Author name code: vandriel-gesztelyi ADS astronomy entries on 2022-09-14 author:"van Driel-Gesztelyi, Lidia" OR author:"Gesztelyi, Lidia" ------------------------------------------------------------------------ Title: Stellar FIP effect from the empirical side Authors: Seli, Bálint; Van Driel-Gesztelyi, Lidia; Baker, Deborah; Laming, J. Martin; Kovari, Zsolt; Oláh, Katalin; Kriskovics, Levente; Vida, Krisztián; Balázs, Lajos Bibcode: 2022cosp...44.2585S Altcode: The difference between the elemental abundances of the corona and the photosphere is an apparently common feature of stellar atmospheres. The abundance difference depends on the first ionization potential of the given element, so the phenomenon is known as the FIP effect. Here we explore the variation of the strength of the FIP effect for different types of stars, through the FIP bias parameter. Using a sample of 59 main sequence and evolved stars with known coronal abundances from the literature, we look for macroscopic, measurable parameters that affect the stellar FIP bias, and also re-evaluate the simple dependence on the effective temperature. Title: Investigating of the nature of magnetic oscillations associated with FIP effect Authors: Murabito, Mariarita; Jafarzadeh, Shahin; Van Driel-Gesztelyi, Lidia; Ermolli, Ilaria; Baker, Deborah; Brooks, David; Long, David; Jess, David; Valori, Gherardo; Stangalini, Marco Bibcode: 2022cosp...44.2591M Altcode: Observations of the photosphere, chromosphere, and corona combined with magnetic field modeling of one of the biggest sunspots of the 24 solar cycle, revealed that regions of high FIP bias plasma in the corona were magnetically linked to the locations of the intrinsic magnetic oscillations in the solar chromosphere. In order to characterize the driver of the oscillations, we analyzed the relation between the spatial distribution of the magnetic wave power and the overall field geometry and plasma parameters obtained from the multi-height spectropolarimetric non-local thermodynamic equilibrium (NLTE) inversions. In correspondence with the locations where the magnetic wave energy is observed at chromospheric heights, we found evidence in support of locally excited acoustic waves that, after crossing the equipartition layer located close to the umbra-penumbra boundary at photospheric heights, are converted into magnetic-like waves. These results indicate a direct connection between sunspot chromospheric activity and observable changes in coronal plasma composition, demonstrating the power of high resolution, multi-height studies of the solar atmosphere that will become the gold standard in the era of DKIST. Title: Understanding the Correlation between Solar Coronal Abundances and F10.7 Radio Emission Authors: To, Andy S. H.; Baker, Deborah; Long, David; James, Alexander; Brooks, David; van Driel-Gesztelyi, Lidia; Valori, Gherardo; Bastian, Tim; Lomuscio, Samantha; Stansby, David Bibcode: 2022cosp...44.2592T Altcode: Solar corona plasma composition, derived from full-Sun spectra, and the F10.7 radio flux (2.8 GHz) have been shown to be highly correlated (r = 0.88) during the recent weak solar cycle. However, this correlation becomes nonlinear at times of increased solar magnetic activity. We used co-temporal, high spatial resolution, radio (JVLA), and EUV (Hinode/EIS) images of the Sun taken on the 3 and 7 April 2020 to understand the underlying causes of the non-linearity of the FIP bias-F10.7 solar index correlation. We then calculated differential emission measures from AIA images, and paired them with the observed FIP bias to predict the bremsstrahlung component of F10.7 radio emission. Results of this study provide constraints on the amplitude of composition variability related to solar cycle amplitude, and provide an alternative method to calculate coronal composition. Title: What determines active region coronal plasma composition? Authors: Mihailescu, Teodora; Baker, Deborah; Long, David; Green, Lucie; Brooks, David; van Driel-Gesztelyi, Lidia; To, Andy S. H. Bibcode: 2022cosp...44.2580M Altcode: The chemical composition of the solar corona is different from that of the solar photosphere, with the strongest variation being observed in active regions. Using spectral data from the Extreme Ultraviolet (EUV) Imaging Spectrometer (EIS) on Hinode, we present a survey of coronal elemental composition as expressed in the FIP bias in 28 active regions with a wide range of ages and magnetic flux contents, and at different stages in their evolution. We find no correlation between the FIP bias of an active region and its magnetic flux or age. However, there is a dependence of the FIP bias on the evolutionary stage of the active region. FIP bias shows an increasing trend with average magnetic flux density up to 200 G but this trend does not continue at higher values. In contrast to the single values typically used to characterize the FIP bias in a region, we find that the FIP bias distribution within active regions has a significant spread. The highest spread is observed in very dispersed active regions and active regions that have formed a filament channel along their main polarity inversion lines, which is an indicator of the wide range of physical processes that take place in these active regions. These findings indicate that, while some general trends can be observed, the processes influencing the composition of an active region are complex and specific to its evolution, history and magnetic configuration or environment. The spread of FIP bias values in active regions shows a broad match with that previously observed in situ in the slow solar wind. Title: What have we learned about I-FIP Effect on the Sun from Hinode/EIS? Authors: Baker, Deborah; van Driel-Gesztelyi, Lidia Bibcode: 2022cosp...44.2572B Altcode: Plasma composition in stellar coronae can differ from that of their photospheres, the cause of which is one of the open questions in astrophysics. Elements with a low first ionization potential (FIP) are observed to have either enhanced or depleted abundances relative to that of high FIP elements. The abundance pattern is known as the FIP effect or inverse FIP (I-FIP) effect, depending on whether the low FIP elements are over-/under- (FIP/I-FIP) abundant in coronae. Some stellar coronae are dominated by FIP effect plasma but cooler, more active stars are dominated by I-FIP effect plasma. Our local laboratory, the Sun, has a FIP effect dominated corona, however, short-lived I-FIP patches have occasionally been observed. Analysis of multiple cases of I-FIP effect revealed certain conditions in the magnetic field and flare heating to be necessary for the occurrence of I-FIP effect plasma on the Sun. An overview of what we have learned from sixteen years of spatially resolved spectroscopic observations from Hinode/EIS will be presented. We will demonstrate the power of combining spectroscopic, imaging, and magnetic field observations of our Sun to understand the physical processes on cooler stars which we only observe as point sources. Title: Evolution of Plasma Composition in an Eruptive Flux Rope Authors: Baker, Deborah; Demoulin, Pascal; Long, David; Janvier, Miho; Green, Lucie; Brooks, David; van Driel-Gesztelyi, Lidia; Mihailescu, Teodora; To, Andy S. H.; Yardley, Stephanie; Valori, Gherardo Bibcode: 2022cosp...44.1361B Altcode: Magnetic flux ropes are bundles of twisted magnetic field enveloping a central axis. They harbor free magnetic energy and can be progenitors of coronal mass ejections (CMEs). However, identifying flux ropes on the Sun can be challenging. One of the key coronal observables that has been shown to indicate the presence of a flux rope is a peculiar bright coronal structure called a sigmoid. In this work, we show Hinode EUV Imaging Spectrometer observations of sigmoidal active region (AR) 10977. We analyze the coronal plasma composition in the AR and its evolution as a sigmoid (flux rope) forms and erupts as a CME. Plasma with photospheric composition was observed in coronal loops close to the main polarity inversion line during episodes of significant flux cancellation, suggestive of the injection of photospheric plasma into these loops driven by photospheric flux cancellation. Concurrently, the increasingly sheared core field contained plasma with coronal composition. As flux cancellation decreased and a sigmoid/flux rope formed, the plasma evolved to an intermediate composition in between photospheric and typical AR coronal compositions. Finally, the flux rope contained predominantly photospheric plasma during and after a failed eruption preceding the CME. Hence, plasma composition observations of AR 10977 strongly support models of flux rope formation by photospheric flux cancellation forcing magnetic reconnection first at the photospheric level then at the coronal level. Title: What Determines Active Region Coronal Plasma Composition? Authors: Mihailescu, Teodora; Baker, Deborah; Green, Lucie M.; van Driel-Gesztelyi, Lidia; Long, David M.; Brooks, David H.; To, Andy S. H. Bibcode: 2022ApJ...933..245M Altcode: 2022arXiv220505027M The chemical composition of the solar corona is different from that of the solar photosphere, with the strongest variation being observed in active regions (ARs). Using data from the Extreme Ultraviolet (EUV) Imaging Spectrometer (EIS) on Hinode, we present a survey of coronal elemental composition as expressed in the first ionization potential (FIP) bias in 28 ARs of different ages and magnetic flux content, which are at different stages in their evolution. We find no correlation between the FIP bias of an AR and its total unsigned magnetic flux or age. However, there is a weak dependence of FIP bias on the evolutionary stage, decreasing from 1.9 to 2.2 in ARs with spots to 1.5-1.6 in ARs that are at more advanced stages of the decay phase. FIP bias shows an increasing trend with average magnetic flux density up to 200 G, but this trend does not continue at higher values. The FIP bias distribution within ARs has a spread between 0.4 and 1. The largest spread is observed in very dispersed ARs. We attribute this to a range of physical processes taking place in these ARs, including processes associated with filament channel formation. These findings indicate that, while some general trends can be observed, the processes influencing the composition of an AR are complex and specific to its evolution, magnetic configuration, or environment. The spread of FIP bias values in ARs shows a broad match with that previously observed in situ in the slow solar wind. Title: Detection of Stellar-like Abundance Anomalies in the Slow Solar Wind Authors: Brooks, David H.; Baker, Deborah; van Driel-Gesztelyi, Lidia; Warren, Harry P.; Yardley, Stephanie L. Bibcode: 2022ApJ...930L..10B Altcode: 2022arXiv220409332B The elemental composition of the Sun's hot atmosphere, the corona, shows a distinctive pattern that is different from the underlying surface or photosphere. Elements that are easy to ionize in the chromosphere are enhanced in abundance in the corona compared to their photospheric values. A similar pattern of behavior is often observed in the slow-speed (<500 km s-1) solar wind and in solar-like stellar coronae, while a reversed effect is seen in M dwarfs. Studies of the inverse effect have been hampered in the past because only unresolved (point-source) spectroscopic data were available for these stellar targets. Here we report the discovery of several inverse events observed in situ in the slow solar wind using particle-counting techniques. These very rare events all occur during periods of high solar activity that mimic conditions more widespread on M dwarfs. The detections allow a new way of connecting the slow wind to its solar source and are broadly consistent with theoretical models of abundance variations due to chromospheric fast-mode waves with amplitudes of 8-10 km s-1, sufficient to accelerate the solar wind. The results imply that M-dwarf winds are dominated by plasma depleted in easily ionized elements and lend credence to previous spectroscopic measurements. Title: Extending the FIP bias sample to magnetically active stars. Challenging the FIP bias paradigm Authors: Seli, B.; Oláh, K.; Kriskovics, L.; Kővári, Zs.; Vida, K.; Balázs, L. G.; Laming, J. M.; van Driel-Gesztelyi, L.; Baker, D. Bibcode: 2022A&A...659A...3S Altcode: 2021arXiv211114735S Context. The different elemental abundances of the photosphere and the corona are striking features of not only the Sun, but of other stars as well. This phenomenon is known as the first ionisation potential (FIP) effect, and its strength can be characterized by the FIP bias, the logarithmic abundance difference between low- and high-FIP elements in the corona, compared to the photosphere. The FIP bias was shown to depend on the surface temperature of the star.
Aims: We aim to extend the Teff−FIP bias relationship to a larger stellar sample and analyse the effect of other astrophysical parameters on the relation (e.g. surface gravity, age, activity indicators).
Methods: We compiled FIP bias and other parameters for 59 stars for which coronal composition is available, now including evolved stars. Using principal component analysis and linear discriminant analysis, we searched for correlations with other astrophysical parameters within the sample that may influence the stellar FIP bias.
Results: Adding stars to the Teff−FIP bias diagram unveiled new features in its structure. In addition to the previously known relationship, there appears to be a second branch: a parallel sequence about 0.5 dex above it. While the Teff remains the main determinant of the FIP bias, other parameters such as stellar activity indicators also have influence. We find three clusters in the FIP bias determinant parameter space. One distinct group is formed by the evolved stars. Two groups contain main sequence stars in continuation separated roughly by the sign change of the FIP-bias value.
