containing sunspots and as the magnetic flux of active region is getting dispersed, the filament-eruption related CMEs will become dominant. This is confirmed by statistical analyses.</p>All the CMEs are, nevertheless, caused by loss of equilibrium of the magnetic structure. With observational examples we show that the association of CME, flare and filament eruption depends on the characteristics of the source regions: (i) the strength of the magnetic field, the amount of possible free energy storage, (ii) the small- and large-scale magnetic topology of the source region as well as its evolution (new flux emergence, photospheric motions, canceling flux), and (iii) the mass loading of the configuration (effect of gravity). These examples are discussed in the framework of theoretical models. Title: Flux tube emergence, from photosphere to corona Authors: Pariat, E.; Schmieder, B.; Aulanier, G. Bibcode: 2004sf2a.conf..103P Altcode: 2004sf2a.confE.339P From a campaign of multi-wavelength observations of an emerging active region, we have studied the dynamics of the solar atmosphere due to this emergence and the magnetic field topology of the active region. In addition with the observations obtained with Yohkoh, SOHO and TRACE, a balloon borne 80 cm telescope (Flare Genesis Experiment) provided us a series of high spatial resolution vector magnetograms. For the first time we highlight that magnetic flux tubes do not directly emerge with a large Omega-loop shape, as suggest the TRACE observations of the corona, but rather within an undulatory shape. We demonstrated that the resistive Parker instability allows the flux tube to go through the low atmosphere.

This result has been obtained by performing an extrapolation of the field above the active region. Title: Resistive Emergence of Undulatory Flux Tubes Authors: Pariat, E.; Aulanier, G.; Schmieder, B.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2004ApJ...614.1099P Altcode: During its 2000 January flight, the Flare Genesis Experiment observed the gradual emergence of a bipolar active region, by recording a series of high-resolution photospheric vector magnetograms and images in the blue wing of the Hα line. Previous analyses of these data revealed the occurrence of many small-scale, transient Hα brightenings identified as Ellerman bombs (EBs). They occur during the flux emergence, and many of them are located near moving magnetic dipoles in which the vector magnetic field is nearly tangential to the photosphere. A linear force-free field extrapolation of one of the magnetograms was performed to study the magnetic topology of small-scale EBs and their possible role in the flux emergence process. We found that 23 out of 47 EBs are cospatial with bald patches (BPs), while 15 are located at the footpoints of very flat separatrix field lines passing through distant BPs. We conclude that EBs can be due to magnetic reconnection, not only at BP locations, but also along their separatrices, occurring in the low chromosphere. The topological analysis reveals, for the first time, that many EBs and BPs are linked by a hierarchy of elongated flux tubes showing aperiodic spatial undulations, whose wavelengths are typically above the threshold of the Parker instability. These findings suggest that arch filament systems and coronal loops do not result from the smooth emergence of large-scale Ω-loops from below the photosphere, but rather from the rise of undulatory flux tubes whose upper parts emerge because of the Parker instability and whose dipped lower parts emerge because of magnetic reconnection. EBs are then the signature of this resistive emergence of undulatory flux tubes. Title: Evolution and magnetic topology of the M 1.0 flare of October 22, 2002 Authors: Berlicki, A.; Schmieder, B.; Vilmer, N.; Aulanier, G.; Del Zanna, G. Bibcode: 2004A&A...423.1119B Altcode: In this paper we analyse an M 1.0 confined flare observed mainly during its gradual phase. We use the data taken during a coordinated observational campaign between ground based instruments (THEMIS and VTT) and space observatories (SoHO/CDS and MDI, TRACE and RHESSI). We use these multi-wavelength observations to study the morphology and evolution of the flare, to analyse its gradual phase and to understand the role of various heating mechanisms. During the flare, RHESSI observed emission only within the 3-25 keV spectral range. The RHESSI spectra indicate that the emission of the flare was mainly of thermal origin with a small non-thermal component observed between 10 and 20 keV. Nevertheless, the energy contained in the non-thermal electrons is negligible compared to the thermal energy of the flaring plasma. The temperature of plasma obtained from the fitting of the RHESSI X-ray spectra was between 8.5 and 14 MK. The lower temperature limit is typical for a plasma contained in post flare loops observed in X-rays. Higher temperatures were observed during a secondary peak of emission corresponding to a small impulsive event. The SoHO/CDS observations performed in EUV Fe XIX line also confirm the presence of a hot plasma at temperatures similar to those obtained from RHESSI spectra. The EUV structures were located at the same place as RHESSI X-ray emission. The magnetic topology analysis of the AR coming from a linear force-free field extrapolation explains the observed features of the gradual phase of the flare i.e. the asymmetry of the ribbons and their fast propagation. The combination of the multi-wavelength observations with the magnetic model further suggests that the onset of the flare would be due to the reconnection of an emerging flux in a sheared magnetic configuration. Title: Magnetic changes observed in the formation of two filaments in a complex active region: TRACE and MSDP observations Authors: Schmieder, Brigitte; Mein, Nicole; Deng, Yuanyong; Dumitrache, Cristiana; Malherbe, Jean-Marie; Staiger, Joachim; Deluca, E. E. Bibcode: 2004SoPh..223..119S Altcode: This paper is focused on the formation of two filaments in a complex center of decaying active regions (AR 8329 and AR 8326), located in the northern hemisphere. The observations were obtained in Hα by the Multi-channel Subtractive Double Pass spectrograph (MSDP mounted on the German telescope VTT in Tenerife) and EUV lines with TRACE (Transition Region And Corona Explorer). High Doppler shifts are found to be related to the ends of filament segments where canceling magnetic fields are also located (as seen on magnetograms from Big Bear Solar Observatory). At these locations, velocities along the line of sight, derived by using a cloud model method reach −20 km s−1, the segments of filaments merge and frequently a time-related sub-flare is observed by TRACE. The chirality of the filament segments has been determined by different methods: the segments of dextral chirality join together and form a long dextral filament, and a single filament of sinistral chirality forms end to end with the dextral filament but does not merge with it. Assuming a model of twisted flux tube for filament material, we suggest that the dextral filament has negative helicity and a relationship between its formation and the close by sunspot with the same sign of helicity. Title: Determination of the 3D structure of an EUV-filament observed by SoHO/CDS, SoHO/SUMER and VTT/MSDP Authors: Schwartz, P.; Heinzel, P.; Anzer, U.; Schmieder, B. Bibcode: 2004A&A...421..323S Altcode: Heinzel et al. (\cite{hein1}) found that filaments seem to be much more extended in EUV spectral lines than in Hα. In this paper we reconstruct the 3D structure of the extensions of the EUV-filament observed on 15 October 1999 by SoHO/CDS and SoHO/SUMER. Small Hα structures were observed by VTT/MSDP. We computed the bottom and top heights of the EUV-filament extensions for several values of the hydrogen Lyman-continuum optical thickness τ912 using the spectroscopic model of Heinzel et al. (\cite{hein2}). For this we used CDS observations of the two coronal lines Mg X 624.94 Å and Si XII 520.60 Å. Further, we develop a new method for estimating τ912 using the O V line measured by CDS and the O VI measured by SUMER onboard SoHO. The latter line is used as a proxy to deduce the intensity variations of O V underneath the filament. This method also takes into account the presence of prominence-corona transition regions.

Resulting heights of the EUV-filament extensions are around 15 000 km for the bottom and around 40 000 km for the top boundaries. However, there are significant variations around these representative values and we show that in about half of observed pixels the Lyman-continuum absorption dominates in the coronal-line depression, while in the other half it is the volume blocking effect. The latter situation corresponds to a large (larger than 30 000 km) geometrical thickness of the EUV-filament extension. From the heights of the boundaries of the EUV-filament the geometrical thickness can be computed and used to estimate the total mass loading which was found to be comparable to that of typical CMEs. Title: Multi-wavelength study of a high-latitude EUV filament Authors: Schmieder, Brigitte; Lin, Yong; Heinzel, Petr; Schwartz, Pavol Bibcode: 2004SoPh..221..297S Altcode: A large filament was observed during a multi-wavelength coordinated campaign on June 19, 1998 in the Hα line with the Swedish Vacuum Solar Telescope (SVST) at La Palma, in the coronal lines Fe ix/x 171 Å and Fe xi 195 Å with the Transition Region and Coronal Explorer (TRACE) and in EUV lines with the SOHO/CDS spectrometer and the hydrogen Lyman series with the SOHO/SUMER spectrometer. Because of its high-latitude location, it is possible to disentangle the physical properties of the Hα filament and the filament channel seen in EUV lines. TRACE images point out a dark region fitting the Hα fine-structure threads and a dark corridor (filament channel), well extended south of the magnetic inversion line. A similar pattern is observed in the CDS EUV-line images. The opacity of the hydrogen and helium resonance continua at 171 Å is almost two orders of magnitude lower than that at the Hi head (912 Å) and thus similar to the opacity of the Hα line. Since we do not see the filament channel in Hα, this would imply that it should also be invisible in TRACE lines. Thus, the diffuse dark corridor is interpreted as due to the coronal `volume blocking' by a cool plasma which extends to large altitudes. Such extensions were also confirmed by computing the heights from the projection geometry and by simulations of the CDS and TRACE line intensities using the spectroscopic model of EUV filaments (Heinzel, Anzer, and Schmieder, 2003). Finally, our NLTE analysis of selected hydrogen Lyman lines observed by SUMER also leads to a conclusion that the dark filament channel is due to a presence of relatively cool plasma having low densities and being distributed at altitudes reaching the Hα filament. Title: Emerging Flux and the Heating of Coronal Loops Authors: Schmieder, B.; Rust, D. M.; Georgoulis, M. K.; Démoulin, P.; Bernasconi, P. N. Bibcode: 2004ApJ...601..530S Altcode: We use data collected by a multiwavelength campaign of observations to describe how the fragmented, asymmetric emergence of magnetic flux in NOAA active region 8844 triggers the dynamics in the active-region atmosphere. Observations of various instruments on board Yohkoh, SOHO, and TRACE complement high-resolution observations of the balloon-borne Flare Genesis Experiment obtained on 2000 January 25. We find that coronal loops appeared and evolved rapidly ~6+/-2 hr after the first detection of emerging magnetic flux. In the low chromosphere, flux emergence resulted in intense Ellerman bomb activity. Besides the chromosphere, we find that Ellerman bombs may also heat the transition region, which showed ``moss'' ~100% brighter in areas with Ellerman bombs as compared to areas without Ellerman bombs. In the corona, we find a spatiotemporal anticorrelation between the soft X-ray (SXT) and the extreme ultraviolet (TRACE) loops. First, SXT loops preceded the appearance of the TRACE loops by 30-40 minutes. Second, the TRACE and SXT loops had different shapes and different footpoints. Third, the SXT loops were longer and higher than the TRACE loops. We conclude that the TRACE and the SXT loops were formed independently. TRACE loops were mainly heated at their footpoints, while SXT loops brightened in response to coronal magnetic reconnection. In summary, we observed a variety of coupled activity, from the photosphere to the active-region corona. Links between different aspects of this activity lead to a unified picture of the evolution and the energy release in the active region. Title: Multi-wavelength flare study and magnetic configuration Authors: Schmieder, Brigitte; Berlicki, A.; Vilmer, N.; Aulanier, G.; Démoulin, P.; Mein, P.; Mandrini, C.; Deluca, E. Bibcode: 2004IAUS..223..397S Altcode: 2005IAUS..223..397S Recent results of two observation campaigns (October 2002 and October 2003) are presented with the objective of understanding the onset of flares and CMEs. The magnetic field was observed with THEMIS and MDI, the chromosphere with the MSDP operating on the German telescope VTT and on THEMIS, the EUV images with SOHO/CDS and TRACE, the X-ray with RHESSI. We show how important is the magnetic configuration of the active region to produce CMEs using two examples: the October 28 2003 X 17 flare and the October 22 2002 M 1.1 flare. The X 17 flare gave a halo CME while the M 1.1 flare has no corresponding CME. The magnetic topology analysis of the active regions is processed with a linear-force-free field configuration. Title: Multi-Wavelength Observations of an M1.0 Flare on 22 October 2002 Authors: Berlicki, A.; Schmieder, B.; Vilmer, N.; Mein, P.; Mein, N.; Heinzel, P.; Staiger, J.; Deluca, E. E. Bibcode: 2004IAUS..219..669B Altcode: No abstract at ADS Title: Emerging Flux and the Heating of Coronal Loops Authors: Schmieder, B.; Démoulin, P.; Rust, D. M.; Georgoulis, M. K.; Bernasconi, P. N. Bibcode: 2004IAUS..219..483S Altcode: 2003IAUS..219E..18S We suggest that coronal loop heating is caused by dissipation of magnetic energy as new magnetic flux emerges from the photosphere. Based on data from a multi wavelength campaign of observations during the flight of the Flare Genesis Experiment we describe how emergence of flux from the photosphere appears directly to heat the corona to 2-3 MK. Following intense heating the loops cool and become visible through the filters of the TRACE (Transition Region and Coronal Explorer)instrument at one million degrees. We determine the relaxation time of the cooling and compare it withtheoretical heating functions. The proposed mechanism is well accepted in flare loops but we suggest that the mechanism is generally valid and helps to explain the visibility of active region loops in transition region lines. Title: H-alpha spectral observations of the X17+ solar flare on 28 october 2003 Authors: Radziszewski, K.; Rudawy, P.; Schmieder, B.; Berlicki, A. Bibcode: 2004cosp...35.1248R Altcode: 2004cosp.meet.1248R In this paper we present the results of H-alpha observations of the giant X17+ GOES class solar flare on 28 October 2003. The observational data were collected with the Large Coronagraph and MSDP spectrograph of the Astronomical Observatory of Wroclaw University (Poland). During the nearly 3.5 hours of observations we have collected 176 scans covering the whole flaring region (200 000 x 240 000 km2). After the standard data reduction we have obtained quasi-monochromatic 2D images of the flare as well as H-alpha line profiles (+/-0.12 nm) for all pixels of the images. The temporal resolution of our data is equal to about 50 second; the spatial resolution is of the order of 1 second of arc. In this paper we present the main properties of the H-alpha flare: translations of the flare kernels, motion of the matter along the arcade of the H-alpha loops, comparison of the H-alpha structures with ones observed in UV by TRACE and SOHO as well as with magnetograms and numerical models of the magnetic fields and emission of the flaring kernels. Title: Emergence of undulatory magnetic flux tubes by small scale reconnections Authors: Pariat, E.; Aulanier, G.; Schmieder, B.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2004cosp...35.1482P Altcode: 2004cosp.meet.1482P With Flare Genesis Experiment (FGE), a balloon borne observatory launched in Antarctica on January 2000, series of high spatial resolution vector magnetograms, Dopplergrams, and Hα filtergrams have been obtained in an emerging active region (AR 8844). Previous analyses of this data revealed the occurence of many short-lived and small-scale Hα brightenings called 'Ellerman bombs' (EBs) within the AR. We performed an extrapolation of the field above the photosphere using the linear force-free field approximation. The analysis of the magnetic topology reveals a close connexion between the loci of EBs and the existence of ``Bald patches'' regions (BPs are regions where the vector magnetic field is tangential to the photosphere). Among 47 identified EBs, we found that 23 are co-spatial with a BP, while 19 are located at the footpoint of very flat separatrix field lines passing throught a distant BP. We reveal for the first time that some of these EBs/BPs are magneticaly connected by low-lying lines, presenting a 'sea-serpent' shape. This results leads us to conjecture that arch filament systems and active regions coronal loops do not result from the smooth emergence of large scale Ω loops, but rather from the rise of flat undulatory flux tubes which get released from their photospheric anchorage by reconnection at BPs, whose observational signature is Ellerman bombs. Title: Flare evolution and magnetic configuration study Authors: Berlicki, A.; Schmieder, B.; Aulanier, G.; Vilmer, N.; Yan, Y. H. Bibcode: 2004cosp...35.2200B Altcode: 2004cosp.meet.2200B We will present the analysis of M1.0 confined flare emission and evolution in the context of the topology of the coronal magnetic field. This flare was observed in NOAA 0162 on 22 October 2002. The multiwavelength data were taken during a coordinated observational campaign between ground based instruments and space observatories. The photospheric line-of-sight magnetic field observations were obtained with THEMIS and SOHO/MDI. We used these data to perform linear force-free field extrapolation of magnetic field into the corona. Our extrapolation provides an explanation of the appearance of H-alpha flare ribbons. An elongated shape of X-ray emission observed by Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) also follow the predicted shape of extrapolated field lines. Moreover, the X-ray emission observed by RHESSI permit to see thermal emission of coronal loops heated probably by non-thermal electrons, accelerated during the reconnection processes. The presence of non-thermal particles can be deduced from RHESSI X-ray spectra reconstructed during the gradual phase of the flare. On Huairou vector magnetograms of the AR we see that there was strong shear between one of main negative spot and the north small positive spot. The extrapolation with non-constant alpha force-free field model did not obtain any loop to connect these two spots. Title: Climate and weather of the Sun-Earth system: CAWSES Authors: Schmieder, B.; Vincent, B.; Baumjohann, W.; Ono, T.; Basu, S.; Lean, J. Bibcode: 2004AdSpR..34..443S Altcode: SCOSTEP's mission is to implement research programs in solar-terrestrial physics that can benefit from international participation and involve at least two of its participating ICSU bodies. Some past SCOSTEP programs have been comprehensive in nature such that virtually all of SCOSTEP's energy was dedicated to the implementation of one large program. Examples of these were SCOSTEP's STEP program in 1990-1995, the MAP program in 1982-1985, and the IMS in 1976-1979. This document sets forth the case for a major future SCOSTEP program called CAWSES (Climate and Weather of the Sun-Earth System), to be implemented in the period 2004-2008. Title: Magnetic configuration reorganisation before the X 17 flare of October28 2003 Authors: Schmieder, B.; Mandrini, C.; Demoulin, P.; Mein, P. Bibcode: 2004cosp...35.1528S Altcode: 2004cosp.meet.1528S The active region NOAA 0486 was observed during a multi-wavelength campaign with ground based and space instruments. We analyse the magnetic configuration of the region during a pre-event, which reorganizes the magnetic connectivities of the field lines before the occurence of a X17 flare of October 28 2003. The magnetic field was observed with THEMIS and MDI, the chromosphere with the MSDP operating on on THEMIS and with the Meudon heliograph, the EUV images with SOHO/CDS and TRACE. The X17 flare gave a halo CME while the M1.9 flare has no corresponding CME. The magnetic field analysis of the active regions is performed by using a linear-force-free field code. The pre-flare event before the X17 flare change the connectivities in a first phase and allows the stressed field to relax in a second phase producing the X17 flare. Title: Multiwavelength determination of the density and total mass of the EUV filament observed by SoHO/CDS, SoHO/SUMER and MSDP/VTT Authors: Schwartz, P.; Schmieder, B.; Heinzel, P.; Anzer, U. Bibcode: 2004IAUS..223..219S Altcode: 2005IAUS..223..219S It was found that filaments observed in EUV could be much more extended than in Halpha. These extended dark structures visible in EUV are named EUV filaments. Their parts seen only in EUV (not observable in Halpha because of low opacity at the Halpha wavelength) are called EUV-filament extensions (or simply EUV extensions). For the EUV filament observed by SoHO on 15 October 1999 as northern polar crown filament, only a few small dark structures were seen in Halpha. This suggests that the mass of the EUV extension is larger than, or at least comparable with, the mass of the parts of the filament observed in Halpha. In our previous work we determined the 3D structure of the EUV extension of this EUV filament. In this paper we present the determinations of mass and average density of this EUV extension. For better density estimates we interpret the hydrogen Lyman lines observed by SUMER using non-LTE radiative transfer code. From the best fitting of Lyman lines we obtained a reasonable model of the EUV extension with low gas pressure, temperatures from 2times10^4 K to 10^5 K and with extended prominence-corona transition regions. Title: Climate and weather of the Sun Earth system: CAWSES Authors: Schmieder, B.; Basu, S. Bibcode: 2003ESASP.535..701S Altcode: 2003iscs.symp..701S During 2004-2008, CAWSES (Climate and Weather of the Sun-Earth System), SCOSTEP's new international scientific program, will link the world's scientists in a cooperative effort to study the entire interactive Sun-Earth system. This new program seeks to mobilize the international solar-terrestrial science community to fully utilize past, present and future data; to produce improvements in space weather forcasting, design of space- and Earth-based technological systems, and understanding the role of solar-terrestrial influence on Global Change. The CAWSES Science Steering Group with its 7 members (chairman: S. Basu) has organized around four themes: Solar Influence on Climate (chairman: M. Lockwood) Space Weather: Science and applications (chairmen: J. Kozyra, T. Shibata) Atmospheric Coupling Processes (chairman: F. J. Luebken) Space Climatology (chairman: C. Frohlich). A forum is open on the web site for all comments and discussions about the different projects of CAWSES. Title: A Spectroscopic Model of euv Filaments Authors: Heinzel, P.; Anzer, U.; Schmieder, B. Bibcode: 2003SoPh..216..159H Altcode: We propose a new spectroscopic model for extended dark structures around Hα filaments observed in EUV lines. As in previous papers, we call these structures EUV filaments. Our model uses at least three observed EUV lines (located shortward the hydrogen Lyman-continuum limit) to compute iteratively the altitudes at which the EUV filament extensions are located. A transition-region line (O v in the present case) can be used to derive the opacity of the Lyman continuum and the other two coronal lines (e.g., Mg x and Si xii) then give two heights: the bottom and top of the EUV filament. The method takes into account self-consistently the absorption of EUV-line radiation by the Lyman continuum, as well as the volume-blocking effect potentially important for coronal lines. As an example we compute the heights of the EUV filament at one particular position, using CDS data for the 5 May 2000 filament. At this position, the EUV filament extension lies between altitudes 28 700 and 39 000 km, so that the geometrical thickness of the structure is 10300 km (we discuss also the sensitivity of our models to variations of the line intensities). These heights are consistent with the concept of twisted magnetic flux tubes, but there could be also some influence on our results due to additional low lying cool structures from parasitic polarities. Title: Determination of the 3D-topology of an EUV-filament observed by SoHO/CDS SoHO/SUMER and VTT/MSDP Authors: Schwartz, P.; Heinzel, P.; Schmieder, B.; Anzer, U. Bibcode: 2003ESASP.535..495S Altcode: 2003iscs.symp..495S We have constructed a spatial model of an extended EUV-filament observed on 15 October 1999 (polar crown N 38 deg) by SoHO/CDS. The narrow Hα counterparts were observed by VTT/MSDP. As found in 2001, EUV-filaments are much more extended than those parts visible in Hα. We have computed the bottom and top heights of this EUV-filament for the whole CDS raster for different values of the Lyman-continuum optical thickness using CDS measurements of two coronal lines (Mg X 624.94 Å and Si XII 520.60 Å) and the model of Heinzel et al., 2003. For the scale height of the MgX line we used the value from Fludra et al. 1999, assuming that this line is not solar cycle and activity dependent. We created a new method for τ912 determination from O VI and O V line intensities. Because of the inhomogeneity in the O V 629.37 Å line intensity distribution in the vicinitiy of the EUV-filament it was not possible to estimate this intensity under the filament. So we used observations made by SoHO/SUMER of the O VI 1031.91 Å line not absorbed by EUV-filament cold plasma. The knowledge of the heights of the bottom and top boundaries of an EUV-filament gives us the EUV-filament geometrical thickness. From this the mass of the EUV-filament was computed. Title: Foreword (Solar variability as an input to the Earth's environment) Authors: Wu, T.; Obridko, V.; Schmieder, B.; Sykora, J. Bibcode: 2003ESASP.535D..17W Altcode: 2003iscs.sympD..17W No abstract at ADS Title: EUV-filaments and their mass loading Authors: Heinzel, P.; Anzer, U.; Schmieder, B.; Schwartz, P. Bibcode: 2003ESASP.535..447H Altcode: 2003iscs.symp..447H It was found recently (Heinzel et al., 2001; Schmieder et al., 2003) that solar filaments observed in EUV lines by SOHO/CDS are much more extended than their Hα counterparts. This was explained by a large difference between the hydrogen Lyman-continuum and Hα opacities. Two different MHD models were suggested to explain the EUV-filament extensions: the model based on parasitic polarities (Aulanier & Schmieder, 2002) and the model with twisted flux tubes (Anzer & Heinzel, 2003). The latter model can explain our recent findings that at least some parts of the EUV-filament extensions are located relatively high in the corona. These heights can be computed using a new spectroscopic model of EUV-filaments. The mass which is loaded into the EUV-filament extensions is then estimated on the basis of non-LTE transfer calculation. The total filament mass is larger than that derived for the Hα filament itself and this may have consequences for the structure and mass loading of CMEs whenever they form from such filaments - this may answer the question how the extended CME structures can form from rather narrow Hα filaments. We summarize the basic properties of EUV-filaments, present their spectroscopic analysis and give some estimates for mass loading. We then discuss possible relations between EUV-filaments and CMEs, in particular the problems of their masses. Title: Spectroscopic diagnostics of an Hα and EUV filament observed with THEMIS and SOHO Authors: Schmieder, B.; Tziotziou, K.; Heinzel, P. Bibcode: 2003A&A...401..361S Altcode: A long filament has been observed with THEMIS/MSDP and SOHO/CDS - SUMER, during a coordinated campaign (JOPs 131/95) on May 5, 2000. The data were (a) 2-D Hα spectra, observed using THEMIS, (b) Lyman series spectra and Lyman continuum, observed using SOHO/SUMER, and (c) EUV spectra (in O V 629 Å, Mg X 624 Å, Si Xii 520 Å, Ca X 557 Å and He I 584 Å) observed using SOHO/CDS. A large depression of the line emissions in CDS images represents the EUV filament. A computed model shows that the EUV filament consists of an extended in height cloud of low gas pressure at an altitude lower than the top of the Hα filament, volume-blocking and absorbing coronal emission and absorbing transition region line emission. The optical thickness of the Lyman continuum is estimated by using the ratio of O V intensity inside and outside the EUV filament, while the optical thickness of Hα is computed from the Hα line profile by using an inversion technique. Using simultaneous Hα , Lyman lines and Lyman continuum spectroscopic data, we performed detailed, non-LTE radiative transfer diagnostics of the filament plasma conditions. The optical thickness of the Lyman continuum is larger than that of the Hα line by one to two orders of magnitude. This could be of a great importance for filament formation modeling, if we consider that more cool material exists in filament channels but is optically too thin to be visible in Hα images. Title: What can we learn from lfff magnetic extrapolations Authors: Schmieder, B.; Aulanier, G. Bibcode: 2003AdSpR..32.1875S Altcode: Observations of the Sun is done, up to now, in 2D and magnetic field is measured mainly in the photosphere. Magnetic extrapolation techniques allow us nevertheless to have a 3D view of the magnetic field. Different methods are available today. We present in this paper interesting and exploitable results obtained with linear force-free-field methods (lfff). The α parameter is assumed to be constant in the whole volume of computations. The results concern the global potential field in the corona (e.g. example of transequatorial loops), the magnetic topology of flaring active regions (e.g. flares and bald patch regions), twisted magnetic fields in filaments, and magnetic reconnection in emerging active region (e.g. Ellerman Bombs). We discuss on the limits of the validity of the methods. Title: Flare Genesis Experiment: magnetic topology of Ellerman bombs Authors: Schmieder, B.; Pariat, E.; Aulanier, G.