Author name code: fleck ADS astronomy entries on 2022-09-14 author:"Fleck, Bernhard" ------------------------------------------------------------------------ Title: Acoustic-gravity wave propagation characteristics in 3D radiation hydrodynamic simulations of the solar atmosphere Authors: Fleck, Bernhard; Khomenko, Elena; Carlsson, Mats; Rempel, Matthias; Steiner, Oskar; Riva, Fabio; Vigeesh, Gangadharan Bibcode: 2022cosp...44.2503F Altcode: There has been tremendous progress in the degree of realism of three-dimensional radiation magneto-hydrodynamic simulations of the solar atmosphere in the past decades. Four of the most frequently used numerical codes are Bifrost, CO5BOLD, MANCHA3D, and MURaM. Here we test and compare the wave propagation characteristics in model runs from these four codes by measuring the dispersion relation of acoustic-gravity waves at various heights. We find considerable differences between the various models. Title: Power distribution of oscillations in the atmosphere of a plage region. Joint observations with ALMA, IRIS, and SDO Authors: Narang, Nancy; Chandrashekhar, Kalugodu; Jafarzadeh, Shahin; Fleck, Bernhard; Szydlarski, Mikołaj; Wedemeyer, Sven Bibcode: 2022A&A...661A..95N Altcode: 2022arXiv220211547N Context. Joint observations of the Atacama Large Millimeter/Submillimeter Array (ALMA) with other solar observatories can provide a wealth of opportunities for understanding the coupling between different layers of the solar atmosphere.
Aims: We present a statistical analysis of the power distribution of oscillations in a plage region in active region NOAA AR12651, which was observed jointly with ALMA, the Interface Region Imaging Spectrograph (IRIS), and the Solar Dynamics Observatory (SDO).
Methods: We employ coordinated ALMA Band 6 (1.25 mm) brightness temperature maps, IRIS slit-jaw images in the 2796 Å passband, and observations in six passbands (1600 Å, 304 Å, 131 Å, 171 Å, 193 Å, and 211 Å) from the Atmospheric Imaging Assembly (AIA) on board SDO. We perform Lomb-Scargle transforms to study the distribution of oscillation power by means of dominant period maps and power maps. We study the spatial association of oscillations through the atmosphere, with a focus on the correlation of the power distribution of ALMA oscillations with others.
Results: We do not observe any significant association of ALMA oscillations with IRIS and AIA oscillations. While the global behavior of the dominant ALMA oscillations shows a similarity with that of the transition region and coronal passbands of AIA, the ALMA dominant period maps and power maps do not show any correlation with those from the other passbands. The spatial distribution of dominant periods and power in different period intervals of ALMA oscillations is uncorrelated with those of any other passbands.
Conclusions: We speculate that the non-association of ALMA oscillations with those of IRIS and AIA is due to significant variations in the height of formation of the millimeter continuum observed by ALMA. Additionally, the fact that ALMA directly maps the brightness temperature, in contrast to the intensity observations by IRIS and AIA, can result in the very different intrinsic nature of the ALMA oscillations compared to the IRIS and AIA oscillations. Title: Large scale coherent magnetohydrodynamic oscillations in a sunspot Authors: Stangalini, M.; Verth, G.; Fedun, V.; Aldhafeeri, A. A.; Jess, D. B.; Jafarzadeh, S.; Keys, P. H.; Fleck, B.; Terradas, J.; Murabito, M.; Ermolli, I.; Soler, R.; Giorgi, F.; MacBride, C. D. Bibcode: 2022NatCo..13..479S Altcode: Although theoretically predicted, the simultaneous excitation of several resonant modes in sunspots has not been observed. Like any harmonic oscillator, a solar magnetic flux tube can support a variety of resonances, which constitute the natural response of the system to external forcing. Apart from a few single low order eigenmodes in small scale magnetic structures, several simultaneous resonant modes were not found in extremely large sunspots. Here we report the detection of the largest-scale coherent oscillations observed in a sunspot, with a spectrum significantly different from the Sun's global acoustic oscillations, incorporating a superposition of many resonant wave modes. Magnetohydrodynamic numerical modeling agrees with the observations. Our findings not only demonstrate the possible excitation of coherent oscillations over spatial scales as large as 30-40 Mm in extreme magnetic flux regions in the solar atmosphere, but also paves the way for their diagnostic applications in other astrophysical contexts. Title: A novel approach to identify resonant MHD wave modes in solar pores and sunspot umbrae: B − ω analysis Authors: Stangalini, M.; Jess, D. B.; Verth, G.; Fedun, V.; Fleck, B.; Jafarzadeh, S.; Keys, P. H.; Murabito, M.; Calchetti, D.; Aldhafeeri, A. A.; Berrilli, F.; Del Moro, D.; Jefferies, S. M.; Terradas, J.; Soler, R. Bibcode: 2021A&A...649A.169S Altcode: 2021arXiv210311639S The umbral regions of sunspots and pores in the solar photosphere are generally dominated by 3 mHz oscillations, which are due to p-modes penetrating the magnetic region. In these locations, wave power is also significantly reduced with respect to the quiet Sun. However, here we study a pore where not only is the power of the oscillations in the umbra comparable to, or even larger than, that of the quiet Sun, but the main dominant frequency is not 3 mHz as expected, but instead 5 mHz. By combining Doppler velocities and spectropolarimetry and analysing the relationship between magnetic field strength and frequency, the resultant B − ω diagram reveals distinct ridges that are remarkably clear signatures of resonant magneto-hydrodynamic (MHD) oscillations confined within the pore umbra. We demonstrate that these modes, in addition to velocity oscillations, are also accompanied by magnetic oscillations, as predicted from MHD theory. The novel technique of B − ω analysis proposed in this article opens up an exciting new avenue for identifying MHD wave modes in the umbral regions of both pores and sunspots. Title: An overall view of temperature oscillations in the solar chromosphere with ALMA Authors: Jafarzadeh, S.; Wedemeyer, S.; Fleck, B.; Stangalini, M.; Jess, D. B.; Morton, R. J.; Szydlarski, M.; Henriques, V. M. J.; Zhu, X.; Wiegelmann, T.; Guevara Gómez, J. C.; Grant, S. D. T.; Chen, B.; Reardon, K.; White, S. M. Bibcode: 2021RSPTA.37900174J Altcode: 2021RSTPA.379..174J; 2020arXiv201001918J By direct measurements of the gas temperature, the Atacama Large Millimeter/submillimeter Array (ALMA) has yielded a new diagnostic tool to study the solar chromosphere. Here, we present an overview of the brightness-temperature fluctuations from several high-quality and high-temporal-resolution (i.e. 1 and 2 s cadence) time series of images obtained during the first 2 years of solar observations with ALMA, in Band 3 and Band 6, centred at around 3 mm (100 GHz) and 1.25 mm (239 GHz), respectively. The various datasets represent solar regions with different levels of magnetic flux. We perform fast Fourier and Lomb-Scargle transforms to measure both the spatial structuring of dominant frequencies and the average global frequency distributions of the oscillations (i.e. averaged over the entire field of view). We find that the observed frequencies significantly vary from one dataset to another, which is discussed in terms of the solar regions captured by the observations (i.e. linked to their underlying magnetic topology). While the presence of enhanced power within the frequency range 3-5 mHz is found for the most magnetically quiescent datasets, lower frequencies dominate when there is significant influence from strong underlying magnetic field concentrations (present inside and/or in the immediate vicinity of the observed field of view). We discuss here a number of reasons which could possibly contribute to the power suppression at around 5.5 mHz in the ALMA observations. However, it remains unclear how other chromospheric diagnostics (with an exception of Hα line-core intensity) are unaffected by similar effects, i.e. they show very pronounced 3-min oscillations dominating the dynamics of the chromosphere, whereas only a very small fraction of all the pixels in the 10 ALMA datasets analysed here show peak power near 5.5 mHz.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: High-frequency oscillations in small chromospheric bright features observed with Atacama Large Millimetre/Submillimetre Array Authors: Guevara Gómez, J. C.; Jafarzadeh, S.; Wedemeyer, S.; Szydlarski, M.; Stangalini, M.; Fleck, B.; Keys, P. H. Bibcode: 2021RSPTA.37900184G Altcode: 2020arXiv200804179G We report detection of oscillations in brightness temperature, size and horizontal velocity of three small bright features in the chromosphere of a plage/enhanced-network region. The observations, which were taken with high temporal resolution (i.e. 2 s cadence) with the Atacama large millimetre/ submillimetre array (ALMA) in Band 3 (centred at 3 mm; 100 GHz), exhibit three small-scale features with oscillatory behaviour with different, but overlapping, distributions of period on the order of, on average, 90 ± 22 s, 110 ± 12 s and 66 ± 23 s, respectively. We find anti-correlations between perturbations in brightness, temperature and size of the three features, which suggest the presence of fast sausage-mode waves in these small structures. In addition, the detection of transverse oscillations (although with a larger uncertainty) may also suggest the presence of Alfvénic oscillations which are likely representative of kink waves. This work demonstrates the diagnostic potential of high-cadence observations with ALMA for detecting high-frequency magnetohydrodynamic waves in the solar chromosphere. Such waves can potentially channel a vast amount of energy into the outer atmosphere of the Sun.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: A new method for detecting solar atmospheric gravity waves Authors: Calchetti, Daniele; Jefferies, Stuart M.; Fleck, Bernhard; Berrilli, Francesco; Shcherbik, Dmitriy V. Bibcode: 2021RSPTA.37900178C Altcode: 2020arXiv200800210C Internal gravity waves have been observed in the Earth's atmosphere and oceans, on Mars and Jupiter, and in the Sun's atmosphere. Despite ample evidence for the existence of propagating gravity waves in the Sun's atmosphere, we still do not have a full understanding of their characteristics and overall role for the dynamics and energetics of the solar atmosphere. Here, we present a new approach to study the propagation of gravity waves in the solar atmosphere. It is based on calculating the three-dimensional cross-correlation function between the vertical velocities measured at different heights. We apply this new method to a time series of co-spatial and co-temporal Doppler images obtained by SOHO/MDI and Hinode/SOT as well as to simulations of upward propagating gravity wave-packets. We show some preliminary results and outline future developments.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: Acoustic-gravity wave propagation characteristics in three-dimensional radiation hydrodynamic simulations of the solar atmosphere Authors: Fleck, B.; Carlsson, M.; Khomenko, E.; Rempel, M.; Steiner, O.; Vigeesh, G. Bibcode: 2021RSPTA.37900170F Altcode: 2020arXiv200705847F There has been tremendous progress in the degree of realism of three-dimensional radiation magneto-hydrodynamic simulations of the solar atmosphere in the past decades. Four of the most frequently used numerical codes are Bifrost, CO5BOLD, MANCHA3D and MURaM. Here we test and compare the wave propagation characteristics in model runs from these four codes by measuring the dispersion relation of acoustic-gravity waves at various heights. We find considerable differences between the various models. The height dependence of wave power, in particular of high-frequency waves, varies by up to two orders of magnitude between the models, and the phase difference spectra of several models show unexpected features, including ±180° phase jumps.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: On the influence of magnetic topology on the propagation of internal gravity waves in the solar atmosphere Authors: Vigeesh, G.; Roth, M.; Steiner, O.; Fleck, B. Bibcode: 2021RSPTA.37900177V Altcode: 2020arXiv201006926V The solar surface is a continuous source of internal gravity waves (IGWs). IGWs are believed to supply the bulk of the wave energy for the lower solar atmosphere, but their existence and role for the energy balance of the upper layers is still unclear, largely due to the lack of knowledge about the influence of the Sun's magnetic fields on their propagation. In this work, we look at naturally excited IGWs in realistic models of the solar atmosphere and study the effect of different magnetic field topographies on their propagation. We carry out radiation-magnetohydrodynamic simulations of a magnetic field free and two magnetic models-one with an initial, homogeneous, vertical field of 100 G magnetic flux density and one with an initial horizontal field of 100 G flux density. The propagation properties of IGWs are studied by examining the phase-difference and coherence spectra in the kh - ω diagnostic diagram. We find that IGWs in the upper solar atmosphere show upward propagation in the model with predominantly horizontal field similar to the model without magnetic field. In contrast to that the model with predominantly vertical fields show downward propagation. This crucial difference in the propagation direction is also revealed in the difference in energy transported by waves for heights below 0.8 Mm. Higher up, the propagation properties show a peculiar behaviour, which require further study. Our analysis suggests that IGWs may play a significant role in the heating of the chromospheric layers of the internetwork region where horizontal fields are thought to be prevalent.

This article is part of the Theo Murphy meeting issue `High-resolution wave dynamics in the lower solar atmosphere'. Title: Reply to: Signatures of sunspot oscillations and the case for chromospheric resonances Authors: Jess, David B.; Snow, Ben; Fleck, Bernhard; Stangalini, Marco; Jafarzadeh, Shahin Bibcode: 2021NatAs...5....5J Altcode: 2020NatAs.tmp..149J No abstract at ADS Title: 3D Visualisation of Solar Data with JHelioviewer Authors: Mueller, D.; Nicula, B.; Verstringe, F.; Bourgoignie, B.; Csillaghy, A.; Laube, S.; Berghmans, D.; Ireland, J.; Fleck, B. Bibcode: 2020AGUFMSH0360001M Altcode: The Solar Orbiter and Parker Solar Probe missions focus on exploring the linkage between the Sun and the heliosphere. These new missions are collecting unique data that will allow us to study the coupling between macroscopic physical processes to those on kinetic scales, the generation of solar energetic particles and their propagation into the heliosphere and the origin and acceleration of solar wind plasma.

The scientific community now has access to large volumes of complex remote-sensing and in-situ observations from different vantage points, complemented by petabytes of simulation data. Answering overarching science questions like "How do solar transients drive heliospheric variability and space weather?" will only be possible if the science community has the necessary tools at hand to visualize these data and assimilate them into sophisticated models.

A key piece needed to bridge the gap between observables, derived quantities like magnetic field extrapolations and model output is a tool to routinely and intuitively visualise large heterogeneous, multidimensional, time-dependent data sets. The open-source JHelioviewer software, which is part of the ESA/NASA Helioviewer Project, is addressing this need. This contribution highlights recent extensions of JHelioviewer's functionality, in particular those of interest for Solar Orbiter. Title: Data reduction pipeline for MOF-based synoptic telescopes Authors: Forte, Roberta; Berrilli, Francesco; Calchetti, Daniele; Del Moro, Dario; Fleck, Bernhard; Giebink, Cynthia; Giebink, William; Giovannelli, Luca; Jefferies, Stuart Mark; Knox, Allister; Magrì, Maria; Murphy, Neil; Nitta, Garry; Oliviero, Maurizio; Pietropaolo, Ermanno; Rodgers, Wayne; Scardigli, Stefano; Viavattene, Giorgio Bibcode: 2020JSWSC..10...63F Altcode: There are strong scientific cases and practical reasons for building ground-based solar synoptic telescopes. Some issues, like the study of solar dynamics and the forecasting of solar flares, benefit from the 3D reconstruction of the Sun's atmosphere and magnetic field. Others, like the monitoring and prediction of space weather, require full disk observations, at the proper sampling rate, combining H-alpha images and Doppler velocity and magnetic field. The synoptic telescopes based on Magneto Optical Filters (MOF) using different lines are capable of measuring the line-of-sight Doppler velocity and magnetic field over the full solar disk at different ranges of height in the Sun's photosphere and low chromosphere. Instruments like the MOTH (Magneto-Optical filters at Two Heights), using a dual-channel based on MOFs operating at 589.0 nm (Na D2 line) and 769.9 nm (K D1 line), the VAMOS instrument (Velocity And Magnetic Observations of the Sun), operating at 769.9 nm (K D1 line), and the future TSST (Tor Vergata Synoptic Solar Telescope), using a dual-channel telescope operating at 656.28 nm (H-alpha line) and at 769.9 nm (K D1 line), allow to face both aspects, the scientific and the operative related to Space Weather applications. The MOTH, VAMOS and TSST data enable a wide variety of studies of the Sun, from seismic probing of the solar interior (sound speed, rotation, details of the tachocline, sub-surface structure of active regions), to the dynamics and magnetic evolution of the lower part of the solar atmosphere (heating of the solar atmosphere, identification of the signatures of solar eruptive events, atmospheric gravity waves, etc.), to the 3D reconstruction of the solar atmosphere and flare locations. However, the use of MOF filters requires special care in calibrating the data for scientific or operational use. This work presents a systematic pipeline that derives from the decennial use of MOF's technology. More in detail, the pipeline is based on data reduction procedures tested and validated on MOTH data acquired at Mees Solar Observatory of the University of Hawaii Haleakala Observatories and at South Pole Solar Observatory (SPSO), at the Amundsen-Scott South Pole Station in Antarctica, during Antarctica Summer Campaign 2016/17. Title: The Solar Orbiter Science Activity Plan. Translating solar and heliospheric physics questions into action Authors: Zouganelis, I.; De Groof, A.; Walsh, A. P.; Williams, D. R.; Müller, D.; St Cyr, O. C.; Auchère, F.; Berghmans, D.; Fludra, A.; Horbury, T. S.; Howard, R. A.; Krucker, S.; Maksimovic, M.; Owen, C. J.; Rodríguez-Pacheco, J.; Romoli, M.; Solanki, S. K.; Watson, C.; Sanchez, L.; Lefort, J.; Osuna, P.; Gilbert, H. R.; Nieves-Chinchilla, T.; Abbo, L.; Alexandrova, O.; Anastasiadis, A.; Andretta, V.; Antonucci, E.; Appourchaux, T.; Aran, A.; Arge, C. N.; Aulanier, G.; Baker, D.; Bale, S. D.; Battaglia, M.; Bellot Rubio, L.; Bemporad, A.; Berthomier, M.; Bocchialini, K.; Bonnin, X.; Brun, A. S.; Bruno, R.; Buchlin, E.; Büchner, J.; Bucik, R.; Carcaboso, F.; Carr, R.; Carrasco-Blázquez, I.; Cecconi, B.; Cernuda Cangas, I.; Chen, C. H. K.; Chitta, L. P.; Chust, T.; Dalmasse, K.; D'Amicis, R.; Da Deppo, V.; De Marco, R.; Dolei, S.; Dolla, L.; Dudok de Wit, T.; van Driel-Gesztelyi, L.; Eastwood, J. P.; Espinosa Lara, F.; Etesi, L.; Fedorov, A.; Félix-Redondo, F.; Fineschi, S.; Fleck, B.; Fontaine, D.; Fox, N. J.; Gandorfer, A.; Génot, V.; Georgoulis, M. K.; Gissot, S.; Giunta, A.; Gizon, L.; Gómez-Herrero, R.; Gontikakis, C.; Graham, G.; Green, L.; Grundy, T.; Haberreiter, M.; Harra, L. K.; Hassler, D. M.; Hirzberger, J.; Ho, G. C.; Hurford, G.; Innes, D.; Issautier, K.; James, A. W.; Janitzek, N.; Janvier, M.; Jeffrey, N.; Jenkins, J.; Khotyaintsev, Y.; Klein, K. -L.; Kontar, E. P.; Kontogiannis, I.; Krafft, C.; Krasnoselskikh, V.; Kretzschmar, M.; Labrosse, N.; Lagg, A.; Landini, F.; Lavraud, B.; Leon, I.; Lepri, S. T.; Lewis, G. R.; Liewer, P.; Linker, J.; Livi, S.; Long, D. M.; Louarn, P.; Malandraki, O.; Maloney, S.; Martinez-Pillet, V.; Martinovic, M.; Masson, A.; Matthews, S.; Matteini, L.; Meyer-Vernet, N.; Moraitis, K.; Morton, R. J.; Musset, S.; Nicolaou, G.; Nindos, A.; O'Brien, H.; Orozco Suarez, D.; Owens, M.; Pancrazzi, M.; Papaioannou, A.; Parenti, S.; Pariat, E.; Patsourakos, S.; Perrone, D.; Peter, H.; Pinto, R. F.; Plainaki, C.; Plettemeier, D.; Plunkett, S. P.; Raines, J. M.; Raouafi, N.; Reid, H.; Retino, A.; Rezeau, L.; Rochus, P.; Rodriguez, L.; Rodriguez-Garcia, L.; Roth, M.; Rouillard, A. P.; Sahraoui, F.; Sasso, C.; Schou, J.; Schühle, U.; Sorriso-Valvo, L.; Soucek, J.; Spadaro, D.; Stangalini, M.; Stansby, D.; Steller, M.; Strugarek, A.; Štverák, Š.; Susino, R.; Telloni, D.; Terasa, C.; Teriaca, L.; Toledo-Redondo, S.; del Toro Iniesta, J. C.; Tsiropoula, G.; Tsounis, A.; Tziotziou, K.; Valentini, F.; Vaivads, A.; Vecchio, A.; Velli, M.; Verbeeck, C.; Verdini, A.; Verscharen, D.; Vilmer, N.; Vourlidas, A.; Wicks, R.; Wimmer-Schweingruber, R. F.; Wiegelmann, T.; Young, P. R.; Zhukov, A. N. Bibcode: 2020A&A...642A...3Z Altcode: 2020arXiv200910772Z Solar Orbiter is the first space mission observing the solar plasma both in situ and remotely, from a close distance, in and out of the ecliptic. The ultimate goal is to understand how the Sun produces and controls the heliosphere, filling the Solar System and driving the planetary environments. With six remote-sensing and four in-situ instrument suites, the coordination and planning of the operations are essential to address the following four top-level science questions: (1) What drives the solar wind and where does the coronal magnetic field originate?; (2) How do solar transients drive heliospheric variability?; (3) How do solar eruptions produce energetic particle radiation that fills the heliosphere?; (4) How does the solar dynamo work and drive connections between the Sun and the heliosphere? Maximising the mission's science return requires considering the characteristics of each orbit, including the relative position of the spacecraft to Earth (affecting downlink rates), trajectory events (such as gravitational assist manoeuvres), and the phase of the solar activity cycle. Furthermore, since each orbit's science telemetry will be downloaded over the course of the following orbit, science operations must be planned at mission level, rather than at the level of individual orbits. It is important to explore the way in which those science questions are translated into an actual plan of observations that fits into the mission, thus ensuring that no opportunities are missed. First, the overarching goals are broken down into specific, answerable questions along with the required observations and the so-called Science Activity Plan (SAP) is developed to achieve this. The SAP groups objectives that require similar observations into Solar Orbiter Observing Plans, resulting in a strategic, top-level view of the optimal opportunities for science observations during the mission lifetime. This allows for all four mission goals to be addressed. In this paper, we introduce Solar Orbiter's SAP through a series of examples and the strategy being followed. Title: A New Method for Detecting Solar Atmospheric Gravity Waves Authors: Calchetti, D.; Jefferies, S.; Fleck, B.; Berrilli, F. Bibcode: 2020SPD....5120403C Altcode: For the past fifty years, acoustic waves generated near the solar surface have provided a powerful tool for the seismic mapping of the Sun's internal structure and dynamics. This field of research, known as helioseismology, has provided numerous fundamental breakthroughs in our understanding of the Sun's interior. Interestingly, the convective sources that produce the acoustic waves also produce internal gravity waves that propagate throughout the Sun's atmosphere. In principle, these waves can unlock the secrets of the Sun's atmosphere in much the same way as helioseismology revolutionized our view of the Sun's interior. However, despite ample evidence for their existence, we still do not fully understand the characteristics and overall role of the internal gravity waves for the dynamics and energetics of the solar atmosphere. Here we present a new approach to study the propagation of gravity waves in the solar atmosphere which finally opens the door for seismic mapping of the Sun's atmosphere. We show some preliminary results based on the analysis of both simulations and real observations, and we outline future developments. Title: The Sun at millimeter wavelengths. I. Introduction to ALMA Band 3 observations Authors: Wedemeyer, Sven; Szydlarski, Mikolaj; Jafarzadeh, Shahin; Eklund, Henrik; Guevara Gomez, Juan Camilo; Bastian, Tim; Fleck, Bernhard; de la Cruz Rodriguez, Jaime; Rodger, Andrew; Carlsson, Mats Bibcode: 2020A&A...635A..71W Altcode: 2020arXiv200102185W Context. The Atacama Large Millimeter/submillimeter Array (ALMA) started regular observations of the Sun in 2016, first offering receiver Band 3 at wavelengths near 3 mm (100 GHz) and Band 6 at wavelengths around 1.25 mm (239 GHz).
Aims: Here we present an initial study of one of the first ALMA Band 3 observations of the Sun. Our aim is to characterise the diagnostic potential of brightness temperatures measured with ALMA on the Sun.
Methods: The observation covers a duration of 48 min at a cadence of 2 s targeting a quiet Sun region at disc-centre. Corresponding time series of brightness temperature maps are constructed with the first version of the Solar ALMA Pipeline and compared to simultaneous observations with the Solar Dynamics Observatory (SDO).
Results: The angular resolution of the observations is set by the synthesised beam, an elliptical Gaussian that is approximately 1.4″ × 2.1″ in size. The ALMA maps exhibit network patches, internetwork regions, and elongated thin features that are connected to large-scale magnetic loops, as confirmed by a comparison with SDO maps. The ALMA Band 3 maps correlate best with the SDO/AIA 171 Å, 131 Å, and 304 Å channels in that they exhibit network features and, although very weak in the ALMA maps, imprints of large-scale loops. A group of compact magnetic loops is very clearly visible in ALMA Band 3. The brightness temperatures in the loop tops reach values of about 8000-9000 K and in extreme moments up to 10 000 K.
Conclusions: ALMA Band 3 interferometric observations from early observing cycles already reveal temperature differences in the solar chromosphere. The weak imprint of magnetic loops and the correlation with the 171, 131, and 304 SDO channels suggests, however, that the radiation mapped in ALMA Band 3 might have contributions from a wider range of atmospheric heights than previously assumed, but the exact formation height of Band 3 needs to be investigated in more detail. The absolute brightness temperature scale as set by total power measurements remains less certain and must be improved in the future. Despite these complications and the limited angular resolution, ALMA Band 3 observations have a large potential for quantitative studies of the small-scale structure and dynamics of the solar chromosphere.