Conclusions: The new branch of the Teff−FIP bias diagram contains stars with higher activity level, in terms of X-ray flux and rotational velocity. The Rossby number also seems to be important, indicating possible dependence on the type of dynamo operating in these stars influencing their FIP bias. The two main-sequence clusters run from the earliest spectral types of A-F with shallow convection zones through G-K-early-M stars with gradually deeper convection zones, and they end with the fully convective M dwarf stars, depicting the change of the dynamo type with the internal differences of the main sequence stars in connection with the FIP-bias values. Title: Evolution of Plasma Composition in an Eruptive Flux Rope Authors: Baker, D.; Green, L. M.; Brooks, D. H.; Démoulin, P.; van Driel-Gesztelyi, L.; Mihailescu, T.; To, A. S. H.; Long, D. M.; Yardley, S. L.; Janvier, M.; Valori, G. Bibcode: 2022ApJ...924...17B Altcode: 2021arXiv211011714B Magnetic flux ropes are bundles of twisted magnetic field enveloping a central axis. They harbor free magnetic energy and can be progenitors of coronal mass ejections (CMEs). However, identifying flux ropes on the Sun can be challenging. One of the key coronal observables that has been shown to indicate the presence of a flux rope is a peculiar bright coronal structure called a sigmoid. In this work, we show Hinode EUV Imaging Spectrometer observations of sigmoidal active region (AR) 10977. We analyze the coronal plasma composition in the AR and its evolution as a sigmoid (flux rope) forms and erupts as a CME. Plasma with photospheric composition was observed in coronal loops close to the main polarity inversion line during episodes of significant flux cancellation, suggestive of the injection of photospheric plasma into these loops driven by photospheric flux cancellation. Concurrently, the increasingly sheared core field contained plasma with coronal composition. As flux cancellation decreased and a sigmoid/flux rope formed, the plasma evolved to an intermediate composition in between photospheric and typical AR coronal compositions. Finally, the flux rope contained predominantly photospheric plasma during and after a failed eruption preceding the CME. Hence, plasma composition observations of AR 10977 strongly support models of flux rope formation by photospheric flux cancellation forcing magnetic reconnection first at the photospheric level then at the coronal level. Title: Editorial Appreciation Authors: Arregui, Iñigo; Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2022SoPh..297...11A Altcode: No abstract at ADS Title: Investigating the origin of magnetic perturbations associated with the FIP Effect Authors: Murabito, M.; Stangalini, M.; Baker, D.; Valori, G.; Jess, D. B.; Jafarzadeh, S.; Brooks, D. H.; Ermolli, I.; Giorgi, F.; Grant, S. D. T.; Long, D. M.; van Driel-Gesztelyi, L. Bibcode: 2021A&A...656A..87M Altcode: 2021arXiv210811164M Recently, magnetic oscillations were detected in the chromosphere of a large sunspot and found to be linked to the coronal locations where a first ionization potential (FIP) effect was observed. In an attempt to shed light on the possible excitation mechanisms of these localized waves, we further investigate the same data by focusing on the relation between the spatial distribution of the magnetic wave power and the overall field geometry and plasma parameters obtained from multi-height spectropolarimetric non-local thermodynamic equilibrium (NLTE) inversions of IBIS data. We find, in correspondence with the locations where the magnetic wave energy is observed at chromospheric heights, that the magnetic fields have smaller scale heights, meaning faster expansions of the field lines, which ultimately results in stronger vertical density stratification and wave steepening. In addition, the acoustic spectrum of the oscillations at the locations where magnetic perturbations are observed is broader than that observed at other locations, which suggests an additional forcing driver to the p-modes. Analysis of the photospheric oscillations in the sunspot surroundings also reveals a broader spectrum between the two opposite polarities of the active region (the leading spot and the trailing opposite polarity plage), and on the same side where magnetic perturbations are observed in the umbra. We suggest that strong photospheric perturbations between the two polarities are responsible for this broader spectrum of oscillations, with respect to the p-mode spectrum, resulting in locally excited acoustic waves that, after crossing the equipartition layer, located close to the umbra-penumbra boundary at photopheric heights, are converted into magnetic waves and steepen due to the strong density gradient.

Movie associated to Fig. 1 is available at https://www.aanda.org Title: Global Contributions of Active Regions to the Solar Wind Authors: Stansby, David; Green, Lucie; van Driel-Gesztelyi, Lidia; Horbury, Timothy Bibcode: 2021AGUFMSH24C..04S Altcode: Both coronal holes and active regions are source regions of the solar wind. The distribution of these coronal structures across both space and time within the corona is well known, and is driven by photospheric magnetic flux evolution across the 11-year solar cycle. In turn these coronal structures drive variability in the solar wind throughout the heliosphere. To understand how important active regions are as solar wind sources, we have used photospheric magnetic field maps from the past four solar cycles to estimate what fraction of magnetic open solar flux is rooted in active regions, a proxy for the fraction of all solar wind originating in active regions. We found that the fractional contribution of active regions to the solar wind varies between 30% to 80% at any one time during solar maximum and is negligible at solar minimum, showing a strong correlation with sunspot number. While active regions are typically confined to latitudes ±30 in the corona, the solar wind they produce can reach latitudes up to ±60. These results quantify the importance of active regions in globally influencing the whole heliosphere, providing motivation for further studies of active regions as solar wind sources during Solar Cycle 25. Title: Active Region Contributions to the Solar Wind over Multiple Solar Cycles Authors: Stansby, David; Green, Lucie M.; van Driel-Gesztelyi, Lidia; Horbury, Timothy S. Bibcode: 2021SoPh..296..116S Altcode: 2021arXiv210404417S Both coronal holes and active regions are source regions of the solar wind. The distribution of these coronal structures across both space and time is well known, but it is unclear how much each source contributes to the solar wind. In this study we use photospheric magnetic field maps observed over the past four solar cycles to estimate what fraction of magnetic open solar flux is rooted in active regions, a proxy for the fraction of all solar wind originating in active regions. We find that the fractional contribution of active regions to the solar wind varies between 30% to 80% at any one time during solar maximum and is negligible at solar minimum, showing a strong correlation with sunspot number. While active regions are typically confined to latitudes ±30∘ in the corona, the solar wind they produce can reach latitudes up to ±60∘. Their fractional contribution to the solar wind also correlates with coronal mass ejection rate, and is highly variable, changing by ±20% on monthly timescales within individual solar maxima. We speculate that these variations could be driven by coronal mass ejections causing reconfigurations of the coronal magnetic field on sub-monthly timescales. Title: Graphical evidence for the solar coronal structure during the Maunder minimum: comparative study of the total eclipse drawings in 1706 and 1715 Authors: Hayakawa, Hisashi; Lockwood, Mike; Owens, Matthew J.; Sôma, Mitsuru; Besser, Bruno P.; van Driel-Gesztelyi, Lidia Bibcode: 2021JSWSC..11....1H Altcode: We discuss the significant implications of three eye-witness drawings of the total solar eclipse on 1706 May 12 in comparison with two on 1715 May 3, for our understanding of space climate change. These events took place just after what has been termed the "deep Maunder Minimum" but fall within the "extended Maunder Minimum" being in an interval when the sunspot numbers start to recover. Maria Clara Eimmert's image in 1706 is particularly important because she was both a highly accomplished astronomical observer and an excellent artist: it was thought lost and was only re-discovered in 2012. Being the earliest coronal drawings of observational value yet identified, these drawings corroborate verbal accounts a corona without significant streamers, seen at totality of this and another eclipse event in 1652 during the Maunder Minimum. The graphical evidence implies that the coronal solar magnetic field was not lost but significantly weakened and the lack of coronal structure means there was little discernable open flux (either polar or at lower latitudes) even during the recovery phase of the Maunder Minimum. These observations provide evidence for a different state of oscillation of the solar dynamo, and hence behaviour of the Sun, in comparison with that during normal solar cycle minima (when a streamer belt between two polar coronal holes is visible) or near normal sunspot maxima (when coronal structure is caused by coronal holes at all latitudes) even to observers without a telescope. Title: Plasma Upflows Induced by Magnetic Reconnection Above an Eruptive Flux Rope Authors: Baker, Deborah; Mihailescu, Teodora; Démoulin, Pascal; Green, Lucie M.; van Driel-Gesztelyi, Lidia; Valori, Gherardo; Brooks, David H.; Long, David M.; Janvier, Miho Bibcode: 2021SoPh..296..103B Altcode: 2021arXiv210616137B One of the major discoveries of Hinode's Extreme-ultraviolet Imaging Spectrometer (EIS) is the presence of upflows at the edges of active regions. As active regions are magnetically connected to the large-scale field of the corona, these upflows are a likely contributor to the global mass cycle in the corona. Here we examine the driving mechanism(s) of the very strong upflows with velocities in excess of 70 km s−1, known as blue-wing asymmetries, observed during the eruption of a flux rope in AR 10977 (eruptive flare SOL2007-12-07T04:50). We use Hinode/EIS spectroscopic observations combined with magnetic-field modeling to investigate the possible link between the magnetic topology of the active region and the strong upflows. A Potential Field Source Surface (PFSS) extrapolation of the large-scale field shows a quadrupolar configuration with a separator lying above the flux rope. Field lines formed by induced reconnection along the separator before and during the flux-rope eruption are spatially linked to the strongest blue-wing asymmetries in the upflow regions. The flows are driven by the pressure gradient created when the dense and hot arcade loops of the active region reconnect with the extended and tenuous loops overlying it. In view of the fact that separator reconnection is a specific form of the more general quasi-separatrix (QSL) reconnection, we conclude that the mechanism driving the strongest upflows is, in fact, the same as the one driving the persistent upflows of ≈10 - 20 km s−1 observed in all active regions. Title: The Evolution of Plasma Composition during a Solar Flare Authors: To, Andy S. H.; Long, David M.; Baker, Deborah; Brooks, David H.; van Driel-Gesztelyi, Lidia; Laming, J. Martin; Valori, Gherardo Bibcode: 2021ApJ...911...86T Altcode: 2021arXiv210209985T We analyze the coronal elemental abundances during a small flare using Hinode/EIS observations. Compared to the preflare elemental abundances, we observed a strong increase in coronal abundance of Ca XIV 193.84 Å, an emission line with low first ionization potential (FIP < 10 eV), as quantified by the ratio Ca/Ar during the flare. This is in contrast to the unchanged abundance ratio observed using Si X 258.38 Å/S X 264.23 Å. We propose two different mechanisms to explain the different composition results. First, the small flare-induced heating could have ionized S, but not the noble gas Ar, so that the flare-driven Alfvén waves brought up Si, S, and Ca in tandem via the ponderomotive force which acts on ions. Second, the location of the flare in strong magnetic fields between two sunspots may suggest fractionation occurred in the low chromosphere, where the background gas is neutral H. In this region, high-FIP S could behave more like a low-FIP than a high-FIP element. The physical interpretations proposed generate new insights into the evolution of plasma abundances in the solar atmosphere during flaring, and suggests that current models must be updated to reflect dynamic rather than just static scenarios. Title: Editorial Appreciation Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2021SoPh..296...14L Altcode: No abstract at ADS Title: Alfvénic Perturbations in a Sunspot Chromosphere Linked to Fractionated Plasma in the Corona Authors: Baker, Deborah; Stangalini, Marco; Valori, Gherardo; Brooks, David H.; To, Andy S. H.; van Driel-Gesztelyi, Lidia; Démoulin, Pascal; Stansby, David; Jess, David B.; Jafarzadeh, Shahin Bibcode: 2021ApJ...907...16B Altcode: 2020arXiv201204308B In this study, we investigate the spatial distribution of highly varying plasma composition around one of the largest sunspots of solar cycle 24. Observations of the photosphere, chromosphere, and corona are brought together with magnetic field modeling of the sunspot in order to probe the conditions that regulate the degree of plasma fractionation within loop populations of differing connectivities. We find that, in the coronal magnetic field above the sunspot umbra, the plasma has photospheric composition. Coronal loops rooted in the penumbra contain fractionated plasma, with the highest levels observed in the loops that connect within the active region. Tracing field lines from regions of fractionated plasma in the corona to locations of Alfvénic fluctuations detected in the chromosphere shows that they are magnetically linked. These results indicate a connection between sunspot chromospheric activity and observable changes in coronal plasma composition. Title: Spectropolarimetric Insight into Plasma Sheet Dynamics of a Solar Flare Authors: French, R.; Judge, P. G.; Matthews, S.; van Driel-Gesztelyi, L.; Long, D. Bibcode: 2020AGUFMSH045..03F Altcode: Magnetic reconnection is thought to lie at the heart of energy release in solar flares, but the process is not yet fully understood. We examine spectropolarimetric data from the CoMP coronagraph, acquired a few hours into the evolution of the September 10th 2017 X8.2-class flare. We find a striking and spatially coherent low polarisation structure, aligned with the hot plasma sheet observed in EUV. By elimination, we find the significant depolarisation to be a result of small-scale sub-pixel magnetic structure along the plasma sheet, consistent with theory of reconnection instabilities. This interpretation of ongoing reconnection is supported by further Hinode/EIS observations and AIA DEMs, from well beyond the impulsive phase of the flare. The plasma sheet remains visible in CoMP linear polarisation over a day into the flare's evolution, several hours after its last appearance in EUV. We conclude that polarisation measurements with new coronagraphs, such the DKIST CRYO-NIRSP instrument, will further enhance our understanding of magnetic reconnection during eruptive flares. Title: A new trigger mechanism for coronal mass ejections. The role of confined flares and photospheric motions in the formation of hot flux ropes Authors: James, A. W.; Green, L. M.; van Driel-Gesztelyi, L.; Valori, G. Bibcode: 2020A&A...644A.137J Altcode: 2020arXiv201011204J Context. Many previous studies have shown that the magnetic precursor of a coronal mass ejection (CME) takes the form of a magnetic flux rope, and a subset of them have become known as "hot flux ropes" due to their emission signatures in ∼10 MK plasma.
