Author name code: malherbe ADS astronomy entries on 2022-09-14 author:"Malherbe, Jean-Marie" ------------------------------------------------------------------------ Title: The SLED project and the dynamics of coronal flux ropes Authors: Malherbe, Jean-Marie; Mein, Pierre; Sayède, Frédéric; Rudawy, Pawel; Phillips, Kenneth; Keenan, Francis; Rybák, Jan Bibcode: 2022AdSpR..70.1562M Altcode: Investigations of the dynamics of the hot coronal plasma are crucial for understanding various space weather phenomena and making in-depth analyzes of the global heating of the solar corona. We present here numerical simulations of observations of siphon flows along loops (simple semi-circular flux ropes) to demonstrate the capabilities of the Solar Line Emission Dopplerometer (SLED), a new instrument under construction for imaging spectroscopy. It is based on the Multi-channel Subtractive Double Pass (MSDP) technique, which combines the advantages of filters and slit spectrographs. SLED will observe coronal structures in the forbidden lines of FeX 6374 Å and FeXIV 5303 Å, and will measure Doppler shifts up to 150 km s-1 at high precision (50 m s-1) and cadence (1 Hz). It is optimized for studies of the dynamics of fast evolving events such as flares or Coronal Mass Ejections (CMEs), as well as for the detection of high-frequency waves. Observations will be performed with the coronagraph at Lomnický Štít Observatory (LSO), and will also occur during total solar eclipses as SLED is a portable instrument. Title: Jules Janssen, the birth of solar physics, the foundation of Meudon Observatory, and the Mont Blanc adventure (1875-1895) Authors: Malherbe, J. -M. Bibcode: 2022JAHH...25..187M Altcode: Jules Janssen is a well known astronomer. In 1868 he introduced the spectroscopic technique to observe solar prominences. He also invented innovative methods in imagery and photography. This paper focuses on the period from the foundation of Meudon Observatory, associated with the birth of astrophysics and solar physics in France, to the Mont Blanc saga, with the creation of the observatory and the three scientific ascents by Janssen to the top of the mountain. As most documents are written in French, this fantastic and unbelievable adventure at the end of the nineteenth century, deserves to be told in English, and it reveals the long-term vision of Janssen's astronomy. It involved specialized instruments, located in well-chosen places where atmospheric interference was minimized. High altitude observations, from Mont Blanc (or from balloons, also experienced by Janssen), prefigure space astronomy which developed Title: Monitoring fast solar chromospheric activity: the MeteoSpace project Authors: Malherbe, Jean-Marie; Corbard, Thierry; Barbary, Gaële; Morand, Frédéric; Collin, Claude; Crussaire, Daniel; Guitton, Florence Bibcode: 2022ExA....53.1127M Altcode: 2022ExA...tmp...33M We present in this reference paper an instrumental project dedicated to the monitoring of solar activity during solar cycle 25. It concerns the survey of fast evolving chromospheric events implied in Space Weather, such as flares, coronal mass ejections, filament instabilities and Moreton waves. Coronal waves are produced by large flares around the solar maximum and propagate with chromospheric counterparts; they are rare, faint, difficult to observe, and for that reason, challenging. They require systematic observations with automatic, fast and multi-channel optical instruments. MeteoSpace is a high cadence telescope assembly specially designed for that purpose. The large amount of data will be freely available to the solar community. We describe in details the optical design, the qualification tests and capabilities of the telescopes, and show how waves can be detected. MeteoSpace will be installed at Calern observatory (Côte d'Azur, 1270 m) and will be in full operation in 2023. Title: The Solar Line Emission Dopplerometer project Authors: Malherbe, Jean-Marie; Mein, Pierre; Sayède, Frédéric; Rudawy, Pawel; Phillips, Kenneth; Keenan, Francis; Rybák, Jan Bibcode: 2022ExA....53...83M Altcode: 2021ExA...tmp..125M; 2021arXiv211001645M Observations of the dynamics of solar coronal structures are necessary to investigate space weather phenomena and global heating of the corona. The profiles of high temperature lines emitted by the hot plasma are usually integrated by narrow band filters or recorded by classical spectroscopy. We present in this paper details of a new transportable instrument (under construction) for imaging spectroscopy: the Solar Line Emission Dopplerometer (SLED). It uses the Multi-channel Subtractive Double Pass (MSDP) technique, which combines the advantages of both filters and narrow slit spectrographs, i.e. high temporal, spatial and spectral resolutions. The SLED will measure at high cadence (1 Hz) the line-of-sight velocities (Doppler shifts) of hot coronal loops, in the forbidden lines of FeX 6374 Å and FeXIV 5303 Å. It will follow the dynamics of fast evolving events of solar activity such as flares or Coronal Mass Ejections (CMEs), and also study coronal heating by short period waves. Observations will be performed with the coronagraph at the Lomnický Štít Observatory (LSO, in Slovakia) or during total eclipses. The SLED will also observe the dynamics of solar prominences in Hα 6563 Å or He D3 5876 Å lines when mounted on the Białków coronagraph (near Wrocław, Poland). It is fully compatible with polarimetric measurements by various techniques. Title: Five decades of solar research at the Pic du Midi Turret-Dome (1960-2010). Part 2: High spatial resolution imagery Authors: Muller, R.; Roudier, Th.; Malherbe, J. -M. Bibcode: 2021JAHH...24..921M Altcode: In the Part 2 of the series of two papers dedicated to the review on fifty years of advances in solar instrumentation and solar physics made at the Pic du Midi Turret-Dome (1960-2010) in various domains, we pre-sent the main observations and results obtained in the field of high resolution imagery, for which the instrument was originally designed. Title: Reconstructing solar irradiance from historical Ca II K observations. I. Method and its validation Authors: Chatzistergos, Theodosios; Krivova, Natalie A.; Ermolli, Ilaria; Yeo, Kok Leng; Mandal, Sudip; Solanki, Sami K.; Kopp, Greg; Malherbe, Jean-Marie Bibcode: 2021A&A...656A.104C Altcode: 2021arXiv210905844C Context. Knowledge of solar irradiance variability is critical to Earth's climate models and understanding the solar influence on Earth's climate. Direct solar irradiance measurements have only been available since 1978. Reconstructions of past variability typically rely on sunspot data. However, sunspot records provide only indirect information on the facular and network regions, which are decisive contributors to irradiance variability on timescales of the solar cycle and longer.
Aims: Our ultimate goal is to reconstruct past solar irradiance variations using historical full-disc Ca II K observations to describe the facular contribution independently of sunspot observations. Here, we develop the method and test it extensively by using modern CCD-based (charge-coupled device) Ca II K observations. We also carry out initial tests on two photographic archives.
Methods: We employ carefully reduced and calibrated Ca II K images from 13 datasets, including some of the most prominent series, such as those from the Meudon, Mt Wilson, and Rome observatories. We convert them to unsigned magnetic field maps and then use them as input to the adapted Spectral and Total Irradiance Reconstruction (SATIRE) model to reconstruct total solar irradiance (TSI) variations over the period 1978-2019, for which direct irradiance measurements are available.
Results: The reconstructed irradiance from the analysed Ca II K archives agrees well with direct irradiance measurements and existing reconstructions. The model also returns good results on data taken with different bandpasses and images with low spatial resolution. Historical Ca II K archives suffer from numerous inconsistencies, but we show that these archives can still be used to reconstruct TSI with reasonable accuracy provided the observations are accurately processed and the effects of changes in instrumentation and instrumental parameters are identified and accounted for. The reconstructions are relatively insensitive to the TSI reference record used to fix the single free parameter of the model. Furthermore, even employment of a series, itself reconstructed from Ca II K data, as a reference for further reconstructions returns nearly equally accurate results. This will enable the Ca II K archives without an overlap with direct irradiance measurements to be used to reconstruct past irradiance.
Conclusions: By using the unsigned magnetic maps of the Sun reconstructed from modern high-quality Ca II K observations as input into the SATIRE model, we can reconstruct solar irradiance variations nearly as accurately as from directly recorded magnetograms. Historical Ca II K observations can also be used for past irradiance reconstructions but need additional care, for example identifying and accounting for discontinuities and changes in the quality of the data with time. Title: Five decades of solar research at the Mic du Midi Turret-Dome (1960-2010). Part 1: Overview of instrumentation and observations Authors: Roudier, Th.; Malherbe, J. -M.; Rozelot, J. -P.; Mein, P.; Muller, R. Bibcode: 2021JAHH...24..585R Altcode: The Pic du Midi Turret-Dome, known as 'Lunette Jean Rösch'or LJR ('lunette' for refractor in French), was scientifically active during five decades between 1960 and 2010. It was dedicated to high spatial resolution observations in solar astronomy. We review fifty years of advances in solar instrumentation and solar physics made by this instrument in various domains, which took advantage of the good seeing at Pic du Midi. First, we summarize some of the LJR results in broad-band and wide-field imagery of the photosphere; as this topic was the initial goal and has been the most important contribution of the refractor, details will be provided in Part 2. Then, we present spectro-polarimetric instrumentation and observations with narrow slit and imaging spectroscopy of the photosphere and the chromosphere. The Turret-Dome also housed an original spectro-coronagraph, and observations of the high temperature coronal plasma are highlighted. Finally, we describe progress in the determination of the solar shape with the heliometer. The LJR remained active until the launch of the Hinode and Solar Dynamics Observatory satellites (in 2006 and 2010, respectively). Title: Changes in granulation scales over the solar cycle seen with SDO/HMI and Hinode/SOT Authors: Ballot, J.; Roudier, T.; Malherbe, J. M.; Frank, Z. Bibcode: 2021A&A...652A.103B Altcode: 2021arXiv210603556B Context. The Sun is the only star where the superficial turbulent convection can be observed at very high spatial resolution. The Solar Dynamics Observatory (SDO) has continuously observed the full Sun from space with multi-wavelength filters since July 2010. In particular, the Helioseismic and Magnetic Imager (HMI) instrument takes high-cadence frames (45 s) of continuum intensity in which solar granulation is visible.
Aims: We aimed to follow the evolution of the solar granules over an activity cycle and look for changes in their spatial properties.
Methods: We investigated the density of granules and their mean area derived directly from the segmentation of deconvolved images from SDO/HMI. To perform the segmentation, we define granules as convex elements of images.
Results: We measured an approximately 2% variation in the density and the mean area of granules over the cycle, the density of granules being greater at solar maximum with a smaller granule mean area. The maximum density appears to be delayed by about one year compared to classical activity indicators, such as the sunspot number. We complemented this study with high-spatial-resolution observations obtained with Hinode/SOTBFI (Solar Optical Telescope Broadband Filter Imager), which are consistent with our results.
Conclusions: The observed variations in solar granulation at the disc centre reveal a direct insight into the change in the physical properties that occur in the upper convective zone during a solar cycle. These variations can be due to interactions between convection and magnetic fields, either at the global scale or, locally, at the granulation scale. Title: Photospheric downflows observed with SDO/HMI, HINODE, and an MHD simulation Authors: Roudier, T.; Švanda, M.; Malherbe, J. M.; Ballot, J.; Korda, D.; Frank, Z. Bibcode: 2021A&A...647A.178R Altcode: 2021arXiv210303077R Downflows on the solar surface are suspected to play a major role in the dynamics of the convection zone, at least in its outer part. We investigate the existence of the long-lasting downflows whose effects influence the interior of the Sun but also the outer layers. We study the sets of Dopplergrams and magnetograms observed with Solar Dynamics Observatory and Hinode spacecrafts and an magnetohydrodynamic (MHD) simulation. All of the aligned sequences, which were corrected from the satellite motions and tracked with the differential rotation, were used to detect the long-lasting downflows in the quiet-Sun at the disc centre. To learn about the structure of the flows below the solar surface, the time-distance local helioseismology was used. The inspection of the 3D data cube (x, y, t) of the 24 h Doppler sequence allowed us to detect 13 persistent downflows. Their lifetimes lie in the range between 3.5 and 20 h with a sizes between 2″ and 3″ and speeds between −0.25 and −0.72 km s−1. These persistent downflows are always filled with the magnetic field with an amplitude of up to 600 Gauss. The helioseismic inversion allows us to describe the persistent downflows and compare them to the other (non-persistent) downflows in the field of view. The persistent downflows seem to penetrate much deeper and, in the case of a well-formed vortex, the vorticity keeps its integrity to the depth of about 5 Mm. In the MHD simulation, only sub-arcsecond downflows are detected with no evidence of a vortex comparable in size to observations at the surface of the Sun. The long temporal sequences from the space-borne allows us to show the existence of long-persistent downflows together with the magnetic field. They penetrate inside the Sun but are also connected with the anchoring of coronal loops in the photosphere, indicating a link between downflows and the coronal activity. A links suggests that EUV cyclones over the quiet Sun could be an effective way to heat the corona. Title: Four Decades of Advances from MSDP to S4I and SLED Imaging Spectrometers Authors: Mein, P.; Malherbe, J. -M.; Sayède, F.; Rudawy, P.; Phillips, K. J. H.; Keenan, F. P. Bibcode: 2021SoPh..296...30M Altcode: 2021arXiv210103918M The Multichannel Subtractive Double Pass (MSDP) is an imaging spectroscopy technique, which allows observations of spectral line profiles over a 2D field of view with high spatial and temporal resolution. It has been intensively used since 1977 on various spectrographs (Meudon, Pic du Midi, the German Vacuum Tower Telescope, THEMIS, Wrocław). We summarize previous developments and describe the capabilities of a new design that has been developed at Meudon and that has higher spectral resolution and increased channel number: Spectral Sampling with Slicer for Solar Instrumentation (S4I), which can be combined with a new and fast polarimetry analysis. This new generation MSDP technique is well adapted to large telescopes. Also presented are the goals of a derived compact version of the instrument, the Solar Line Emission Dopplerometer (SLED), dedicated to dynamic studies of coronal loops observed in the forbidden iron lines, and prominences. It is designed for observing total solar eclipses, and for deployment on the Wrocław and Lomnicky peak coronagraphs respectively for prominence and coronal observations. Title: Evolution of exploding granules from coordinated observations by THEMIS, IRIS, SDO/HMI, and HINODE, and a simulation Authors: Roudier, T.; Malherbe, J. M.; Gelly, B.; Douet, R.; Frank, Z.; Dalmasse, K. Bibcode: 2020A&A...641A..50R Altcode: 2020arXiv200712438R Exploding granules constitute the strongest horizontal flows on the quiet Sun and contribute to the structure of the surface horizontal velocity fields which build the large-scale organization of the discrete magnetic field. In this work we explore exploding granule expansion through the observations of the ground-based THEMIS telescope, IRIS, SDO, and the Hinode space-borne instruments, and finally with the magnetohydrodynamics simulation. We evaluate the detection and the expansion of exploding granules at several wavelengths and at various spatial and temporal resolutions. To analyze the different temporal sequences, two methods of image segmentation are applied to select the granules. The first allows us to follow individually the exploding granules observed simultaneously by THEMIS, IRIS, and SDO. The second uses long time independent sequences from THEMIS, IRIS, SDO, Hinode, and a simulation. In the first method (called manual) the segmentation isolates the cell of the granules (bright granules and intergranular parts), while in the second method (called statistical) only the bright part of the granules are isolated. The results obtained with simultaneous or distinct temporal observations using the two methods of segmentation are in good agreement. The granule area evolves linearly with an expansion velocity that decreases with the radius. A rapid decrease in the velocity expansion in the first two minutes is observed. The detection and measurement of the dynamics of the explosive granules can be performed from ground- and space-based instruments. Our work reveals the usefulness of SDO data, with low spatial resolution, to study the dynamics of the exploding granules all over the solar surface. Title: Major Volcanic Eruptions and Their Impacts on Southern Hemisphere Temperatures During the Late 19th and 20th Centuries, as Simulated by CMIP5 Models Authors: Harvey, P. J.; Grab, S. W.; Malherbe, J. Bibcode: 2020GeoRL..4787792H Altcode: While much is known about the impacts of volcanic forcing on Northern Hemisphere (NH) climates, knowledge about Southern Hemisphere (SH) responses is still in its infancy. We examine volcanic impacts on SH temperatures following eight major late 19th and 20th century eruptions (Agung, 1963; Colima, 1913; El Chichón, 1982; Pinatubo, 1991; Krakatau, 1883; Quizapu, 1932; Santa Maria, 1902; Tarawera, 1886). Coupled Model Intercomparison Project, Phase 5 (CMIP5) historical simulations are used to analyze near-surface land temperatures. We demonstrate that four of the eight major eruptions (Krakatau, Santa Maria, Agung, and Pinatubo) significantly lowered mean SH temperatures; these tropical eruptions emitted at least 20 Tg of SO2 into the stratosphere. SH responses typically lagged NH temperature cooling responses by 1-2 months, excluding Pinatubo. Responses differ spatially and temporally with each eruption, highlighting the importance of investigating events individually. Overall, we observe relatively strong (between -0.19°C and -0.36°C) austral autumn/winter SH cooling. Title: Analysis of full-disc Ca II K spectroheliograms. III. Plage area composite series covering 1892-2019 Authors: Chatzistergos, Theodosios; Ermolli, Ilaria; Krivova, Natalie A.; Solanki, Sami K.; Banerjee, Dipankar; Barata, Teresa; Belik, Marcel; Gafeira, Ricardo; Garcia, Adriana; Hanaoka, Yoichiro; Hegde, Manjunath; Klimeš, Jan; Korokhin, Viktor V.; Lourenço, Ana; Malherbe, Jean-Marie; Marchenko, Gennady P.; Peixinho, Nuno; Sakurai, Takashi; Tlatov, Andrey G. Bibcode: 2020A&A...639A..88C Altcode: 2020arXiv200501435C Context. Studies of long-term solar activity and variability require knowledge of the past evolution of the solar surface magnetism. The archives of full-disc Ca II K observations that have been performed more or less regularly at various sites since 1892 can serve as an important source of such information.