Movies are available at https://www.aanda.org Title: Measuring the Dispersion Relation of Acoustic-Gravity Waves in the Solar Atmosphere Authors: Fleck, Bernhard; Jefferies, Stuart M.; Murphy, Neil; Berrilli, Francesco Bibcode: 2020ASSP...57..141F Altcode: We use localized measurements of the dispersion relation for acoustic-gravity waves to generate the first maps of the spatial structure of the sound speed, acoustic cut-off frequency, and radiative damping time in the Sun's lower atmosphere. These maps offer a new diagnostic for the solar atmosphere. Title: A chromospheric resonance cavity in a sunspot mapped with seismology Authors: Jess, David B.; Snow, Ben; Houston, Scott J.; Botha, Gert J. J.; Fleck, Bernhard; Krishna Prasad, S.; Asensio Ramos, Andrés; Morton, Richard J.; Keys, Peter H.; Jafarzadeh, Shahin; Stangalini, Marco; Grant, Samuel D. T.; Christian, Damian J. Bibcode: 2020NatAs...4..220J Altcode: 2019NatAs...4..220J; 2019NatAs.tmp..502J Sunspots are intense collections of magnetic fields that pierce through the Sun's photosphere, with their signatures extending upwards into the outermost extremities of the solar corona1. Cutting-edge observations and simulations are providing insights into the underlying wave generation2, configuration3,4 and damping5 mechanisms found in sunspot atmospheres. However, the in situ amplification of magnetohydrodynamic waves6, rising from a few hundreds of metres per second in the photosphere to several kilometres per second in the chromosphere7, has, until now, proved difficult to explain. Theory predicts that the enhanced umbral wave power found at chromospheric heights may come from the existence of an acoustic resonator8-10, which is created due to the substantial temperature gradients experienced at photospheric and transition region heights11. Here, we provide strong observational evidence of a resonance cavity existing above a highly magnetic sunspot. Through a combination of spectropolarimetric inversions and comparisons with high-resolution numerical simulations, we provide a new seismological approach to mapping the geometry of the inherent temperature stratifications across the diameter of the underlying sunspot, with the upper boundaries of the chromosphere ranging between 1,300 ± 200 km and 2,300 ± 250 km. Our findings will allow the three-dimensional structure of solar active regions to be conclusively determined from relatively commonplace two-dimensional Fourier power spectra. The techniques presented are also readily suitable for investigating temperature-dependent resonance effects in other areas of astrophysics, including the examination of Earth-ionosphere wave cavities12. Title: Observed Local Dispersion Relations for Magnetoacoustic-gravity Waves in the Sun’s Atmosphere: Mapping the Acoustic Cutoff Frequency Authors: Jefferies, Stuart M.; Fleck, Bernhard; Murphy, Neil; Berrilli, Francesco Bibcode: 2019ApJ...884L...8J Altcode: 2019arXiv191003198J We present the observed local dispersion relations for magnetoacoustic-gravity waves in the Sun’s atmosphere for different levels of magnetic field strength. We model these data with a theoretical local dispersion relation to produce spatial maps of the acoustic cutoff frequency in the Sun’s photosphere. These maps have implications for the mechanical heating of the Sun’s upper atmosphere, by magnetoacoustic-gravity waves, at different phases of the solar magnetic activity cycle. Title: Detection of Three-minute Oscillations in Full-disk Lyman-alpha Emission during a Solar Flare Authors: Milligan, Ryan O.; Fleck, Bernhard; Ireland, Jack; Fletcher, Lyndsay; Dennis, Brian R. Bibcode: 2018csc..confE..36M Altcode: In a recent study of spatially-integrated Lyman-alpha line emission (Lya, 1216A) from GOES/EUVS, we detected the presence of acoustic 3-minute oscillations during an X-class solar flare. Similar periodicities were also found - in phase - in Lyman continuum data from SDO/EVE, and the 1600A and 1700A channels on SDO/AIA. The implication is that the chromosphere responds dynamically at its acoustic cutoff frequency to an impulsive injection of energy. Since the 3-minute period was not detected at hard X-ray energies in RHESSI data we can state that this 3-minute oscillation does not depend on the rate of energisation of non-thermal electrons. This finding suggests that chromospheric mechanical energy should be included in the flare energy budget, and that fluctuations in Lya emission may influence the composition and dynamics of planetary atmospheres during periods of high activity. Knowledge of the behaviour of this emission during flares could be important when interpreting future science results from the EUI instrument on Solar Orbiter which will obtain high cadence images in Lya. Title: The MOTH II Doppler-Magnetographs and Data Calibration Pipeline Authors: Forte, Roberta; Jefferies, Stuart M.; Berrilli, Francesco; Del Moro, Dario; Fleck, Bernhard; Giovannelli, Luca; Murphy, Neil; Pietropaolo, Ermanno; Rodgers, Wayne Bibcode: 2018IAUS..335..335F Altcode: The calibration pipeline of the level zero images obtained from the Magneto-Optical filters at Two Heights (MOTH II) instrument is presented. MOTH II consists of two 20 cm aperture instruments, each using a Magneto-Optical Filter (MOF): one at 5896 Å (Na D2-line), the other one at 7700 Å (K I-line). MOTH II instruments thus provide full disk line-of-sight Doppler velocity and magnetic field measurements at two heights in the solar atmosphere. The developed MOTH II pipeline employs a set of standard calibration corrections, a correction for signal leakage, due to the non-ideal behavior of the polarizers, and the geometrical registration between the eight images acquired by four CMOS cameras, relative to two components of the signal in two circular polarization states, in each of the two channels. MOTH II data are used to investigate atmospheric dynamics (e.g., internal gravity waves and magneto-acoustic portals) and Space Weather phenomena. Particularly, flare forecasting algorithms, based on the detection of magnetic active regions (ARs) and associated flare probability estimation, are currently under development. The possible matching of MOTH II data with SDO/HMI and SDO/AIA images into a flux rope model, developed in collaboration between Harvard-Smithsonian CfA and MIT Laboratory for Nuclear Science, is being tested. Title: Detection of 3-Minute Oscillations in Full-Disk Lyman-alpha Emission During A Solar Flare Authors: Milligan, R. O.; Ireland, J.; Fleck, B.; Hudson, H. S.; Fletcher, L.; Dennis, B. R. Bibcode: 2017AGUFMSH41A2739M Altcode: We report the detection of chromospheric 3-minute oscillations in disk-integrated EUV irradiance observations during a solar flare. A wavelet analysis of detrended Lyman-alpha (from GOES/EUVS) and Lyman continuum (from SDO/EVE) emission from the 2011 February 15 X-class flare revealed a 3-minute period present during the flare's main phase. The formation temperature of this emission locates this radiation to the flare's chromospheric footpoints, and similar behaviour is found in the SDO/AIA 1600A and 1700A channels, which are dominated by chromospheric continuum. The implication is that the chromosphere responds dynamically at its acoustic cutoff frequency to an impulsive injection of energy. Since the 3-minute period was not found at hard X-ray energies (50-100 keV) in RHESSI data we can state that this 3-minute oscillation does not depend on the rate of energization of, or energy deposition by, non-thermal electrons. However, a second period of 120 s found in both hard X-ray and chromospheric emission is consistent with episodic electron energization on 2-minute timescales. Our finding on the 3-minute oscillation suggests that chromospheric mechanical energy should be included in the flare energy budget, and the fluctuations in the Lyman-alpha line may influence the composition and dynamics of planetary atmospheres during periods of high activity. Title: Franz-Ludwig Deubner (1934 - 2017) Authors: Fleck, Bernhard; von der Lühe, Oskar Bibcode: 2017SoPh..292..178F Altcode: No abstract at ADS Title: 3D Visualization of Solar Data: Preparing for Solar Orbiter and Parker Solar Probe Authors: Mueller, D.; Nicula, B.; Felix, S.; Verstringe, F.; Bourgoignie, B.; Csillaghy, A.; Berghmans, D.; Jiggens, P.; Ireland, J.; Fleck, B. Bibcode: 2017AGUFMSH23D2686M Altcode: Solar Orbiter and Parker Solar Probe will focus on exploring the linkage between the Sun and the heliosphere. These new missions will collect unique data that will allow us to study, e.g., the coupling between macroscopic physical processes to those on kinetic scales, the generation of solar energetic particles and their propagation into the heliosphere and the origin and acceleration of solar wind plasma. Combined with the several petabytes of data from NASA's Solar Dynamics Observatory, the scientific community will soon have access to multi­dimensional remote-sensing and complex in-situ observations from different vantage points, complemented by petabytes of simulation data. Answering overarching science questions like "How do solar transients drive heliospheric variability and space weather?" will only be possible if the community has the necessary tools at hand. In this contribution, we will present recent progress in visualizing the Sun and its magnetic field in 3D using the open-source JHelioviewer framework, which is part of the ESA/NASA Helioviewer Project. Title: Detection of Three-minute Oscillations in Full-disk Lyα Emission during a Solar Flare Authors: Milligan, Ryan O.; Fleck, Bernhard; Ireland, Jack; Fletcher, Lyndsay; Dennis, Brian R. Bibcode: 2017ApJ...848L...8M Altcode: 2017arXiv170909037M In this Letter we report the detection of chromospheric 3-minute oscillations in disk-integrated EUV irradiance observations during a solar flare. A wavelet analysis of detrended Lyα (from GOES/EUVS) and Lyman continuum (from Solar Dynamics Observatory (SDO)/EVE) emission from the 2011 February 15 X-class flare (SOL2011-02-15T01:56) revealed a ∼3 minute period present during the flare’s main phase. The formation temperature of this emission locates this radiation at the flare’s chromospheric footpoints, and similar behavior is found in the SDO/Atmospheric Imaging Assembly 1600 and 1700 Å channels, which are dominated by chromospheric continuum. The implication is that the chromosphere responds dynamically at its acoustic cutoff frequency to an impulsive injection of energy. Since the 3-minute period was not found at hard X-ray (HXR) energies (50-100 keV) in Reuven Ramaty High Energy Solar Spectroscopic Imager data we can state that this 3-minute oscillation does not depend on the rate of energization of non-thermal electrons. However, a second period of 120 s found in both HXR and chromospheric lightcurves is consistent with episodic electron energization on 2-minute timescales. Our finding on the 3-minute oscillation suggests that chromospheric mechanical energy should be included in the flare energy budget, and the fluctuations in the Lyα line may influence the composition and dynamics of planetary atmospheres during periods of high activity. Title: JHelioviewer. Time-dependent 3D visualisation of solar and heliospheric data Authors: Müller, D.; Nicula, B.; Felix, S.; Verstringe, F.; Bourgoignie, B.; Csillaghy, A.; Berghmans, D.; Jiggens, P.; García-Ortiz, J. P.; Ireland, J.; Zahniy, S.; Fleck, B. Bibcode: 2017A&A...606A..10M Altcode: 2017arXiv170507628M Context. Solar observatories are providing the world-wide community with a wealth of data, covering wide time ranges (e.g. Solar and Heliospheric Observatory, SOHO), multiple viewpoints (Solar TErrestrial RElations Observatory, STEREO), and returning large amounts of data (Solar Dynamics Observatory, SDO). In particular, the large volume of SDO data presents challenges; the data are available only from a few repositories, and full-disk, full-cadence data for reasonable durations of scientific interest are difficult to download, due to their size and the download rates available to most users. From a scientist's perspective this poses three problems: accessing, browsing, and finding interesting data as efficiently as possible.
Aims: To address these challenges, we have developed JHelioviewer, a visualisation tool for solar data based on the JPEG 2000 compression standard and part of the open source ESA/NASA Helioviewer Project. Since the first release of JHelioviewer in 2009, the scientific functionality of the software has been extended significantly, and the objective of this paper is to highlight these improvements.
Methods: The JPEG 2000 standard offers useful new features that facilitate the dissemination and analysis of high-resolution image data and offers a solution to the challenge of efficiently browsing petabyte-scale image archives. The JHelioviewer software is open source, platform independent, and extendable via a plug-in architecture.
Results: With JHelioviewer, users can visualise the Sun for any time period between September 1991 and today; they can perform basic image processing in real time, track features on the Sun, and interactively overlay magnetic field extrapolations. The software integrates solar event data and a timeline display. Once an interesting event has been identified, science quality data can be accessed for in-depth analysis. As a first step towards supporting science planning of the upcoming Solar Orbiter mission, JHelioviewer offers a virtual camera model that enables users to set the vantage point to the location of a spacecraft or celestial body at any given time. Title: Future Mission Concepts for Helioseismology Authors: Sekii, Takashi; Appourchaux, Thierry; Fleck, Bernhard; Turck-Chièze, Sylvaine Bibcode: 2017hdsi.book..291S Altcode: No abstract at ADS Title: 20 Years of SOHO Authors: Fleck, Bernhard; Müller, Daniel Bibcode: 2016ENews..47c..27F Altcode: The Solar and Heliospheric Observatory (SOHO), a joint mission of ESA and NASA, has provided unparalleled insight into the Sun over the past 20 years - from its interior, through the hot and dynamic atmosphere, out to the solar wind and its interaction with the interstellar medium. SOHO also plays a vital role in forecasting potentially dangerous space weather situations by continuously monitoring solar storms, and unexpectedly also became the most prolific discoverer of comets in the history of astronomy. Title: Solar Science with the Atacama Large Millimeter/Submillimeter Array—A New View of Our Sun Authors: Wedemeyer, S.; Bastian, T.; Brajša, R.; Hudson, H.; Fleishman, G.; Loukitcheva, M.; Fleck, B.; Kontar, E. P.; De Pontieu, B.; Yagoubov, P.; Tiwari, S. K.; Soler, R.; Black, J. H.; Antolin, P.; Scullion, E.; Gunár, S.; Labrosse, N.; Ludwig, H. -G.; Benz, A. O.; White, S. M.; Hauschildt, P.; Doyle, J. G.; Nakariakov, V. M.; Ayres, T.; Heinzel, P.; Karlicky, M.; Van Doorsselaere, T.; Gary, D.; Alissandrakis, C. E.; Nindos, A.; Solanki, S. K.; Rouppe van der Voort, L.; Shimojo, M.; Kato, Y.; Zaqarashvili, T.; Perez, E.; Selhorst, C. L.; Barta, M. Bibcode: 2016SSRv..200....1W Altcode: 2015SSRv..tmp..118W; 2015arXiv150406887W The Atacama Large Millimeter/submillimeter Array (ALMA) is a new powerful tool for observing the Sun at high spatial, temporal, and spectral resolution. These capabilities can address a broad range of fundamental scientific questions in solar physics. The radiation observed by ALMA originates mostly from the chromosphere—a complex and dynamic region between the photosphere and corona, which plays a crucial role in the transport of energy and matter and, ultimately, the heating of the outer layers of the solar atmosphere. Based on first solar test observations, strategies for regular solar campaigns are currently being developed. State-of-the-art numerical simulations of the solar atmosphere and modeling of instrumental effects can help constrain and optimize future observing modes for ALMA. Here we present a short technical description of ALMA and an overview of past efforts and future possibilities for solar observations at submillimeter and millimeter wavelengths. In addition, selected numerical simulations and observations at other wavelengths demonstrate ALMA's scientific potential for studying the Sun for a large range of science cases. Title: ALMA Observations of the Sun in Cycle 4 and Beyond Authors: Wedemeyer, S.; Fleck, B.; Battaglia, M.; Labrosse, N.; Fleishman, G.; Hudson, H.; Antolin, P.; Alissandrakis, C.; Ayres, T.; Ballester, J.; Bastian, T.; Black, J.; Benz, A.; Brajsa, R.; Carlsson, M.; Costa, J.; DePontieu, B.; Doyle, G.; Gimenez de Castro, G.; Gunár, S.; Harper, G.; Jafarzadeh, S.; Loukitcheva, M.; Nakariakov, V.; Oliver, R.; Schmieder, B.; Selhorst, C.; Shimojo, M.; Simões, P.; Soler, R.; Temmer, M.; Tiwari, S.; Van Doorsselaere, T.; Veronig, A.; White, S.; Yagoubov, P.; Zaqarashvili, T. Bibcode: 2016arXiv160100587W Altcode: This document was created by the Solar Simulations for the Atacama Large Millimeter Observatory Network (SSALMON) in preparation of the first regular observations of the Sun with the Atacama Large Millimeter/submillimeter Array (ALMA), which are anticipated to start in ALMA Cycle 4 in October 2016. The science cases presented here demonstrate that a large number of scientifically highly interesting observations could be made already with the still limited solar observing modes foreseen for Cycle 4 and that ALMA has the potential to make important contributions to answering long-standing scientific questions in solar physics. With the proposal deadline for ALMA Cycle 4 in April 2016 and the Commissioning and Science Verification campaign in December 2015 in sight, several of the SSALMON Expert Teams composed strategic documents in which they outlined potential solar observations that could be feasible given the anticipated technical capabilities in Cycle 4. These documents have been combined and supplemented with an analysis, resulting in recommendations for solar observing with ALMA in Cycle 4. In addition, the detailed science cases also demonstrate the scientific priorities of the solar physics community and which capabilities are wanted for the next observing cycles. The work on this White Paper effort was coordinated in close cooperation with the two international solar ALMA development studies led by T. Bastian (NRAO, USA) and R. Brajsa, (ESO). This document will be further updated until the beginning of Cycle 4 in October 2016. In particular, we plan to adjust the technical capabilities of the solar observing modes once finally decided and to further demonstrate the feasibility and scientific potential of the included science cases by means of numerical simulations of the solar atmosphere and corresponding simulated ALMA observations. Title: SSALMON - The Solar Simulations for the Atacama Large Millimeter Observatory Network Authors: Wedemeyer, S.; Bastian, T.; Brajša, R.; Barta, M.; Hudson, H.; Fleishman, G.; Loukitcheva, M.; Fleck, B.; Kontar, E.; De Pontieu, B.; Tiwari, S.; Kato, Y.; Soler, R.; Yagoubov, P.; Black, J. H.; Antolin, P.; Gunár, S.; Labrosse, N.; Benz, A. O.; Nindos, A.; Steffen, M.; Scullion, E.; Doyle, J. G.; Zaqarashvili, T.; Hanslmeier, A.; Nakariakov, V. M.; Heinzel, P.; Ayres, T.; Karlicky, M. Bibcode: 2015AdSpR..56.2679W Altcode: 2015arXiv150205601W The Solar Simulations for the Atacama Large Millimeter Observatory Network (SSALMON) was initiated in 2014 in connection with two ALMA development studies. The Atacama Large Millimeter/submillimeter Array (ALMA) is a powerful new tool, which can also observe the Sun at high spatial, temporal, and spectral resolution. The international SSALMONetwork aims at co-ordinating the further development of solar observing modes for ALMA and at promoting scientific opportunities for solar physics with particular focus on numerical simulations, which can provide important constraints for the observing modes and can aid the interpretation of future observations. The radiation detected by ALMA originates mostly in the solar chromosphere - a complex and dynamic layer between the photosphere and corona, which plays an important role in the transport of energy and matter and the heating of the outer layers of the solar atmosphere. Potential targets include active regions, prominences, quiet Sun regions, flares. Here, we give a brief overview over the network and potential science cases for future solar observations with ALMA. Title: Future Mission Concepts for Helioseismology Authors: Sekii, Takashi; Appourchaux, Thierry; Fleck, Bernhard; Turck-Chièze, Sylvaine Bibcode: 2015SSRv..196..285S Altcode: 2015SSRv..tmp...15S Future space-mission concepts currently discussed in the helioseismology community are reviewed. One popular idea is to observe the Sun from high latitudes, to explore the polar regions as well as to probe the deep interior using stereoscopic techniques, by combining observations from high latitudes with observations from within the ecliptic plane. Another idea is to stay within the ecliptic plane but still aim for stereoscopic helioseismology for deep layers. A new instrument and a novel mission concept for studying the solar core regions are also discussed. Title: The 9 May 2016 transit of Mercury - a great outreach opportunity in Europe Authors: Rothery, D. A.; Benkhoff, J.; Zender, J.; Gill, R.; Fleck, B.; Doressoundiram, A. Bibcode: 2015EPSC...10..108R Altcode: People across most of the globe will have a chance to witness Mercury's next solar transit, 11:12-18:42 UT, Monday 9 May 2016. Occurring a year after the end of the MESSENGER mission and a few months before the launch of BepiColombo, this transit (the first since 2006) will be an ideal occasion to draw the public's attention to the science goals of those missions, to showcase what we have recently learned about Mercury, and to draw attention to the conundrums that make Mercury such a fascinating object to study. Title: A steady-state supersonic downflow in the transition region above a sunspot umbra Authors: Straus, Thomas; Fleck, Bernhard; Andretta, Vincenzo Bibcode: 2015A&A...582A.116S Altcode: 2015arXiv150704279S We investigate a small-scale (~1.5 Mm along the slit), supersonic downflow of about 90 km s-1 in the transition region above the lightbridged sunspot umbra in AR 11836. The observations were obtained with the Interface Region Spectrograph (IRIS) on 2013 September 2 from 16:40 to 17:59 UT. The downflow shows up as redshifted "satellite" lines of the Si iv and O iv transition region lines and is remarkably steady over the observing period of nearly 80 min. The downflow is not visible in the chromospheric lines, which only show an intensity enhancement at the location of the downflow. The density inferred from the line ratio of the redshifted satellites of the O iv lines (Ne = 1010.6 ± 0.25 cm-3) is only a factor 2 smaller than the one inferred from the main components (Ne = 1010.95 ± 0.20 cm-3). Consequently, this implies a substantial mass flux (~5 × 10-7 g cm-2 s-1), which would evacuate the overlying corona on timescales close to 10 s. We interpret these findings as evidence of a stationary termination shock of a supersonic siphon flow in a cool loop that is rooted in the central umbra of the spot.