Aims: We seek to identify the processes by which these hot flux ropes form, with a view of developing our understanding of CMEs and thereby improving space weather forecasts.
Methods: Extreme-ultraviolet observations were used to identify five pre-eruptive hot flux ropes in the solar corona and study how they evolved. Confined flares were observed in the hours and days before each flux rope erupted, and these were used as indicators of episodic bursts of magnetic reconnection by which each flux rope formed. The evolution of the photospheric magnetic field was observed during each formation period to identify the process(es) that enabled magnetic reconnection to occur in the β < 1 corona and form the flux ropes.
Results: The confined flares were found to be homologous events and suggest flux rope formation times that range from 18 hours to 5 days. Throughout these periods, fragments of photospheric magnetic flux were observed to orbit around each other in sunspots where the flux ropes had a footpoint. Active regions with right-handed (left-handed) twisted magnetic flux exhibited clockwise (anticlockwise) orbiting motions, and right-handed (left-handed) flux ropes formed.
Conclusions: We infer that the orbital motions of photospheric magnetic flux fragments about each other bring magnetic flux tubes together in the corona, enabling component reconnection that forms a magnetic flux rope above a flaring arcade. This represents a novel trigger mechanism for solar eruptions and should be considered when predicting solar magnetic activity.

Movies associated to Figs. 4, 8, 12, and 14 are available at https://www.aanda.org 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: The Solar Orbiter EUI instrument: The Extreme Ultraviolet Imager Authors: Rochus, P.; Auchère, F.; Berghmans, D.; Harra, L.; Schmutz, W.; Schühle, U.; Addison, P.; Appourchaux, T.; Aznar Cuadrado, R.; Baker, D.; Barbay, J.; Bates, D.; BenMoussa, A.; Bergmann, M.; Beurthe, C.; Borgo, B.; Bonte, K.; Bouzit, M.; Bradley, L.; Büchel, V.; Buchlin, E.; Büchner, J.; Cabé, F.; Cadiergues, L.; Chaigneau, M.; Chares, B.; Choque Cortez, C.; Coker, P.; Condamin, M.; Coumar, S.; Curdt, W.; Cutler, J.; Davies, D.; Davison, G.; Defise, J. -M.; Del Zanna, G.; Delmotte, F.; Delouille, V.; Dolla, L.; Dumesnil, C.; Dürig, F.; Enge, R.; François, S.; Fourmond, J. -J.; Gillis, J. -M.; Giordanengo, B.; Gissot, S.; Green, L. M.; Guerreiro, N.; Guilbaud, A.; Gyo, M.; Haberreiter, M.; Hafiz, A.; Hailey, M.; Halain, J. -P.; Hansotte, J.; Hecquet, C.; Heerlein, K.; Hellin, M. -L.; Hemsley, S.; Hermans, A.; Hervier, V.; Hochedez, J. -F.; Houbrechts, Y.; Ihsan, K.; Jacques, L.; Jérôme, A.; Jones, J.; Kahle, M.; Kennedy, T.; Klaproth, M.; Kolleck, M.; Koller, S.; Kotsialos, E.; Kraaikamp, E.; Langer, P.; Lawrenson, A.; Le Clech', J. -C.; Lenaerts, C.; Liebecq, S.; Linder, D.; Long, D. M.; Mampaey, B.; Markiewicz-Innes, D.; Marquet, B.; Marsch, E.; Matthews, S.; Mazy, E.; Mazzoli, A.; Meining, S.; Meltchakov, E.; Mercier, R.; Meyer, S.; Monecke, M.; Monfort, F.; Morinaud, G.; Moron, F.; Mountney, L.; Müller, R.; Nicula, B.; Parenti, S.; Peter, H.; Pfiffner, D.; Philippon, A.; Phillips, I.; Plesseria, J. -Y.; Pylyser, E.; Rabecki, F.; Ravet-Krill, M. -F.; Rebellato, J.; Renotte, E.; Rodriguez, L.; Roose, S.; Rosin, J.; Rossi, L.; Roth, P.; Rouesnel, F.; Roulliay, M.; Rousseau, A.; Ruane, K.; Scanlan, J.; Schlatter, P.; Seaton, D. B.; Silliman, K.; Smit, S.; Smith, P. J.; Solanki, S. K.; Spescha, M.; Spencer, A.; Stegen, K.; Stockman, Y.; Szwec, N.; Tamiatto, C.; Tandy, J.; Teriaca, L.; Theobald, C.; Tychon, I.; van Driel-Gesztelyi, L.; Verbeeck, C.; Vial, J. -C.; Werner, S.; West, M. J.; Westwood, D.; Wiegelmann, T.; Willis, G.; Winter, B.; Zerr, A.; Zhang, X.; Zhukov, A. N. Bibcode: 2020A&A...642A...8R Altcode: Context. The Extreme Ultraviolet Imager (EUI) is part of the remote sensing instrument package of the ESA/NASA Solar Orbiter mission that will explore the inner heliosphere and observe the Sun from vantage points close to the Sun and out of the ecliptic. Solar Orbiter will advance the "connection science" between solar activity and the heliosphere.
Aims: With EUI we aim to improve our understanding of the structure and dynamics of the solar atmosphere, globally as well as at high resolution, and from high solar latitude perspectives.
Methods: The EUI consists of three telescopes, the Full Sun Imager and two High Resolution Imagers, which are optimised to image in Lyman-α and EUV (17.4 nm, 30.4 nm) to provide a coverage from chromosphere up to corona. The EUI is designed to cope with the strong constraints imposed by the Solar Orbiter mission characteristics. Limited telemetry availability is compensated by state-of-the-art image compression, onboard image processing, and event selection. The imposed power limitations and potentially harsh radiation environment necessitate the use of novel CMOS sensors. As the unobstructed field of view of the telescopes needs to protrude through the spacecraft's heat shield, the apertures have been kept as small as possible, without compromising optical performance. This led to a systematic effort to optimise the throughput of every optical element and the reduction of noise levels in the sensor.
Results: In this paper we review the design of the two elements of the EUI instrument: the Optical Bench System and the Common Electronic Box. Particular attention is also given to the onboard software, the intended operations, the ground software, and the foreseen data products.
Conclusions: The EUI will bring unique science opportunities thanks to its specific design, its viewpoint, and to the planned synergies with the other Solar Orbiter instruments. In particular, we highlight science opportunities brought by the out-of-ecliptic vantage point of the solar poles, the high-resolution imaging of the high chromosphere and corona, and the connection to the outer corona as observed by coronagraphs. Title: Dynamics of Late-stage Reconnection in the 2017 September 10 Solar Flare Authors: French, Ryan J.; Matthews, Sarah A.; van Driel-Gesztelyi, Lidia; Long, David M.; Judge, Philip G. Bibcode: 2020ApJ...900..192F Altcode: 2020arXiv200713377F In this multi-instrument paper, we search for evidence of sustained magnetic reconnection far beyond the impulsive phase of the X8.2-class solar flare on 2017 September 10. Using Hinode/EIS, CoMP, SDO/AIA, K-Cor, Hinode/XRT, RHESSI, and IRIS, we study the late-stage evolution of the flare dynamics and topology, comparing signatures of reconnection with those expected from the standard solar flare model. Examining previously unpublished EIS data, we present the evolution of nonthermal velocity and temperature within the famous plasma sheet structure, for the first four hours of the flare's duration. On even longer timescales, we use differential emission measures and polarization data to study the longevity of the flare's plasma sheet and cusp structure, discovering that the plasma sheet is still visible in observations of CoMP linear polarization on 2017 September 11, long after its last appearance in EUV. We deduce that magnetic reconnection of some form is still ongoing at this time—27 hr after flare onset. Title: Spectropolarimetric Insight into Plasma Sheet Dynamics of a Solar Flare Authors: French, R.; Judge, P.; Matthews, S.; van Driel-Gesztelyi, L.; Long, D. Bibcode: 2020SPD....5121102F Altcode: Magnetic reconnection is thought to lie at the heart of energy release in solar flares, but the process is not yet fully understood. We examine spectropolarimetric data from the CoMP coronagraph, acquired a few hours into the evolution of the September 10th 2017 X8.2-class flare. We find a striking and spatially coherent low polarisation structure, aligned with the hot plasma sheet observed in EUV. By elimination, we find the significant depolarisation to be a result of small-scale sub-pixel magnetic structure along the plasma sheet, consistent with theory of reconnection instabilities. This interpretation of ongoing reconnection is supported by further Hinode/EIS observations and AIA DEMs, from well beyond the impulsive phase of the flare. The plasma sheet remains visible in CoMP linear polarisation over a day into the flare's evolution, several hours after its last appearance in EUV. We conclude that polarisation measurements with new coronagraphs, such the DKIST CRYO-NIRSP instrument, will further enhance our understanding of magnetic reconnection during eruptive flares. Title: Editorial: Solar Wind at the Dawn of the Parker Solar Probe and Solar Orbiter Era Authors: Lapenta, Giovanni; Zhukov, Andrei; van Driel-Gesztelyi, Lidia Bibcode: 2020SoPh..295..103L Altcode: Solar Wind 15 brought together almost 250 experts from all continents of the world to discuss the current trends and future perspectives of the research on the Sun and its solar wind. The present article collection recaptures some of the highlights of their contributions. Title: Can Subphotospheric Magnetic Reconnection Change the Elemental Composition in the Solar Corona? Authors: Baker, Deborah; van Driel-Gesztelyi, Lidia; Brooks, David H.; Démoulin, Pascal; Valori, Gherardo; Long, David M.; Laming, J. Martin; To, Andy S. H.; James, Alexander W. Bibcode: 2020ApJ...894...35B Altcode: 2020arXiv200303325B Within the coronae of stars, abundances of those elements with low first ionization potential (FIP) often differ from their photospheric values. The coronae of the Sun and solar-type stars mostly show enhancements of low-FIP elements (the FIP effect) while more active stars such as M dwarfs have coronae generally characterized by the inverse-FIP effect (I-FIP). Here we observe patches of I-FIP effect solar plasma in AR 12673, a highly complex βγδ active region. We argue that the umbrae of coalescing sunspots, and more specifically strong light bridges within the umbrae, are preferential locations for observing I-FIP effect plasma. Furthermore, the magnetic complexity of the active region and major episodes of fast flux emergence also lead to repetitive and intense flares. The induced evaporation of the chromospheric plasma in flare ribbons crossing umbrae enables the observation of four localized patches of I-FIP effect plasma in the corona of AR 12673. These observations can be interpreted in the context of the ponderomotive force fractionation model which predicts that plasma with I-FIP effect composition is created by the refraction of waves coming from below the chromosphere. We propose that the waves generating the I-FIP effect plasma in solar active regions are generated by subphotospheric reconnection of coalescing flux systems. Although we only glimpse signatures of I-FIP effect fractionation produced by this interaction in patches on the Sun, on highly active M stars it may be the dominant process. Title: Editorial Appreciation Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2020SoPh..295....9L Altcode: No abstract at ADS Title: Spectropolarimetric Insight into Plasma Sheet Dynamics of a Solar Flare Authors: French, Ryan J.; Judge, Philip G.; Matthews, Sarah A.; van Driel-Gesztelyi, Lidia Bibcode: 2019ApJ...887L..34F Altcode: 2019arXiv191112666F We examine spectropolarimetric data from the Coronal Multi-channel Polarimeter (CoMP) instrument, acquired during the evolution of the 2017 September 10 X8.2 solar flare on the western solar limb. CoMP captured linearly polarized light from two emission lines of Fe XIII at 1074.7 and 1079.8 nm, from 1.03 to 1.5 solar radii. We focus here on the hot plasma sheet lying above the bright flare loops and beneath the ejected coronal mass ejection. The polarization has a striking and coherent spatial structure, with unexpectedly small polarization aligned with the plasma sheet. By elimination, we find that small-scale magnetic field structure is needed to cause such significant depolarization, and suggest that plasmoid formation during reconnection (associated with the tearing-mode instability) creates magnetic structure on scales below instrument resolution of 6 Mm. We conclude that polarization measurements with new coronagraphs, such as the upcoming Daniel K. Inouye Solar Telescope, will further enhance our understanding of magnetic reconnection and development of turbulence in the solar corona. Title: Understanding the Plasma and Magnetic Field