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2002ESASP.506..911S Altcode: 2002svco.conf..911S; 2002ESPM...10..911S Flare Genesis Experiment (FGE), a balloon borne Observatory was launched in Antarctica on January 10, 2000 and flew during 17 days. FGE consists of an 80 cm Cassegrain telescope with an F/1.5 ultra-low-expansion glass primary mirror and a crystalline silicon secondary mirror. A helium-filled balloon carried the FGE to an altitude of 37 km (Bernasconi et al. 2000, 2001). We select among all the observations a set of high spatial and temporal resolution observations of an emerging active region with numerous Ellerman bombs (EBs). Statistical and morphology analysis have been performed. We demonstrate that Ellerman bombs are the result of magnetic reconnection in the low chromosphere by a magnetic topology analysis. The loci of EBs coincide with "bald patches" (BPs). BPs are regions where the vector field is tangential to the boundary (photosphere) along an inversion line. We conclude that emerging flux through the photosphere is achieved through resistive emergence of U loops connecting small Ω loops before rising in the chromosphere and forming Arch Filament System (AFS). Title: Spectral diagnostics of the magnetic field orientation in a round-shaped filament Authors: Schmieder, B.; Mein, N.; Heinzel, P.; Anzer, U. Bibcode: 2002ESASP.506..469S Altcode: 2002ESPM...10..469S; 2002svco.conf..469S During several campaigns focused on prominences we have obtained coordinated spectral observations from the ground and from space. The SOHO/SUMER spectrometer allows us to observe, among others, the whole Lyman series of hydrogen, while the Hα line was observed by the MSDP spectrograph at the VTT. For Lyman lines, the non-LTE radiative-transfer computations have shown the importance of the prominence-corona transition region (PCTR) and its relation to the magnetic field orientation for the explanation of the observed line profiles (Schmieder et al. 1998, Heinzel et al. 2001). Moreover, Heinzel and Anzer (2001) developed new 2D models which demonstrate how the shapes of Lyman lines vary depending on the orientation of the magnetic field with respect to the line of sight. To confirm this result observationally, we focus here on a round-shaped filament observed during three days as it was crossing the limb. The Lyman profiles observed on the limb are different from day to day and we interpret these differences by the change of orientation of the prominence axis (and therefore the magnetic field direction) with respect to the line-of-sight. Title: Statistics, morphology, and energetics of Ellerman bombs Authors: Georgoulis, Manolis K.; Rust, David M.; Bernasconi, Pietro N.; Schmieder, Brigitte Bibcode: 2002ESASP.505..125G Altcode: 2002IAUCo.188..125G; 2002solm.conf..125G We have performed a detailed analysis of several hundreds Hα Ellerman bombs in the low chromosphere, above an emerging flux region. We find that Ellerman bombs may be small-scale, low-altitude, magnetic reconnection events that heat the low chromosphere in the active region. Their energy content varies between 1027 erg and 1028 erg, typical of sub-flaring activity. Title: Magnetic cancellation and small-scale activity in an AR filament Authors: Schmieder, B.; Engvold, O.; Yong, Lin; Deng, Y. Y.; Mein, N. Bibcode: 2002ESASP.505..223S Altcode: 2002solm.conf..223S; 2002IAUCo.188..223S A long set of observations obtained with the VTT/MSDP spectrograph in September 1998 (8 to 11) allows us to follow the formation of a complex filament in and around a nest of active regions during its disk passage. Continuous shear of magnetic field in this region can explain the formation and the relative stability of the filament structure before the occurrence of a flare which leads to important changes in the magnetic configuration. The corona overlying the region and the flare, as well, is observed by TRACE. The studied filament is stable on long term time scale. However, high spatial and temporal observations obtained in La Palma (SVST) show high Doppler shifts and strong transverse motions of absorbing blobs along the filament. These velocities are directly related to magnetic activity as observed with the SVST. A small scale magnetic analysis shows emergence of MMFs (Moving Magnetic Features) around a decaying sunspot and canceling flux with the neighbor network. Magnetic reconnection could occur and explain the ejection of blobs along the new magnetic field lines. Formation of the transient blobs is discussed. Title: Vector magnetic field observations of flux tube emergence Authors: Schmieder, B.; Aulanier, G.; Pariat, E.; Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N. Bibcode: 2002ESASP.505..575S Altcode: 2002IAUCo.188..575S; 2002solm.conf..575S With Flare Genesis Experiment (FGE), a balloon borne Observatory high spatial and temporal resolution vector magnetograms have been obtained in an emerging active region. The comparison of the observations (FGE and TRACE) with a linear force-free field analysis of the region shows where the region is non-force-free. An analysis of the magnetic topology furnishes insights into the existence of "bald patches" regions (BPs are regions where the vector field is tangential to the boundary (photosphere) along an inversion line). Magnetic reconnection is possible and local heating of the chromopshere is predicted near the BPs. Ellerman bombs (EBs) were found to coincide with few BPs computed from a linear force-free extrapolation of the observed longitudinal field. But when the actual observations of transverse fields were used to identify BPs, then the correspondence with EB positions improved significantly. We conclude that linear force-free extrapolations must be done with the true observed vertical fields, which require the measurement of the three components of the magnetic field. Title: Filament activation and magnetic reconnection Authors: Deng, Yuanyong; Lin, Yong; Schmieder, Brigitte; Engvold, OddbjØrn Bibcode: 2002SoPh..209..153D Altcode: A curved filament in a decaying active region (AR 8329) was observed on 9 September 1998 with a combination of several instruments. The main data base is a 4-hour long time series of 1 min cadence using the Lockheed tunable filter mounted in the Swedish Vacuum Solar Tower in La Palma (SVST). Filtergrams obtained at several wavelength positions in Hα images are used to derive Doppler images. Interleaved images in the magnetic sensitive Fe i 6302.5 Å line yield corresponding magnetograms. Supplementing observations are collected from TRACE and the French Multi-Channel Double Pass spectrograph (MSDP) mounted in the German VTT in Tenerife. The filament, which consists of several discrete fragments with nearly horizontal fine structures, undergoes activity and counter-streaming bulk flow, but without erupting. The magnetic field inversion line of this active region is complex and strongly influenced by intrusion of a positive polarity area in a following negative polarity of the region. The positive polarity area contains a small sunspot surrounded by moving magnetic features (MMFs). The MMFs interact directly with the parasitic polarities in the filament channel, and thereby gives rise to merging and canceling magnetic flux. When the interaction occurs at the location of the feet (`barbs') of the filament notable activations are observed (ejection of `blobs'). The ejections of `blobs' are preceded by twist of filament threads and the `blobs' move along downward bending field lines towards the photosphere close to the sound speed. Title: The Structure and Evolution of a Sigmoidal Active Region Authors: Gibson, S. E.; Fletcher, L.; Del Zanna, G.; Pike, C. D.; Mason, H. E.; Mandrini, C. H.; Démoulin, P.; Gilbert, H.; Burkepile, J.; Holzer, T.; Alexander, D.; Liu, Y.; Nitta, N.; Qiu, J.; Schmieder, B.; Thompson, B. J. Bibcode: 2002ApJ...574.1021G Altcode: Solar coronal sigmoidal active regions have been shown to be precursors to some coronal mass ejections. Sigmoids, or S-shaped structures, may be indicators of twisted or helical magnetic structures, having an increased likelihood of eruption. We present here an analysis of a sigmoidal region's three-dimensional structure and how it evolves in relation to its eruptive dynamics. We use data taken during a recent study of a sigmoidal active region passing across the solar disk (an element of the third Whole Sun Month campaign). While S-shaped structures are generally observed in soft X-ray (SXR) emission, the observations that we present demonstrate their visibility at a range of wavelengths including those showing an associated sigmoidal filament. We examine the relationship between the S-shaped structures seen in SXR and those seen in cooler lines in order to probe the sigmoidal region's three-dimensional density and temperature structure. We also consider magnetic field observations and extrapolations in relation to these coronal structures. We present an interpretation of the disk passage of the sigmoidal region, in terms of a twisted magnetic flux rope that emerges into and equilibrates with overlying coronal magnetic field structures, which explains many of the key observed aspects of the region's structure and evolution. In particular, the evolving flux rope interpretation provides insight into why and how the region moves between active and quiescent phases, how the region's sigmoidicity is maintained during its evolution, and under what circumstances sigmoidal structures are apparent at a range of wavelengths. Title: The role of magnetic bald patches in surges and arch filament systems Authors: Mandrini, C. H.; Démoulin, P.; Schmieder, B.; Deng, Y. Y.; Rudawy, P. Bibcode: 2002A&A...391..317M Altcode: The short-lived active region (AR) NOAA 7968 was thoroughly observed all along its disk transit (June 3 to 10, 1996) from space and from the ground. During the early stage of its evolution, flux emerged in between the two main polarities and arch filament systems (AFS) were observed to be linked to this emergence. New bipoles and a related surge were observed on June 9. We have modeled the magnetic configuration of AR 7968 using a magnetohydrostatic approach and we have analyzed its topology on June 6 and June 9 in detail. We have found that some of the AFS and the surge were associated with field lines having dips tangent to the photosphere (the so called ``bald patches'', BPs). Two interacting BP separatrices, defining a separator, have been identified in the configuration where these very different events occurred. The observed evolution of the AFS and the surge is consistent with the expected results of magnetic reconnection occuring in this magnetic topology, which is specific to 3D configurations. Previously BPs have been found to be related to filament feet, small flares and transition region brightenings. Our results are evidence of the importance of BPs in a much wider range of phenomena, and show that current layers can be formed and efficiently dissipated in the chromosphere. Title: Statistics, Morphology, and Energetics of Ellerman Bombs Authors: Georgoulis, Manolis K.; Rust, David M.; Bernasconi, Pietro N.; Schmieder, Brigitte Bibcode: 2002ApJ...575..506G Altcode: We investigate the statistical properties of Ellerman bombs in the dynamic emerging flux region NOAA Active Region 8844, underneath an expanding arch filament system. High-resolution chromospheric Hα filtergrams (spatial resolution 0.8"), as well as photospheric vector magnetograms (spatial resolution 0.5") and Dopplergrams, have been acquired by the balloon-borne Flare Genesis Experiment. Hα observations reveal the first ``seeing-free'' data set on Ellerman bombs and one of the largest samples of these events. We find that Ellerman bombs occur and recur in preferential locations in the low chromosphere, either above or in the absence of photospheric neutral magnetic lines. Ellerman bombs are associated with photospheric downflows, and their loci follow the transverse mass flows on the photosphere. They are small-scale events, with typical size 1.8"×1.1" , but this size depends on the instrumental resolution. A large number of Ellerman bombs are probably undetected, owing to limited spatial resolution. Ellerman bombs occur in clusters that exhibit fractal properties. The fractal dimension, with an average value ~1.4, does not change significantly in the course of time. Typical parameters of Ellerman bombs are interrelated and obey power-law distribution functions, as in the case of flaring and subflaring activity. We find that Ellerman bombs may occur on separatrix, or quasi-separatrix, layers, in the low chromosphere. A plausible triggering mechanism of Ellerman bombs is stochastic magnetic reconnection caused by the turbulent evolution of the low-lying magnetic fields and the continuous reshaping of separatrix layers. The total energies of Ellerman bombs are estimated in the range (1027, 1028) ergs, the temperature enhancement in the radiating volume is ~2×103 K, and the timescale of radiative cooling is short, of the order of a few seconds. The distribution function of the energies of Ellerman bombs exhibits a power-law shape with an index ~-2.1. This suggests that Ellerman bombs may contribute significantly to the heating of the low chromosphere in emerging flux regions. Title: Photospheric Vertical Current Density and Overlying Atmospheric Activity in an Emerging Flux Region Authors: Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N.; Schmieder, B. Bibcode: 2002AAS...200.2004G Altcode: 2002BAAS...34..673G Using high-resolution vector magnetograms obtained by the balloon-borne Flare Genesis Experiment (FGE), we construct maps of the vertical current density in the emerging flux region NOAA 8844. The vertical current density has been decomposed into components that are field-aligned and perpendicular to the magnetic field, thus allowing a straightforward identification of force-free areas, as well as of areas where the force-free approximation breaks down. Small-scale chromospheric activity, such as H α Ellerman bombs and Ultraviolet bright points in 1600 Åshow a remarkable correlation with areas of strong current density. Simultaneous data of overlying coronal loops, observed by TRACE in the Extreme Ultraviolet (171 Åand 195 Å), have been carefully co-aligned with the FGE photospheric maps. We find that the footpoints of the TRACE loops always coincide with strong vertical currents and enhancements of the current helicity density. We also investigate whether the force-free approximation is valid on the photosphere during various evolutionary stages of the active region. Title: The magnetic nature of wide EUV filament channels and their role in the mass loading of CMEs Authors: Aulanier, G.; Schmieder, B. Bibcode: 2002A&A...386.1106A Altcode: Previous works have shown that dark and wide EUV filament channels observed at lambda < 912 Å, are due to absorption of EUV lines in cool plasma condensations that are not observed in Hα . We extend this interpretation and we address the issue of the possible injection of their mass into CMEs, through the magneto-hydrostatic modeling in 3D of one filament observed both in Hα and in EUV. The model parameters are fixed so as to match the Hα observations only. Further comparison of the model with the EUV observations reveal the magnetic nature of the absorbing plasma condensations. They are formed in magnetic dips, as for the filament itself. Opacity ratios and the hydrostatic condition imply that the dips must be filled by cool material up to 1700 km, which increases the filament mass by 50% as compared to Hα estimations. Far from the filament, the absorbing condensations are located below 4 Mm in altitude above the photosphere, on the edge of weak photospheric parasitic polarities, within the lower parts of long field lines overlaying the filament. By physical analogy with Hα filament feet, we redefined these extended regions as EUV feet. The broadening of the EUV filament channel is dominated by EUV feet, while the larger filling of dips plays a non-negligible but minor role. Further implications from this work are discussed, on the visibility and the geometry of the condensations, on the existence of EUV filament channels in the absence of filaments, on the loading of cool material into filament feet through bald patch reconnection and on the complex geometry of the upper prominence-corona transition region. The magnetic topology implies that during the filament eruption, the mass of its wide EUV feet will not contribute to the CME, whereas the extra mass provided by the large filling of dips in the filament flux tube will be loaded into the CME. Title: Foreword (SOLSPA 2001) Authors: Schmieder, Brigitte; Smaldone, Luigi Bibcode: 2002ESASP.477D..15S Altcode: 2002scsw.confD..15S No abstract at ADS Title: Climate and weather of the Sun-Earth system: CAWSES, SCOSTEP's program for 2003-2008 Authors: Schmieder, B.; Vincent, B.; Baumjohann, W.; Ono, T.; Basu, S.; Lean, L. Bibcode: 2002ESASP.477...59S Altcode: 2002scsw.conf...59S SCOSTEP's mission is to implement research programs in solar-terrestrial physics that can benefit from international participation and involve at least two of its participating and involve at least two of its participating ICSU bodies. Some past SCOSTEP programs have been comprehensive in nature such that virtually all of SCOSTEP's energy was dedicated to the implementation of one large program. Examples of these were SCOSTEP's STEP program in 1990-95, the MAP program in 1982-85, and the IMS in 1976-79. This document sets forth the case for a major future SCOSTEP program called CAWSES (Climate and Weather of the Sun-Earth System), to be implemented in the period 2003-2008. Title: Magnetic build-up and precursors of CMEs Authors: van Driel-Gesztelyi, Lidia; Schmieder, Brigitte; Poedts, Stefaan Bibcode: 2002ESASP.477...47V Altcode: 2002scsw.conf...47V CMEs are fundamentally magnetic phenomena, thus to improve CME forecast we have to find out more about the characteristics of the small and large-scale magnetic field in and around their source region prior to CME occurrence. In this paper we show examples of the magnetic evolution of CME-prolific active regions using SOHO/MDI data. It appears that CMEs are preceded by magnetic evolution during which the helicity of the source region is increasing due to twisted flux emergence, shearing motions between opposite polarity footpoints of subsequently emerging bipoles and, in a smaller extend, by the differential rotation acting on the emerged flux. Furthermore, we find short-term magnetic precursors of CME events, typically a combination of major flux emergence, cancellation and fast shearing motions in active regions with strong concentrated magnetic fields prior to flare-related CMEs and small-scale cancellation events along the magnetic inversion line in decayed active regions with low magnetic flux density prior to filament eruption-related CMEs. We make an overview of recent studies on magnetic helicity and suggest that such analyses will be able to provide a key to unlock the secrets of CME buildup and initiation. Title: The characteristics of microwave burst source and energy budget in disappering filament Authors: Tang, Y. H.; Schmieder, B.; Fang, C. Bibcode: 2002AdSpR..29.1461T Altcode: On 7 May, 1992 a complex event with the disappearence of a filament and a two ribbon flare was well observed in Hα filtergrams, Yorkoh soft X-ray data, and radio data. This event is studied by using the flare-filament current model. The momentum equation and the energy equation of the filament current have been solved. By using the measured time variation of the filament height, the corresponding evolution of the current intensity and the total energy of the current filament were computed. The magnetic field strength and the energy flux of energetic electrons in the source region of microwave bursts have also been estimated by using the microwave spectrum. During the main phase, the mean magnetic strength and the energy flux of energetic electrons are about 300-400G and 1 × 10 11 erg cm -2s -1, respectively. By using these physical parameters, the energy budget has been made. These results show that the flare of 7 May, 1992 may be the result of reconnection of current sheet beneath the disappearing filament and the flare energy is provided by current filament. Title: Energetics of the 18 May 1994 brightening event Authors: Tang, Y. H.; Li, Y. N.; Fang, C.; Schmieder, B.; Aulanier, G.; Demoulin, P. Bibcode: 2002AdSpR..30..557T Altcode: By using YOHKOH soft X-ray images, vector magnetograms and Hα filtergrams, the energetics of the brightening event of May 18, 1994 has been studied. It occurred in a nearly potential magnetic configuration as shown by the comparison between the magnetic extrapolation(linear force free field) and the large scale soft X-ray loops. This event is related to the emergence of a new magnetic flux. The brightening points of Hα and soft X-ray are located at computed separatrices associated with field lines which are tangent to the photosphere. This brightening may be a signature of reconnection taking place between the pre-existing non-potential loops and the new emerging small loops. The magnetic energy provided by reconnection is likely to be stored in the non-potential loops and shearing emerging flux. A phenomenological model is offered. Title: Climate and Weather of the Sun Earth system:SCOSTEP s program for 2004- 2008 Authors: Schmieder, B.; Vincent, B.; Baumjohann, W.; Ono, T.; Basu, S.; Lean, L. Bibcode: 2002cosp...34E.139S Altcode: 2002cosp.meetE.139S Research in the past decade has produced significant improvements in understanding the physical processes within each of the Sun-Earth domains, and enabled crossdisciplinary progress in understanding the domain as a whole.SCOSTEP's mission is to implement research programs in solar-terrestrial physics that can benefit from international participation and involve at least two of its participating ICSU bodies. Some past SCOSTEP programs have been comprehensive in nature such that virtually all of SCOSTEP's energy was dedicated to the implementation of one large program. Examples of these were SCOSTEP's STEP program in 1990-95, the MAP program in 1982-85, and the IMS in 1976-79. This document sets forth the case for a major future SCOSTEP program called CAWSES (Climate and Weather of the Sun-Earth System), to be implemented in the period 2004-2008. Climate implies long-term studies Title: Surges y Arch Filament Systems: Una topología inusual Authors: Mandrini, C. H.; Démoulin, P.; Schmieder, B.; Deng, Y. Y.; Rudawy, P. Bibcode: 2002BAAA...45...17M Altcode: Active region (AR) NOAA 7968 was observed during its solar disk transit by several instruments on ground and on board satellites (Yohkoh and SOHO). During its emergence Arch Filament Systems (AFS) linking the polarities of the main bipole were observed. During its decay a surge (a chromospheric confined mass ejection) occurred to the South of the positive polarity of this bipole. We model the AR magnetic field in the magnetohydrostatic approach and compute its topology. We find that the evolution of both events, AFS and surge, agrees with magnetic field reconnection occurring in field lines that are tangentially touching the photosphere. These lines define the so called ``bald patches'' (BPs). In previous studies these topological structures have been found to be related to small flares and transition region brightenings. Our results point out the importance of BPs in a wider phenomenological context and show that current sheets can develop and efficiently dissipate in the chromosphere. Title: What can we learn from magnetic extrapolation above active region and filament? Authors: Schmieder, B.; Aulanier, G. Bibcode: 2002cosp...34E.458S Altcode: 2002cosp.meetE.458S Observations of the Sun is done up to now in 2D. Magnetic extrapolation technique allows us to have a 3D view of the magnetic field lines. Global 3D structures can be visualized by using such computations. Assuming linear force-free-field configuration we have analyzed different active regions and filaments. In the lfff approximation thevalue is constant for all the field lines and is chosen in order to give the best global or local fit to the structures projected on the solar surface observed in H, in UV lines (EIT, TRACE) or in X rays (Yohkoh/SXT). With some examples we will show some important results that we have obtained: 1. the existence of a vertical gradient of the magnetic shear above active region with filament (Schmieder et al 1996). 2. the existence of the same value offitting the sheared filament and the spiral structure around a sunspot, the existence of dips in the magnetic field strength at the location of the filament channel in an AR (Schmieder et al 1991). 3. the validity of chirality laws with dextral/sinistral filaments and negative /positiveparameter according to the hemisphere (Aulanier et al 1999, 2000, Aulanier and Schmieder 2002) Title: Minutes of the 33rd JOSO Board Meeting - 2001 Authors: Cauzzi, G.; Kucera, A.; Schmieder, B. Bibcode: 2002joso.book...15C Altcode: No abstract at ADS Title: Climate and Weather of The Sun Earth System Authors: Schmieder, B.; Vincent, B.; Baumjohann, W.; Ono, T.; Basu, S.; Lean, J. Bibcode: 2002EGSGA..27..250S Altcode: SCOSTEP's mission is to implement research programs in solar-terrestrial physics that can benefit from international participation and involve at least two of its par- ticipating ICSU bodies. Some past SCOSTEP programs have been comprehensive in nature such that virtually all of SCOSTEP's energy was dedicated to the implemen- tation of one large program. Examples of these were SCOSTEP's STEP program in 1990-95, the MAP program in 1982-85, and the IMS in 1976-79. This document sets forth the case for a major future SCOSTEP program called CAWSES (Climate and Weather of the Sun-Earth System), to be implemented in the period 2003-2008. Title: Minutes of the 32nd JOSO Board Meeting - 2000 Authors: Cauzzi, G.; Kucera, A.; Schmieder, B. Bibcode: 2002joso.book...10C Altcode: No abstract at ADS Title: JOSO national report 2000-2001 - France Authors: Schmieder, B.; Mein, P.; Lemaire, P.; Pick, M.; Vilmer, N. Bibcode: 2002joso.book...56S Altcode: We report on the scientific advances in solar physics in France. The French Solar community is large split in different laboratories and observatories. We report on specific groups (THEMIS, SOHO, Nançay). Title: Evolution of the source region of the interplanetary magnetic cloud of 18-20 Oct. 1995 Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Baranyi, T. Bibcode: 2002AdSpR..29.1489V Altcode: We follow the evolution and activity of the reversed polarity AR 7912 using multi-wavelength observations. We find that the presence of high shear increased by flux emergence led to the occurrence of a long-duration eruptive flare on 14 October 1995, which was manifested in the SXR corona by an arcade of expanding sigmoidal loops. A twisted magnetic cloud was observed at 1 AU between October 18-20. We propose that it was ejected from this reversed polarity AR, and it was associated with the expanding sigmoids. Title: Relationships between CME's and prominences Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Aulanier, G.; Démoulin, P.; Thompson, B.; De Forest, C.; Wiik, J. E.; Saint Cyr, C.; Vial, J. C. Bibcode: 2002AdSpR..29.1451S Altcode: We have studied the erupting prominences which were associated with coronal mass ejections during a series of campaigns involving both spacecraft and ground-based observatories. The evolution of the physical conditions within the prominences was established from Hα and magnetic field observations. Particular attention ahs been paid to the presence of mixed amgnetic polarity in the filament channel, the evolution of the shear of the large-scale magnetic field, and the existence of multiple magnetic inversion lines. We conclude that reconnection of large-scale coronal magnetic fields is responsible for both the CME and filament eruption. Title: A Relationship Between Transition Region Brightenings, Abundances, and Magnetic Topology Authors: Fletcher, Lyndsay; López Fuentes, Marcelo C.; Mandrini, Cristina H.; Schmieder, Brigitte; Démoulin, Pascal; Mason, Helen E.; Young, Peter R.; Nitta, Nariaki Bibcode: 2001SoPh..203..255F Altcode: We present multi-instrument observations of active region (AR) 8048, made between 3 June and 5 June 1997, as part of the SOHO Joint Observing Program 33. This AR has a sigmoid-like global shape and undergoes transient brightenings in both soft X-rays and transition region (TR) lines. We compute a magneto-hydrostatic model of the AR magnetic field, using as boundary condition the photospheric observations of SOHO/MDI. The computed large-scale magnetic field lines show that the large-scale sigmoid is formed by two sets of coronal loops. Shorter loops, associated with the core of the SXT emission, coincide with the loops observed in the hotter CDS lines. These loops reveal a gradient of temperature, from 2 MK at the top to 1 MK at the ends. The field lines most closely matching these hot loops extend along the quasi-separatrix layers (QSLs) of the computed coronal field. The TR brightenings observed with SOHO/CDS can also be associated with the magnetic field topology, both QSL intersections with the photosphere, and places where separatrices issuing from bald patches (sites where field lines coming from the corona are tangent to the photosphere) intersect the photosphere. There are, furthermore, suggestions that the element abundances measured in the TR may depend on the type of topological structure present. Typically, the TR brightenings associated with QSLs have coronal abundances, while those associated with BP separatrices have abundances closer to photospheric values. We suggest that this difference is due to the location and manner in which magnetic reconnection occurs in two different topological structures. Title: Why Are Solar Filaments More Extended in Extreme-Ultraviolet Lines than in Hα? Authors: Heinzel, P.; Schmieder, B.; Tziotziou, K. Bibcode: 2001ApJ...561L.223H Altcode: A long solar filament was observed simultaneously in the Hα line by THEMIS/MSDP and in selected EUV lines by the Coronal Diagnostic Spectrometer on SOHO. Co-alignment of optical and EUV images reveals that the dark EUV filament is much more extended than the Hα filament. Assuming that the EUV filament represents Lyman continuum absorption of the background EUV-line radiation, a straightforward explanation of this effect is suggested. Based on non-LTE filament models, we demonstrate that the ratio of the Lyman continuum to Hα opacity can reach a factor of 50-100, and thus the EUV filament is still well visible while the Hα line contrast diminishes below the detection limit. This kind of interpretation leads to an important conclusion that the cool filament material in which the Lyman continuum absorption takes place is more abundant than one would expect from Hα disk observations. This then may have significant consequences on the filament structure and on formation models, as well as on mass considerations related to coronal mass ejections. Title: A Study of Hydrogen Density in Emerging Flux Loops from a Coordinated Transition Region and Coronal Explorer and Canary Islands Observation Campaign Authors: Mein, N.; Schmieder, B.; DeLuca, E. E.; Heinzel, P.; Mein, P.; Malherbe, J. M.; Staiger, J. Bibcode: 2001ApJ...556..438M Altcode: During an international ground-based campaign in the Canary Islands coordinated with space instruments (i.e., Transition Region and Coronal Explorer [TRACE]), we observed an active region on 1998 September 10 with high spatial and temporal resolution. New emerging flux in the central part of the active region was observed in magnetograms of the Swedish Vacuum Solar Telescope, La Palma. Emerging loops (arch-filament systems [AFSs]) are well developed in Hα and Ca II according to the observations made at the Vacuum Tower Telescope (VTT) and THEMIS telescope in Tenerife with the Multichannel Subtractive Double Pass (MSDP) spectrographs. The TRACE images obtained at 171 and 195 Å show low-emission regions that are easily identified as the individual AFS. They are due to absorption by hydrogen and helium continua in the cool filament plasma. We compare two techniques of measuring the hydrogen density in the cool dense fibrils of AFSs. The first method based on TRACE observations derived the neutral hydrogen column density of the plasma absorbing coronal lines. The second one using Hα line profiles provided by the MSDP spectrographs is based on the cloud model. The results are consistent. We derive also electron density values using Hα lines that are in good agreement with those derived from the 8542 Å Ca II line observed with THEMIS (Mein et al.). The three types of observations (TRACE, VTT, THEMIS) are well complementary: absorption of coronal lines giving a good approximation for the maximum value of the neutral hydrogen column density, the Hα line giving a good determination of ne, and the 8542 Å Ca II line a good determination of the electronic temperature. Title: Sunspot Formation from Emerging Flux Ropes - Observations from Flare Genesis Authors: Rust, D. M.; Bernasconi, P. N.; Georgoulis, M. K.; LaBonte, B. J.; Schmieder, B. Bibcode: 2001AGUSM..SP42A09R Altcode: From January 10 to 27, 2000, the Flare Genesis payload observed the Sun while suspended from a balloon in the stratosphere above Antarctica. The goal of the mission was to acquire a long time series of high-resolution images and vector magnetograms of the solar photosphere and chromosphere. We obtained images, magnetograms and Dopplergrams in the magnetically sensitive Ca I line at 6122 Angstroms. Additional simultaneous images were obtained in the wing of H-alpha. On January 25, 2000, we observed in NOAA region 8844 at N05 W30. The rapid development of a sunspot group that apparently included a delta spot (two polarities within one umbra). We considered a variety of models for interpreting these observations, including a twisted flux tube, a bipole that annihilates, a bipole that submerges, and a field distorted by mass loading. From the vector magnetograms and Doppler measurements, we conclude that nearly horizontal flux ropes are swept into the developing spot where they tilt upward to contribute to the familiar nearly vertical sunspot fields. The largest flux rope exhibited a twisted structure, and its angle with respect to the vertical was so great that it could be mistaken for a positive magnetic field merging into a negative sunspot. Flare Genesis was supported by NASA grant NAG5-8331 and by NSF grant OPP-9909167. Title: Peculiar Moving Magnetic Features Observed With the Flare Genesis Experiment Authors: Bernasconi, P. N.; Rust, D. M.; Georgoulis, M. K.; LaBonte, B. J.; Schmieder, B. Bibcode: 2001AGUSM..SP51A02B Altcode: With the Flare Genesis Experiment (FGE), a balloon-borne 80-cm solar telescope, we observed the active region NOAA 8844 on January 25, 2000 for several hours. FGE was equipped with a vector polarimeter and a lithium-niobate Fabry-Perot narrow-band filter. It recorded time series of filtergrams, vector magnetograms, and dopplergrams at the CaI 6122.2 Angstroms line, as well as Hα filtergrams, with a cadence between 2.5 and 7.5 minutes. At the time of the observations NOAA 8844 was located at approximately 5 deg N, 30 deg W. It was a new flux emergence that first appeared on the solar disk two days before and was still showing a very dynamic behavior. Its two main polarity parts were rapidly moving away from each other and new magnetic flux was constantly emerging from its center. Here we describe the structure and behavior of peculiar small moving magnetic dipoles (called moving magnetic features MMF's) that we observed near the trailing negative polarity sunspot of NOAA 8844. Presentations by D. M. Rust, and by M. K. Georgoulis at this meeting will focus on other aspects of the same active region. The MMF's took the form of small dipoles that first emerged into the photosphere near the center of a supergranular cell located next to the main trailing flux concentration. They rapidly migrated towards the spot, following the supergranular flow. The two polarities of the little dipoles did not separate; they moved together with same speed and in the same direction. The dipoles were oriented parallel to their motion toward the negative spot, with the positive polarity always leading. MMF's usually move away from sunspots, and their orientation is the reverse of what we see here. In addition, we noted that the dipole structure was not symmetric. The field lines of the trailing part of the MMF's (negative polarity) were always much more perpendicular to the local horizontal than the ones of the leading part. The trailing part looked more compact and circular, while the leading part was more elongated in the direction of the motion. We conclude that we observed a new type of MMF's with a totally different magnetic structure than previously seen. We present a possible model that could explain their unusual structure and behavior. This work was supported by NASA grant NAG5-8331 and NSF grant OPP-9909167. Title: SOHO/SUMER observations and analysis of the hydrogen Lyman spectrum in solar prominences Authors: Heinzel, P.; Schmieder, B.; Vial, J. -C.; Kotrč, P. Bibcode: 2001A&A...370..281H Altcode: The complete hydrogen Lyman spectrum in several prominences has been observed with the UV spectrometer SUMER on-board the SOHO, during the Joint Observing Programme 107, together with other space and ground-based observatories. Based on these observations, we are able to demonstrate, for the first time, that there exists a large variety of intensities and shapes of Lyman lines in different prominences and in various parts thereof. Therefore, no ``canonical'' Lyman spectrum can be considered for modelling purposes. However, we have identified at least two representative properties of the observed spectra: in one case (May 28, 1999 prominence) we detected high integrated intensities and no reversals in lines higher than Lalpha . Another prominence (June 2, 1999) exhibited quite similar integrated intensities, but all lines have rather strongly reversed profiles. This behaviour cannot be explained in terms of standard isothermal-isobaric models and we thus consider more general models which are in pressure equilibrium with the magnetic field and which have significant prominence-corona transition region (PCTR) temperature gradients. This type of model, recently suggested by Anzer & Heinzel (\cite{anhe99}), is capable of explaining strong emission profiles without reversal. Based on extended non-LTE computations, we suggest that quite different Lyman spectra mentioned above may correspond to two types of PCTRs, one seen along the magnetic-field lines (unreversed profiles) and the other one seen across the field lines (reversed profiles). Finally, we again confirm the importance of partial-redistribution (PRD) scattering processes for Lyman lines in prominences. However, our analysis of new SUMER data also points to a critical role of the PCTR in radiative transport in these lines. Title: CDS UV Brightenings Explained by Quasi-separatrices and Bald Patches in an S-shape active region Authors: Schmieder, B.; Démoulin, P.; Fletcher, L.; López Fuentes, M. C.; Mandrini, C. H.; Mason, H. E.; Young, P. R.; Nitta, N. Bibcode: 2001IAUS..203..314S Altcode: We present multi-instrument observations of AR 8048, made between June 3 and June5 1997 as part of SoHO JOP033. This active region has a sigmoid-like global shape and undergoes transient erupting phenomena which releases the stored energy. Using a force free field approach, we defined coronal magnetic field lines which fit with the observations. The large-scale magnetic field lines confirms the sigmoid characteristics of the active region. The study in 3D of the configuration explained where and how the energy is released at different places. The Ne VI brightenings correspond to the location of tangent to the photosphere field lines, named "bald patch", they are localized in the low transition region and represent feet of field lines. The Si XII brightenings at coronal temperature are at the top of coronal loops joining quasi-separatrices. Title: The Relationship between CMEs and Prominence Eruptions Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Delannée, C.; Simnett, G. M.; Wiik, J. E. Bibcode: 2001IAUS..203..310S Altcode: From multi-wavelength studies of eruptions of prominences observed by Yohkoh, SoHO and ground-based observatories, we find a good correlation between prominence eruptions and CMEs (i.e. May 1 1996, Sept 25 1996, May 31 1997). Focusing our interest on their temporal relationship, we observe that it is not clear that filament eruption is prior to the CME. Nevertheless they are both signatures of destabilization of the global coronal magnetic field. The magnetic configuration in the corona should involve the initial presence of a twisted flux tube. The eruption could be driven by a fast increase of the poloidal field in the flux tube or by photospheric shearing motions of the flux tube. Title: Chromosphere Authors: Schmieder, B. Bibcode: 2000eaa..bookE1993S Altcode: The chromosphere (Greek χρωμα, color) is a gaseous shell atmosphere surrounding the Sun, and more generally stars, with a typical thickness of 2000 km, lying above the SOLAR PHOTOSPHERE