Aims: We derive the plage area evolution over the last 12 solar cycles by employing data from all Ca II K archives that are publicly available in digital form, including several as-yet-unexplored Ca II K archives.
Methods: We analysed more than 290 000 full-disc Ca II K observations from 43 datasets spanning the period between 1892-2019. All images were consistently processed with an automatic procedure that performs the photometric calibration (if needed) and the limb-darkening compensation. The processing also accounts for artefacts affecting many of the images, including some very specific artefacts, such as bright arcs found in Kyoto and Yerkes data. Our employed methods have previously been tested and evaluated on synthetic data and found to be more accurate than other methods used in the literature to treat a subset of the data analysed here.
Results: We produced a plage area time-series from each analysed dataset. We found that the differences between the plage areas derived from individual archives are mainly due to the differences in the central wavelength and the bandpass used to acquire the data at the various sites. We empirically cross-calibrated and combined the results obtained from each dataset to produce a composite series of plage areas. The 'backbone' approach was used to bridge the series together. We have also shown that the selection of the backbone series has little effect on the final composite of the plage area. We quantified the uncertainty of determining the plage areas with our processing due to shifts in the central wavelength and found it to be less than 0.01 in fraction of the solar disc for the average conditions found on historical data. We also found the variable seeing conditions during the observations to slightly increase the plage areas during the activity maxima.
Conclusions: We provide the most complete so far time series of plage areas based on corrected and calibrated historical and modern Ca II K images. Consistent plage areas are now available on 88% of all days from 1892 onwards and on 98% from 1907 onwards.

The whole series described in the paper 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/cat/J/A+A/639/A88 Title: Optical instrumentation for chromospheric monitoring during solar cycle 25 at Paris and Côte d'Azur observatories Authors: Malherbe, Jean-Marie; Corbard, Thierry; Dalmasse, Kevin Bibcode: 2020JSWSC..10...31M Altcode: We present the observing program proposed by Paris and Côte d'Azur Observatories for monitoring solar activity during the upcoming cycle 25 and providing near real time images and movies of the chromosphere for space-weather research and applications. Two optical instruments are fully dedicated to this task and we summarize their capabilities. Short-term and fast-cadence observations of the chromosphere will be performed automatically at Calern observatory (Côte d'Azur), where dynamic events, as flare development, Moreton waves, filament instabilities and Coronal Mass Ejections onset, will be tracked. This new set of telescopes will operate in 2021 with narrow bandpass filters selecting Hα and CaII K lines. We present the instrumental design and a simulation of future images. At Meudon, the Spectroheliograph is well adapted to the long-term and low-cadence survey of chromospheric activity by recently improved and optimized spectroscopic means. Surface scans deliver daily (x, y, λ) datacubes of Hα, CaII K and CaII H line profiles. We describe the nature of available data and emphasize the new calibration method of spectra. Title: VizieR Online Data Catalog: Plage area composite series (Chatzistergos+, 2020) Authors: Chatzistergos, T.; Ermolli, I.; Krivova, N. A.; Solanki, S. K.; Banerjee, D.; Barata, T.; Belik, M.; Gafeira, R.; Garcia, A.; Hanaoka, Y.; Hegde, M.; Klimes, J.; Korokhin, V. V.; Lourenco, A.; Malherbe, J. -M.; Marchenko, G. P.; Peixinho, N.; Sakurai, T.; Tlatov, A. G. Bibcode: 2020yCat..36390088C Altcode: Annual, monthly, and daily values of the plage area composite series.

The archives included are those from the Arcetri (Ar), Baikal (Ba), Brussels (Br), Calern (CL), Catania (CT), Coimbra (Co), Kanzelhoehe (Ka), Kenwood (Ke), Kharkiv (Kh), Kislovodsk (Ki), Kodaikanal taken with the spectroheliograph (Ko), Kodaikanal taken with the Twin telescope (KT), Kodaikanal taken with the White-Light Active Region Monitor (WARM) telescope (KW), Kyoto (Ky), Manila (Ma), Mauna Loa (ML) taken with the Precision Solar Photometric Telescope (PSPT), McMath-Hulbert (MM), Mees (MS), Meudon taken with the spectroheliograph (MD1), Meudon taken with an interference filter (MD2), Mitaka taken with the spectroheliograph (Mi1), Mitaka taken with the Solar Flare Telescope with an interference filter (Mi2), Mt Wilson (MW), Pic du Midi (PM), SOlar Diameter Imager and Surface Mapper (SODISM) telescope on board the PICARD spacecraft (PS), Rome taken with the equatorial bar at Monte Mario (Ro), Rome taken with the PSPT (RP1), Rome taken with the PSPT with narrow bandwidth (RP2), Sacramento Peak (SP), San Fernando taken with the Cartesian Full-Disk Telescope (CFDT) 1 (SF1), San Fernando taken with the CFDT2 (SF2), Schauinsland (Sc), Teide (Te) taken with the Chromospheric Telescope (ChroTel), Upice (UP), Valasske Mezirici (VM), Wendelstein (WS), and Yerkes (YR) sites

(3 data files). Title: Meteospace, a New Instrument for Solar Survey at the Calern Observatory Authors: Malherbe, J. -M.; Corbard, Th; Dalmasse, K.; The Meteospace team Bibcode: 2020arXiv200102162M Altcode: High cadence observations of solar activity (active regions, flares, filaments) in the H$\alpha$ line were performed at Meudon and Haute Provence Observatories from 1956 to 2004. More than 7 million images were recorded, mainly on 35 mm films. After a review of the scientific interest of solar surveys at high temporal resolution and the historical background, we describe the new instrument which will operate automatically in 2020 at the Calern station of the Côte d'Azur observatory (1270 m). It will replace the former heliographs with improved cadence, seeing and time coverage. We summarize the capabilities of the optical design and present new scientific perspectives in terms of flare onset and Moreton wave detection. Title: Meteospace, a New Instrument for Solar Survey at the Calern Observatory Authors: Malherbe, J. -M.; Corbard, Th.; Dalmasse, K.; Meteospace Team Bibcode: 2019SoPh..294..177M Altcode: High-cadence observations of solar activity (active regions, flares, filaments) in the Hα line were performed at Meudon and Haute Provence Observatories from 1956 to 2004. More than 7 million images were recorded, mainly on 35 mm films. After a review of the scientific interest of solar surveys at high temporal resolution and the historical background, we describe the new instrument which will operate automatically in 2020 at the Calern station of the Côte d'Azur observatory (1270 m). It will replace the former heliographs with improved cadence, seeing and time coverage. We summarize the capabilities of the optical design and present new scientific perspectives in terms of flare onset and Moreton wave detection. Title: The New 2018 Version of the Meudon Spectroheliograph Authors: Malherbe, J. -M.; Dalmasse, K. Bibcode: 2019SoPh..294...52M Altcode: 2020arXiv200102638M Daily full-disk observations of the solar photosphere and chromosphere started at the Meudon Observatory in 1908. After a review of the scientific context and the historical background, we describe the instrumental characteristics and capabilities of the new version operating since 2018. The major change is the systematic recording of full line profiles over the entire solar disk providing 3D data cubes. Spectral and spatial sampling are both improved. Classical 2D images of the Sun at fixed wavelength are still delivered. We summarize the different processing levels of on-line data and briefly review the new scientific perspectives. Title: Link between trees of fragmenting granules and deep downflows in MHD simulation Authors: Roudier, T.; Malherbe, J. M.; Stein, R. F.; Frank, Z. Bibcode: 2019A&A...622A.112R Altcode: 2019arXiv190103255R Context. Trees of fragmenting granules (TFG) and associated flows are suspected to play a major role in the formation of the network in the quiet Sun. We investigate the counterparts, in terms of dynamics, of surface structures detectable by high resolution observations in deeper layers up to 15 Mm, which are only available from numerical simulations.
Aims: The first aim is to demonstrate that TFG can be evidenced either from surface intensitites, vertical (Vz), or Doppler (Vdop) velocities. The second is to show that horizontal flows, which are derived from intensities or Vz/Vdop flows, are in good agreement, and that this is the case for observations and numerical simulations. The third objective is to apply this new Vz-based method to a 3D simulation to probe relationships between horizontal surface flows, TFG, and deep vertical motions.
Methods: The TFG were detected after oscillation filtering of intensities or Vz/Vdop flows, using a segmentation and labelling technique. Surface horizontal flows were derived from local correlation tracking (LCT) and from intensities or Vz/Vdop flows. These methods were applied to Hinode observations, 2D surface results of a first simulation, and 3D Vz data of a second simulation.
Results: We find that TFG and horizontal surface flows (provided by the LCT) can be detected either from intensities or Vz/Vdop component, for high resolution observations and numerical simulations. We apply this method to a 3D run providing the Vz component in depth. This reveals a close relationship between surface TFG (5 Mm mesoscale) and vertical downflows 5 Mm below the surface. We suggest that the dynamics of TFG form larger scales (the 15-20 Mm supergranulation) associated with 15 Mm downflowing cells below the surface.
Conclusions: The TFG and associated surface flows seem to be essential to understanding the formation and evolution of the network at the meso and supergranular scale.

Movies associated to Figs. 3, 11, 12, and 14 are availabe at https://www.aanda.org 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: Prototype of S4EI (spectral sampling with slicer for stellar and extragalactical instrumentation): a new generation 3D Spectro-imager Authors: Sayède, F.; Puech, M.; Mein, P.; Galicher, R.; Malherbe, J. -M.; Amans, J. -P. Bibcode: 2018SPIE10702E..54S Altcode: S4EI (Spectral Sampling with Slicer for Stellar and Extragalactical Instrumentation) is a new concept for extending Multichannel Subtractive Double Pass (ie S4I - Spectral Sampling with Slicer for Solar Instrumentation) to night-time astronomy. The Multichannel Subtractive Double Pass (MSDP) spectrographs have been widely used in solar spectroscopy because of their ability to provide an excellent compromise between field of view and the spatial and spectral resolutions. Compared with other spectrographs, MSDP can deliver simultaneous monochromatic images without any time-scanning requirements (as the standard Fabry-Perot), with limited loss of flux. Spatial resolution is the same as for an Imager given by the telescope: it can be very high. It is based on new generation reflecting plane image slicers working with large apertures specific to night-time telescopes. The resulting design could be potentially very attractive and innovative for different domains of astronomy, e.g., the simultaneous spatial mapping of accurately flux-calibrated emission lines between OH sky lines in extragalactic astronomy or the simultaneous imaging of stars, exoplanets and interstellar medium. The determination of physical and chemical properties of galaxies needs to observe several emission lines at different wavelengths. The combination of these lines gives access to the distribution in dust, star formation rate, metallicity, the kinematics or even to the electron density of the gas in the galaxies. The spatial resolution of MSDP allows, like the 3D or integral field spectrographs the construction of spatial distribution maps. The advantage of S4EI is that by measuring simultaneously the different lines, the relative errors of the flux calibration between the different wavelengths of the lines are potentially limited by the uncertainty of the calibration source used, which is expected to significantly reduce the associated errors and thus increase the precision and accuracy of estimates. Title: Large-scale photospheric motions determined from granule tracking and helioseismology from SDO/HMI data Authors: Roudier, Th.; Švanda, M.; Ballot, J.; Malherbe, J. M.; Rieutord, M. Bibcode: 2018A&A...611A..92R Altcode: 2017arXiv171205255R Context. Large-scale flows in the Sun play an important role in the dynamo process linked to the solar cycle. The important large-scale flows are the differential rotation and the meridional circulation with an amplitude of km s-1 and few m s-1, respectively. These flows also have a cycle-related components, namely the torsional oscillations. Aim. Our attempt is to determine large-scale plasma flows on the solar surface by deriving horizontal flow velocities using the techniques of solar granule tracking, dopplergrams, and time-distance helioseismology.
Methods: Coherent structure tracking (CST) and time-distance helioseismology were used to investigate the solar differential rotation and meridional circulation at the solar surface on a 30-day HMI/SDO sequence. The influence of a large sunspot on these large-scale flows with a specific 7-day HMI/SDO sequence has been also studied.
Results: The large-scale flows measured by the CST on the solar surface and the same flow determined from the same data with the helioseismology in the first 1 Mm below the surface are in good agreement in amplitude and direction. The torsional waves are also located at the same latitudes with amplitude of the same order. We are able to measure the meridional circulation correctly using the CST method with only 3 days of data and after averaging between ± 15° in longitude.
Conclusions: We conclude that the combination of CST and Doppler velocities allows us to detect properly the differential solar rotation and also smaller amplitude flows such as the meridional circulation and torsional waves. The results of our methods are in good agreement with helioseismic measurements. Title: Dynamics of Trees of Fragmenting Granules in the Quiet Sun: Hinode/SOT Observations Compared to Numerical Simulation Authors: Malherbe, J. -M.; Roudier, T.; Stein, R.; Frank, Z. Bibcode: 2018SoPh..293....4M Altcode: 2018arXiv180401870M We compare horizontal velocities, vertical magnetic fields, and the evolution of trees of fragmenting granules (TFG, also named families of granules) derived in the quiet Sun at disk center from observations at solar minimum and maximum of the Solar Optical Telescope (SOT on board Hinode) and results of a recent 3D numerical simulation of the magneto-convection. We used 24-hour sequences of a 2D field of view (FOV) with high spatial and temporal resolution recorded by the SOT Broad band Filter Imager (BFI) and Narrow band Filter Imager (NFI). TFG were evidenced by segmentation and labeling of continuum intensities. Horizontal velocities were obtained from local correlation tracking (LCT) of proper motions of granules. Stokes V provided a proxy of the line-of-sight magnetic field (BLOS). The MHD simulation (performed independently) produced granulation intensities, velocity, and magnetic field vectors. We discovered that TFG also form in the simulation and show that it is able to reproduce the main properties of solar TFG: lifetime and size, associated horizontal motions, corks, and diffusive index are close to observations. The largest (but not numerous) families are related in both cases to the strongest flows and could play a major role in supergranule and magnetic network formation. We found that observations do not reveal any significant variation in TFG between solar minimum and maximum. Title: Dynamics of the photosphere along the solar cycle from SDO/HMI Authors: Roudier, Th.; Malherbe, J. M.; Mirouh, G. M. Bibcode: 2017A&A...598A..99R Altcode: 2016arXiv161102152R Context. As the global magnetic field of the Sun has an activity cycle, one expects to observe some variation of the dynamical properties of the flows visible in the photosphere.
Aims: We investigate the flow field during the solar cycle by analysing SDO/HMI observations of continuum intensity, Doppler velocity and longitudinal magnetic field.