Evolution of a Filament Using Observations and Nonlinear Force-free Field Modeling Authors: Yardley, Stephanie L.; Savcheva, Antonia; Green, Lucie M.; van Driel-Gesztelyi, Lidia; Long, David; Williams, David R.; Mackay, Duncan H. Bibcode: 2019ApJ...887..240Y Altcode: 2019arXiv191101314Y We present observations and magnetic field models of an intermediate filament present on the Sun in 2012 August, associated with a polarity inversion line that extends from AR 11541 in the east into the quiet Sun at its western end. A combination of Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly, SDO/Helioseismic and Magnetic Imager (HMI), and Global Oscillation Network Group Hα data allow us to analyze the structure and evolution of the filament from 2012 August 4 23:00 UT to 2012 August 6 08:00 UT when the filament was in equilibrium. By applying the flux rope insertion method, nonlinear force-free field models of the filament are constructed using SDO/HMI line-of-sight magnetograms as the boundary condition at the two times given above. Guided by observed filament barbs, both modeled flux ropes are split into three sections each with a different value of axial flux to represent the nonuniform photospheric field distribution. The flux in the eastern section of the rope increases by 4 × 1020 Mx between the two models, which is in good agreement with the amount of flux canceled along the internal PIL of AR 11541, calculated to be 3.2 × 1020 Mx. This suggests that flux cancellation builds flux into the filament’s magnetic structure. Additionally, the number of field line dips increases between the two models in the locations where flux cancellation, the formation of new filament threads, and growth of the filament is observed. This suggests that flux cancellation associated with magnetic reconnection forms concave-up magnetic field that lifts plasma into the filament. During this time, the free magnetic energy in the models increases by 0.2 × 1031 ergs. Title: Polarized radiative transfer, rotation measure fluctuations, and large-scale magnetic fields Authors: On, Alvina Y. L.; Chan, Jennifer Y. H.; Wu, Kinwah; Saxton, Curtis J.; van Driel-Gesztelyi, Lidia Bibcode: 2019MNRAS.490.1697O Altcode: 2019arXiv190906703O; 2019MNRAS.tmp.2320O Faraday rotation measure (RM) at radio wavelengths is commonly used to diagnose large-scale magnetic fields. It is argued that the length-scales on which magnetic fields vary in large-scale diffuse astrophysical media can be inferred from correlations in the observed RM. RM is a variable which can be derived from the polarized radiative transfer equations in restrictive conditions. This paper assesses the usage of rotation measure fluctuation (RMF) analyses for magnetic field diagnostics in the framework of polarized radiative transfer. We use models of various magnetic field configurations and electron density distributions to show how density fluctuations could affect the correlation length of the magnetic fields inferred from the conventional RMF analyses. We caution against interpretations of RMF analyses when a characteristic density is ill defined, e.g. in cases of lognormal-distributed and fractal-like density structures. As the spatial correlations are generally not the same in the line-of-sight longitudinal direction and the sky plane direction, one also needs to clarify the context of RMF when inferring from observational data. In complex situations, a covariant polarized radiative transfer calculation is essential to capture all aspects of radiative and transport processes, which would otherwise ambiguate the interpretations of magnetism in galaxy clusters and larger scale cosmological structures. Title: Flaring Activity of Proxima Centauri from TESS Observations: Quasiperiodic Oscillations during Flare Decay and Inferences on the Habitability of Proxima b Authors: Vida, Krisztián; Oláh, Katalin; Kővári, Zsolt; van Driel-Gesztelyi, Lidia; Moór, Attila; Pál, András Bibcode: 2019ApJ...884..160V Altcode: 2019arXiv190712580V We analyze the light curve of the M5.5 dwarf Proxima Centauri obtained by the Transiting Exoplanet Survey Satellite (TESS) in Sectors 11 and 12. In the ≈50 day long light curve we identified and analyzed 72 flare events. The flare rate was 1.49 events per day; in total, 7.2% of the observing time was classified as flaring. The estimated flare energies were on the order of 1030-1032 erg in the TESS passband (≈4.8× higher in bolometric energies, but on the same order of magnitude). Most of the eruptions appeared in groups. Two events showed quasiperiodic oscillations during their decay phase with a timescale of a few hours, which could be caused by quasiperiodic motions of the emitting plasma or oscillatory reconnection. From the cumulative flare frequency distribution we estimate that superflares with energy output of 1033 erg are expected to occur three times per year, while magnitude larger events (with 1034 erg) can occur every second year. This reduces the chances of habitability of Proxima Cen b, although earlier numerical models did not rule out the existence of liquid water on the planetary surface. We did not find any obvious signs of planetary transit in the light curve. Title: Spectroscopic Signatures of Plasma-Sheet Dynamics in a Solar Flare Authors: French, Ryan J.; Matthews, Sarah A.; van Driel-Gesztelyi, Lidia; Long, David M. Bibcode: 2019shin.confE.186F Altcode: According to the standard eruptive flare model, energy is released in a current sheet formed in the wake of an erupting flux rope. The current sheet itself is theoretically predicted to be 10m wide, thus representing a significant challenge for current observational techniques. However, a handful of observations have reported enhanced emission from the region surrounding the current sheet, often referred to as the plasma-sheet. Since this region must respond to processes occurring in the current sheet itself, the study of its properties offers the possibility to indirectly probe conditions in the current sheet related to the reconnection process. Recent observations (Warren al., (2018), Li et al., 2018) have demonstrated the presence of enhanced nonthermal velocities in the current sheet observed in the 10th September 2017 X8.2 class flare, consistent with the presence of turbulence and possible tearing mode instability. In this study, we combine observations from the Extreme-ultraviolet Imaging Spectrometer (EIS) and Atmospheric Imaging Assembly (AIA) to explore the relationship between the Alfven speed calculated for different plasma beta regimes, observed non-thermal velocity measurements, and the evolution of the plasma-sheet to test for the presence of the plasmoid instability. Title: Transient Inverse-FIP Plasma Composition Evolution within a Solar Flare Authors: Baker, Deborah; van Driel-Gesztelyi, Lidia; Brooks, David H.; Valori, Gherardo; James, Alexander W.; Laming, J. Martin; Long, David M.; Démoulin, Pascal; Green, Lucie M.; Matthews, Sarah A.; Oláh, Katalin; Kővári, Zsolt Bibcode: 2019ApJ...875...35B Altcode: 2019arXiv190206948B Understanding elemental abundance variations in the solar corona provides an insight into how matter and energy flow from the chromosphere into the heliosphere. Observed variations depend on the first ionization potential (FIP) of the main elements of the Sun’s atmosphere. High-FIP elements (>10 eV) maintain photospheric abundances in the corona, whereas low-FIP elements have enhanced abundances. Conversely, inverse FIP (IFIP) refers to the enhancement of high-FIP or depletion of low-FIP elements. We use spatially resolved spectroscopic observations, specifically the Ar XIV/Ca XIV intensity ratio, from Hinode’s Extreme-ultraviolet Imaging Spectrometer to investigate the distribution and evolution of plasma composition within two confined flares in a newly emerging, highly sheared active region. During the decay phase of the first flare, patches above the flare ribbons evolve from the FIP to the IFIP effect, while the flaring loop tops show a stronger FIP effect. The patch and loop compositions then evolve toward the preflare basal state. We propose an explanation of how flaring in strands of highly sheared emerging magnetic fields can lead to flare-modulated IFIP plasma composition over coalescing umbrae which are crossed by flare ribbons. Subsurface reconnection between the coalescing umbrae leads to the depletion of low-FIP elements as a result of an increased wave flux from below. This material is evaporated when the flare ribbons cross the umbrae. Our results are consistent with the ponderomotive fractionation model for the creation of IFIP-biased plasma. Title: Modeling the Effect of Mass-draining on Prominence Eruptions Authors: Jenkins, Jack M.; Hopwood, Matthew; Démoulin, Pascal; Valori, Gherardo; Aulanier, Guillaume; Long, David M.; van Driel-Gesztelyi, Lidia Bibcode: 2019ApJ...873...49J Altcode: 2019arXiv190110970J Quiescent solar prominences are observed within the solar atmosphere for up to several solar rotations. Their eruption is commonly preceded by a slow increase in height that can last from hours to days. This increase in the prominence height is believed to be due to their host magnetic flux rope transitioning through a series of neighboring quasi-equilibria before the main loss of equilibrium that drives the eruption. Recent work suggests that the removal of prominence mass from a stable, quiescent flux rope is one possible cause for this change in height. However, these conclusions are drawn from observations and are subject to interpretation. Here, we present a simple model to quantify the effect of “mass-draining” during the pre-eruptive height evolution of a solar flux rope. The flux rope is modeled as a line current suspended within a background potential magnetic field. We first show that the inclusion of mass, up to 1012 kg, can modify the height at which the line current experiences loss of equilibrium by up to 14%. Next, we show that the rapid removal of mass prior to the loss of equilibrium can allow the height of the flux rope to increase sharply and without an upper bound as it approaches its loss-of-equilibrium point. This indicates that the critical height for the loss of equilibrium can occur at a range of heights depending explicitly on the amount and evolution of mass within the flux rope. Finally, we demonstrate that for the same amount of drained mass, the effect on the height of the flux rope is up to two orders of magnitude larger for quiescent prominences than for active region prominences. Title: The quest for stellar coronal mass ejections in late-type stars. I. Investigating Balmer-line asymmetries of single stars in Virtual Observatory data Authors: Vida, Krisztián; Leitzinger, Martin; Kriskovics, Levente; Seli, Bálint; Odert, Petra; Kovács, Orsolya Eszter; Korhonen, Heidi; van Driel-Gesztelyi, Lidia Bibcode: 2019A&A...623A..49V Altcode: 2019arXiv190104229V Context. Flares and coronal mass ejections (CMEs) can have deleterious effects on their surroundings: they can erode or completely destroy atmospheres of orbiting planets over time and also have high importance in stellar evolution. Most of the CME detections in the literature are single events found serendipitously sparse for statistical investigation.
Aims: We aimed to gather a large amount of spectral data of M-dwarfs to drastically increase the number of known events to make statistical analysis possible in order to study the properties of potential stellar CMEs.
Methods: Using archival spectral data we investigated asymmetric features of Balmer-lines, which could indicate the Doppler-signature of ejected material.
Results: Of more than 5500 spectra we find 478 that have line asymmetries - including nine larger events, in terms of velocity and mass - on 25 objects, with 1.2-19.6 events per day on objects with line asymmetries. Most events are connected with enhanced peaks of Balmer-lines, indicating that these are connected to flares similar to solar events. In most cases the detected speed does not reach surface escape velocity: the typical observed maximum velocities are on the order of 100-300 km s-1, while the typical masses of the ejecta were on the order of 1015-1018 g. Statistical analysis of the events suggests that these events are more frequent on cooler stars with stronger chromospheric activity.