and containing mainly hydrogen and helium gas.... Title: Initiation of CMEs: the role of magnetic twist Authors: van Driel-Gesztelyi, L.; Manoharan, P. K.; Démoulin, P.; Aulanier, G.; Mandrini, C. H.; Lopez-Fuentes, M.; Schmieder, B.; Orlando, S.; Thompson, B.; Plunkett, S. Bibcode: 2000JASTP..62.1437V Altcode: 2000JATP...62.1437V Recent multiwavelength observations, modelling results and theoretical developments indicate the importance of twisted magnetic configurations in solar active regions (ARs) in the initiation of coronal mass ejections (CMEs). Through multiwavelength analysis of a few representative events we make an attempt to provide constraints for CME models. The two events presented here in detail start with the expansion of sigmoids (S- or inverse S-shaped loops) observed in soft X-rays. Both events (on 25 October /1994 and 14 October /1995) occurred before the launch of the SOHO spacecraft, but indirect evidences (i.e. signatures of an outward propagation traced up to /~20 solar radii and an associated magnetic cloud) suggest that both of them were related to CMEs. We show evidence that sigmoids are the coronal manifestations of twisted magnetic flux tubes, which start expanding presumably due to a loss of equilibrium. It is noteworthy that the analysed CMEs occurred in a complex (not simply bipolar) magnetic environment and in all cases we found evidences of the interaction (magnetic reconnection) with the surrounding fields. We propose a scenario for sigmoid expansion related CME events and suggest that twisted magnetic configurations are good candidates for being source regions of CMEs. Title: Coronal mass ejections (CMEs) initiation: models and observations Authors: Wu, S. T.; Guo, W. P.; Plunkett, S. P.; Schmieder, B.; Simnett, G. M. Bibcode: 2000JASTP..62.1489W Altcode: 2000JATP...62.1489W We use three observed coronal mass ejection (CME) events and numerical magnetohydrodynamic simulation models to illustrate three distinct CME initiation processes: (1) streamer destabilization due to increase of currents, via increase of axial fields, of the flux-rope, (2) photospheric shear and (3) plasma flow induced CME. The 3 January 1998 event is used to illustrate the streamer destabilization process to initiate a CME because the observed height-time curve indicates that the prominence eruption proceeds the CME initiation. We interpret this CME as being initiated because of destabilization of the streamer due to the upward motion of the flux-rope by the additional Lorentz /(J×B) force. On the other hand, the 22 June /1998 event shows that the CME was launched prior to the prominence eruption. This case is modeled by shear-induced loss-of-equilibrium. The last case is entirely different from the previous two. The morphology of the 5 October /1996 event does not show any relation with the filament//flux-rope. We modeled this event by introducing a plasma flow. Using the observations and MHD models, we conclude that the first two categories are flux-rope driven, because the energy source, which propels the CME, is stored in the flux-rope, and the third category is driven by an assumed plasma flow with the effects of fast solar wind, because this CME appears at the boundary region of a streamer and coronal hole. Title: Emergence of sheared magnetic flux tubes in an active region observed with the SVST and TRACE Authors: Deng, Y. Y.; Schmieder, B.; Engvold, O.; DeLuca, E.; Golub, L. Bibcode: 2000SoPh..195..347D Altcode: The active region NOAA AR 8331 was a target of an international ground-based observational campaign in the Canaries and coordinated with space instruments (TRACE and Yohkoh). We focus our study on observations obtained with the SVST at LaPalma, and with TRACE. On 10 September 1998, arch-filament systems were observed with high spatial and temporal resolution, from the lower to the upper atmosphere of the Sun, during five hours. Flux tubes emerged with increasing shear, which apparently led to energy release and heating in the overlying corona. A model for filament formation by the emergence of U-shaped loops from the subphotosphere, as proposed by Rust and Kumar (1994), is supported by the present observations. The coronal response to these events is visualized by rising, medium-scale loop brightenings. The low-lying X-ray loops show short-lived, bright knots which are thought to result from interaction between different loop systems. Title: Multi-wavelength study of the slow ``disparition brusque" of a filament observed with SOHO Authors: Schmieder, B.; Delannée, C.; Yong, Deng Yuan; Vial, J. C.; Madjarska, M. Bibcode: 2000A&A...358..728S Altcode: A mid-latitude filament was observed before and after its eruption with SOHO (EIT, SUMER, CDS and LASCO) and with ground based observatories (Meudon and Pic du Midi) in the context of a coordinated MEDOC campaign in Orsay. The eruption was followed by a large Coronal Mass Ejection well observed by LASCO. Few hours before its eruption, the filament is partially heated (as seen in 195 Ä with EIT). The physical conditions of the filament before its eruption have been investigated by spectroscopic analysis of SUMER (the Lyman series L4 to L9) and of CDS combined with the Multi-channel Subtractive Double Pass Spectrograph (MSDP) spectra of Hα . Five hours before the eruption, large broadenings of chromospheric and transition region lines (CDS) were observed in the main body of the filament suggesting strong turbulence as well as opposite Dopplershifts on each side of the filament (Hα and He I) which could be interpreted as twist motions. The optical thickness of the filament is rather large. During the eruption the twist is largely developed as observed in 304 Ä. The Doppler shifts of the filament estimated from Lyman lines are in good agreement with the velocity of the front edge of the CME bright loop. We notice that both, the filament and the bright loop, are deviated towards the equator. This implies that they belong to the same global expansion event constrained to remain in the equatorial streamer. An X-ray bright point observed close to a filament footpoint could be the signature of reconnection process linked to the destabilization of the filament. It is interpreted in the framework of new MHD modeling of lateral filament footpoints (Aulanier & Démoulin 1998). Title: Hα and Soft X-Ray Brightening Events Caused by Emerging Flux Authors: Tang, Y. H.; Li, Y. N.; Fang, C.; Aulanier, G.; Schmieder, B.; Demoulin, P.; Sakurai, T. Bibcode: 2000ApJ...534..482T Altcode: By using Yohkoh soft X-ray images, vector magnetograms, and Hα filtergrams, the brightening event that occurred on 1994 May 18 has been studied in detail. It occurred in a nearly potential large-scale magnetic configuration as shown by the comparison between the magnetic extrapolation (linear force-free field) and the large-scale soft X-ray loops. This event is related to the emergence of a new magnetic flux of about 3×1020 Mx. The impulsive enhancement of the emerging flux occurs about 20 minutes before the peaks of the Hα and soft X-ray brightening and lasts for about 10 minutes. This brightening may be a signature of reconnection taking place between the preexisting nonpotential loops and the new emerging small loops. The magnetic energy provided by reconnection is likely to be stored in the nonpotential loops and the emerging flux as implied by the vector magnetograms. By using the electron temperature and the electron density of the brightening event derived from the analysis of the Yohkoh data, an energy budget has been estimated. The result indicates that the energy needed can be reasonably provided by magnetic reconnection. Title: New Results from the Flare Genesis Experiment Authors: Rust, D. M.; Bernasconi, P. N.; Eaton, H. A.; Keller, C.; Murphy, G. A.; Schmieder, B. Bibcode: 2000SPD....31.0302R Altcode: 2000BAAS...32..834R From January 10 to 27, 2000, the Flare Genesis solar telescope observed the Sun while suspended from a balloon in the stratosphere above Antarctica. The goal of the mission was to acquire long time series of high-resolution images and vector magnetograms of the solar photosphere and chromosphere. Images were obtained in the magnetically sensitive Ca I line at 6122 Angstroms and at H-alpha (6563 Angstroms). The FGE data were obtained in the context of Max Millennium Observing Campaign #004, the objective of which was to study the ``Genesis of Solar Flares and Active Filaments/Sigmoids." Flare Genesis obtained about 26,000 usable images on the 8 targeted active regions. A preliminary examination reveals a good sequence on an emerging flux region and data on the M1 flare on January 22, as well as a number of sequences on active filaments. We will present the results of our first analysis efforts. Flare Genesis was supported by NASA grants NAG5-4955, NAG5-5139, and NAG5-8331 and by NSF grant OPP-9615073. The Air Force Office of Scientific Research and the Ballistic Missile Defense Organization supported early development of the Flare Genesis Experiment. Title: Foreword Authors: Vázquez, M.; Schmieder, B. Bibcode: 2000ESASP.463D..13V Altcode: 2000sctc.procD..13V No abstract at ADS Title: Solar filaments - comparing multi-wavelength observations with magnetic modelling Authors: Schmieder, B. Bibcode: 2000ssls.work...57S Altcode: Multi-wavelength observations of a filament/prominence obtained during campaigns with the space missions (SOHO, Yohkoh, TRACE) open a new research field. Physical conditions of filaments and their environment (i.e. temperature, dynamcis, electron density) provides important constraints on theories of formation, stability or instability. The fine structures of filament are discussed in the framework of magnetic configurations: Is the prominence field a sheared arcade or a twisted flux rope? What is the magnetic structure of the footpoints of prominences called also "barbs"? Are the field lines dipped or are they vertical? We present some new developments of 3-D models of a bipolar magnetic field and twisted flux tube which explain the fine structures in prominences as well as the feet. The new models bring valuable information on the global solar magnetic field with direct implications for dynamo theories and on the helicity of the heliosphere. Title: Brightening Event in Hα and Soft X-Ray on May 18, 1994 Authors: Tang, Y. H.; Li, Y. N.; Schmieder, B.; Aulanier, G.; Demoulin, P.; Fang, C.; Sakurai, T. Bibcode: 2000AdSpR..25.1829T Altcode: By using Yohkoh soft X-ray images, vector magnetograms and Hα filtergrams, a brightening event that occurred on May 18, 1994 has been studied in detail. It occurred in a nearly potential large-scale magnetic configuration as shown by the comparisons between the magnetic extrapolations (linear force-free field) and the large-scale soft X-ray loops. This brightening event observed in Hα line and soft X-ray seems to be related to new emerging magnetic flux with an amount of photospheric magnetic flux of about 3× 1020 Mx. The emerging flux increases obviously about 20 minutes before the Hα and soft X-ray brightening, and lasts for about 103 s. This brightening may be a signature of reconnection taking place between the pre-existing loop and the new emerging small loops Title: N-S Variation of the X-ray Flare Number during the Solar Cycle 22 Authors: Schmieder, B.; Li, K. J.; Li, Q. S. Bibcode: 2000ESASP.463..423S Altcode: 2000sctc.proc..423S No abstract at ADS Title: 3-D Magnetic Configurations for Filaments and Flares: The Role of ``Magnetic Dips'' and ``Bald Patches'' Authors: Aulanier, G.; Schmieder, B.; van Driel-Gesztelyi, L.; Kucera, T.; Démoulin, P.; Fang, C.; Mein, N.; Vial, J. -C.; Mein, P.; Tang, Y. H.; Deforest, C. Bibcode: 2000AdSpR..26..485A Altcode: The 3-D magnetic configuration of a filament and of a low energy flare is reconstructed, using linear mag- netohydrostatic (lmhs) extrapolations. In both cases, we find observational signatures of energy release at the locations of computed ``bald patches'' separatrices, characterised by field lines which are tangent to the photosphere.The filament was observed on Sept. 25, 1996, in Hα with the MSDP on the German VTT, Tenerife, as well as in Si IV with SOHO/SUMER. It is modeled as a twisted flux-tube deformed by the magnetic polarities observed with SOHO/MDI. The shape and location of the computed dipped field lines are in good agreement with the shape of the filament and its feet observed in Hα. Some ``bald patches'' (BPs) are present where the distribution of dips reaches the photosphere. We show that some of the large scale field lines rooted in BPs can be related to bright fine structures in Si IV. We propose that the plasma there is heated by ohmic dissipation from the currents expected to be present along the BP separatrices.The flare was observed on May 18, 1994, in soft X-rays with Yohkoh/SXT, and in Hα at Mitaka (Japan). The magnetic field is directly extrapolated from a photospheric magnetogram from Kitt Peak Observatory. The intersections with the photosphere of the computed separatrices match well the bright Hα ribbons. The later are associated to three BPs, with overlaying dipped field lines. We show that enhanced densities are present in these dips, which can be correlated with dark Hα fibrils.Both cases show the importance of dipped field lines and BPs in the solar atmosphere. Energy release via ohmic dissipation as well as reconnection along BP separatrices is proposed to provide heating observed as UV brightenings in filament channels and even as small flares Title: Dynamics in Restructuring Active Regions Observed During Soho/Yohkoh/Gbo Campaigns Authors: Schmieder, B.; Deng, Y.; Mandrini, C. H.; Rudawy, P.; Nitta, N.; Mason, H.; Fletcher, L.; Martens, P.; Brynildsen, N. Bibcode: 2000AdSpR..25.1879S Altcode: JOP17 and JOP 33 are SOHO Joint Observing Programs in collaboration with Yohkoh/SXT and ground based observatories (GBO's), dedicated to observe dynamical events through the atmosphere. During runs of these programs we observed in restructuring active regions (ARs), surges, subflares, bright knots, but not large flares and jets. From these observations we have been able to derive some of the responses of the coronal and chromospheric plasma to the evolution of the photospheric magnetic field. Emerging flux in an AR led to the formation of Arch Filament Systems in the chromosphere, hot loops and knots in the transition region, and X-ray loops. Frequent surges have been observed in relation to parasitic or mixed polarities, but coronal jets have not yet been found. We discuss the possible mechanisms acting during the restructuring of the active regions (reconnection or ``sea-serpent'' geometries) Title: Solar Prominences Observed by Soho (SUMER, CDS, EIT) and Ground-Based Observatories (GBO) Authors: Heinzel, P.; Schmieder, B.; Vial, J. C.; Rudawy, P. Bibcode: 2000AdSpR..25.1777H Altcode: We present two sets of prominence observations in higher lines of the hydrogen Lyman series (from Lδ to L-9), together with some other UV lines. These data have been obtained by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) onboard the SOHO satellite in June 1997. Coordinated observations were also taken by other SOHO instruments: Coronal Diagnostic Spectrometer (CDS) and Extreme-Ultraviolet Imaging Telescope(EIT) and with the coronagraph of the Wroclaw University Observatory at Bialkóv, the spectrograph of the Ondřejov Observatory. We demonstrate the basic characteristics of the calibrated line profiles and compare them with the theoretical profiles computed from isothermal-isobaric models Title: The Total Eclipse Experience in Hungary Authors: van Driel-Gesztelyi, L.; Jankovics, I.; Kovács, J.; Schmieder, B.; Vincze, I. J. Bibcode: 1999ESASP.448.1297V Altcode: 1999ESPM....9.1297V; 1999mfsp.conf.1297V No abstract at ADS Title: Diagnostics Constraints on Prominence Parameters from SOHO and Ground-based Observations Authors: Schmieder, B.; Kotrč, P.; Heinzel, P.; Kucera, T.; Andretta, V. Bibcode: 1999ESASP.448..439S Altcode: 1999ESPM....9..439S; 1999mfsp.conf..439S No abstract at ADS Title: Interpretation of the Activity due to Flux Emergence in an AR Authors: Mandrini, C. H.; Démoulin, P.; Schmieder, B.; Deng, Y. Y.; Rudawy, P. Bibcode: 1999ESASP.448..617M Altcode: 1999ESPM....9..617M; 1999mfsp.conf..617M No abstract at ADS Title: Bright Rims of Solar Prominences Authors: Hansen, I.; Engvold, O.; Schmieder, B.; Mein, N.; Mein, P. Bibcode: 1999ESASP.448..491H Altcode: 1999mfsp.conf..491H; 1999ESPM....9..491H No abstract at ADS Title: A Study of Hydrogen Density in Emerging Flux Loops from a Coordinated TRACE and Canary Islands Observation Campaign Authors: Schmieder, B.; Deluca, E.; Mein, N.; Mein, P.; Malherbe, J. M.; Wilken, V.; Staiger, J.; Engvold, O.; Hanssen, I. Bibcode: 1999ESASP.448..653S Altcode: 1999mfsp.conf..653S; 1999ESPM....9..653S No abstract at ADS Title: Fine-Structures and Dynamics of a Filament in EUV lines: SOHO/CDS and SUMER, TRACE Authors: Schmieder, B.; Engvold, O.; Wiik, J. E.; Deluca, E. Bibcode: 1999ESASP.446..599S Altcode: 1999soho....8..599S No abstract at ADS Title: Hydrogen Lyman Lines and Continuum Emission in a Polar-Crown Prominence Observed with SUMER/SOHO Authors: Schmieder, B.; Kucera, T.; Heinzel, P.; Vial, J. -C. Bibcode: 1999ESASP.446..605S Altcode: 1999soho....8..605S We present, for the first time, a quasi-simultaneous spectroscopic observation of the whole Lyman series of HI and continuum in a quiescent prominence. Namely we have extended our previous study of higher Lyman lines to lower members of the series, particularly L-alpha and L-beta. For the latter two lines, we compare our calibrated profiles (free of geocoronal absorption) with previous data from OSO-8 LPSP spectrometer and (for L-alpha) from UVSP/SMM. We demonstrate the importance of Lyman lines for studies of the base of the prominence-corona transition region. Title: Analysis of evolution of NOAA 7912 active region on 19 October 1995 Authors: Rudawy, P.; van Driel-Gesztelyi, L.; Cader-Sroka, B.; Mein, P.; Mein, N.; Schmieder, B.; Malherbe, J. -M.; Rompolt, B. Bibcode: 1999A&AS..139...89R Altcode: An analysis of a minor (B3.2) flare related to an X-ray jet in the reversed polarity NOAA 7912 active region is presented, focusing on various kinds of activity observed in the Hα line with the MSDP instrument. Using complementary Yohkoh soft X-ray observations and a Kitt Peak magnetic field map we study the influence of a rather low and graduate energy release on filaments, fibrils and chromospheric brightenings and their relevant coronal features. We find that this small flare affected the entire AR and was associated with strong up- and downflows along remote fibrils and filaments, which appear to be connected by large-scale loops. It is shown that at least one of the observed brightenings was caused by downflow of the matter, thus, by the kinematic heating of the material. The filament in the vicinity of the flare footpoints changed the most: it broke into two parts, temporarily rose to higher altitudes inside the AR and even erupted outside of the AR, re-forming only three hours later. We show that even a minor flare can lead to important morphological and dynamical changes in an active region. Title: SOHO/SUMER observations and analysis of hydrogen Lyman lines in a quiescent prominence Authors: Schmieder, B.; Heinzel, P.; Vial, J. C.; Rudawy, P. Bibcode: 1999SoPh..189..109S Altcode: A quiescent prominence was observed in June 1997 by instruments onboard the SOHO spacecraft: the Solar Ultraviolet Measurements of Emitted Radiation (SUMER), Coronal Diagnostic Spectrometer (CDS) and Extreme-Ultraviolet Imaging Telescope (EIT), along with the coronagraph of the Wrocław University Observatory at Bialków and the spectrograph of the Ondřejov Observatory. We present prominence observations in higher lines of the hydrogen Lyman series (from Lδ to L-9), together with some other UV lines obtained by SUMER. We extract the basic characteristics of the calibrated line profiles of these Lyman lines and compare them with the theoretical profiles computed from three kinds of NLTE models which also include prominence filamentation. Our principal result is that the current NLTE models are in principle capable of explaining the SUMER calibrated intensities in the observed Lyman lines. We also find that in order to fit all these lines, one has to consider a prominence-corona transition region (PCTR) with a temperature gradient. At low pressures, higher Lyman lines are still rather sensitive to the incident radiation which must be carefully taken into account in the modeling. From PCTR models, which also take into account the effect of ambipolar diffusion on the heating, we have derived the formation depths for the Lyman series lines. High Lyman lines seem to be formed just at the base of the PCTR. Title: The Role of "Magnetic Dips" and "Bald Patches" for a Filament Observed by SOHO and GBO Authors: Aulanier, G.; Schmieder, B.; Kucera, T.; van Driel-Gesztelyi, L.; Démoulin, P.; Mein, N.; Vial, J. -C.; Mein, P. Bibcode: 1999ASPC..184..291A Altcode: The studied filament was observed on Sept. 25, 1996, in Hα with the MSDP on the German VTT, Tenerife, as well as in Si IV with SOHO/SUMER. The 3-D magnetic configuration of the filament channel is reconstructed, using linear magnetohydrostatic (lmhs) extrapolations from a SOHO/MDI magnetogram, which is modified by a background magnetic component constraining a twisted flux-tube. This flux-tube is deformed by the magnetic polarities observed with SOHO/MDI. The shape and location of the computed "dipped field lines" are in good agreement with the shape of the filament and its feet observed in Hα. Some "bald patches" (BPs) are present where the distribution of dips reaches the photosphere. We find observational signatures in Si IV brightenings of energy release at the locations of computed "bald patch separatrices", defined by field lines which are tangent to the photosphere. We propose that the plasma is there heated by ohmic dissipation from the expected currents in the BP separatrices. The results show the importance of "dipped field lines" and "bald patches" in filament channels. Title: Magnetic Field Evolution and Topology of an AR Authors: Mandrini, C. H.; Deng, Y. Y.; Schmieder, B.; Démoulin, P.; Rudawy, P.; Nitta, N.; Newmark, J.; de Forest, C. Bibcode: 1999ASPC..184..276M Altcode: Active region 7968 was observed during runs of a coordinated SOHO, Yohkoh and ground-based observatory program (Joint Observing Program, JOP, 17). The region appeared and decayed in a seven day period (June 3 to 10, 1996). In this time, mainly during June 6, it presented a very dynamical behaviour. Flux emerged in between the two main polarities and Arch Filament Systems (AFS) were observed to be linked to this emergence. We analyze the evolution of some over dark arches observed during flux emergence, forming two systems of AFS. Modelling the magnetic field, we find that these systems were associated to field lines having dips tangent to the photosphere (the so called "bald patches", BPs). We discuss their evolution in terms of emergence of the dipped portion of the lines or of magnetic field reconnection. Title: Coordinated Prominence Observations by SOHO and Ground-Based Observatories Authors: Schmieder, B.; Heinzel, P.; Vial, J. -C.; Malherbe, J. M.; Mein, P.; Rudawy, P.; Ceppatelli, G. Bibcode: 1999ASPC..184..296S Altcode: Coordinated observations obtained during the JOP12 (Joint Observing Programme between SOHO and ground-based instruments) allow us to analyse the physical conditions in a prominence of 5 June 1997 and its environment in the solar corona. The arch-shaped prominence shows either vertical or horizontal structures according to the observed lines (Hα with the coronagraph of the Wroclaw University Observatory at Bialków and lines in a broad temperature range by the Coronal Diagnostic Spectrometer CDS). The less dynamic behaviour of this prominence was shown by the persistence of bubbles in the prominence and confirmed by the Dopplershifts measured in CDS lines and in Hα by the Italian Panoramic Monochromator (IPM) filter on the THEMIS telescope in Tenerife. We explain the complex morphology of this prominence by recent 3D MHD models. Finally, we present prominence spectra in higher lines of the hydrogen Lyman series (from Lδ to L-9), together with some other UV lines. These data have been obtained by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER). We demonstrate the basic characteristics of the calibrated line profiles of Lyman lines and compare them with the theoretical profiles computed from isothermal-isobaric models. This leads to some constraints on the environment of the prominence. Title: Long-Term Magnetic Evolution of an AR and its CME Activity Authors: van Driel-Gesztelyi, L.; Mandrini, C. H.; Thompson, B.; Plunkett, S.; Aulanier, G.; Démoulin, P.; Schmieder, B.; de Forest, C. Bibcode: 1999ASPC..184..302V Altcode: Using SOHO/MDI full-disc magnetic maps, we follow the magnetic evolution of a solar active region for several months in the period of July-November 1996. We extrapolate the photospheric magnetic fields in the linear force-free approximation and match the modelled field lines with the soft X-ray loops observed with the Yohkoh/SXT in order to diagnose the coronal magnetic shear. We find that while the turbulent motions diffuse the flux, the differential rotation, and possibly twisted flux emergence, increase the magnetic shear. Flares are observed during the first three rotations, while CME events (observed by SOHO/EIT and LASCO) originate from this AR from its emergence throughout its decay. Several early CMEs, while none of the late CMEs, are related to flare events above the GOES B1 level. We find that the late CMEs occur when the magnetic shear, after accumulating for four rotations, reaches a high level and saturates. We propose that CME activity serves as a valve through which the AR could get rid of excess shear and helicity. Title: The evolution from birth to decay of a short-lived active region Authors: Deng, Yuan Yong; Schmieder, Brigitte; Mandrini, Cristina H.; Khan, Josef I.; Démoulin, Pascal; Rudawy, Pawel Bibcode: 1999A&A...349..927D Altcode: In the following paper we present results of the analysis of NOAA active region 7968, which was the target of a coordinated observing campaign involving the instruments aboard the Solar and Heliospheric Observatory (SOHO), Yohkoh, and ground-based observatories (Bialków, Pic du Midi, and Huairou). This active region was relatively short-lived, and thus provides a rare example of a region observed continuously from its birth to its decay phase. We have extrapolated the SOHO Michelson Doppler Imager (MDI) longitudinal magnetograms, and have compared the results of the modeled field with loops observed over a wide range of temperatures ( ~ 10(5) -3x10(6) K). We find that, throughout the interval of disk passage, the global magnetic structure of the active region corresponds to a nearly potential-field configuration. Magnetic field shear is only seen in isolated patches along the polarity inversion line and is associated with the emergence of parasitic polarity regions. Several small GOES (B-class) X-ray flares and surge-like ejections were observed during the lifetime of the active region. We interpret both the heating of the active region loops and the flaring in terms of magnetic reconnection. In our scenario, the flares are assumed to be due to reconnection between the pre-existing field and newly emerging twisted flux tubes (as indicated by observed changes in the transverse field and inferred twisting motions of the plasma); while the heating of the plasma in quasi-static active region loops is assumed to be due to a relaxation process of the magnetic configuration. These loops appear anchored at places where the photospheric field is highly fragmented, creating a very complex connectivity pattern. This fact, together with the continual photospheric motions, provides the favorable conditions for current sheet formation and release of magnetic energy. Title: Some Advances in 3D-Magnetic Field Topology: an Observed Case of a "Bald Patch" Flare Authors: Démoulin, P.; Aulanier, G.; Schmieder, B. Bibcode: 1999ASPC..184...65D Altcode: The aim of this work is to bring observational evidences of the possible role of the "bald patch" topology in flaring events. A bald patch (or BP) is present along the photospheric inversion line where the field lines are curved-up, so when magnetic dips are present. The set of field lines associated to the BP define a separatrix where a current sheet may form. We find such configuration in AR 7722 where, on May 18, 1994, a sub-flare was observed in X-rays by Yohkoh/SXT and in Hα at NAOJ. Using the magnetohydrostatic equations derived by Low (1992), we model the magnetic field configuration by extrapolation of the Kitt Peak photospheric field, taking into account the effects of pressure and gravity. Hα flare kernels are shown to be located at the lower parts of the computed separatrices associated to bald patches (BPs). This is an evidence that BPs can be involved in flares, and that current sheets can be dissipated in low levels of the solar atmosphere. Title: Multiple-Thread Model of a Prominence Observed by SUMER and EIT on SOHO Authors: Wiik, J. E.; Dammasch, I. E.; Schmieder, B.; Wilhelm, K. Bibcode: 1999SoPh..187..405W Altcode: A quiescent polar crown prominence was observed at Meudon in Hα and Ca ii lines, and by EIT and SUMER on board SOHO in UV lines from 9 to 10 March 1996. SUMER observed the prominence continuously in a scanning mode between 21:40 UT on 9 March, and 18:13 UT on 10 March, in the nitrogen line N v (λ1238) with a 1 arc sec2 resolution. Altogether 190 prominence images (121×108 pixels) were obtained. These are presented in a movie. The prominence is highly dynamic. Large-scale features, such as mixed loop systems and dark cavities are changing on time scales of a few hours. Filamentary structure is evident and is changing within a few frames of the movie. A lifetime of 20-25 min for the fine structure has been found by the autocorrelation method. We have statistically analysed the three moments of the N v line in the prominence: line intensity, Doppler shift and linewidth, in the context of a multiple-thread model. We find that the data are consistent with a model where the prominence is assumed to be an ensemble of small threads. In the brightest parts of the prominence it is possible that there are many unresolved threads (15-20) along the line of sight with diameters smaller than a few hundred kilometers. The filling factor is probably very small and in that case the structures occupy only a fraction of the volume. Title: Derivation of physical parameters of chromospheric structures assuming a constant and a varying source function Authors: Tsiropoula, G.; Madi, C.; Schmieder, B. Bibcode: 1999SoPh..187...11T Altcode: Hα profiles of a rosette region consisting of several bright and dark mottles were obtained with the Multichannel Subtractive Double Pass (MSDP) spectrograph mounted on the 50 cm 'Tourelle' refractor of the Pic du Midi Observatory. These profiles have been analysed in terms of the classical cloud model which assumes a constant source function and holds only for optically thin structures. A new technique is also described which enables the determination of various physical parameters of chromospheric features taking into account the variation of the source function with the optical depth. This method can be applied, in contrast to the classical cloud model, to all lines whether optically thin or optically thick and gives a good fit to the entire profile from the core to the wings. A comparison of the results given by the two different methods is also performed. Title: A new emerging flux and brightening event. Authors: Li, Yining; Tang, Yuhua; Aulanier, G.; Schmieder, B.; Demoulin, P.; Fang, Cheng Bibcode: 1999PPMtO..18..131L Altcode: By using Yohkoh soft X-ray images, vector magnetograms and Hα filtergrams, a brightening event of Hα and soft X-ray of 18 May, 1994 has been studied in detail. It is shown that the event is obviously caused by new emerging flux. The brightening points of Hα and soft X-ray are located at computed separatrices associated to field lines which are tangent to the photosphere. This brightening event may be a signature of reconnection taking place between the pre-existing loops and the new emerging small loops in the lower solar atmosphere. Title: Filament channel structures in a SI IV line related to a 3d magnetic model Authors: Kucera, T. A.; Aulanier, G.; Schmieder, B.; Mein, N.; Vial, J. -C. Bibcode: 1999SoPh..186..259K Altcode: A recent 3D magnetic model of filament support (Aulanier and Démoulin, 1998) has shown that specific morphologies derived from the model, based on SOHO/MDI magnetograms, match quite well with the observations of a filament observed in Hα and Ca ii lines with the German telescope VTT in Tenerife on 25 September 1996 (Aulanier et al., 1998, 1999a). Some predictions of this model concern the filament channel. To continue the comparison of model and data, we have investigated the same filament region observed in ultraviolet by the SOHO spectrometers SUMER and CDS. The elongated EUV fine structures in the filament channel observed in the Si iv 1393.76 Å line by SUMER have similar orientations and locations to features predicted by the model of Aulanier et al. (1999a). These regions are near the bases of field lines which tangentially join to the photosphere in so called 'bald patches' and are parts of large arcades above the filament channel. In addition, we consider the Si iv Doppler shifts in these structures and compare them to what might be expected from the model field structure. Our study also suggests that the filament has a very low opacity in Si iv, lower than that of the O v line observed by CDS. Title: Multi-wavelength observations of the onset phase of a coronal mass ejection Authors: Innes, D. E.; Inhester, B.; Srivastava, N.; Brekke, P.; Harrison, R. A.; Matthews, S. A.; Noëns, J. C.; Schmieder, B.; Thompson, B. J. Bibcode: 1999SoPh..186..337I Altcode: The structure and dynamics of the initial phases of a coronal mass ejection (CME) seen in soft X-ray, extreme ultraviolet and optical emission are described. The event occurred on the SW limb of the Sun in active region AR 8026 on 9 April 1997. Just prior to the CME there was a class C1.5 flare. Images taken with the Extreme Ultraviolet Imaging Telescope (EIT) reveal the emergence of a candle-flame shaped extreme ultraviolet (EUV) cavity at the time of the flare. Yohkoh images, taken about 15 min later, show that this cavity is filled with hot X-ray emitting gas. It is most likely that this is the site of the flare. Almost simultaneous to the flare, an Hα surge or small filament eruption occurs about 50 arc sec northwards along the limb from the EUV cavity. At both the site of the core of the hot, EUV cavity and the filament ejection are X-ray jets. These jets seem to be connected by hot loops near their bases. Both jets disappear within a few minutes of one another. Title: Analysis Of The Disappearing Filament And Flare Of 7 May 1992 Authors: Tang, Y. H.; Mouradian, Z.; Schmieder, B.; Fang, C.; Sakurai, T. Bibcode: 1999SoPh..185..143T Altcode: By using Yohkoh soft X-ray data, Hα filtergrams, and radio data, the activation of the disappearing filament and the flare eruption on 7 May 1992 have been studied. Main conclusions are as follows: (1) the emergence of new magnetic flux tends to affect the pre-existing X-ray loops, which usually appear in arcades spanning Hα filament, changing the magnetic environment of the filament, and then enhance the current in the filament. Therefore newly emerging flux plays a fundamental role in the destabilization of this filament. (2) According to the Hα data and the rising motion of the filament, the corresponding current variation in the filament has been calculated. It seems that the current interruption may be a possible trigger mechanism for this filament disappearance. (3) The magnetic field strength and the energy flux of energetic electrons in the source region of