Methods: We first picked data at disk center during 6 yr along the solar cycle with a 48-h time step in order to study the overall evolution of the continuum intensity and magnetic field. Then we focused on thirty 6-h sequences of quiet regions without any remnant of magnetic activity separated by 6 months, in summer and winter, when disk center latitude B0 is close to zero. The horizontal velocity was derived from the local correlation tracking technique over a field of view of 216.4 Mm × 216.4 Mm located at disk center.
Results: Our measurements at disk center show the stability of the flow properties between meso- and supergranular scales along the solar cycle.
Conclusions: The network magnetic field, produced locally at disk center independently from large scale dynamo, together with continuum contrast, vertical and horizontal flows, seem to remain constant during the solar cycle. Title: Investigation of the solar centre-to-limb variation of oxygen and lithium spectral features Authors: Caffau, E.; Malherbe, J. -M.; Steffen, M.; Ludwig, H. -G.; Mott, A. Bibcode: 2017MmSAI..88...45C Altcode: We compare intensity spectra of the Sun observed at different limb angles in the wavelength range covering the forbidden oxygen lines and the lithium resonance feature with line formation computations performed on a CO5BOLD 3D hydrodynamical simulation of the solar atmosphere. Among the prime oxygen abundance indicators, the forbidden line at 630 nm is contaminated with a significant Ni I blend. The availability of observations at different positions on the solar disc allows us to disentangle the contributions of oxygen and nickel and to derive their individual abundances. We derived in the past, from the [OI] line, A(O)=8.73± 0.05 with a nickel abundance of A(Ni)=6.1± 0.04. From the observations here presented, we obtain A(O)=8.71 and A(Ni)=6.09, in excellent agreement with the previous result. For lithium, we investigated the Li doublet at 670.7 nm and compared synthetic spectra of the Li spectra range based on different line-lists available in the literature to the observed data. With these observations, we are still unable to conclude on which is the best line-list to be used for the blending lines. Title: METEOSPACE, solar monitoring and space weather at Calern observatory Authors: Corbard, T.; Malherbe, J. -M.; Crussaire, D.; Morand, F.; Ruty, F.; Biree, L.; Aboudarham, J.; Fuller, N.; Renaud, C.; Meftah, M. Bibcode: 2016sf2a.conf..293C Altcode: METEOSPACE is a new partnership project between the Paris Observatory (OP), the Observatoire de la Côte d'Azur (OCA), the French Air Force and a service company (LUNA technology) for the development and operation of a set of small telescopes Hα / Ca II K / Ca II H / G band to be installed at on the Calern plateau (OCA). The objective is to monitor solar activity for both research and its applications in space weather through continuous optical observations of the dynamic phenomena that are visible in the chromosphere: eruptions, destabilization of the filaments triggering coronal mass ejections and associated Moreton waves. Title: Investigation of the lithium 670.7 nm wavelength range in the solar spectrum Authors: Caffau, Elisabetta; Mott, Alessandro; Harutyunyan, Gohar; Malherbe, Jean-Marie; Steffen, Matthias Bibcode: 2016cosp...41E.281C Altcode: Lithium is a key chemical element, with a chemical evolution that is different from that of most other elements. It is also very fragile, as it is destroyed by nuclear reactions with protons at temperatures higher than about 2.5 million K. According to standard Big Bang nucleosynthesis, only the isotope 7Li is produced in significant amounts, while the primordial abundance of the lighter isotope 6Li is negligible. Lithium is not produced by nucleosynthesis in normal stars, except in peculiar phases of stellar evolution (e.g. in AGB stars and Novae). Lithium may also be formed as a result of flares in the atmospheres of young, active stars. To investigate the history of Li production and depletion in the Galaxy, it is necessary to analyse stars of all ages, including those at solar metallicity. In this case, the spectroscopic determination of the Li abundance is complicated by the presence of other spectral lines overlapping with the Li doublet at 670.7 nm. The correct identification and knowledge of the atomic parameters of these blend lines is critical, especially if the 6LI/7Li isotopic ratio is to be derived. In this investigation, we consider several line lists of the blending components available in the literature and use them to compute synthetic spectra, performing the line formation computations both for the classical 1D Holweger-Mueller model and a CO5BOLD 3D hydrodynamical simulation of the solar atmosphere. The synthetic spectra are then compared to the solar spectrum observed at different limb angles. This allows us to check the quality of existing line lists, to find potentially misidentified blend lines, and to construct an optimized line list for solar-type stars. Title: Relation between trees of fragmenting granules and supergranulation evolution Authors: Roudier, Th.; Malherbe, J. M.; Rieutord, M.; Frank, Z. Bibcode: 2016A&A...590A.121R Altcode: 2016arXiv160404118R Context. The determination of the underlying mechanisms of the magnetic elements diffusion over the solar surface is still a challenge. Understanding the formation and evolution of the solar network (NE) is a challenge, because it provides a magnetic flux over the solar surface comparable to the flux of active regions at solar maximum.
Aims: We investigate the structure and evolution of interior cells of solar supergranulation. From Hinode observations, we explore the motions on solar surface at high spatial and temporal resolution. We derive the main organization of the flows inside supergranules and their effect on the magnetic elements.
Methods: To probe the superganule interior cell, we used the trees of fragmenting granules (TFG) evolution and their relations to horizontal flows.
Results: Evolution of TFG and their mutual interactions result in cumulative effects able to build horizontal coherent flows with longer lifetime than granulation (1 to 2 h) over a scale up to 12''. These flows clearly act on the diffusion of the intranetwork (IN) magnetic elements and also on the location and shape of the network.
Conclusions: From our analysis during 24 h, TFG appear as one of the major elements of the supergranules which diffuse and advect the magnetic field on the Sun's surface. The strongest supergranules contribute the most to magnetic flux diffusion in the solar photosphere.

Movies are available in electronic form at http://www.aanda.org Title: The photospheric solar oxygen project. III. Investigation of the centre-to-limb variation of the 630 nm [O I]-Ni I blend Authors: Caffau, E.; Ludwig, H. -G.; Steffen, M.; Livingston, W.; Bonifacio, P.; Malherbe, J. -M.; Doerr, H. -P.; Schmidt, W. Bibcode: 2015A&A...579A..88C Altcode: 2015arXiv150600931C Context. The solar photospheric abundance of oxygen is still a matter of debate. For about ten years some determinations have favoured a low oxygen abundance which is at variance with the value inferred by helioseismology. Among the oxygen abundance indicators, the forbidden line at 630 nm has often been considered the most reliable even though it is blended with a Ni i line. In Papers I and II of this series we reported a discrepancy in the oxygen abundance derived from the 630 nm and the subordinate [O I] line at 636 nm in dwarf stars, including the Sun.
Aims: Here we analyse several, in part new, solar observations of the centre-to-limb variation of the spectral region including the blend at 630 nm in order to separate the individual contributions of oxygen and nickel.
Methods: We analyse intensity spectra observed at different limb angles in comparison with line formation computations performed on a CO5BOLD 3D hydrodynamical simulation of the solar atmosphere.
Results: The oxygen abundances obtained from the forbidden line at different limb angles are inconsistent if the commonly adopted nickel abundance of 6.25 is assumed in our local thermodynamic equilibrium computations. With a slightly lower nickel abundance, A(Ni) ≈ 6.1, we obtain consistent fits indicating an oxygen abundance of A(O) = 8.73 ± 0.05. At this value the discrepancy with the subordinate oxygen line remains.
Conclusions: The derived value of the oxygen abundance supports the notion of a rather low oxygen abundance in the solar photosphere. However, it is disconcerting that the forbidden oxygen lines at 630 and 636 nm give noticeably different results, and that the nickel abundance derived here from the 630 nm blend is lower than expected from other nickel lines. Title: Families of Granules, Flows, and Acoustic Events in the Solar Atmosphere from Hinode Observations Authors: Malherbe, J. -M.; Roudier, T.; Frank, Z.; Rieutord, M. Bibcode: 2015SoPh..290..321M Altcode: 2014SoPh..tmp..189M We investigate the relationship between trees of fragmenting granules (TFG), horizontal and vertical flows, and acoustic events (AE) in the photospheric network. AE are spatially concentrated and short-duration locations of acoustic energy flux. We performed observations at disk center of a 2D field of view (FOV) with high spatial and temporal resolutions provided by the Solar Optical Telescope onboard Hinode. Line profiles of Fe I 557.6 nm were recorded by the Narrow-band Filter Imager on an 80″×36″ FOV during five hours with a cadence of 22 seconds and 0.08″ pixel size. Vertical velocities were derived at two atmospheric levels allowing the determination of the energy flux at the acoustic frequency of 3.3 mHz. Families of granules and horizontal velocities were obtained from local correlation tracking (LCT) after segmentation and labeling of either continuum intensities or granular Doppler shifts. AE exhibit durations in the range 0.25 to 1 hour compatible with the lifetime of families (80 % do not last more than two hours). High-energy AE have the shortest lifetimes. We found that most AE occur in intergranular lanes located in or close to the boundaries between different families (called inter families) in regions with predominantly downward vertical motions and horizontal converging flows. In contrast, diverging flows are observed inside families, with a few AE in the intergranules. At the beginning of the sequence, when families are not yet detected, the distribution of AE is not uniform and is already organized at spatial lengths related to the mesogranular scale, with maximum contribution in the range 5″ to 10″, fully compatible with the scale of the maximum contribution of families in the TFG space. Although all sizes and durations seem to exist for families, their number decreases with increasing size and lifetime. Title: Time Evolution of Force-Free Parameter and Free Magnetic Energy in Active Region NOAA 10365 Authors: Valori, G.; Romano, P.; Malanushenko, A.; Ermolli, I.; Giorgi, F.; Steed, K.; van Driel-Gesztelyi, L.; Zuccarello, F.; Malherbe, J. -M. Bibcode: 2015SoPh..290..491V Altcode: We describe the variation of the accumulated coronal helicity derived from the magnetic helicity flux through the photosphere in active region (AR) NOAA 10365, where several large flares and coronal mass ejections (CMEs) occurred. We used SOHO/MDI full-disk line-of-sight magnetograms to measure the helicity flux, and the integral of GOES X-ray flux as a proxy of the coronal energy variations due to flares or CMEs. Using the linear force-free field model, we transformed the accumulated helicity flux into a time sequence of the force-free parameter α accounting for flares or CMEs via the proxy derived from GOES observations. This method can be used to derive the value of α at different times during the AR evolution, and is a partial alternative to the commonly used match of field lines with EUV loops. By combining the accumulated helicity obtained from the observations with the linear force-free theory, we describe the main phases of the emergence process of the AR, and relate them temporally with the occurrence of flares or CMEs. Additionally, a comparison with the loop-matching method of fixing alpha at each time independently shows that the proposed method may be helpful in avoiding unrealistic or undetermined values of alpha that may originate from an insufficient quality of the image used to identify coronal loops at a given time. For the relative intensity of the considered events, the linear force-free field theory implies that there is a direct correlation between the released energy on the one hand and the product of the coronal helicity with the variation of α due to the event on the other. Therefore, the higher the value of the accumulated coronal helicity, the smaller the force-free parameter variation required to produce the same decrease in the free energy during the CMEs. Title: Optical characterization of the breadboard narrowband prefilters for Solar Orbiter PHI Authors: Dominguez-Tagle, Carlos; Appourchaux, Thierry; Ruiz de Galarreta, Claudia; Fourmond, Jean-Jacques; Philippon, Anne; Le Clec'h, Jean-Christophe; Bouzit, Mehdi; Bommier, Véronique; Le Cocguen, Regis; Crussaire, Daniel; Malherbe, Jean-Marie Bibcode: 2014SPIE.9143E..5GD Altcode: The Polarimetric and Helioseismic Imager (PHI) on board of Solar Orbiter will observe the Sun to measure the photospheric vector magnetic field and the line-of-sight velocity. It will employ a narrowband filtergraph (FG) to scan the FeI 6173 Å absorption line. At different spectral positions, the polarization state of the incoming light will be analyzed. The FG will provide a tuning range to scan the line, the continuum, and to compensate for the spacecraft radial velocity, as it will approach to the Sun down to 0.28 AU. The FG includes a Fabry-Perot etalon and two narrowband prefilters. The bandpass of the narrowest one has a nominal Full Width at Half Maximum (FWHM) of 2.7 Å. The measurement of the prefilters characteristics is essential for the instrument calibration. Here we present the results of the breadboard prefilters characterization, which is an important milestone in the development of the instrument. Title: The S4I prototype, a beam-slicer dedicated to the new generation Multichannel Subtractive Double Pass for EST imaging spectropolarimetry Authors: Sayède, Frédéric; Mein, Pierre; Malherbe, Jean-Marie; Amans, Jean-Philippe; Crussaire, Daniel; Lecocguen, Regis Bibcode: 2014SPIE.9147E..6FS Altcode: For the future European Solar Telescope (EST) the Observatoire de Paris proposes a new generation of MSDP, an imaging spectro-polarimetry instrument. To validate this new generation, we develop a plane micro-mirrors beam slicer prototype that is tested and validated on an optical bench and on existing telescopes. The prototype called S4I (Spectral Sampling with Slicer for Solar Instrumentation) is built and tested at the Observatoire de Paris. It validates the opto-mechanical feasibility of the new beam slicer. After a complete description of the system, we present the first images. We evaluate the performances of the prototype and compare them to the requirements for the beam-slicer dedicated to the future EST. Title: S4EI (Spectral Sampling with Slicer for Stellar and Extragalactical Instrumentation), a new-generation of 3D spectro-imager dedicated to night astronomy Authors: Sayède, Frédéric; Puech, Mathieu; Mein, Pierre; Bonifacio, Piercarlo; Malherbe, Jean-Marie; Galicher, Raphaël.; Amans, Jean-Philippe; Fasola, Gilles Bibcode: 2014SPIE.9147E..3OS Altcode: Multichannel Subtractive Double Pass (MSDP) spectrographs have been widely used in solar spectroscopy because of their ability to provide an excellent compromise between field of view and spatial and spectral resolutions. Compared with other types of spectrographs, MSDP can deliver simultaneous monochromatic images at higher spatial and spectral resolutions without any time-scanning requirement (as with Fabry-Perot spectrographs), and with limited loss of flux. These performances are obtained thanks to a double pass through the dispersive element. Recent advances with VPH (Volume phase holographic) Grisms as well as with image slicers now make MSDP potentially sensitive to much smaller fluxes. We present S4EI (Spectral Sampling with Slicer for Stellar and Extragalactical Instrumentation), which is a new concept for extending MSDP to night-time astronomy. It is based on new generation reflecting plane image slicers working with large apertures specific to night-time telescopes. The resulting design could be potentially very attractive and innovative for different domains of astronomy, e.g., the simultaneous spatial mapping of accurately flux-calibrated emission lines between OH sky lines in extragalactic astronomy or the simultaneous imaging of stars, exoplanets and interstellar medium. We present different possible MSDP/S4EI configurations for these science cases and expected performances on telescopes such as the VLT. Title: Structure and evolution of solar supergranulation using SDO/HMI data Authors: Roudier, Th.; Švanda, M.; Rieutord, , M.; Malherbe, J. M.; Burston, R.; Gizon, L. Bibcode: 2014A&A...567A.138R Altcode: 2014arXiv1407.0196R Context. Studying the motions on the solar surface is fundamental for understanding how turbulent convection transports energy and how magnetic fields are distributed across the solar surface.
Aims: From horizontal velocity measurements all over the visible disc of the Sun and using data from the Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI), we investigate the structure and evolution of solar supergranulation.
Methods: Horizontal velocity fields were measured by following the proper motions of solar granules using a newly developed version of the coherent structure tracking code. With this tool, maps of horizontal divergence were computed. We then segmented and identified supergranular cells and followed their histories by using spatio-temporal labelling. With this data set we derived the fundamental properties of supergranulation, including their motion.
Results: We find values of the fundamental parameters of supergranulation similar to previous studies: a mean lifetime of 1.5 days and a mean diameter of 25 Mm. The tracking of individual supergranular cells reveals the solar differential rotation and a poleward circulation trend of the meridional flow. The shape of the derived differential rotation and meridional flow does not depend on the cell size. If there is a background magnetic field, the diverging flows in supergranules are weaker.