Conclusions: If the detected events correspond to CMEs, the detected maximum velocities are lower than those observed on the Sun, while event rates were somewhat lower than we could expect from the solar case. If the velocities are not distorted significantly due to a projection effect, these findings may support the idea that most of the coronal mass ejections could be suppressed by a strong magnetic field. Alternatively, it is possible that we can observe only an early low-coronal phase of the events before being accelerated at higher altitudes. Our findings could indicate that later-type, active dwarfs could be a safer environment for exoplanetary systems CME-wise than previously thought, and atmosphere loss due to radiation effects would play a stronger role in exoplanetary atmosphere evolution than CMEs. Title: Editorial Appreciation Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2019SoPh..294....3L Altcode: We are pleased to acknowledge, with sincere thanks, the following colleagues who supported the community by reviewing articles for Solar Physics during 2018. Title: An Observationally Constrained Model of a Flux Rope that Formed in the Solar Corona Authors: James, Alexander W.; Valori, Gherardo; Green, Lucie M.; Liu, Yang; Cheung, Mark C. M.; Guo, Yang; van Driel-Gesztelyi, Lidia Bibcode: 2018csc..confE...9J Altcode: Coronal mass ejections (CMEs) are large-scale eruptions of plasma from the coronae of stars, and it is important to study the plasma processes involved in their initiation. This first requires us to understand the pre-eruptive configuration of CMEs. To this end, we used extreme-ultraviolet (EUV) observations from SDO/AIA to conclude that a magnetic flux rope formed high-up in the solar corona above NOAA Active Region 11504 before it erupted on 2012 June 14. Then, we used data from SDO/HMI and our knowledge of the EUV observations to model the coronal magnetic field of the active region one hour prior to eruption using a nonlinear force-free field extrapolation. The extrapolation revealed a flux rope that matches the EUV observations remarkably well, with its axis 120 Mm above the photosphere. The erupting structure was not observed to kink, but the decay index near the apex of the axis of the extrapolated flux rope is comparable to typical critical values required for the onset of the torus instability. Therefore, we suggest that the torus instability drove the eruption of the flux rope. Title: Understanding the Role of Mass-Unloading in a Filament Eruption Authors: Jenkins, Jack; Long, David; van Driel-Gesztelyi, Lidia; Carlyle, Jack; Hopwood, Matthew Bibcode: 2018csc..confE..17J Altcode: We combine observations of a partial filament eruption on 11 December 2011 with a simple line-current model to demonstrate that including mass is an important next step for understanding solar eruptions. Observations from the Solar Terrestrial Relations Observatory-Behind (STEREO-B) and the Solar Dynamics Observatory (SDO) spacecraft were used to remove line-of-sight projection effects in filament motion and correlate the effect of plasma dynamics with the evolution of the filament height. The two viewpoints enable the amount of mass drained to be estimated, and an investigation of the subsequent radial expansion and eruption of the filament. We use these observational measurements to constrain a line-current model and quantitatively demonstrate the important role that the presence and draining of mass has in the lead-up to solar eruptions. Specifically, we show that the balance of magnetic and gravitational forces acting on the line-current is increasingly sensitive to mass perturbations as it approaches its loss-of-equilibrium. Finally, we conclude that the eruption of the observed filament was restrained until 70% of the mass had drained from the structure. Title: The Role of Flux Cancellation in Eruptions from Bipolar ARs Authors: Yardley, S. L.; Green, L. M.; van Driel-Gesztelyi, L.; Williams, D. R.; Mackay, D. H. Bibcode: 2018ApJ...866....8Y Altcode: 2018arXiv180810635Y The physical processes or trigger mechanisms that lead to the eruption of coronal mass ejections (CMEs), the largest eruptive phenomenon in the heliosphere, are still undetermined. Low-altitude magnetic reconnection associated with flux cancellation appears to play an important role in CME occurrence as it can form an eruptive configuration and reduce the magnetic flux that contributes to the overlying, stabilizing field. We conduct the first comprehensive study of 20 small bipolar ARs (ARs) in order to probe the role of flux cancellation as an eruption trigger mechanism. We categorize eruptions from the bipolar regions into three types related to location, and find that the type of eruption produced depends on the evolutionary stage of the AR. In addition, we find that ARs that form eruptive structures by flux cancellation (low-altitude reconnection) had, on average, lower flux cancellation rates than the AR sample as a whole. Therefore, while flux cancellation plays a key role, by itself it is insufficient for the production of an eruption. The results provide supporting evidence that although flux cancellation in a sheared arcade may be able to build an eruptive configuration, a successful eruption depends upon the removal of sufficient overlying and stabilizing field. Convergence of the bipole polarities also appears to be present in regions that produce an eruption. These findings have important implications for understanding the physical processes that occur on our Sun in relation to CMEs and for space weather forecasting. Title: Sequential Eruptions Triggered by Flux Emergence: Observations and Modeling Authors: Dacie, S.; Török, T.; Démoulin, P.; Linton, M. G.; Downs, C.; van Driel-Gesztelyi, L.; Long, D. M.; Leake, J. E. Bibcode: 2018ApJ...862..117D Altcode: 2018arXiv180700020D We describe and analyze observations by the Solar Dynamics Observatory of the emergence of a small, bipolar active region within an area of unipolar magnetic flux that was surrounded by a circular, quiescent filament. Within only 8 hours from the start of the emergence, a partial splitting of the filament and two consecutive coronal mass ejections took place. We argue that all three dynamic events occurred as a result of particular magnetic-reconnection episodes between the emerging bipole and the pre-existing coronal magnetic field. To substantiate our interpretation, we consider 3D magnetohydrodynamic simulations that model the emergence of magnetic flux in the vicinity of a large-scale coronal flux rope. The simulations qualitatively reproduce most of the reconnection episodes suggested by the observations, as well as the filament splitting, the first eruption, and the formation of sheared/twisted fields that may have played a role in the second eruption. Our results suggest that the position of emerging flux with respect to the background magnetic configuration is a crucial factor for the resulting evolution, while previous results suggest that parameters such as the orientation or the amount of emerging flux are important as well. This poses a challenge for predicting the onset of eruptions that are triggered by flux emergence, and calls for a detailed survey of the relevant parameter space by means of numerical simulations. Title: Solar Cycle Observations of the Neon Abundance in the Sun-as-a-star Authors: Brooks, David H.; Baker, Deborah; van Driel-Gesztelyi, Lidia; Warren, Harry P. Bibcode: 2018ApJ...861...42B Altcode: 2018arXiv180507032B Properties of the Sun’s interior can be determined accurately from helioseismological measurements of solar oscillations. These measurements, however, are in conflict with photospheric elemental abundances derived using 3D hydrodynamic models of the solar atmosphere. This divergence of theory and helioseismology is known as the “solar modeling problem.” One possible solution is that the photospheric neon abundance, which is deduced indirectly by combining the coronal Ne/O ratio with the photospheric O abundance, is larger than generally accepted. There is some support for this idea from observations of cool stars. The Ne/O abundance ratio has also been found to vary with the solar cycle in the slowest solar wind streams and coronal streamers, and the variation from solar maximum to minimum in streamers (∼0.1-0.25) is large enough to potentially bring some of the solar models into agreement with the seismic data. Here we use daily sampled observations from the EUV Variability Experiment on the Solar Dynamics Observatory taken in 2010-2014, to investigate whether the coronal Ne/O abundance ratio shows a variation with the solar cycle when the Sun is viewed as a star. We find only a weak dependence on, and moderate anti-correlation with, the solar cycle with the ratio measured around 0.2-0.3 MK falling from 0.17 at solar minimum to 0.11 at solar maximum. The effect is amplified at higher temperatures (0.3-0.6 MK) with a stronger anti-correlation and the ratio falling from 0.16 at solar minimum to 0.08 at solar maximum. The values we find at solar minimum are too low to solve the solar modeling problem. Title: Understanding the Role of Mass-Unloading in a Filament Eruption Authors: Jenkins, Jack Michael; Long, David; van Driel-Gesztelyi, Lidia; Carlyle, Jack Bibcode: 2018tess.conf10907J Altcode: Solar filaments are persistent features on the solar surface, lasting from days to months before either successfully erupting into the heliosphere as part of a CME, or collapsing and returning the suspended plasma to the chromosphere. To date, the consensus has been that the plasma comprising the filament plays no significant role in the global evolution of the host flux rope. As a result, little effort has been made to quantify the impact that mass has on the evolution of magnetic structures in the solar atmosphere. Here we present observations and analysis that suggest that the inclusion of mass is an important next step to fully understand solar eruptions. A partial filament eruption that occurred on 11 December 2011 was observed by both the Solar Terrestrial Relations Observatory-Behind (STEREO-B) and the Solar Dynamics Observatory (SDO) spacecraft. The combination of multiple perspectives from different locations within the heliosphere allowed the removal of line-of-sight projection effects, and the correlation of plasma dynamics to the evolution in filament height. Our results show that 70\% of the measurable filament mass drained shortly \textit{prior} to a change in the height--time expansion profile of the remaining filament material from a shallow to steeper exponential. A proxy was then formulated to test whether the observed mass-unloading was responsible for this observed change in behaviour. This proxy is defined as the ratio between the upward force supplied to the host flux rope due to this mass-unloading and the restraining force caused by the tension of the overlying magnetic field. A ratio range of between 1.8 and 4.1 was found, indicating that the upward force as a result of the the mass-unloading dominated the evolution. We conclude that the unloading of filament mass from the host flux rope was likely responsible for the accelerated expansion. Title: Václav Bumba (1925 - 2018) Authors: Kotrč, Pavel; Heinzel, Petr; Sobotka, Michal; Ambrož, Pavel; van Driel-Gesztelyi, Lidia Bibcode: 2018SoPh..293...40K Altcode: No abstract at ADS Title: An Observationally Constrained Model of a Flux Rope that Formed in the Solar Corona Authors: James, Alexander W.; Valori, Gherardo; Green, Lucie M.; Liu, Yang; Cheung, Mark C. M.; Guo, Yang; van Driel-Gesztelyi, Lidia Bibcode: 2018ApJ...855L..16J Altcode: 2018arXiv180207965J Coronal mass ejections (CMEs) are large-scale eruptions of plasma from the coronae of stars. Understanding the plasma processes involved in CME initiation has applications for space weather forecasting and laboratory plasma experiments. James et al. used extreme-ultraviolet (EUV) observations to conclude that a magnetic flux rope formed in the solar corona above NOAA Active Region 11504 before it erupted on 2012 June 14 (SOL2012-06-14). In this work, we use data from the Solar Dynamics Observatory (SDO) to model the coronal magnetic field of the active region one hour prior to eruption using a nonlinear force-free field extrapolation, and find a flux rope reaching a maximum height of 150 Mm above the photosphere. Estimations of the average twist of the strongly asymmetric extrapolated flux rope are between 1.35 and 1.88 turns, depending on the choice of axis, although the erupting structure was not observed to kink. The decay index near the apex of the axis of the extrapolated flux rope is comparable to typical critical values required for the onset of the torus instability, so we suggest that the torus instability drove the eruption. Title: Coronal Elemental Abundances in Solar Emerging Flux Regions Authors: Baker, Deborah; Brooks, David H.; van Driel-Gesztelyi, Lidia; James, Alexander W.; Démoulin, Pascal; Long, David M.; Warren, Harry P.; Williams, David R. Bibcode: 2018ApJ...856...71B Altcode: 2018arXiv180108424B The chemical composition of solar and stellar atmospheres differs from the composition of their photospheres. Abundances of elements with low first ionization potential (FIP) are enhanced in the corona relative to high-FIP elements with respect to the photosphere. This is known as the FIP effect and it is important for understanding the flow of mass and energy through solar and stellar atmospheres. We used spectroscopic observations from the Extreme-ultraviolet Imaging Spectrometer on board the Hinode observatory to investigate the spatial distribution and temporal evolution of coronal plasma composition within solar emerging flux regions inside a coronal hole. Plasma evolved to values exceeding those of the quiet-Sun corona during the emergence/early-decay phase at a similar rate for two orders of magnitude in magnetic flux, a rate comparable to that observed in large active regions (ARs) containing an order of magnitude more flux. During the late-decay phase, the rate of change was significantly faster than what is observed in large, decaying ARs. Our results suggest that the rate of increase during the emergence/early-decay phase is linked to the fractionation mechanism that leads to the FIP effect, whereas the rate of decrease during the later decay phase depends on the rate of reconnection with the surrounding magnetic field and its plasma composition. Title: Editorial Appreciation Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2018SoPh..293...14L Altcode: No abstract at ADS Title: Understanding the Role of Mass-Unloading in a Filament Eruption Authors: Jenkins, J. M.; Long, D. M.; van Driel-Gesztelyi, L.; Carlyle, J. Bibcode: 2018SoPh..293....7J Altcode: 2017arXiv171102565J We describe a partial filament eruption on 11 December 2011 that demonstrates that the inclusion of mass is an important next step for understanding solar eruptions. Observations from the Solar Terrestrial Relations Observatory-Behind (STEREO-B) and the Solar Dynamics Observatory (SDO) spacecraft were used to remove line-of-sight projection effects in filament motion and correlate the effect of plasma dynamics with the evolution of the filament height. Flux cancellation and nearby flux emergence are shown to have played a role in increasing the height of the filament prior to eruption. The two viewpoints allow the quantitative estimation of a large mass-unloading, the subsequent radial expansion, and the eruption of the filament to be investigated. A 1.8 to 4.1 lower-limit ratio between gravitational and magnetic-tension forces was found. We therefore conclude that following the loss-of-equilibrium of the flux-rope, the radial expansion of the flux-rope was restrained by the filamentary material until 70% of the mass had evacuated the structure through mass-unloading. Title: The Life Cycle of Active Region Magnetic Fields Authors: Cheung, M. C. M.; van Driel-Gesztelyi, L.; Martínez Pillet, V.; Thompson, M. J. Bibcode: 2018smf..book..317C Altcode: No abstract at ADS Title: Non-thermal distributions and energy transport in the solar flares Authors: Matthews, Sarah; del Zanna, Guilio; Calcines, Ariadna; Mason, Helen; Mathioudakis, Mihalis; Culhane, Len; Harra, Louise; van Driel-Gesztelyi, Lidia; Green, Lucie; Long, David; Baker, Deb; Valori, Gherardo Bibcode: 2017arXiv171200773M Altcode: Determining the energy transport mechanisms in flares remains a central goal in solar flares physics that is still not adequately answered by the 'standard flare model'. In particular, the relative roles of particles and/or waves as transport mechanisms, the contributions of low energy protons and ions to the overall flare budget, and the limits of low energy non-thermal electron distribution are questions that still cannot be adequately reconciled with current instrumentation. In this 'White Paper' submitted in response to the call for inputs to the Next Generation Solar Physics Mission review process initiated by JAXA, NASA and ESA in 2016, we outline the open questions in this area and possible instrumentation that could provide the required observations to help answer these and other flare-related questions. Title: Editorial: Last Print Issue of Solar Physics Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2017SoPh..292..196L Altcode: No abstract at ADS Title: Field distribution of magnetograms from simulations of active region formation Authors: Dacie, S.; van Driel-Gesztelyi, L.; Démoulin, P.; Linton, M. G.; Leake, J. E.; MacTaggart, D.; Cheung, M. C. M. Bibcode: 2017A&A...606A..34D Altcode: Context. The evolution of the photospheric magnetic field distributions (probability densities) has previously been derived for a set of active regions. Photospheric field distributions are a consequence of physical processes that are difficult to determine from observations alone.