microwave bursts have been estimated by using the microwave spectrum. During the main phase, the mean magnetic strength and the energy flux of energetic electrons are about 300-400 G and 1×1011 erg cm−2 s −1, respectively. (4) The energy provided by reconnection of the current sheet and the total energy of the current filament are estimated and we show that there is enough energy stored in the filament to feed the 7 May, 1992 flare. Title: 3-D magnetic configurations supporting prominences. III. Evolution of fine structures observed in a filament channel Authors: Aulanier, G.; Démoulin, P.; Mein, N.; van Driel-Gesztelyi, L.; Mein, P.; Schmieder, B. Bibcode: 1999A&A...342..867A Altcode: On September 25() th 1996, a quiescent filament located near the center disc (S2, E5) was observed on the German VTT (Tenerife) with the MSDP instrument, in the Hα line center and wings. SOHO/MDI line-of-sight magnetograms were co-aligned with the MSDP images, showing the position and evolution of the lateral feet of the filament in the vicinity of the parasitic magnetic polarities observed in the filament channel. Using the assumptions developed in the previous papers of this series related to the reconstruction of the 3-D magnetic configuration of filaments, we perform ``linear magnetohydrostatic'' extrapolations (taking into account the effects of plasma pressure and gravity) on the SOHO/MDI magnetograms. The main hypothesis is the presence of a twisted flux-tube located above the photospheric inversion line. Assuming that the parameters of the model do not need to be significantly modified during the evolution of the configuration for a duration of 1 day, we have shown that the 3-D distribution of dipped field lines is well correlated with Hα dark absorbing features in the filament channel: the filament itself, its lateral feet and some of the surrounding dark fibrils. In this way we confirm what was suggested in our earlier papers, i.e. that the feet are composed of the dipped portions of some field lines, which form a continuous pattern from the corona to the photosphere. We propose the same explanation for the magnetic configuration of some of the dark Hα fibrils in the channel. We show that the plasma effects are not responsible for the existence of most of the magnetic dips, however their inclusion helps to get a better correspondence between the model and the observations. We find that the average Hα Doppler velocities associated with the filament and with the chromospheric fibrils is of the order of a few hundred m s(-1) (though it can go locally up to 3 km s(-1) in the filament). These upward velocities are consistent with a quasi-static evolution of the magnetic configuration and with the support of dense plasma in magnetic dips. Title: Third Advances in Solar Physics Euroconference: Magnetic Fields and Oscillations Authors: Schmieder, B.; Hofmann, A.; Staude, J. Bibcode: 1999ASPC..184.....S Altcode: The third Advances in Solar Physics Euroconference (ASPE) "Magnetic Fields and Oscillations"concluded a series of three Euroconferences sponsored by the European Union. The meeting took place in Caputh near Potsdam, Germany, on September 22-25, 1998, followed by the JOSO (Joint Organization for Solar Observations) 30th Annual Board Meeting on September 26, 1998. The ASPE formula is attractive and compares well with other meetings with "show-and-tell" character. This meeting had 122 participants coming from 26 countries; 36 participants came from countries formerly behind the Iron Curtain; a "politically incorrect" estimate says that 48 participants were below 35 years of age, with an unusually large female-to-male ratio. This characteristic of youngness is the more striking since solar physics is a perhaps overly established field exhibiting an overly senior age profile. It was a good opportunity to train this young generation in Solar Physics. The conference topic "Magnetic Fields and Oscillations" obviously was wide enough to cater to many an interest. These proceedings are organized according to the structure of the meeting. They include the topics 'High resolution spectropolarimetry and magnetometry', 'Flux-tube dynamics', 'Modelling of the 3-D magnetic field structure', 'Mass motions and magnetic fields in sunspot penumbral structures', 'Sunspot oscillations', 'Oscillations in active regions - diagnostics and seismology', 'Network and intranetwork structure and dynamics', and 'Waves in magnetic structures'. These topics covered the first 2.5 days of the conference. The reviews, oral contributions, and poster presentations were by no means all of the meeting. The ASPE formula also adds extensive plenary sessions of JOSO Working groups on topics that involve planning of Europe-wide collaboration. At this meeting these concerned solar observing techniques, solar data bases, coordination between SOHO and ground-based observing, and preparations for August 11, 1999 when more Europeans will be eclipsed than ever before. The contributions to these sessions have been included into the present volume as well. The participants of the EU-TMR Research Network 'Solar Magnetometry Network' came together to discuss in a special working group session questions of their future collaboration. Title: Bright Points and Subflares in Ultraviolet Lines and X-Rays Authors: Rovira, M.; Schmieder, B.; Démoulin, P.; Simnett, G. M.; Hagyard, M. J.; Reichmann, E.; Tandberg-Hanssen, E. Bibcode: 1999ApJ...510..474R Altcode: We have analyzed an active region which was observed in Hα (Multichannel Subtractive Double Pass Spectrograph), in UV lines (SMM/UVSP), and in X-rays (SMM/HXIS). In this active region there were only a few subflares and many small bright points visible in UV and in X-rays. Using an extrapolation based on the Fourier transform, we have computed magnetic field lines connecting different photospheric magnetic polarities from ground-based magnetograms. Along the magnetic inversion lines we find two different zones: (1) a high-shear region (>70°) where subflares occur, and (2) a low-shear region along the magnetic inversion line where UV bright points are observed. In these latter regions the magnetic topology is complex with a mixture of polarities. According to the velocity field observed in the Si IV λ1402 line and the extrapolation of the magnetic field, we notice that each UV bright point is consistent with emission from low-rising loops with downflows at both ends. We notice some hard X-ray emissions above the bright-point regions with temperatures up to 8 × 106 K, which suggests some induced reconnection due to continuous emergence of new flux. This reconnection is also enhanced by neighboring subflares. Title: Calentamiento de arcos coronales en una región activa por reconfiguración topológica del campo magnético. Authors: López Fuentes, M.; Mandrini, C. H.; Démoulin, P.; Schmieder, B.; Fletcher, L.; Mason, H. Bibcode: 1999BAAA...43...24L Altcode: We study the active region (AR) 8048 observed on June 1997 in several wavelenghts. The combined observations obtained using CDS (SOHO) and SXT (Yohkoh) show the heating of the coronal magnetic loops at different atmospheric altitudes. Extrapolating the magnetic field in the corona from longitudinal magnetograms from MDI (SOHO), we determine the location of Bald Patches in the surroundings of the leading spot. This magnetic feature, the emergence of parasitic magnetic polarities and the observed photospheric motions provide the conditions to explain the observed heating. Title: Eruptive filament of May 31, 1997, observed by SOHO. Authors: Schmieder, B.; Heinzel, P.; Vial, J. -C.; Delaboudinière, J. -P.; Delannée, C. Bibcode: 1999joso.proc..147S Altcode: In the frame of the SUMER/CDS Joint Programme (JOP 17) the authors have detected the four Lyman lines in an erupting filament. The strong self-absorption in these lines, already reported for quiescent filaments, is still present in this highly dynamical event, but the authors observe a significant red asymmetry in the intensities of the two peaks. They ascribe it to an upward bulk motion of the filament, which they can actually see on a series of EIT images taken in the Fe XII line. Both sets of observations can lead to a determination of the velocity vector. The Doppler velocities are also derived from other lines detected by SUMER/CDS and can be correlated with the observations of the Pic-du-Midi MSDP obtained for this event. The filament eruption was also well observed by other GBO instruments in the Hα line (Meudon and Ondřejov). Title: Magnetic fields and oscillations. 3rd Euroconference ASPE98 (Advances in Solar Physics Euroconference 1998), Potsdam/Caputh (Germany), 22 - 25 Sep 1998. Poster contributions. Authors: Schmieder, B.; Staude, J. Bibcode: 1999joso.proc...74S Altcode: All of the oral presentations of ASPE98 will be published in a separate volume of the ASP Conference Series, while this volume contains the poster presentations. Title: Active Regions Authors: Holman, G. D.; Cheng, C. -C.; Gurman, J. B.; Haisch, B. M.; Poland, A. I.; Porter, J. G.; Saba, J. L. R.; Schmieder, B.; Strong, K. T. Bibcode: 1999mfs..conf...41H Altcode: Magnetic Field Strength and Strucutre Results Prior to SMM First Results with SMM Subsequent Results: 1983-1987 The Coronal Magnetic Structures Observing Campaign Coronal Magnetic Field Studies after SMM Dynamics and Heating of the Solar Corona FCS Line-Broadening Measurements Large Nonthermal Velocities Spatial Variations Correlation Studies FCS Line-Broadening Data Interpreting the FCS Line Broadening Constraints on Mass Motions Link to Heating Discussion Coronal Heating, Magnetic Fields, and Flares UVSP Obervations of Active Regions Transition Region Brightenings: UV Microflares Sunspots Magnetic Field and Height of the Transition Region Sunspot Plumes Sunspot Flows Horizontal Flows Vertical Flows Nonthermal Line Broadening Umbral Oscillations A Look Backward, a Look Forward Prominences and Filaments Prominence Environment and Structure Steady Flows in Prominence Material Activity in Prominences Postflare Loops and Surges Conclusion Title: Analysis of H profiles. Physical parameters of chromospheric mottles: A case study Authors: Tsiropoula, G.; Madi, C.; Schmieder, B.; Preka-Papadema, P. Bibcode: 1999A&AT...18..455T Altcode: Observations of a well-defined rosette region which consisted of several bright and dark mottles and located almost at the solar disc centre (N5, W5) were made with the Multichannel Double Pass (MSDP) spectrograph mounted on the 50 cm "Tourelle" refractor of the Pic Du Midi Observatory, on June 17, 1986. This instrument records a two-dimensional field on the solar surface and having 11 channels provides at every pixel of the field of view the profile of the H line. We have used these profiles to derive several physical parameters of the chromospheric mottles. The basic assumption of the method we used is that the source function is not constant inside the structures, but has a parabolic variation with the optical depth. By using an iterative least square procedure for non-linear functions, five parameters of chromospheric mottles were computed: the optical depth, the Doppler width, the line-of-sight velocity, the source function at the middle of the structure, and the source function's variation factor. Title: New Perspectives on Solar Prominences Authors: Schmieder, B. Bibcode: 1999ASPC..158..133S Altcode: 1999ssa..conf..133S No abstract at ADS Title: Multiple-thread model of a prominence observed by SUMER and EIT on SOHO and by GBO's. Authors: Wiik, J. E.; Dammasch, I. E.; Schmieder, B.; Wilhelm, K. Bibcode: 1999joso.proc..184W Altcode: No abstract at ADS Title: Physical properties of the quiescent prominence of 5June 1996, from Hα observations Authors: Li, Kejun; Schmieder, B.; Malherbe, J. -M.; Roudier, Th.; Wiik, J. -E. Bibcode: 1998SoPh..183..323L Altcode: The Multichannel Subtractive Double Pass spectrograph (MSDP) is designed to observe line profiles in a 2D field of view with a good spatial and temporal resolution. In order to deal with this unique opportunity, we introduce a new method for fitting the hydrogen Hα line formed in prominences and deriving various plasma parameters from line profile observations. A quiescent prominence was observed on 5June 1996, at the Pic du Midi during an international campaign between 09:30UT and 11:00UT with the MSDP spectrograph operating in Hα at the Turret Dome. Using the new fitting method, we show that the temperature, column density of hydrogen atoms and microturbulent velocity of the prominence are respectively about 8500K, 1.4x1012cm-2, and 10 to 20kms-1. The electron density of the prominence is about 1.8x1010cm-3. Title: Magnetohydrostatic Model of a Bald-Patch Flare Authors: Aulanier, G.; Démoulin, P.; Schmieder, B.; Fang, C.; Tang, Y. H. Bibcode: 1998SoPh..183..369A Altcode: On 18 May, 1994, a subflare was observed in AR 7722 in X-rays by Yohkoh/SXT and in Hα at National Astronomical Observatory of Japan. The associated brightenings are due to small-scale magnetic energy release, triggered by parasitic fluxes emerging and moving at the edge of leading sunspots. Using the magnetohydrostatic equations derived by Low (1992), we model the magnetic field configuration by extrapolation of the Kitt Peak photospheric field, taking into account the effects of pressure and gravity. Hα flare kernels are shown to be located at computed separatrices associated with field lines which are tangent to the photosphere, namely 'bald patches' (BPs). This is evidence that BPs can be involved in flares, and that current sheets can be dissipated in low levels of the solar atmosphere. The presence of dense plasma which is supported against gravity in the magnetic dips above BPs is correlated to dark elongated features observed in Hα. Mass flows in these flat fibrils are discussed in the context of energy release in the BP separatrices. The effect of the plasma on the computed magnetic configuration is shown to be of secondary importance with respect to the topology of the field. Title: Spectral Analysis of a Thermal Flare on 27 October 1993 Authors: Schmieder, B.; Fang, C.; Harra-Murnion, L. K. Bibcode: 1998SoPh..182..447S Altcode: A thermal subflare occurring on 27 October 1993 was observed during a multi-wavelength campaign with the Yohkoh spacecraft and the Multi-channel Subtractive Double-Pass spectrograph (MSDP) at Pic du Midi. The various instruments provided us with 2-D Hα spectra, X-ray spectra and X-ray images. A non-LTE computation (including chromospheric condensation) was carried out to determine the dynamic parameters of the flaring chromosphere. By combining these results with the Yohkoh data, we illustrate that momentum is balanced between the upflowing plasma and the downflowing cool plasma during the flare. This result is consistent with the evaporation model. Title: Multi-wavelength observations of POST flare loops in two long duration solar flares Authors: Harra-Murnion, L. K.; Schmieder, B.; van Driel-Gesztelyi, L.; Sato, J.; Plunkett, S. P.; Rudawy, P.; Rompolt, B.; Akioka, M.; Sakao, T.; Ichimoto, K. Bibcode: 1998A&A...337..911H Altcode: We have analysed two Long Duration solar Events (LDEs) which produced large systems of Post Flare Loops (PFLs) and which have been observed by Yohkoh and ground-based observatories. Using the Maximum Entropy Method (MEM) image synthesis technique with new modulation patterns we were able to make hard X-ray (HXR) images of the post flare loops recorded in the L Channel (13.9-22.7 keV) of the Yohkoh Hard X-ray Telescope. We obtained co-aligned 2-D maps in Hα (10(4) K), in soft X-rays (5x 10(6) K) and in hard X-rays (20x 10(6) K). We conclude that the soft X-ray (SXR) loops lie higher than the Hα loops and the former are overlaid by HXR emission. This is suggestive of the magnetic reconnection process. However some details are not consistent with the standard models. Firstly the separation between the HXR source and the SXR loop increases with time, with the HXR source being approximately a factor of five larger than the equivalent source in impulsive flares. Secondly the cooling times deduced from observations are longer than the theoretically expected ones and the discrepancy increases with time. We review the current models in view of these results. Title: Filament Observations with SOHO Sumer/cds: The Behaviour of Hydrogen Lyman Lines Authors: Schmieder, B.; Heinzel, P.; Kucera, T.; Vial, J. -C. Bibcode: 1998SoPh..181..309S Altcode: On 21 September 1996, a filament close to an area of enhanced network was observed with the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer and Coronal Diagnostic Spectrometer (CDS). CDS provided intensity, Doppler shift and linewidth maps of the region in six lines whose temperature range covers 104 to 106 K. SUMER observations consisted of maps of the region in four hydrogen Lyman lines (Lδ, L∈, L-6, L-7) and a Svi line (944 Å). In all the Lyman lines we detect a central absorption and an asymmetry in the intensity of the two peaks. First NLTE computations indicate that such reversed Lyman profiles and their absolute intensities can be reproduced with the existing filament models provided that we take into account a prominence-corona transition region (PCTR). We discuss the Lyman lines' asymmetry in terms of macroscopic flows by comparison with the Hei line Doppler shifts observed with CDS. Title: Statistical analysis of the X-ray flares (M >= 1) during the maximum period of solar cycle 22 Authors: Li, K. -J.; Schmieder, B.; Li, Q. -Sh. Bibcode: 1998A&AS..131...99L Altcode: The data of the X-ray flare events of class M>= 1 during the interval of 1987 to 1992 corresponding to the maximum period of the 22nd solar cycle have been investigated to study the North-South (N-S) and West-East (W-E) asymmetries. During that period it has been shown the existence of a real N-S asymmetry. That confirms recent studies done by using other indicators, such as sunspot areas \cite[(Oliver & Ballester 1994)]{oliv94}. The E-W asymmetry during that period is not significant but a non uniform flare distribution in longitude has been evidenced. That result is also in good agreement with the work made by \cite[Joshi (1995)]{josh95} using Hα flares for the same time period. We have shown that the behaviour of the reverse tendency of Solar Cycle 21 to exhibit a predominance of the southern hemisphere in the N-S asymmetry compared to the previous Solar Cycles (19 and 20) is maintained for Solar Cycle 22. A long period cycle of the N-S asymmetry could be suspected. Title: Arch Filament Systems Associated with X-Ray Loops Authors: Malherbe, J. M.; Schmieder, B.; Mein, P.; Mein, N.; Van Drielgesztelyi, L.; Von Uexküll, M. Bibcode: 1998SoPh..180..265M Altcode: Using multi-wavelength observations obtained with the Tenerife telescopes (VTT and GCT) and with the Yohkoh satellite, we observed new emerging flux with an associated arch filament system (AFS) in the chromosphere and bright X-ray loops in the corona. We observed the change of connectivity of the X-ray loop footpoints which may be at the origin of the occurrence of a subflare. Densities, gas and magnetic pressures of cold AFS and hot loops were derived and discussed. The extrapolation of the photospheric magnetic field observed with the GCT in a linear force-free field assumption (constant α) shows that this region, in spite of having roughly a global potential configuration, consists of two systems of arch filaments. We found these two systems best fitted with two sheared magnetic topologies of opposite α values of ± 0.1 Mm-1 Title: A possible interpretation of the inhomogeneity and material motion within the post-flare loop of June 26, 1992. Authors: You, Dan; Tang, Yuhua; Fang, Cheng; Schmieder, B. Bibcode: 1998AcASn..39..165Y Altcode: Using the theory of linear current instability, the authors discussed the possibility of inhomogeneous "knot" structures within the post-flare loop of June 25 - 26, 1992. Besides, by simultaneously considering the gravity of the Sun, magnetic stress within the loop and primary velocity at the top, the authors theoretically calculated the motion of matter within the post-flare loop. The theoretical results are in accord with observations. Title: The Postflare Loops and the Nearby Active Chromosphere of 1992 June 26: Addendum Authors: Malherbe, J. -M.; Tarbell, T.; Wiik, J. E.; Schmieder, B.; Frank, Z.; Shine, R. A.; van Driel-Gesztelyi, L. Bibcode: 1998ApJ...495..502M Altcode: Video segments are presented that were processed from a quantitative study of the dynamics of the evolution of Hα postflare loops developed after a large solar flare. The high spatial resolution of the Swedish Vacuum Solar Telescope (SVST) at La Palma provided a unique set of data for such an event. Title: First Observations with THEMIS Authors: Rayrole, J.; Mein, P.; Schmieder, B. Bibcode: 1998ASPC..155..260R Altcode: 1998sasp.conf..260R No abstract at ADS Title: SUMER/SOHO Filament Observations in Selected Lyman Lines Authors: Schmieder, B.; Kucera, T.; Heinzel, P.; Vial, J. -C. Bibcode: 1998ASPC..150..205S Altcode: 1998IAUCo.167..205S; 1998npsp.conf..205S No abstract at ADS Title: Evolution of the Magnetic Field and Chromospheric Fine Structure in a Filament Channel Authors: van Driel-Gesztelyi, L.; Mein, P.; Mein, N.; Schmieder, B.; Malherbe, J. -M.; Aulanier, G.; Démoulin, P.; Deforest, C.; Staiger, J. Bibcode: 1998ASPC..155..321V Altcode: 1998sasp.conf..321V No abstract at ADS Title: Microflares and active filaments Authors: Schmieder, B.; Fontenla, J.; Tandberg-Hanssen, E. Bibcode: 1998PAICz..88...63S Altcode: No abstract at ADS Title: Second Advances in Solar Physics Euroconference: Three-Dimensional Structure of Solar Active Regions Authors: Alissandrakis, Costas E.; Schmieder, Brigitte Bibcode: 1998ASPC..155.....A Altcode: 1998sasp.conf.....A No abstract at ADS Title: Non potentiality of coronal loops above active regions Authors: Aulanier, G.; Schmieder, B.; Démoulin, P.; van Driel-Gesztelyi, L.; Deforest, C. Bibcode: 1998ASPC..155..105A Altcode: 1998sasp.conf..105A No abstract at ADS Title: A method for determining physical parameters in chromospheric mottles Authors: Tsiropoula, G.; Madi, C.; Schmieder, B. Bibcode: 1998ESASP.421..341T Altcode: 1998sjcp.conf..341T No abstract at ADS Title: Filament Disparition Brusque and CME - September 25-26, 1996 Event Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Aulanier, G.; Demoulin, P.; Martens, P. C. H.; Zarro, D.; Deforest, C.; Thompson, B.; St. Cyr, C.; Kucera, T.; Burkepile, J. T.; White, O. R.; Hanaoka, Y.; Nitta, N. Bibcode: 1998ASPC..150..366V Altcode: 1998IAUCo.167..366V; 1998npsp.conf..366V No abstract at ADS Title: Surges and filaments in active regions during SOHO campaigns Authors: Schmieder, B.; Deng, Y.; Rudawy, P.; Nitta, N.; Mandrini, C. H.; Fletcher, L.; Martens, P.; Innes, D.; Young, P.; Mason, H. Bibcode: 1998ESASP.421..323S Altcode: 1998sjcp.conf..323S No abstract at ADS Title: New Perspectives on Solar Prominences Authors: Webb, David F.; Schmieder, Brigitte; Rust, David M. Bibcode: 1998ASPC..150.....W Altcode: 1998npsp.conf.....W; 1998IAUCo.167.....W No abstract at ADS Title: Helical Structure in an Eruptive Prominence Related to a CME (SUMER, CDS, LASCO) Authors: Kucera, T. A.; Poland, A. I.; Wiik, J. E.; Schmieder, B.; Simnett, G. Bibcode: 1998ASPC..150..318K Altcode: 1998IAUCo.167..318K; 1998npsp.conf..318K SOHO (SUMER/CDS) observed an eruptive prominence on May 1,1996, associated with a CME observed by LASCO. We investigate the physical conditions of this prominence in order to quantify velocity, temperature, and density. SUMER spectra in Si IV and O IV lines are used to obtain Doppler-shift images of the prominence. The prominence shows large-scale red and blueshifted regions, revealing a large helical structure with a global twist. In addition, fine structure analysis shows multiple components in the line profile, suggesting integration of many threads along the line-of-sight with a large dispersion of velocities (∼150 km s-1). Title: Dynamics and Fine Structures in Quiescent Prominences (MSDP/Pic du Midi, SOHO/SUMER and CDS) Authors: Li, K.; Malherbe, J. -M.; Wiik, J. E.; Schmieder, B.; Roudier, Th.; Kucera, T.; Poland, A. Bibcode: 1998ASPC..150...32L Altcode: 1998IAUCo.167...32L; 1998npsp.conf...32L No abstract at ADS Title: Bright Points and Subflares in UV Lines and in X-Rays Authors: Rovira, M.; Schmieder, B.; Demoulin, P.; Simnett, G. M.; Hagyard, M. J.; Reichmann, E.; Tandberg-Hanssen, E. Bibcode: 1998msfc.rept.....R Altcode: We have analysed an active region which was observed in Hα (MSDP), UV lines (SMM/UVSP), and in X rays (SMM/HXIS). In this active region there were only a few subflares and many small bright points visible in UV and in X rays. Using an extrapolation based on the Fourier transform we have computed magnetic field lines connecting different photospheric magnetic polarities from ground-based magnetograms. Along the magnetic inversion lines we find 2 different zones: 1. a high shear region (less than 70 degrees) where subflares occur 2. a low shear region along the magnetic inversion line where UV bright points are observed. Title: From one JOSO to another Authors: Schmieder, Brigitte Bibcode: 1998ASSL..222...84S Altcode: 1998ream.conf...84S No abstract at ADS Title: 3-D Modelling of a Filament Observed in Hα and with SOHO Authors: Aulanier, G.; Schmieder, B.; Démoulin, P.; Mein, N.; van Driel-Gesztelyi, L.; Mein, P.; Vial, J. C.; Deforest, C. Bibcode: 1998ESASP.417..217A Altcode: 1998cesh.conf..217A No abstract at ADS Title: X-ray jets in a reversed polarity region and interplanetary effects Authors: Schmieder, B.; van Driel, L.; Mein, N.; Mein, P.; Willson, R.; Raoult, A. Bibcode: 1998ESASP.421..157S Altcode: 1998sjcp.conf..157S No abstract at ADS Title: A study of activity in interacting sunspot groups Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Hénoux, J. -C. Bibcode: 1998PAICz..88...13S Altcode: No abstract at ADS Title: Velocity Fields of a Filament Region Observed with Ground-Based Telescopes and from SOHO Authors: Mein, P.; Schmieder, B.; Malherbe, J. -M.; Wiik, J. E.; Engvold, O.; Brekke, P.; Zirker, J. B.; Poland, A. I.; Delaboudiniere, J. -P.; Staiger, J. Bibcode: 1998ASPC..150..135M Altcode: 1998npsp.conf..135M; 1998IAUCo.167..135M No abstract at ADS Title: Evolution of a reversed polarity active region NOAA 7912 in the photosphere, the chromosphere and the corona. Authors: van Driel-Gesztelyi, L.; Baranyi, T.; Mein, N.; Cader-Sroka, B.; Rudawy, P.; Mein, P.; Rompolt, B.; Schmieder, B.; Malherbe, J. -M.; Willson, R.; Kile, J. N.; Raoult, A. Bibcode: 1998joso.proc..103V Altcode: The authors follow the evolution and activity of NOAA 7912, a reversed polarity region, in the photosphere (Kitt Peak magnetograms and Debrecen white-light photoheliograms), chromosphere (MSDP instrument mounted on the German VTT at Tenerife), and the corona (Yohkoh/SXT, Nançay radioheliograph and the VLA) between October 12-20, 1995. They find that in spite of the high shear and creation of several mixed-polarity regions through flux emergence, the flares in the group did not exceed the M-class level. This might be due to the fact that the highly inclined bipolar fields emerging in the following part of the primary reversed dipole were relatively small and quickly "consumed" by cancellation enhanced by sunspot motions. On the other hand, the presence of high shear and minor fast-moving parasitic polarities in NOAA 7912 was sufficient to produce eruptive events like X-ray jets with important coronal and interplanetary effects. Title: Three-dimensional structure of solar active regions. 2nd Euroconference ASPE97 (Advances in Solar Physics Euroconference 1997), Preveza (Greece), 7 - 11 Oct 1997. Poster contributions. Authors: Schmieder, B.; Alissandrakis, C. Bibcode: 1998joso.proc...78S Altcode: All of the oral presentations of ASPE97 will be published in a separate volume of the ASP Conference Series, while this volume contains the poster presentations. Title: Filament observations with SOHO SUMER/CDS. Authors: Schmieder, B.; Kučera, T.; Heinzel, P.; Vial, J. -C. Bibcode: 1998joso.proc..136S Altcode: During a coordinated campaign between SOHO and ground-based instruments a filament located close to the central meridian has been the target of SUMER and CDS spectrometers on September 21, 1996. Title: X-Ray Jets and Their Radio Signatures at Metric and Centimeter Wavelenths Authors: van Driel-Gesztelyi, L.; Willson, R. F.; Kile, J. N.; Raoult, A.; Klein, L.; Mein, N.; Rudawy, P.; Cader, B.; Rompolt, B.; Schmieder, B.; Mein, P.; Malherbe, J. M. Bibcode: 1998ASPC..154..707V Altcode: 1998csss...10..707V On October 19, 1995 at 10:30 UT and 17:00 UT, two semi-homologous X-ray jets were observed with the Yohkoh/SXT from AR 7912, a region having a reversed polarity group with vortex-like Hα fibril pattern and X-ray loops. The jets appeared over a mixed magnetic polarity region in the vicinity of the leading spot. The first event was also observed with the Nancay radio heliograph at 167, 236, and 327 MHz. Type III activity, indicating the presence of electron beams, superimposed on a noise-storm was clearly visible. Type III activity first appeared at 10:25 UT, coincident with the onset of the X-ray jet, at 164 MHz and 236 MHz close to the storm position, and in the direction of the X-ray jet. At 10:28:40 UT a new group of sources appeared eastward of the former activity, which may correspond to another jet branch along a more easterly path seen in the ohkoh} images. The second X-ray jet event was also observed with the Very Large Array (VLA) at 6.2, 20.7, and 91.6 cm. For this event, VLA snapshot maps at 6.2 and 20.7 cm reveal low-brightness temperature changes in source structure at the site of the X-ray jet during the preburst, impulsive, and decay phases. The VLA 91.6 cm observations also show noise storm emission above the active region but there is no clear temporal correlation between this later X-ray jet and the impulsive decimetric bursts that were observed during this period. Although the X-ray observations show that the two jets had similar temperatures, emission measures, speeds and trajectories they appear to have had dissimilar metric responses to these events. This surprising result may question our understanding of the process of electron beam acceleration in jets. Title: 3-D Magnetic Field Configuration Late in a Large Two-Ribbon Flare Authors: Moore, R. L.; Schmieder, B.; Hathaway, D. H.; Tarbell, T. D. Bibcode: 1997SoPh..176..153M Altcode: We present Hα and coronal X-ray images of the large two-ribbon flare of 25-26 June, 1992 during its long-lasting gradual decay phase. From these observations we deduce that the 3-D magnetic field configuration late in this flare was similar to that at and before the onset of such large eruptive bipolar flares: the sheared core field running under and out of the flare arcade was S-shaped, and at least one elbow of the S looped into the low corona. From previous observations of filament-eruption flares, we infer that such core-field coronal elbows, though rarely observed, are probably a common feature of the 3-D magnetic field configuration late in large two-ribbon flares. The rare circumstance that apparently resulted in a coronal elbow of the core field being visible in Hα in our flare was the occurrence of a series of subflares low in the core field under the late-phase arcade of the large flare; these subflares probably produced flaring arches in the northern coronal elbow, thereby rendering this elbow visible in Hα. The observed late-phase 3-D field configuration presented here, together with the recent sheared-core bipolar magnetic field model of Antiochos, Dahlburg, and Klimchuk (1994) and recent Yohkoh SXT observations of the coronal magnetic field configuration at and before the onset of large eruptive bipolar flares, supports the seminal 3-D model for eruptive two-ribbon flares proposed by Hirayama (1974), with three modifications: (1) the preflare magnetic field is closed over the filament-holding core field; (2) the preflare core field has the shape of an S (or backward S) with coronal elbows; (3) a lower part of the core field does not erupt and open, but remains closed throughout flare, and can have prominent coronal elbows. In this picture, the rest of the core field, the upper part, does erupt and open along with the preflare arcade envelope field in which it rides; the flare arcade is formed by reconnection that begins in the middle of the core field at the start of the eruption and progresses from reconnecting closed core field early in the flare to reconnecting `opened' envelope field late in the flare. Title: Eruptive prominence and associated CME observed with SUMER, CDS and LASCO (SOHO) Authors: Wiik, J. E.; Schmieder, B.; Kucera, T.; Poland, A.; Brekke, P.; Simnett, G. Bibcode: 1997SoPh..175..411W Altcode: Observations of an eruptive prominence were obtained on 1 May 1996, with the SUMER and CDS instruments aboard SOHO during the preparatory phase of the Joint Observing Programme JOP12. A coronal mass ejection observed with LASCO is associated temporally and spatially with this prominence. The main objective of JOP12 is to study the dynamics of prominences and the prominence-corona interface. By analysing the spectra of Oiv and Siiv lines observed with SUMER and the spectra of 15 lines with CDS, Doppler shifts, temperatures and electron densities (ratio of Oiv 1401 to 1399Å) were derived in different structures of the prominence. The eruptive part of the prominence consists of a bubble (plasmoid) of material already at transition region temperatures with red shifts up to 100 km s-1 and an electron density of the order of 1010cm-3. The whole prominence was very active. It developed both a large helical loop and several smaller loops consisting of twisted threads or multiple ropes. These may be studied in the SUMER movie (movie 2). The profiles of the SUMER lines show a large dispersion of velocities (±50 km s-1) and the ratio of the Oiv lines indicates a large dispersion in electron density (3 x 109cm-3 to 3x 1011cm-3). The CME observed by LASCO left the corona some tens of minutes before the prominence erupted. This is evidence that the prominence eruptions are probably the result of the removal of the restraining coronal magnetic fields which are in part responsible for the original stability of the prominence. Title: Magnetic reconnection driven by emergence of sheared magnetic field. Authors: Schmieder, B.; Aulanier, G.; Demoulin, P.; van Driel-Gesztelyi, L.; Roudier, T.; Nitta, N.; Cauzzi, G. Bibcode: 1997A&A...325.1213S Altcode: Recurrent subflares (Class C) were observed in the NOAA 7608 active region on 27 October 1993. From multi-wavelength observations (white-light, magnetic field, H-alpha, X-ray), obtained during a coordinated campaign between Pic du Midi and Yohkoh, it appears that these flares were double ribbon flares caused by new flux emergence. As the flare begins, the X-ray emission observed with Yohkoh/SXT is loop-shaped with the axis almost parallel to the magnetic inversion line, while during the flare development, X-ray loops appear at the location of the emerging flux. The extrapolation of the photospheric magnetic field in a linear force-free field configuration allows identification of the magnetic configuration given by the flares. The Hα flare ribbons are located at the intersections of the computed quasi-separatrice layers (QSLs) with the chromosphere. We show that the initial loop-shaped X-ray emission region is in fact formed by several smaller loops directed in a nearly orthogonal direction with their feet anchored close to or in the Hα ribbons. During the flare development there are X-ray loops which represent only one foot of open or largescale magnetic loops. For the studied flares the puzzling soft X-rays observations could only be understood with the help of Hα and magnetic data combined with a modeling of the coronal magnetic field. Further, from the deduced magnetic field topology, the width of the QSLs and our present knowledge of 3-D magnetic reconnection, we conclude that the flare was due to magnetic reconnection driven by emergence of sheared magnetic