The movie is available in electronic form at http://www.aanda.org Title: Solar and Galactic Cosmic Rays Observed by SOHO Authors: Fleck, Bernhard; Curdt, Werner; Olive, Jean-Philippe; van Overbeek, Ton Bibcode: 2015TESS....131009F Altcode: Both the Cosmic Ray Flux (CRF) and Solar Energetic Particles (SEPs) have left an imprint on SOHO technical systems. While the solar array efficiency degraded irreversibly down to 75% of its original level over 1 ½ solar cycles, Single Event Upsets (SEUs) in the solid state recorder (SSR) have been reversed by the memory protection mechanism. We compare the daily CRF observed by the Oulu station with the daily SOHO SEU rate and with the degradation curve of the solar arrays. The Oulu CRF and the SOHO SSR SEU rate are both modulated by the solar cycle and are highly correlated, except for sharp spikes in the SEU rate, caused by isolated SEP events, which also show up as discontinuities in the otherwise slowly decreasing solar ray efficiency. This allows to discriminate between effects with solar and non-solar origin and to compare the relative strength of both. We find that the total number of SSR SEUs with solar origin over the 17 ½ years from January 1996 through June 2013 is of the same order as those generated by cosmic ray hits. 49% of the total solar array degradation during that time can be attributed to proton events, i.e. the effect of a series of short-lived, violent events (SEPs) is comparable to the cycle-integrated damage by cosmic rays. Title: Observations of a Steady-State Supersonic Downflow in the Transition Region above a Sunspot Umbra Authors: Fleck, Bernhard; Straus, Thomas; Andretta, Vincenzo Bibcode: 2015TESS....120311F Altcode: Sunspots have been an area of intense research ever since Hale's discovery of strong magnetic fields in these structures. Here we report on the detection of a particular sunspot phenomenon: a small-scale (~ 1.5 Mm), supersonic downflow of about 90 km/s in the transition region above a light-bridged sunspot umbra. The observations were obtained with the Interface Imaging Region Spectrograph (IRIS) on 2 September 2013 from 16:39 to 17:58 UT in the sunspot of AR 11836 near disk center. Slit length and width were 68” and 0.166”, respectively. The cadence of the time series was 3 s, with exposure times of 2 s. The observations comprise nine spectral windows: C II 1336, Fe XII 1349, Cl I 1352, O I 1356, Si IV 1394, Si IV 1403, NUV at 2786 and 2831, and Mg II h and k 2796. The spectral window containing the Si IV 1403 line also includes the O IV 1400, 1401, and 1405 lines, the last one blended with a S IV line. The downflow shows up as red-shifted, well-separated “satellite” lines of the Si IV and O IV transition region lines and is remarkably steady over the observing period of nearly 80 min. The satellite lines do not participate in the 3-min shock wave Doppler maneuvres of the main component. The downflow is not visible in the chromospheric lines, which only show an intensity enhancement at the location of the downflow. The density inferred from the line ratio of the redshifted satellites of the O IV lines (Ne=1010.5 ±0.3 cm-3) is only a factor 2.5 smaller than the one inferred from the main components (Ne=1010.9 ±0.2 cm-3). Consequently, this implies a substantial mass flux (~ 4×10-7 g cm-2 s-1), which would evacuate the overlying corona on time scales of the order of 10 s. We interpret these findings as evidence of a stationary termination shock of a supersonic siphon flow in a cool loop rooted in the central umbra of the spot. Such stationary shocks have been predicted for siphon flows in hot coronal loops by Noci (1981). Title: Solar and Heliospheric Observatory (SOHO) (1995) Authors: Fleck, B.; St. Cyr, O. C. Bibcode: 2015hchp.book..159F Altcode: No abstract at ADS Title: Solar and Galactic Cosmic Rays Observed by SOHO Authors: Curdt, W.; Fleck, B. Bibcode: 2015CEAB...39..109C Altcode: 2015arXiv150507952C Both the Cosmic Ray Flux (CRF) and Solar Energetic Particles (SEPs) have left an imprint on SOHO technical systems. While the solar array efficiency degraded irreversibly down to ≈77% of its original level over roughly 1 1/2 solar cycles, Single Event Upsets (SEUs) in the solid state recorder (SSR) have been reversed by the memory protection mechanism. We compare the daily CRF observed by the Oulu station with the daily SOHO SEU rate and with the degradation curve of the solar arrays. The Oulu CRF and the SOHO SSR SEU rate are both modulated by the solar cycle and are highly correlated, except for sharp spikes in the SEU rate, caused by isolated SEP events, which also show up as discontinuities in the otherwise slowly decreasing solar ray efficiency. This allows to discriminate between effects with solar and non-solar origin and to compare the relative strength of both. We find that during solar cycle 23 (1996 Apr 1 -- 2008 Aug 31) only 6% of the total number of SSR SEUs were caused by SEPs; the remaining 94% were due to galactic cosmic rays. During the maximum period of cycle 23 (2000 Jan 1 -- 2003 Dec 31), the SEP contribution increased to 22%, and during 2001, the year with the highest SEP rate, to 30%. About 40% of the total solar array degradation during the 17 years from Jan 1996 through Feb 2013 can be attributed to proton events, i.e. the effect of a series of short-lived, violent SEP events is comparable to the cycle-integrated damage by cosmic rays. Title: Wave Propagation in the Internetwork Chromosphere: Comparing IRIS Observations of Mg II h and k with Simulations Authors: Fleck, B.; De Pontieu, B.; Leenaarts, J.; Pereira, T. M. D.; Straus, T. Bibcode: 2014AGUFMSH51C4174F Altcode: The objective of this study is to explore the dynamics of the upper internetwork chromosphere using high-resolution spectroscopic "sit-and-stare" time series obtained with the Interface Region Imaging Spectrogragh (IRIS) in the Mg II h and k lines. The Mg II h and k lines reveal a particularly complex spatio-temporal behavior, which strongly depends on the magnetic field topology. We focus on six parameters in both the h and k line: the Doppler shift and intensity of the central reversal (h3 and k3) and the blue and red emission peaks (h2v, h2r, k2v, k2r). In an effort to better understand what physical parameters can be extracted from these lines and to put our interpretation of the observations on more solid grounds, we extend our analysis to synthetic spectra obtained from numerical simulations and compare the results to the observations. Title: Interpreting the Helioseismic and Magnetic Imager (HMI) Multi-Height Velocity Measurements Authors: Nagashima, Kaori; Löptien, Björn; Gizon, Laurent; Birch, Aaron C.; Cameron, Robert; Couvidat, Sebastien; Danilovic, Sanja; Fleck, Bernhard; Stein, Robert Bibcode: 2014SoPh..289.3457N Altcode: 2014arXiv1404.3569N; 2014SoPh..tmp...84N The Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI) filtergrams, taken at six wavelengths around the Fe I 6173.3 Å line, contain information about the line-of-sight velocity over a range of heights in the solar atmosphere. Multi-height velocity inferences from these observations can be exploited to study wave motions and energy transport in the atmosphere. Using realistic convection-simulation datasets provided by the STAGGER and MURaM codes, we generate synthetic filtergrams and explore several methods for estimating Dopplergrams. We investigate at which height each synthetic Dopplergram correlates most strongly with the vertical velocity in the model atmospheres. On the basis of the investigation, we propose two Dopplergrams other than the standard HMI-algorithm Dopplergram produced from HMI filtergrams: a line-center Dopplergram and an average-wing Dopplergram. These two Dopplergrams correlate most strongly with vertical velocities at the heights of 30 - 40 km above (line center) and 30 - 40 km below (average wing) the effective height of the HMI-algorithm Dopplergram. Therefore, we can obtain velocity information from two layers separated by about a half of a scale height in the atmosphere, at best. The phase shifts between these multi-height Dopplergrams from observational data as well as those from the simulated data are also consistent with the height-difference estimates in the frequency range above the photospheric acoustic-cutoff frequency. Title: Helioseismic and Magnetic Imager Multi-height Dopplergrams Authors: Nagashima, Kaori; Gizon, Laurent; Birch, Aaron; Löptien, Björn; Couvidat, Sebastien; Fleck, Bernhard Bibcode: 2014arXiv1401.3182N Altcode: We study Doppler velocity measurements at multiple heights in the solar atmosphere using a set of six filtergrams obtained by the Helioseismic magnetic Imager on board the Solar Dynamics Observatory. There are clear and significant phase differences between core and wing Dopplergrams in the frequency range above the photospheric acoustic cutoff frequency, which indicates that these are really "multi-height" datasets. Title: Helioseismic and Magnetic Imager Multi-height Dopplergrams Authors: Nagashima, K.; Gizon, L.; Birch, A.; Löptien, B.; Couvidat, S.; Fleck, B. Bibcode: 2013ASPC..479..429N Altcode: We study Doppler velocity measurements at multiple heights in the solar atmosphere using a set of six filtergrams, obtained by the Helioseismic Magnetic Imager on board the Solar Dynamics Observatory. There are clear and significant phase differences between core and wing Dopplergrams in the frequency range above the photospheric acoustic cutoff frequency, which indicates that these are really “multi-height” datasets. Title: JHelioviewer: Visualization software for solar physics data Authors: Mueller, Daniel; Dimitoglou, George; Caplins, Benjamin; Garcia Ortiz, Juan Pablo; Wamsler, Benjamin; Hughitt, Keith; Alexanderian, Alen; Ireland, Jack; Amadigwe, Desmond; Fleck, Bernhard Bibcode: 2013ascl.soft08016M Altcode: 2013ascl.soft08016Y JHelioview is open source visualization software for solar physics data. The JHelioviewer client application enables users to browse petabyte-scale image archives; the JHelioviewer server integrates a JPIP server, metadata catalog, and an event server. JHelioview uses the JPEG 2000 image compression standard, which provides efficient access to petabyte-scale image archives; JHelioviewer also allows users to locate and manipulate specific data sets. Title: The Intensity-Velocity Phase Spectra of Evanescent Oscillations and Acoustic Sources Authors: Severino, G.; Straus, T.; Oliviero, M.; Steffen, M.; Fleck, B. Bibcode: 2013SoPh..284..297S Altcode: 2012SoPh..tmp..295S There are three major issues in modeling solar evanescent oscillations: the variation of the intensity [I]-velocity [V] phase difference of p-modes close to the base of photosphere; the existence of a plateau of negative I-V phase differences below and between the ridges of the low-frequency p-modes; the explanation of the I-V cross-spectra of the evanescent oscillations. We present new interpretations for the first two issues, based on modeling intensity fluctuations taking steep temperature gradients, opacity, and non-adiabatic cooling into account. Title: Extracting multi-height velocity information from SDO/HMI Dopplergrams Authors: Nagashima, Kaori; Gizon, Laurent; Birch, Aaron; Loeptien, Bjoern; Couvidat, Sebastien; Fleck, Bernhard; Stein, Robert Bibcode: 2013enss.confE..76N Altcode: Multi-height velocity information in the solar atmosphere is useful for many studies of the structure and dynamics of the solar atmosphere. We discuss the possibility of measuring the vertical velocity at multiple layers in the solar atmosphere using the six filtergrams of the Fe I 6173A absorption line obtained by SDO/HMI. In the standard HMI pipeline processing, these filtergrams are combined to estimate a single Doppler velocity. Here we construct three Dopplergrams by computing pair-wise differences between intensities in the blue and red wings of the line. We use realistic numerical simulations of convection to evaluate the range of heights that contribute to each of our multi-height velocity estimates. The cross-spectra of the Dopplergrams contain interesting information about vertical wave propagation in the solar atmosphere. Title: On the Effects of the SDO Orbital Motion on the HMI Vector Magnetic Field Measurements Authors: Fleck, B.; Centeno, R.; Cheung, M.; Couvidat, S.; Hayashi, K.; Rezaei, R.; Steiner, O.; Straus, T. Bibcode: 2013enss.confE.145F Altcode: In a previous study we have investigated the magnetic field diagnostics potential of SDO/HMI. We have used the output of high-resolution 3D, time-dependent, radiative magneto-hydrodynamics simulations to calculate Stokes profiles for the Fe I 6173 Å line. From these we constructed Stokes filtergrams using a representative set of HMI filter response functions. The magnetic field vector (x,y) and line-of-sight Doppler velocities V(x,y) were determined from these filtergrams using a simplified version of the HMI magnetic field processing pipeline, and the reconstructed magnetic field (x,y) and line-of-sight velocity V(x,y) were compared to the actual magnetic field (x,y,z) and vertical velocity V0(x,y,z) in the simulations. The present investigation expands this analysis to include the effects of the significant orbital motions of SDO, which, given the limited wavelength range of the HMI filter profiles, affects the outer wing measurements and therefore might impact the magnetic field measurements. We find that the effects of the orbital movement of SDO are noticeable, in particular for the strongest fields (B > 3 kG) and the maximum wavelength shift of 5.5 km/s (3.5 km/s orbital movement + 2 km/s solar rotation). Saturation effects for strong fields (B > 3 kG) are already visible for wavelength shifts of 3.2 km/s (orbital movement, disk center). The measurements of inclination and vertical velocity are more robust. Compared to other factors of uncertainty in the inversion of HMI Stokes measurements the orbital movement is not a major concern or source of error. Title: Preface Authors: Fleck, Bernhard; Heber, Bernd; Vourlidas, Angelos; van Driel-Gesztelyi, Lidia; Mandrini, Cristina H.; Leibacher, John Bibcode: 2012SoPh..281....1F Altcode: 2012SoPh..tmp..223F No abstract at ADS Title: On the Magnetic-Field Diagnostics Potential of SDO/HMI Authors: Fleck, B.; Hayashi, K.; Rezaei, R.; Vitas, N.; Centeno, R.; Cheung, M.; Couvidat, S.; Fischer, C.; Steiner, O.; Straus, T.; Viticchie, B. Bibcode: 2012decs.confE.104F Altcode: The Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) is designed to study oscillations and the magnetic field in the solar photosphere. It observes the full solar disk in the Fe I absorption line at 6173 Å. We use the output of three high-resolution 3D, time-dependent, radiative magneto-hydrodynamics simulations (two based on the MURaM code, one on the CO5BOLD code) to calculate Stokes profiles Fi(λ,x,y; i=I, V, Q, U) for the Fe I 6173 Å line for snapshots of a sunspot, a plage area and an enhanced network region. Stokes filtergrams are constructed for the 6 nominal HMI wavelengths by multiplying the Stokes profiles with a representative set of HMI filter response functions. The magnetic field vector B(x,y) and line-of-sight Doppler velocities V(x,y) are determined from these filtergrams using a simplified version of the HMI magnetic field processing pipeline. Finally, the reconstructed magnetic field B(x,y) and line-of-sight velocity V(x,y) are compared to the actual magnetic field B0(x,y,z) and vertical velocity V0(x,y,z) in the simulations. Title: On the Magnetic-Field Diagnostics Potential of SDO/HMI Authors: Fleck, B.; Hayashi, K.; Rezaei, R.; Vitas, N.; Centeno, R.; Couvidat, S.; Fischer, C.; Steiner, O.; Straus, T.; Viticchie, B. Bibcode: 2011sdmi.confE..74F Altcode: The Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) is designed to study oscillations and the magnetic field in the solar photosphere. It observes the full solar disk in the Fe I 6173 absorption line. We use the output of two high-resolution 3D, time-dependent, radiative magneto-hydrodynamics simulations (one based on the MURAM code, the other one on the COBOLD code) to calculate Stokes profiles for the Fe I 6173 line for a snapshot of a plage region and a snapshot of an enhanced network region. After spatially degrading the Stokes profiles to HMI resolution, they are multiplied by a representative set of HMI filter response functions and Stokes filtergrams are constructed for the 6 nominal HMI wavelengths. The magnetic field vector and line-of-sight Doppler velocities are determined from these filtergrams using a simplified version of the HMI magnetic field processing pipeline. Finally, the reconstructed magnetic field is compared to the actual magnetic field in the simulation. Title: On the Formation Height of the SDO/HMI Fe 6173 Å Doppler Signal Authors: Fleck, B.; Couvidat, S.; Straus, T. Bibcode: 2011SoPh..271...27F Altcode: 2011SoPh..tmp..242F; 2011arXiv1104.5166F; 2011SoPh..tmp..117F; 2011SoPh..tmp..173F The Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) is designed to study oscillations and the magnetic field in the solar photosphere. It observes the full solar disk in the Fe I absorption line at 6173 Å. We use the output of a high-resolution, 3D, time-dependent, radiation-hydrodynamic simulation based on the CO5BOLD code to calculate profiles F(λ,x,y,t) for the Fe I 6173 Å line. The emerging profiles F(λ,x,y,t) are multiplied by a representative set of HMI filter-transmission profiles Ri(λ, 1≤i≤6) and filtergrams Ii(x,y,t; 1≤i≤6) are constructed for six wavelengths. Doppler velocities VHMI(x,y,t) are determined from these filtergrams using a simplified version of the HMI pipeline. The Doppler velocities are correlated with the original velocities in the simulated atmosphere. The cross-correlation peaks near 100 km, suggesting that the HMI Doppler velocity signal is formed rather low in the solar atmosphere. The same analysis is performed for the SOHO/MDI Ni I line at 6768 Å. The MDI Doppler signal is formed slightly higher at around 125 km. Taking into account the limited spatial resolution of the instruments, the apparent formation height of both the HMI and MDI Doppler signal increases by 40 to 50 km. We also study how uncertainties in the HMI filter-transmission profiles affect the calculated velocities. Title: The Helioviewer Project: Solar Data Visualization and Exploration Authors: Hughitt, V. Keith; Ireland, J.; Müller, D.; García Ortiz, J.; Dimitoglou, G.; Fleck, B. Bibcode: 2011SPD....42.1517H Altcode: 2011BAAS..43S.1517H SDO has only been operating a little over a year, but in that short time it has already transmitted hundreds of terabytes of data, making it impossible for data providers to maintain a complete archive of data online. By storing an extremely efficiently compressed subset of the data, however, the Helioviewer project has been able to maintain a continuous record of high-quality SDO images starting from soon after the commissioning phase. The Helioviewer project was not designed to deal with SDO alone, however, and continues to add support for new types of data, the most recent of which are STEREO EUVI and COR1/COR2 images. In addition to adding support for new types of data, improvements have been made to both the server-side and client-side products that are part of the project. A new open-source JPEG2000 (JPIP) streaming server has been developed offering a vastly more flexible and reliable backend for the Java/OpenGL application JHelioviewer. Meanwhile the web front-end, Helioviewer.org, has also made great strides both in improving reliability, and also in adding new features such as the ability to create and share movies on YouTube. Helioviewer users are creating nearly two thousand movies a day from the over six million images that are available to them, and that number continues to grow each day. We provide an overview of recent progress with the various Helioviewer Project components and discuss plans for future development. Title: Helioviewer: Simplifying Your Access to SDO Data Authors: Hughitt, V. K.; Ireland, J.; Mueller, D.; Beck, J.; Lyon, D.; Dau, A.; Dietert, H.; Nuhn, M.; Dimitoglou, G.; Fleck, B. Bibcode: 2010AGUFMSH23C1868H Altcode: Over the past several years, the Helioviewer Project has evolved from a simple web application to display images of the sun into a suite of tools to visualize and interact with heterogeneous types of solar data. In addition to a modular and scalable back-end server, the Helioviewer Project now offers multiple browse clients; the original web application has been upgraded to support high-definition movie generation and feature and event overlays. For complex image processing and massive data volumes, there is a stand-alone desktop application, JHelioviewer. For a quick check of the latest images and events, there is an iPhone application, hqTouch. The project has expanded from the original SOHO images to include image data from SDO and event and feature data from the HEK. We are working on adding additional image data from other missions as well as spectral and time-series data. We will discuss the procedure through which interested parties may process their data for use with Helioviewer, including how to use JP2Gen to convert FITS files into Helioviewer-compliant JPEG 2000 images, how to setup a local instance of the Helioviewer server, and how to query Helioviewer in your own applications using a simple web API. Title: Estimating the Energy Flux of Acoustic-Gravity Waves in the Solar Atmosphere from SDO/HMI Data Authors: Fleck, B.; Straus, T.; Jefferies, S.; Scherrer, P. Bibcode: 2010AGUFMSH11A1602F Altcode: Straus et al. (2008, 2009) demonstrated the existence of internal gravity waves in the solar atmosphere and showed that they are a key mediator of mechanical energy in the middle/upper photosphere, transporting even more energy than high-frequency acoustic waves. Here we repeat this analysis with data from SDO/HMI, which offers several distinct advantages, which are particularly relevant for the study of internal gravity waves (which have long periods and small spatial scales): excellent image stability over long time intervals, high spatial resolution, large field-of-view, and good temporal cadence. Title: JHelioviewer: Open-Source Software for Discovery and Image Access in the Petabyte Age (Invited) Authors: Mueller, D.; Dimitoglou, G.; Langenberg, M.; Pagel, S.; Dau, A.; Nuhn, M.; Garcia Ortiz, J. P.; Dietert, H.; Schmidt, L.; Hughitt, V. K.; Ireland, J.; Fleck, B. Bibcode: 2010AGUFMSH22A..05M Altcode: The unprecedented torrent of data returned by the Solar Dynamics Observatory is both a blessing and a barrier: a blessing for making available data with significantly higher spatial and temporal resolution, but a barrier for scientists to access, browse and analyze them. With such staggering data volume, the data is bound to be accessible only from a few repositories and users will have to deal with data sets effectively immobile and practically difficult to download. From a scientist's perspective this poses three challenges: accessing, browsing and finding interesting data while avoiding the proverbial search for a needle in a haystack. To address these challenges, we have developed JHelioviewer, an open-source visualization software that lets users browse large data volumes both as still images and movies. We did so by deploying an efficient image encoding, storage, and dissemination solution using the JPEG 2000 standard. This solution enables users to access remote images at different resolution levels as a single data stream. Users can view, manipulate, pan, zoom, and overlay JPEG 2000 compressed data quickly, without severe network bandwidth penalties. Besides viewing data, the browser provides third-party metadata and event catalog integration to quickly locate data of interest, as well as an interface to the Virtual Solar Observatory to download science-quality data. As part of the Helioviewer Project, JHelioviewer offers intuitive ways to browse large amounts of heterogeneous data remotely and provides an extensible and customizable open-source platform for the scientific community. Title: Adiabatic high degree modes of a rotating star. I. General features and real pressure modes Authors: Schmitz, F.; Fleck, B. Bibcode: 2010A&A...515A.103S Altcode:
Aims: The influence of the rotation of the Sun on non-radial p-modes with high wave numbers l is studied. To investigate and understand the basic properties of these modes, it is sufficient to consider only the outer layers of the Sun, which can be approximated by a plane layer with constant gravity.
Methods: We use a model with a smooth transition between a polytropic convection zone and an isothermal atmosphere. The rotation is simulated by a constant horizontal wind. For this model, using the column mass instead of the geometrical height, the adiabatic wave equation of the pressure perturbation can be reduced to Whittaker's differential equation. From boundary conditions we obtain the dispersion relation. The geometrical height is a simple elementary function of the column mass.
Results: The dispersion relation F(ω, k) = 0 is a higher order algebraic equation in both frequency and horizontal wave number, which must be solved numerically. We analyze the behavior of the dispersion curves of modes with an adiabatic exponent γ = 5/3 for layers with polytropic indices n = 3 and n = 3/2. The f-mode is considered separately. For the understanding of the results we also consider modes of a homogeneous gas. We compare the k - ω diagram of our idealized model with the k - ω diagram of a real solar model.