Conclusions: This study confirms that supergranules are suitable tracers that may be used to investigate the large-scale flows of the solar convection as long as they are detectable enough on the surface. Title: Coronal Magnetic Reconnection Driven by CME Expansion—the 2011 June 7 Event Authors: van Driel-Gesztelyi, L.; Baker, D.; Török, T.; Pariat, E.; Green, L. M.; Williams, D. R.; Carlyle, J.; Valori, G.; Démoulin, P.; Kliem, B.; Long, D. M.; Matthews, S. A.; Malherbe, J. -M. Bibcode: 2014ApJ...788...85V Altcode: 2014arXiv1406.3153V Coronal mass ejections (CMEs) erupt and expand in a magnetically structured solar corona. Various indirect observational pieces of evidence have shown that the magnetic field of CMEs reconnects with surrounding magnetic fields, forming, e.g., dimming regions distant from the CME source regions. Analyzing Solar Dynamics Observatory (SDO) observations of the eruption from AR 11226 on 2011 June 7, we present the first direct evidence of coronal magnetic reconnection between the fields of two adjacent active regions during a CME. The observations are presented jointly with a data-constrained numerical simulation, demonstrating the formation/intensification of current sheets along a hyperbolic flux tube at the interface between the CME and the neighboring AR 11227. Reconnection resulted in the formation of new magnetic connections between the erupting magnetic structure from AR 11226 and the neighboring active region AR 11227 about 200 Mm from the eruption site. The onset of reconnection first becomes apparent in the SDO/AIA images when filament plasma, originally contained within the erupting flux rope, is redirected toward remote areas in AR 11227, tracing the change of large-scale magnetic connectivity. The location of the coronal reconnection region becomes bright and directly observable at SDO/AIA wavelengths, owing to the presence of down-flowing cool, dense (1010 cm-3) filament plasma in its vicinity. The high-density plasma around the reconnection region is heated to coronal temperatures, presumably by slow-mode shocks and Coulomb collisions. These results provide the first direct observational evidence that CMEs reconnect with surrounding magnetic structures, leading to a large-scale reconfiguration of the coronal magnetic field. 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: 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: 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: Magnetic reconnection driven by filament eruption in the 7 June 2011 event Authors: van Driel-Gesztelyi, L.; Baker, D.; Török, T.; Pariat, E.; Green, L. M.; Williams, D. R.; Carlyle, J.; Valori, G.; Démoulin, P.; Matthews, S. A.; Kliem, B.; Malherbe, J. -M. Bibcode: 2014IAUS..300..502V Altcode: During an unusually massive filament eruption on 7 June 2011, SDO/AIA imaged for the first time significant EUV emission around a magnetic reconnection region in the solar corona. The reconnection occurred between magnetic fields of the laterally expanding CME and a neighbouring active region. A pre-existing quasi-separatrix layer was activated in the process. This scenario is supported by data-constrained numerical simulations of the eruption. Observations show that dense cool filament plasma was re-directed and heated in situ, producing coronal-temperature emission around the reconnection region. These results provide the first direct observational evidence, supported by MHD simulations and magnetic modelling, that a large-scale re-configuration of the coronal magnetic field takes place during solar eruptions via the process of magnetic reconnection. Title: The photospheric solar oxygen project. II. Non-concordance of the oxygen abundance derived from two forbidden lines Authors: Caffau, E.; Ludwig, H. -G.; Malherbe, J. -M.; Bonifacio, P.; Steffen, M.; Monaco, L. Bibcode: 2013A&A...554A.126C Altcode: 2013arXiv1305.1763C Context. In the Sun, the two forbidden [O i] lines at 630 and 636 nm were previously found to provide discrepant oxygen abundances.
Aims: We investigate whether this discrepancy is peculiar to the Sun or whether it is also observed in other stars.
Methods: We make use of high-resolution, high signal-to-noise ratio spectra of four dwarf to turn-off stars, five giant stars, and one sub-giant star observed with THEMIS, HARPS, and UVES to investigate the coherence of the two lines.
Results: The two lines provide oxygen abundances that are consistent, within observational errors, in all the giant stars examined by us. On the other hand, for the two dwarf stars for which a measurement was possible, for Procyon, and for the sub-giant star Capella, the 636 nm line provides systematically higher oxygen abundances, as already seen for the Sun.
Conclusions: The only two possible reasons for the discrepancy are a serious error in the oscillator strength of the Ni i line blending the 630 nm line or the presence of an unknown blend in the 636 nm line, which makes the feature stronger. The CN lines blending the 636 nm line cannot be responsible for the discrepancy. The Ca i autoionisation line, on the red wing of which the 636 nm line is formed, is not well modelled by our synthetic spectra. However, a better reproduction of this line would result in even higher abundances from the 636 nm, thus increasing the discrepancy.

Based on observations collected at ESO Paranal Observatory, Programme 182.D-5053(A). Title: Comparison of solar horizontal velocity fields from SDO/HMI and Hinode data Authors: Roudier, Th.; Rieutord, M.; Prat, V.; Malherbe, J. M.; Renon, N.; Frank, Z.; Švanda, M.; Berger, T.; Burston, R.; Gizon, L. Bibcode: 2013A&A...552A.113R Altcode: 2013arXiv1303.4271R Context. The measurement of the Sun's surface motions with a high spatial and temporal resolution is still a challenge.
Aims: We wish to validate horizontal velocity measurements all over the visible disk of the Sun from Solar Dynamics Observatory/ Helioseismic and Magnetic Imager (SDO/HMI) data.
Methods: Horizontal velocity fields are measured by following the proper motions of solar granules using a newly developed version of the coherent structure tracking (CST) code. The comparison of the surface flows measured at high spatial resolution (Hinode, 0.1 arcsec) and low resolution (SDO/HMI, 0.5 arcsec) allows us to determine corrections to be applied to the horizontal velocity measured from HMI white light data.
Results: We derive horizontal velocity maps with spatial and temporal resolutions of respectively 2.5 Mm and 30 min. From the two components of the horizontal velocity vx and vy measured in the sky plane and the simultaneous line of sight component from SDO/HMI dopplergrams vD, we derive the spherical velocity components (vr, vθ, vϕ). The azimuthal component vϕ gives the solar differential rotation with a high precision (± 0.037 km s-1) from a temporal sequence of only three hours.
Conclusions: By following the proper motions of the solar granules, we can revisit the dynamics of the solar surface at high spatial and temporal resolutions from hours to months and years with the SDO data. Title: The Power Spectrum of the Solar Surface Flows from Hinode Data and First Observations with MOF/CALAS Pic-du-Midi Authors: Roudier, T.; Rieutord, M.; Rincon, F.; Malherbe, J. -M.; Brito, D.; Berger, T.; Frank, Z.; Parés, L.; Bourrec, E.; Beigbeder, F. Bibcode: 2012ASPC..454...47R Altcode: Many features of solar surface turbulence, like the supergranulation, are still poorly understood.We use long time series of images taken by the Solar Optical Telescope on board the Hinode satellite to determine the velocity fields. The dynamics in the subgranulation range can be investigated with unprecedented precision thanks to the absence of seeing effects and the use of the MTF of SOT for correcting the spectra. The first MOF/CALAS/Pic-du-Midi results are also shown. Title: Acoustic Events in the Solar Atmosphere from Hinode/SOT NFI Observations Authors: Malherbe, J. -M.; Roudier, T.; Rieutord, M.; Berger, T.; Franck, Z. Bibcode: 2012SoPh..278..241M Altcode: 2012arXiv1207.1170M We investigate the properties of acoustic events (AEs), defined as spatially concentrated and short duration energy flux, in the quiet Sun, using observations of a 2D field of view (FOV) with high spatial and temporal resolution provided by the Solar Optical Telescope (SOT) onboard Hinode. Line profiles of Fe I 557.6 nm were recorded by the Narrow-band Filter Imager (NFI) on a 82″×82″ FOV during 75 min with a time step of 28.75 s and 0.08″ pixel size. Vertical velocities were computed at three atmospheric levels (80, 130, and 180 km) using the bisector technique, allowing the determination of energy flux to be made in the range 3 - 10 mHz using two complementary methods (Hilbert transform and Fourier power spectrum). Horizontal velocities were computed using local correlation tracking (LCT) of continuum intensities providing divergences. We found that the net energy flux is upward. In the range 3 - 10 mHz, a full FOV space and time averaged flux of 2700 W m−2 (lower layer 80 - 130 km) and 2000 W m−2 (upper layer 130 - 180 km) is concentrated in less than 1 % of the solar surface in the form of narrow (0.3″) AE. Their total duration (including rise and decay) is of the order of 103 s. Inside each AE, the mean flux is 1.6×105 W m−2 (lower layer) and 1.2×105 W m−2 (upper). Each event carries an average energy (flux integrated over space and time) of 2.5×1019 J (lower layer) to 1.9×1019 J (upper). More than 106 events could exist permanently on the Sun, with a birth and decay rate of 3500 s−1. Most events occur in intergranular lanes, downward velocity regions, and areas of converging motions. Title: Some Dynamic Analysis of the Photosphere from Hinode/SOT and SDO/HMI Observations Authors: Roudier, T.; Malherbe, J.; Rieutord, M.; Berger, T.; Frank, Z.; Prat, V.; Renon, N.; Gizon, L.; Svanda, M. Bibcode: 2012ASPC..456...65R Altcode: We first present the important role played by the families of granule (or Tree of Fragmenting granules) in the formation of the photospheric network. Then, we describe the occurence and characteristics of acoustic events (AE), defined as spatially concentrated energy flux, in the quiet Sun. Finally, we present how horizontal velocities obtained from SDO/HMI data are calibrated by using Hinode/SOT observations. Title: Quasi full-disk maps of solar horizontal velocities using SDO/HMI data Authors: Roudier, Th.; Rieutord, M.; Malherbe, J. M.; Renon, N.; Berger, T.; Frank, Z.; Prat, V.; Gizon, L.; Švanda, M. Bibcode: 2012A&A...540A..88R Altcode: 2012arXiv1203.0514R
Aims: For the first time, the motion of granules (solar plasma on the surface on scales larger than 2.5 Mm) has been followed over the entire visible surface of the Sun, using SDO/HMI white-light data.
Methods: Horizontal velocity fields are derived from image correlation tracking using a new version of the coherent structure tracking algorithm. The spatial and temporal resolutions of the horizontal velocity map are 2.5 Mm and 30 min, respectively.
Results: From this reconstruction, using the multi-resolution analysis, one can obtain to the velocity field at different scales with its derivatives such as the horizontal divergence or the vertical component of the vorticity. The intrinsic error on the velocity is ~0.25 km s-1 for a time sequence of 30 min and a mesh size of 2.5 Mm. This is acceptable compared to the granule velocities, which range between 0.3 km s-1 and 1.8 km s-1. A high correlation between velocities computed from Hinode and SDO/HMI has been found (85%). From the data we derive the power spectrum of the supergranulation horizontal velocity field, the solar differential rotation, and the meridional velocity. Title: On the power spectrum of solar surface flows Authors: Rieutord, M.; Roudier, T.; Rincon, F.; Malherbe, J. -M.; Meunier, N.; Berger, T.; Frank, Z. Bibcode: 2010A&A...512A...4R Altcode: 2009arXiv0911.3319R Context. The surface of the Sun provides us with a unique and very detailed view of turbulent stellar convection. Studying its dynamics can therefore help us make significant progress in stellar convection modelling. Many features of solar surface turbulence like the supergranulation are still poorly understood.
Aims: The aim of this work is to give new observational constraints on these flows by determining the horizontal scale dependence of the velocity and intensity fields, as represented by their power spectra, and to offer some theoretical guidelines to interpret these spectra.
Methods: We use long time-series of images taken by the Solar Optical Telescope (SOT) on board the Hinode satellite; we reconstruct both horizontal (by granule tracking) and vertical (by Doppler effect) velocity fields in a field-of-view of ~ 75 × 75 Mm2. The dynamics in the subgranulation range can be investigated with unprecedented precision thanks to the absence of seeing effects and the use of the modulation transfer function of SOT for correcting the spectra.
Results: At small subgranulation scales down to 0.4 Mm the spectral density of kinetic energy associated with vertical motions exhibits a k-10/3-like power law, while the intensity fluctuation spectrum follows either a k-17/3 or a k-3-like power law at the two continuum levels investigated (525 and 450 nm respectively). We discuss the possible physical origin of these scalings and interpret the combined presence of k-17/3 and k-10/3 power laws for the intensity and vertical velocity as a signature of buoyancy-driven turbulent dynamics in a strongly thermally diffusive regime. In the mesogranulation range and up to a scale of 25 Mm, we find that the amplitude of the vertical velocity field decreases like λ-3/2 with the horizontal scale λ. This behaviour corresponds to a k2 spectral power law. Still in the 2.5-10 Mm mesoscale range, we find that intensity fluctuations in the blue continuum also follow a k2 power law. In passing we show that granule tracking cannot sample scales below 2.5 Mm. We finally further confirm the presence of a significant supergranulation energy peak at 30 Mm in the horizontal velocity power spectrum and show that the emergence of a pore erases this spectral peak. We tentatively estimate the scale height of the vertical velocity field in the supergranulation range and find 1 Mm; this value suggests that supergranulation flows are shallow. 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: Supergranulation, Network Formation, and TFGs Evolution from Hinode Observations Authors: Roudier, T.; Rincon, F.; Rieutord, M.; Brito, D.; Beigbeder, F.; Parès, L.; Malherbe, J. -M.; Meunier, N.; Berger, T.; Frank, Z. Bibcode: 2009ASPC..415..203R Altcode: In this paper, we analyse a a 48h high-resolution time sequence of the quiet Sun photosphere obtained with the Solar Optical Telescope onboard Hinode. Using floating corks advected by velocity fields inferred from photometry measurements, we show that long-living Trees of Fragmenting Granules play a crucial role in the advection of small-scale magnetic fields and in the build-up of the magnetic network. 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: Mesoscale dynamics on the Sun's surface from HINODE observations Authors: Roudier, Th.; Rieutord, M.; Brito, D.; Rincon, F.; Malherbe, J. M.; Meunier, N.; Berger, T.; Frank, Z. Bibcode: 2009A&A...495..945R Altcode: 2009arXiv0902.2299R Context:
Aims: The interactions of velocity scales on the Sun's surface, from granulation to supergranulation are still not understood, nor are their interaction with magnetic fields. We thus aim at giving a better description of dynamics in the mesoscale range which lies between the two scales mentioned above.
Methods: We analyse a 48 h high-resolution time sequence of the quiet Sun photosphere at the disk center obtained with the Solar Optical Telescope onboard Hinode. The observations, which have a field of view of 100´´ × 100´´, typically contain four supergranules. We monitor in detail the motion and evolution of granules as well as those of the radial magnetic field.
Results: This analysis allows us to better characterize Trees of Fragmenting Granules issued from repeated fragmentation of granules, especially their lifetime statistics. Using floating corks advected by measured velocity fields, we show their crucial role in the advection of the magnetic field and in the build up of the network. Finally, thanks to the long duration of the time series, we estimate that the turbulent diffusion coefficient induced by horizontal motion is approximately 430 km2 s-1.