field impacting in the pre-existing coronal field. Title: Evidence of Magnetic Reconnection from Hα, Soft X-Ray and Photospheric Magnetic Field Observations Authors: Mandrini, C. H.; DÉmoulin, P.; BagalÁ, L. G.; Van Driel-Gesztelyi, L.; HÉnoux, J. C.; Schmieder, B.; Rovira, M. G. Bibcode: 1997SoPh..174..229M Altcode: A conventional view of magnetic reconnection is mainly based on the 2-D picture of an X-type neutral point, or on the extension of it to 3-D, and it is thought to be accompanied by flux transport across separatrices (places where the field-line mapping is discontinuous). This view is too restrictive when we realize the variety of configurations that are seen flaring. We designed an algorithm, called Source Method (SM), to determine the magnetic topology of active regions (ARs). The observed photospheric field was extrapolated to the corona using subphotospheric sources and the topology was defined by the link between these sources. Hα flare brightenings were found to be located at the intersection with the chromosphere of the separatrices so defined. These results and the knowledge we gained on the properties of magnetic field-line linkage, led us to generalize the concept of separatrices to `quasi-separatrix layers' (QSLs) and to design a new method (`quasi-separatrix layers method', QSLM) to determine the magnetic topology of ARs. QSLs are regions where the magnetic field-line linkage changes drastically (discontinuously when they behave like separatrices) and the QSLM can be applied to ARs where the photospheric field has been extrapolated using any kind of technique. In this paper we apply the QSLM to observed flaring regions presenting very different configurations and also to a decaying AR where a minor phenomenon, like an X-ray bright point (XBP), is observed. We find that the locations of flare and XBP brightenings are related to the properties of the field-line linkage of the underlying magnetic region, as expected from recent developments of 3-D magnetic reconnection. The extrapolated coronal field lines representing the structures involved in the analyzed events have their photospheric footpoints located at both sides of QSLs. Our results strongly support the hypothesis that magnetic reconnection is at work in various coronal phenomena, ranging from the less energetic ones to large-scale eruptions. Title: Post-flare loops of May 16, 1981. Spectral analysis. Authors: Gu, X. -M.; Ding, Y. -J.; Luo, Z.; Schmieder, B. Bibcode: 1997A&A...324..289G Altcode: We present the analysis of Hα spectra obtained during a two-ribbon flare observed on the solar disk on May 16, 1981 at Yunnan Observatory with the Spectra-Spectroheliograph (SSHG). The complicated asymmetric profiles produced by the post-flare loops overlying flare ribbons are analysed with a fast method based on the cloud model method. This method takes into account the bright background of the loops and allows computation of the physical quantities of loops crossed by the slit: velocity field, optical thickness, source function and Doppler width. Using the scanning spectra of the region, we obtain 2-D maps of these parameters. The validity of the method used is compared with other methods and the sensitivity of parameters to solution is discussed in details. The results obtained with this method are compared with those given by Heinzel et al. (1992SPh...139...81H) using a fully non-LTE approach. Title: Determination of physical parameters in dark mottles. Authors: Tsiropoula, G.; Schmieder, B. Bibcode: 1997A&A...324.1183T Altcode: The application of the cloud model to measurements of the contrast as a function of wavelength in the Hα line has recently enabled us to derive numerical values for various parameters (such as velocity, source function, Doppler width and optical depth) of dark mottles observed near the center of the solar disk. The values of these parameters are used together with the calculations of Poland et al. (1971SPh....18..391P) and Yakovkin and Zel'dina (1975SPh....45..319Y) in order to determine the physical conditions in these structures. Thus population densities at levels 1, 2, 3 (N_1_, N_2_, N_3_), total particle density of hydrogen N_H_, electron density N_e_, electron temperature T_e_, gas pressure, total column mass, mass density and degree of hydrogen ionization can be determined. The values obtained are comparable with estimates obtained for spicules and mottles by different authors in the past and, furthermore, offer the prospect of putting observational constraints on non-LTE two-dimensional modelling of dark mottles observed in the Hα line which is currently in progress. Title: Post-Flare Loops of 26 June 1992 - IV. Formation and Expansion of Hot and Cool Loops Authors: Van Driel-Gesztelyi, L.; Wiik, J. E.; Schmieder, B.; Tarbell, T.; Kitai, R.; Funakoshi, Y.; Anwar, B. Bibcode: 1997SoPh..174..151V Altcode: Observations of the post-flare loops after the X3.9 flare which occurred on 25 June, 1992 at 20:11 UT by the Yohkoh/SXT in X-rays, as well as in Hα obtained at 5 different observatories, have provided a unique, longest ever, set of data for a study of the relationship between the hot and cool post-flare loops as they evolve. At any given time, the altitude difference between the hot X-ray loops of 6-7× 106 K and the cool Hα loops of 1.5× 104 K is related to the expansion rate of the loop systems and their cooling time. Therefore, measurements of the expansion rate and relative height of hot and cool loops can provide direct observational values for their cooling times. We measured the altitude of hot and cool loops for 15 and 19 hours, respectively, and found that the cooling time increased as the density of the loops decreased. We found a reasonably good agreement between the observed cooling times and those obtained from model calculations, although the observed values were always somewhat longer than the theoretical ones. Taking into account evolutionary effects, we also found similar shapes and configurations of hot and cool loops during the entire observing period and confirmed that, at any time, hot loops are at higher altitude than cool loops, suggesting that cool loops indeed evolve from hot loops. These results were used to check the validity of the reconnection model. Title: The Postflare Loops and the Nearby Active Chromosphere of 1992 June 26 Authors: Malherbe, J. -M.; Tarbell, T.; Wiik, J. E.; Schmieder, B.; Frank, Z.; Shine, R. A.; van Driel-Gesztelyi, L. Bibcode: 1997ApJ...482..535M Altcode: The main objective of this paper is to present a quantitative study of the dynamics of the evolution of Hα postflare loops developed after a large solar flare and the processed videos produced from the observations. The high spatial resolution of the Swedish Vacuum Solar Telescope (SVST) at La Palma has provided a unique set of data for such an event. A Gaussian fitting method is proposed to derive intensities and Doppler shifts from observations taken at three wavelengths (Hα center and Hα +/- 0.07 nm). Moving condensations or ``blobs'' of cold material provide transverse velocities, which, together with the radial component, enable us to derive their velocity vector magnitude. Plasma velocities are around free-fall velocities near the top of the loops but are significantly smaller close to their footpoints, suggesting a deceleration mechanism. The loops are anchored in the chromosphere, which shows tremendous activity in the active region and in the nearby ``quiet Sun.'' Spicules and ejection of plasmoids are also observed at the limb. Title: Evolution of a Delta Group in the Photosphere and Corona Authors: Van Driel-Gesztelti, L.; Csepura, G.; Schmieder, B.; Malherbe, J. -M.; Metcalf, T. Bibcode: 1997SoPh..172..151V Altcode: 1997ESPM....8..151V We present a study of the evolution of NOAA AR 7205 in the photosphere and corona, including an analysis of sunspot motions, and show the evolutionary aspects of flare activity using full-disc white-light observations from Debrecen, vector magnetograms from Mees Observatory, Hawaii, and Yohkoh soft X-ray observations. NOAA AR 7205 was born on the disc on 18 June, 1992. During the first 3 days it consisted of intermittent minor spots. A vigorous evolution started on 21 June when, through the emergence and merging (v ≈ 100-150 m s-1) of several bipoles, a major bipolar sunspot group was formed. Transverse magnetic fields and currents indicated the presence of shear (clockwise twist) already on 21 June (with α ≈ 0.015 Mm-1). On 23 June, new flux emerged in the trailing part of the region with the new negative polarity spot situated very close to the big positive polarity trailing spot of the main bipole. The secondary bipole seemed to emerge with high non-potentality (currents). From that time the AR became the site of recurrent flare activity. We find that all 14 flares observed with the Yohkoh satellite occurred between the highly sheared new bipole and the double-headed principal bipole. Currents observed in the active region became stronger and more extended with time. We propose that the currents have been (i) induced by sunspot motions and (ii) increased by non-potential flux emergence leading to the occurrence of energetic flares (X1.8 and X3.9). This observation underlines the importance of flare analysis in the context of active region evolution. Title: Optical and Radio Spectral Analysis of a Recurrent Surge Authors: Kotrč, Pavel; Schmieder, Brigitte; Karlický, Marian; Heinzel, Petr Bibcode: 1997SoPh..172..199K Altcode: 1997ESPM....8..199K Coordinated observations obtained at Meudon (MSDP) and at Ondřejov provide surge spectra in optical range (Hα, Hβ, Hγ, Hµ, Ca H and K lines) and in radio range. The MSDP data allowed us to follow the time evolution of the surge. The spectra of Balmer lines were used to derive the electron density of the expelled cool material. The radio bursts indicate that the acceleration of electrons took place in the low and dense atmosphere, giving a good argument for a reconnection near the transition region. Title: 3-D Magnetic Field Configuration Late in a Large Two-Ribbon Flare Authors: Moore, R. L.; Schmieder, B.; Hathaway, D. H.; Tarbell, T. D. Bibcode: 1997SPD....28.0157M Altcode: 1997BAAS...29R.889M We present H-alpha and coronal X-ray images of the large two-ribbon flare of 25/26 June 1992 during its long-lasting gradual decay phase. From these observations we deduce that the 3-D magnetic field configuration late in this flare was similar to that at and before the onset of such large eruptive bipolar flares: the sheared core field running under and out of the flare arcade was S-shaped, and at least one elbow of the S looped into the low corona. From previous observations of filament-eruption flares, we infer that such core-field coronal elbows, though rarely observed, are probably a common feature of the 3-D magnetic field configuration late in large two-ribbon flares. The rare circumstance that apparently resulted in a coronal elbow of the core field being visible in H-alpha in our flare was the occurrence of a series of subflares low in the core field under the late-phase arcade of the large flare; these subflares probably produced flaring arches in the northern coronal elbow, thereby rendering this elbow visible in H-alpha. The observed late-phase 3-D field configuration presented here, together with the recent sheared-core bipolar magnetic field model of Antiochos, Dahlburg, and Klimchuk (1994) and recent Yohkoh SXT observations of the coronal magnetic field configuration at and before the onset of large eruptive bipolar flares, supports the seminal 3-D model for eruptive two-ribbon flares proposed by Hirayama (1974), with three modifications: (1) the preflare magnetic field is closed over the filament-holding core field; (2) the preflare core field has the shape of an S (or backward S) with coronal elbows; (3) a lower part of the core field does not erupt and open, but remains closed throughout flare, and can have prominent coronal elbows. In this picture, the rest of the core field, the upper part, does erupt and open along with the preflare arcade envelope field in which it rides; the flare arcade is formed by reconnection that begins in the middle of the core field at the start of the eruption and progresses from reconnecting closed core field early in the flare to reconnecting "opened" envelope field late in the flare. Title: NLTE Analysis of SUMER Filament Observations on SOHO Authors: Heinzel, P.; Schmieder, B.; Vial, J. -C. Bibcode: 1997ESASP.404..427H Altcode: 1997cswn.conf..427H No abstract at ADS Title: Solar Magnetic Field Events related to CMEs observed with SOHO (MDI, EIT, SUMER, LASCO) Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Wiik, J. E.; Thompson, B.; de Forest, C.; Saint Cyr, C.; Vial, J. -C.; Nitta, N.; Simnett, G. Bibcode: 1997IAUJD..19E..42S Altcode: We shall present two CMEs observed by LASCO during the minimum of activity of the Sun. These are associated with filament disparitions brusques (DB). CME and DB definitively seem to be consequences of global magnetic field instability, which causes reconnection of pre-existing field lines in the corona. We shall demonstrate how cancelling flux and converging magnetic field in photosphere may destabilize coronal streamers overlying one or two filament channels. Title: Prominence Activity Related to CME Observed by SOHO, YOHKOH and Ground-Based Observatories Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Wiik, J. E.; Kucera, T.; Thompson, B.; de Forest, C.; Saint Cyr, C.; Simnett, G. M. Bibcode: 1997ESASP.404..663S Altcode: 1997cswn.conf..663S No abstract at ADS Title: Two dimensional distribution of physical parameters in dark mottles assuming constant and non-constant source function Authors: Tsiropoula, G.; Madi, G.; Christopoulou, E.; Alissandrakis, G.; Schmieder, B.; Preka-Papadema, P. Bibcode: 1997jena.confE..60T Altcode: Observations of a rosette region consisting of several dark mottles located almost at the solar disk centre (N5, W5) were made with the Multichannel Double Pass (MSDP) spectrograph mounted on the 50 cm ``Tourelle'' refractor of the Pic du Midi Observatory, on June 17, 1986. The MSDP having 11 channels provides at every point of the field of view the profile of the H-alpha line, which is reconstructed from 11 values. The observed contrast profiles of the dark features as a function of the wavelength are used in terms of Beckers' cloud model (e.g. assuming that the source function is constant throughout the feature) in order to derive 4 parameters: the line-of-sight velocity, the optical depth at line centre, the Doppler width and the source function. The computation of the four parameters was carried out by an iterative least square procedure for non linear functions. Allowing the source function to have a parabolic variation with the optical depth and using the same iteration procedure the source function at the centre of the feature and the source function variation factor are determined. Comparison of the values of the physical parameters derived under these two different assumptions concerning the source function is performed. These values are also compared with the values obtained from multilevel non-LTE models. Title: Coordinated Observations of Prominences with SUMER/CDS and Ground Observatories Authors: Wiik, J. E.; Schmieder, B.; Kucera, T.; Poland, A. Bibcode: 1997ASPC..118..278W Altcode: 1997fasp.conf..278W An international campaign for the observation of prominences and filaments was successfully accomplished between June 3 and 9 1996. Several ground observatories took part in the campaign which included the space observatories SOHO and Yohkoh. The main objective of this campaign was to study the dynamics of prominences and the prominence-corona interface, the formation of filaments and the fine structures at different temperatures. We will reported on two Joint Observing Programmes of SUMER and CDS aboard SOHO (JOP 12 and JOP 17), which have been achieved. Finally we will present as an exemple a prominence observed on May 1, 1996 during the tests of the programme JOP 12. This prominence was associated with a CME (observed with LASCO). Very active parts with Dopplershifs up to +/- 36kms(-1) were measured in the SUMER spectra of the prominence, indicating the presence of twisted ropes during the eruption. Mean electron densities have spatial and temporal dispersion of one order of magnitude (10(9) - 10(10) cm(-3) ). Title: Magnetic reconnection driven by an emerging flux. Authors: Aulanier, G.; Démoulin, P.; Schmieder, B.; Malherbe, J. M.; van Driel-Gesztelyi, L.; Roudier, T. Bibcode: 1997joso.proc...51A Altcode: No abstract at ADS Title: Analysis of long duration flares Authors: Harra-Murnion, L. K.; Plunkett, S. P.; Helsdon, S. F.; Phillips, K. J. H.; van Driel-Gesztelyi, L.; Schmieder, B.; Rompolt, B.; Akioka, M. Bibcode: 1997AdSpR..20.2333H Altcode: Yohkoh has observed many long duration events permitting a statistical study of the properties of these interesting events. We have selected ten flares for analysis which have durations between 5 and 20 hours, and size ranging from C to X GOES class. Employing the Soft X-ray Telescope, the Bragg Crystal Spectrometer, GOES spacecraft, and ground-based H_alpha data, we examine the morphology, temperature, emission measure, location of the hard X-ray source, non-thermal velocities and upflows of the plasma at different stages in the flare development. Our results are used to address the question of the energy source that maintains the hot plasma at temperatures of several million degrees for many hours. Title: 1st Advances in Solar Physics Euroconference: Advances in the Physics of Sunspots Authors: Schmieder, B.; del Toro Iniesta, J. C.; Vazquez, M. Bibcode: 1997ASPC..118.....S Altcode: 1997fasp.conf.....S No abstract at ADS Title: Dynamics and evolution of the post-flare loops of June 1992 Authors: Wiik, J. E.; van Driel-Gesztely, L.; Schmieder, B.; Heinzel, P. Bibcode: 1997AdSpR..20.2345W Altcode: Observations in X-rays (Yohkoh/SXT) and in Hα of a system of post-flare loops which developed after a flare on 25 June 1992 provide a unique set of data for a study of the relationship between the hot and cool post-flare loops as they evolve. Through a study of the magnetic configuration in which the flare occurred, we are able to reconstruct the true, 3D geometry of the loops. We derive the bulk-flow velocities along the loop as a function of height using Doppler velocities and the results from the loop reconstruction. We also provide a set of relative altitude data. These results are used to check the validity of the reconnection model in the frame of the cooling time needed to cool X-ray loops to Hα temperature. Title: Advances in the physics of sunspots. Poster contributions. 1st ASPE Meeting, Puerto de la Cruz, Tenerife (Spain), 2 - 6 Oct 1996. Authors: Schmieder, B. Bibcode: 1997joso.proc...47S Altcode: The invited reviews and contributed papers are published in the Astronomical Society of the Pacific Conference Series, Vol. 118. Title: Post-flare loops in the chromosphere and corona. Authors: van Driel-Gesztelyi, L.; Wiik, J. E.; Schmieder, B. Bibcode: 1997ASIC..494...85V Altcode: 1997topr.conf...85V Post-flare loops, which may last for several hours during the gradual phase of powerful flares, can provide spectacular limb events during solar eclipses. According to models, on-going magnetic reconnection keeps creating new loops at an ever-increasing altitude. The newly formed hot loops can cool down to chromospheric temperatures quickly, in a few minutes, or slowly, over a few hours, depending on their density. A good test of the model is to measure the altitude difference between loops observed at different wavelengths which show the loops at different stages of the cooling process. Title: "Prominences, filaments and chromospheric activity" June 1996 campaign with SOHO, YOHKOH and Wrocław. Authors: Wiik, J. E.; Rudawy, P.; Schmieder, B.; Kucera, T.; Rompolt, B.; Poland, A. Bibcode: 1997joso.proc...93W Altcode: No abstract at ADS Title: Flows Through the Magnetically Structured Solar Atmosphere Authors: Schmieder, B. Bibcode: 1997LNP...489..139S Altcode: 1997shpp.conf..139S The upper solar atmosphere until three solar radii is controlled by the magnetic field. The plasma β (P kin/P magn) is decreasing with increasing altitude in the low corona but is already less than unity in the middle chromosphere. The dynamics of the chromosphere and the transition region are driven by magnetic effects, even in the "quiet" Sun. We will review some promising research programs concerning steady flows and oscillatory phenomena in the small scale structures, mainly based on new two-dimensional spectral diagnostics. The filamentary behaviour of the solar atmosphere may be the key to understanding basic problems like coronal heating. The importance of the chromospheric network, plages and penumbra is emphasized by the fact that they represent footpoints of coronal loops. Largescale coronal structures (streamers, jets, post-flare loops, arcades) are linked to photospheric and chromospheric events and give a three-dimensional view of the atmosphere. Title: 3D Magnetic Reconnection at an X-Ray Bright Point Authors: Mandrini, C. H.; Démoulin, P.; Van Driel-Gesztelyi, L.; Schmieder, B.; Cauzzi, G.; Hofmann, A. Bibcode: 1996SoPh..168..115M Altcode: On May 1, 1993, a flaring X-ray bright point (XBP) was observed for about 16 hours in the old, disintegrating, bipolar active region (AR) NOAA 7493. During this period, a minor magnetic bipole (1020 Mx) emerged in the region. We have found observational evidence showing that the XBP brightenings were due to magnetic reconnection between the new bipole and pre-existing plage fields. The aim of the present work is to substantiate with magnetic modelling what has been shown by the observations. For this purpose we extrapolate the observed photospheric magnetic fields in the linear force-free approximation and follow its evolution during the lifetime of the XBP. From the computed coronal field lines we determine the location of regions of drastic change in field-line linkage, called `quasi-separatrix layers' or QSLs. QSLs are open layers that behave physically like separatrices: the break down of ideal magnetohydrodynamics and the release of free magnetic energy may occur at these locations when their thickness is small enough. The extrapolated field lines, with photospheric footpoints on both sides of QSLs, match the observed chromospheric and coronal structures (arch filament system, XBP and faint X-ray loops (FXL)). We study also the evolution of the width of the QSL located over the new negative polarity pore: the calculated QSL is very thin (typically less than 100 m) during the lifetime of the XBP, but becomes much thicker (≥ 104 m) after the XBP has faded. Furthermore we show that peaks in X-ray brightness propagate along the FXL with a velocity of ≈ 670 km s-1, starting from the XBP location, implying that the energy is released where the emerging bipole impacts against pre-existing coronal loops. We discuss the possible mechanism of energy transport and conclude that the energy is conducted to the remote footpoints of the FXL by a thermal front. These results strongly support the supposition that the XBP brightness and flaring are due to the interaction of different flux systems, through 3D magnetic reconnection, at QSLs. Title: Differential Magnetic Field Shear in an Active Region Authors: Schmieder, B.; Demoulin, P.; Aulanier, G.; Golub, L. Bibcode: 1996ApJ...467..881S Altcode: The three-dimensional extrapolation of magnetic field lines from a magneto gram obtained at Kitt Peak allows us to understand the global structure of the NOAA active region 6718, as observed in X-rays with the Normal Incidence X-ray Telescope (NIXT) and in Hα with the Multichannel Subtractive Double Pass spectrograph (MSDP) in Meudon on 1991 July 11. This active region was in a quiet stage. Bright X-ray loops connect plages having field strengths of ∼300 G, while Hα fibriles connect penumbrae having strong spot fields to the surrounding network. Small, intense X-ray features in the moat region around a large spot, which could be called X-ray-bright points, are due mainly to the emergence of magnetic flux and merging of these fields with surrounding ones. A set of large-scale, sheared X-ray loops is observed in the central part of the active region. Based on the fit between the observed coronal structure and the field configurations (and assuming a linear force-free field), we propose a differential magnetic field shear model for this active region. The decreasing shear in outer portions of the active region may indicate a continual relaxation of the magnetic field to a lower energy state in the progressively older portions of the AR. Title: Post-Flare Loops of 26 June 1992, III Authors: Wiik, J. E.; Schmieder, B.; Heinzel, P.; Roudier, T. Bibcode: 1996SoPh..166...89W Altcode: Post-flare loops were observed on June 26, 1992 in the Hα line with the Multichannel Subtractive Double-Pass spectrograph (MSDP) on Pic-du-Midi and with the Swedish telescope on La Palma. The highly dynamic loops are inhomogeneous (blobs). The cool loops were observed 10-12 hours after the X 3.9 class flare which had a maximum on June 25 at 20∶11 UT. From 2D images obtained with the MSDP on June 26 we derive Hα intensities and Doppler velocities of the loop plasma. Using a geometrical reconstruction technique we show that these loops are mainly perpendicular to the solar surface and have the shape of a dipole magnetic configuration. We derive the bulk-flow velocities along the loop as a function of height using the Doppler velocities and the results from the loop reconstruction. Where the Doppler velocities are too small, we derive the bulk-flow velocities from the displacements of the falling blobs. We discuss existing deviations from free-fall velocity in the lower parts of the loops. Title: Post-Flare Loops of 26 June 1992, II Authors: Schmieder, B.; Heinzel, P.; Van Driel-Gesztelyi, L.; Lemen, J. R. Bibcode: 1996SoPh..165..303S Altcode: We observed the large post-flare loop system, which developed after the X 3.9 flare of 25 June 1992 at 20∶11 UT, in Hα with the Multichannel Subtractive Double Pass Spectrograph at Pic-du-Midi and in X-rays with the it Yohkoh/SXT instrument. Following the long-term development of cool and hot plasmas, we have determined the emission measure of the cool plasma and, for the first time, the temporal evolution of the hot-loop emission measure and temperature during the entire gradual phase. Thus, it was possible to infer the temporal variation of electron densities, leading to estimates of cooling times. A gradual decrease of the hot-loop emission measure was observed, from 4 × 1030 cm−5 at 23∶00 UT on 25 June 1992 to 3 × 1028 cm−5 at 13∶10 UT on 26 June 1992. During the same period, the temperature decreased only slowly from 7.2 to 6.0 × 106 K. Using recent results of NLTE modeling of prominence-like plasmas, we also derive the emission measure of cool Hα loops and discuss their temperature and ionisation degree. During two hours of Hα observations (11-13 hours after the flare) the averaged emission measure does not show any significant change, though the amount of visible cool material decreases and the volume of the loops increases. The emission measure in Hα, after correction for the Doppler-brightening effect, is slightly lower than in soft X-rays. Since the hot plasma seems to be more spatially extended, we arrive at electron densities in the range ninfesupho≤ ninfesupcool∼ 2 × 1010 cm−3 at the time of the Hα observations. Title: Subflares and surges in AR 2744 during the Solar Maximum Mission. Authors: Schmieder, B.; Rovira, M.; Simnett, G. M.; Fontenla, J. M.; Tandberg-Hanssen, E. Bibcode: 1996A&A...308..957S Altcode: Active region NOAA 2744, which was at S25, had its central meridian passage on Oct 23 1980 and was relatively quiet according to Hα, UV and X-ray observations made by the Solar Maximum Mission (SMM). The region was also observed by the Marshall Space Flight Center (MSFC) vector magnetograph. During its disk passage only subflares and surges were detected. Their locations appeared to be governed by the magnetic topology. On October 21 a miniflare occurred close to the separator between the two main sunspots. On October 22 the emergence of a small region of parasitic polarity in the existing magnetic field appeared to be responsible for three subflares and subsequent surges. We discuss the energy budget for plasmas at temperatures in the 10^4^K, 10^5^K and 10^6^K ranges in the context of surge-trigger mechanisms. On October 21 the energy deposition driving the surges did not produce a high temperature plasma. By October 22 the active region had evolved and the surges were now associated with some high temperature plasma. However, the energy radiated at transition region temperatures would be larger than that estimated in X-rays depending on the dilution factor. This would imply a continuous influx of energy in order to sustain the long duration surge (30min) rather than a simple, impulsive energy input. If the electron density in the 10^4^-10^5^K plasma is taken as ~10^12^cm^-3^ the diameter of individual surge loops should only be ~40km. The relevance of our results to (a) reconnection and (b) gradient pressure driven models for surges is discussed. Title: Chromospheric ejections and their signatures in X-ray observed by YOHKOH Authors: Schmieder, B.; Mein, N.; Shibata, K.; van Driel-Gesztelyi, L.; Kurokawa, H. Bibcode: 1996AdSpR..17d.193S Altcode: 1996AdSpR..17..193S Surges, or condensations of chromospheric material, are commonly observed in active regions when new emerging magnetic flux (EMF) occurs. In order to study EMF-related phenomena in the corona, observing campaigns were organized with the Yohkoh X-ray satellite and ground based observatories. EMFs could be detected in magnetograms made in Potsdam and Hawaii, surge and arch filament system (AFS) events (on Oct 7 1991, May 1 1993, respectively) with the Multichannel Subtractive Double Pass instruments operating at Meudon and on the Canary Islands and with the Hida telescope at Kyoto University. Bright X-ray loops coincident with chromospheric surge activity were detected in the high resolution Yohkoh SXT images. We also found coincident brightness variations between an X-ray bright point (XBP) and the underlying chromospheric plage related to EMF. We interpret the appearance of AFS as condensation of material among magnetic field lines, the X-ray bright points as the result of a magnetic reconnection process, and surges as ejection of cold plasma bubbles squeezed between field lines as a result of reconnection. Title: Coordinated SPDE rocket, YOHKOH and ground observations of an emerging flux region and a filament Authors: Damé, L.; Martic, M.; Brown, W. A.; Bruner, M. E.; Strong, K.; Suematsu, Y.; Tsuneta, S.; Schmieder, B. Bibcode: 1996AdSpR..17d.189D Altcode: 1996AdSpR..17..189D During the first flight of the Solar Plasma Diagnostic Experiment (SPDE), May 12, 1992, we obtained UV filtergrams at high resolution (full Sun 0.82'' spatial resolution in the 160 nm continuum, the CIV lines and Lyman alpha) with the Ultraviolet Filtergrap Camera (UVFC). Closely coordinated observations were obtained with the Soft X-ray Telescope (SXT) of the Yohkoh satellite and from dedicated ground programs in particular at Sacramento Peak, La Palma and Pic-du-Midi observatories. With this unique set of data we cover the solar atmosphere as a whole, from the temperature minimum to the high corona with essential steps in the chromosphere and transition region. After the necessary calibrations of the data set, we present the first results of the multitemperature development of an emerging flux region and of a filament that rapidly changed right during the rocket short lifetime. Title: Structure and evolution of post-flare loops: analysis of YOHKOH and MSDP observations Authors: Schmieder, B.; Heinzel, P.; Wiik, J. E.; Lemen, J.; Hiei, E. Bibcode: 1996AdSpR..17d.111S Altcode: 1996AdSpR..17..111S Using coordinated observations of the June 26 1992 post-flare loops (Yohkoh-SXT and MSDP at Pic-du-Midi), we have analyzed the physical conditions in both hot and cool loops and studied their spatial structure and temporal evolution. Coalignment of high-resolution images from SXT and MSDP indicates that the cool Hα loops are located just below the hot ones and that the whole loop system grows in time with a velocity 1.4 km s^-1. The temperature of hot loops as derived from SXT data amounts to 5 x 10^6 K, while the cool loops have temperatures around 10^4 K. The electron density of hot loops was estimated from SXT emission-measure analysis to 7 x 10^9 cm^-3, while Hα integrated intensity gives an electron density in cool loops of 2.2 x 10^10 cm^-3. With these plasma parameters we have solved the energy equation in order to estimate the cooling time. The basic result of this work is that the cooling time is comparable to the characteristic growing time of the loop system (~ 1500 - 2000 sec), which is in agreement with the scenario of the post-flare loop system development. Title: High resolution Lyalpha images obtained with the transition region camera (TRC): a comparison with Hα observations Authors: Wiik, J. E.; Foing, B. H.; Martens, P.; Fleck, B.; Schmieder, B. Bibcode: 1996AdSpR..17d.105W Altcode: 1996AdSpR..17..105W Comparing high spatial resolution (~ 1'') images observed in Lyalpha with the Transition Region Camera (TRC) and in Hα at Sacramento Peak and Meudon Observatories, we notice that some structures are well correlated in the two lines (plages), while others are less correlated (chromospheric network, filaments). This is an indication of the inhomogeneous distribution of physical parameters in these structures. Title: Observations and Analysis of Surges in Chromosphere and Lower Corona Authors: Kotrc, P.; Schmieder, B.; Karlický, M.; Heinzel, P. Bibcode: 1996RoAJ....6...69K Altcode: No abstract at ADS Title: X-Ray Bright Point Flares Due to Magnetic Reconnection Authors: Van Driel-Gesztelyi, L.; Schmieder, B.; Cauzzi, G.; Mein, N.