Dedicated to Franz-Ludwig Deubner, who celebrated his 75th birthday on June 2, 2009. Title: The Signature of Flares in VIRGO Total Solar Irradiance Measurements Authors: Quesnel, A.; Dennis, B. R.; Fleck, B.; Fröhlich, C.; Hudson, H. S.; Tolbert, A. K. Bibcode: 2010ASPC..428..133Q Altcode: 2010arXiv1003.4194Q We use Total Solar Irradiance (TSI) measurements from the VIRGO (Variability of solar Irradiance and Gravity Oscillations) instrument on board SOHO to obtain preliminary estimates of the mean total radiative energy emitted by X-class solar flares. The basic tool is that of summed-epoch analysis, which has also enabled us to detect and partially characterize systematic errors present in the basic data. We describe these errors, which significantly degrade the photometry at high frequencies. We find the ratio of GOES 1-8 Å luminosity to total bolometric luminosity to be of order 0.01. Title: JHelioviewer: Taming The Torrent Of SDO Data Authors: Mueller, Daniel; Langenberg, M.; Pagel, S.; Schmidt, L.; Garcia Ortiz, J. P.; Dimitoglou, G.; Hughitt, V. K.; Ireland, J.; Fleck, B. Bibcode: 2010AAS...21640224M Altcode: 2010BAAS...41..877M Space missions generate an ever-growing amount of data, as impressively highlighted by the Solar Dynamics Observatory's (SDO) expected return of 1.4 TByte/day. In order to fully exploit their data, scientists need to be able to browse and visualize many different data products spanning a large range of physical length and time scales. So far, the tools available to the scientific community either require downloading all potentially relevant data sets beforehand in their entirety or provide only movies with a fixed resolution and cadence. For SDO, the former approach is prohibitive due to the shear data volume, while the latter does not do justice to the high resolution and cadence of the images. To address this challenge, we have developed JHelioviewer, a JPEG 2000-based visualization and discovery software for solar image data. Using the very efficient lossy compression mode of JPEG 2000, a full-size SDO image can be compressed to 1 MByte at good visual quality for browsing purposes. JHelioviewer will make the vast amount of SDO images available to the worldwide community in this format, which is already being used for all SOHO images. JHelioviewer is a cross-platform application that offers movie streaming, real-time frame-by-frame image processing, feature/event overlays and will enable users to access SDO science data via a VSO interface. JHelioviewer uses the JPEG 2000 Interactive Protocol (JPIP) and OpenGL. The random code stream access of JPIP minimizes data transfer by streaming image data in a region-of-interest and quality-progressive way, while OpenGL enables rapid hardware-accelerated image processing and rendering. Currently focused on solar physics data, JHelioviewer can easily be adapted for use in other areas of space and earth sciences. This poster will illustrate the new and expanded functionality of JHelioviewer and highlight the advantages of JPEG 2000 as a new compression standard for solar image data. Title: The Helioviewer Project: Browsing, Visualizing and Accessing Petabytes of Solar Data Authors: Mueller, Daniel; Hughitt, V. K.; Langenberg, M.; Ireland, J.; Pagel, S.; Schmidt, L.; Garcia Ortiz, J. P.; Dimitoglou, G.; Fleck, B. Bibcode: 2010AAS...21640223M Altcode: 2010BAAS...41..876M After its successful launch, NASA's Solar Dynamics Observatory (SDO) will soon return more than 1 Terabyte worth of images per day. This unprecedented torrent of data will pose an entirely new set of challenges with respect to data access, data browsing and searching for interesting data while avoiding the proverbial search for "a needle in a haystack". In order to fully exploit SDO's wealth of data and connect it to data from other solar missions like SOHO, scientists need to be able to interactively browse and visualize many different data products spanning a large range of physical length and time scales. So far, all tools available to the scientific community either require downloading all potentially relevant data sets beforehand in their entirety or provide only movies with a fixed resolution and cadence. The Helioviewer project offers a solution to these challenges by providing a suite of tools that are based on the new JPEG 2000 compression standard and enable scientists and the general public alike to intuitively browse visualize and access petabytes of image data remotely:

- JHelioviewer, a cross-platform application that offers movie streaming and real-time processing using the JPEG 2000 Interactive Protocol (JPIP) and OpenGL, as well as feature/event overlays.

- helioviewer.org, a web-based image and feature/event browser.

- Server-side services to stream movies of arbitrary spatial and temporal resolution in a region-of-interest and quality-progressive form, a JPEG 2000 image database and a feature/event server. All the services can be accessed through well-documented interfaces (APIs).

- Code to convert images into JPEG 2000 format.

This presentation will give an overview of the Helioviewer Project, illustrate new features and highlight the advantages of JPEG 2000 as a data format for solar physics that has the potential to revolutionize the way high-resolution image data are disseminated and analyzed. Title: Solar Mashups: Interacting With, Extending, And Embedding Helioviewer.org And Jhelioviewer Authors: Hughitt, V. Keith; Ireland, J.; Müller, D.; Langenberg, M.; Pagel, S.; Schmidt, L.; Harper, J.; Dimitoglou, G.; Fleck, B. Bibcode: 2010AAS...21640225H Altcode: 2010BAAS...41..877H Helioviewer.org is a JPEG 2000-driven web application for searching and displaying heterogeneous solar data sets, including both image and catalog information. Helioviewer.org has been written from the ground up with extensibility in mind. The result of this effort is a rich Application Programming Interface (API) from which third-party applications can interact with Helioviewer.org. In addition to being able to launch Helioviewer.org with a specified state (by giving it a time and a set of instruments, wavelengths, etc), it is also possible to generate composite images and movies, and to search for catalog data from the Heliophysics Event Knowledgebase (HEK). We are developing our software so that you will be able to embed instances of Helioviewer.org in your own web pages, in much the same way that it is now possible to embed Google Maps (tm) into any webpage. This will make it very easy to overlay your data with that provided by the Helioviewer Project. JHelioviewer, Helioviewer.org's Java-based counterpart, shares many of the same features as Helioviewer.org, but also offers some new ones when it comes to extensibility, including a custom plugin architecture that supports custom image filters, overlay layers, GUI components, and more. Both of the projects are free to use and completely open-source, and anyone is welcome to contribute to their development. Title: High frequency waves in the solar atmosphere?. Authors: Fleck, B.; Straus, T.; Carlsson, M.; Jefferies, S. M.; Severino, G.; Tarbell, T. D. Bibcode: 2010MmSAI..81..777F Altcode: 2010arXiv1002.3285F The present study addresses the following questions: How representative of the actual velocities in the solar atmosphere are the Doppler shifts of spectral lines? How reliable is the velocity signal derived from narrowband filtergrams? How well defined is the height of the measured Doppler signal? Why do phase difference spectra always pull to 0o phase lag at high frequencies? Can we actually observe high frequency waves (P< 70 s)? What is the atmospheric MTF of high frequency waves? How reliably can we determine the energy flux of high frequency waves? We address these questions by comparing observations obtained with Hinode/NFI with results from two 3D numerical simulations (Oslo Stagger and CO5BOLD). Our results suggest that the observed high frequency Doppler velocity signal is caused by rapid height variations of the velocity response function in an atmosphere with strong velocity gradients and cannot be interpreted as evidence of propagating high frequency acoustic waves. Estimates of the energy flux of high frequency waves should be treated with caution, in particular those that apply atmospheric MTF corrections. Title: On the detection of fast moving upflows in the quiet solar photosphere. Authors: Straus, Th.; Fleck, B.; Jefferies, S. M.; Carlsson, M.; Tarbell, T. D. Bibcode: 2010MmSAI..81..751S Altcode: 2010arXiv1002.3305S In our studies of the dynamics and energetics of the solar atmosphere, we have detected, in high-quality observations from Hinode SOT/NFI, ubiquitous small-scale upflows which move horizontally with supersonic velocities in the quiet Sun. We present the properties of these fast moving upflows (FMUs) and discuss different interpretations. Title: JHelioviewer: Exploring Petabytes of Solar Images Authors: Mueller, Daniel; Fleck, Bernhard; Dimitoglou, George; Garcia Ortiz, Juan Pablo; Schmidt, Ludwig; Hughitt, Keith; Ireland, Jack Bibcode: 2010cosp...38.2880M Altcode: 2010cosp.meet.2880M Space missions generate an ever-growing amount of data, as impressively highlighted by the Solar Dynamics Observatory's (SDO) expected return of 1.4 TByte/day. In order to fully ex-ploit their data, scientists need to be able to browse and visualize many different data products spanning a large range of physical length and time scales. So far, the tools available to the scientific community either require downloading all potentially relevant data sets beforehand in their entirety or provide only movies with a fixed resolution and cadence. For SDO, the former approach is prohibitive due to the shear data volume, while the latter does not do justice to the high resolution and cadence of the images. To address this challenge, we have developed JHelioviewer, a JPEG 2000-based visualization and discovery software for solar image data. JHelioviewer makes the vast amount of SDO images available to the worldwide community, lets users browse more than 14 years worth of images from the Solar and Heliospheric Observatory (SOHO) and facilitates browsing and analysis of complex time-dependent data sets from mul-tiple sources in general. The user interface for JHelioviewer is a multi-platform Java client that communicates with a remote server via the JPEG 2000 interactive protocol JPIP. The random code stream access of JPIP minimizes data transfer and can encapsulate metadata as well as multiple image channels in one data stream. This presentation will illustrate the features of JHelioviewer and highlight the advantages of JPEG 2000 as a new data compression standard. Title: On the Role of Acoustic-Gravity Waves in the Energetics of the Solar Atmosphere Authors: Straus, T.; Fleck, B.; Jefferies, S. M.; McIntosh, S. W.; Severino, G.; Steffen, M.; Tarbell, T. D. Bibcode: 2009ASPC..415...95S Altcode: 2010arXiv1003.3773S In a recent paper (Straus et al. 2008) we determined the energy flux of internal gravity waves in the lower solar atmosphere using a combination of 3D numerical simulations and observations obtained with the IBIS instrument operated at the Dunn Solar Telescope and the Michelson Doppler Imager (MDI) on SOHO. In this paper we extend these studies using coordinated observations from SOT/NFI and SOT/SP on Hinode and MDI. The new measurements confirm that gravity waves are the dominant phenomenon in the quiet middle/upper photosphere and that they transport more mechanical energy than the high-frequency (> 5 mHz) acoustic waves, even though we find an acoustic flux 3-5 times larger than the upper limit estimate of Fossum & Carlsson (2006). It therefore appears justified to reconsider the significance of (non-M)HD waves for the energy balance of the solar chromosphere. Title: Helioviewer.org: Browsing Very Large Image Archives Online Using JPEG 2000 Authors: Hughitt, V. K.; Ireland, J.; Mueller, D.; Dimitoglou, G.; Garcia Ortiz, J.; Schmidt, L.; Wamsler, B.; Beck, J.; Alexanderian, A.; Fleck, B. Bibcode: 2009AGUFMSH51B1279H Altcode: As the amount of solar data available to scientists continues to increase at faster and faster rates, it is important that there exist simple tools for navigating this data quickly with a minimal amount of effort. By combining heterogeneous solar physics datatypes such as full-disk images and coronagraphs, along with feature and event information, Helioviewer offers a simple and intuitive way to browse multiple datasets simultaneously. Images are stored in a repository using the JPEG 2000 format and tiled dynamically upon a client's request. By tiling images and serving only the portions of the image requested, it is possible for the client to work with very large images without having to fetch all of the data at once. In addition to a focus on intercommunication with other virtual observatories and browsers (VSO, HEK, etc), Helioviewer will offer a number of externally-available application programming interfaces (APIs) to enable easy third party use, adoption and extension. Recent efforts have resulted in increased performance, dynamic movie generation, and improved support for mobile web browsers. Future functionality will include: support for additional data-sources including RHESSI, SDO, STEREO, and TRACE, a navigable timeline of recorded solar events, social annotation, and basic client-side image processing. Title: JHelioviewer: Visualizing Large Sets of Solar Images Using JPEG 2000 Authors: Muller, D.; Fleck, B.; Dimitoglou, G.; Caplins, B. W.; Amadigwe, D. E.; García Ortiz, J. P.; Wamsler, B.; Alexanderian, A.; Hughitt, V. K.; Ireland, J. Bibcode: 2009CSE....11...38M Altcode: 2009arXiv0906.1582M All disciplines that work with image data-from astrophysics to medical research and historic preservation-increasingly require efficient ways to browse and inspect large sets of high-resolution images. Based on the JPEG 2000 image-compression standard, the JHelioviewer solar image visualization tool lets users browse petabyte-scale image archives as well as locate and manipulate specific data sets. Title: A Novel Approach to Discovery and Access to Solar Data in the Petabyte Age Authors: Mueller, Daniel; Dimitoglou, G.; Hughitt, V. K.; Ireland, J.; Wamsler, B.; Fleck, B. Bibcode: 2009SPD....40.1706M Altcode: Space missions generate an ever-growing amount of data, as impressively highlighted by SDO's expected data rate of 1.4 TByte/day. In order to fully exploit their data, scientists need to be able to browse and visualize many different data products spanning a large range of physical length and time scales. So far, the tools available to the scientific community either require downloading all potentially relevant data sets beforehand in their entirety or provide only movies with a fixed resolution and cadence. To facilitate browsing and analysis of complex time-dependent data sets from multiple sources, we are developing JHelioviewer, a JPEG 2000-based visualization and discovery infrastructure for solar image data. Together with its web-based counterpart helioviewer.org, JHelioviewer offers intuitive ways to browse large amounts of heterogeneous data remotely and allows users to search related event data bases. The user interface for JHelioviewer is a multi-platform Java client that can both communicate with a remote server via the JPEG 2000 interactive protocol JPIP and open local data. The random code stream access of JPIP minimizes data transfer and can encapsulate meta data as well as multiple image channels in one data stream. This presentation will illustrate some of the features of JHelioviewer and the advantages of JPEG 2000 as a new data compression standard. Title: Helioviewer.org: An Open-source Tool for Visualizing Solar Data Authors: Hughitt, V. Keith; Ireland, J.; Schmiedel, P.; Dimitoglou, G.; Mueller, D.; Fleck, B. Bibcode: 2009SPD....40.1502H Altcode: As the amount of solar data available to scientists continues to increase at faster and faster rates, it is important that there exist simple tools for navigating this data quickly with a minimal amount of effort. By combining heterogeneous solar physics datatypes such as full-disk images and coronagraphs, along with feature and event information, Helioviewer offers a simple and intuitive way to browse multiple datasets simultaneously. Images are stored in a repository using the JPEG 2000 format and tiled dynamically upon a client's request. By tiling images and serving only the portions of the image requested, it is possible for the client to work with very large images without having to fetch all of the data at once. Currently, Helioviewer enables users to browse the entire SOHO data archive, updated hourly, as well as data feature/event catalog data from eight different catalogs including active region, flare, coronal mass ejection, type II radio burst data. In addition to a focus on intercommunication with other virtual observatories and browsers (VSO, HEK, etc), Helioviewer will offer a number of externally-available application programming interfaces (APIs) to enable easy third party use, adoption and extension. Future functionality will include: support for additional data-sources including TRACE, SDO and STEREO, dynamic movie generation, a navigable timeline of recorded solar events, social annotation, and basic client-side image processing. Title: The Helioviewer Project: Discovery For Everyone Everywhere Authors: Ireland, Jack; Hughitt, K.; Müller, D.; Dimitoglou, G.; Schmiedel, P.; Fleck, B. Bibcode: 2009SPD....40.1501I Altcode: The Helioviewer Project: discovery for everyone everywhere There is an ever increasing amount of solar and heliospheric data gathered from multiple sources such as space-based facilities and ground based observatories. There are also multiple feature and event catalogs arising from human and computer based detection methods. The Helioviewer Project is developing a suite of technologies to allow users around the world to visualize, browse and access these heterogeneous datasets in an intuitive and highly customizable fashion.

Helioviewer technologies are based on the JPEG2000 file format, an extremely flexible format that allows for the efficient transfer of data (and meta-data, such as FITS keywords) between client and server. Rather then having to download an entire image and then examine the small portion- for example, an active region - that you are interested in, the JPEG2000 file format lets you preferentially download only those portions you are interested in. This dramatically reduces the amount of data transferred, making possible responsive and flexible scientific discovery applications that can browse populous archives of large images, such as those from the Solar Dynamics Observatory.

In addition, the Helioviewer Project is designed to be flexible and extensible to data sources as they become available. Helioviewer.org (www.helioviewer.org) works seamlessly with the Virtual Solar Observatory (VSO) whilst an application programming interface (API) is being developed for interaction with the Solar Dynamics Observatory Heliophysics Event Knowledgebase.