Conclusions: These results demonstrate that the long living families contribute to the formation of the magnetic network and suggest that supergranulation could be an emergent length scale building up as small magnetic elements are advected and concentrated by TFG flows. Our estimate for the magnetic diffusion associated with this horizontal motion might provide a useful input for mean-field dynamo models. 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: 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: Turbulent fields in the quiet sun from Hanle and Zeeman effects with THEMIS Authors: López Ariste, A.; Malherbe, J. M.; Manso Sainz, R.; Asensio Ramos, A.; Ramírez Vélez, J. C.; Martínez González, M. Bibcode: 2007sf2a.conf..596L Altcode: The measurement of the Sr I line with full polarimetry and spatial resolution with THEMIS has provided the unexpected result of an apparent correlation between the Hanle effect signals and the Zeeman effect signals on this line. Traditionnally, Hanle effect signals in linear polarisation have been interpreted as the signature of unorganized, turbulent fields, while Zeeman effect signals -mostly in circular polarisation- were interpreted as structured fields. The correlation between both observed by THEMIS requires a change of mind respect to the picture of the quiet sun, with fewer structured fields and a turbulent field visible also in deep magnetograms. This picture is supported also by recent results with Mn lines with strong coupling with its hyperfine structure and of center-to-limb histograms of Zeeman amplitudes. Title: Resonance polarization of the solar 455.4 nm BaII line: diagnostics of chromospheric magnetic fields Authors: Michel, C.; Faurobert, M.; Arnaud, J.; Malherbe, J. M. Bibcode: 2007sf2a.conf..607M Altcode: The BaII resonance line at 455.4 nm is formed in the low solar chromopshere. It is significantly linearly polarized outside active regions and close to the solar limb. This so-called resonance polarization is sensitive to the Hanle effect of weak magnetic fields. We report on numerical simulations of the intensity and resonance polarization profiles in the line and in the adjacent continuum, in the quiet solar atmosphere and we compare them to observations performed at the Jean Rosch refractor at the Pic du Midi Observatory. In the simulations we take into account non-LTE multilevel coupling, multiple scattering and partial frequency redistribution, and we neglect the hyperfine structure of the odd isotopes. This allows to model the central part of the line core and the wings quite well. Then we investigate the diagnostic potential of the line core polarization for weak unresolved magnetic fields in the low chromosphere. We find that the observed polarization rates are in good agreement with the simulations if we take into account the Hanle effect of weak magnetic fields on the order of 60 to 75 Gauss. 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: Magnetic flux tubes observed with THEMIS/MSDP Authors: Mein, P.; Mein, N.; Faurobert, M.; Aulanier, G.; Malherbe, J. -M. Bibcode: 2007A&A...463..727M Altcode: Aims:We use spectro-polarimetric THEMIS/MSDP data to investigate the 3D structure of solar magnetic-flux tubes across the upper photosphere.
Methods: Profiles of the sodium D1 line 589.6 nm are analysed by the bisector method at different wavelengths from the core to the wings, for several bright features. They are compared to synthetic profiles derived from 2D magnetic models of flux tubes and from the MULTI code for NLTE line profiles. Three different magnetic models of flux tubes are investigated. Model (I) consists of a single flux tube that compensates for the horizontal Lorentz forces exactly, while model (II) uses a compromise between horizontal and vertical components. Model (III), a conglomerate of thinner flux tubes, leads to the best agreement with observations.
Results: (1) The combination of seeing effects (small filling factor) with slopes of line profiles, which are different in the flux tubes and the neighbouring quiet sun, account for the decrease in observed magnetic field from line core to line wings in central parts of magnetic features, as well as the decrease in magnetic fluxes integrated over the whole magnetic features. (2) The expansion with height of single magnetic flux tubes (models I and II) accounts for the increase in the size of magnetic features from line wings to line core. (3) Pure thermodynamical criteria characterising Dopplershifts and line-intensity fluctuations of magnetic and non-magnetic features have been proven by observations.
Conclusions: . We could account for differential Zeeman effects along the D1 line profile by combining expansion of flux tubes with height, low gas pressure inside flux tubes, and small filling factor due to seeing effects. Better agreement with observations, in particular with respect to magnetic field amplitudes, will probably need 3D models that take velocity fields and horizontal gradients of temperature into account. Title: First observations of the second solar spectrum with spatial resolution at the Lunette Jean Rösch Authors: Malherbe, J. -M.; Moity, J.; Arnaud, J.; Roudier, Th. Bibcode: 2007A&A...462..753M Altcode: Context: A new polarimeter has been installed at the focus of the 50 cm refractor of the Lunette Jean Rösch (LJR), previously known as Turret Dome, Pic du Midi, France, for spectroscopic observations of weak solar magnetic fields. Fields can be derived through the Hanle effect from the depolarization of the second solar spectrum (i.e. the linearly polarized spectrum at the limb).
Aims: We present the first observations with spatial resolution based on the new device performed with the large 8 m Echelle spectrograph, or recorded in imagery mode through narrow band filters. The observations started in April 2004, especially in the blue part of the spectrum where our instrumentation has a particularly good efficiency. The capabilities and the characteristics of the new instrument are briefly described. We observed several lines of the second solar spectrum with the slit of the spectrograph orthogonal to the limb to study the polarization as a function of limb distance (which is related to altitude in the atmosphere), and several spectral windows in imagery to determine the average continuum polarization.
Methods: The polarimeter uses Nematic Liquid Crystal (NLC) technology at the primary focus of the refractor, in spectroscopic or imagery mode.
Results: A continuous polarization profile through the limb is presented for the photospheric SrI 460.7 nm line, the low chromospheric BaII 455.4 nm line, and the CaI 422.7 nm line within a distance of 120´´, together with measurements of the mean continuum polarization obtained in imagery mode. Preliminary results of the polarization of the SrI 460.7 nm line are also shown at 40´´ from the limb, as a function of the brightness of structures visible in the continuum (granulation). They reveal a tendency for the polarization to be weaker in dark features (intergranules) than in bright ones (granules), suggesting a stronger magnetic field in intergranular lanes. As example the enigmatic and weak polarization signal in the core of the NaD1 589.6 nm line is presented.
Conclusions: .Some aspects of the spatial variation of the polarization with respect to the granulation pattern require further investigation at higher spatial resolution.

Appendices A-C are only available in elctronic form at http://www.aanda.org Title: Magnetic flux tubes observed with THEMIS/MSDP . Authors: Mein, P.; Mein, N.; Faurobert, M.; Aulanier, G.; Malherbe, J. -M. Bibcode: 2007MmSAI..78...92M Altcode: We use 2D spectro-polarimetric data of the NaD1 line to investigate magnetic flux tubes at several levels of the solar photosphere:

- magnetic and non-magnetic bright features can be discriminated by simple criteria of intensities and dopplershifts.

- 2D magnetic models and NLTE line profiles are compared to observations : combination of seeing effects and departures between slopes of line profiles in flux tubes and neighbouring photosphere account for vertical gradients of line-of-sight (LOS) magnetic field measurements.

- Best qualitative agreements are obtained with clusters of magnetic flux tubes. 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: Spectro polarimetry with liquid crystals . Authors: Malherbe, J. -M.; Roudier, Th.; Moity, J.; Mein, P.; Arnaud, J.; Muller, R. Bibcode: 2007MmSAI..78..203M Altcode: We report spectro polarimetric observations made with the spectrograph of the Lunette Jean Rösch at Pic du Midi, France. We have tested Ferroelectric (FLC) and Nematic (NLC) Liquid Crystals. The instrument setup is briefly decribed, together with first observations of magnetic fields obtained with the Multichannel Subtractive Double Pass (MSDP). Polarization analysis of various spectral lines performed with the single pass (SP) spectrograph in active regions or at the limb is also presented. Title: Interpretation of the Second Solar Spectrum of the Sr I 4607 Å Line Observed at THEMIS and Pic-du-Midi Authors: Derouich, M.; Bommier, V.; Malherbe, J. -M.; Landi Degl'Innocenti, E.; Molodij, G.; Sahal-Bréchot, S. Bibcode: 2006ASPC..358..120D Altcode: The Hanle effect is the only tool available for measuring turbulent (i.e., spatially unresolved) magnetic fields at the surface of the quiet Sun. The Hanle-effect diagnostics relies on the discrepancy between the linear polarization calculated in the absence of a magnetic field and the observed polarization. We interpreted the linear polarization of the Sr I 4607 Å line, observed at THEMIS (December 7-9, 2002) and Pic-du-Midi (May 14, 2004), in terms of the Hanle effect. We present here the main results of this study. In particular, we stress the importance of a proper adjustment of the theoretical intensity profile to the observed one, through the application of a zero-field model, the magnetic field being determined in a second step from the line-center polarization degree. With the spatial resolution

and coverage of the Pic-du-Midi data (1 arcsec resolution, 132 distances from the limb), we can also attain depth probing of the turbulent magnetic strength, and we discuss whether this can vary within the range of heights of formation for the line center. Title: Second solar spectrum of the Sr I 4607 Å line: depth probing of the turbulent magnetic field strength in a quiet region Authors: Derouich, M.; Bommier, V.; Malherbe, J. M.; Landi Degl'Innocenti, E. Bibcode: 2006A&A...457.1047D Altcode: Aims.This paper is devoted to an interpretation of Quiet-Sun, spatially-resolved spectropolarimetric observations of the Hanle effect in terms of turbulent weak magnetic field determination.
Methods: . Observations: the slit was positioned perpendicular to the limb, and the spatial resolution along the slit was 1 arcsec, leading to a depth probing along 132 different limb distances. The new polarimeter of the Pic-du-Midi Turret Dome was used on May 14, 2004 to observe a quiet region at the East limb equator in the resonance line of neutral Strontium at 4607 Å.
Results: . For each limb distance, we properly adjusted the theoretical intensity profile obtained by applying a zero-field model to the observed one. Micro- and macroturbulent velocities were thus derived (average values v{micro}=1.77 km s-1 and v{macro}=1.95 km s-1). The magnetic field was determined in a second step by interpreting the Hanle effect on the line center linear polarization degree. The depolarizing collisions with neutral hydrogen were taken fully into account through a semi-classical calculation of their rates. An average value of B=38 Gauss was thus derived. Finally, error bars on the magnetic field values were evaluated from a) the polarimetric inaccuracy, b) the limb distance determination inaccuracy, and c) the uncertainty on our theoretical collisional depolarizing rates that we evaluated. This combination leads to 10-20% as total relative error on the magnetic field determination by the Hanle effect method. Since the inaccuracy due to the model itself was hard to properly evaluate, it was ignored. An uncertainty of ±60 km on the line formation depth was, however, derived from the contribution functions. The magnetic field is found to increase slowly with height in the height range 220-300 km above τ5000=1 and then decrease in the height range 300-370 km.
Title: Sub arcsec evolution of solar magnetic fields Authors: Roudier, Th.; Malherbe, J. M.; Moity, J.; Rondi, S.; Mein, P.; Coutard, Ch. Bibcode: 2006A&A...455.1091R Altcode: Context: .The evolution of the concentrated magnetic field in flux tubes is one challenge of the nowadays Solar physics which requires time sequence with high spatial resolution.
Aims: .Our objective is to follow the properties of the magnetic concentrations during their life, in intensity (continuum and line core), magnetic field and Doppler velocity.
Methods: .We have observed solar region NOAA 0644 on 2004 July 15 at Pic du Midi observatory with the Multichannel Subtractive Double Pass (MSDP) operating mode and analysed the circular polarization of the Na D1 589.6 nm spectral line in terms of longitudinal magnetic field in 2D field of view (5.6 arcsec× 80 arcsec), during 41 mn at two altitudes 327 km and 170 km in the photosphere.
Results: .Our data analysis reveals that all the concentrated magnetic features are associated with downward motions and the magnetic field remains very stable during the 41 mn. At different height 327 and 170 km, a clear depth effect is visible on Doppler velocity but not in the magnetic field strength.
Title: The Lyman Alpha Imaging-Monitor Experiment (LAIME) for TESIS/CORONAS-PHOTON Authors: Damé, L.; Koutchmy, S.; Kuzin, S.; Lamy, P.; Malherbe, J. -M.; Noëns, J. -C. Bibcode: 2006cosp...36.3524D Altcode: 2006cosp.meet.3524D LAIME the Lyman Alpha Imaging-Monitor Experiment is a remarkably simple no mechanisms and compact 100x100x400 mm full Sun imager to be flown with TESIS on the CORONAS-PHOTON mission launch expected before mid-2008 As such it will be the only true chromospheric imager to be flown in the next years supporting TESIS EUV-XUV imaging SDO and the Belgian LYRA Lyman Alpha flux monitor on the ESA PROBA-2 microsatellite launch expected in September 2007 We will give a short description of this unique O60 mm aperture imaging telescope dedicated to the investigating of the magnetic sources of solar variability in the UV and chromospheric and coronal disruptive events rapid waves Moreton waves disparitions brusques of prominences filaments eruptions and CMEs onset The resolution pixel is 2 7 arcsec the field of view 1 4 solar radius and the acquisition cadence could be as high as 1 image minute The back thinned E2V CCD in the focal plane is using frame transfer to avoid shutter and mechanisms Further more the double Lyman Alpha filtering allows a 40 AA FWHM bandwidth and excellent rejection yet providing a vacuum seal design of the telescope MgF2 entrance window Structural stability of the telescope focal length 1 m is preserved by a 4-INVAR bars design with Aluminium compensation in a large pm 10 o around 20 o Title: On the Disk Hα and Radio Observations of the 2003 October 28 Flare and Coronal Mass Ejection Event Authors: Pick, Monique; Malherbe, Jean-Marie; Kerdraon, Alain; Maia, Dalmiro Jorge Filipe Bibcode: 2005ApJ...631L..97P Altcode: We present the evolution of the Hα and radio emissions seen by the Meudon Hα telescope and the Nançay radioheliograph, which are associated with the X17.2 flare and halo CME of 2003 October 28. The remarkable characteristic of this event is its spatial extent that it reached in a few minutes. At 164 MHz, radio images show that the emission covers the whole disk of the Sun and extends as far as 1.8 Rsolar from the Sun's center. The radio emissions, the Moreton wave seen in Hα, and the CME all show a similar temporal and spatial development, and the three phenomena are likely to be related. We show that multifrequency radio imaging observations obtained at high cadence can accurately visualize the initial on-the-disk development of fast halo CMEs and also provide physical parameters such as their speed and angular expansion. Title: Research on a complex CME event including Hα, LASCO, radio and MDI observations Authors: Wang, S. J.; Maia, D.; Pick, M.; Aulanier, G.; Malherbe, J. -M.; Delaboudinière, J. -P. Bibcode: 2005AdSpR..36.2273W Altcode: We present our research on a fast and decelerating partial halo coronal mass ejection (CME) event detected in multi-wavelengths in the chromosphere and the corona on 14 October, 1999. The event involved a whole complex active area which spanned more than 40° of heliolongitude. It included a strong solar flare (XI/1N) and a complex eruptive filament within an active region of the entire complex. Especially, several radio sources were detected in the decimetric range prior to the CME by the Nançay Radioheliograph (NRH). A linear force-free field extrapolation of the Michelson Doppler Imager (MDI) magnetogram was performed to calculate the magnetic topology of the complex prior to the triggering of the event. The presence of a coronal null point combined with the