Aims: We analyse simulated magnetograms from numerical simulations, which model the emergence and decay of active regions. These simulations have different experimental set-ups and include different physical processes, allowing us to investigate the relative importance of convection, magnetic buoyancy, magnetic twist, and braiding for flux emergence.
Methods: We specifically studied the photospheric field distributions (probability densities found with a kernel density estimation analysis) and compared the results with those found from observations.
Results: Simulations including convection most accurately reproduce the observed evolution of the photospheric field distributions during active region evolution.
Conclusions: This indicates that convection may play an important role during the decay phase and also during the formation of active regions, particularly for low flux density values. Title: The Life Cycle of Active Region Magnetic Fields Authors: Cheung, M. C. M.; van Driel-Gesztelyi, L.; Martínez Pillet, V.; Thompson, M. J. Bibcode: 2017SSRv..210..317C Altcode: 2016SSRv..tmp...46C We present a contemporary view of how solar active region magnetic fields are understood to be generated, transported and dispersed. Empirical trends of active region properties that guide model development are discussed. Physical principles considered important for active region evolution are introduced and advances in modeling are reviewed. Title: The 2015 St Patrick's Day Storm: Origins Authors: Carlyle, Jack; van Driel-Gesztelyi, Lidia; Zuccarello, Francesco; James, Alexander; Williams, David Bibcode: 2017SPD....4840402C Altcode: The magnetic storm experienced at Earth on St. Patrick's Day 2015 had been the strongest of cycle 24 (at that time) with a measured DST of -223 nT, though it was not expected to cause much of a disturbance. In this work we study the solar source region of several peculiar eruptions, leading to the formation and destruction of various structures, in the week leading up to the storm, and determine the true sequence of events. The evolution of the magnetic flux at the solar surface is examined in order to place suspected flux-ropes into context, and the evolution of the magnetic connectivities is described alongside a PFSS model of the surrounding region. The balance between positive and negative flux directly before two key eruptions is investigated in detail, in order to ascertain whether particular trigger mechanisms are feasible explanations. As well as these magnetic investigations, the column density of plasma involved is calculated from extreme ultraviolet images, and this is used to estimate the total mass of one filament, as well as select other features relevant to the eruptions. This information is then used to comment on the energy budgets and requirements of several processes in order to best understand the underlying drivers of this event.Previous studies on the St. Patrick's Day Storm are also incorporated into this work, and an attempt is made to reconcile the disparate conclusions drawn by the scientific community as to why this storm was not only so effective, but also a major forecasting failure. Title: A Solar cycle correlation of coronal element abundances in Sun-as-a-star observations Authors: Brooks, David H.; Baker, Deborah; van Driel-Gesztelyi, Lidia; Warren, Harry P. Bibcode: 2017NatCo...8..183B Altcode: 2018arXiv180200563B The elemental composition in the coronae of low-activity solar-like stars appears to be related to fundamental stellar properties such as rotation, surface gravity, and spectral type. Here we use full-Sun observations from the Solar Dynamics Observatory, to show that when the Sun is observed as a star, the variation of coronal composition is highly correlated with a proxy for solar activity, the F10.7 cm radio flux, and therefore with the solar cycle phase. Similar cyclic variations should therefore be detectable spectroscopically in X-ray observations of solar analogs. The plasma composition in full-disk observations of the Sun is related to the evolution of coronal magnetic field activity. Our observations therefore introduce an uncertainty into the nature of any relationship between coronal composition and fixed stellar properties. The results highlight the importance of systematic full-cycle observations for understanding the elemental composition of solar-like stellar coronae. Title: A study of the long term evolution in active region upflows Authors: Harra, Louise K.; Ugarte-Urra, Ignacio; De Rosa, Marc; Mandrini, Cristina; van Driel-Gesztelyi, Lidia; Baker, Deborah; Culhane, J. Leonard; Démoulin, Pascal Bibcode: 2017PASJ...69...47H Altcode: Since their discovery, upflows at the edges of active regions have attracted a lot of interest, primarily as they could potentially contribute to the slow solar wind. One aspect that has not been studied yet is how the long term evolution of active regions impacts the upflows. In this work, we analyze one active region that survives three solar rotations. We track how the flows change with time. We use local and global modeling of the decaying active region to determine how the age of the active region will impact the extent of the open magnetic fields, and then how some of the upflows could become outflows. We finish with a discussion of how these results, set in a broader context, can be further developed with the Solar Orbiter mission. Title: On-Disc Observations of Flux Rope Formation Prior to Its Eruption Authors: James, A. W.; Green, L. M.; Palmerio, E.; Valori, G.; Reid, H. A. S.; Baker, D.; Brooks, D. H.; van Driel-Gesztelyi, L.; Kilpua, E. K. J. Bibcode: 2017SoPh..292...71J Altcode: 2017arXiv170310837J Coronal mass ejections (CMEs) are one of the primary manifestations of solar activity and can drive severe space weather effects. Therefore, it is vital to work towards being able to predict their occurrence. However, many aspects of CME formation and eruption remain unclear, including whether magnetic flux ropes are present before the onset of eruption and the key mechanisms that cause CMEs to occur. In this work, the pre-eruptive coronal configuration of an active region that produced an interplanetary CME with a clear magnetic flux rope structure at 1 AU is studied. A forward-S sigmoid appears in extreme-ultraviolet (EUV) data two hours before the onset of the eruption (SOL2012-06-14), which is interpreted as a signature of a right-handed flux rope that formed prior to the eruption. Flare ribbons and EUV dimmings are used to infer the locations of the flux rope footpoints. These locations, together with observations of the global magnetic flux distribution, indicate that an interaction between newly emerged magnetic flux and pre-existing sunspot field in the days prior to the eruption may have enabled the coronal flux rope to form via tether-cutting-like reconnection. Composition analysis suggests that the flux rope had a coronal plasma composition, supporting our interpretation that the flux rope formed via magnetic reconnection in the corona. Once formed, the flux rope remained stable for two hours before erupting as a CME. Title: Editorial Appreciation Authors: Leibacher, John; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2017SoPh..292...19L Altcode: We are pleased to acknowledge, with sincere thanks, the following referees who supported the community by refereeing articles for Solar Physics during 2016. Title: Evolution of the magnetic field distribution of active regions Authors: Dacie, S.; Démoulin, P.; van Driel-Gesztelyi, L.; Long, D. M.; Baker, D.; Janvier, M.; Yardley, S. L.; Pérez-Suárez, D. Bibcode: 2016A&A...596A..69D Altcode: 2016arXiv160903723D
Aims: Although the temporal evolution of active regions (ARs) is relatively well understood, the processes involved continue to be the subject of investigation. We study how the magnetic field of a series of ARs evolves with time to better characterise how ARs emerge and disperse.
Methods: We examined the temporal variation in the magnetic field distribution of 37 emerging ARs. A kernel density estimation plot of the field distribution was created on a log-log scale for each AR at each time step. We found that the central portion of the distribution is typically linear, and its slope was used to characterise the evolution of the magnetic field.
Results: The slopes were seen to evolve with time, becoming less steep as the fragmented emerging flux coalesces. The slopes reached a maximum value of -1.5 just before the time of maximum flux before becoming steeper during the decay phase towards the quiet-Sun value of -3. This behaviour differs significantly from a classical diffusion model, which produces a slope of -1. These results suggest that simple classical diffusion is not responsible for the observed changes in field distribution, but that other processes play a significant role in flux dispersion.