After a short introduction to the underlying technology, a live demonstration of the web application www.helioviewer.org will be given. We will also comment on other client applications (Jhelioviewer, a Java-based browse tool), and the application of Helioviewer technology to existing and future solar and heliospheric data and feature/event repositories. This project is funded by NASA VxO and LWS awards and an ESA science award. Title: Helioviewer: A Web 2.0 Tool for Visualizing Heterogeneous Heliophysics Data Authors: Hughitt, V. K.; Ireland, J.; Lynch, M. J.; Schmeidel, P.; Dimitoglou, G.; Müeller, D.; Fleck, B. Bibcode: 2008AGUFMSM11B1617H Altcode: Solar physics datasets are becoming larger, richer, more numerous and more distributed. Feature/event catalogs (describing objects of interest in the original data) are becoming important tools in navigating these data. In the wake of this increasing influx of data and catalogs there has been a growing need for highly sophisticated tools for accessing and visualizing this wealth of information. Helioviewer is a novel tool for integrating and visualizing disparate sources of solar and Heliophysics data. Taking advantage of the newly available power of modern web application frameworks, Helioviewer merges image and feature catalog data, and provides for Heliophysics data a familiar interface not unlike Google Maps or MapQuest. In addition to streamlining the process of combining heterogeneous Heliophysics datatypes such as full-disk images and coronagraphs, the inclusion of visual representations of automated and human-annotated features provides the user with an integrated and intuitive view of how different factors may be interacting on the Sun. Currently, Helioviewer offers images from The Extreme ultraviolet Imaging Telescope (EIT), The Large Angle and Spectrometric COronagraph experiment (LASCO) and the Michelson Doppler Imager (MDI) instruments onboard The Solar and Heliospheric Observatory (SOHO), as well as The Transition Region and Coronal Explorer (TRACE). Helioviewer also incorporates feature/event information from the LASCO CME List, NOAA Active Regions, CACTus CME and Type II Radio Bursts feature/event catalogs. The project is undergoing continuous development with many more data sources and additional functionality planned for the near future. Title: Preface: SOHO 20 - Transient events on the Sun and in the heliosphere Authors: Robbrecht, E.; Hochedez, J. -F.; Fleck, B.; Gurman, J.; Forsyth, R. Bibcode: 2008AnGeo..26.2953R Altcode: No abstract at ADS Title: High Frequency Acoustic Waves in the Sun's Atmosphere Authors: Fleck, B.; Jefferies, S. M.; McIntosh, S. W.; Severino, G.; Straus, T.; Tarbell, T. D. Bibcode: 2008ESPM...12.2.39F Altcode: This year marks the 60th anniversary of two pioneering papers by Schwarzschild (1948) and Biermann (1948), who independently proposed that acoustic waves generated in the turbulent convection zone play an important role in the heating of the chromosphere and corona. High frequency acoustic waves have remained one of the leading contenders for solving the heating problem of the non-magnetic chromospheres of the Sun and late-type stars ever since. Earlier attempts to determine the acoustic energy flux from ground were compromised by atmospheric seeing, which has its biggest effect on the high frequency parts of the observed signal. Recently, based on a comparison of TRACE observations and 1-D simulations, Fossum & Carlsson (2005, 2006) concluded that high-frequency acoustic waves are not sufficient to heat the solar chromosphere. The same conclusion was reached by Carlsson et al. (2007) from an analysis of Hinode SOT/BFI Ca II H and blue continuum observations. Other authors (e.g. Cuntz et al. 2007; Wedemeyer-Boehm et al. 2007, Kalkofen 2007), however, questioned these results for a number of reasons. Because of its limited spatial resolution and limited sensitivity there are inherent difficulties when comparing TRACE observations with numerical simulations. Further, intensity oscillations are difficult to interpret, as they result from a phase-sensitive mix of temperature and pressure fluctuations, and non-local radiation transfer effects may complicate the picture even more. Here we revisit the role of high frequency acoustic waves in the dynamics and energetics of the Sun's atmosphere using high cadence, high resolution Doppler velocity measurements obtained with SOT/SP and SOT/NFI on Hinode. Title: On the Role of Acoustic-gravity Waves in the Energetics of the Solar Atmosphere Authors: Straus, T.; Fleck, B.; Jefferies, S. M.; Cauzzi, G.; McIntosh, S. W.; Reardon, K.; Severino, G.; Steffen, M.; Suter, M.; Tarbell, T. D. Bibcode: 2008ESPM...12.2.11S Altcode: We revisit the dynamics and energetics of the solar atmosphere, using a combination of high-quality observations and 3D numerical simulations of the overshoot region of compressible convection into the stable photosphere. We discuss the contribution of acoustic-gravity waves to the energy balance of the photosphere and low chromosphere. We demonstrate the presence of propagating internal gravity waves at low frequencies (< 5mHz). Surprisingly, these waves are found to be the dominant phenomenon in the quiet middle/upper photosphere and to transport a significant amount of mechanical energy into the atmosphere outweighing the contribution of high-frequency (> 5mHz) acoustic waves by more than an order of magnitude. We compare the properties of high-frequency waves in the simulations with results of recent high cadence, high resolution Doppler velocity measurements obtained with SOT/SP and SOT/NFI on Hinode. Our results seem to be in conflict with the simple picture of upward propagating sound waves. We discuss the implications of our findings on the energy flux estimate at high-frequencies. Title: The Energy Flux of Internal Gravity Waves in the Lower Solar Atmosphere Authors: Straus, Thomas; Fleck, Bernhard; Jefferies, Stuart M.; Cauzzi, Gianna; McIntosh, Scott W.; Reardon, Kevin; Severino, Giuseppe; Steffen, Matthias Bibcode: 2008ApJ...681L.125S Altcode: Stably stratified fluids, such as stellar and planetary atmospheres, can support and propagate gravity waves. On Earth these waves, which can transport energy and momentum over large distances and can trigger convection, contribute to the formation of our weather and global climate. Gravity waves also play a pivotal role in planetary sciences and modern stellar physics. They have also been proposed as an agent for the heating of stellar atmospheres and coronae, the exact mechanism behind which is one of the outstanding puzzles in solar and stellar physics. Using a combination of high-quality observations and 3D numerical simulations we have the first unambiguous detection of propagating gravity waves in the Sun's (and hence a stellar) atmosphere. Moreover, we are able to determine the height dependence of their energy flux and find that at the base of the Sun's chromosphere it is around 5 kW m-2. This amount of energy is comparable to the radiative losses of the entire chromosphere and points to internal gravity waves as a key mediator of energy into the solar atmosphere. Title: High Frequency Acoustic Waves in the Sun's Atmosphere Authors: Fleck, B.; Jefferies, S. M.; McIntosh, S. W.; Straus, T.; Tarbell, T. D. Bibcode: 2008AGUSMSP41B..04F Altcode: This year marks the 60th anniversary of two pioneering papers by Schwarzschild (1948) and Biermann (1948), who independently proposed that acoustic waves generated in the turbulent convection zone play an important role in the heating of the chromosphere and corona. High frequency acoustic waves have remained one of the leading contenders for solving the heating problem of the non-magnetic chromospheres of the Sun and late-type stars ever since. Earlier attempts to determine the acoustic energy flux from ground were compromised by atmospheric seeing, which has its biggest effect on the high frequency parts of the observed signal. Recently, based on a comparison of TRACE observations and 1-D simulations, Fossum & Carlsson (2005, 2006) concluded that high-frequency acoustic waves are not sufficient to heat the solar chromosphere. The same conclusion was reached by Carlsson et al. (2007) from an analysis of Hinode SOT/BFI Ca II H and blue continuum observations. Other authors (e.g. Cuntz et al. 2007; Wedemeyer-Boehm et al. 2007, Kalkofen 2007), however, questioned these results for a number of reasons. Because of its limited spatial resolution and limited sensitivity there are inherent difficulties when comparing TRACE observations with numerical simulations. Further, intensity oscillations are difficult to interpret, as they result from a phase-sensitive mix of density, temperature, and pressure fluctuations, and radiation transfer effects may complicate the picture even more. Here we revisit the role of high frequency acoustic waves in the Sun's atmosphere using high cadence, high resolution Doppler velocity measurements obtained with SOT/SP and SOT/NFI on Hinode. Title: Solar Orbiter: A Mission Update Authors: Marsden, R. G.; Fleck, B. Bibcode: 2007ASPC..368..645M Altcode: The Solar Orbiter Mission will study the Sun in greater detail than ever before due the close proximity of the spacecraft as it orbits the Sun. At its closest point, Solar Orbiter will be about 0.22 AU from the Sun, closer than any other satellite to date. In addition to providing high-resolution images of the solar surface, perihelion passes at these distances occur in near co-rotation with the Sun, allowing the instruments to track features on the surface for several days. The mission profile also includes a high-latitude phase that will allow observations from up to 35° above the solar equator. The combination of near-Sun, quasi-heliosynchronous and high-latitude observations by remote-sensing and in-situ instruments makes Solar Orbiter a unique platform for the study of the links between the Sun and the inner heliosphere. Title: Disentangling The Magnetic Field Structure Of Sunspots - Stereoscopic Polarimetry With Solar Orbiter Authors: Müller, D. A. N.,; Schlichenmaier, R.; Fleck, B.; Fritz, G. Bibcode: 2007ESASP.641E..32M Altcode: Sunspots exhibit complex, highly structured magnetic fields and flows. Disentangling the atmospheric structure of sunspots is a great challenge, and can only be achieved by the combination of spectropolarimetry at high spatial resoultion and detailed modeling efforts. We use a generalized 3D the embeds magnetic flux tuber in a stratified atmosphere and calculates the emerging polarization of spectrail lines for arbitrary viewing angles. The resulting polarization maps are a very efficient tool to distinguish between different atmospheric scenarios and determine the 3D structure of the magnetic field and the flow field. In this contribution, we present synthetic maps of the net circular polarication (NCP) as a function of the heliocentric angle for different spectral lines of interest. Among these are the Fe I 617.3 nm line which would be observed by the VIM instrument abard Solar Orbiter and the Fe I 630.2 nm line which will be observed by Hinode (formerly known as Solar-B). Title: Future solar space missions Authors: Fleck, B. Bibcode: 2007msfa.conf...17F Altcode: The coming years promise to be the golden era of solar and heliospheric physics, with STEREO, Hinode (Solar-B) and SDO enhancing the current fleet of solar space missions and affording new opportunities for improved understanding of the Sun-heliosphere system. Looking beyond that, however, there is a significant gap until Solar Orbiter will be launched in 2015 (nearly 20 years after the launch of SOHO). This paper provides an overview of the next generation of solar space missions. Title: Low-frequency magneto-acoustic waves in the solar chromosphere Authors: Jefferies, S. M.; McIntosh, S. W.; Armstrong, J. D.; Bogdan, T. J.; Cacciani, A.; Fleck, B. Bibcode: 2006ESASP.624E..16J Altcode: 2006soho...18E..16J No abstract at ADS Title: Magnetoacoustic Portals and the Basal Heating of the Solar Chromosphere Authors: Jefferies, Stuart M.; McIntosh, Scott W.; Armstrong, James D.; Bogdan, Thomas J.; Cacciani, Alessandro; Fleck, Bernhard Bibcode: 2006ApJ...648L.151J Altcode: We show that inclined magnetic field lines at the boundaries of large-scale convective cells (supergranules) provide ``portals'' through which low-frequency (<5 mHz) magnetoacoustic waves can propagate into the solar chromosphere. The energy flux carried by these waves at a height of 400 km above the solar surface is found to be a factor of 4 greater than that carried by the high-frequency (>5 mHz) acoustic waves, which are believed to provide the dominant source of wave heating of the chromosphere. This result opens up the possibility that low-frequency magnetoacoustic waves provide a significant source of energy for balancing the radiative losses of the ambient solar chromosphere. Title: Low-frequency magneto-acoustic waves in the solar chromosphere Authors: Jefferies, S. M.; McIntosh, S. W.; Armstrong, J. D.; Cacciani, A.; Bogdan, T. J.; Fleck, B. Bibcode: 2006IAUJD...3E..62J Altcode: We demonstrate that low-frequency (< 5 mHz) propagating magneto-acoustic waves provide a larger source of energy for balancing the radiative losses of the solar chromosphere than their high-frequency (> 5 mHz) counterparts. The low-frequency waves, which are normally evanescent in the solar atmosphere, are able to propagate through "acoustic portals" that exist in areas of strong, significantly inclined (> 30° with respect to the vertical), magnetic field. Such conditions are found both in active regions and at the boundaries of supergranules. The latter implies that acoustic portals are omnipresent over the solar surface and throughout the magnetic activity cycle, an essential prerequisite for any baseline heating mechanism. Title: 10 years of SOHO Authors: Fleck, Bernhard; Müller, Daniel; Haugan, Stein; Sánchez Duarte, Luis; Siili, Tero; Gurman, Joseph B. Bibcode: 2006ESABu.126...24F Altcode: Since its launch on 2 December 1995, SOHO has revolutionised our understanding of the Sun. It has provided the first images of structures and flows below the Sun's surface and of activity on the far side. SOHO has revealed the Sun's extremely dynamic atmosphere, provided evidence for the transfer of magnetic energy from the surface the outer solar atmosphere, the corona, through a "magnetic carpet", and identified the source regions of the fast solar wind. It has revolutionised our understanding of solar-terrestrial relations and dramatically improved our space weather-forecasting by its continuous stream of images covering the atmosphere, extended corona and far side. The findings are documented in an impressive number of scientific publications: over 2500 papers in refereed journals since launch, representing the work of over 2300 individual scientists. At the same time, SOHO's easily accessible, spectacular data and fundamental scientific results have captured the imagination of the space science community and the general public alike. As a byproduct of the efforts to provide real-time data to the public, amateurs now dominate SOHO's discovery of over 1100 Sungrazing comets. Title: 10 Years of SOHO: Some lessons and where to go next Authors: Fleck, B. Bibcode: 2006cosp...36.3397F Altcode: 2006cosp.meet.3397F SOHO has brought us a wealth of new information about the Sun the heliosphere and space weather and has provided an exemplary model for international cooperation The scientific achievements of the SOHO mission are the results of a concerted multi-disciplinary effort by a large international community of solar scientists involving sound investment in space hardware coupled with a vigorous and well-coordinated scientific operation and interpretation effort From the beginning SOHO was conceived as an integrated package of complementary instruments and great emphasis has been placed on coordinated observations both internally among different SOHO instruments as well as externally with other spacecraft and ground-based observatories The next five years promise to be the golden era of solar and heliospheric physics with STEREO Solar-B and SDO SOHO s lineal descendant enhancing the current fleet of solar space missions and affording new opportunities for improved understanding of the Sun-heliosphere system Looking beyond that however there is a significant gap until Solar Orbiter will be launched in 2015 nearly 20 years after the launch of SOHO I will review some of the key findings from SOHO discuss how future missions will achieve new understanding built on the foundation laid by SOHO and what in my view are the key challenges for future missions Title: Evolution of the Magnetic Energy Budget in AR 10486 from Potential and Nonlinear Force-Free Models Authors: Régnier, S.; Fleck, B.; Abramenko, V.; Zhang, H. -Q. Bibcode: 2005ESASP.596E..61R Altcode: 2005ccmf.confE..61R No abstract at ADS Title: Connecting Sun and Heliosphere (Solar Wind 11 / SOHO 16) Authors: Fleck, B.; Zurbuchen, T. H.; Lacoste, H. Bibcode: 2005ESASP.592.....F Altcode: 2005soho...16E....F No abstract at ADS Title: Foreword Authors: Zurbuchen, T. H.; Fleck, B. Bibcode: 2005ESASP.592....3Z Altcode: No abstract at ADS Title: The TRACE Inter-Network Oscillations (INO) Program II: Observations of Limb and Coronal Hole Regions Authors: McIntosh, S. W.; Crotser, D.; Leamon, R. J.; Fleck, B.; Tarbell, T. D. Bibcode: 2005AGUSMSH13C..06M Altcode: We will present results of the TRACE Inter-Network Oscillations (INO) observing program from 2003 to the present. The INO program uses near-simultaneous observations in the 1600Å and 1700Å UV continuum pass bands as an acoustic probe of chromospheric structure. In this poster we will discuss the INO observations of limb, polar and coronal hole regions and show the key results found, thus far. These observations offer us a remote means to study the structure and behavior of the chromopsheric plasma topography at a potential driving base for the heliospheric plasma system. Title: Travel Time and Phase Analysis of Waves in the Lower Solar Chromosphere Authors: Fleck, B.; Armstrong, J.; Cacciani, A.; de Pontieu, B.; Finsterle, W.; Jefferies, S. M.; McIntosh, S. W.; Tarbell, T. D. Bibcode: 2005AGUSMSH13C..04F Altcode: In an effort to better understand how the chromospheric plasma and magnetic fields are guiding, converting and dissipating acoustic waves, we analyze high-cadence time series taken in Na I D2 589.0 nm and K I 769.9 nm that were obtained with the Magneto Optical Filters at Two Heights (MOTH) experiment at the South Pole in January 2003. These data are complemented by a very high spatial resolution time series taken in Na D with the Swedish Vacuum Solar Telescope in June 1992. The travel time maps, power maps, and phase diagrams show some unexpected behaviour, in particular in and around active regions. Title: Energetics of AR 0486 from line-of-sight and vector magnetograms Authors: Regnier, S.; Fleck, B. Bibcode: 2005AGUSMSH51C..09R Altcode: Over two weeks in October/November 2003, the Sun featured unusually strong activity, with three large sunspot groups (including the largest one of this solar cycle), twelve X-class flares (including the strongest ever recorded), numerous halo coronal mass ejections (two with near-recorded speeds) and two significant proton storms. Eight of the twelve X-class flares originated from active region AR 10486. To understand the reasons of this peculiar activity, we investigate the evolution of the coronal magnetic field configuration as well as the energetics of AR 10486 before and after the X17.2 flare on October 28. To determine the coronal magnetic fields, we use potential and nonlinear force-free reconstruction techniques using line-of-sight (SOHO/MDI) and vector (MSO/IVM, Huairou, BBSO) magnetograms on the photosphere as boundary conditions. We identify the source region of the flare as related to the existence of null point or separator field line evidenced in a reversed-Y magnetic configuration. From the 3D configurations we derive the magnetic energy budget which can be released during the impulsive phase of the flare. The estimated free magnetic energy is enough to trigger an X-class flare. The continuous evolution of the magnetic energy derived from the potential field extrapolations indicates that the flare does not modify the distribution of magnetic field on the photosphere. We also study the distribution of energy before and after the flare using different vector magnetic field measurements. Title: Space Weather Effects on SOHO and its Leading Role as a Space Weather Wãtchdog Authors: Brekke, P.; Fleck, B.; Haugan, S. V.; van Overbeek, T.; Schweitzer, H.; Simonin, B. Bibcode: 2005mcsp.conf...83B Altcode: No abstract at ADS Title: Eight years of SOHO: some highlights Authors: Fleck, B. Bibcode: 2005ASSL..320..139F Altcode: 2005smp..conf..139F No abstract at ADS Title: Solar Orbiter—mission profile, main goals and present status Authors: Marsch, Eckart; Marsden, Richard; Harrison, Richard; Wimmer-Schweingruber, Robert; Fleck, Bernhard Bibcode: 2005AdSpR..36.1360M Altcode: The main goals and present status of the Solar Orbiter mission are briefly described. solar orbiter will determine in situ the properties of fields and particles in the unexplored near-Sun heliosphere in three dimensions, investigate remotely the fine-scale structures and events in the magnetically coupled layers of the Sun’s atmosphere, identify through near corotation the links between activity on the solar surface and the resulting evolution of the inner heliosphere, and observe from relatively high latitudes the polar regions and equatorial corona. Some results from recent activities, such as industrial studies, payload working group meetings, science definition team meetings and ESA internal studies are briefly reviewed. Solar Orbiter is currently planned for launch in October 2013. Title: SOHO 15 Workshop - Coronal Heating Authors: Walsh, R. W.; Ireland, J.; Danesy, D.; Fleck, B. Bibcode: 2004ESASP.575.....W Altcode: 2004soho...15.....W No abstract at ADS Title: Magnetic Field Evolution of AR 0486 Before and after the X17 Flare on October 28, 2003 Authors: Régnier, S.; Fleck, B. Bibcode: 2004ESASP.575..519R Altcode: 2004soho...15..519R No abstract at ADS Title: Chromospheric Oscillations in an Equatorial Coronal Hole Authors: McIntosh, Scott W.; Fleck, Bernhard; Tarbell, Theodore D. Bibcode: 2004ApJ...609L..95M Altcode: We report phase-difference and travel-time analyses of propagating chromospheric oscillations in and around an equatorial coronal hole as observed by TRACE. Our results suggest a significant change in atmospheric conditions at the base of the chromosphere inside the coronal hole relative to its boundary and quiet-Sun regions. Title: Probing Chromospheric Structure with the TRACE Inter-Network Oscillation Program Authors: Fleck, B.; McIntosh, S. W. Bibcode: 2004AAS...204.3717F Altcode: 2004BAAS...36..711F We discuss the structure and dynamics of the solar chromosphere through the application of several diagnostics to the Transition Region and Coronal Explorer (TRACE) Inter-Network Oscillation (INO) ''synoptic'' observing sequence. Using several newly developed diagnostics we investigate the generation and interplay of the observed chromospheric oscillations and the ubiquitous magnetic field that permeates the TRACE field of view. Title: The Magnetic Field Evolution of AR 10486 and AR 10488 Before and After the X17 Flare on Oct. 28, 2003 Authors: Regnier, S.; Fleck, B. Bibcode: 2004AAS...204.0205R Altcode: 2004BAAS...36..668R We investigate the causes and the consequences of the X17 flare which occured in active region (AR) 10486 on Oct. 28, 2003. Using MDI high-cadence longitudinal magnetograms, we first follow the evolution of the photospheric magnetic field of both AR 10486 (site of the flare) and AR 10488 (new emerged active region). We then identify the main photospheric motions in AR 10486 which are precursors of the eruptive phenomena (e.g., emergence of flux, cancellation of flux). We also focus our study on the fast emergence of AR 10488 and the change of connectivity between the two active regions after the flare.

We also study the evolution of the coronal magnetic fields assuming a potential field equilibrium state. This is a case study to know if we can forecast a solar eruption using a time series of potential field extrapolations.

For both active regions, an IVM vector magnetogram is available almost 16 hours before the flare and is used as a snapshot. Those two magnetograms allow us to determine the nonlinear force-free magnetic configurations as well as the free energy budgets. These computations allow us to estimate how far those active regions are from the potential field configurations.