occurrence of two distant and nearly simultaneous radio sources put strong arguments in favor of the generalized breakout model for the triggering of the eruption. The analysis of the subsequent development of the event suggests that large interconnecting loops were ejected together with the CME. Title: Second solar spectrum observed at the Pic-du-Midi: depth probing of the turbulent magnetic field intensity in a quiet region. Authors: Derouich, M.; Malherbe, J. M.; Bommier, V.; Landi Degl'Innocenti, E.; Sahal-Bréchot, S. Bibcode: 2004sf2a.conf..113D Altcode: 2004sf2a.confE.346D The installation of a new polarimeter at the Turret Dome of the Pic-du-Midi has permitted new observations of the "second solar spectrum" (which is the spectrum of the linear polarization observed near the solar limb), having a spatial resolution. On 2003 October 25, we have observed a quiet region located at the East limb equator, in the resonance line of neutral strontium at 4607 Å. The slit was positioned perpendicular to the limb: recording various limb distances provides a depth probing of the solar atmosphere. The intensity of the turbulent magnetic field has been derived from the Hanle effect interpretation, which is actually the only method for vectorial weak field determination. The theoretical profiles to be compared to the observed ones have been obtained by applying the atomic density matrix formalism (Landi Degl'Innocenti E., Bommier V., & Sahal-Bréchot S., 1990). The various collisional coefficients have been computed by applying semi-classical methods that are accurate to 20% or better: the one from Seaton (1962) and Sahal-Bréchot (1969a, 1969b) for the collisions with electrons, responsible for the inelastic transitions, and the one developed by Anstee & O'Mara (1991, 1995) for line broadening computations, generalized to the collisional depolarization by Derouich et al. (2003; see also Derouich, 2004), for the elastic collisions with neutral hydrogen atoms. The results have been found in full agreement with those previously obtained with THEMIS without any spatial resolution (at 9 limb distances). With the spatial resolution that we have now at the Pic-du-Midi (1 arcsec, 138 limb distances), it appears that the turbulent magnetic field intensity does not vary with depth, in the line formation region that ranges from ~200 to ~300 km above the tau5000=1 level. Title: High resolution solar magnetometry with the spectrograph of the Pic du Midi Turret Dome Authors: Malherbe, J. -M.; Roudier, Th.; Mein, P.; Moity, J.; Muller, R. Bibcode: 2004A&A...427..745M Altcode: 2000astro.ph..3094R We present the first results obtained with a new Ferroelectric Liquid Crystal (FLC) polarimeter operating with the spectrograph of the Pic du Midi Turret Dome, since September 2003. We observed the solar granulation around active region NOAA 0459 with the Multichannel Subtractive Double Pass (MSDP) operating mode and analysed the circular polarization of the Na D1 589.6 nm spectral line in terms of longitudinal magnetic fields in a 2D field of view (16× 142 arcsec). Image quality was fairly good and limited to 0.4 arcsec due to the pixel sampling. This observation reveals the presence of magnetic concentrations of several hundred Gauss which are mainly located in the intergranular lanes. Data analysis performed at two different optical depths (line core and line wings) also suggests that magnetic lines are curved and diverge with increasing altitude. 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: SOLARNET: the solution to the high resolution needs of solar physics Authors: Dame, L.; Clade, S.; Malherbe, J. M. Bibcode: 2004cosp...35.3583D Altcode: 2004cosp.meet.3583D Encounter missions like the Solar Orbiter have high resolution imaging goals in addition to the plasma measurements. If context, arcsec imaging, might be possible and useful to interpret the plasma observation, we will demonstrate that the thermal conditions near the Sun will prevent to achieve any of the higher resolution goals even by taking the most state-of-the-art solar telescope (carbon-carbon structure, SiC mirrors, etc.). A far better solution to fulfill the high resolution needs is the SOLARNET mission. SOLARNET is a medium size high resolution solar physics mission proposed to CNES for a new start in 2006 and a possible launch in 2010. Partnerships with Germany, Belgium, China and India are under discussion. At the center of the SOLARNET mission is a 3-telescopes interferometer of 1 meter baseline capable to provide 50 times the best ever spatial resolution achieved in Space with previous, current or even planned solar missions: 20 mas - 20 km on the Sun in the FUV. The interferometer is associated to an on-axis subtractive double monochromator (imaging spectrograph) capable of high spectral (0.01 nm) and high temporal resolutions (50 ms) on a field of view of 40 arcsec and over the FUV and UV spectral domains (from 117.5 to 400 nm). This will allow to access process scales of magnetic reconnection, dissipation, emerging flux and much more, from the high chromosphere to the low corona with emphasis on the transition zone where the magnetic confinement is expected to be maximum. A whole new chapter of the physics of solar magnetic field structuring and evolution will be opened. Launched by an Eurockot on a high altitude sun-synchronous non-eclipsing orbit, SOLARNET will also provide continuous observations at a sustained rate for Helioseismology and solar cycle studies. We review the scientific program of SOLARNET and its advantages (and complementarities) with an encounter type mission (probe or orbiter), describe the interferometer concept and design, present the first imaging results of the SOLARNET breadboard obtained at Meudon Observatory this spring and give a short overview of the mission aspects. Title: SOLARNET: a high resolution mission to complement the ILWS programme Authors: Dame, L.; Clade, S.; Malherbe, J. M. Bibcode: 2004cosp...35.3579D Altcode: 2004cosp.meet.3579D SOLARNET is a medium size high resolution solar physics mission proposed to CNES for a new start in 2006 and a possible launch in 2010. Partnerships with Germany, Belgium, China and India are under discussion. At the center of the SOLARNET mission is a 3-telescopes interferometer of 1 meter baseline capable to provide 50 times the best ever spatial resolution achieved in Space with previous, current or even planned solar missions: 20 mas - 20 km on the Sun in the FUV. The interferometer is associated to an on-axis subtractive double monochromator (imaging spectrograph) capable of high spectral (0.01 nm) and high temporal resolutions (50 ms) on a field of view of 40 arcsec and over the FUV and UV spectral domains (from 117.5 to 400 nm). This will allow to access process scales of magnetic reconnection, dissipation, emerging flux and much more, from the high chromosphere to the low corona with emphasis on the transition zone where the magnetic confinement is expected to be maximum. A whole new chapter of the physics of solar magnetic field structuring and evolution will be opened. The interferometer is complemented by several other instruments providing larger field of view and higher temperature (EUV-XUV coronal imaging) to define the context and extension of the solar phenomena. Helioseismology, a strong asset of SOHO, is also intended with both velocity and diameter measures, allowed by a non-eclipsing Sun synchronous orbit. The SOLARNET interferometer design results of an extensive laboratory demonstration program of interferometric imaging of extended objects. It started 10 years ago and culminates this year with the first interferometric observations (images) of the Sun at Meudon Observatory at the "Grand Siderostat de Foucault" with a complete 3 telescopes cophased interferometer representative of SOLARNET. We will review the scientific program of SOLARNET, describe the interferometer concept and design, present the first solar imaging results of the breadboard and give a short overview of the mission aspects. Title: Families of fragmenting granules and their relation to meso- and supergranular flow fields Authors: Roudier, Th.; Lignières, F.; Rieutord, M.; Brandt, P. N.; Malherbe, J. M. Bibcode: 2003A&A...409..299R Altcode: 3D analysis (x,y,t) of the granular intensity field (11-hour time sequence from the Swedish Vacuum Solar Telescope on La Palma, Canary Islands), demonstrates that a significant fraction of the granules in the photosphere are organized in the form of ``Trees of Fragmenting Granules" (TFGs). A TFG consists of a family of repeatedly splitting granules, originating from a single granule at its beginning. A striking result is that TFGs can live much longer (up to 8 h) than individual granules (10 min). We find that 62% of the area covered by granules belongs to TFGs of a lifetime >1.5 h. When averaged in time, such long-lived TFGs correspond to coherent diverging flows which may be identified as mesogranules. We also find a correlation between the network and the spatial distribution of TFGs. Title: High spatial resolution capabilities of Doppler measurements with the Pic du Midi MSDP spectrograph Authors: Roudier, Th.; Malherbe, J. M.; Mein, P.; Muller, R.; Coutard, C.; Lafon, M.; Grimaud, F. Bibcode: 2003A&A...409..793R Altcode: We analyse observations in the NaD1 line (lambda 5896 Å) obtained with the MSDP spectrograph of the Turret Dome of the Pic du Midi Observatory. Individual images reveal high spatial resolution and the data reduction shows the high capabilities of the spectrograph to get doppler measurements up to the limit of the resolution of the refractor (0\farcs3). Dopplershifts are obtained in the middle and high photosphere. The smallest granules 0\farcs4 show upward motions in the middle photosphere. Title: Interpretation of a complex CME event: Coupling of scales in multiple flux systems Authors: Maia, D.; Aulanier, G.; Wang, S. J.; Pick, M.; Malherbe, J. -M.; Delaboudinière, J. -P. Bibcode: 2003A&A...405..313M Altcode: Using multi-wavelength observations, in particular in imagery, recorded by SOHO/LASCO-MDI, Yohkoh/SXT, the Meudon spectroheliograph and the Nançay radioheliograph, and performing a linear force-free field extrapolation, we analyzed the triggering and the development of a complex eruptive event in the chromosphere and in the corona. This event included an X1 class flare and an eruptive filament within an active region, but it also involved a whole active complex spanning over 40 degrees of heliolongitude. It resulted in a fast and decelerating partial halo CME, associated with a Moreton wave and a complex series of metric, decimetric and microwave radio bursts. The presence of a coronal null point combined with the occurrence of two distant and nearly simultaneous radio sources give strong arguments in favor of the generalized breakout model for the triggering of the eruption. The observations are consistent with the occurrence of magnetic reconnection at the null point three minutes before the start of the eruption, which is consistent with other observed CME precursors. The analysis of the subsequent development of the event suggests that large interconnecting loops were ejected together with the CME, and that secondary reconnections at low altitude probably occurred remotely in the active complex. Our results show that the triggering and evolution of this complex CME involved multiple magnetic flux systems over a large coronal volume surrounding the flare site, and that it resulted from the coupling of scales from narrow reconnection current sheets to very large inter active region magnetic connections. Title: Na I D1 Stokes V Asymmetries and Velocity Structure Around Sunspots Authors: Eibe, M. T.; Sánchez Almeida, J.; Mein, P.; Aulanier, G.; Malherbe, J. M. Bibcode: 2003ASPC..307..374E Altcode: No abstract at ADS Title: Recurrence of fragmenting granules and their relation to meso- and supergranular flow fields Authors: Roudier, Th.; Lignières, F.; Rieutord, M.; Brandt, P. N.; Malherbe, J. -M. Bibcode: 2003EAS.....9..371R Altcode: The 3D analysis (x, y, t) of the granulation intensity field (11-hour time sequence from Swedish Vacuum Solar Telescope on La Palma, Canary Islands), demonstrated that the granules in the phostosphere are organized in ``Trees of Fragmenting Granules" (TFGs). A TFG consists of a family of repeatedly splitting granules, issued from one granule at its beginning. A striking result is that TFGs can live much longer (up to 8h10) than individual granules (10 mn). When averaged in time, such long-lived TFGs can be identified to the mesogranules. We also found a correlation between the network and the spatial distribution of TFGs. Title: Photometry of rapidly evolving chromospheric bright points in NOAA 9661 as observed by Themis and the Ondřejov multichannel flare spectrograph Authors: Kotrč, P.; Kupryakov, Yu. A.; Havlíčková, E.; Chambe, G.; Malherbe, J. -M. Bibcode: 2002ESASP.506..669K Altcode: 2002svco.conf..669K; 2002ESPM...10..669K Active region NOAA 9661 was observed on 13 October 2001 via narrow band Hα filters at THEMIS and at the Ondřejov Multichannel Flare Spectrograph both at a cadence of 25 images per second. Rapidly evolving bright points located at various places close to the sunspot were noticed several times during the day from 6 UT until 13 UT. Quite often their sudden appearance and disappearance seemed to be strongly correlated. We expect these small areas to be magnetically interconnected and possibly heated by injections of the same population of electrons moving along the magnetic field lines. Light curves of Hα emission integrated over individual bright areas were derived to search for short-timescale variations and to analyze them, especially concerning their correlations between different pairs of these areas. A similar analysis was performed for sites in all the active region for comparison and calibration purposes. Changes in correlations are discussed. Title: Vertical structure of sunspots from THEMIS observations Authors: Eibe, M. T.; Aulanier, G.; Faurobert, M.; Mein, P.; Malherbe, J. M. Bibcode: 2002A&A...381..290E Altcode: We have analysed two-dimensional spectro-polarimetric data taken with the MSDP observing mode of THEMIS in the Na I D1 line to investigate the height variation of the magnetic field in sunspot umbrae. From the Zeeman-induced circular polarization measured at individual MSDP channels within the line profile, maps of the longitudinal magnetic field have been computed. A method based on Response Functions has been developed to estimate the depth in the atmosphere at which the Zeeman measurements are originated, thus providing the line-of-sight field at different altitudes in the photosphere. The magnetogram corresponding to the deepest level has served as a boundary condition to perform the potential field extrapolation into the corona. We have found that the spatial distribution of vertical field gradient contours predicted from extrapolation is in qualitatively good agreement with that inferred from observations. Quantitatively, however, the longitudinal field gradients obtained with both methods differ about one order of magnitude, being larger for observations. The origin of this discrepancy has been discussed with respect to possible observation biases, as well as to idealizations used for field extrapolation. This is a crucial problem to be addressed in future work, and may have important implications for the physics of how the magnetic field evolves through sunspots and how the flux is distributed in the corona. 