Conclusions: We propose that the steep negative slope seen during the late-decay phase is due to magnetic flux reprocessing by (super)granular convective cells. Title: Editorial: 50 Years of Solar Physics Authors: Charbonneau, Paul; Leibacher, John; Mandrini, Cristina; van Driel-Gesztelyi, Lidia; Wheatland, Michael S. Bibcode: 2016SoPh..291.3461C Altcode: 2016SoPh..tmp..189C No abstract at ADS Title: Preface to Topical Issue: Waves in the Solar Corona: From Microphysics to Macrophysics Authors: Nakariakov, V. M.; Pascoe, D. J.; Sych, R.; van Driel-Gesztelyi, L. Bibcode: 2016SoPh..291.3139N Altcode: 2016SoPh..tmp..187N No abstract at ADS Title: Flux Cancellation and the Evolution of the Eruptive Filament of 2011 June 7 Authors: Yardley, S. L.; Green, L. M.; Williams, D. R.; van Driel-Gesztelyi, L.; Valori, G.; Dacie, S. Bibcode: 2016ApJ...827..151Y Altcode: 2016arXiv160608264Y We investigate whether flux cancellation is responsible for the formation of a very massive filament resulting in the spectacular eruption on 2011 June 7. We analyze and quantify the amount of flux cancellation that occurs in NOAA AR 11226 and its two neighboring active regions (ARs 11227 & 11233) using line-of-sight magnetograms from the Heliospheric Magnetic Imager. During a 3.6 day period building up to the eruption of the filament, 1.7 × 1021 Mx, 21% of AR 11226's maximum magnetic flux, was canceled along the polarity inversion line (PIL) where the filament formed. If the flux cancellation continued at the same rate up until the eruption then up to 2.8 × 1021 Mx (34% of the AR flux) may have been built into the magnetic configuration that contains the filament plasma. The large flux cancellation rate is due to an unusual motion of the positive-polarity sunspot, which splits, with the largest section moving rapidly toward the PIL. This motion compresses the negative polarity and leads to the formation of an orphan penumbra where one end of the filament is rooted. Dense plasma threads above the orphan penumbra build into the filament, extending its length, and presumably injecting material into it. We conclude that the exceptionally strong flux cancellation in AR 11226 played a significant role in the formation of its unusually massive filament. In addition, the presence and coherent evolution of bald patches in the vector magnetic field along the PIL suggest that the magnetic field configuration supporting the filament material is that of a flux rope. Title: An Investigation of the Sources of Earth-directed Solar Wind during Carrington Rotation 2053 Authors: Fazakerley, A. N.; Harra, L. K.; van Driel-Gesztelyi, L. Bibcode: 2016ApJ...823..145F Altcode: In this work we analyze multiple sources of solar wind through a full Carrington Rotation (CR 2053) by analyzing the solar data through spectroscopic observations of the plasma upflow regions and the in situ data of the wind itself. Following earlier authors, we link solar and in situ observations by a combination of ballistic backmapping and potential-field source-surface modeling. We find three sources of fast solar wind that are low-latitude coronal holes. The coronal holes do not produce a steady fast wind, but rather a wind with rapid fluctuations. The coronal spectroscopic data from Hinode’s Extreme Ultraviolet Imaging Spectrometer show a mixture of upflow and downflow regions highlighting the complexity of the coronal hole, with the upflows being dominant. There is a mix of open and multi-scale closed magnetic fields in this region whose (interchange) reconnections are consistent with the up- and downflows they generate being viewed through an optically thin corona, and with the strahl directions and freeze-in temperatures found in in situ data. At the boundary of slow and fast wind streams there are three short periods of enhanced-velocity solar wind, which we term intermediate based on their in situ characteristics. These are related to active regions that are located beside coronal holes. The active regions have different magnetic configurations, from bipolar through tripolar to quadrupolar, and we discuss the mechanisms to produce this intermediate wind, and the important role that the open field of coronal holes adjacent to closed-field active regions plays in the process. Title: Photospheric Vector Magnetic Field Evolution of NOAA Active Region 11504 and the Ensuing CME Authors: James, Alexander; Green, Lucie; Valori, Gherardo; van Driel-Gesztelyi, Lidia; Baker, Deborah; Brooks, David; Palmerio, Erika Bibcode: 2016SPD....4730305J Altcode: Coronal mass ejections (CMEs) are eruptions of billions of tonnes of plasma from the Sun that drive the most severe space weather effects we observe. In order to be able to produce forecasts of space weather with lead times of the order of days, accurate predictions of the occurrence of CMEs must be developed. The eruptive active-region studied in this work (NOAA 11504) is complex, featuring fragmentation of penumbral magnetic field in the days prior to eruption, as well as rotation of the leading sunspot. SDO/HMI vector photospheric magnetic field measurements are utilised alongside SDO/AIA multi-wavelength extreme ultra-violet (EUV) observations to study the dynamics of the photospheric and coronal structures, as well as Hinode/EIS spectroscopic measurements, including elemental composition data. The EUV data show flare ribbons as well as coronal dimmings, which are used to infer the orientation of the erupting flux rope. This flux rope orientation is then compared to in situ measurements of the flux rope. The vector magnetic field data is used to determine the possible contributions the field fragmentation and sunspot rotation may have made to the formation of the flux rope and the triggering of the CME. Title: Division E Commission 10: Solar Activity Authors: Schrijver, Carolus J.; Fletcher, Lyndsay; van Driel-Gesztelyi, Lidia; Asai, Ayumi; Cally, Paul S.; Charbonneau, Paul; Gibson, Sarah E.; Gomez, Daniel; Hasan, Siraj S.; Veronig, Astrid M.; Yan, Yihua Bibcode: 2016IAUTA..29..245S Altcode: 2015arXiv151003348S After more than half a century of community support related to the science of ``solar activity'', IAU's Commission 10 was formally discontinued in 2015, to be succeeded by C.E2 with the same area of responsibility. On this occasion, we look back at the growth of the scientific disciplines involved around the world over almost a full century. Solar activity and fields of research looking into the related physics of the heliosphere continue to be vibrant and growing, with currently over 2,000 refereed publications appearing per year from over 4,000 unique authors, publishing in dozens of distinct journals and meeting in dozens of workshops and conferences each year. The size of the rapidly growing community and of the observational and computational data volumes, along with the multitude of connections into other branches of astrophysics, pose significant challenges; aspects of these challenges are beginning to be addressed through, among others, the development of new systems of literature reviews, machine-searchable archives for data and publications, and virtual observatories. As customary in these reports, we highlight some of the research topics that have seen particular interest over the most recent triennium, specifically active-region magnetic fields, coronal thermal structure, coronal seismology, flares and eruptions, and the variability of solar activity on long time scales. We close with a collection of developments, discoveries, and surprises that illustrate the range and dynamics of the discipline. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2016SoPh..291..337L Altcode: 2016SoPh..tmp...10L No abstract at ADS Title: Erratum to: The Magnetic Helicity Budget of a CME-Prolific Active Region Authors: Green, L. M.; López Fuentes, M.; Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.; Culhane, J. L. Bibcode: 2016SoPh..291..335G Altcode: 2015SoPh..tmp..179G No abstract at ADS Title: Preface Authors: Fletcher, L.; Heinzel, P.; van Driel-Gesztelyi, L.; Mandrini, C. H.; Fárník, F. Bibcode: 2015SoPh..290.3379F Altcode: 2015SoPh..tmp..168F No abstract at ADS Title: Preface: Probing the Sun Inside and Out Authors: Harra, Louise; Baker, Deborah; Howe, Rachel; Leibacher, John; van Driel-Gesztelyi, Lidia Bibcode: 2015SoPh..290.3091H Altcode: 2015SoPh..tmp..167H No abstract at ADS Title: Persistent Near-Surface Flow Structures from Local Helioseismology Authors: Howe, Rachel; Komm, R. W.; Baker, D.; Harra, L.; van Driel-Gesztelyi, L.; Bogart, R. S. Bibcode: 2015SoPh..290.3137H Altcode: 2015arXiv150706525H; 2015SoPh..tmp..115H Near-surface flows measured by the ring-diagram technique of local helioseismology show structures that persist over multiple rotations. We examine these phenomena using data from the Global Oscillation Network Group (GONG) and the Helioseismic and Magnetic Imager (HMI) and show that a correlation analysis of the structures can be used to estimate the rotation rate as a function of latitude, giving a result consistent with the near-surface rate from global helioseismology and slightly slower than that obtained from a similar analysis of the surface magnetic field strength. At latitudes of 60∘ and above, the HMI flow data reveal a strong signature of a two-sided zonal flow structure. This signature may be related to recent reports of "giant cells" in solar convection. Title: A Study of the Coronal Non-thermal Velocity in Polar Regions During the Rise from Solar Minimum to Solar Maximum in Cycle 24 Authors: Harra, L.; Baker, D.; Edwards, S. J.; Hara, H.; Howe, R.; van Driel-Gesztelyi, L. Bibcode: 2015SoPh..290.3203H Altcode: 2015SoPh..tmp....8H We explore the changes in coronal non-thermal velocity (Vnt) measurements at the poles from solar minimum to solar maximum using Hinode EUV Imaging Spectrometer data. We find that although the intensity in the corona at the poles does tend to increase with the cycle, there are no significant changes in the Vnt values. The locations of enhanced Vnt values measured do not always have a counterpart in intensity, and they are sometimes located in weak emission regions. Unipolar magnetic streams, created through diffusion of the following polarity of the decaying active regions, slowly progress towards the poles. These streams are expected to be related to magnetic nulls as locations that indicate an increased likelihood for magnetic reconnection to occur. Through global potential field source-surface modelling, we determine how the number of nulls varied during the cycle and find that those that lie at < 1.1 solar radii vary significantly. We search for a correlation between the variation of the magnetic nulls and the Vnt values, as it may be expected that with an increasing number of nulls, the Vnt values in the corona increase as well. There is no correlation with the Vnt values, however. This indicates that the magnetic structures that create the enhanced Vnt behaviour are small-scale features and hence not easily measurable at the poles. Because they do not change during the solar cycle, they are likely to be created by a local dynamo. The variation of the upper range of Vnt is reduced, which highlights that strongly dynamic behaviour is reduced as the solar maximum approaches. This is likely to be due to the reduced area of the polar coronal hole, which allows fewer opportunities for reconnection to occur between open and closed magnetic fields. Title: Source of a Prominent Poleward Surge During Solar Cycle 24 Authors: Yeates, A. R.; Baker, D.; van Driel-Gesztelyi, L. Bibcode: 2015SoPh..290.3189Y Altcode: 2015SoPh..tmp...18Y; 2015arXiv150204854Y As an observational case study, we consider the origin of a prominent poleward surge of leading polarity, visible in the magnetic butterfly diagram during Solar Cycle 24. A new technique is developed for assimilating individual regions of strong magnetic flux into a surface-flux transport model. By isolating the contribution of each of these regions, the model shows the surge to originate primarily in a single high-latitude activity group consisting of a bipolar active region present in Carrington Rotations 2104 - 05 (November 2010 - January 2011) and a multipolar active region in Rotations 2107 - 08 (February - April 2011). This group had a strong axial dipole moment opposed to Joy's law. On the other hand, the modelling suggests that the transient influence of this group on the butterfly diagram will not be matched by a large long-term contribution to the polar field because it is located at high latitude. This is in accordance with previous flux-transport models. Title: Evolution of Active Regions Authors: van Driel-Gesztelyi, Lidia; Green, Lucie May Bibcode: 2015LRSP...12....1V Altcode: The evolution of active regions (AR) from their emergence through their long decay process is of fundamental importance in solar physics. Since large-scale flux is generated by the deep-seated dynamo, the observed characteristics of flux emergence and that of the subsequent decay provide vital clues as well as boundary conditions for dynamo models. Throughout their evolution, ARs are centres of magnetic activity, with the level and type of activity phenomena being dependent on the evolutionary stage of the AR. As new flux emerges into a pre-existing magnetic environment, its evolution leads to re-configuration of small-and large-scale magnetic connectivities. The decay process of ARs spreads the once-concentrated magnetic flux over an ever-increasing area. Though most of the flux disappears through small-scale cancellation processes, it is the remnant of large-scale AR fields that is able to reverse the polarity of the poles and build up new polar fields. In this Living Review the emphasis is put on what we have learned from observations, which is put in the context of modelling and simulation efforts when interpreting them. For another, modelling-focused Living Review on the sub-surface evolution and emergence of magnetic flux see Fan (2009). In this first version we focus on the evolution of dominantly bipolar ARs. Title: Parallel Evolution of Quasi-separatrix Layers and Active Region Upflows Authors: Mandrini, C. H.; Baker, D.; Démoulin, P.; Cristiani, G. D.; van Driel-Gesztelyi, L.; Vargas Domínguez, S.; Nuevo, F. A.; Vásquez, A. M.; Pick, M. Bibcode: 2015ApJ...809...73M Altcode: 2015arXiv150701264M Persistent plasma upflows were observed with Hinode’s EUV Imaging Spectrometer (EIS) at the edges of active region (AR) 10978 as it crossed the solar disk. We analyze the evolution of the photospheric magnetic and velocity fields of the AR, model its coronal magnetic field, and compute the location of magnetic null-points and quasi-sepratrix layers (QSLs) searching for the origin of EIS upflows. Magnetic reconnection at the computed null points cannot explain all of the observed EIS upflow regions. However, EIS upflows and QSLs are found to evolve in parallel, both temporarily and spatially. Sections of two sets of QSLs, called outer and inner, are found associated to EIS upflow streams having different characteristics. The reconnection process in the outer QSLs is forced by a large-scale photospheric flow pattern, which is present in the AR for several days. We propose a scenario in which upflows are observed, provided that a large enough asymmetry in plasma pressure exists