S. Regnier's research is funded by the European Community's Human Potential Programme through the European Solar Magnetism Network (contract HPRN-CT-2002-00313). Title: Summary of the Solar Orbiter payload working group activities Authors: Fleck, Bernhard; Harrison, Richard A.; Marsden, Richard G.; Wimmer-Schweingruber, Robert Bibcode: 2004SPIE.5171..123F Altcode: Approved in October 2000 by ESA's Science Programme Committee as a flexi-mission, the Solar Orbiter will study the Sun and unexplored regions of the inner heliosphere from a unique orbit that brings the probe to within 45 solar radii (0.21 AU) of our star, and to solar latitudes as high as 38°. The scientific payload to be carried by the Orbiter will include a sophisticated remote-sensing package, as well as state-of-the-art in-situ instruments. Given the technical and financial constraints associated with this mission, it is essential that key technologies requiring significant development be identified as early as possible. ESA has therefore set up a Payload Working Group (PWG), made up of members of the scientific community with expertise in instrumentation of the kind envisaged for the Solar Orbiter. The tasks of the PWGs included: 1) a realistic assessment of the strawman payload, including definition of mass, size, power requirements; 2) identification of key problem areas arising as a result of the extreme thermal and radiation environments; 3) identification of necessary technological developments; and 4) provision of detailed input to a Solar Orbiter Payload Definition Document (PDD). This contribution summarizes the activities and findings by the Solar Orbiter Payload Working Group. Title: Development of imaging arrays for solar UV observations based on wide band gap materials Authors: Schuehle, Udo H.; Hochedez, Jean-Francois E.; Pau, Jose Luis; Rivera, Carlos; Munoz, Elias; Alvarez, Jose; Kleider, Jean-Paul; Lemaire, Philippe; Appourchaux, Thierry; Fleck, Bernhard; Peacock, Anthony; Richter, Mathias; Kroth, Udo; Gottwald, Alexander; Castex, Marie-Claude; Deneuville, Alain; Muret, Pierre; Nesladek, Milos; Omnes, Franck; John, Joachim; Van Hoof, Chris Bibcode: 2004SPIE.5171..231S Altcode: Solar ultraviolet imaging instruments in space pose most demanding requirements on their detectors in terms of dynamic range, low noise, high speed, and high resolution. Yet UV detectors used on missions presently in space have major drawbacks limiting their performance and stability. In view of future solar space missions we have started the development of new imaging array devices based on wide band gap materials (WBGM), for which the expected benefits of the new sensors - primarily visible blindness and radiation hardness - will be highly valuable. Within this initiative, called "Blind to Optical Light Detectors (BOLD)", we have investigated devices made of AlGa-nitrides and diamond. We present results of the responsivity measurements extending from the visible down to extreme UV wavelengths. We discuss the possible benefits of these new devices and point out ways to build new imaging arrays for future space missions. Title: Mapping the Chromospheric Plasma Topography Through Chromospheric Oscillations Authors: McIntosh, S. W.; Fleck, B. Bibcode: 2004ESASP.547..149M Altcode: 2004soho...13..149M Recent research has shown that understanding the physical nature of chromospheric oscillations hinges critically upon the understanding of the plasma structure in which they are formed and observed. To this end we discuss the mapping of the chromospheric plasma topography through the analysis of simultaneous SOHO/MDI and TRACE time-series observations through a combination of Fourier and Wavelet based analysis techniques. We are able to construct a picture of the chromospheric plasma and its interaction with the wave modes present. Such a picture will focus studies on topographic regions that will form a simulation test-bed for theories of modeconversion, dissipation and wave heating in the solar chromosphere. Title: Eight Years of SOHO Authors: Fleck, Bernhard Bibcode: 2004IAUS..223..589F Altcode: 2005IAUS..223..589F Since its launch on 2 December 1995, the joint ESA/NASA SOHO mission has provided a wealth of information about the Sun, from its interior, through the hot and dynamic atmosphere, to the solar wind and its interaction with the interstellar medium. At the same time, SOHO's easily accessible images and movies have captured the imagination of the science community and the general public alike. This article summarizes some of the key findings from 8 years of SOHO. Title: Spatial Correlations of Phase Relationships in TRACE Ultraviolet Bandpasses Authors: McIntosh, S. W.; Fleck, B. Bibcode: 2004IAUS..219..696M Altcode: No abstract at ADS Title: Saving SOHO Authors: Fleck, B. Bibcode: 2004ESASP.547..543F Altcode: 2004soho...13..543F No abstract at ADS Title: Sunspot Umbral Oscillations: Results from SOHO JOP097 Authors: O'Shea, E.; Muglach, K.; Fleck, B. Bibcode: 2003csss...12..601O Altcode: We present results of an ongoing analysis of time series data, which were obtained in the context of the Joint Observing Program (JOP) 97 of the year 2000. This JOP included the Coronal Diagnostic Spectrometer (CDS) and the Michelson Doppler Imager (MDI) instrument, both part of SOHO, the TRACE satellite and various ground based observatories. We show evidence for apparently upwardly propagating in a sunspot umbra which we suggest are due to magnetoacoustic waves. These waves manifest themselves as oscillations in lines ranging in temperature from the upper photosphere/chromosphere to the corona. To our knowledge this is the first time umbral oscillations have been conclusively seen in coronal lines. This research is part of the European Solar Magnetometry Network (ESMN) supported by the EU through the TMR programme. Title: Investigating the role of plasma topography on chromospheric oscillations observed by TRACE Authors: McIntosh, S. W.; Fleck, B.; Judge, P. G. Bibcode: 2003A&A...405..769M Altcode: We present the results of an investigation into the interaction of the topographic structure of the solar chromospheric plasma with the wave modes manifesting themselves in the UV continua formed there. We show that there is a distinct correlation between the inferred plasma topography, the phase-differences between and suppression of oscillations in different levels of the solar atmosphere. We interpret these factors as evidence of interaction between the oscillations and the extended magnetic ``canopy''. This work is based on the analysis of joint observations made by the Solar and Heliospheric Observatory (SOHO) spacecraft and the Transition Region and Coronal Explorer (TRACE). Title: Chromospheric Oscillations observed by SUMER and TRACE: Their Interplay with the Solar Plasma Topography Authors: McIntosh, S. W.; Fleck, B. Bibcode: 2003SPD....34.0701M Altcode: 2003BAAS...35R.819M We present the results of an investigation into the interaction of wave modes with the solar chromospheric plasma's topography through the analysis of joint SOHO/SUMER and TRACE observations. We show that there is a distinct correlation between the inferred solar plasma topography (specifically the height of the transition from a high to low plasma-beta regime) and the phase differences between, and suppression of, atmospheric/chromospheric oscillations in different levels of the solar atmosphere. Indeed, we demonstrate that the spectroscopic signal observed changes dramatically in the passage from the high to low beta regimes. We propose that the dependences presented can be used as an interpretative tool for simulations seeking to model chromospheric oscillations and as a diagnostics of the plasma conditions in the important region in the mid-chromosphere where the plasma-beta is of order unity, through the signatures of the wave-modes present. Title: Solar Orbiter: a mission overview and status update Authors: Fleck, Bernhard; Marsden, Richard G. Bibcode: 2003SPIE.4853..150F Altcode: Approved in October 2000 by ESA's Science Programme Committee as a flexi-mission and re-confirmed in May 2002 as an element in the new ESA science programme "Cosmic Vision", the Solar Orbiter will study the Sun and unexplored regions of the inner heliosphere from a unique orbit that brings the probe to within 45 solar radii of our star, and to solar latitudes as high as 38 degrees. The scientific payload to be carried by the Solar Orbiter will include both remote-sensing instruments and an in situ package. Launch is currently scheduled for 2012. Given the technical challenges associated with this mission, it is essential that key technologies requiring significant development be identified as early as possible. ESA has therefore set up Payload Working Groups whose task it is to address potential problem areas arising as a result of the extreme thermal and radiation environment and to identify necessary technological developments. Title: New UV detectors for solar observations Authors: Hochedez, Jean-Francois E.; Schuehle, Udo H.; Pau, Jose L.; Alvarez, Jose; Hainaut, Olivier; Appourchaux, Thierry P.; Auret, F. D.; Belsky, Andrei; Bergonzo, Philippe; Castex, M. C.; Deneuville, A.; Dhez, Pierre; Fleck, Bernhard; Haenen, Ken; Idir, Mourad; Kleider, Jean Paul; Lefeuvre, Elie; Lemaire, Philippe; Monroy, E.; Muret, P.; Munoz, Elias; Nesladek, Milos; Omnes, Franck; Pace, Emanuele; Peacock, Anthony J.; Van Hoof, Chris A. Bibcode: 2003SPIE.4853..419H Altcode: BOLD (Blind to the Optical Light Detectors) is an international initiative dedicated to the development of novel imaging detectors for UV solar observations. It relies on the properties of wide bandgap materials (in particular diamond and Al-Ga-nitrides). The investigation is proposed in view of the Solar Orbiter (S.O.) UV instruments, for which the expected benefits of the new sensors -primarily visible blindness and radiation hardness- will be highly valuable. Despite various advances in the technology of imaging detectors over the last decades, the present UV imagers based on silicon CCDs or microchannel plates exhibit limitations inherent to their actual material and technology. Yet, the utmost spatial resolution, fast temporal cadence, sensitivity, and photometric accuracy will be decisive for the forthcoming solar space missions. The advent of imagers based on wide-bandgap materials will permit new observations and, by simplifying their design, cheaper instruments. As for the Solar Orbiter, the aspiration for wide-bandgap material (WBGM) based UV detectors is still more sensible because the spacecraft will approach the Sun where the heat and the radiation fluxes are high. We describe the motivations, and present the program to achieve revolutionary flight cameras within the Solar Orbiter schedule as well as relevant UV measurements. Title: Towards an explanation of features in the diagnostic diagram of a model atmosphere. I. Linear wave equations with convenient invariants Authors: Schmitz, F.; Fleck, B. Bibcode: 2003A&A...399..723S Altcode: New standard forms of the time-independent linear adiabatic wave equation of plane atmospheres are presented. The main objective is to obtain equations with invariants as simple as possible so that oscillation theorems can be applied effectively. By transformations of both the independent and the dependent variables, equations with simple invariants are formulated. We present a standard form of the wave equation the invariant of which depends only on the first derivative of the equilibrium density, as opposed to the common standard form the invariant of which depends also on second derivatives. Further, we discuss a procedure which replaces the wave equation by a system of two simple second order differential equations. In this case we try to draw conclusions on the general behavior of solutions by use of oscillation theorems. In addition, a re-formulation of the wave equation is presented, which eliminates terms with first derivatives of atmospheric quantities. The independent variable of the resulting equation depends not only on the geometrical height but also on the ratio omega /k. In this case, it is necessary to use a diagnostic diagram the axes of which are given by omega /k and omega instead of the common k-omega diagram. Therefore we discuss the meaning of the parameter omega /k for the representation of dispersion curves. Finally, for the VAL-atmosphere (Vernazza et al. \cite{vernazza}), regions of certainly nonoscillatory waves are considered. Title: Solar observing facilities Authors: Fleck, B.; Keller, C. U. Bibcode: 2003dysu.book..403F Altcode: An overview is given of current and planned ground-based solar telescopes and instruments, balloon-borne and suborbital solar telescopes, and solar and heliospheric space missions. These observing facilities operate in all areas of solar physics, from the solar interior to interplanetary space and from regimes of high energy to observations requiring high resolution. The next generation of solar telescopes and instruments promise us the ability to investigate solar processes on their fundamental scales, whether sub-arc second or global in nature. Title: The Solar Orbiter mission Authors: Marsden, R. G.; Fleck, B. Bibcode: 2003AdSpR..32.2699M Altcode: Approved in October 2000 by ESA's Science Programme Committee as a flexi-mission, the Solar Orbiter will studythe Sun and unexplored regions of the inner heliosphere from a unique orbit that brings the probe to within 45 solar radii (0.21 AU) of our star, and to solar latitudes as high as 38°. This orbit will allow the Solar Orbiter to make fundamental contributions to our understanding of the acceleration and propagation of energetic particles in the extended solar atmosphere. During quasi-heliosynchronous phases of the orbit, Solar Orbiter will track a given region of the solar surface for several days, making possible unprecedented studies of the sources of impulsive and CME-related particle events. The scientific payload to be carried by the probe will include a sophisticated remote-sensing package, as well as state-of-the-art in-situ instruments. The multi-wavelength, multi-disciplinary approach of Solar Orbiter, combined with its novel location, represents a powerful tool for studies of energetic particle phenomena. Title: Prospects in ESA for young researchers in solar physics Authors: Wenzel, K. -P.; Fleck, B. Bibcode: 2002ESASP.506.1001W Altcode: 2002svco.conf.1001W; 2002ESPM...10.1001W SOHO, the solar physics flagship mission, being operational over a solar cycle, and the upcoming Solar Orbiter form strong elements in the ESA space science programme. The paper gives a brief overview of ESA and its space science programme, summarises the scope and staffing of ESA's Research and Scientific Support Department (RSSD), and describes career and training opportunities for young researchers within ESA. Title: Solar Orbiter: a mission overview and status update Authors: Fleck, B.; Marsden, R. Bibcode: 2002ESASP.506..919F Altcode: 2002ESPM...10..919F; 2002svco.conf..919F Approved in October 2000 by ESA's Science Programme Committee as a flexi-mission and re-confirmed in May 2002 as an element in the new ESA science programme "Cosmic Vision", the Solar Orbiter will study the Sun and unexplored regions of the inner heliosphere from a unique orbit that brings the probe to within 45 solar radii of our star, and to solar latitudes as high as 38 degrees. The scientific payload to be carried by the Solar Orbiter will include both remote-sensing instruments and an in situ package. Launch is currently scheduled for 2012. Given the technical challenges associated with this mission, it is essential that key technologies requiring significant developement be identified as early as possible. ESA has therefore set up Payload Working Groups whose task it is to address potential problem areas arising as a result of the extreme thermal and radiation environment and to identify necessary technological developments. Title: Prospects of future solar space missions Authors: Fleck, B. Bibcode: 2002ESASP.505..311F Altcode: 2002IAUCo.188..311F; 2002solm.conf..311F Recent results from solar space missions like Yohkoh, SOHO, TRACE, ACE, and Ulysses have produced stunning results that are invigorating solar research and challenging existing models of the Sun. Future space missions and new ground-based instruments promise to continue this "solar renaissance" in all areas of solar physics. This paper provides an overview of the next generation of solar space missions. The scientific objectives, mission profiles and payload capabilities of Solar-B, STEREO, Picard, SST, SDO, ASCE, Solar Probe, Solar Orbiter, Sentinels, and RAM are summarized. Title: Automated detection of CMEs in LASCO data Authors: Berghmans, D.; Foing, B. H.; Fleck, B. Bibcode: 2002ESASP.508..437B Altcode: 2002soho...11..437B We have developed software that autonomously detects CMEs in image sequences from LASCO. the crux of the software is the detection of CMEs as bright ridges in (height, time) maps using the Hough transform. The output is a list of events, similar to the classic catalogs, with principle angle, angular width and velocity estimation for each CME. In contrast to catalogs assembled by human operators, these CME detections by software can be faster, which is especially important in the context of space weather, and possibly also more objective, as the detection criterion is written explicitly in a program. In this paper we describe the software and validate its performance by comparing its output with the visually assembled CME catalogs. We discuss its present success rate (about 75%) and prospects for improvement. Finally, we show that the software can also reveal CMEs that have not been listed in the catalogs. Such unreported cases might be of influence on CME statistics and prove that also the present catalogs do not have a 100% success rate. Title: Trawling around in the Noise Authors: Fleck, B.; McIntosh, S. W. Bibcode: 2002AAS...200.3905F Altcode: 2002BAAS...34..701F We investigate the possible presence of low amplitude, high-frequency oscillations in short time exposure SUMER timeseries. Using a variety of profile fitting methods and a combination of real and synthetic data we examine the detection thresholds and limits. As a result we can assess the likelyhood that certain long-duration, high cadence, SUMER datasets contain meaningful information about the propagation of high frequency waves in the Solar Chromosphere and Transition Region. Title: Oscillations above sunspots: Evidence for propagating waves? Authors: O'Shea, E.; Muglach, K.; Fleck, B. Bibcode: 2002A&A...387..642O Altcode: We present results of an analysis of time series data observed in sunspot umbral regions. The data were obtained in the context of the SOHO Joint Observing Program (JOP) 97 in September 2000. This JOP included the Coronal Diagnostic Spectrometer (CDS) and the Michelson Doppler Imaging (MDI) instrument, both part of SOHO, the TRACE satellite and various ground based observatories. The data was analysed by using both Fourier and wavelet time series analysis techniques. We find that oscillations are present in the umbra at all temperatures investigated, from the temperature minimum as measured by TRACE 1700 Å up to the upper corona as measured by CDS Fe Xvi 335 Å (log T=6.4 K). Oscillations are found to be present with frequencies in the range of 5.4 mHz (185 s) to 8.9 mHz (112 s). Using the techniques of cross-spectral analysis time delays were found between low and high temperature emission suggesting the possibility of both upward and downward wave propagation. It is found that there is typically a good correlation between the oscillations measured at the different emission temperatures, once the time delays are taken into account. We find umbral oscillations both inside and outside of sunspot plume locations which indicates that umbral oscillations can be present irrespective of the presence of these sunspot plumes. We find that a number of oscillation frequencies can exist co-spatially and simultaneously i.e. for one pixel location three different frequencies at 5.40, 7.65 and 8.85 mHz were measured. We investigate the variation of the relative amplitudes of oscillation with temperature and find that there is a tendency for the amplitudes to reach a maximum at the temperature of O Iii (and less typically O V and Mg Ix) and then to decrease to reach a minimum at the temperature of Mg X (log T=6.0 K), before increasing again at the temperature of Fe Xvi. We discuss a number of possible theoretical scenarios that might explain these results. From a measurement of propagation speeds we suggest that the oscillations we observe are due to slow magnetoacoustic waves propagating up along the magnetic field lines. Title: Space weather aspects of the ESA Solar Orbiter mission Authors: Marsden, R.; Fleck, B. Bibcode: 2002ESASP.477..359M Altcode: 2002scsw.conf..359M No abstract at ADS Title: Space Weather Aspects of the ESA Solar Orbiter Mission Authors: Marsden, R. G.; Fleck, B. Bibcode: 2002stma.conf..443M Altcode: No abstract at ADS Title: The Sun During The Ulysses Fast Latitude Scan and Northern Polar Pass As Seen By Soho Authors: Fleck, B.; Brekke, P.; Haugan, S. V. H. Bibcode: 2002EGSGA..27.3839F Altcode: In 2001, during the Ulysses fast latitude scan (January - September) and second north- ern polar pass (September - December), the Sun showed a remarkable resurgence of solar activity after its rapid drop-off following the activity maximum in the summer of 2000. In early April active region 9393, the largest active region of the current cycle, produced a series of events, among them the biggest X-ray flare on record. In the fall there were three severe proton storms, one of them the third largest on record since measurements began in 1976. It is interesting to note that five out of the eight proton storms with flux densities greater than 10,000 cm-2 s-1 sr-1 (>10 MeV) since 1976 occurred in cycle 23, and three of these five in 2001. The overall change in solar ac- tivity in 2001 will be reviewed and some of the most dramatic events from that year discussed. Title: Long-term solar irradiance variations: results and perspectives Authors: Pap, J.; Fleck, B.; Frohlich, C.; Jones, H.; Kuhn, J.; Schmutz, W. Bibcode: 2002cosp...34E.553P Altcode: 2002cosp.meetE.553P In this paper we show the recent result on irradiance variations and their relation to solar magnetic activity over solar cycles 21 to 23. Comparison of the multi-decade long irradiance and magnetic field measurements indicates that the shape and magnitude of irradiance variations are different from that of magnetic indices. Specifically, while magnetic indices show that solar cycle 23 is weaker than the two previous cycles, the long-term variation of total solar irradiance over solar cycles 21 to 23 is rather symmetrical, showing that its maximum and minimum levels were about the same within their measuring uncertainties. These results raise questions like: (1) is there a strict linear relationship between solar variability and irradiance variations as the current irradiance models used in climate studies assume?; (2) what is the role of polar magnetic fields in irradiance changes?; (3) is there a significant non-magnetic component in the observed irradiance variations? The results presented in this paper underscore the need to further develop new measurement and analysis techniques to study and predict the climate impact of solar variability. Title: JOSO report 200-2001 - The Netherlands. Solar Physics in The Netherlands Authors: Rutten, R.; Keppens, R.; Fleck, B. Bibcode: 2002joso.book...81R Altcode: Solar physics research in the Netherlands is carried out at Nijmegen, Utrecht, Nieuwegein, and Noordwijk. Title: Space Weather Effects on SOHO Authors: Brekke, P.; Fleck, B.; Haugan, S.; Schweitzer, H.; Chaloupy, M. Bibcode: 2002cosp...34E2156B Altcode: 2002cosp.meetE2156B Since its launch on 2 December 1995, the Solar and Heliospheric Observatory (SOHO) has provided an unparalleled breadth and depth of information about the Sun, from its interior, through the hot and dynamic atmosphere, and out to the solar wind. SOHO is in a halo orbit around L1 Lagrangian point where it views the Sun 24 hours a day. Thus, it is situated outside the Earth's protective magnetosphere which shields other satellites from high energy particles from the Sun. We present a summary of the observed effects on the instruments and electronics on SOHO throughout the mission. In particular we will focus on a number of large particle events during the recent years while the Sun was approaching maximum activity, and how they affected both the scientific data as well as hardware components. Title: The Solar Orbiter mission Authors: Marsden, R.; Fleck, B. Bibcode: 2002cosp...34E.222M Altcode: 2002cosp.meetE.222M Approved in October 2000 by ESA's Science Programme Committee as a flexi mission, the Solar Orbiter will study the Sun and unexplored regions of the inner heliosphere from a unique orbit that brings the probe to within 45 solar radii (0.21 AU) of our star, and to solar latitudes as high as 38° This orbit will allow the Solar Orbiter to make fundamental contributions to our understanding of the acceleration and propagation of energetic particles in the extended solar atmosphere. During the quasi-heliosynchronous phases of the orbit, Solar Orbiter will track a given region of the solar surface for several days, making possible unprecedented studies of the sources of