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: Temporal height properties of the exploding granules Authors: Roudier, Th.; Eibe, M. T.; Malherbe, J. M.; Rieutord, M.; Mein, P.; Mein, N.; Faurobert, M. Bibcode: 2001A&A...368..652R Altcode: Based on time series of 2D MSDP spectrograms, taken at the Turret Dome in Pic du Midi, we present the temporal evolution of exploding granules in intensity and Doppler velocity through the solar photosphere. We describe the penetration of exploding granules in the solar photosphere during their lifes and the related phenomena like the ``Bright Plumes'' located in the downflowing plasma just on the edge of the granule. We suggest a possible scenario of the exploding granule evolution in the solar photosphere. Title: Emergence of a U-loop - sub-photospheric link between solar active regions Authors: van Driel-Gesztelyi, L.; Malherbe, J. -M.; Démoulin, P. Bibcode: 2000A&A...364..845V Altcode: Using SOHO/MDI magnetic maps we present the first direct observational evidence for the emergence of a U-loop in the solar photosphere. We show that two active regions (ARs), i.e. two adjacent Omega -loops, which were emerging at the same time at the same solar latitude, about 150000 km distance in longitude from each other, emerged from at least partially the same toroidal flux strand, and we bring five independent arguments to prove this assertion. The opposite polarity legs of the two Omega -loops were connected below the photosphere by a U-shaped loop. Following the emergence of the Omega -loops, the U-loop started emerging, manifested by the fast proper motion of the leading spots of the eastern (smaller) active region, which, after forming an elongated channel, collided with the following spots of the westerly AR and started cancelling with them. The full cancellation could not be followed because the ARs rotated out of sight. The total magnetic flux of the two ARs was unequal, the flux in the smaller AR was a quarter of that of the larger one. We propose scenarios for the formation of such a U-loop and discuss the implications of the confirmed existence of U-loops for the solution of such puzzles as the in-situ disappearance of magnetic flux from active regions, active nests and the formation of inter-AR filaments. Title: On mesogranulation, network formation and supergranulation Authors: Rieutord, M.; Roudier, T.; Malherbe, J. M.; Rincon, F. Bibcode: 2000A&A...357.1063R Altcode: We present arguments which show that in all likelihood mesogranulation is not a true scale of solar convection but the combination of the effects of both highly energetic granules, which give birth to strong positive divergences (SPDs) among which we find exploders, and averaging effects of data processing. The important role played by SPDs in horizontal velocity fields appears in the spectra of these fields where the scale ~ 4 Mm is most energetic; we illustrate the effect of averaging with a one-dimensional toy model which shows how two independent non-moving (but evolving) structures can be transformed into a single moving structure when time and space resolution are degraded. The role of SPDs in the formation of the photospheric network is shown by computing the advection of floating corks by the granular flow. The coincidence of the network bright points distribution and that of the corks is remarkable. We conclude with the possibility that supergranulation is not a proper scale of convection but the result of a large-scale instability of the granular flow, which manifests itself through a correlation of the flows generated by SPDs. 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: 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: Determination of horizontal velocity fields at the sun's surface with high spatial and temporal resolution Authors: Roudier, Th.; Rieutord, M.; Malherbe, J. M.; Vigneau, J. Bibcode: 1999A&A...349..301R Altcode: We analyse the two algorithms which have been used in the past few years to determine the horizontal flow fields at the Sun's surface, namely the Local Correlation Tracking (LCT) of L. November and the Feature Tracking of L. Strous. Analysing the systematic errors introduced by LCT, we show that these errors come from the averaging processes. More precisely, they arise from the interpolating step of the algorithm: granules' motions determine the flow on an irregular grid which is then interpolated to derive quantities such as horizontal divergence or vertical vorticity. Interpolation is therefore a crucial step since mesoscale structures have mainly been studied through divergences and vorticities. We conclude that a reliable algorithm should be based on the tracking of coherent structures, like granules, since they are representative of the fluid motion, and should contain an interpolator which keeps track of the errors introduced either by location of the data (the shape of the irregular grid) or by the noise in the data. 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: Internal intermittency on the Sun surface? Authors: Roudier, T.; Rieutord, M.; Malherbe, J. M.; Vigneau, J. Bibcode: 1999joso.proc..197R Altcode: An improved version of LCT and FT is presented and used to determine high spatial and temporal resolution horizontal flow fields at the Sun's surface. The granule diplacements and group evolution can be followed. The horizontal flow fields calculated by these methods show a structured flow at mean scale (4 to 8 arcsec) by a group of granules which is probably related to the local intermittency. 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: 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: Surveillance et prévision de l'activité solaire à l'Observatoire de Paris. Authors: Malherbe, J. -M. Bibcode: 1998JAF....56....5M Altcode: No abstract at ADS 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: Solar mesogranule lifetime measurements Authors: Roudier, Th.; Malherbe, J. M.; Vigneau, J.; Pfeiffer, B. Bibcode: 1998A&A...330.1136R Altcode: { We present a study in which the solar lifetime of mesocells (4-10 arcsec) was determined from a long time sequence (6h 40min) obtained at the Pic du Midi Observatory. The mesocell detection was performed by local correlation tracking, using various spatial and temporal windows. The histograms derived from the visual measurements reveal that mesoscale lifetime is between 10min and 160min, with peaked distributions around 30-40min. The indirect method for lifetime estimation using a correlation coefficient, gives a mesocale lifetime from 16 to 185min depending on the temporal window and the methods used. The proper motions of the long-living mesocells are found to be random with respect to the superganule flows, with the peak distribution of horizontal velocities at 0.5km/s. The results of this mesocell lifetime determination method are smaller by a factor of 2 to 5 with respect to the previous results. This difference could be attributed to the mesocell definition, the method of measurement or the different location of the mesocell field of view in the supergranular network. } 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: 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: 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: 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: 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: Flare Multi-Line 2D-SPECTROSCOPY Authors: Mein, P.; Mein, N.; Malherbe, J. -M.; Heinzel, P.; Kneer, F.; von Uexkull, M.; Staiger, J. Bibcode: 1997SoPh..172..161M Altcode: 1997ESPM....8..161M A small flare was observed at the Teide Observatory on October 5, 1994. Simultaneous data were obtained at the German Vacuum Tower Telescope (VTT) with the MSDP spectrograph providing high-resolution imaging spectroscopy in two chromospheric lines, and the Gregory Coudé Telescope (GCT) providing information about the magnetic field. Basic flare characteristics are: Title: Intergranular plumes and formation of network bright points. Authors: Roudier, T.; Malherbe, J. M.; November, L.; Vigneau, J.; Coupinot, G.; Lafon, M.; Muller, R. Bibcode: 1997A&A...320..605R Altcode: We discuss the temporal evolution of the photospheric intergranular lanes using a 1 hour time sequence of white-light images of solar granulation. The time series was obtained with the 50 cm refractor at the turret dome of the Pic du Midi Observatory. Analysis reveals the existence of singularities in the intergranular lanes that we call ``intergranular holes''. Intergranular holes, which have diameters between 0.24arcsec and 0.45arcsec, are continuously visible for more than 45 minutes. The holes appear to be systematically distributed at the periphery of mesogranular and supergranular cells. Our study reveals the formation of bright points (BPs) in 4 out of 14 cases studied very close to the intergranular holes, suggesting that intergranular holes may be the locations where magnetic flux tubes are formed. Title: 3-D reconnection related to new emerging flux Authors: Schmeider, B.; Démoulin, P.; Aulanier, G.; Malherbe, J. M.; van Driel-Gesztelyi, L.; Mandrini, C. H.; Roudier, T.; Nitta, N.; Harra-Murnion, L. K. Bibcode: 1997AdSpR..19.1871S Altcode: We present evidences that emergence of new flux in the lower atmosphere leads to magnetic reconnection of field lines. In a first phase the phenomenon is observed in the chromosphere by the formation of dark filaments (arch filament system) which are overlaid by bright loops visible in soft X-rays. Different types of event appear according to the magnetic field configuration and the amount of energy involved. 3-D modelling of the photospheric magnetic field provides a new tool for understanding reconnection in real configurations. The observed chromospheric and coronal loops are good diagnostics for the modelling. We document our statement by examples obtained during coordinated campaigns with the Hα Multichannel Subtractive Double Pass spectrographs-MSDP (Pic du Midi and Tenerife) and the Yohkoh instruments. Title: BASS 2000 THEMIS Archive Authors: Roudier, Th.; Malherbe, J. M. Bibcode: 1997ASPC..118..377R Altcode: 1997fasp.conf..377R No abstract at ADS 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: Spatial relation between the 5-minute oscillations and granulation patterns. Authors: Espagnet, O.; Muller, R.; Roudier, T.; Mein, P.; Mein, N.; Malherbe, J. M. Bibcode: 1996A&A...313..297E Altcode: A white light, high resolution movie of the quiet photosphere has been used to study the spatial relation between the solar granulation and the 5-min oscillations of high degree mode (small spatial scale). The granular and oscillatory brightness components have been separated with the help of a specific filter, in the k-ω diagram. The surface of the Sun appears to be covered with adjacent oscillating cells of apparent size 2" (1500km) to 3" (2000km). Some cells are noticeable by their amplitude which is much larger than average. These strong oscillations usually appear in expanding intergranular spaces. Our observations suggest that the 5-min oscillations are stochastically generated by turbulent convection. However, the most energetic oscillations occur in downflows only, well separated of each other in time and space. Title: Cloud model with variable source function for solar Hα structures. Authors: Mein, N.; Mein, P.; Heinzel, P.; Vial, J. -C.; Malherbe, J. M.; Staiger, J. Bibcode: 1996A&A...309..275M Altcode: The "cloud model" used to derive the physical parameters of solar chromospheric features is extended to the cases of non-constant source function and of velocity gradients. This model assumes a given relationship between the source function and the opacity of the cloud which is derived from non-LTE modelling. An algorithm using 4 points of the Halpha_ profile is proposed to derive the optical thickness, the line-of-sight velocity and the dopplerwidth. The results are compared with a 5-points inversion which does not use the given relationship between source function and opacity. Effects of the uncertainty about the radiation coming from the underlying chromosphere, as well as effects of data noise, are discussed. The inversion method is illustrated by some examples of observed profiles obtained with the MSDP spectrograph of the VTT telescope (Teide Observatory). 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: High resolution flare observations with multi-line imaging spectroscopy. Authors: Mein, P.; Heinzel, P.; Malherbe, J. -M.; Staiger, J. Bibcode: 1996joso.proc...68M Altcode: No abstract at ADS Title: The Server of the Observatoire de Paris-Meudon-Nançay Authors: Arenou, F.; Chevalier, J. M.; Dubost, K.; Huille, S.; Laurent, C.; Letourneur, L.; Malherbe, J. M.; Schneider, J.; Spite, F.; Spite, M. Bibcode: 1995VA.....39...97A Altcode: No abstract at ADS Title: The Sun. Authors: Martres, M. J.; Boyer, R.; Costard, F.; Malherbe, J. M.; Olivieri, G. Bibcode: 1994oga..book....1M Altcode: Contents: 1. Introduction. 2. The changing appearance of the Sun. 3. How to observe the Sun. 4. Amateur observing programmes. 5. Monochromatic observation of the Sun. 6. Conclusion. Title: Janssen et l'Observatoire astronomique du mont Blanc. Authors: Malherbe, J. -M. Bibcode: 1993LAstr.107..278M Altcode: No abstract at ADS Title: Linear force-free magnetic field around quiescent solar prominences computed from observable boundary conditions Authors: Demoulin, P.; Raadu, M. A.; Malherbe, J. M. Bibcode: 1992A&A...257..278D Altcode: The magnetic support of solar prominences in two-dimensional linear force-free fields is analyzed. The prominence was modeled as a vertical current sheet with mass in equilibrium between gravity and magnetic forces. A finite difference numerical technique was used which incorporates both vertical photospheric and horizontal prominence magnetic field observations as boundary conditions. The mixed-boundary value problem is described and the current singularity generally present is eliminated by a modification of the initial boundary condition. Using the linear force-free hypothesis the bipolar and quadripolar regions were found to be associated with normal and inverse prominence polarity respectively. An increase of magnetic shear decreases the mass supported for a given vertical dependence of the field component orthogonal to the prominence. Title: La fondation de l'observatoire et les débuts de l'astronomie au Pic du Midi (1852 - 1947). Dernière partie: Le règne de la coupole Baillaud. Authors: Malherbe, J. -M.; Coutard, C.; Roudier, T. Bibcode: 1991LAstr.105R...1M Altcode: No abstract at ADS Title: La fondation de l'observatoire et les débuts de l'astronomie au Pic du Midi (1852 - 1947). Deuxième partie: L'introduction de l'astronomie. Authors: Malherbe, J. -M.; Coutard, C.; Roudier, T. Bibcode: 1991LAstr.105Q...1M Altcode: No abstract at ADS Title: A numerical simulation of magnetic reconnection and radiative cooling in line-tied current sheets Authors: Forbes, T. G.; Malherbe, J. M. Bibcode: 1991SoPh..135..361F Altcode: We have used the radiative MHD equations for an optically thin plasma to carry out a numerical experiment related to the formation of `post'-flare loops. The numerical experiment starts with a current sheet that is in mechanical and thermal equilibrium, but which is unstable to both tearing-mode and thermal-condensation instabilities. The current sheet is line-tied at one end to a photospheric-like boundary and evolves asymmetrically. The effects of thermal conduction, resistivity variation, and gravity are ignored. In general, we find that reconnection in the nonlinear stage of the tearing-mode instability can strongly affect the onset of condensations unless the radiative cooling time scale is much smaller than the tearing-mode time scale. When the ambient plasma β is less than 0.2, the reconnection enters a regime where the outflow from the reconnection region is supermagnetosonic with respect to the fast-mode wave speed. In the supermagnetosonic regime the most rapidly condensing regions occur downstream of a fast-mode shock that forms where the outflow impinges on closed loops attached to the photospheric-like boundary. A similar shock-induced condensation might occur during the formation of `post'-flare loops. Title: La fondation de l'observatoire et les débuts de l'astronomie au Pic du Midi (1852 - 1947). Introduction. Première partie: La fondation de l'observatoire. Authors: Malherbe, J. -M.; Coutard, C.; Roudier, T. Bibcode: 1991LAstr.105....6M Altcode: No abstract at ADS Title: Dynamics of the solar granulation. II - Statistical analysis: Power spectra, coherence, phase Authors: Roudier, T.; Vigneau, J.; Espagnet, O.; Muller, R.; Mein, P.; Malherbe, J. M. Bibcode: 1991A&A...248..245R Altcode: The solar granulation is analyzed statistically by the computation of coherence, phase, and power spectra using data provided by the Multichannel Subtractive Double Pass spectrograph of the Pic du Midi Observatory. The main result of the analysis is that the velocity power spectrum of the granulation changes in shape at 3 arcsec: the raw spectrum features a slope discontinuity; the corrected spectra have a power maximum at 3 arcsec. Between 3 arcsec and the resolution limit (0.8 arcsec), the power decreases almost linearly, with a slope close to -5/3, consistent with the Kolmogorov power law for a turbulent energy cascade. Title: Dynamics of solar granulation. I - Processing of MSDP spectra Authors: Roudier, T.; Vigneau, J.; Mein, P.; Malherbe, J. M.; Coutard, C.; Hellier, R.; Muller, R. Bibcode: 1991A&A...248..237R Altcode: High resolution (about 0.5 arcsec) 2D spectra have been obtained with the Multichannel Subtractive Double Pass spectrograph of the Pic du Midi Observatory in a quiet region at the solar disk center. The adapted image processing which provides 2D intensity and velocity maps of the solar granulation, at two intensity levels of the line NaD2, is described. A quantitative evaluation of the spatial resolution is determined both for the intensity and velocity granulation fields. Title: Results from high resolution solar images and spectra obtained at the Pic du Midi Observatory (1986-1990) Authors: Roudier, Th.; Muller, R.; Vigneau, J.; Auffret, H.; Espagnet, O.; Simon, G. W.; Title, A. M.; Frank, Z.; Shine, R. A.; Tarbell, T. D.; Mein, P.; Malherbe, J. M. Bibcode: 1991AdSpR..11e.205R Altcode: 1991AdSpR..11..205R We present an overview of our recent results about solar granulation and mesogranulation, obtained with Pic du Midi observations. These results were obtained during 1986-1990 using image and spectrographic analysis of high spatial resolution data. The study of the solar granulation, with 2 Dim. ``Multichannel Subtractive Double Pass'' (M.S.D.P.) spectra, shows a clear change of the dynamical regime at 3'' (⋍ 2200 km) of the photospheric velocity field when oscillatory components are filtered out.