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, P.; Staiger, J. Bibcode: 1996SoPh..163..145V Altcode: Ground-based optical observations coordinated with Yohkoh/SXT X-ray observations of an old, disintegrating bipolar active region AR NOAA 7493 (May 1, 1993) provided a multiwavelength data base to study a flaring `active region' X-ray bright point (XBP) of about 16 hr lifetime, and the activity related to it in different layers of the solar atmosphere. The XBP appeared to be related to a new minor bipole of about 1020 Mx. Superposed on a global evolution of soft X-ray brightness, the XBP displayed changes of brightness, lasting for 1-10 min. During the brightenings the XBP apparently had a spatial structure, which was (tiny) loop-like rather than point-like. The X-ray brightenings were correlated with chromospheric activity: (i) brightenings of underlying chromospheric faculae, and (ii) appearance of strong turbulent velocities in the arch filament system. We propose that the XBP brightenings were due to reconnection of the magnetic field lines (sketched in 3D) between the new bipole and a pre-existing plage field induced by the motion of one of the new pores (v = 0.2 km s−1) towards the plage, and that the XBP itself was a reconnected hot loop between them. Title: Hot and Cool Post-Flare Loops: Formation and Dynamics Authors: Schmieder, B.; Heinzel, P.; van Driel-Gesztelyi, L.; Wiik, J. E.; Lemen, J. Bibcode: 1996mpsa.conf..211S Altcode: 1996IAUCo.153..211S No abstract at ADS Title: Reconexión magnética en una región activa en decaimiento Authors: Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.; Schmieder, B.; Bagalá, L. G.; Rovira, M. G. Bibcode: 1996BAAA...40....5M Altcode: Se han obtenido observaciones desde Tierra (Hα y magnetogramas) coordinadas con el Soft X-ray Telescope (SXT), a bordo del satélite japonés Yohkoh, de una región activa bipolar en decaimiento. Estos datos constituyen la base para el estudio de un punto brillante en rayos X (PBX) y de la actividad relacionada con el mismo en distintas capas de la atmósfera solar. Las observaciones muestran que el PBX está relacionado con la aparición de un bipolo menor (~ 1020 Mx) y que su abrillantamiento continuo, así como sus aumentos de brillo esporádicos (``fulguraciones"), son el resultado de la reconexión entre el pequeño arco emergente (visto en Hα como un sistema de filamentos arqueados, SFA) y arcos mayores asociados al campo facular preexistente. Se ha extrapolado el campo magnético observado en la aproximación libre de fuerzas lineal y se ha seguido su evolución a lo largo de la vida del PBX. Se ha calculado la posición de las cuasiseparatrices (CSs) a partir del campo modelado. Las líneas de campo extrapoladas, cuyas bases fotosféricas se encuentran a ambos lados de las CSs, están de acuerdo con las estructuras cromosféricas y coronales observadas. Se ha calculado el espesor de la CD ubicada a lo largo de la polaridad negativa emergente, encontrándose que su variación está de acuerdo con la evolución de la intensidad del PBX; la CS es muy delgada durante la vida del PBX (~ 100 m), mientras que su espesor aumenta considerablemente (>= 10^4 m) cuando el PBX desaparece de las imágenes del SXT. Estos resultados señalan que el abrillantamiento y las ``fulguraciones" de este PBX se deben al proceso de reconexión en 3D que tiene lugar en las CSs. Title: Relative Altitude of Hot and Cool Post-Flare Loops Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Wiik, J. E.; Tarbell, T.; Heinzel, P.; Kitai, R.; Funakoshi, Y.; Anwar, B. Bibcode: 1996ASPC..111..359V Altcode: 1997ASPC..111..359V The authors collected a unique set of data obtained simultaneously at 4 different ground based observatories and with the Yohkoh satellite to study the relationship between hot X-ray and cool Hα post-flare loops as they evolved during the long gradual phase of the X3.9 flare which occurred on 25 June 1992. They found reasonably good agreement between the computed 'theoretical' cooling times and the 'observed' cooling times derived from the relative altitudes of hot and cool loops. Taking into account evolutionary effects, the authors also found similar shape and configuration of hot and cool loops during the entire observing period and confirmed that at any time hot loops are at higher altitude than cool loops, suggesting that cool loops indeed descend from hot loops. The results provide support for the reconnection model. Title: Signatures of New Emerging Flux in the Solar Atmosphere Authors: Schmieder, B.; Malherbe, J. M.; Mein, P.; Mein, N.; van Driel-Gesztelyi, L.; Roudier, T.; Nitta, N.; Harra-Murnion, L. K. Bibcode: 1996ASPC..111...43S Altcode: 1997ASPC..111...43S The emergence of new flux in the low atmosphere leads to magnetic reconnection of field lines. In a stable phase the phenomenon is observed in the chromosphere by the formation of dark filaments (arch filament system, AFS). The authors show how bright loops visible in soft X-rays are co-aligned with the AFS. Different types of events appear as the released energy increases. With less energetic phenomena than flares one observes surges, jets or X-ray bright points, according to the configuration of the field lines (open/closed). A low-level reconnection process is detectable as an X-ray bright point. If the energy is ≡1028ergs cm-3, one observes subflares. The authors document their statement by showing examples observed in coordinated observations obtained with the MSDP (Pic du Midi and Tenerife) and Yohkoh/SXT and BCS for the events occurring on Oct 5, 1994, Oct 27, 1993, and May 1, 1993. Title: 3D Magnetic Reconnection: Example of an X-Ray Bright Point Authors: Demoulin, P.; Mandrini, C. H.; van Driel-Gesztelyi, L.; Priest, E. R.; Henoux, J. C.; Schmieder, B. Bibcode: 1996ASPC..111...49D Altcode: 1997ASPC..111...49D In the classical view magnetic reconnection occurs at neutral points and implies transport of magnetic field-lines across separatrices. The authors show that reconnection may also occur in the absence of neutral points at so-called "quasi-separatrix layers" (QSLs), where there is a steep gradient in field-line linkage at the boundaries. Reconnection occurs in QSLs where the field-line velocity becomes larger than the allowed maximal plasma velocity or where the electric-current density becomes too great. The authors describe both a theoretical and an observed configuration. In the case of a simple sheared X-field they show that even a smooth continuous shear flow, imposed at the boundary, gives strong plasma jetting inside and parallel to the QSLs. Applying the QSL method to an X-ray bright point observed by Yohkoh, they find field lines in the extrapolated field which are on both sides of QSLs and which are in good agreement with loops observed in Hα and X-rays related to emerging flux. The evolution of the QSL width may explain the brightness evolution of the XBP. Title: Emerging Flux, Reconnection, and XBP Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Demoulin, P.; Mandrini, C.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, N.; Mein, P. Bibcode: 1996mpsa.conf..459V Altcode: 1996IAUCo.153..459V No abstract at ADS Title: Emerging flux seen by Yohkoh. Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Mandrini, C.; Démoulin, P.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, N.; Mein, P. Bibcode: 1996joso.proc..124V Altcode: No abstract at ADS Title: Ultraviolet Observations of the Structure and Dynamics of an Active Region at the Limb Authors: Korendyke, C. M.; Dere, K. P.; Socker, D. G.; Brueckner, G. E.; Schmieder, B. Bibcode: 1995ApJ...443..869K Altcode: The structure and dynamics of active region NOAA 7260 at the limb have been studied using ultraviolet spectra and spectroheliograms obtained during the eighth rocket flight of the Naval Research Laboratory's High Resolution Telescope an Spectrograph (HRTS). The instrument configuration included a narrow-bandpass spectroheliograph to observe the Sun in the lines of C IV lambda 550 and a tandem-Wadsworth mount spectrograph to record the profiles of chromospheric transition region and coronal lines in the 1850-2670 A region. The combination of high spatial resolution and high spectral purity C IV slit jaw images with ultraviolet emission-line spectra corresponding allows examination of a variety of active region phenomena. A time series of spectroheliograms shows large-scale loop systems composed of fine-scale threads with some extending up to 100 Mm above the limb. The proper motion of several supersonic features, including a surge were measured. The accelerated plasmas appear in several different geometries and environments. Spectrograph exposures were taken with the slit positioned at a range of altitudes above the limb and provide a direct comparison between coronal, transition region and chromospheric emission line profiles. The spectral profiles of chromospheric and transition region emission lines show line-of-sight velocities up to 70 km/s. These lower temperature, emission-line spectra show small-scale spatial and velocity variations which are correlated with the threadlike structures seen in C IV. Coronal lines of Fe XII show much lower velocities and no fine structure. Title: Hα surges and associated Soft X-ray loops Authors: Schmieder, B.; Shibata, K.; van Driel-Gesztelyi, L.; Freeland, S. Bibcode: 1995SoPh..156..245S Altcode: A recurrent Hα surge was observed on 7 October, 1991 on the western solar limb with the Meudon MSDP spectrograph. The GOES satellite recorded X-ray subflares coincident with all three events. During two of the surges high-resolutionYohkoh Soft X-ray Telescope (SXT) images have been taken. Low X-ray loops overlying the active region where the surges occurred were continuously restructuring. A flare loop appeared at the onset of each surge event and somewhat separated from the footpoint of the surge. The loops are interpreted as causally related to the surges. It is suggested that surges are due to magnetic reconnection between a twisted cool loop and open field lines. Cold plasma bubbles or jets squeezed among untwisting magnetic field lines could correspond to the surge material. No detection was made of either X-ray emission along the path of the surges or X-ray jets, possibly because of the finite detection threshold of theYohkoh SXT. Title: Relation between Cool and Hot Post-Flare Loops of 26 June 1992 Derived from Optical and X-Ray (SXT-YOHKOH) Observations Authors: Schmieder, B.; Heinzel, P.; Wiik, J. E.; Lemen, J.; Anwar, B.; Kotrc, P.; Hiei, E. Bibcode: 1995SoPh..156..337S Altcode: We have analyzed the physical conditions of the plasma in post-flare loops with special emphasis on dynamics and energy transport using SXT-data (hot plasma) and optical ground-based data from Pic du Midi, Wrocław, and Ondřejov (cool plasma). By combining the Hα observations with the SXT images we can understand the relationship between cool and hot plasmas, the process of cooling post-flare loops and the mechanism which maintains the long duration of these loops. Using recent results of NLTE modeling of prominence-like plasmas, we derive the emission measure of cool Hα loops and this gives us a realistic estimate of the electron density (2.2 × 1010 cm−3). Then, by comparing this emission measure with that of hot loops derived from SXT data, we are able to estimate the ratio between electron densities in hot and cool loops taking into account the effect of geometrical filling factors. This leads to the electron density in hot loops 7 × 109 cm−3. We also derive the temperature of hot X-ray loops (≃ 5.5 × 106 K), which, together with the electron density, provides the initial values for solving the time-dependent energy balance equation. We obtain the cooling times which are compared to a typical growth-time of the whole loop system (∼ 2000 s). In the legs of cool Hα loops, we observe an excess of the emission measure which we attribute to the effect of Doppler brightening (due to large downflow velocities). Title: Preparing for SOHO: results from the transition region camera Authors: Wiik, J. E.; Foing, B. H.; Schmieder, B.; Martens, P.; Fleck, B. Bibcode: 1994ESASP.373..433W Altcode: 1994soho....3..433W No abstract at ADS Title: THEMIS: its capabilities and key programs Authors: Schmieder, B.; Mein, P. Bibcode: 1994ESASP.373..393S Altcode: 1994soho....3..393S No abstract at ADS Title: Dynamics of post-flare loops observed on June 26, 1992 Authors: Wiik, J. E.; Schmieder, B.; Heinzel, P.; Roudier, T. Bibcode: 1994ESASP.373..207W Altcode: 1994soho....3..207W No abstract at ADS Title: Dynamical fine structures of the chromosphere Authors: Tsiropoula, G.; Schmieder, B.; Alissandrakis, C. E. Bibcode: 1994SSRv...70...65T Altcode: We have studied the spatial structure and temporal evolution of a chromospheric region with chains of mottles at the junction of three supergranules. The observations were obtained with the Multichannel Subtractive Double Pass spectrograph operating in Hα at the Pic du Midi Observatory. From a statistical point of view the fine structures were stable in intensity over the observation period (15 min), while the line of sight velocity showed remarkable changes within a few minutes. A detailed analysis shows that the predominant pattern of bulk motion in the dark mottles is that of downflow at their footpoints and upflow at their tops, which is followed by downflows along the whole structure and that this process repeats itself several times during their lifetime. Title: Hierarchy of spatial scale sin UV prominences Authors: Schmieder, B.; Wiik, J. E.; Dere, K. P. Bibcode: 1994SSRv...70..175S Altcode: Ultraviolet spectra of a quiescent prominence observed with theHigh Resolution Telescope and Spectrograph (HRTS) are analyzed. Different techniques lead to greatly different spatial scales for the prominence structures. The UV spectra show strong variations in intensity and Doppler shift on scales larger than 1700 km. Spectroscopic diagnostics employing line intensity ratios indicate the existence of scales between 400 m to some hundred kilometers. We attempt to interpret various aspects of the prominence intensities and velocities with a multiple thread model. Title: Coordinated optical and YOHKOH observations of 26 June 1992 flare loops Authors: Heinzel, P.; Kotrč, P.; Schmieder, B.; Hiei, E.; Anwar, B. Bibcode: 1994SSRv...70..181H Altcode: Optical spectra of large flare loops were detected by the Ondřejov Multichannel Flare Spectrograph (MFS) during coordinated observations with MSDP at Pic du Midi (Hα) and the soft X-ray telescope (SXT) on Yohkoh. The CCD video images taken by the MFS slit-jaw camera document the time-development of the flare loops as seen through the Hα filter. Preliminary analysis of the MSDP images shows the intensity structure of the cool flare loops and their velocity fields. From the spectra we can clearly see the intensity variations along the cool loops. SXT images show the structure of hot X-ray loops similar to that of cool loops. Special attention is devoted to the bright tops, simultaneously observed in X-rays, Hα and other optical lines. Based on a preliminary analysis of the optical spectra, we speculate about possible mechanisms leading to an observed bright emission at the tops of cool loops. We suggest that direct soft X-ray irradiation of cool loops at their tops could be, at least partly, responsible for such a strong brightening. Title: Time evolution of fine structures in the solar chromosphere. Authors: Tsiropoula, G.; Alissandrakis, C. E.; Schmieder, B. Bibcode: 1994A&A...290..285T Altcode: We have studied the temporal evolution of two quiet chromospheric regions, one with a typical rosette and another with chains of mottles at the junction of three supergranules. The observations were obtained during 15 minutes with the Multichannel Subtractive Double Pass spectrograph (MSDP) operating in Hα at the Pic du Midi Observatory. We derived intensity maps and Doppler shift velocities at different wavelengths along the Hα profile over a two dimensional field of view. The observed contrast profiles were matched with theoretical contrast profiles using Beckers' cloud model for a more accurate determination of the line of sight velocity. A statistical analysis with cross correlation functions showed that the fine structures were stable in intensity over the observation period (15 min), but the line of sight velocity showed important changes within a few minutes. A detailed analysis of the velocities along the axes of dark mottles showed that the predominant pattern of bulk motion is that of downflow at their footpoints and alternating phases of upflow and downflow at their tops. This motion is consistent with Pikel'ner's model for spicules, which attributes this pattern to the reconnection of opposite magnetic filed lines. This picture is also consistent with the velocity reversals with time observed in spicules and may be associated to the systematic downflows observed in the transition region. Doppler shift velocities in dark mottles are too low compared to those derived with the cloud model; the latter are comparable to those reported for spicules, strengthening the view that these structures are identical. Title: Energy Transport and Dynamics Authors: Schmieder, B.; Peres, G.; Enome, S.; Falciani, R.; Heinzel, P.; Hénoux, J. C.; Mariska, J.; Reale, F.; Rilee, M. L.; Rompolt, B.; Shibasaki, K.; Stepanov, A. V.; Wülser, J. P.; Zarro, D.; Zharkova, V. Bibcode: 1994SoPh..153...55S Altcode: We report findings concerning energy transport and dynamics in flares during the impulsive and gradual phases based on new ground-based and space observations (notably fromYohkoh). A preheating sometimes occurs during the impulsive phase. CaXIX line shifts are confirmed to be good tracers of bulk plasma motions, although strong blue shifts are not as frequent as previously claimed. They often appear correlated with hard X-rays but, forsome events, the concept that electron beams provide the whole energy input to the thermal component seems not to apply. Theory now yields: new diagnostics of low-energy proton and electron beams; accurate hydrodynamical modeling of pulse beam heating of the atmosphere; possible diagnostics of microflares (based on X-ray line ratio or on loop variability); and simulated images of chromospheric evaporation fronts. For the gradual phase, the continual reorganization of magnetic field lines over active regions determines where and when magnetic reconnection, the mechanism favoured for energy release, will occur. Spatial and temporal fragmentation of the energy release, observed at different wavelengths, is considered to be a factor as well in energy transport and plasma dynamics. Title: Coronal Structures Observed in X-rays (NIXT) and H_alpha Surges Authors: Schmieder, B.; Mouradian, Z.; Golub, L.; Antiochos, S. Bibcode: 1994kofu.symp..317S Altcode: Ground-based coordinated observations with the Multichannel subtractive double pass spectrograph (MSDP) and the heliograph in Meudon allowed us to portray the chromospheric intensity and velocity fields below coronal structures observed with the Normal Incidence X-ray Telescope (NIXT). On July 11, 1991 (eclipse day) we have identified in AR 6713 (N38 W 42) the X-ray signatures of the network, subflares, filaments and surges. The largest H_alpha surge has only weak emission in X-ray, while a weak H_alpha feature corresponds to a very bright x-ray subflare. We calculate the emission measures of these events and give some constraints on the triggering mechanisms of surges. Title: Microflares and their Related Events Authors: Schmieder, B.; Fontenla, J.; Tandberg-Hanssen, E.; Simnett, G. M. Bibcode: 1994kofu.symp..339S Altcode: We have studied in detail two series of events that occur in two separate active regions on October 9 and June 15, 1980 during the period of SMM observations. These events can be considered as typical of a class of solar compact subflares. The events have been studied using simultaneous UVSP (C IV) and Meudon (H_alpha) data, and for the brighter event we also use X-ray data from HXIS. Characteristics of microflares are derived. The simplest microflare may be composed of a large number of small events, some of which appear to be triggered by earlier events in the same series. Title: Evolution of Active Regions Leading to Flares Authors: Schmieder, B.; Demoulin, P.; Henoux, J. -C.; Driel-Gesztelyi, L. V.; Mandrini, C.; Rovira, M. Bibcode: 1994kofu.symp..297S Altcode: We model observed longitudinal magnetic fields obtained in Potsdam, Meudon, MSFC Hunstville by a series of magnetic sources located below the photosphere. H_alpha flare kernels are found situated on intersecting separatrices (surfaces delimiting regions of different magnetic connectivities). We deduce that energy release occurs mainly at the separator by magnetic reconnection. Evidence for both neutralized and un-neutralized currents are observed in different flaring regions. Moreover we have found two photospheric currents of opposite sign, linked in the corona by field lines, at the border of flare kernels. Title: Observational support of reconnection in solar flares Authors: Démoulin, P.; Hénoux, J. C.; Schmieder, B.; Mandrini, C. H.; Rovira, M. G.; Somov, B. Bibcode: 1994SSRv...68..129D Altcode: We present a detailed analysis of the magnetic topology of flaring active region. TheH α kernels are found to be located at the intersection of the separatrices with the chromosphere when the shear, deduced from the fibrils or/and transverse magnetic field direction, is taken into account. We show that the kernels are magnetically connected by field lines passing close to the separator. We confirm, for other flares, previous studies which show that photospheric current concentrations are located at the borders of flare ribbons. Moreover we found two photospheric current concentrations of opposite sign, linked in the corona by field lines which follow separatrices. These give evidence that magnetic energy is released by reconnection processes in solar flares. Title: Erratum: A study of surges and flares within an active region Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Gerlei, O.; Simnett, G. M. Bibcode: 1994SoPh..151..399S Altcode: No abstract at ADS Title: Comparison between Cool and Hot Plasma Behaviors of Surges Authors: Schmieder, B.; Golub, L.; Antiochos, S. K. Bibcode: 1994ApJ...425..326S Altcode: Ground-based coordinated observations with the Multichannel Subtractive Double Pass spectrograph (MSDP) allowed us to obtain chromospheric intensity and velocity field maps below coronal structures during the launch of the NIXT payload on 1991 July 11 (eclipse day). A large H-alpha ejection in AR 6713 (N38 W40) was detected during the NIXT flight. However, only a low level of X-ray emission was associated with this event. In contrast, bright X-ray emission associated with a subflare was observed in a nearby active region, but with only a weak associated ejection in H-alpha. A discussion of both of these events gives strong constraints on the triggering mechanisms of surges. Title: Time Evolution of a Miniflare as Seen in H alpha , UV Lines, and X-Rays Authors: Fontenla, J.; Schmieder, B.; Simnett, G. M.; Tandberg-Hanssen, E. Bibcode: 1994ApJ...424.1022F Altcode: A miniflare that occurred in active region Hale 16896 on 1980 June 15 was observed in H-alpha, UV lines, and soft X-rays. These data allow us to analyze the flare emission and derive the energetics and dynamics of the chromospheric plasma involved. Our results indicate that the energy released by the miniflare was about 1028 ergs, about four orders of magnitude smaller than that of a large flare. However, hard X-rays (5.5-8.0 keV) were observed which indicated a plasma with temperature as high as 27 x 106 K. The H-alpha wings, C IV, and X-rays all showed a short-lived and compact (3 sec x 3 sec) brightening in a location near the leading sunspot. At this location, small-scale changes in the magnetic field were observed from about 2 hr before to about 6 hr after the miniflare. Only very small velocities seem to have been associated with most of the event in H-alpha. The data are consistent with short and dense loops at temperatures above 107 K which lost a large fraction of their energy via downward conduction through regions at the footpoints. Several secondary events appear to have been triggered by the miniflare along an arch filament which itself was not greatly affected. A number of much less energetic (1025-1026 erg) events preceded and followed the mini-flare. One of these occurred 11 minutes after the mini-flare and displayed a highly Doppler-shifted signature from the foot-point of a C IV arch. This arch delineates the connection that existed between the location of the mini-flare and the location of secondary events triggered by the flare. Title: Relationship between magnetic field evolution and flaring sites in AR 6659 in June 1991 Authors: Schmieder, B.; Hagyard, M. J.; Guoxiang, Ai; Hongqi, Zhang; Kalman, B.; Gyori, L.; Rompolt, B.; Demoulin, P.; Machado, M. E. Bibcode: 1994SoPh..150..199S Altcode: During the international campaign of June 1991, the active region AR 6659 produced six very large, long-duration flares (X10/12) during its passage across the solar disk. We present the characteristics of four of them (June 4, 6, 9, 15). Precise measurements of the spot motions from Debrecen and Tokyo white-light pictures are used to understand the fragmentation of the main sunspot group with time. This fragmentation leads to a continuous restructuring of the magnetic field pattern while rapid changes are evidenced due to fast new flux emergence (magnetograms of MFSC, Huairou). The first process leads to a shearing of the field lines along which there is energy storage; the second one is the trigger which causes the release of energy by creating a complex topology. We conjecture that these two processes with different time scales are relevant to the production of flares. Title: Relationship between electric currents, photospheric motions, chromospheric activity, and magnetic field topology Authors: van Driel-Gesztelyi, L.; Hofmann, A.; Demoulin, P.; Schmieder, B.; Csepura, G. Bibcode: 1994SoPh..149..309V Altcode: Through coordinated observations made during the Max'91 campaign in June 1989 in Potsdam (magnetograms), Debrecen (white light and Hα), and Meudon (MSDP), we follow the evolution of the sunspot group in active region NOAA 5555 for 6 days. The topology of the coronal magnetic field is investigated by using a method based on the concept of separatrices - applied previously (Mandriniet al., 1991) to a magnetic region slightly distorted by field-aligned currents. The present active region differs by having significant magnetic shear. We find that the Hα flare kernels and the main photospheric electric current cells are located close to the intersection of the separatrices with the chromosphere, in a linear force-free field configuration adapted to the observed shear. Sunspot motions, strong currents, isolated polarities, or intersecting separatrices are not in themselves sufficient to produce a flare. A combination of them all is required. This supports the idea that flares are due to magnetic reconnection, when flux tubes with field-aligned currents move towards the separatrix locations. Title: Chromospheric fine structure: Black & white mottles Authors: Heinzel, P.; Schmieder, B. Bibcode: 1994A&A...282..939H Altcode: H-alpha observations of the chromosphere have been obtained on June 17, 1986 with a high spatial resolution using the MSDP (Multichannel Subtractive Double Pass) spectrograph operating at Pic du Midi observatory. Various fine structures are observed in the chromosphere: bushes of fibrils around supergranules and fibrils (mottles) in the rosettes. They are relatively stable, but line-of-sight velocities +/- 5-10 km/s are observed at the boundaries of supergranules (rosettes). Velocity images exhibit finer structures than intensity ones, with no cospatial relationship between both of them. Typical H-alpha line profiles of dark and bright (black & white) mottles, constructed from 11 MSDP channels, are used to derive the physical conditions in these structures. Non-local thermodynamic equilibrium (NLTE) models of dark and bright mottles are represented by a grid of prominence-like models of Goutebroze et al. (1993). It is demonstrated that higher-pressure models(pg approximately = 0.5-1 dyn/sq cm) with temperature around 104 K naturally explain the profiles of both dark and bright structures. By introducing a generalized two-cloud model with non-uniform source function, we account schematically for a shear-type velocity field. However, the velocities are found to be of a secondary importance when the broad U-shaped profiles formation is considered. We conclude that dark and bright mottles have a similar nature and that their brightness difference is predominantly due to pressure variations of the plasma injected into the rosette flux tubes. Finally, we discuss the ambiguity of H-alpha contrast profiles and comment on applicability of the classical cloud model. Title: Interpretation of Magnetic Field Structures of AR 6659 in June 7-10; 1991 Authors: Wu, S. T.; Weng, F. S.; Hagyard, M. J.; Machado, M.; Schmieder, B. Bibcode: 1994scs..conf..201W Altcode: 1994IAUCo.144..201W The authors examine the magnetic structures in AR 6659 by using the observation of vector magnetic fields obtained at MSFC/NASA. The structure of coronal loops is revealed. The authors also computed the total magnetic energy vs time of this region. It shows that there is indeed enough energy to propel the numerous, energetic flares that were observed in this region. Title: Fine structures of the solar chromosphere Authors: Schmieder, B.; Heinzel, P.; Tsiropoula, G.; Alessandrakis, C. E. Bibcode: 1994ASIC..433..151S Altcode: No abstract at ADS Title: Coronal Cavities Observed Around Prominences Authors: Wiik, J. E.; Schmieder, B.; Noëns, J. -C. Bibcode: 1994emsp.conf..167W Altcode: No abstract at ADS Title: Time Evolution of Chromospheric Fine Structures Authors: Tsiropoula, G.; Alissandrakis, C. E.; Schmieder, B. Bibcode: 1994emsp.conf..111T Altcode: No abstract at ADS Title: Electron Densities in Solar Prominences Authors: Wiik, J. E.; Heinzel, P.; Schmieder, B. Bibcode: 1994scs..conf..381W Altcode: 1994IAUCo.144..381W The authors concentrate on the determination of electron densities, using the MSDP spectrograph at Pic du Midi. They discuss a new approach for diagnosing the electron densities by comparing the observed Hα intensities with theoretically predicted variations of the line-center intensity versus Ne. Title: Coronal Structures Observed in X-Rays (NIXT) and Hα Surges Authors: Schmieder, B.; Mouradian, Z.; Golub, L.; Antiochos, S. Bibcode: 1994emsp.conf..159S Altcode: No abstract at ADS Title: Black and White Mottles Authors: Heinzel, P.; Schmieder, B. Bibcode: 1994emsp.conf...81H Altcode: No abstract at ADS Title: Coronal Environment of Quiescent Prominences Authors: Wiik, J. E.; Schmieder, B.; Noens, J. C. Bibcode: 1994SoPh..149...51W Altcode: With thespectro-coronagraph and themultichannel subtractive double pass spectrograph (MSDP) at the Pic du Midi Observatory two quiescent prominences were observed simultaneously. From the spectro-coronagraph observations 2D maps of HeI λ 10830 å, FeXIII λ 10798 and 10747 å line intensities were obtained. In addition, we obtained 2D maps of the ratioR of the two iron lines. This ratio is used as a diagnostic for determining the density of the hot coronal plasma surrounding prominences. We found that the electron density is higher at the location of the prominences than in the corona, whereas small regions (∼40″) of lower electron density are unevenly distributed around the prominences indicating that the surrounding corona is highly inhomogeneous. The density of the cavity is reduced by a factor 1.5 compared to the density of the prominence environment (∼5 × 108 cm−3). We discuss the existence of cavities around these prominences according to the orientation of their axes relative to the line of sight and according to the velocity field inside the prominences. Constraints on models for prominence formation are derived. Title: Poster Papers presented at the Seventh European Meeting on Solar Physics Authors: Belvedere, G.; Rodonó, M.; Schmieder, B.; Simnett, G. M. Bibcode: 1994emsp.conf.....B Altcode: No abstract at ADS Title: Twisted Flux Tubes and Sunspot Motions in AR 5555 Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Schmieder, B.; Hofmann, A.; Csepura, G. Bibcode: 1994emsp.conf..115V Altcode: No abstract at ADS Title: Sites of flares and filaments in solar active regions Authors: Schmieder, B.; van-Driel, L.; Hofmann, A.; Démoulin, P.; Hénoux, J. C.; Hagyard, M. Bibcode: 1993AdSpR..13i.119S Altcode: 1993AdSpR..13..119S We applied a method developed to derive from magnetic field data the location of energy release in solar active regions. This method has been applied to two sets of data (June 13-15 1980 and June 23-25 1989) using magnetograms (Meudon, MSFC, Potsdam) and Hα data (Debrecen, MSDP Meudon). The Hα flares are located at intersections of the separatrices with the chromosphere in places where high density currents are observed. This supports the idea that the energy released in flares is due to magnetic reconnection at the location of a separator and subsequently transported to the chromosphere along field lines. It is found that strong magnetic shear is a necessary condition for filament formation. Magnetic shear merely determines the importance of the flare and is certainly not a necessary condition for flare activity. Title: Relationship between magnetic field evolution and flaring sites in AR 6659 on June 1991 Authors: Schmieder, B.; Démoulin, P.; Hagyard, M.; Machado, M. E.; Guo, Xiang Ai; Zhang, Hongqi; Fu, Qijun; Zhi, Kai Li; Luan, Ti; Kalman, B.; Györi, L. Bibcode: 1993AdSpR..13i.123S Altcode: 1993AdSpR..13..123S During the international campaign of June 1991, the active region AR 6659 produced 6 very large long duration flares at the same location during its passage across the solar disk. Vector magnetograms were obtained at Marshall (Huntsville) and Huairou Station (Beijing) with a time difference of 10 to 12 hours, thus giving a good survey of the magnetic field evolution with time. The flare of June 6/01:08 UT (X12 plus/4B) was observed in Shahe Station (Beijing) in white light, in Hα and in radio centimetric wavelengths. The evolution of the flare of June 9/01:43 UT (X10/3B) has been followed in Hα at the Yunnan Observatory (Kunming). An other one was well observed on June 15 at 08:20 UT in Wroclaw and in Debrecen. Some subflares were observed at Sac Peak on June 4, 5, 7 at Meudon on June 10, 14 and Debrecen on June 12 and 13.

In this short communication we concentrate on the relationship between magnetic field shear and flare sites. Title: Correlation of He II lyman alpha with He I 10830 Å, and with chromospheric and EUV coronal emission Authors: Thompson, W. T.; Neupert, W. M.; Jordan, S. D.; Jones, H.; Thomas, R. J.; Schmieder, B. Bibcode: 1993SoPh..147...29T Altcode: This paper describes the results of comparing SERTS-3 images obtained in the transition region line of HeII 304 å with chromospheric HeI 10830 å absorption, with strong coronal lines of MgIX 368 å, FeXV 284 å and 417 å, and FeXVI 335 å and 31 å, with Hα, with CaII 8542 å, and with magnetograms in FeI 8688Hα. All of the images are illustrated, and the image reconstruction techniques used are described and evaluated. The high correlation of the HeII 304 å and HeI 10830 å images, originally found by Harvey and Sheeley (1977), is confirmed and is put on a quantitative basis. We find that the supergranulation network has greater contrast, and that filaments appear darker, in 10830 å than in 304 å. In active regions, the 304 å line follows more closely the behavior of Hα and CaII 8542 å than the 10830 å line. Title: A Study of Surges and Flares Within an Active Region Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Gerlei, O.; Simnett, G. M. Bibcode: 1993SoPh..146..163S Altcode: Active region 2684 was observed by the Solar Maximum Mission and ground-based observatories simultaneously for over 12 hours on September 23, 1980. During these observations, recurrent surges were detected above an area with complex parasitic magnetic polarity located at the periphery of the active region. The time evolution of the Hα surges, CIV brightenings and X-ray spikes leads to the conclusion that the energy source is in the corona, from magnetic reconnection. The energy is transported by energetic charged particles along the loops, thereby heating the chromosphere as the particles lose their energy. The divergent motion of the spots corresponding to small dipoles at the base of the surge indicates that there is important magnetic reorganisation. According to the magnetic field-line configuration (large loop or open structures), X-rays can (or cannot) be associated with surges. Title: UV prominences observed with the HRTS: structure and physical properties Authors: Wiik, J. E.; Dere, K.; Schmieder, B. Bibcode: 1993A&A...273..267W Altcode: Ultraviolet spectra of two quiescent prominences (PL1, PL2) observed with the High Resolution Telescope and Spectrograph (HRTS) are described and analyzed. Meudon synoptic maps and spectroheliograms indicate that prominence PL 1 was extremely active during the flight and that material ejections were likely. PL2 appeared to be a more stable prominence. The significant differences between the spectra of the two prominences can perhaps be explained by their levels of activity. The spectrum of the more active prominence PL1 is dominated by transition zone lines formed near 105 K whereas the second prominence PL2 shows considerable emission of cooler chromospheric lines formed near 2 × 1O4 K. PL 1 also exhibits larger bulk flow velocities (up to ∼ 30 km s-1) and non-thermal velocities (∼20km s-1). From line ratios (O IV, N V, N IV, Si IV) a relatively large electron density (∼1011 cm-3) is derived for the PL1 prominence transition region (PTR). In comparison, PL2 is a relatively quiet prominence with bulk flow velocities generally less than ∼3 km s-1.