impulsive and CME-related particle events. The scientific payload to be carried by the probe will include a sophisticated remote-sensing package, as well as state-of-the-art in-situ instruments. The multi-wavelength, multi-disciplinary approach of Solar Orbiter, combined with its novel location, represents a powerful tool for studies of energetic particle phenomena. Title: Solar orbiter, a high-resolution mission to the sun and inner heliosphere Authors: Marsch, E.; Antonucci, E.; Bochsler, P.; Bougeret, J. -L.; Fleck, B.; Harrison, R.; Langevin, Y.; Marsden, R.; Pace, O.; Schwenn, R.; Vial, J. -C. Bibcode: 2002AdSpR..29.2027M Altcode: The scientific rationale of the Solar Orbiter is to provide, at high spatial (35 km pixel size) and temporal resolution, observations of the solar atmosphere and unexplored inner heliosphere. Novel observations will be made in the almost heliosynchronous segments of the orbits at heliocentric distances near 45 R⊙ and out of the ecliptic plane at the highest heliographic latitudes of 30° - 38°. The Solar Orbiter will achieve its wide-ranging aims with a suite of sophisticated instruments through an innovative design of the orbit. The first near-Sun interplanetary measurements together with concurrent remote observations of the Sun will permit us to determine and understand, through correlative studies, the characteristics of the solar wind and energetic particles in close linkage with the plasma and radiation conditions in their source regions on the Sun. Over extended periods the Solar Orbiter will deliver the first images of the polar regions and the side of the Sun invisible from the Earth. Title: Solar Orbiter: a high-resolution mission to the sun and inner heliosphere Authors: Fleck, Bernhard; Marsch, E.; Antonucci, Ester; Bochsler, Peter A.; Bougeret, J. L.; Harrison, R.; Marsden, R. P.; Coradini, M.; Pace, Oscar; Schwenn, Rainer; Vial, Jean-Claude Bibcode: 2001SPIE.4498....1F Altcode: The key mission objective of the Solar Orbiter is to study the Sun from close-up (45 solar radii, or 0.21 AU) in an orbit tuned to solar rotation in order to examine the solar surface and the space above from a co-rotating vantage point at high spatial resolution. Solar Orbiter will also provide images of the Sun's polar regions from heliographic latitudes as high as 38 degrees. The strawman payload encompasses two instrument packages: Solar remote-sensing instruments: EUV full-sun and high resolution imager, high-resolution EUV spectrometer, high-resolution and full-sun visible light telescope and magnetograph, EUV and visible-light coronagraphs, radiometers. Heliospheric instruments: solar wind analyzer, radio and plasma wave analyzer, magnetometer, energetic particle detectors, interplanetary dust detector, neutral particle detector, solar neutron detector. To reach its novel orbit, Solar Orbiter will make use of low-thrust solar electric propulsion (SEP) interleaved by Earth and Venus gravity assists. Solar Orbiter was selected by ESA's Science Programme Committee (SPC) in October 2000 as a Flexi-mission, to be implemented after the BepiColombo cornerstone mission to Mercury before 2013. This paper summarizes the science to be addressed with the Solar Orbiter, followed by brief descriptions of the strawman payload, the mission profile, and the spacecraft and ground segment designs. Title: Measuring Solar Abundances Authors: von Steiger, R.; Vial, J. -C.; Bochsler, P.; Chaussidon, M.; Cohen, C. M. S.; Fleck, B.; Heber, V. S.; Holweger, H.; Issautier, K.; Lazarus, A. J.; Ogilvie, K. W.; Paquette, J. A.; Reisenfeld, D. B.; Teriaca, L.; Wilhelm, K.; Yusainee, S.; Laming, J. M.; Wiens, R. C. Bibcode: 2001AIPC..598...13V Altcode: 2001sgc..conf...13V This is the rapporteur paper of Working Group 2 on Measuring Solar Abundances. The working group presented and discussed the different observations and methods for obtaining the elemental and isotopic composition of the Sun, and critically reviewed their results and the accuracies thereof. Furthermore, a few important yet unanswered questions were identified, and the potential of future missions to provide answers was assessed. . Title: Visible Imager / Magnetograph: summary of splinter session Authors: von der Lühe, O.; Fleck, B. Bibcode: 2001ESASP.493..149V Altcode: 2001sefs.work..149V Both splinter sessions for the Visible Imager and Magnetograph (VIM) were well attended by approximately 30 participants. The goals of the session was to review the scientific objectives for VIM, to discuss specific technological issues, and to refine the approach to science operation during all orbital phases. The session was closed by the formation of a definition team which will look in detail into these matters in order to prepare a VIM Phase A proposal. Title: Solar Orbiter, a high-resolution mission to the Sun and inner heliosphere Authors: Marsch, E.; Harrison, R.; Pace, O.; Antonucci, E.; Bochsler, P.; Bougeret, J. -L.; Fleck, B.; Langevin, Y.; Marsden, R.; Schwenn, R.; Vial, J. -C. Bibcode: 2001ESASP.493D..11M Altcode: 2001sefs.workD..11M Solar Orbiter will provide, at very high spatial (35 km pixel size) and temporal resolution, novel observations of the solar atmosphere and unexplored inner heliosphere. It will achieve its wide-ranging scientific aims with a suite of sophisticated instruments through an innovative orbit design. Unprecedented observations will be made in the heliosynchronous segments of the orbits at heliocentric distances near 45 Rsolar and out of the ecliptic plane at the highest heliographic latitudes of 30° - 38°. The first near-Sun interplanetary measurements together with concurrent remote-sensing observations of the Sun and its corona will permit us to determine and understand, through correlative studies, the characteristics of the solar wind and energetic particles in close linkage with the plasma and radiation conditions in the source regions on the Sun. Solar Orbiter will deliver the first images of the polar regions and the far side of the Sun invisible from the Earth. Title: Solar encounter Authors: Battrick, Bruce; Sawaya-Lacoste, H.; Marsch, E.; Martinez Pillet, V.; Fleck, B.; Marsden, R. Bibcode: 2001ESASP.493.....B Altcode: 2001sefs.work.....B The prime objectives of the workshop were to: inform the community about the science opportunities of the Solar Orbiter mission; to provide a forum for sharpening and focussing the science goals; allow the hardware groups and instrument proposers to critically review the payload; establish international contacts and collaborations. Title: Highlights from SOHO and Future Space Missions Authors: Fleck, Bernhard Bibcode: 2001ASSL..259....1F Altcode: 2001dysu.conf....1F The Solar and Heliospheric Observatory (SOHO) has provided an unparalleled breadth and depth of information about the Sun, from its interior, through the hot and dynamic atmosphere, out to the solar wind. Analysis of the helioseismology data from SOHO has shed new light on a number of structural and dynamic phenomena in the solar interior, such as the absence of differential rotation in the radiative zone, subsurface zonal and meridional flows, sub-convection-zone mixing, a possible circumpolar jet, and very slow polar rotation. Evidence for an upward transfer of magnetic energy from the Sun's surface toward the corona has been established. The ultraviolet instruments have revealed an extremely dynamic solar atmosphere where plasma flows play an important role. Electrons in coronal holes were found to be relatively ``cool", whereas heavy ions are extremely hot and have highly anisotropic velocity distributions. The source regions for the high speed solar wind has been identified and the acceleration profiles of both the slow and fast solar wind have been measured. This paper tries to summarize some of the most recent findings from the SOHO mission. Present plans for future solar space missions are also briefly discussed. Title: Active Region Oscillations: Results from SOHO JOP 097 Authors: O'Shea, E.; Fleck, B.; Muglach, K.; Sütterlin, P. Bibcode: 2001AGUSM..SH41A02O Altcode: We present here an analysis of data obtained in a sunspot region, using the Coronal Diagnostic Spectrometer (CDS) on SOHO. These data were obtained in the context of the Joint Observing Program (JOP) 97 which, together with CDS, included the Michelson Doppler Imaging (MDI) instrument on SOHO, the TRACE satellite and various ground based observatories, e.g. the DOT on La Palma. Using the lines of Fe XVI 335, Mg IX 368, He I 584, O III 599, Mg X 624 and O V 624 of CDS time series data were obtained in the pore and plage regions of sunspots associated with active regions AR 9166, 9166 and 9169 between September 19-29 2000. In addition to the time series datasets we also obtained 240 arcsec x 240 arcsec raster images of the sunspot regions examined. Using different time series analysis techniques we analyse the different periods of oscillation found in time series datasets and present the results here. This research is part of the European Solar Magnetometry Network supported by the EC through the TMR programme. Title: Correlated Wavelet Transforms of SOHO Chromospheric and Transition Region Timeseries Observations Authors: McIntosh, S. W.; Fleck, B. Bibcode: 2001AGUSM..SH41A03M Altcode: We consider the wavelet transform study of correlated SOHO (SUMER, CDS and EIT) time-series observations with a view to understanding inter-network plasma structure along the line-of-sight. By implementing wavelet transforms in a novel way we able to study the behavior of upward propagating wave-packets as a function of their height in the atmosphere. Using this information we will infer properties of the inter-network thermodynamic plasma structure of the chromosphere and transition region. Title: Helioseismology - What is Next? Authors: Scherrer, P. H.; Fleck, B.; Ulrich, R. K. Bibcode: 2001AGUSM..SP22A09S Altcode: The helioseismology instruments on SOHO have produced a rich set of new insights into the solar interior. Combined with GONG and other ground-based networks these instruments have, for the most part, met the goals set for them. These instruments have demonstrated the usefulness of helioseismic techniques for imaging solar interior structure and motions but do not have all the capabilities necessary to fully exploit the method. Future mission plans call for pushing helioseismic imaging to regions nearer the surface, to higher latitudes, and deeper into the interior. The capabilities of the planned or possible instruments on the Solar Dynamics Observatory, Solar Orbiter, and Farside/Safari missions will enable these presently inaccessible domains to be exploited. Title: Space Weather Aspects of the Solar Orbiter Mission Authors: Fleck, B.; Marsden, R. Bibcode: 2001AGUSM..SH22C06F Altcode: Approved in October 2000 by ESA's Science Programme Committee as a flexi-mission, the Solar Orbiter will study the Sun and unexplored regions of the inner heliosphere from a unique orbit that brings the probe to within 45 solar radii of our star, and to solar latitudes as high as 38 deg. This orbit will allow the Solar Orbiter to make fundamental contributions to our understanding of the transient phenomena driving space weather, including coronal mass ejections (CMEs) and flare-related effects. Being closer to the sources of such transients in the solar atmosphere, the Solar Orbiter will be ideally located to measure the input into the heliosphere and to determine the boundary conditions near the Sun. The scientific payload to be carried by the probe will include a sophisticated remote-sensing package, as well as state-of-the-art in situ instruments. The multi-wavelength, multi-disciplinary approach of the Solar Orbiter, combined with its novel location, represents a powerful tool for studies of the influence of space weather-related events on interplanetary space. Title: Active region oscillations Authors: O'Shea, E.; Banerjee, D.; Doyle, J. G.; Fleck, B.; Murtagh, F. Bibcode: 2001A&A...368.1095O Altcode: We report here on an investigation of high frequency oscillations in active regions, carried out using high cadence observations of O V 629 Å, Mg Ix 368 Å and Fe Xvi 335 Å, with the Coronal Diagnostic Spectrometer (cds) on soho. Using the techniques of wavelet analysis on various temporal series datasets, we find that certain oscillation frequencies are favoured for each line. We find furthermore that a ~ 5 min oscillation signature is commonly present in all lines, suggesting a coupling of the photospheric driver with the transition region and coronal loop modes. We report on the tendency for higher frequency oscillations to be present at lower intensity values, suggesting that higher frequency oscillations occur in interloop regions or at loop boundaries, possibly as a result of some resonant absorption process. In addition, we find that the coronal lines of Fe Xvi and Mg Ix show more significant oscillations in the velocity than in the intensity, which suggests that in the velocity we measure additional non-compressive wave modes not visible in the intensity. As this effect is not seen in the transition region line of O V it would seem that these additional non-compressive modes are produced in and limited to the corona. We suggest that there are two main mechanisms responsible for the observed oscillations; either resonant Alfvén and/or fast kink waves or propagating slow magnetoacoustic waves, both present in coronal loops. Title: Solar Orbiter Authors: Fleck, B.; Marsden, R.; Pace, O. Bibcode: 2001ESABu.105...56F Altcode: The scientific goals of the Solar Orbiter are to: - determine in-situ the properties and dynamics of plasma, fields and particles in the near-Sun heliosphere - investigate the fine-scale structure and dynamics of the Sun's magnetised atmosphere, using close-up, high-resolution remote sensing - identify the links between activity on the Sun's surface and the resulting evolution of the corona and inner heliosphere, using solar corotation passes - observe and fully characterise the Sun's polar regions and equatorial corona from high latitudes. Title: On the nature of network oscillations Authors: Banerjee, D.; O'Shea, E.; Doyle, J. G.; Goossens, M.; Fleck, B. Bibcode: 2001ESASP.464..175B Altcode: 2001soho...10..175B We examine time-series of spectral data obtained from the Solar Ultraviolet Measurements of Emitted Radiation instrument (SUMER), on board SOHO in the period 10-31 July 1996. Observations were obtained in lines, ranging in temperature from 12,000 K to 106K, covering the low chromosphere to the corona. In this short contribution we report on the time series analysis on one of these dataset, using wavelet methods, of small individual network regions in the quiet Sun. The wavelet analysis allows us to derive the duration as well as the periods of the oscillations. The statistical significance of the oscillations was estimated by using a randomisation method. The oscillations are considered to be due to waves, which are produced in short bursts with coherence times of about 10-20 minutes. The low chromospheric and transition region lines show intensity and velocity power in the 2.4 mHz range. The observed 2-4 mHz network oscillations can be interpreted in terms of kink and sausage waves propagating upwards along thin magnetic flux tubes. The kink waves can be generated by random foot-point motions, e.g. by exploding granules, at the photospheric level. As they propagate within flux tubes, their amplitude grows exponentially with height and becomes non-linear. The waves can thereby undergo a mode transformation and become sausage type waves, which are more easily detected on the disk. Title: Solar Orbiter - A high resolution mission to the Sun and the inner heliosphere (Oral papers and posters which were given at the conference, but for which no manuscripts were submitted) Authors: Marsch, E.; Fleck, B.; Schwenn, R. Bibcode: 2001ohnf.conf..445M Altcode: No abstract at ADS Title: From solar min to solar max: half a solar cycle of SOHO observations Authors: Brekke, P.; Fleck, B. Bibcode: 2001ICRC...27I..21B Altcode: The Solar and Heliospheric Observatory (SOHO) has provided an unparalleled breadth and depth of information about the Sun, from its interior, through the hot and dynamic atmosphere, out to the solar wind. Analysis of the helioseismology data from SOHO has shed new light on a number of structural and dynamic phenomena in the solar interior, such as the absence of differential rotation in the radiative zone, subsurface zonal and meridional flows, subconvection-zone mixing, a possible circumpolar jet, and very slow polar rotation. Evidence for an upward transfer of magnetic energy from the Sun's surface toward the corona has been established. The ultraviolet instruments have revealed an extremely dynamic solar atmosphere where plasma flows play an important role. Electrons in coronal holes were found to be relatively `cool', whereas heavy ions are extremely hot and have highly anisotropic velocity distributions. The source regions for the high speed solar wind has been identified and the acceleration profiles of both the slow and fast solar wind have been measured. This paper tries to summarize some of the findings from the SOHO mission from the past five years. Title: Solar Orbiter, a High-Resolution Mission to the Sun and Inner Heliosphere Authors: Marsch, E.; Antonucci, E.; Bochsler, P.; Bougeret, J. -L.; Fleck, B.; Harrison, R.; Marsden, R.; Schwenn, R.; Vial, J. -C. Bibcode: 2001IAUS..203..565M Altcode: The scientific rationale of the Solar Orbiter (SO) is to provide, at high spatial and temporal resolution, observations of the solar atmosphere and unexplored inner heliosphere. The most interesting and novel observations will be made in the almost heliosynchronous segments of the orbits at heliocentric distances near 45 Rodot and out-of-ecliptic at the highest heliographic latitudes of 38 degrees. The SO will achieve its many and varied aims with a suite of small and innovative instruments through a clever choice of orbits. The first near-Sun interplanetary measurements together with concurrent remote observations of the Sun will permit us to determine and understand, through correlative studies, the characteristics of the solar wind and energetic particles in close linkage with the plasma and radiation conditions in their source regions on the Sun. The SO will, during the high-latitude orbital passes, provide the first observations of the Sun's polar regions as seen from outside the ecliptic and also measure the magnetic field at the poles. Title: Recent insights into the physics of the sun and heliosphere : highlights from SOHO and other space missions : IAU Symposium 203, proceedings of the 24th General Assembly of the IAU held at Manchester, United Kingdom, 7-11 August 2000 Authors: Brekke, Pål; Fleck, Bernhard; Gurman, Joseph B. Bibcode: 2001IAUS..203.....B Altcode: No abstract at ADS Title: Active region oscillations Authors: O'Shea, E.; Banerjee, D.; Doyle, J. G.; Fleck, B.; Murtagh, F. Bibcode: 2001ESASP.464..223O Altcode: 2001soho...10..223O We report here on an investigation of high frequency oscillations in active regions, carried out using high cadence observations of O V 629 Å, Mg IX 368 Å and Fe XVI 335 Å with the Coronal Diagnostic Spectrometer (CDS) on SoHO. Using the techniques of wavelet analysis on various temporal series datasets, we find that certain bands of oscillation frequency are favoured for each line. We report on the tendency for higher frequency oscillations to correspond to lower intensity values, suggesting that higher frequency oscillations occur in inter-loop regions or at loop boundaries, and further that some resonant absorption process is perhaps at work at these locations. We suggest that there are two possible mechanisms for the observed oscillations; either resonant Alfvén waves or resonant fast kink waves in coronal loops. Title: Quiet Sun Oscillation Packets Authors: Ireland, J.; McIntosh, S. W.; Fleck, B. Bibcode: 2000SPD....31.0132I Altcode: 2000BAAS...32..807I This paper combines the novel techniques of wavelet analysis and genetic algorithms to exploit SOHO-SUMER (Solar Ultraviolet Measurements of Emitted Radiation) data in a new way. The data consists of time series in O I 1306.03 Angstroms, Si II 1309.28 Angstroms, C I 1311.36 Angstroms, C II 1334.53 Angstroms, He I 584 Angstroms, O I 1152 Angstroms, and C III 1176 Angstroms tracking specific pieces of quiet Sun westward across the disk. To analyse this data, genetic algorithms (McIntosh et. al, A.& A. Suppl. Ser., 132, 145, 1998) are used to fit quiet Sun emission spectra, allowing the unbiassed determination of spectral properties such as total line intensity and Doppler velocity. Time series of line intensity and Doppler velocity are formed which are then analysed using wavelet techniques, permitting the distinguishing of distinct oscillation wave packets in the time series. Correlations of wave packets between different lines and physical quantities are discussed, as are the distributions of oscillation packets seen. Title: Solar Orbiter --- A High Resolution Mission to the Sun and Inner Heliosphere Authors: Fleck, B.; Marsch, E.; Schwenn, R.; Antonucci, E.; Bochsler, P.; Bougeret, J. -L.; Harrison, R. A.; Marsden, R.; Vial, J. -C. Bibcode: 2000SPD....31.0296F Altcode: 2000BAAS...32..828F The scientific rationale of the Solar Orbiter (SO) is to provide, at high spatial and temporal resolution, observations of the solar atmosphere and unexplored inner heliosphere. The most interesting and novel observations will be made in the almost heliosynchronous segments of the orbits at heliocentric distances near 45 Rsun and out-of-ecliptic at heliographic latitudes of up to 38o. By going to 45 Rsun the SO will allow remote sensing of the solar atmosphere with unprecedented spatial resolution, and the almost heliosynchronous orbit segments will permit us to disentangle spatial and temporal variations in the solar wind in close linkage with the plasma and radiation conditions in the source regions of the Sun. The strawman payload encompasses two instrument packages: Heliospheric Instruments --- high-res visible light telescope and magnetograph (<40 km), high-res X-ray/EUV imager (<30 km), high-res EUV spectrometer (<100 km), EUV and visible-light coronagraphs, solar neutron and γ -ray detectors, radiometers. Heliospheric Instruments --- solar wind analyzer, magnetometer, energetic particle detectors, IP dust detector, plasma wave analyser, radio experiment, neutral particle detector. Using solar electric propulsion (SEP) in conjunction with multiple planet swing-by manoeuvres, it will take SO two years to reach a perihelion of 45 Rsun at an orbital period of 149 days, with an inclination ranging from 6.7o to 23.4o w.r.t. the ecliptic. During an extended mission phase of about 2 years the inclination will increase to 31.7o, leading to a maximum heliographic latitude of 38.3o. The SO was one of the about 40 responses to the Call for Proposals for the next two "flexi-missions" (F2 and F3) within ESA's Scientific Programme. At its meeting on 1 March 2000, ESA's Space Science Advisory Committee recommended the Solar Orbiter among 5 other proposals for an assessment study. Launch is expected by the end of the decade. Title: Four years of SOHO discoveries - some highlights. Authors: Fleck, B.; Brekke, P.; Haugan, S.; Duarte, L. S.; Domingo, V.; Gurman, J. B.; Poland, A. I. Bibcode: 2000ESABu.102...68F Altcode: Analysis of the helioseismic data from SOHO has shed new light on solar and heliosheric physics: the structure and dynamics of the solar interior, the heating and dynamics of the solar corona, and the acceleration and composition of the solar wind. Title: Dynamics of Chromiospheric and Transition Region Lines Observed with SOHO/SUMER and the GCT/Tenerife Authors: Muglach, K.; Fleck, B.; Schühle, U.; Stolpe, F.; Foing, B. H.; Wilhelm, K. Bibcode: 2000AdSpR..25.1731M Altcode: High-resolution spectroscopic observations of the quiet Sun have been carried out in September 1996 at the German Gregory Coudé Telescope (GCT) in Tenerife and in May 1997 with the SUMER instrument onboard SOHO. Time sequences of spectra in the visible and near infrared as well as in the ultraviolet have been taken, covering a range of heights from the solar photosphere up into the transition region. In this contribution we present the dynamical behaviour observed at the various heights in the solar atmosphere Title: Waves in the Quiet Sun's Chromosphere Authors: Muglach, K.; Fleck, B. Bibcode: 1999ESASP.446..499M Altcode: 1999soho....8..499M High resolution spectroscopic observations of the quiet sun have been carried out in May 1997 with the SUMER instrument onboard of SOHO. Nine hour time sequences at disk center in various UV lines have been taken, covering a range of height between the solar chromosphere and the transition region. In this contribution we will present the dynamics we find in the various heights/temperature regimes in the solar atmosphere. Title: Observational Constraints on Models of the Solar Background Spectrum Authors: Straus, Th.; Severino, G.; Deubner, F. -L.; Fleck, B.; Jefferies, S. M.; Tarbell, T. Bibcode: 1999ApJ...516..939S Altcode: We discuss the properties of the solar background signal as observed in high-quality, l-ν power and phase difference spectra of the continuum (C), velocity (V), and line intensity (I) fluctuations of the Ni I 6768 Å line. These spectra were generated from high-resolution images acquired by the Michelson Doppler Imager on board SOHO.