A three hour movie obtained on film at Pic du Midi Observatory and analyzed at the Lockheed Research Laboratory and the National Solar Observatory (Sacramento Peak) was used to calculate the horizontal flow pattern. The mean lifetime of the diverging areas related to mesogranulation is estimated at 3 hours; these diverging areas are swept by the supergranulation flow towards the supergranule boundary with a mean speed of 0.4 km/s. Title: L'Observatoire des Rayons Cosmiques à l'Aiguille du Midi. Authors: Malherbe, J. -M. Bibcode: 1990LAstr.104..243M Altcode: No abstract at ADS 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: The Formation of Flare Loops by Magnetic Reconnection and Chromospheric Ablation Authors: Forbes, T. G.; Malherbe, J. M.; Priest, E. R. Bibcode: 1989SoPh..120..285F Altcode: Slow-mode shocks produced by reconnection in the corona can provide the thermal energy necessary to sustain flare loops for many hours. These slow shocks have a complex structure because strong thermal conduction along field lines dissociates the shocks into conduction fronts and isothermal subshocks. Heat conducted along field lines mapping from the subshocks to the chromosphere ablates chromospheric plasma and thereby creates the hot flare loops and associated flare ribbons. Here we combine a non-coplanar compressible reconnection theory with simple scaling arguments for ablation and radiative cooling, and predict average properties of hot and cool flare loops as a function of the coronal vector magnetic field. For a coronal field strength of 100 G the temperature of the hot flare loops decreases from 1.2 × 107 K to 4.0 × 106 K as the component of the coronal magnetic field perpendicular to the plane of the loops increases from 0% to 86% of the total field. When the perpendicular component exceeds 86% of the total field or when the altitude of the reconnection site exceeds 106km, flare loops no longer occur. Shock enhanced radiative cooling triggers the formation of cool Hα flare loops with predicted densities of ≈ 1013 cm−3, and a small gap of ≈ 103 km is predicted to exist between the footpoints of the cool flare loops and the inner edges of the flare ribbons. Title: Granulation velocity field: latest results from Pic-du-Midi - processing of MSDP data Authors: Mein, P.; Roudier, Th.; Vigneau, J.; Muller, R.; Malherbe, J. M.; Contard, C.; Hellier, R. Bibcode: 1989hsrs.conf..521M Altcode: No abstract at ADS Title: The magnetic field around quiescent solar prominences computed from observational boundary conditions Authors: Demoulin, P.; Malherbe, J. M.; Priest, E. R. Bibcode: 1989A&A...211..428D Altcode: A generalization of Anzer's model (1972) for quiescent prominence support is presented. The coronal field is assumed to be current-free except inside the prominence where currents support dense material against gravity. The prominence is taken to be an infinitely thin current sheet of finite extent along the vertical axis. The hypothesis of two-dimensional fields allows the use of complex functions to solve the mixed boundary problem which is defined by the observed vertical field in the photosphere and the horizontal magnetic field in the prominence. These boundary conditions are not sufficient to determine a unique solution for the magnetic field. The indeterminacy is decreased by physical considerations, and some models for Normal (N) and Inverse (I) configurations are presented. In both cases it is possible to find field configurations which can support the fintie prominence against gravity. Title: Protuberanzen und Beobachtungsprogramme. Authors: Malherbe, J. -M.; Martres, M. -J.; Vial, J. -C. Bibcode: 1989Sonne..13....8M Altcode: No abstract at ADS Title: Oscillations of the sun's chromosphere. V - Importance of network dynamics for chromospheric heating Authors: von Uexkuell, M.; Kneer, F.; Malherbe, J. M.; Mein, P. Bibcode: 1989A&A...208..290V Altcode: A 64-min time sequence of disk center H-alpha spectrograms taken with the MSDP spectrograph at the Observatoire du Pic du Midi is analyzed. This type of spectrograph allows spectroscopy of a two-dimensional field of view. From the H-alpha line profiles at each pixel, line-shift and minimum intensity fluctuation are determined as functions of spatial and temporal coordinates. A frequency analysis with standard Fourier techniques is performed. It is confirmed that in the interior of the chromospheric network cells the oscillatory behavior dominates, whereas at the boundaries one generally finds random motions on scales of 2-10 arcsec. The random behavior of the H-alpha structures outlines the permanent rearrangement of the magnetic field lines pushed around by the subphotospheric granular flow. Title: The formation of solar prominences Authors: Malherbe, J. -M. Bibcode: 1989ASSL..150..115M Altcode: 1988dsqs.work..115M; 1989dsqs.work..115M Recent progress in the understanding of the formation of quiescent solar prominences is summarized, from both an observational and theoretical point of view. It is now well known that the mass of a quiescent prominence (seen in emission at the solar limb) or a filament (generally seen in absorption above the disk) is an appreciable part of the mass of the entire corona (roughly one tenth or more), which makes it difficult to form these structures by coronal condensation alone. Hence possible mechanisms proposed recently to account for their formation are divided into two categories, namely, injection (of the chromospheric material into the corona by siphon flows) and condensation (of the coronal plasma itself). Title: Particles and energy transport in the solar atmosphere during solar flares. Authors: Heristchi, D.; Raadu, M. A.; Vial, J. -C.; Malherbe, J. -M. Bibcode: 1989sasf.confP.321H Altcode: 1988sasf.conf..321H; 1989IAUCo.104P.321H The proposed model of particle transport in the solar atmosphere during flares consists in a low density plasmoid originating deep in the atmosphere and rising under magnetic and buoyancy forces. Confined particles are selectively released during the ascent and their interaction with the solar atmosphere produces X and γ bremsstrahlung. The characteristics of high energy particles released in the interplanetary medium are found to agree with observations. Title: Quelques phénomènes de l'optique atmosphérique. Authors: Malherbe, Jean-Marie Bibcode: 1988LAstr.102..351M Altcode: Atmospheric optical effects resulting from the interaction between extended light sources (the sun and moon) or point sources (planets and bright stars) and the heterogeneous atmosphere are discussed. It is noted that refraction is responsible for such phenomena as the oblateness of the sun and moon when rising or setting, mirages (the curving of light rays near the ground), nocturnal scintillation, rainbows, and halos. The diffusion of light by particles in the atmosphere is responsible for the blue color of the sky during the day and the red color of the sky at sunrise and sunset. Diffractive phenomena discussed include the colored ring surrounding the sun or moon when viewed through fog and the iridescent Bishop's ring. Title: Two Solar Observation Programmes Authors: Marthes, M. J.; Malherbe, J. M.; Vial, J. Bibcode: 1988scaa.conf..175M Altcode: 1988IAUCo..98..175M No abstract at ADS Title: The formation of solar prominences. Authors: Malherbe, J. M. Bibcode: 1988dssp.conf...77M Altcode: Recent progress in the understanding of the formation of quiescent solar prominences is summarized in this paper, from both an observational and theoretical point of view. The first part as a review of recent observations; the second one presents main instabilities involved in prominence formation, and is a summary of first attempts to model this complex phenomenon. The third part investigates filament formation by chromospheric injection, while the fourth one describes recent models of coronal condensation. 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: 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: Contribution a l'etude magneto thermo dynamique des protuberances solaires Authors: Malherbe, Jean-Marie Bibcode: 1987PhDT.......217M Altcode: No abstract at ADS Title: Inversion of line profile disturbances - A nonlinear method applied to solar CaII lines Authors: Mein, P.; Mein, N.; Malherbe, J. M.; Dame, L. Bibcode: 1987A&A...177..283M Altcode: Thermodynamical disturbances in the solar atmosphere can be deduced from observations of line profiles. The authors propose a non-linear method based on Fourier analysis: each profile is converted into a "double profile" for a fast convergence of Fourier expansions. Disturbances of Fourier coefficients are connected theoretically with physical disturbances by second order developments. Temperature and velocity fluctuations are derived from a least square inversion of these developments. The authors apply this method to a time sequence of high resolution profiles of the Ca II 3968 Å line. The accuracy of the results is discussed. The enhanced blue peaks occurring in the asymmetric profiles are interpreted as downward velocity gradients, associated with temperature excesses. Title: Protubérances solaires et programmes d'observation. Authors: Malherbe, Jean-Marie; Martres, Marie-Josephe; Vial, Jean-Claude Bibcode: 1987LAstr.101..321M Altcode: The observed characteristics of solar prominences are reviewed, and models for the formation of filaments and for the magnetic structure of protuberances are discussed. Data suggest that coronal filaments are formed either by the pumping of chromospheric matter or by condensation of the coronal plasma itself by thermal instability. The class of Kippenhahn-Schluter models involve magnetic rings which are bent under the influence of gravity, and the class of Kuperus-Raadu models place prominences above a certain neutral point. Observations of filamentary velocity fields indicate that the magnetic support of the condensation is in quasi-static evolution. Three proposed areas of study of prominences, the connections and exchanges of matter at great distances, eruptive prominences, and the sudden disappearance of prominences, are discussed. 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: Dynamics of the solar granulation. Authors: Muller, R.; Roudier, Th.; Malherbe, J. M.; Mein, P. Bibcode: 1987PAICz..66..175M Altcode: 1987eram....1..175M In order to understand the origin of the solar granulation, convective or turbulent, in this paper the authors report results about the intensity-velocity correlation and the energy power spectrum derived from the Doppler shifts measurement on two-dimensional high resolution spectrograms. 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: The Formation of Solar Prominences Authors: Malherbe, J. M. Bibcode: 1987dssp.work...77M Altcode: 1987ASSL..150...77M No abstract at ADS Title: Les observatoires du Mont-Blanc en 1900. Authors: Malherbe, J. -M. Bibcode: 1987LAstr.101..115M Altcode: 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: 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: On the thermal durability of solar prominences, or how to evaporate aprominence? Authors: Malherbe, J. M.; Forbes, T. G. Bibcode: 1986NASCP2442..225M Altcode: 1986copp.nasa..225M The authors investigate the thermal disappearance of solar prominences under strong perturbations due to wave heating, Ohmic heating, viscous heating or conduction. Specifically, they calculate how large a thermal perturbation is needed to destroy a stable thermal equilibrium, and find that the prominence plasma appears to be thermally very rugged. Its cold equilibrium may most likely be destroyed by either strong magnetic heating or conduction in a range of parameters which is relevant to flares. 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: Can prominences form in current sheets? Authors: Malherbe, J. M.; Forbes, T. G. Bibcode: 1986NASCP2442...33M Altcode: 1986copp.nasa...33M Two-dimensional numerical simulations of the formation of cold condensations in a vertical current sheet have been performed using the radiative, resistive MHD equations with line-tied boundary conditions at one end of the sheet. Prominence-like condensations are observed to appear above and below an X-line produced by the onset of the tearing-mode instability. Cooling in the sheet is initiated by Ohmic decay, with the densest condensations occurring in the region downstream of a fast-mode shock. This shock, which is due to the line-tied boundary conditions, terminates one of the two supermagnetosonic reconnection jets that develop when the tearing is fully developed. This paper emphasizes the condensation properties of shock waves, which may trigger or considerably enhance the conditions for thermal condensations. Title: Transition zone effects on thermal non-equilibrium and plasma condensation in solar coronal loops Authors: She, Z. S.; Malherbe, J. M.; Raadu, M. A. Bibcode: 1986A&A...164..364S Altcode: The quasi-static thermal structure of arches or loops in the solar corona is investigated analytically, integrating the classical HD equations numerically along the magnetic-field lines and taking the effect of the transition region joining the arches to the chromosphere into account. Expressions for determining the mechanical heating rate and summit temperature from the footpoint chromospheric density and the loop length are obtained, and the implications of a solution with a cold dense mass sheet at the arcade summit are explored. Title: A Shock Condensation Mechanism for Loop Prominences Authors: Forbes, T. G.; Malherbe, J. M. Bibcode: 1986ApJ...302L..67F Altcode: Self-consistent, numerical solutions of the resistive MHD equations in two dimensions show that a quasi-stationary, fast-mode shock is a characteristic feature of the reconnection dynamics of the Kopp-Pneuman model of two-ribbon flares. A preliminary analysis of the effects of radiative cooling and thermal conduction suggests that the fast shock can help trigger a thermal condensation (i.e., a loop prominence) if the reconnecting magnetic fields are sufficiently strong. Title: Numerical Image Processing Applied to the Solar Corona Authors: Malherbe, J. M.; Noens, J. C.; Roudier, Th. Bibcode: 1986SoPh..103..393M Altcode: Numerical data processing is applied to the high-resolution images-of the solar corona obtained with the 20 cm coronagraph of the Pic du Midi observatory. Two complementary methods are proposed to solve some classical difficulties usually met in the morphological analysis of the solar corona, namely the brightness gradient in the inner and medium corona, the low contrast of numerous emissive regions and the superimposition along the line of sight of different structures. The methods which are described in this paper may help to resolve the complex coronal active regions into fine structures which is now necessary to interpret all observed corona data. Title: A reconnection mechanism for coronal condensations in two-ribbon flares. Authors: Forbes, T. G.; Malherbe, J. M. Bibcode: 1986lasf.conf..443F Altcode: 1986lasf.symp..443F During the last few years the authors have used a series of self-consistent two-dimensional, MHD calculations to explore the reconnection dynamics implied by the two-ribbon flare model of Kopp and Pneuman (1976). The calculations show, that in addition to the standard slow-mode MHD shocks generated by reconnection, there also exists a standing fast-mode MHD shock. Because of thermal conduction, the slow shocks generate an evaporative upflow of chromospheric plasma into the reconnection region. Analysis of the effects of radiative and conductive cooling suggests that at least some of this evaporated plasma will undergo thermal condensation when it passes through the fast shock. Title: THEMIS: un projet solaire national pour une recherche internationale. Authors: Rayrolle, J.; Mein, P.; Malherbe, J. -M. Bibcode: 1986JAF....28....6R Altcode: No abstract at ADS 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: Inversion of Chromospheric Line Profiles Authors: Mein, P.; Mein, N.; Malherbe, J. M. Bibcode: 1985tphr.conf..303M Altcode: No abstract at ADS Title: Mass Motions in Hα Absorbing Structures of the Solar Chromosphere Authors: Mein, P.; Malherbe, J. M.; Mein, N.; Mouradian, Z.; Schmeider, B. Bibcode: 1985tphr.conf..316M Altcode: No abstract at ADS 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: Inversion of chromospheric line profiles. Authors: Mein, P.; Mein, N.; Malherbe, J. M. Bibcode: 1985MPARp.212..303M Altcode: Because of the large amount of high resolution data which becomes available now from solar observations, fast codes are urgently needed in order to interpret disturbed line profiles. The authors present briefly two kinds of algorithms usable in the case of chromospheric lines. 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: Atmospheric structure deduced from disturbed line profiles - application to Ca II lines. Authors: Mein, N.; Mein, P.; Malherbe, J. -M.; Dame, L.; Dumont, S. Bibcode: 1985cdm..proc..167M Altcode: A new method is described in order to derive physical quantities (temperature, pressure, radial velocities) from the observation of disturbed line profiles. The authors suggest a method of Fourier analysis with double profiles and a non linear expansion of the coefficient of the Fourier terms. An application to a sequence of H - Ca II line is attempted. The method seems a powerful tool allowing the determination of at least 4 physical quantities simultaneously. 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: Magnetic instabilities in solar filaments: models of twisting motionsand ejecta. Authors: Schmeider, B.; Malherbe, J. M.; Raadu, M. Bibcode: 1984ESASP.220..273S Altcode: 1984ESPM....4..273S Time sequences of two destabilized solar filaments were derived using a spectrograph operated in H alpha. The opposite directed velocities observed in the first filament are interpreted in terms of a twisted magnetic flux rope model. The sudden disappearance of the second filament corresponds to high velocity plasmoids confined in magnetic field lines and then ejected. Title: A numerical simulation of the formation of solar prominences. Authors: Malherbe, J. M.; Forbes, T. G.; Priest, E. R. Bibcode: 1984ESASP.220..119M Altcode: 1984ESPM....4..119M The radiative-resistive MHD equations are numerically solved in two-dimensions for a magnetic field configuration that starts with a vertical current sheet which is line-tied at its base and is in mechanical, but not radiative, equilibrium. The aim of the present study is to determine whether this initial configuration can achieve a prominence-like equilibrium in the presence of magnetic reconnection and tearing in the current-sheet. 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: 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: Intensity oscillations in the calcium - K line Authors: Gouttebroze, P.; Dame, L.; Malherbe, J. -M. Bibcode: 1984MmSAI..55..245G Altcode: An analysis is undertaken of a time sequence of quiet sun filtergrams taken in the core of the K line, in order to investigate the oscillatory properties of the chromosphere. The physical significance of these intensity variations and their diagnostic capabilities are discussed, and an oscillatory power vs. frequency and mean intensity diagram is noted to indicate the different behaviors of bright regions dominated by low frequency waves and darker regions dominated by high frequency waves. A diagnostic wavenumber-frequency diagram indicates two oscillatory power concentrations which approximately correspond to acoustic and gravity waves, in chromospheric conditions. A theoretical diagnostic diagram computed on the basis of a solar atmosphere model exhibits a 'g-1' chromospheric mode; this corresponds almost exactly to the location of the observed ridge. 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: Méthodes aux différences finies pour la résolution numérique des équations aux dérivées partielles de la dynamique des fluides et de la magnétohydrodynamique dans le cadre de problèmes à conditions aux limites et conditions initiales. Authors: Malherbe, J. -M. Bibcode: 1984cms..conf..221M Altcode: No abstract at ADS Title: Observation and analysis of intensity oscillations in the solar K-line Authors: Dame, L.; Gouttebroze, P.; Malherbe, J. -M. Bibcode: 1984A&A...130..331D Altcode: Chromospheric oscillations are investigated with a time sequence of filtergrams of the sun taken in the core of the Ca II K-line at the Sacramento Peak Observatory. The relations between oscillation frequency and wavenumber are analyzed, as are those between frequency and mean intensity. Intensity analysis reveals that low frequency waves are associated mainly with bright (chromospheric network) regions, while the '3-min' oscillation dominates in cell interiors. As the mean brightness of the observed region increases, the high frequency limit of oscillatory power decreases. This is interpreted as the decrease of the resonance frequency of the chromospheric cavity with increasing temperatures, which confirms the chromospheric origin of the 3-min oscillations. Diagnostic diagrams suggest that both acoustic and internal gravity waves occur in the chromosphere and appear to have a modal structure. Title: Equilibre MHD et instabilités dans les protubérances ou filaments solaires. Authors: Malherbe, J. -M. Bibcode: 1984cms..conf..383M Altcode: No abstract at ADS Title: Current sheet models for solar prominences. II - Energetics and condensation process Authors: Malherbe, J. M.; Priest, E. R.; Forbes, T. G.; Heyvaerts, J. Bibcode: 1983A&A...127..153M Altcode: A steady state dynamic model for solar prominences of the Kuperus and Raadu type was previously proposed by Malherbe and Priest (1983), but only the motion through series of quasi-static states was investigated there. The mechanisms for formation, condensation and cooling of plasma in this model are studied. As hot coronal material approaches the filament sheet, it is expected to cool and condense. Cold material is then carried up through the prominence by rising magnetic field lines due to converging photospheric motions below the filament. Two possible ways are suggested of triggering a thermal instability and so producing such a stationary condensation process: a larger pressure in the sheet, or a smaller wave heating in the reconnected field than in the surrounding corona. This paper presents a simple model to simulate the plasma condensation: the thermodynamics of the cooling process, as well as the dynamics of new material entering the prominence sheet, are described in detail. Title: Current sheet models for solar prominences. I Magnetohydrostatics of support and evolution through quasi-static models Authors: Malherbe, J. M.; Priest, E. R. Bibcode: 1983A&A...123...80M Altcode: Several 2D current sheet models for solar prominences, supported against gravity by potential magnetic configurations, are presented. Simple magnetostatic solutions, both of Kuperus-Raadu type (KR) and of Kippenhahn-Schlüter type (KS) are built with the help of complex functions and discussed. The authors suggest that, in the case of KS models, slow (<100 ms-1) diverging photospheric flows below prominences could explain the upward motions reported by Malherbe et al. (1983) in disk filaments; while, in the case of KR models, slow converging flows could explain them. To account for such motions and magnetic field observations by Leroy et al. (1983) it is proposed in Raadu's spirit (1979), a quasi-static reconnection model, in which new material entering the prominence condenses and is brought up through it by the moving magnetic field. The resulting dynamics is studied in a simple magnetic geometry of KR type. Title: Equilibre magnetohydrodynamique des protuberances solaires Authors: Malherbe, Jean-Marie Bibcode: 1983MsT.........21M Altcode: A study of the magneto hydrodynamic equilibrium of solar prominences, PhD THESIS, University of PARIS 7 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: 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: 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: 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: 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