Different techniques yield greatly different spatial scales for the prominence. The UV spectra show strong variations in intensity and Doppler shift on scales of about 1700km. The combined density and emission measures indicate path lengths of 400 m or less. The optical depth in C IV requires path lengths of 40 km or less. If, as suggested by these analyses, it is assumed that prominence emission is due to a number of micro-structures with a Gaussian velocity distribution, then spatial scales of the micro-structures of a few hundred kilometers are found. Title: Common Evolution of Adjacent Sunspot Groups Authors: van Driel-Gesztelyi, L.; Csepura, G.; Nagy, I.; Gerlei, O.; Schmieder, B.; Rayrole, J.; Demoulin, P. Bibcode: 1993SoPh..145...77V Altcode: The evolution of two adjacent bipolar sunspot groups is studied using Debrecen full-disc, white-light photoheliograms and Hα filtergrams as well as Meudon magnetograms. The proper motions of the principal preceding spots of both groups show quite similar patterns; the spots move along almost parallel tracks and change the direction of their motion on the same day at almost the same heliographic longitude. Also, three simultaneous emergences of magnetic flux were observed in both groups. These observations support the idea that these adjacent sunspot groups were magnetically linked below the photosphere. Matching the extrapolated magnetic field lines with the chromospheric fibril structure appears to be different in the two groups since they indicate quite different model solutions for each group, i.e., a near-potential magnetic field configuration in the older group (1) and a twisted force-free field configuration in the younger group (2). The latter configuration could be created by a considerable twist of the main bunch of flux tubes in Group 2, which is reflected in the relative sunspot motions. It is also showed how this twist contributed to the formation of a filament between the two groups. Title: Evidence for magnetic reconnection in solar flares Authors: Demoulin, P.; van Driel-Gesztelyi, L.; Schmieder, B.; Hemoux, J. C.; Csepura, G.; Hagyard, M. J. Bibcode: 1993A&A...271..292D Altcode: From a study of the magnetic field topology in an active region, evidence is derived that solar flares are produced by magnetic reconnection. We study a complex group with two active regions (AR 25 t 1 and AR 2512) for three consecutive days, June 13-15 1980. The observed longitudinal magnetic field is used to model the coronal magnetic field by the potential field created by a series of magnetic charges. This computed field matches satisfactorily the Ho fibrils and the observed transverse field direction. A set of flares occurs principally in the northern group (AR 2511). During these three days, two different magnetic configurations in succession are responsible for the occurrence of these flares: first the intrusion of a new opposite flux in the following polarity, secondly the emergence of new flux between the main polarities. In this last case flares occurred, although the emerging bipole is almost parallel to the main bipole. We show that even in this bipolar configuration a separator is present and that observed H flare ribbons are located near the intersection of the computed separatrices with the photosphere. This provides strong support to a model where reconnection releases the stored magnetic energy. The induced evolution of the magnetic field forces reconnection along others separators. They are connected by magnetic field lines to fainter kernels. Title: The fine structure of a chromospheric rosette Authors: Tsiropoula, G.; Alissandrakis, C. E.; Schmieder, B. Bibcode: 1993A&A...271..574T Altcode: We have studied the spatial behaviour of the physical properties of dark mottles forming a well-defined rosette. The observations were obtained with the Multichannel Subtractive Double Pass (MSDP) spectrograph, operating in Hα at the Pic du Midi Observatory. From these observations, intensity fluctuations and Doppler shift velocities at different wavelengths were derived over a two dimensional field of view. The observed contrast profiles were matched with theoretical contrast profiles using Beckers' cloud model and 4 parameters were derived for the dark mottles: the source function, the line-of-sight velocity, the Doppler width and the optical depth. From these parameters a range for the temperature and electron density can be derived using Vernazza's et al. (1981) model D. We detected strong downflows at the roots of the mottles, while their upper part is ascending with velocities sometimes greater than 10 km s-1. The values of the cloud parameters are consistent with values given by other authors for this kind of features. Consistency was also found between cloud parameters and the values given for spicules, leading to the conclusion for the identity of these structures. Title: Active Region Evolution Through Coordinated Observations Authors: Mein, N.; Mein, P.; Schmieder, B.; Engvold, O.; Molowny, R.; Ai, G. X. Bibcode: 1993ASPC...46...63M Altcode: 1993mvfs.conf...63M; 1993IAUCo.141...63M No abstract at ADS Title: Underneath coronal loops: MSDP observations coordinated with SERTS 4 and NIXT flights. Authors: Schmieder, B.; Mein, N.; Golub, L.; Davila, J. M.; Thomas, R.; Brosius, J. Bibcode: 1992ESASP.348..257S Altcode: 1992cscl.work..257S Ground-based coordinated observations with the multichannel subtractive double pass spectrograph (MSDP) allowed to portray the chromospheric intensity and velocity fields below coronal structures during recent launchs of sounding rockets. During SERTS 4 observations (May 7, 1991), two different active regions presenting flare and filament have been coaligned with UV structures. In July 11, 1991 (eclipse day) large Hα ejection material in AR 6713 was detected during the NIXT flight. Preliminary results are displayed. Title: Intensity, velocity and turbulence in prominences observed with the HRTS instrument. Authors: Schmieder, B.; Wiik, J. E.; Dere, K. P. Bibcode: 1992JAF....43...36S Altcode: No abstract at ADS Title: Structural Elements of Filaments Authors: Schmieder, B. Bibcode: 1992SoPh..141..275S Altcode: Filaments are cool structures (∼ 7000 K) embedded in the hot corona. Observations in the optical wavelength range (Hα, Hβ, Ca II K) show that filaments consist principally of a main body with the footpoints tied in the photosphere, generally at the boundaries of the supergranules. New instrumentation (Big Bear, Sacramento Peak, Canary Islands) reveals that filaments are highly structured. The dimension of the fine structures is limited by the spatial resolving power of the instruments (∼ 350 km). These fine structures may be caused by filamentation along the magnetic field or by a radiative instability during the formation of the prominences. New attempts based on radiative transfer calculations, density diagnostics, or dynamics are being developed in order to estimate the number of threads integrated along the line of sight, 2 to 200 according to various authors. Plasma parameter values are derived from these studies. While the models of prominences take into account the magnetic field observations, the fine structures and the dynamics are ignored most of the time. Title: Determination of plasma parameters in a quiescent prominence Authors: Wiik, J. E.; Heinzel, P.; Schmieder, B. Bibcode: 1992A&A...260..419W Altcode: We present H-alpha observations and analysis of a quiescent, polar crown prominence observed on June 11, 1988 with the MSDP spectrograph at the Pic du Midi Observatory. Two-dimensional maps of H-alpha intensities and line-of-sight velocities have been obtained. The large-scale velocity pattern consisting of cells and elongated structures is stable on a time scale of about 1 min, but evolves continuously and undergoes large changes in shape and amplitude during one hour. This behavior of the velocity field suggests the presence of twists in flux ropes or shear motions. Further, comparing the absolute observed intensities with values from non-LTE radiative computations we estimate the range of electron densities, source functions and optical thicknesses in different parts of the prominence. For upper parts of the prominence we obtain electron densities in the range 1 - 5 x l0 exp 10/cu cm. Title: Time evolution of a two-ribbon flare - Characteristics of post-flare loops Authors: Gu, Xiao-Ma; Lin, Jun; Luan, Ti; Schmieder, B. Bibcode: 1992A&A...259..649G Altcode: Observations of a two ribbon flare on 5 May, 1989 were performed at Yunnan Observatory and at Meudon. Magnetograms have been obtained in Huairou-Beijing Observatory. The topology of the flaring region and the slow evolution of post-flare loops (cool flare loops) can be derived from Yunnan filtergrams. The ribbons seem to be the footpoints of the loops. The analysis of H-alpha line profiles in the loops, obtained with the Multichannel Subtractive Double Pass (MSDP) spectrograph of Meudon allows us to derive some physical parameters of the loops. The importance of the reference background intensity is discussed. The cool flare loops are low (hmax is approximately equal to 25,000 km) dense (ne is approximately equal to 10 exp 11/cu cm) and relatively inhomogeneous. They are rising with a velocity of 5 to 10 km/s. Title: Intensity, velocity and turbulence in prominences observed with the HRTS. Authors: Wiik, J. E.; Dere, K.; Schmieder, B. Bibcode: 1992ESASP.344...65W Altcode: 1992spai.rept...65W The moments of UV emission line profiles between 1206 and 1670 A observed in two quiescent prominences with the High Resolution Telescope and Spectrograph (HRTS) are analysed. Spectral lines in this region of the solar spectrum provide information on plasmas in the 10000K to 200000K range. In both prominences a good correlation is found between the intensities of lines formed at different temperatures. A good correlation is also found between the non-thermal velocities of different lines. Title: Structure and Dynamics of Cool Flare Loops Authors: Heinzel, P.; Schmieder, B.; Mein, P. Bibcode: 1992SoPh..139...81H Altcode: MSDP observations of the 16 May, 1981 two-ribbon flare are used to study the physical structure and the dynamical behaviour of cool flare loops. The loops have been detected in the Hα line just after the flare maximum and they appeared in absorption against the disk. Using the first-order differential cloud model (DCM1) technique, we derive empirically some basic plasma parameters at 15 points along one loop leg. The flow velocities and the true heights have been reconstructed with respect to a geometrical projection. Subsequently, detailed non-LTE models of cool loops have been constructed in order to fit Hα source function values previously derived from DCM1 analysis. It is demonstrated that this source function is rather sensitive to the radial component of the flow velocity (the so-called Doppler brightening) and to enhanced irradiation of the loops from the underlying flare ribbons. In this way, we have been able to estimate quantitatively all plasma parameters which determine the physical structure of cool loops (i.e., the temperature, pressure, density), as well as the momentum-balance condition within the loops. For these dark loops we have arrived at relatively low gas pressures of the order of 0.1-0.5 dyne cm-2 with corresponding electron densities around 1011 cm-3. Pressure-gradient forces have been found to be of small importance in the momentum-balance equation, and thus they cannot explain departures from a free-fall motion found in our MSDP data analysis. We propose three possible solutions to this problem. Title: Chromospheric structure and dynamics. Authors: Schmieder, B. Bibcode: 1992ESASP.344...35S Altcode: 1992spai.rept...35S Chromospheric structures are observed up to the limiting spatial resolving power of the instruments. The magnetic field controls the chromospheric topology both at the large scale, such as canopies, supergranulation, mesogranulation and at the small scale, such as fibrils, mottles, spicules. Different properties of the chromosphere structure may be deduced from a dynamics study. The author will discuss on the role of magnetic and convective forces in oscillatory and non-stationary flows observed in the structures. Spectroscopic diagnostics are used to derive physical parameters in chromospheric structures. Title: Post-Flare Loops Authors: Schmieder, B. Bibcode: 1992LNP...399..124S Altcode: 1992IAUCo.133..124S; 1992esf..coll..124S Post-flare loops or cool flare loops (CFL) when observed in the H line are magnetic structures within an active region which are clearly a fundamental part of the flare itself and not an external phenomenon or a consequence of flares. After a two-ribbon flare the field-line reconnection gives rise to flare loops of hot temperature which shrink and become cool within few minutes to an hour. The Ha flare loops appear generally as dark loops during the gradual phase of the flare; viewed on the limb they may appear as loops in emission, reaching 50000 km. They create a system of quasi-steady arches lasting up to several hours. Large downflows are observed along the legs of the loops with deccelaration by comparing to free-fall motions. As derived from radiative transfer diagnostics, the gas pressure range of the loops is between 0.2 and 5 dyn cm-2 and the electron density is between 1010 and 1012 cm-3. The magnetic free energy needs to be continuously replenished from low levels during the flare. Different mechanisms may be considered, dynamical ones such as upward motion from the convection zone pushing the coronal field and twisting of the field lines, or thermal ones such as evaporation or ablation of chromospheric material. We will discuss some observational evidence supporting the Forbes and Malherbe (1986) reconnection model based on the Kopp and Pneuman configuration. Title: Fine structure analysis of a prominence in H-alpha and coronal lines Authors: Wiik, J. E.; Schmieder, B.; Noens, J. C.; Heinzel, P. Bibcode: 1992sws..coll..131W Altcode: Prominence observations made simultaneously with the MSDP spectrograph and with the coronagraph at Pic du Midi are presented. The existence of a coronal cavity is discussed. 2D maps of H-alpha intensities and the line-of-sight velocities have been obtained. The behavior of the velocity field suggests the presence of twists along flux ropes or shear motions. Further, using a probabilistic approach to the H-alpha-line formation, we estimate the range of temperatures, electron densities and optical thicknesses in different parts of the prominence by fitting the observed H-alpha intensity profiles. Title: Plasma Parameters Derived from MSDP Observations of Cool Flare Loops Authors: Heinzel, P.; Schmieder, B.; Mein, P. Bibcode: 1992LNP...399..134H Altcode: 1992IAUCo.133..134H; 1992esf..coll..134H MSDP observations of 16 May 1981 two-ribbon flare are used to study the physical structure and dynamical behaviour of cool flare loops. The loops have been detected in the H line just after the flare maximum and they appeared in absorption against the disk. Using the first-order differential cloud model (DCM1) technique, we derive empirically some basic plasma parameters at 15 points along one loop leg. The flow velocities and true heights have been reconstructed with respect to a geometrical projection. Subsequently, detailed non-LTE models of cool loops have been constructed in order to fit H source-function values previously derived from DCM1 analysis. It is demonstrated that this source function is rather sensitive to the radial component of the flow velocity (the so-called Doppler brightening) and to the enhanced irradiation of the loops from the underlying flare ribbons. In this way, we have been able to estimate quantitatively all plasma parameters which determine the physical structure of cool loops (i. e. the temperature, pressure, density, etc.), as well as the momentum-balance condition within the loops. For these dark loops we have arrived at relatively low gas pressures of the order of 0.1 - 0.5 dyn cm-2 , with corresponding electron densities around 1011 cm-3. Pressure-gradient forces have been found to be of small importance in the momentum-balance equation. However, the classical momentum equation is not capable of explaining significant departures from a free-fall motion under the gravity force, found from our MSDP data. We propose three possible explanations to this problem. Title: Dynamics in the Prominence - Corona Transition Region from HRTS Spectra Authors: Schmieder, B.; Dere, K. P.; Wiik, J. E. Bibcode: 1992LNP...399..333S Altcode: 1992esf..coll..333S; 1992IAUCo.133..333S Line profiles of UV emission lines between 1206Å and 1670Å observed in two prominences with the High Resolution Telescope and Spectrograph (HRTS) are analysed. Spectral lines in this region of the solar spectrum such as C I, Fe II, Si IV and C IV, provide information on plasmas in the 10 000 K to 200 000 K range. In the active prominence observed with HRTS-1 a good correlation is found between the intensities and velocities of different lines formed over a range of temperatures. On the contrary, poor cross correlation between the velocities observed in plasmas of cold temperatures indicates the presence of different structures in the SL2 prominence. Microturbulent velocities from 0 to 25km s-1 are found in both prominences. Title: Fine structure of solar filaments. II - Dynamics of threads and footpoints Authors: Schmieder, B.; Raadu, M. A.; Wiik, J. E. Bibcode: 1991A&A...252..353S Altcode: The dynamical behavior of the fine structures observed at the Pic du Midi through a multichannel subtractive double pass (MSDP) spectrograph during a 15-min period has been studied. Widespread continual changes in the velocity field were observed during this period, and, for the whole region, there was virtually no correlation from one minute to the next. High velocities (up to +/-15 km/s) were detected at locations where the filament was anchored in the chromosphere using the first order differential cloud model. It is argued that these footpoints are essentially the same kind of structures as the chromospheric bushes seen around supergranules, which show spiculelike activity modified by the local magnetic field geomentry. Parallel to the filament axis elongated Doppler structures with coherent motions were observed. These structures may be interpreted as magnetic flux tubes identifiable during their short rise time, or they may indicate that there are coherent wave motions. Title: A microflare-related activation of a filament observed in H-alpha and C IV lines Authors: Schmieder, B.; Fontenla, J.; Tandberg-Hanssen, E. Bibcode: 1991A&A...252..343S Altcode: A filament in active region AR 2717 was observed in two lines formed at different temperatures (H-alpha at 10 exp 4 K and C IV at 10 exp 5 K) with the multichannel-double-pass (MSDP) spectrograph and the ultraviolet spectrometer and polarimeter (UVSP). The partial disparition brusque (DB) of the filament as observed in H-alpha was due to the heating of a filament section in the vicinity of a bright point. A propagating disturbance followed this event. A detailed analysis of C IV rasters shows that this disturbance was not a passive perturbation, but was itself triggering active phenomena at various locations along its path, resulting in energy releases. It is suggested that this propagation of brightness was due to fast successive reconnections between fine looplike structures of the filament. Title: Conditions for flare and filament formation in interacting solar active regions Authors: Schmieder, B.; Henoux, J. -C.; van Driel-Gesztelyi, L.; Simnett, G. M. Bibcode: 1991A&A...244..533S Altcode: The evolution of two interacting sunspot groups of different ages is traced over a period of three days. The photospheric velocity field is obtained and compared with the general evolution of the region in an attempt to better understand the conditions that lead to flare activity and filament formation. It is shown that the observed photospheric motions can generate dc electric currents, which, in effect, could lead to energy storage. Title: Comparison of SERTS Spectroheliograms with Ground-Based Observations Authors: Thompson, W. T.; Neupert, W. M.; Brosius, J. W.; Jones, H. P.; Schmieder, B. Bibcode: 1991BAAS...23R1061T Altcode: No abstract at ADS Title: Oscillations in Hα filaments: center-to-limb study. Authors: Thompson, W. T.; Schmieder, B. Bibcode: 1991A&A...243..501T Altcode: Center-to-limb observations of time sequences of the velocity field in filaments have been made with the MSDP spectrograph operating on the Meudon solar tower. The velocity power spectra made over whole filament regions show a broad maximum around 200 s period. The power in the filaments is reduced compared with the chromosphere power near the disk center by a factor of 2-4, while at μ = 0.9 they are more comparable. Nevertheless, the MSDP spectrograph allows a 2D analysis and the authors find that high oscillation amplitudes (1-1.25 km s-1) are detected in discrete areas, principally at the edges of the filaments and in chromospheric fibrils close to the filament, with well defined periods around 250 s, 200 s, and 150 s. The oscillations are transverse to the direction of the fine structures. A wave propagation velocity along the fibrils has been derived from the observations and could correspond to an Alfvén velocity. The authors discuss mechanisms that may be responsible for these waves. The oscillations could be interpreted by eigenmodes of filamentary structures. A resonance phenomenon may occur between surface waves generated at the boundary of the tubes and body waves (i.e. Alfvén waves). Title: Flares and filament formation due to the interaction between two active regions Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Hénoux, J. C.; Simnett, G. Bibcode: 1991AdSpR..11e..95S Altcode: 1991AdSpR..11...95S We follow the evolution (flare activity, filament formation) of two interacting active regions of different ages over three days, through observations at white-light, Hα, UV, and X-ray wavelengths. We show that the observed photospheric motions could generate DC electric currents and that they could lead to free energy storage. Flares were observed more-or-less simultaneously in remote locations of the sunspot group. This suggests that the same perturbation affected an ensemble of lines of force. Filament formation took place due to DC current generation by photospheric shearing motions with a velocity up to 350 m s-1. Title: Coordinated observations with high resolution spectrographs (HRTS, SERTS, MSDP) Authors: Schmieder, B.; Thompson, W. T.; Neupert, W. M.; Thomas, R. J.; Dere, K. P. Bibcode: 1991AdSpR..11e.255S Altcode: 1991AdSpR..11R.255S Observations with the High Resolution Telescope Spectrograph (HRTS) aboard Spacelab2 in 1985, and more recently with the Solar Extreme-ultraviolet Rocket Telescope and Spectrometer (SERTS) during the rocket flight of May 5, 1989 were well coordinated with the Meudon instruments, principally with the Multichannel Subtractive Double Pass (MSDP) spectrograph. These instruments allow the study of phenomena in a large temperature range and the determination of the energy budget. MSDP observations coordinated with the SERTS have permitted the analysis of physical parameters of coronal plasma surrounding dynamical chromospheric events, such as preflaring region and a filament. By combining Hα spectrograms and HRTS data, C IV flow (~50 km s-1) detected at the footpoints of a prominence has been interpreted by horizontal velocities along the axis of the arches of the prominence. Title: Oscillations detected in C IV and Hα lines in magnetic structures Authors: Schmieder, B.; Thompson, W. T.; Mein, P. Bibcode: 1991AdSpR..11d.195S Altcode: 1991AdSpR..11..195S Different processes involving the magnetic field and its fine structures in the atmosphere have been proposed to explain the heating of the corona. To help explore phenomena related to these different processes, we will report some new observations of oscillations in fine chromospheric structures using the MSDP spectrograph operating at Meudon and the UVSP spectrograph aboard SMM. The temporal analysis of radial velocities measured in the C IV line shows that no oscillations are detectable in the transition zone. It is in good agreement with the wave reflection model generally admitted. In the Hα line the 2 D analysis points out that the energy observed in an unresolved frequency range around 250 s in the chromospheric power spectrum is in fact concentrated in structures parallel to chromospheric fibrils along which the phase extends coherently. The oscillations appear to be transverse and might be interpreted either by Alfvén waves generated in the chromosphere and propagating through magnetic filamentary structures or by eigenmodes of filamentary structures excited by chromospheric p-modes. Title: Flow patterns in a sunspot region observed in the photosphere, chromosphere and transition region Authors: Dere, K. P.; Schmieder, B.; Alissandrakis, C. E. Bibcode: 1990A&A...233..207D Altcode: The flow patterns around a sunspot at photospheric, chromospheric, and transition zone temperatures is examined. The spiral fibril pattern observed in H-alpha is consistent with a constant alpha force-free field extrapolation of the photospheric magnetic field. Evidence is found for the first time that C IV fibrils near spots follow the field lines parallel to the chromospheric H-alpha fibrils. The observed large-scale pattern of redshifts and blueshifts in the vicinity of the sunspot is stable and conforms to the typical Evershed flow patterns of radial outflow at the photospheric levels and radial inflows at the chromospheric and transition region levels. The three-dimensional velocity vectors associated with this flow are derived assuming an axially symmetric Evershed flow. Title: Evaporation in the Transition Region during the Gradual Phase of Flares Authors: Schmieder, B.; Malherbe, J. M.; Simnett, G. M.; Forbes, T. G.; Tandberg-Hanssen, E. Bibcode: 1990ApJ...356..720S Altcode: Previous observations have revealed that small, but sustained, H-alpha blueshifts occur in flare ribbons during the gradual, or late, phase of flares. These blueshifts suggest that there is a gentle evaporation of chromospheric material throughout the late phase of flares, but ambiguities in the interpretation of H-alpha leave open the possibility that these blueshifts are caused by downflowing, rather than upflowing, material. Using both C IV and soft (3.5-8 keV) X-ray data from SMM observations, evidence is found which supports the interpretation of the H-alpha blueshifts as upflows in the range from 4-12 km/s. The blueshifts are interpreted in terms of the reconnection model proposed by Carmichael (1964). The model produces a sustained energy release through-out the late phase which accounts for the prolonged soft X-ray emission after a flare. This energy release comes from the reconnecting magnetic field above the flare site, and some of the energy is transported along field lines mapping to the chromosphere where it drives chromospheric evaporation. Title: Ultraviolet Spectra of a Prominence Authors: Dere, K.; Lund, P.; Schmieder, B. Bibcode: 1990BAAS...22R.815D Altcode: No abstract at ADS Title: Relationship between a spot and a filament observed during spacelab 2 mission Authors: Schmieder, B.; Dere, K. P.; Raadu, M. A.; Démoulin, P.; Alissandrakis, C. E. Bibcode: 1990AdSpR..10i.195S Altcode: 1990AdSpR..10..195S During the Spacelab 2 Mission, an active region including a sunspot, plages, fibrils and a filament which disappears during the observation period, was observed in Hα and in the C IV lines. The analysis of the observations leads to several conclusions. Shear in the active region filament is observed before its disappearance. Hα and C IV upflows in the filament are well correlated spatially, but the transition zone (C IV) velocities are an order of magnitude larger than the Hα chromospheric ones. Over the sunspot, the reverse-Evershed effect is observed in Hα and in C IV Dopplershift images while strong downflows are also detected in the C IV profiles.

Magnetograph data for the whole region are used to calculate the linear force-free magnetic field. A single value of the force-free parameter α is found to give a good fit to both the sheared filament structure and the sunspot spiral structures, indicating a causal relationship.

We propose a model based on the inductive coupling between current systems associated with the filament and the sunspot. Relaxation phenomena due to resistive effects in the filament could lead to irreversible conversion of magnetic energy into kinetic energy and heating. Title: Oscillations detected in Hα filaments. Authors: Schmieder, B.; Thompson, W. T.; Mein, P. Bibcode: 1990PDHO....7..296S Altcode: The authors report some new observations of oscillations in filaments observed at different positions on the disk using the MSDP spectrograph operating at Meudon. The velocity power spectra made over whole filament regions show a smooth maximum around 200 s period. Oscillations are detected principally in discrete areas in the filaments and in chromospheric fibrils, with well defined periods around 250 s and 150 s. The oscillations could be interpreted by Alfvén waves generated in the chromosphere and propagating through magnetic filamentary structures or by eigenmodes of filamentary structures excited by chromospheric p-modes. Title: Dynamical Structure of a Quiescent Prominence Authors: Mein, P.; Mein, N.; Schmieder, B.; Noëns, J. C. Bibcode: 1990LNP...363..252M Altcode: 1990doqp.coll..252M; 1990IAUCo.117..252M A statistic analysis of H profiles in a quiescent prominence is consistent with the superposition of individual velocity structures (typically 10), with standard deviation ~ 15 km s-1. Title: Hα diagnostics of 16 May 1981 flare loops. Authors: Heinzel, P.; Mein, P.; Schmieder, B. Bibcode: 1990PDHO....7..272H Altcode: MSDP observations (Meudon) of 16 May 1981 post-flare loops are used to derive the hydrogen plasma parameters in flare loops. The authors compare two recently developed methods: a differential cloud model and a probabilistic transfer technique. Title: Interaction between Bipolar Sunspot Groups Authors: Csepura, G.; van Driel-Gesztelyi, L.; Nagy, I.; Gerlei, O.; Schmieder, B.; Rayrole, J. Bibcode: 1990PDHO....7...88C Altcode: 1990ESPM....6...88C; 1990dysu.conf...88C The authors find some evidence for the interaction of two close-by developing sunspot groups. Title: Formation of a Filament around a Magnetic Region Authors: Schmieder, B.; Démoulin, P.; Ferreira, J.; Alissandrakis, C. E. Bibcode: 1990LNP...363..232S Altcode: 1990doqp.coll..232S; 1990IAUCo.117..232S The evolution of the active region AR4682 observed in 1985 during six rotations was dominated by three different phenomena: . the large scale pattern activity: relationship between two active regions, formation of a quiescent filament during the decay phase of the active region, . the presence of two pivot points along the filament surrounding the sunspot-with the long term one is associated the existence of the filament, with the short term one the activity with partial disappearance, . the magnetic shear during one rotation. The magnetic field lines have been extrapolated from photospheric data using Alissandrakis code (1981). The magnetic configuration with the existence of a dip favors the formation of a filament. We note that the shearing of the sunspot region and of the filament are both well described by force-free magnetic fields with the same constant α. This suggests that they are both a consequent of the same shear process. Title: High Resolution Spectrography in Ultraviolet Authors: Schmieder, B.; Thompson, W. T.; Neupert, W. M.; Thomas, R. J.; Dere, K. P. Bibcode: 1990PDHO....7..250S Altcode: 1990ESPM....6..250S; 1990dysu.conf..250S The authors point out some of the advantages of coordinated observations with ground-based and space instrumentation. Results obtained during the rocket flight of the Solar Extreme-ultraviolet Rocket Telescope and Spectrograph (SERTS) for a preflaring region are presented and the complementarity of observations is pointed out with the High Resolution Telescope and Spectrograph (HRTS) which permits the detection of dynamical structures in hot plasma surrounding cool structures such as prominences and sunspots seen in visible light. Title: Mass Motion in and around Prominences Authors: Schmieder, B. Bibcode: 1990LNP...363...85S Altcode: 1990IAUCo.117...85S; 1990doqp.coll...85S The mass of a quiescent prominence is equivalent to one-tenth of the all coronal plasma. It is obvious that this crucial problem is resolved, now if we consider the dynamical nature of prominences. Observations of motions of filaments will be reviewed in regard to their time scales: . solar cycle (slow migration of filaments, pivot points, convection) . days or hours (stationary motions, oscillations) . hours or minutes (appearance or disparition brusque, eruption) These motions will be discussed in view of a better understanding of the formation of filaments (chromospheric injection or coronal plasma condensation), stability of the fine structures, existence of the feet, relationship of the DB, and the coronal mass ejections. Title: Evolution of Fine Structures in a Filament Authors: Schmieder, B.; Mein, P. Bibcode: 1990LNP...363..235S Altcode: 1990doqp.coll..235S; 1990IAUCo.117..235S A quiescent filament observed in June 1986 underwent a slow Disparition Brusque which lasted 4 days. Here, we focus our study on the dynamical behaviour of the fine structures ( Full-Width Half-Max ~ 350 km) in this filament which were observed at Pic du Midi with the Multi-Channel Subtractive Double Pass (MSDP) spectrograph during a period of 30 minutes. We observed no changes in intensity during this period, but we did observe changes in the velocity field with no correlation from one minute to the next. High velocities were detected at the footpoints where the filament is anchored in the photosphere , of the same order than those observed at the boundaries of the supergranules (between ±10 km s-1). To explain these observations we suggest a spicule-like model which supplies material to the prominence. Title: Overall properties and steady flows Authors: Schmieder, B. Bibcode: 1989ASSL..150...15S Altcode: 1988dsqs.work...15S; 1989dsqs.work...15S Since the publication of the book 'Solar Prominences' (Tandberg-Hanssen, 1974), prominences have been the subject of many theoretical and observational studies, as discussed and summarized in several reviews (Hirayama, 1985; Poland, 1986; Malherbe, 1987). The present paper presents recent progress, mostly from an observational point of view, in the understanding of the formation, structure, support, and instabilities of solar prominences. Results of spectroscopic diagnostics (velocity, temperature and density) are stressed. Title: Evolution of Fine Structures in a Filament Authors: Schmieder, B.; Mein, P. Bibcode: 1989HvaOB..13...31S Altcode: No abstract at ADS Title: Flare Dynamics Authors: Zarro, D.; Alexander, D.; Fludra, A.; Emslie, G.; Gurman, J.; Graeter, M.; Li, P.; Phillips, K.; Saba, J.; Schmieder, B.; Slater, G.; Wulser, J. P.; Watanabe, T.; Dulk, G.; MacKinnon, A.; McClements, K.; Spicer, D. Bibcode: 1989tnti.conf....2Z Altcode: No abstract at ADS Title: A surge in the chromosphere and the transition region: velocities and microturbulence. Authors: Mein, P.; Schmieder, B.; Tandberg-Hanssen, E. Bibcode: 1989sasf.confP.223M Altcode: 1989IAUCo.104P.223M; 1988sasf.conf..223M Simultaneous observations of a surge in Hα and C IV are analysed in terms of Doppler velocities and "microturbulence". The behaviour of both quantities suggests strong velocity shears with small spatial scales. Title: Dynamical Structure of a Quiescent Prominence Authors: Mein, P.; Mein, N.; Schmieder, B.; Noens, J. C. Bibcode: 1989HvaOB..13..113M Altcode: No abstract at ADS Title: Preflare activity. Authors: Priest, E. R.; Gaizauskas, V.; Hagyard, M. J.; Schmahl, E. J.; Webb, D. F.; Cargill, P.; Forbes, T. G.; Hood, A. W.; Steinolfson, R. S.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M. -J.; Porter, J. G.; Schmieder, B.; Smith, J. B., Jr.; Toomre, J.; Woodgate, B.; Waggett, P.; Bentley, R.; Hurford, G.; Schadee, A.; Schrijver, J.; Harrison, R.; Martens, P. Bibcode: 1989epos.conf....1P Altcode: Contents: 1. Introduction. 2. Magnetohydrodynamic instability. 3. Preflare magnetic and velocity fields. 4. Coronal manifestations of preflare activity. Title: Formation of a Filament around a Magnetic Region Authors: Schmieder, B.; Demoulin, P.; Ferreira, J.; Alissandrakis, C. E. Bibcode: 1989HvaOB..13....1S Altcode: No abstract at ADS Title: An example of the association of X-ray and UV emission with H-alpha surges Authors: Schmieder, B.; Mein, P.; Simnett, G. M.; Tandberg-Hanssen, E. Bibcode: 1988A&A...201..327S Altcode: From H-alpha UV, and X-ray data, the nature of a well-observed surge on November 12, 1980 has been studied to try to understand the relationships between the mechanical motions and the high-temperature emissions. The cool (H-alpha) and the hot (O v) parts of the surge plasma both show velocities in the range of 100-120 km/s. The kinetic and potential energies of the surge are two orders of magnitude higher than the radiative energy. The observations suggest that the surge occurs in open structures parallel to one leg of a large scale coronal magnetic loop. The energy is released principally in the open structure (surge) and only a small amount heats the coronal loop (X-ray signature). This energy division should probably not be treated as a general characteristic of surge events. Different events are expected to exhibit a different energy balance, and this can account for the lack of a consensus in the previous literature regarding surge/X-ray associations. Title: The Evershed flow in the solar photosphere, chromosphere and chromosphere-corona transition region Authors: Alissandrakis, C. E.; Dialetis, D.; Mein, P.; Schmieder, B.; Simon, G. Bibcode: 1988A&A...201..339A Altcode: The authors have studied the height dependence of the characteristics of the Evershed flow in the photosphere, chromosphere and chromosphere-corona transition region. The Multichannel Subtractive Double Pass Spectrograph was used to obtain line of sight velocity maps in Hα, the Meudon magnetograph for mapping the photospheric velocity and magnetic field and the Ultraviolet Spectrometer and Polarimeter on the Solar Maximum Mission spacecraft for line-of-sight velocities in C IV, in sunspot regions. The observations are practically simultaneous in the three atmospheric levels and cover three consecutive days (Sep 28, 29 and 30, 1980). The emphasis was on the large scale, quasi-stationary characteristics of the flow. Title: Photospheric-induced destabilization and ejection of prominence material Authors: Raadu, M. A.; Schmieder, B.; Mein, N.; Gesztelyi, L. Bibcode: 1988A&A...197..289R Altcode: The sequence of events leading up to prominence activation in two different cases is studied. In one case, observed on September 3, 1980, strong velocity shears were produced indicating filament twisting. In the other case, observed on June 22, 1980, activation results in the ejection of prominence material. The paper presents new evidence for a common initial triggering mechanism, the birth or motion of pores at one end of the activated filament sections. This is taken as an indication of emerging magnetic flux and current induction in the filaments. The difference in the final results is partly due to the different ambient magnetic field structures. In particular in the case leading to material ejection there is a subsequent associated flare occurred indicating the storage of magnetic energy in the region. Models are proposed for the two sequences of events, clarifying the underlying similarities and interpreting the distinct features of the two sets of observations. Title: Some dynamical aspects of a quiescent filament Authors: Schmieder, B.; Demoulin, P.; Poland, A.; Thompson, B. Bibcode: 1988A&A...197..281S Altcode: A typical quiescent filament was observed on the disk in the Hα and C IV lines during a period of approximately one hour. Vertical velocities (<2.5 km s-1) with a time scale of 5 min and a spatial scale of a few tens of seconds of arc were detected in Hα, and associated with microturbulence in both lines. The C IV observations correlated well with those in Hα, and showed no indication of material heating from Hα to C IV temperatures. Two mechanisms to explain these observations are proposed: mass motion along twisted magnetic field or instabilities triggering waves along the filament. Title: Variations of the Solar Limb Brightness with the Oscillations Authors: Schmieder, B.; Mein, P. Bibcode: 1988IAUS..123..429S Altcode: The aim of this work is to compute the amplitude of the limb darkening fluctuations due to oscillations in order to compare it with the observations made with the heliometer at the Pic du Midi (Rösch and Yerle 1983 - 1984). It is shown that 5 min oscillations lead to variation in the brightness gradient of less than 2%. Title: Environment and dynamics of a prominence observed at Pic du Midi. Authors: Noëns, J. C.; Schmieder, B.; Mein, P. Bibcode: 1988dssp.conf..177N Altcode: Simultaneous observations were made at Pic du Midi using the 20 cm Coronograph and the Multichannel Subtractive Double Pass spectrograph operating in the "Coupole Tourelle". The prominence observed on June 17, 1987 is composed of three principal vertical structures 50000 km high with faint material connecting then. A coronal cavity is visible above the prominence. The dynamics of this prominence in Hα is large, horizontal circulation is observed. Images in Hα versus time show a slow evolution in the general shape with an exchange of material between the vertical structures. Title: Velocity shear and microturbulence in solar filaments a differential cloud model. Authors: Mein, P.; Schmieder, B. Bibcode: 1988dssp.conf...17M Altcode: The authors analyse the time sequence of an active region filament observed at the MSDP of the Meudon Solar Tower. They use a "differential cloud model" which is well suited to the interpretation of Hα profiles with an inhomogeneous chromospheric background. A previous model (Schmieder et al. 1985) suggesting twisting motions of magnetic ropes is confirmed. Title: Overall properties and steady flows. Authors: Schmieder, B. Bibcode: 1988dssp.conf....5S Altcode: A description and a classification of some of the different types of prominences observed is presented. The importance of filaments as tracers of the general magnetic field is indicated. From the spectroscopic diagnostics, density, temperature, microturbulence and velocity are deduced under, in and around filmants using photospheric, chromospheric and EUV lines. Activation of filaments is due to instabilities. The causes and the consequences of these instabilities are reviewed. Title: The Role of the Observatoire de Paris, Meudon in Providing Astronomical Information Authors: Floquet, M.; Schmieder, B. Bibcode: 1988scaa.conf..224F Altcode: 1988IAUCo..98..224F No abstract at ADS Title: Post-flare loops: formation and velocity Authors: Schmieder, B.; Mein, P.; Malherbe, J. -M.; Forbes, T. G. Bibcode: 1988AdSpR...8k.145S Altcode: 1988AdSpR...8..145S Post-flare loops are generally observed between two ribbon flares. The formation of post flare loops and active region or plage filaments has been explained in a model based on magnetic reconnection and chromospheric ablation /1,2/. This model uses a magnetic topology which is relevant to solar flares /3/ : a large flare or an instability opens the magnetic lines of a coronal arcade (or arch) and a vertical current sheet forms. Then the reconnection of the magnetic field follows according to the scenario of Kopp and Pneuman /4/. In this magnetic configuration, we show that the formation of condensations or dense loops is induced by reconnection shocks.