We confirm that the background signal in the velocity power spectra can be reproduced by a composite model with two quasi-stationary components, describing large-scale and small-scale convective motions, and a periodic component. The line and continuum intensity power spectra require additional quasi-stationary and periodic components. The extra quasi-stationary component dominates the intensity and continuum background signals over the spectral region where the I-V phase difference spectra show essentially constant negative phase difference: i.e., below and in between the p-mode ridges (called the plateau-interridge regime by Deubner et al.). Since the I-V phase between the p-mode ridges is not random, the solar background beneath the p-modes must be considered as coherent. We thus speculate that the negative phase regime may be the manifestation of a correlated background. Such a background has been proposed to explain the opposite sense of the asymmetries of the p-mode line profiles in velocity and brightness oscillations. Title: Diary of a drama. Authors: Vandenbussche, F.; Fleck, B. Bibcode: 1999AsNow..13...56V Altcode: 1999AstNw..13...56V "Focus: Basking in the Sun". When on 24 Jun 1998 contact was lost with SOHO a rescue mission was immediately started. Title: On wave equations and cut-off frequencies of plane atmospheres Authors: Schmitz, F.; Fleck, B. Bibcode: 1998A&A...337..487S Altcode: This paper deals with the one-dimensional vertical propagation of linear adiabatic waves in plane atmospheres. In the literature there are various representations of the standard form of the wave equation from which different forms of the so called cut-off frequency are inferred. It is not uncommon that statements concerning the propagation behavior of waves are made which are based on the height dependence of a cut-off frequency. In this paper, first we critically discuss concepts resting on the use of cut-off frequencies. We add a further wave equation to three wave equations previously presented in the literature, yielding an additional cut-off frequency. Comparison among the various cut-off frequencies of the VAL-atmosphere reveals significant differences, which illustrate the difficulties of interpreting a height dependent cut-off frequency. We also discuss the cut-off frequency of the parabolic temperature profile and the behavior of the polytropic atmosphere. The invariants of the four wave equations presented contain first and second derivatives of the adiabatic sound speed. These derivatives cause oscillations and peaks in the space dependent part of the invariants, which unnecessarily complicate the discussion. We therefore present a new form of the wave equation, the invariant of which is extremely simple and does not contain derivatives of the thermodynamic variables. It is valid for any LTE equation of state. It allows us to make effective use of strict oscillation theorems. We calculate the height-dependent part of the invariant of this equation for the VAL-atmosphere including ionization and dissociation. For this real atmosphere, there is no obvious correspondence between the behavior of the invariant and the temperature structure or the sound speed profile. The invariant of the wave equation is nearly constant around the temperature minimum. In the chromosphere, the invariant is almost linear. The case of the wave equation with a linear invariant is studied analytically. Title: NSO/AFRL/Sac Peak K-line Monitoring Program Authors: Keil, Stephen L.; Henry, Timothy W.; Fleck, Bernhard Bibcode: 1998ASPC..140..301K Altcode: 1998ssp..conf..301K No abstract at ADS Title: Phase spectra seen from space Authors: Straus, Th.; Deubner, F. -L.; Fleck, B.; Marmolino, C.; Severino, G.; Tarbell, T. Bibcode: 1998IAUS..185..455S Altcode: We discuss preliminary results of a study of the dynamics of the solar atmosphere including a first space based investigation of k-omega phase difference spectra between velocity and intensity perturbations. The data, including simultaneous line shift, line depth, and continuum intensity measurements at disk center, have been obtained from a MDI time series in its high resolution mode. Line depth and continuum intensity are used to calculate the line intensity which is the more frequently used parameter in phase difference studies. We compare the results to ground based observations. Title: K-ϖ Phase Spectra Obtained from Space Authors: Straus, Th.; Fleck, B.; Severino, G.; Deubner, F. -L.; Marmolino, C.; Tarbell, T. Bibcode: 1998ESASP.417..293S Altcode: 1998cesh.conf..293S No abstract at ADS Title: Wave Propagation in the Chromosphere and Transition Region: Where Have All the Shock Waves Gone? Authors: Fleck, B.; Steffens, S.; Deubner, F. -L.; Wilhelm, K.; Harrison, R.; Gurman, J. Bibcode: 1997SPD....28.0120F Altcode: 1997BAAS...29..882F We present first results from a joint observing program (SOHO JOP 26) involving SUMER, CDS and EIT on SOHO, coordinated with ground-based observations at the Vacuum Tower Telescope at Iza{\ n}a, Tenerife. The objective of this study is to characterize the wave propagation properties in the solar atmosphere, from the photosphere through the chromosphere up into the transition region. Particular emphasis is laid on the 3-min shock waves observed in the Ca II K line. How do they impact the transition region and what signature do they leave there and in the lower corona? The ground-based measurements comprise high resolution time series (both filtergrams and spectrograms) in Ca II K, Hα and Mgb_2. With SUMER we ran four sequences covering different temperature regimes: a) O I 1302, O I 1306, Si II 1309, C I 1311, C II 1334, C II 1335, b) Si I 1256, N V 1242, O V 629 c) He I 584, C III 1175, O I 1152, d) H I 1025, O VI 1031, O VI 1037. With CDS we took spectral time series in O VI 554, He I 584, He II 607, Mg IX 368, and O V 629 as well as wide-slit (90x240'') ``movies'' in He I 584, Mg IX 368 and O V 629, while EIT ran sub-field high cadence sequences in He II 304. Title: First Results from SOHO Authors: Fleck, B. Bibcode: 1997Ap&SS.258...57F Altcode: 1997ESAC....7...57F SOHO, the Solar and Heliospheric Observatory, is a project of international cooperation between ESA and NASA to study the Sun, from its deep core to the outer corona, and the solar wind. Three helioseismology instruments are providing unique data for the study of the structure and dynamics of the solar interior, from the very deep core to the outermost layers of the convection zone. A set of five complementary remote sensing instruments, consisting of EUV, UV and visible light imagers, spectrographs and coronagraphs, give us our first comprehensive view of the outer solar atmosphere and corona, leading to a better understanding of the enigmatic coronal heating and solar wind acceleration processes. Finally, three experiments complement the remote sensing observations by making in- situ measurements of the composition and energy of the solar wind and charged energetic particles, and another instrument maps the neutral hydrogen in the heliosphere and its dynamic change by the solar wind. This paper reports some of the first results from the SOHO mission. Title: The Whole Sun Catalogue Authors: Sanchez Duarte, L.; Fleck, B.; Bentley, R. Bibcode: 1997ASPC..118..382S Altcode: 1997fasp.conf..382S To maximize the scientific outcome of the wealth of solar observations available, it would be extremely useful to have a complete, central catalogue giving some basic information such as `where, when, what' about all solar observations made. This paper presents a proposal for such a catalogue based on the infrastructure developed for the SOHO Archive, but being independent of it. Our goal is to refine this proposal with the help of the JOSO group and to implement it by 1997. Title: First Results from SOHO on Waves Near the Solar Transition Region Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.; Schuhle, U.; Curdt, W.; Harrison, R.; Gurman, J.; Thompson, B. J.; Brekke, P.; Delaboudiniere, J. -P.; Lemaire, P.; Hessel, B.; Rutten, R. J. Bibcode: 1997ASPC..118..284S Altcode: 1997fasp.conf..284S We present first results from simultaneous observations with the CDS, EIT and SUMER instruments {please see Solar Physics 162 (1995) for a description of the instruments} onboard SOHO and the VTT at Tenerife. Our aim is to study the wave propagation, shock formation, and transmission properties of the upper chromosphere and transition region. The preliminary results presented here include the variation of velocity power spectra with height, difference in power between internetwork and network regions, and variations in mean flows displayed by different spectral lines. Title: Tracing CA K Grains Through the Chromosphere into the Transition Region Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K. Bibcode: 1997ESASP.404..685S Altcode: 1997cswn.conf..685S No abstract at ADS Title: The Solar and Heliospheric Observatory (SOHO) in 1996. Authors: Domingo, V.; Fleck, B.; Martens, P.; Sanchez, L. Bibcode: 1997joso.proc....4D Altcode: This report gives a brief overview of SOHO's scientific production in its first year of operation. Title: Wave Propagation in the Chromosphere and Transition Region Authors: Steffens, S.; Deubner, F. -L.; Fleck, B.; Wilhelm, K.; Harrison, R.; Gurman, J. Bibcode: 1997ESASP.404..679S Altcode: 1997cswn.conf..679S No abstract at ADS Title: The first results from SOHO. Authors: Fleck, B.; Švestka, Z. Bibcode: 1997frfs.book.....F Altcode: This volume contains papers reporting the first scientific results from the SOHO mission as well as descriptions of the in-flight performance of some of the instruments. A CD-ROM with multimedia material is included as an integral part of this volume. Reprinted from Sol. Phys., Vol. 170, No. 1 (Jan 1997) (see AAA, Vol. 67) and Vol. 175, No. 2 (Oct 1997) (see AAA, Vol. 68). Title: First Results from SOHO. Authors: Fleck, B. Bibcode: 1997RvMA...10..273F Altcode: No abstract at ADS Title: The first results from SOHO. Authors: Domingo, V.; Fleck, B.; Poland, A. Bibcode: 1996ESABu..87....7D Altcode: SOHO, launched by an Atlas II-AS from Cape Canaveral on 2 December 1995, was inserted into its halo orbit around the L1 Lagrangian point. Typical examples of the unique results being obtained with SOHO's instruments are presented. Title: High resolution Lyalpha images obtained with the transition region camera (TRC): a comparison with Hα observations Authors: Wiik, J. E.; Foing, B. H.; Martens, P.; Fleck, B.; Schmieder, B. Bibcode: 1996AdSpR..17d.105W Altcode: 1996AdSpR..17..105W Comparing high spatial resolution (~ 1'') images observed in Lyalpha with the Transition Region Camera (TRC) and in Hα at Sacramento Peak and Meudon Observatories, we notice that some structures are well correlated in the two lines (plages), while others are less correlated (chromospheric network, filaments). This is an indication of the inhomogeneous distribution of physical parameters in these structures. Title: Preface Authors: Fleck, B.; Domingo, V.; Poland, A. Bibcode: 1995SoPh..162D...9F Altcode: No abstract at ADS Title: The SOHO mission. Authors: Fleck, B.; Domingo, V.; Poland, A. I. Bibcode: 1995SoPh..162.....F Altcode: SOHO, the Solar and Heliospheric Observatory, is a project of international cooperation between ESA and NASA to study the Sun, from its deep core to the outer corona. This special issue is dedicated to the SOHO payload and to its operation. Title: The SOHO Mission: an Overview Authors: Domingo, V.; Fleck, B.; Poland, A. I. Bibcode: 1995SoPh..162....1D Altcode: The Solar and Heliospheric Observatory (SOHO) is a space mission that forms part of the Solar-Terrestrial Science Program (STSP), developed in a collaborative effort by the European Space Agency (ESA) and the National Aeronautics and Space Administration (NASA). The STSP constitutes the first "cornerstone" of ESA's long-term programme known as "Space Science — Horizon 2000". The principal scientific objectives of the SOHO mission are a) to reach a better understanding of the structure and dynamics of the solar interior using techniques of helioseismology, and b) to gain better insight into the physical processes that form and heat the Sun's corona, maintain it and give rise to its acceleration into the solar wind. To achieve these goals, SOHO carries a payload consisting of 12 sets of complementary instruments. SOHO is a three-axis stabilized spacecraft with a total mass of 1850 kg; 1150 W of power will be provided by the solar panels. The payload weighs about 640 kg and will consume 450 W in orbit. SOHO will be launched by an ATLAS II-AS and will be placed in a halo orbit around the Sun-Earth L1 Lagrangian point where it will be continuously pointing to Sun centre with an accuracy of 10 arcsec. Pointing stability will be better than 1 arcsec over 15 min intervals. The SOHO payload produces a continuous science data stream of 40 kbits/s which will be increased by 160 kbits/s whenever the solar oscillations imaging instrument is operated in its highrate mode. Telemetry will be received by NASA's Deep Space Network (DSN). Planning, coordination and operation of the spacecraft and the scientific payload will be conducted from the Experiment Operations Facility (EOF) at NASA's Goddard Space Flight Center (GSFC). Title: Is there a chromospheric mode at 6 mHz? Authors: Steffens, S.; Deubner, F. -L.; Hofmann, J.; Fleck, B. Bibcode: 1995A&A...302..277S Altcode: We present time series of Na D_1_ and Ca K_2v_ filtergrams of the quiet sun obtained simultaneously with the Vacuum Tower Telescope at Observatorio del Teide, Tenerife. Special interest is taken in the distribution of power in the Fourier domain. We distinguish power "on" and "between" the ridges of the p-modes and pseudo p-modes. The latter are found to extend beyond the acoustic cutoff frequency up to 12mHz in Na D_1_ and 8.5mHz in Ca K_2v_. Most of the power of the broad chromospheric feature detected in Ca II K by Harvey et al. (???) in the background of a one-dimensional power spectrum is found preferentially between the p-mode ridges at about 6mHz, as our two-dimensional analysis reveals. This behaviour would be consistent with the nature of "avoided crossing" (Ulrich & Rhodes ???) of a chromospheric mode and the p-modes. We note that the center frequency of the interridge feature appears independent of height, whereas the power distribution of the p-mode ridges extends to higher frequencies as height increases. We suppose that different mechanisms are responsible for the generation of these two wave fields. In our investigation the broad band of enhanced power at 6mHz is even more conspicuous in Na D_1_ than in Ca K_2v_. Title: On the generation of resonance oscillations in plane atmospheres. Authors: Schmitz, F.; Fleck, B. Bibcode: 1995A&A...301..483S Altcode: The paper deals with some selected properties of linear 1-D resonance oscillations of plane stratified atmospheres. First, we study the response of a bounded isothermal atmosphere to a velocity pulse injected at the bottom of the atmosphere. For a family of pulses, we calculate the Lagrangian density perturbation at the bottom as this quantity indicates the response of the whole atmosphere. The analytical expressions give insight into details of the onset and the decay of the oscillation for finite times. We find that the principle asymptotic term governs the resonance oscillation only at large times. Further, we consider the influence of weak radiative damping on the oscillation. To study conditions for the existence of a resonance oscillation in non-isothermal atmospheres, we use transformations of the wave equation. By suitable transformations of the wave equation of a non-isothermal atmosphere to the wave equation of the homogeneous gas, we obtain some particular temperature stratifications which do not show the resonance oscillation. The solution of the wave equation of polytropic atmospheres with negative half-integral index is discussed. By transformations of the wave equation to the wave equation of the isothermal atmosphere, we obtain temperature structures of atmospheric layers the dynamical behavior of which is equal to the behavior of the isothermal atmosphere. Further, we determine temperature stratifications which do not produce a real resonance oscillation, but significant distortions of sharp pulses. Title: Phase Analysis of the K-Grain Excitation Pattern Authors: Hofmann, J.; Deubner, F. –L.; Steffens, S.; Fleck, B. Bibcode: 1995ESASP.376b.493H Altcode: 1995help.confP.493H; 1995soho....2..493H No abstract at ADS Title: On the Phenomenology of K-Grains Authors: Steffens, S.; Deubner, F. –L.; Hofmann, J.; Fleck, B. Bibcode: 1995ESASP.376b.487S Altcode: 1995soho....2..487S; 1995help.confP.487S No abstract at ADS Title: Is There an Atmospheric Mode Near 6 mHz? Authors: Steffens, S.; Deubner, F. –L.; Hofmann, J.; Fleck, B. Bibcode: 1995ESASP.376b.481S Altcode: 1995soho....2..481S; 1995help.confP.481S No abstract at ADS Title: Helioseismology Authors: Hoeksema, J. T.; Domingo, V.; Fleck, B.; Battrick, Bruce Bibcode: 1995ESASP.376b....H Altcode: 1995help.confP....H No abstract at ADS Title: SOHO: The Solar and Heliospheric Observatory Authors: Domingo, V.; Fleck, B.; Poland, A. I. Bibcode: 1995SSRv...72...81D Altcode: The Solar and Heliospheric Observatory (SOHO), together with the Cluster mission, constitutes ESA's Solar Terrestrial Science Programme (STSP), the first “Cornerstone” of the Agency's long-term programme “Space Science — Horizon 2000”. STSP, which is being developed in a strong collaborative effort with NASA, will allow comprehensive studies to be made of the both the Sun's interior and its outer atmosphere, the acceleration and propagation of the solar wind and its interaction with the Earth. This paper gives a brief overview of one part of STSP, the SOHO mission. Title: On the reflection of linear 3-D hydrodynamic waves in a plane atmosphere by an ionization step. Authors: Schmitz, F.; Fleck, B. Bibcode: 1995A&A...294..206S Altcode: We investigate the influence of a variable ionization rate on the propagation behavior of evanescent and acoustic waves in an isothermal atmosphere. For isothermal waves in a pure atomic hydrogen atmosphere the wave equation of the total pressure perturbation can be transformed into the hypergeometric equation, from which by a linear transformation formula of the hypergeometric function simple analytical expressions for the reflection of waves can be obtained. For vertical evanescent waves we compare the reflection caused by a continuous ionization step with that of a corresponding temperature step for which in the 1-D case an analytical approach exists. The reflection is significantly different for the two cases, although the sound speed is equal in both atmospheres. We also consider the reflection by a discontinuous ionization step and compare it with the continuous model in order to study the usefulness of such an approximation. We also compare the reflection of waves by a discontinuous ionization step with the reflection by a discontinuous temperature step. We again find basic differences between the two reflection mechanisms which are due to the different behaviour of the first derivatives of the velocity and the pressure perturbation at the discontinuous step. Title: Is there an atmospheric mode near 6 mHz? Authors: Steffens, S.; Deubner, F. -L.; Hofmann, J.; Fleck, B. Bibcode: 1995AGAb...11..138S Altcode: No abstract at ADS Title: He 10830 Angstrom Confirms Non-Propagation Component of Chromospheric Oscillations Authors: Hofmann, J.; Deubner, F. -L.; Fleck, B. Bibcode: 1995ASPC...76..342H Altcode: 1995gong.conf..342H No abstract at ADS Title: What Have We Learned About Chromospheric Oscillations from HeI 10830Å? Authors: Fleck, B.; Deubner, F. -L.; Hofmann, J. Bibcode: 1995itsa.conf..437F Altcode: Time series of He I 10830 spectra taken simultaneously with spectra of other chromospheric lines (Ca II 8542 Å and Ca II K) are analyzed to study wave propagation in the solar chromosphere. Rather than providing conclusive answers to some of the long standing questions concerning chromospheric oscillations, the new results derived from the He 10830 line raise new puzzling questions. The spatio-temporal wave pattern deduced from the Doppler displacements of the He line differs significantly from those of the two Ca II lines, while the phase difference between the Doppler displacements of He 10830 and Ca K_3 stays close to zero in the whole frequency range observed. This is difficult to reconcile with the low oscillation amplitude observed in the He 10830 line (RMS≈1100 m/s), which is less than half the velocity amplitude derived from the core displacement of Ca K_3. Another surprising result is that the Ca K ``bright point'' events are only barely visible in the Doppler displacement of the He 10830 line. Title: The SOHO mission Authors: Fleck, B.; Domingo, V.; Poland, A. Bibcode: 1995somi.book.....F Altcode: No abstract at ADS Title: SOHO: The Solar and Heliospheric Observatory Authors: Domingo, V.; Fleck, B.; Poland, A. I. Bibcode: 1995hlh..conf...81D Altcode: No abstract at ADS Title: Books-Received - Mass Supply and Flows in the Solar Corona Authors: Fleck, B. Bibcode: 1995Sci...267..119F Altcode: No abstract at ADS Title: The SOHO Mission Authors: Fleck, B. Bibcode: 1995LNP...444..233F Altcode: 1995cmer.conf..233F SOHO, the Solar and Heliospheric Observatory, is a joint ESA/NASA mission to study the sun from its interior to, and including, the solar wind in interplanetary space. It is currently scheduled for launch in 1995. In this paper a mission overview is given, comprising scientific objectives, payload, spacecraft, operations, and data and ground system. Title: On the phenomenology of K-grains. Authors: Steffens, S.; Deubner, F. -L.; Hofmann, J.; Fleck, B. Bibcode: 1995AGAb...11..140S Altcode: No abstract at ADS Title: Helioseismology Authors: Hoeksema, J. T.; Domingo, V.; Fleck, B.; Battrick, Bruce Bibcode: 1995ESASP.376a....H Altcode: 1995heli.conf.....H No abstract at ADS Title: The SOHO mission Poland. Authors: Fleck, B.; Domingo, V.; Poland, Arthur I. Bibcode: 1995sohp.book.....F Altcode: 1995QB521.S5828.... No abstract at ADS Title: Preparing for SOHO: results from the transition region camera Authors: Wiik, J. E.; Foing, B. H.; Schmieder, B.; Martens, P.; Fleck, B. Bibcode: 1994ESASP.373..433W Altcode: 1994soho....3..433W No abstract at ADS Title: The scientific payload of the space-based Solar and Heliospheric Observatory (SOHO) Authors: Domingo, V.; Fleck, B.; Poland, A. I. Bibcode: 1994SSRv...70....7D Altcode: The space-based Solar and Heliospheric Observatory (SOHO) is a joint venture of ESA and NASA within the frame of the Solar Terrestrial Science Programme (STSP), the first “Cornerstone” of ESA's long-term programme “Space Science — Horizon 2000”. The principal scientific objectives of the SOHO mission are: a) a better understanding of the structure and dynamics of the solar interior using techniques of helioseismology, and b) a better insight into the physical processes that form and heat the Sun's corona, maintain it and give rise to its acceleration into the solar wind. To achieve these goals, SOHO carries a payload consisting of 12 sets of complementary instruments which are briefly described here. Title: SOHO operations and ground system Authors: Poland, A. I.; Domingo, V.; Fleck, B. Bibcode: 1994SSRv...70...13P Altcode: SOHO is a joint ESA/NASA mission to study the sun from its interior to, and including, the solar wind in interplanetary space. It is currently scheduled for launch in 1995. After launch SOHO with be operated from the Experiment Operations Facility (EOF) at Goddard Space Flight Center (GSFC). The EOF will consist of facilities for instrument commanding, data reception, data reduction and data analysis. In this paper the operations concepts including instrument ground commanding from the EOF and communications capabilities between the EOF and ground observatories and the public networks in general will be described. Title: Foreword Authors: Fleck, B.; Noci, G.; Poletto, G. Bibcode: 1994SSRv...70D..17F Altcode: No abstract at ADS Title: Mass Supply and Flows in the Solar Corona - Conference Authors: Fleck, B.; Noci, G.; Poletto, G. Bibcode: 1994SSRv...70....1F Altcode: No abstract at ADS Title: Mass supply and flows in the solar corona. Proceedings. 2. SOHO Workshop, Marciana Marina, Island of Elba (Italy), 27 Sep - 1 Oct 1993. Authors: Fleck, B.; Noci, G.; Poletto, G. Bibcode: 1994SSRv...70.....F Altcode: This workshop focused on the following topics: 1. Fine scale structures. 2. Loops and prominences. 3. Coronal streamers. 4. Coronal holes and solar wind. Each of these four topics was introduced by an observational and a theoretical overview highlighting the most recent advances in their area. A third review illustrated how SOHO might help in solving open problems. Title: On the propagation of linear 3-D hydrodynamic waves in plane non-isothermal atmospheres Authors: Schmitz, F.; Fleck, B. Bibcode: 1994A&AS..106..129S Altcode: Closed solutions of the time independent wave equation of 3-D linear adiabatic waves in non-isothermal atmospheres are presented and discussed. Three temperature stratifications are considered applying the full wave equation without any approximations: a continuous temperature step between two asymptotically isothermal layers, an exponentially decreasing, and an exponentially increasing temperature stratification. In this first paper we present the fundamental systems, discuss general properties, and present some tools for more detailed investigations. For the exponential temperature stratifications, the wave equation is transformed to the hypergeometric equation. Linear transformation formulas are used to study details of the solutions. For the exponentially decreasing temperature stratification the second solution of the fundamental mode is calculated, and the convective and Rayleigh-Taylor instabilities are considered. In the case of the continuous temperature step the wave equation can be reduced to Heun's differential equation. Various representations of the solutions are presented and the continuation of the solutions is discussed. Title: On the strength of solar intra-network fields. Authors: Keller, C. U.; Deubner, F. -L.; Egger, U.; Fleck, B.; Povel, H. P. Bibcode: 1994A&A...286..626K Altcode: The combination of the German Vacuum Tower Telescope and the prototype of ZIMPOL I (Zuerich Imaging Stokes Polarimeter I), a novel, very sensitive imaging polarimeter, has resulted in the first spectra of solar intra-network (IN) fields in circular polarization. The sensitivity in terms of flux density is 0.7 Mx/cm^2^. While magnetic fields in solar spots, pores, plages, and in the network have predominantly kG field strengths, the magnetic field strength of the IN flux is a controversial subject due to the absence of direct measurements. We first summarize the current ideas on IN fields and examine previous arguments for their field strength. Our measurements of the magnetic line ratio formed between the amplitudes of the Stokes V profiles of Fe I 5247.1 A and Fe I 5250.2 A are consistent with a field strength well below 1 kG. Since the sensitivity of the magnetic line ratio becomes low for small field strengths, we can only set an upper limit on the field strength of IN fields of 500 G at the level of line formation with a probability of 68% and an upper limit of 1 kG with a probability of 95%. We emphasize that these are the first observations of a magnetic line ratio of unity near disk center. Title: On the correlation of magnetic field strength and inclination with continuum brightness of a sunspot penumbra. Authors: Hofmann, J.; Deubner, F. -L.; Fleck, B.; Schmidt, W. Bibcode: 1994A&A...284..269H Altcode: A fairly regular sunspot penumbra has been observed near disk center using a Stokes V polarimeter at the German Vacuum-Tower-Telescope in Izana, Tenerife. We obtained two-dimensional spectral data by scanning the limbside sector of the penumbra in steps of 1 arcsecond with the slit oriented parallel to the solar limb. From Stokes V and Stokes I spectra of four magnetically sensitive lines (FeI5247.1A, CrI5247.6A, FeI5250.2A, and FeI5250.7A) recorded with 1024 x 1024 pixel CCD cameras we have determined several magnetic parameters. The results of a correlation analysis show a clear relation between continuum brightness and magnetic field inclination, field lines beeing flatter in the dark penumbral filaments. We also find a correlation between field strength and brightness; this correlation is not uniform across the penumbra, however. Title: Non-linearities of chromospheric oscillations Authors: Deubner, F. -L.; Hofmann, J.; Kossack, E.; Fleck, B. Bibcode: 1994ASIC..433..155D Altcode: No abstract at ADS Title: Observations of Solar Oscillations in He 110830 Angstrom Authors: Fleck, B.; Deubner, F. -L.; Maier, D.; Schmidt, W. Bibcode: 1994IAUS..154...65F Altcode: No abstract at ADS Title: Wave propagation in the solar chromosphere: some new results from CaII K, CaII 8542 and HeI 10830 observations Authors: Fleck, B.; Deubner, F. -L.; Hofmann, J.; Steffens, S. Bibcode: 1994chdy.conf..103F Altcode: Time series of spectra taken simultaneously in the three chromospheric lines Ca II 8542 A, Ca II K, and He I 10830 AA are analyzed to study the wave propagation behaviour in the solar chromosphere. The V-V phase difference between the three chromospheric lines stays close to 0 deg in the whole frequency range observed and thus confirms previous observations of a non-propagating component dominating the acoustic wave spectrum in the solar chromosphere. In particular, the dominant 3-min oscillations observed in the core displacement of the Ca II 8542 and Ca K line are highly correlated, contrary to the numerical NLTE radiating shock dynamic simulations of Carlsson and Stein (1993) which revealed a significant phase delay between the two lines. The oscillation amplitude observed in the He 10830 line (RMS ~ 1100 m/s) is only about half the velocity amplitude derived from the core displacement of Ca K3. We also present a first He 10830 k-omega diagram. Title: SOHO Science Opportunities Authors: Fleck, B.; Domingo, V.; Poland, A. I. Bibcode: 1994scs..conf..609F Altcode: 1994IAUCo.144..609F The principal scientific objectives of the SOHO mission are: a) a better understanding of the structure and dynamics of the solar interior using techniques of helioseismology, and b) a better insight into the physical processes that form and heat the Sun's corona, maintain it and give rise to its acceleration into the solar wind. To achieve these goals, SOHO carries a payload consisting of 12 sets of complementary instruments which are briefly described here. Title: SOHO Operations Authors: Fleck, B.; Domingo, V.; Poland, A. I. Bibcode: 1994scs..conf..614F Altcode: 1994IAUCo.144..614F SOHO, the Solar and Heliospheric Observatory, is currently scheduled for launch in 1995. After launch SOHO will be operated from the Experiment Operations Faciliy (EOF) at Goddard Space Flight Center (GSFC). The EOF will consist of facilities for instrument commanding, data reception, data reduction and data analysis. This paper briefly describes the operations concepts. Title: Mass supply and flows in the solar corona Authors: Fleck, B.; Noci, G.; Poletto, G. Bibcode: 1994msfs.conf.....F Altcode: No abstract at ADS Title: Line profile asymmetries in a sunspot penumbra Authors: Hofmann, J.; Deubner, F. -L.; Fleck, B. Bibcode: 1994smf..conf..182H Altcode: No abstract at ADS Title: Investigations on Laser Induced Dynamic Gratings in Azo-Dye Doped Polymer Layers and Their Application Authors: Fleck, B.; Rehn, H.; Friedrich, V.; Wenke, L.; Janietz, D. Bibcode: 1994ESOC...48..413F Altcode: 1994aao..conf..413F No abstract at ADS Title: Experimental Investigations on Two-Wave Mixing in Photorefractive Crystals with Spherical Waves Authors: Kiessling, A.; Fleck, B.; Wenke, L. Bibcode: 1994ESOC...48..419K Altcode: 1994aao..conf..419K No abstract at ADS Title: SOHO - The Solar and Heliospheric Observatory Authors: Fleck, B.; Domingo, V. Bibcode: 1994smf..conf..408F Altcode: No abstract at ADS Title: SOHO: science objectives and capabilities Authors: Fleck, B.; Domingo, V.; Poland, A. I. Bibcode: 1994ASIC..433..517F Altcode: No abstract at ADS Title: Phases and amplitudes of acoustic-gravity waves. 2: The effects of reflection Authors: Marmolino, C.; Severino, G.; Deubner, F. -L.; Fleck, B. Bibcode: 1993A&A...278..617M Altcode: We study wave reflection caused by the temperature stratification of the solar atmosphere, assumed to be a succession of two layers of different temperatures and radiative decay times. Considering waves which propagate energy upward in the atmosphere, we compute the complex amplitude reflection and transmission coefficients and investigate the effects that reflection introduces on the phases of acoustic-gravity waves. In the evanescent region of the kx - omega diagram, between the Lamb waves and the acoustic cut-off frequency, the reflection coefficient is small, in particular zero on the fundamental mode. Therefore, in this region, the reflected wave has a small amplitude and its superposition to the incident wave does not affect the latter in a significant way. In particular, the T - V phase differences of the total wave are very similar to those of the incident wave. Furthermore, a heruisitic formula is presented which describes the observed coexistence of two different phase regimes between velocity and intensity oscillations in the evanescent area above the fundamental mode. Title: On the numerical calculation of hydrodynamic shock waves in atmospheres by an FCT method Authors: Schmitz, F.; Fleck, B. Bibcode: 1993A&A...279..499S Altcode: The numerical calculation of vertically propagating hydrodynamic shock waves in a plane atmosphere by the ETBFCT-version of the Flux Corrected Transport (FCT) method by Boris and Book is discussed. The results are compared with results obtained by a characteristic method with shock fitting. We show that the use of the internal energy density as a dependent variable instead of the total energy density can give very inaccurate results. Consequent discretization rules for the gravitational source terms are derived. The improvement of the results by an additional iteration step is discussed. It appears that the FCT method is an excellent method for the accurate calculation of shock waves in an atmosphere. Title: On the interactions of hydrodynamic shock waves in stellar atmospheres Authors: Fleck, B.; Schmitz, F. Bibcode: 1993A&A...273..671F Altcode: We study the effects of non-linear interactions of hydrodynamic shock waves in the solar atmosphere and their influence on the resonant oscillations at the cut-off frequency The shock waves originate from randomly generated wave packets with broad frequency distributions as opposed to previous studies which start with monochromatic wave trains, single pulses or, at the most, regular waves trains with stochastically changing periods. We consider only one-dimensional (vertical) adiabatic or isothermal hydrodynamics using a numerical code based on a modified flux corrected transport algorithm. The results are analyzed by applying Fourier methods, i.e. power and phase difference spectra. The dynamical behaviour of an atmosphere excited by a broad spectrum.of acoustic waves differs extremely from that disturbed by monochromatic waves. Due to shock overtaking processes almost all the high frequency shock waves merge and form strong long period shock waves. Comparing the results of three different frequency spectra it is shown that the detailed form of the excitation spectrum is only of minor importance. The results show that shock overtaking does not generate the characteristic cut-off frequency oscillations. We observe these particular oscillations only when we add a long period evanescent component with ω≤ωac to the acoustic spectrum at the base of the atmosphere. Consequences for the shock heating of the solar chromosphere are briefly discussed. Title: Invited Talk: (SOHO Operations and Coordination with Ground-based Observatories) Authors: Domingo, V.; Fleck, B. Bibcode: 1993BAAS...25.1195D Altcode: No abstract at ADS Title: Polanmetric Measurements of the Fine Structure of a Sunspot Penumbra Authors: Hofmann, J.; Deubner, F. L.; Fleck, B. Bibcode: 1993ASPC...46...44H Altcode: 1993mvfs.conf...44H; 1993IAUCo.141...44H No abstract at ADS Title: Observations of Waves and Oscillations in the Solar Magnetic Fine Structure Authors: Fleck, B.; Deubner, F. -L.; Schmidt, W. Bibcode: 1993ASPC...46..522F Altcode: 1993IAUCo.141..522F; 1993mvfs.conf..522F No abstract at ADS Title: Dynamics of the solar atmosphere. V - Partial reflection and forced oscillation, and their signature in phase diagrams Authors: Deubner, F. -L.; Fleck, B.; Schmitz, F.; Straus, Th. Bibcode: 1992A&A...266..560D Altcode: An overview of several new dynamic phenomena detected by means of velocity-brightness (V-I) and V-V phase diagrams is presented. The great diagnostic value of this kind of data analysis is demonstrated and used in order to develop a consistent description and interpretation of the surprisingly broad spectrum of linear hydrodynamic wave motions that occur in a stellar atmosphere. The significance of partial reflection and the role of forced oscillations in practically all layers of the solar atmosphere are demonstrated. With reference to the concept of continuous partial reflection, a model of the 'background' of coherent wave motions found at frequencies and wavenumbers in between the well-known p-mode ridges is presented. Title: On the reflection of linear hydrodynamic waves at continuous temperature steps in stellar atmospheres Authors: Schmitz, F.; Fleck, B. Bibcode: 1992A&A...260..447S Altcode: A simple analytical expression which describes a smooth temperature step is used to study the behavior of vertically propagating adiabatic waves in non-isothermal plane atmospheric layers. With this expression the one-dimensional equation of adiabatic linear atmospheric waves is reduced to a hypergeometric differential equation. From the asymptotic evaluations of the solutions we obtain formulas for reflection coefficients and phases. In the case of acoustic waves the reflection coefficients can be given in terms of simple functions. It is shown how the photospheric temperature decrease and the chromospheric temperature increase of the solar atmosphere can be approximated by the temperature formula. For these approximations various results are presented for both evanescent and acoustic waves. The results of the reflection at continuous steps are compared with those at a temperature discontinuity. The WKB-approximation of the velocity of a wave passing a continuous temperature step is given. A limiting form of the temperature function is used to study the behavior of evanescent waves in a photosphere. Title: Is mesogranulation a distinct regime of convection? Authors: Straus, Th.; Deubner, F. -L.; Fleck, B. Bibcode: 1992A&A...256..652S Altcode: We investigate the dynamics of the mesogranulation phenomenon by analyzing spatially 2D spectral time series taken at disk center and cos Theta = 0.8. After a 3D Fourier transformation, we integrate the power and crosspower spectra in azimuth, and calculate k - omega power, phase difference, and cross-power spectra. The spatial power spectra are compared with those obtained from numerical simulations of stationary cell patterns. In the deepest atmospheric layers the V - I phase difference spectra reveal a uniform regime of convective motions at frequencies below the Lamb mode. The power spectra exhibit at all levels a significant distinction between supergranulation and convective patterns of smaller scales. On the other hand, the 'mesogranulation' phenomenon cannot be identified as an independent convective regime in the deep photosphere, distinct from granulation. Rather, the mesostructures that appear to emerge in the middle photosphere and temperature minimum seem to be a product of the overshoot driving only the largest elements of an extended distribution of granular sizes while the smaller elements have already died out at a lower level. Title: Polarimetric measurements of the fine structure of a sunspot penumbra. Authors: Hofmann, J.; Deubner, F. -L.; Fleck, B.; Schmidt, W. Bibcode: 1992AGAb....7..149H Altcode: No abstract at ADS Title: An analysis of non-linear oscillations in the solar chromosphere. Authors: Kossack, E.; Deubner, F. -L.; Fleck, B. Bibcode: 1992AGAb....7..148K Altcode: No abstract at ADS Title: The 3-min oscillations of the solar chromosphere - A basic physical effect? Authors: Fleck, B.; Schmitz, F. Bibcode: 1991A&A...250..235F Altcode: The resonant excitation of the acoustic cut-off frequency mode in a stratified atmosphere, an affect which provides a simple explanation of the observed 3-min oscillations of the solar chromosphere, is discussed. It is demonstrated that the cut-off frequency mode is excited also by long period disturbances, which, in the case of the sun, could be the wave trains of the photospheric 5-min oscillations. Due to the spatial attenuation of the evanescent waves, the oscillations at the cut-off frequency dominate the oscillatory signal above a certain height (about 6 to 8 scale heights above the moving piston). The oscillations at the cut-off frequency are very persistent and vanish for t approaches infinity only in an infinitely extended atmosphere without any reflecting boundaries. In a finite atmosphere with an upper boundary at which total or partial reflection occurs, the Omega = 1 oscillations are permanently excited. It is concluded that there is no need for a chromospheric cavity to explain the observed chromospheric 3-min resonance, as was previously assumed. Title: Observations of Waves and Oscillations in Solar Magnetic Fluxtube Concentrations (With 1 Figure) Authors: Fleck, B.; Deubner, F. -L. Bibcode: 1991mcch.conf...19F Altcode: No abstract at ADS