We give in this communication a new method of diagnostic to derive from Hα profiles physical parameters, i.e. source function, optical depth and velocity. This method called ``differential cloud method'' is very promising for future observations. Title: Chromospheric and Transition Zone Flows in a Solar Active Region Authors: Dere, K. P.; Schmieder, B. Bibcode: 1987BAAS...19.1118D Altcode: No abstract at ADS Title: Closed Magnetic Structures in the Chromosphere and in the Transition Region Authors: Malherbe, J. M.; Schmieder, B.; Simon, G.; Mein, P.; Tandberg-Hanssen, E. Bibcode: 1987SoPh..112..233M Altcode: Using simultaneous observations of the same solar regions in the lines Hα and CIV 1548 Å, we have derived schematic models of closed magnetic lines from dynamical constraints. We conclude that the magnetic loops are closed at higher levels above facular than above non-facular regions. This result remains valid whatever are the assumed density models and even if we take into account the 3 min oscillations. The center-to-limb behaviour is well predicted by taking into account the relative opacity in chromosphere and transition region. Title: Fine structures in solar filaments. I - Observations and thermal stability Authors: Demoulin, P.; Malherbe, J. M.; Schmieder, B.; Raadu, M. A. Bibcode: 1987A&A...183..142D Altcode: Limb observations of quiescent prominences show very fine structures of less than one arcsecond. Here H-alpha observations on the disk, made with the Multichannel Subtractive Double Pass spectrograph operating at the Observatoire du Pic du Midi are presented. They show long fine structures in the body of the filament, both in intensity and velocity maps. Many prominence models ignore such fine structures and suppose that the quiescent filament is a uniform body such as is seen in unresolved images. It has been suggested that in a current-sheet model of a prominence, fine structures may be produced as a consequence of the tearing mode coupled to thermal instability. Here the role of parallel and orthogonal conduction on the stability of a periodic fine structure is investigated. Equilibrium conditions are found and growth rates determined for linear perturbations. Title: Evidence for Gentle Chromospheric Evaporation during the Gradual Phase of Large Solar Flares Authors: Schmieder, B.; Forbes, T. G.; Malherbe, J. M.; Machado, M. E. Bibcode: 1987ApJ...317..956S Altcode: The Multichannel Subtractive Double Pass Spectrograph of the Meudon solar tower is used to obtain high spatial resolution H-alpha line profiles during the gradual phase of three solar flares. In all cases, small blueshifts lasting for several hours are observed in the flare ribbons. By contrast, the region between the two ribbons exhibits large redshifts that are typical of H-alpha post flare loops. The blueshifts in the ribbons is interpreted as upward chromospheric flows of 0.5-10 km/s, and the possible ambiguities of the interpretation are discussed. A preliminary analysis indicates that such upflows are sufficient to supply the greater than 10 to the 16th g of mass needed to maintain a dense H-alpha postflare loop system in the corona. Title: Material Ejecta in a Disturbed Solar Filament Authors: Raadu, M. A.; Malherbe, J. M.; Schmieder, B.; Mein, P. Bibcode: 1987SoPh..109...59R Altcode: Hα observations, using the Multichannel Subtractive Double Pass (MSDP) spectrograph operating on the Meudon Solar Tower, have been made of an active region filament which undergoes a `disparition brusque'. The period of observation was from 10 ∶ 45 to 13 ∶ 30 UT on 22 June, 1981. Velocity and intensity fluctuations in Hα were measured. The proper motions of ejecta were followed allowing their trajectories and vector velocities to be determined. To model the dynamics of ejecta several models using thermal or magnetic driving forces are compared. The most promising model explains the motion as the consequence of magnetic stresses acting on an isolated magnetized plasmoïd in a diverging flux tube. Title: The Evershed flow in the solar photosphere, chromosphere and chromosphere-corona transition region. Authors: Alissandrakis, C. E.; Dialetis, D.; Mein, P.; Schmieder, B.; Simon, G. Bibcode: 1987PAICz..66..147A Altcode: The authors have studied the height dependent characteristics of the Evershed flow in the photosphere, chromosphere and chromosphere-corona transition region. Title: Photospheric Induced Destabilization and Ejection of Prominence Material Authors: Raadu, M. A.; Schmieder, B.; Mein, N.; Gesztelyi, L. Bibcode: 1987HvaOB..11..105R Altcode: The cause of the sudden activation of solar prominences is not clear. The authors present observations of two cases which were preceded by the emergence and motion of pores (new flux) in the near vicinity of the filaments, which seem to be closely related to the process which triggered the filament destabilization. These observations may be well described by a theoretical model in which the new flux interacts with the older "stable" magnetic field. Title: Dynamics of solar filaments. V - Oscillations in the H-alpha and 1548 A C IV lines Authors: Malherbe, J. M.; Schmieder, B.; Mein, P.; Tandberg-Hanssen, E. Bibcode: 1987A&A...172..316M Altcode: Using the Multichannel Subtractive Double Pass Spectrograph operating in the Meudon solar tower and the Ultraviolet Spectrometer and Polarimeter aboard the Solar Maximum Mission satellite, the authors analyze by Fourier transform technique time sequence observations of filaments in both the Hα line and in the 1548 Å C IV line. The Hα data confirm previous findings that there are no oscillations at the location of the filament in the observed range 1 - 10 mHz. In the C IV line the authors observe power in some parts of the filament where a steady velocity gradient is present, e.g. in the footpoints. The energy is probably due to convective motions rather than pressure oscillations. Title: Environment and Dynamics of a Prominence Observed at Pic-Du Authors: Noens, J. C.; Schmieder, B.; Mein, P. Bibcode: 1987dssp.work..177N Altcode: 1987ASSL..150..177N No abstract at ADS Title: Overall Properties and Steady Flows Authors: Schmieder, B. Bibcode: 1987dssp.work....5S Altcode: 1987ASSL..150....5S No abstract at ADS Title: On the onset of eruptive prominences and coronal transients. Authors: Simon, G.; Mein, N.; Schmieder, B.; Tandberg-Hanssen, E.; Wu, S. T. Bibcode: 1987PAICz..66..211S Altcode: 1987eram....1..211S During the Maximum Year, preflare and preeruptive phenomena have been observed which give a new idea on the association of eruptive prominences and coronal transients. Title: Surges as tracers of magnetic lines. Authors: Schmieder, B.; Mein, P.; Martres, M. J.; Simnett, G.; Tandberg-Hanssen, E. Bibcode: 1987PAICz..66..109S Altcode: 1987eram....1..109S The authors focus their study to chromospheric mass ejecta of cool material visible in Hα and occurring, with or without any flare. Associated with the events are either X ray emission or type III bursts. Title: Velocity Shear and Microturbulence in Solar Filaments Authors: Mein, P.; Schmieder, B. Bibcode: 1987dssp.work...17M Altcode: 1987ASSL..150...17M No abstract at ADS Title: On the existence of oscillations in solar filaments observed in H&alpha; and C IV lines. Authors: Schmieder, B.; Malherbe, J. M.; Mein, P.; Tandberg-Hanssen, E. Bibcode: 1986NASCP2442..197S Altcode: Time sequence observations of filaments in both the H&alpha; line and the 1548 Å C IV line were analyzed with the Fourier transform technique in the frequency range (1 - 10 mHz). No oscillation is detected in filaments except at the footpoints where a steady velocity gradient is large. The energy is probably due to convective motions rather than pressure oscillations. Title: Thermal stability analysis of the fine structure of solar prominences. Authors: Demoulin, Pascal; Malherbe, Jean-Marie; Schmieder, Brigitte; Raadu, Mickael A. Bibcode: 1986NASCP2442..143D Altcode: The authors analyse the linear thermal stability of a 2D periodic structure (alternatively hot and cold) in a uniform magnetic field. The energy equation includes wave heating (assumed proportional to density), radiative cooling and both conduction parallel and orthogonal to magnetic lines. The equilibrium is perturbed at constant gas pressure. The results compared with observations show that the computations suggest that the size of the unresolved threads could be of the order of 10 km only. Title: Filament eruption connected to photospheric activity. Authors: Simon, G.; Gesztelyi, L.; Schmieder, B.; Mein, N. Bibcode: 1986NASCP2442..229S Altcode: 1986copp.nasa..229S Two cases of activation of filaments that occured in regions of intense magnetic activity was studied. The simultaneous observations from Debrecen Observatory (white light and H alpha filtergram), and from Meudon Observatory (magnetogram, MSDP dopplergram and intensity maps in H alpha) gave a complementary set of data from which can be produced evidence of the influence of the photospheric magnetic field on the destabilization process of the filaments. On June 22, 1980, the eruption of the filament is associated with the motion of pores, which are manifestations of emerging flux knots. On September 3, 1980, the twisting motions in the filament are associated to the birth of a pore in its neighborhood. These observations are discussed. Title: Material ejecta in a disturbed solar filament Authors: Raadu, Michael A.; Malherbe, Jean-Marie; Schmieder, Brigitte; Mein, Pierre Bibcode: 1986STIN...8722594R Altcode: H alpha observations, using a multichannel subtractive double pass spectrograph were made of an active region filament which undergoes a sudden disappearance. The period of observation was from 10:45 UT to 13:30 UT on 22 June, 1981. Velocity and intensity fluctuations in H alpha were measured. The proper motions of ejecta were followed allowing their trajectories and vector velocities to be determined. To model the dynamics of ejecta, models using thermal or magnetic driving forces are compared. The most promising model explains the motion as the consequence of magnetic stresses acting on an isolated magnetized plasmoid in a diverging flux tube. Title: Constraints on filament models deduced from dynamical analysis. Authors: Simon, G.; Schmieder, B.; Demoulin, P.; Malherbe, J. M.; Poland, A. I. Bibcode: 1986NASCP2442..177S Altcode: 1986copp.nasa..177S The conclusions deduced from simultaneous observations with the Ultra-Violet Spectrometer and Polarimeter (UVSP) on the Solar Maximum Mission satellite, and the Multichannel Subtractive Double Pass (MSPD) spectrographs at Meudon and Pic du Midi observatories are presented. The observations were obtained in 1980 and 1984. All instruments have almost the same field of view and provide intensity and velocity maps at two temperatures. The resolution is approx. 0.5 to 1.5" for H alpha line and 3" for C IV. The high resolution and simultaneity of the two types of observations allows a more accurate description of the flows in prominences as functions of temperature and position. The results put some contraints on the models and show that dynamical aspects must be taken into account. Title: Dynamics of solar filaments. VI - Center-to-limb study of H-alpha and C IV velocities in a quiescent filament Authors: Simon, G.; Schmieder, B.; Demoulin, P.; Poland, A. I. Bibcode: 1986A&A...166..319S Altcode: The rotation of a stable quiescent filament from near disk center to the limb has been observed. Observations of intensity and velocity were made in H-alpha and C IV, and compared with magnetic field measurements. From the H-alpha observations, it is concluded that the filament is made up of many small scale magnetic features that are not coherently aligned along the neutral line. They are especially convoluted at the apparent 'footpoints'. The measured velocities are of the order of a few kilometers per second in both lines. However, the comparison of the standard deviations of the C IV velocities in and out of the filament as it rotates toward the limb shows that the vertical velocities in the filament are greater than the horizontal velocities. Measurements of velocity do not make it possible to distinguish between the Raadu-Kuperus (1973) or Kippenhahn-Schluter (1957) models for prominences because neither theory is adequately developed for this comparison. However, the observation of the many fine loops brings into question the correctness of either model. Title: The effect of solar oscillations on the brightness of the limb Authors: Schmieder, B.; Mein, P. Bibcode: 1986A&A...161....7S Altcode: Using the realistic atmosphere model VALC, and assuming a spherical geometry, the intensity of the solar limb is calculated, and measured amplitude fluctuations are compared with those expected due to oscillations. In the model, the atmosphere is perturbed successively by density and temperature fluctuations of amplitude smaller than the 6 percent limiting value, and the perturbations are defined by exponential laws corresponding to propagating or evanscent waves. It is shown that 5-minute oscillations lead to variations in the brightness gradient of less than 2 percent. Limb brightness fluctuation amplitudes observed with the Pic du Midi heliometer (Yerle, 1981) show peaks of 10 percent which have too high a value to be explained by solar wave theory. Title: Preflare activity. Authors: Priest, E. R.; Gaizauskas, V.; Hagyard, M. J.; Schmahl, E. J.; Webb, D. F.; Cargill, P.; Forbes, T. G.; Hood, A. W.; Steinolfson, R. S.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.; Karpen, J. T.; Martres, M. -J.; Porter, J. G.; Schmieder, B.; Smith, J. B., Jr.; Toomre, J.; Woodgate, B.; Waggett, P.; Bentley, R.; Hurford, G.; Schadee, A.; Schrijver, J.; Harrison, R.; Martens, P. Bibcode: 1986NASCP2439....1P Altcode: Contents: 1. Introduction: the preflare state - a review of previous results. 2. Magnetohydrodynamic instability: magnetic reconnection, nonlinear tearing, nonlinear reconnection experiments, emerging flux and moving satellite sunspots, main phase reconnection in two-ribbon flares, magnetic instability responsible for filament eruption in two-ribbon flares. 3. Preflare magnetic and velocity fields: general morphology of the preflare magnetic field, magnetic field shear, electric currents in the preflare active region, characterization of the preflare velocity field, emerging flux. 4. Coronal manifestations of preflare activity: defining the preflare regime, specific illustrative events, comparison of preflare X-rays and ultraviolet, preflare microwave intensity and polarization changes, non-thermal precursors, precursors of coronal mass ejections, short-lived and long-lived HXIS sources as possible precursors. Title: Characteristics, location and origin of flare activity in a complex active region Authors: Mechado, M. E.; Gary, G. A.; Hagyard, M. J.; Hernandez, A. M.; Rovira, M. G.; Schmieder, B.; Smith, J. B. Bibcode: 1986AdSpR...6f..33M Altcode: 1986AdSpR...6...33M We summarize the observational characteristics of series of multiple loop flares from a complex active region. The location of the highest observed photospheric magnetic shear is found to be the commonly observed site of flare onset, but not, in many cases, the magnetic region where the largest time-integrated energy release is observed. The observations thus reveal a consistent pattern of energy release processes as related to the magnetic field topology. Title: Dynamics of solar filaments. IV - Structure and mass flow of an active region filament Authors: Schmieder, B.; Malherbe, J. M.; Simon, G.; Poland, A. I. Bibcode: 1985A&A...153...64S Altcode: An active region filament near the center of the solar disk was observed on September 29-30, 1980, with the Multichannel Subtractive Double Pass Spectrograph of the Meudon solar tower and the UV Spectrograph and Polarimeter aboard the SMM satellite. H-alpha and C IV measurements are presently used to study brightness and material velocity in the 10,000 and 100,000 K temperature ranges, and photospheric magnetograms are used to investigate the underlying magnetic field. Attention is given to the constraints imposed on possible filament structures by observations, as well as the expected MHD relationships. Title: Mass motions in Hα absorbing structures of the solar chromosphere. Authors: Mein, P.; Malherbe, J. M.; Mein, N.; Mouradian, Z.; Schmieder, B. Bibcode: 1985MPARp.212..316M Altcode: Two examples of Hα absorbing structures have been observed with the Multichannel Subtractive Double Pass spectrograph at the turret dome (Pic du Midi) and at the solar tower (Meudon). In both cases, 9 points of the line profile are measured simultaneously in a 2D-field of view. Title: Twisting motions in a disturbed solar filament Authors: Schmieder, B.; Malherbe, J. M.; Raadu, M. A. Bibcode: 1985A&A...142..249S Altcode: Time sequences of the vertical velocity field in a disturbed solar active region filament (AR 2646) have been derived using the MSDP spectrograph operating in Hα at the Meudon Solar Tower. Following a period of systematic upward velocities a pair of closely aligned elongated regions of oppositely directed velocities develops and persists over several minutes. These velocities are interpreted in terms of a twisted magnetic flux rope model for the filament. The initial upward motions indicate that the flux rope is rising. This should lead to an expansion since the surrounding pressure is decreasing with height. Conservation of the current and the magnetic flux along the filament then requires twisting motions as the flux rope adjusts to a new radial equilibrium when rising into the corona. Title: Bright Points in H Wings and Mass Flows in the Solar Chromosphere Authors: Mein, P.; Malherbe, J. -M.; Mouradian, Z.; Mein, N.; Schmieder, B.; Muller, R. Bibcode: 1985LNP...233..203M Altcode: 1985hrsp.proc..203M Many mass flows in the chromosphere are physically connected with bright photospheric points. Bidimensional spectroscopy with high spatial resolution is very well suited for the study of both kinds of structures. The authors give some preliminary results derived from recent observations of the MSDP at the Pic-du-Midi. Title: Mass fluxes and magnetic structures in the chromosphere and the transition region; canopies. Authors: Mein, P.; Malherbe, J. -M.; Schmieder, B.; Simon, G.; Tandberg-Hanssen, E. Bibcode: 1985cdm..proc..206M Altcode: Preliminary results of applying a model of canopy-type magnetic lines to account for observed mass fluxes in the chromosphere and transiton region are presented. A set of center-to-limb data obtained in H-alpha and C IV, and to which the model is applied, is reported. The C IV line is assumed to form everywhere at the same height, and the H-alpha formation height is derived by assuming that the absorption coefficient is proportional to the local density. The density ratio between H-alpha and C IV levels is taken to be 100. From the results, it is concluded that the model accounts for the low ratio of radial velocities C IV/H-alpha at r = 0, the increase of H-alpha velocity near the limb, and the general center-to-limb behavior in both lines. Title: Recent Progress in the Physics of Solar Prominences Authors: Ribes, E.; Mein, P.; Malherbe, J. M.; Schmieder, B. Bibcode: 1985spit.conf..467R Altcode: No abstract at ADS Title: Dynamic evolution of recurrent mass ejections observed in Hα and C iv lines Authors: Schmieder, B.; Mein, P.; Martres, M. J.; Tandberg-Hanssen, E. Bibcode: 1984SoPh...94..133S Altcode: During a coordinated SMY program, the consecutive formation of two new active centers merging together within AR 2646 was observed from 28 August, to 5 September, 1980. The two preceding spots compressed an inverse polarity spot on 1 September 1980, causing recurrent ejecta of matter with time intervals around 10 min. The observations of the MSDP spectrograph operating in Hα at the Meudon Solar tower and of the UVSP spectrometer on SMM in the CIV 1548 Å line show that cold and hot material had the same projection, although the upward CIV velocity structure was more extended than the Hα one. We present evidence that observed contrasts of the Hα absorbing structure can be interpreted in terms of a dynamic `cloud model' overlying the chromosphere. Hα matter follows a magnetic channel with upward velocity around 20-30 km s−1 in the first phase of the event and with downward velocity (∼ - 40 km s−1) in the second phase. The stored energy is not sufficient to trigger a flare, nor even to propulse matter along the full length of an arch, because of the periodic reorganisation of the magnetic field. Title: Dynamics of solar filaments. III - Analysis of steady flows in H-alpha and C IV lines Authors: Schmieder, B.; Malherbe, J. M.; Mein, P.; Tandberg-Hanssen, E. Bibcode: 1984A&A...136...81S Altcode: A statistical analysis of intensities and radial velocities of several solar plage filaments (i.e. prominences seen on the solar disk) observed at disk center is presented. Intensity and radial (= vertical) velocity maps were derived from simultaneous 2D measurements of the H-alpha chromospheric line with the Multichannel Subtractive Double Pass spectrograph operating on the Meudon solar tower, and also obtained from 2D recordings of the C IV transition-zone line (1548 A) with the UV Spectrometer and Polarimeter aboard the Solar Maximum Mission satellite. A good correlation (around 0.5) is found between intensities in both lines, as well as between velocities. Persistent upflows are measured in both lines at the filament location. The mean vertical velocities are respectively 0.5 km/s in H-alpha and 5.6 km/s in C IV. The analysis of mass fluxes suggests that C IV upflows occur in the transition region around prominences rather than below, in the chromosphere-corona transition zone. Title: Phase-spectra of solar oscillations Authors: Staiger, J.; Mattig, W.; Schmieder, B.; Deubner, F. -L. Bibcode: 1984MmSAI..55..147S Altcode: Diode array measurements of intensity- and velocity-oscillations were made at the coude-telescope of Capri. From these observations phase-spectra were calculated to identify different types of waves within the solar atmosphere. The results indicate the existence of atmospheric gravity modes in the frequency-range below 2.5 mHz. No running acoustic waves were found in the photosphere for frequencies beyond 7.5 mHz. Vertical propagation seems only to take place for frequencies between 5 mHz and 7.5 mHz. No vertical propagation at all was found in the upper chromosphere. This seems to be due to the occurrence of wave reflection at the chromosphere-corona interface. Title: Study of giant cell motions and their possible relationship with the dynamics of filaments Authors: Schmieder, B.; Ribes, B.; Mein, E.; Malherbe, J. M. Bibcode: 1984MmSAI..55..319S Altcode: The systematic upward motions observed in filaments are presently considered in terms of a large scale convective flow, so that the converging or diverging direction of the subphotospheric flow is related to the magnetic pattern suggested by Kuperus and Raadu (1973) and Kippenhahn and Schlueter (1957). This scheme is tested by means of a method for the detection of the giant convection and its properties, through a differential rotation analysis that uses sunspots, faculae and filaments as outliners. The systematic latitudinal motions obtained in the preliminary results indicate the presence of large scale convection. The method may be used to establish a relationship between the magnetic pattern and the global convection. Title: Oscillations and stationary motions in filaments Authors: Schmieder, B.; Malherbe, J. M.; Mein, P.; Tandberg-Hanssen, E. Bibcode: 1984MmSAI..55..325S Altcode: Observation of oscillations in filaments, which are cold magnetic structures suspended in the corona, are used to test theories of coronal heating by acoustic waves high in the atmosphere. Long lived stationary motions observed in filaments suggest exchanges of material between them and the surrounding corona. A coupling between upflows in filaments and subphotospheric convective motions, dragging the field lines of the prominence magnetic support, is possible. Title: Flare build-up study - Homologous flares group - Part I Authors: Martres, M. -J.; Woodgate, B. E.; Mein, N.; Mouradian, Z.; Rayrole, J.; Schmieder, B.; Simon, G.; Soru-Escaut, I. Bibcode: 1984AdSpR...4g...5M Altcode: 1984AdSpR...4....5M According to the definition of the homology (optical) kept in reference, the homologous flares (HFl) may be observed wherever flares occur. The supposed supplementary preflaring conditions to have HFl may be either that the preflaring conditions have not been destroyed by the first flare (and then what mechanism has stopped the first and triggered the second ?) or that the preflaring conditions have been destroyed and rebuilt (and then, how ?). The analysis of data related to some selected active regions AR by the members of the working group, and the earlier works on HFl, may be used simultaneously to investigate the differences between one set of HFl and the others, the location of their sites and the evolution of HFl productive AR. This study brings the appearance of new footpoints from one flare to the following, the behaviour of cool arches (surging arches) leading to information on the changes of the magnetic configuration, and to peculiar characteristics of HFl, oif 2nd, 3rd in the time order concerning the chromospheric transition zone or coronal regions. The time delay between two consecutive homologous flares appears very quickly as an essential parameter to study homology. It was found that every set of flares (same type of site) is able to produce ``rafales'' of homologous flares, i.e. two, three, four, oir more flares with Δt in the range of one hour or less. The observations show no great chantes in macroscopic photospheric patterns (B, V) during this H flaring period. They lead to compare their temporal variation curves of flare brightness. A quantitative brightness parameter of homology relation has been defined. Some scale changes have also been detected in the dynamic spectrum of the site, and it is in good agreement with a very interesting theoretical suggestion made by P. Sturrock to produce such ``rafales''. It may be shown that the closely consecutive time-homologous flares (CCHF) or ``rafales'' represent a good tool to analyse the critical conditions related to the origin and the amount of energy, mechanism of storage and release, necessary and, perhaps, sufficient conditions. New statistical results, applied to the different selected homologous flare active regions are presented and show the existence in homologous flaring areas of a ``pivot'' of previous filaments interpreted as a signature of an anomaly in the Solar rotation. Title: Recurrent mass ejections observed in Hα and CIV Authors: Schmieder, B.; Simon, G.; Martres, M. -J.; Mein, P.; Mein, N.; Tandberg-Hanssen, E. Bibcode: 1984AdSpR...4g..27S Altcode: 1984AdSpR...4...27S Time sequences of recurrent mass ejections have been observed during a coordinated SMY program (1 Sept. 1980 - 23 Sept. 1980 - 2 Oct. 1980).

Comparison of the temporal evolution of Hα and CIV brightnesses shows a weak phase lag between H α and CIV maxima, in the case of homologous flares, with CIV brightness maxima preceding H α maxima. The analysis of the variation of the ejection velocities is expected to lead to the determination of an energy balance.

Such recurrent ejections could be due to periodic energy storage and periodic reorganisation of magnetic field as envisaged to occur for flares, but at lower energy levels. Title: Dynamics of a surge observed in the C IV and H alpha lines Authors: Schmieder, B.; Mein, P.; Vial, J. -C.; Tandberg-Hanssen, E. Bibcode: 1983A&A...127..337S Altcode: Time sequences of a surge have been obtained in Active Region 2701 during a coordinated SMY program, on October 2nd, 1980, while the MSDP spectrograph operated in H-alpha at the Meudon Solar Tower and the UVSP spectrometer on SMM observed in the 1548 A C IV resonance line. The cold (H-alpha) and hot (C IV) material follow the same channel, and the event lasts about 10 min in both lines. A good correlation is found between H-alpha and C IV velocities; radial velocities along the surge are in the range 40-60 km/s in both cases. The observations are consistent with the hypothesis that a pressure gradient drives the surge. The H-alpha data seem to indicate the presence of a shock wave in the chromosphere, while the C IV quantities (velocities, accelerations) vary on a very short time scale. Their maxima occur at some locations which could be interpreted as 'pinched' zones. Title: Dynamics of solar filaments. II - Mass motions in an active region filament from H-alpha center to limb observations Authors: Malherbe, J. M.; Schmieder, B.; Ribes, E.; Mein, P. Bibcode: 1983A&A...119..197M Altcode: The authors present the observations of a solar filament obtained at Meudon with the Hα spectroheliograph over a period of 10 d. They show a morphologically stable feature. The authors perform a statistical analysis of the radial velocity field. Assuming long-lived (several days) stationary motions, they compute a 3-dimensional velocity field from center to limb observations of the radial component of velocity in the stable feature. Different pictures of stationary material circulations are suggested and compared with theoretical models of filaments. On the contrary, in the case of short-lived (a few 10 min) flows of material, the authors interpret their data in terms of velocity loops in the magnetic structure supporting the filament, and they compare the results with the MHD model proposed by Ribes and Unno (1980). Possible improvements to this model are pointed out in the conclusion. Title: Dynamics of the eruptive prominence of 6 May 1980 and its relationship to the coronal transient Authors: Mein, N.; Schmieder, B.; Simon, G.; Tandberg-Hanssen, E.; Wu, S. T. Bibcode: 1982A&A...114..192M Altcode: The active prominence of the 6 May 1980 has been observed between 5.23 and 10.22 UT with the Ultraviolet Spectrometer and Polarimeter (UVSP) on board the Solar Maximum Mission (SMM) satellite. Intensities of 1548 A line of CIV and dopplershifts have been derived. A motion of the magnetic tube maintaining the prominence material is noted. This motion is followed by a coronal transient observed with the Coronagraph and Polarimeter (C/P) between 11 and 13 UT. It is suggested that the event is related to a MHD wave induced by a flare occurring behind the solar disk, and a MHD modeling of the perturbation is proposed. Title: Preflare heating of filaments Authors: Malherbe, J. M.; Simon, G.; Mein, P.; Mein, N.; Schmieder, B.; Vial, J. C. Bibcode: 1982AdSpR...2k..53M Altcode: 1982AdSpR...2...53M Disappearances of preflare filaments have been observed on June 22, 1980 (S07,W13) (flare at 13.04 U.T.) and September 3, 1980 (flare at 7.52 U.T.). The analysis of MSDP data (MEUDON) leads to the followings conclusions : - Disappearances begin a few minutes before the Hα impulsive phase. - The filaments can be seen again after the flares. - Upwards motions occur in several points, without disturbing significantly preëxisting downflows.

Velocity maps suggest shears or velocity loops.

The filament disappearance seems to be due to a heating mechanism beginning before the flare maximum. Title: A surge obsrved in Hα and CIV Authors: Schmieder, B.; Mein, P.; Vial, J. C.; Tandberg-Hanssen, E. Bibcode: 1982AdSpR...2k.225S Altcode: 1982AdSpR...2..225S Simultaneous Hα (MSDP at Meudon) and C IV (UVSP aboard SMM) measurements of Active Region 2701 were made on October 2, 1980. Isodensity and velocity maps were derived for both lines and superposed. A good correlation was found between Hα and C IV velocities. A surge was observed for 10 minutes. The base was located in a bright point in CIV and Hα, and escaping matter followed the same channel (``absorbing'' in Hα, ``emitting'' in C IV). The velocity along the surge was about 80 kms.-1 in Hα and 100 km s-1 in C IV. A loop appeared in C IV. We discuss the existing models and conclude that the vertical pressure gradient was capable of driving the surge. Title: Mass motions in a quiescent filament Authors: Malherbe, J. M.; Mein, P.; Schmieder, B. Bibcode: 1982AdSpR...2k..57M Altcode: 1982AdSpR...2R..57M The ``disparition brusque'' (DB) of a filament (N20, E35) has been observed above an active region with the Multichannel Subtractive Double Pass (MSDP) spectrograph operating on the Meudon Solar Tower, from 10h45 UT to 13h30 UT on June 22, 1981.

Velocity fields and intensity fluctuations are measured in the Hα line. The DB doesn't take place simultaneously in all parts of the filament : thin threads (thickness <3 arc seconds) with upward radial velocities reaching about 50 km/s are successively observed inside the prominence from S to N regions. These motions correspond likely to the rise of material along magnetic loops closely related to the prominence structure. The dynamics inside such a magnetic loop is investigated : a high speed flow (supersonic, likely superalfvénic) strongly accelerated is evidenced and a deformation of the flux tube, probably due to the centrifugal forces exerted by the flow on the magnetic lines, is suggested.

These results are compared with some theoretical works on dynamics inside magnetic loops, especially to siphon flow models. However, as in the case of the prominence support problem, better theoretical models are still needed. Title: About the onsets of closely-consecutive homologous flares Authors: Martres, M. J.; Mein, N.; Mein, P.; Mouradian, Z.; Rayrole, J.; Schmieder, B.; Simon, G.; Soru-Escaut, I.; Woodgate, B.; Strong, K. Bibcode: 1982AdSpR...2k.109M Altcode: 1982AdSpR...2R.109M The onsets of closely consecutive homologous flares (CCHF), which are separated by less than 6 hours and most often by about 1 hour, are compared with that of isolated flares (no flare in the region half a day before). Isolated flares appear to be formed of two components, a surging arch and a flaring arch, while a set of CCHF may be composed of consecutive elementary flares or of a series of complex ones. It is shown that the onset of eruptive flare phenomena is not the same for an isolated event and for a member of CCHF (excluding the first) as found in H-alpha and EUV observations, and probably in X-ray observations also. It is suggested that a CCHF set would become a single flare with episodic enhancement of brightness by taking account of the common H-alpha behavior of surging and flaring arches as well as the EUV emission. Title: Dynamics in the filaments. I - Oscillations in a quiescent filament Authors: Malherbe, J. M.; Schmieder, B.; Mein, P. Bibcode: 1981A&A...102..124M Altcode: A quiescent filament is observed by the 9 channel MSDP spectrograph operating on the Meudon Observatory tower during 720 s with a 30 s time step. The field view of 6 x 1 arcmin permits the study of the dynamics of 50 oscillation cells which increases the freedom degree comparatively to the one slit spectrograph techniques. A Fourier analysis of the radial velocity measured in the H-alpha line shows that the steady velocities are upward in the filament, while the chromospheric oscillations are almost undetectable inside the filament. Title: Mechanical flux in the solar chromosphere. III - Variation of the mechanical flux Authors: Mein, N.; Schmieder, B. Bibcode: 1981A&A....97..310M Altcode: The mechanical flux in the photosphere and the chromosphere is inferred from observations of atmospheric oscillations made over a large range of periods (60s-400s). Observations of Doppler shifts in Ca II and Mg I lines are related to velocities by means of heights of formation and modulation transfer functions deduced from weighting functions. The flux is derived from estimates of the amplitude and phase of the velocity at different heights in the atmosphere. The results imply that the energy dissipated by waves in a plane-parallel atmospheric model is insufficient to balance the radiative losses. The short-fall can reach a factor 100 in the high chromosphere. Heating of the corona by shock wave dissipation is inconsistent with our results. Title: Structure and Evolution of Velocities in Quiescent Filaments Authors: Martres, M. -J.; Mein, P.; Schmieder, B.; Soru-Escaut, I. Bibcode: 1981SoPh...69..301M Altcode: Simultaneous observations of radial velocities in a `quiescent' prominence seen in Hα on the disk and in the underlaying photosphere have been obtained in the Meudon Observatory: Doppler shifts in photospheric lines are weaker than in the surrounding regions (<0.3 km s-1); the scale of velocity structures is smaller (<104 km). The vertical component of velocities cannot be neglected. Hα Doppler shifts show that: (a) Highest velocities are often correlated with high brightness horizontal gradients, which suggests that filament and surrounding bright regions belong to the same geometrical and dynamical structure. (b) Fast motions (7 km s-1) have short life-times (a few minutes). (c) Slow motions in dark regions (<3 km s-1) are associated with blue shifts and may last several hours. This behaviour was confirmed in many other cases by filament observations with the 3-wavelength Hα patrol. This is consistent with EUV observations of the transition zone around prominences, but disagrees with `downward motions' as seen at the limb, unless these motions do not refer to material velocities. Title: Mechanical flux in the solar chromosphere. II - Determination of the mechanical flux Authors: Schmieder, B.; Mein, N. Bibcode: 1980A&A....84...99S Altcode: The observations of two lines of Ca II (8542-8498) made with the Sacramento Peak Tower and formation altitudes values Z(omega) for these two lines determined by weighting functions are used to evaluate, for each frequency omega, the mechanical flux F(omega) corresponding to the altitude Z(omega). Corrections taking into account the weakening of waves of wavelengths smaller than the line formation layer were applied to the flux. The corrected flux does not show a significant increase with the frequency (up to 10 mHz), which seems to indicate that nonthermal microturbulence does not correspond necessarily to progressive wave. The mechanical flux integrated over the frequency range 0-10 mHz reaches at the most 2000 erg/sq cm s in the middle chromosphere (1100 km). This is not sufficient to balance the energy losses of the transition zone and the corona. Title: Motions and Oscillations in Filaments Authors: Malherbe, J. M.; Martres, M. J.; Mein, P.; Schmieder, B.; Soru-Escaut, I. Bibcode: 1980jfss.conf..166M Altcode: No abstract at ADS Title: Observational Proof of the Inefficiency of the Chromospheric Heating by Acoustic Waves Authors: Mein, P.; Mein, N.; Schmieder, B. Bibcode: 1980jfss.conf...70M Altcode: No abstract at ADS Title: Waves in the low solar chromosphere. Authors: Schmieder, B. Bibcode: 1979A&A....74..273S Altcode: Observations of the Mg I line at 5172.7 A made with the Sacramento Peak Solar Tower have been analyzed statistically. The phase shifts between dopplershifts and between intensity and dopplershift fluctuations measured at different points in the Mg I line profile have been interpreted by wave theory, after a discussion of the formation altitudes of dopplershifts. Radiative dissipation seems to be efficient up to an altitude of 600 km, in the evanescent wave range (3-5 mHz). Some energy can be transported, but in the acoustic wave range (5-8 mHz), energy propagation is not detected. The observations in that frequency range are explained by the simultaneous presence of upward propagating waves and waves reflected in the high chromosphere. The presence of pure downward propagating waves around the temperature minimum can be anticipated. Title: Linear hydrodynamical equations coupled with radiative transfer in a non-isothermal atmosphere. II: Application to solar photospheric observations. Authors: Schmieder, B. Bibcode: 1978SoPh...57..245S Altcode: In a previous paper (Schmieder, 1977), we solved simultaneously the hydrodynamical and radiative transfer equations, so we do not have to assume any relaxation time of the atmosphere. In this paper, we use that theory to interpret photospheric observations of the Mg I line at 5172 Å. Title: Linear hydrodynamical equations coupled with radiative transfer in a non-isothermal atmosphere. I. Method. Authors: Schmieder, B. Bibcode: 1977SoPh...54..269S Altcode: A method coupling the hydrodynamical equations and radiative transfer in a realistic solar model atmosphere is described. The influence of the temperature gradient of the model and the radiative dissipation is pointed out. Title: Wave propagation in the photosphere. Authors: Schmieder, B. Bibcode: 1976SoPh...47..435S Altcode: Using a 32 minutes sequence of observation, brightness and velocity fluctuations in the wings of the MgI line at 5172.7 Å and Fe II line at 5197.578 Å are analysed. The analysis of phase shifts and amplitude ratios leads to the following conclusions: Title: Interpretation of photospheric observations by wave theory Authors: Schmieder, B. Bibcode: 1976pmas.conf..275S Altcode: No abstract at ADS Title: Fluctuations of Temperature and Density in the Photosphere Authors: Schmieder, B. Bibcode: 1972A&A....16...44S Altcode: The first part of this paper deals with the theoretical calculations of the intensities of two lines of Fe 1 (5196.067 A and 5195.482 A), as well as these of a point in the wing of the line b1 of Mg 1 and of the neighbouring continuum in a perturbed atmosphere. We point out that the intensities of the Fe 1 lines are very sensitive to temperature fluctuations whereas the intensity of the continuum is mainly sensitive to density fluctuations. In the second part, the study of the fluctuations of the mesured relative intensities allows us to determine the r.m.s. of the temperature and density fluctuations at two altitudes. We try to evaluate the contribution of respectively the oscfflatory phenomenon and the granulation. In the third part, we introduce the fluctuations associated to the granulation in a solar atmosphere modeL In this way, we obtain perturbed models which give variations of the relative brightness fluctuations across the solar disk. The average value of these variations is in good agreement with the results of Edmonds (1962) for > 0.5. Considering the fluctuations associated with the oscfflatory phenomenon, we determine a radiative minimum relaxation time of about 80s. Key words: photosphere - fluctuations of temperature and of density in the solar photosphere - fine structure - perturbed models in the photosphere - radiative relaxation time in the photosphere La partie est consacree l'e'tude des de deux rajes de Fe 1 (5196,067 A et 5195,482 A), de celle d'un point dans l'aile de la raie b1 de Mg I et de celle du continu voisin dans une atmosphire perturb . Nous montrons que lee des raies du fer sont sensibles aux fluctuations de temp6rature et que par contre celle du continu l'est surtout aux fluctuations de densi . Utilisant ces resultats , nous avons fait des observations la Tour Solaire de Meudon dans ce domaine de longueur d'onde. Dans une partie, I' ude des fluctuations des intensite's relatives mesuree's nous permet de les carts quadratiques moyens des fluctuations de la et de la densit6 pour deux altitudes. Une tentative est faite pour connattre la contribution relative du oscfflatoire et de la granulation dans ces fluctuations. Dans la partie nous introduisons les fluctuations associ6es a' la granulation dans un d' . Nous obtenons des perturbe's qui donnent des variations centre-bord de fluctuations de brillance relative. La moyenne de ces variations est en bon accord avec les mesures d'Edmonds (1962) pour > 0.5. En les fluctuations au 'ne oscfflatoire, nous d6terminons un temps de relaxation minimum de l'ordre de 80s. Title: Sur le Temps de Relaxation des Perturbations en Température dans la Photosphère Authors: Schmieder, B. Bibcode: 1969CRASB.269..935S Altcode: No abstract at ADS