between the pre-reconnection loops and lasts as long as a photospheric forcing is at work. A similar mechanism operates in the inner QSLs; in this case, it is forced by the emergence and evolution of the bipoles between the two main AR polarities. Our findings provide strong support for the results from previous individual case studies investigating the role of magnetic reconnection at QSLs as the origin of the upflowing plasma. Furthermore, we propose that persistent reconnection along QSLs does not only drive the EIS upflows, but is also responsible for the continuous metric radio noise-storm observed in AR 10978 along its disk transit by the Nançay Radio Heliograph. Title: Active region plasma outflows as sources of slow/intermediate solar wind Authors: van Driel-Gesztelyi, Lidia M. Bibcode: 2015IAUGA..2257850V Altcode: L. van Driel-Gesztelyi (1,2,3), D. Baker (1), P. Démoulin (2), Culhane, J.L. (1), M.L. DeRosa (4) C.H. Mandrini (5,6), D.H. Brooks (7), A.N. Fazakerley (1), L.K. Harra (1), L. Zhao (7), T.H. Zurbuchen (7), F.A. Nuevo (5,6), A.M. Vásquez (5,6), G.D. Cristiani (5,6) M. Pick (2)1) UCL/MSSL, UK, (2) Paris Observatory, LESIA, CNRS, France, (3) Konkoly Observatory, Hungary, (4) Lockheed Martin Solar and Astrophysics Laboratory, USA, (5) IAFE, CONICET-UBA, Argentina (6) FCEN, UBA, Argentina (7) Dept. of Atmospheric, Oceanic and Earth Sciences, Univ. of Michigan, USAWe analyse plasma upflows of tens of km/s from the edges of solar active regions discovered by Hinode/EIS and investigate whether or not they become outflows, i.e. find their way into the solar wind. We analyse two magnetic configurations: bipolar and quadrupolar and find that the active region plasma may be directly channeled into the solar wind via interchange reconnection at a high-altitude null point above the active region especially when active regions are located besides coronal holes or in a more complex way via multiple reconnections even from under a closed helmet streamer. We relate the solar observations to in-situ slow/intermediate solar wind streams. Title: Division II: Commission 10: Solar Activity Authors: van Driel-Gesztelyi, Lidia; Scrijver, Karel J.; Klimchuk, James A.; Charbonneau, Paul; Fletcher, Lyndsay; Hasan, S. Sirajul; Hudson, Hugh S.; Kusano, Kanya; Mandrini, Cristina H.; Peter, Hardi; Vršnak, Bojan; Yan, Yihua Bibcode: 2015IAUTB..28..106V Altcode: The Business Meeting of Commission 10 was held as part of the Business Meeting of Division II (Sun and Heliosphere), chaired by Valentin Martínez-Pillet, the President of the Division. The President of Commission 10 (C10; Solar activity), Lidia van Driel-Gesztelyi, took the chair for the business meeting of C10. She summarised the activities of C10 over the triennium and the election of the incoming OC. Title: Interaction between CME and surrounding magnetic fields producing multiple flaring sites Authors: van Driel-Gesztelyi, Lidia M. Bibcode: 2015IAUGA..2257826V Altcode: L. van Driel-Gesztelyi (1,2,3), D. Baker (1), T. Török (4), E. Pariat (2), L.M. Green (1),D.R. Williams (1), J. Carlyle (1,5) G. Valori (1, 2), P. Démoulin (2), B. Kliem (1,7,8),D. Long (1), S.A. Matthews (1), J.-M. Malherbe (2)(1) UCL/MSSL, UK, (2) Paris Observatory, LESIA, CNRS, France, (3) Konkoly Observatory, Hungary, (4) Predictive Science, Dan Diego, USA, (5) Max Planck Inst., Göttingen, Germany, (6) INAF, Obs. Roma, Italy, (7) Potsdam Univ., Germany, (8) Yunnan Observatories, Kunming, ChinaAnalyzing Solar Dynamics Observatory (SDO) observations of the spectacular Coronal Mass Ejection eruption on 7 June 2011, we present evidence of coronal magnetic reconnection between the expanding magnetic structure of the CME and the magnetic fields of an adjacent active region (AR). The onset of reconnection first became apparent in the SDO/AIA images when filament plasma, originally contained within the erupting flux rope, was re-directed towards remote areas in the neighboring AR, tracing the change of large-scale magnetic connectivity. The observations are presented jointly with a topological analysis of the pre-eruption magnetic configuration, and a data-constrained numerical simulation of the three-AR complex, demonstrating the formation/intensification of current sheets along a pre-existing hyperbolic flux tube (HFT) at the interface between the CME and the neighboring AR, where a secondary flare ribbon was created. Reconnection across this current sheet resulted in the formation of new magnetic connections between the erupting magnetic structure and a neighboring AR about 200 Mm from the eruption site, in strong qualitative agreement with the observations. In addition, the CME temporarily created unusually dense plasma conditions around a reconnection region at high coronal altitudes, enabling us to observe emission resulting from it. We argue that this exceptional observation of a coronal brightening was directly observable at SDO/AIA wavelengths owing to the presence of down-flowing cool and dense (estimated to be of the order of 1010 cm-3) filament plasma in the vicinity of the reconnection region. Title: FIP Bias Evolution in a Decaying Active Region Authors: Baker, D.; Brooks, D. H.; Démoulin, P.; Yardley, S. L.; van Driel-Gesztelyi, L.; Long, D. M.; Green, L. M. Bibcode: 2015ApJ...802..104B Altcode: 2015arXiv150107397B Solar coronal plasma composition is typically characterized by first ionization potential (FIP) bias. Using spectra obtained by Hinode’s EUV Imaging Spectrometer instrument, we present a series of large-scale, spatially resolved composition maps of active region (AR)11389. The composition maps show how FIP bias evolves within the decaying AR during the period 2012 January 4-6. Globally, FIP bias decreases throughout the AR. We analyzed areas of significant plasma composition changes within the decaying AR and found that small-scale evolution in the photospheric magnetic field is closely linked to the FIP bias evolution observed in the corona. During the AR’s decay phase, small bipoles emerging within supergranular cells reconnect with the pre-existing AR field, creating a pathway along which photospheric and coronal plasmas can mix. The mixing timescales are shorter than those of plasma enrichment processes. Eruptive activity also results in shifting the FIP bias closer to photospheric in the affected areas. Finally, the FIP bias still remains dominantly coronal only in a part of the AR’s high-flux density core. We conclude that in the decay phase of an AR’s lifetime, the FIP bias is becoming increasingly modulated by episodes of small-scale flux emergence, i.e., decreasing the AR’s overall FIP bias. Our results show that magnetic field evolution plays an important role in compositional changes during AR development, revealing a more complex relationship than expected from previous well-known Skylab results showing that FIP bias increases almost linearly with age in young ARs. Title: JD3 - 3D Views of the Cycling Sun in Stellar Context: Overview Authors: van Driel-Gesztelyi, Lidia; Schrijver, Carolus J. Bibcode: 2015HiA....16...81V Altcode: We summarise the motivations and main results of the joint discussion ``3D Views of the Cycling Sun in Stellar Context'', and give credit to contributed talks and poster presentations, as due to the limited number of pages, this proceedings could only include contributions from the keynote speakers. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2015SoPh..290..657L Altcode: 2015SoPh..tmp...24L No abstract at ADS Title: Time Evolution of Force-Free Parameter and Free Magnetic Energy in Active Region NOAA 10365 Authors: Valori, G.; Romano, P.; Malanushenko, A.; Ermolli, I.; Giorgi, F.; Steed, K.; van Driel-Gesztelyi, L.; Zuccarello, F.; Malherbe, J. -M. Bibcode: 2015SoPh..290..491V Altcode: We describe the variation of the accumulated coronal helicity derived from the magnetic helicity flux through the photosphere in active region (AR) NOAA 10365, where several large flares and coronal mass ejections (CMEs) occurred. We used SOHO/MDI full-disk line-of-sight magnetograms to measure the helicity flux, and the integral of GOES X-ray flux as a proxy of the coronal energy variations due to flares or CMEs. Using the linear force-free field model, we transformed the accumulated helicity flux into a time sequence of the force-free parameter α accounting for flares or CMEs via the proxy derived from GOES observations. This method can be used to derive the value of α at different times during the AR evolution, and is a partial alternative to the commonly used match of field lines with EUV loops. By combining the accumulated helicity obtained from the observations with the linear force-free theory, we describe the main phases of the emergence process of the AR, and relate them temporally with the occurrence of flares or CMEs. Additionally, a comparison with the loop-matching method of fixing alpha at each time independently shows that the proposed method may be helpful in avoiding unrealistic or undetermined values of alpha that may originate from an insufficient quality of the image used to identify coronal loops at a given time. For the relative intensity of the considered events, the linear force-free field theory implies that there is a direct correlation between the released energy on the one hand and the product of the coronal helicity with the variation of α due to the event on the other. Therefore, the higher the value of the accumulated coronal helicity, the smaller the force-free parameter variation required to produce the same decrease in the free energy during the CMEs. Title: Solar Cycle Indices from the Photosphere to the Corona: Measurements and Underlying Physics Authors: Ermolli, Ilaria; Shibasaki, Kiyoto; Tlatov, Andrey; van Driel-Gesztelyi, Lidia Bibcode: 2015sac..book..105E Altcode: No abstract at ADS Title: New Eyes Looking at Solar Activity: Challenges for Theory and Simulations - Placing It into Context Authors: Pohjolainen, S.; Karlický, M.; van Driel-Gesztelyi, L.; Mandrini, C. H. Bibcode: 2015SoPh..290....1P Altcode: 2014SoPh..tmp..190P Solar Cycle 24 has opened a new era in solar radio physics as we now have instruments that can probe solar processes from submillimeter to kilometer waves. New and upgraded instruments provide data that enable studies of both energetic particles and thermal plasma, enhancing our knowledge of solar eruptions and acceleration and propagation of particles, through the solar chromosphere and corona and into the interplanetary space. In this Topical Issue we highlight the new observational capabilities and discuss the theoretical issues connected to solar radio emission and interplanetary radio physics. Title: Magnetic Helicity, Tilt, and Twist Authors: Pevtsov, Alexei A.; Berger, Mitchell A.; Nindos, Alexander; Norton, Aimee A.; van Driel-Gesztelyi, Lidia Bibcode: 2015sac..book..285P Altcode: No abstract at ADS Title: Solar Cycle Indices from the Photosphere to the Corona: Measurements and Underlying Physics Authors: Ermolli, Ilaria; Shibasaki, Kiyoto; Tlatov, Andrey; van Driel-Gesztelyi, Lidia Bibcode: 2014SSRv..186..105E Altcode: 2017arXiv170507054E; 2014SSRv..tmp...48E A variety of indices have been proposed in order to represent the many different observables modulated by the solar cycle. Most of these indices are highly correlated with each other owing to their intrinsic link with the solar magnetism and the dominant eleven year cycle, but their variations may differ in fine details, as well as on short- and long-term trends. In this paper we present an overview of the indices that are often employed to describe the many features of the solar cycle, moving from the ones referring to direct observations of the inner solar atmosphere, the photosphere and chromosphere, to those deriving from measurements of the transition region and solar corona. For each index, we summarize existing measurements and typical use, and for those that quantify physical observables, we describe the underlying physics. Title: Magnetic Helicity, Tilt, and Twist Authors: Pevtsov, Alexei A.; Berger, Mitchell A.; Nindos, Alexander; Norton, Aimee A.; van Driel-Gesztelyi, Lidia Bibcode: 2014SSRv..186..285P Altcode: Since its introduction to astro- and solar physics, the concept of helicity has proven to be useful in providing critical insights into physics of various processes from astrophysical dynamos, to magnetic reconnection and eruptive phenomena. Signature of helicity was also detected in many solar features, including orientation of solar active regions, or Joy's law. Here we provide a summary of both solar phenomena and consider mutual relationship and its importance for the evolution of solar magnetic fields. Title: How Can Active Region Plasma Escape into the Solar Wind from Below a Closed Helmet Streamer? Authors: Mandrini, C. H.; Nuevo, F. A.; Vásquez, A. M.; Démoulin, P.; van Driel-Gesztelyi, L.; Baker, D.; Culhane, J. L.; Cristiani, G. D.; Pick, M. Bibcode: 2014SoPh..289.4151M Altcode: 2014arXiv1409.7369M; 2014SoPh..tmp..115M Recent studies show that active-region (AR) upflowing plasma, observed by the EUV-Imaging Spectrometer (EIS) onboard Hinode, can gain access to open-field lines and be released into the solar wind (SW) via magnetic-interchange reconnection at magnetic null-points in pseudo-streamer configurations. When only one bipolar AR is present on the Sun and is fully covered by the separatrix of a streamer, such as AR 10978 in December 2007, it seems unlikely that the upflowing AR plasma can find its way into the slow SW. However, signatures of plasma with AR composition have been found at 1 AU by Culhane et al. (Solar Phys.289, 3799, 2014) that apparently originated west of AR 10978. We present a detailed topology analysis of AR 10978 and the surrounding large-scale corona based on a potential-field source-surface (PFSS) model. Our study shows that it is possible for the AR plasma to move around the streamer separatrix and be released into the SW via magnetic reconnection, which occurs in at least two main steps. We analyse data from the Nançay Radioheliograph (NRH) in a search for evidence of the chain of magnetic reconnections that we propose. We find a noise storm above the AR and several varying sources at 150.9 MHz. Their locations suggest that they might be associated with particles accelerated during the first-step reconnection process at a null point well outside of the AR. We find no evidence of the second reconnection step in the radio data, however. Our results demonstrate that even when it appears highly improbable for the AR plasma to reach the SW, indirect channels involving a sequence of reconnections can make it possible. Title: Extreme-ultraviolet Observations of Global Coronal Wave Rotation Authors: Attrill, G. D. R.; Long, D. M.; Green, L. M.; Harra, L. K.; van Driel-Gesztelyi, L. Bibcode: 2014ApJ...796...55A Altcode: We present evidence of global coronal wave rotation in EUV data from SOHO/EIT, STEREO/EUVI, and SDO/AIA. The sense of rotation is found to be consistent with the helicity of the source region (clockwise for positive helicity, anticlockwise for negative helicity), with the source regions hosting sigmoidal structures. We also study two coronal wave events observed by SDO/AIA where no clear rotation (or sigmoid) is observed. The selected events show supporting evidence that they all originate with flux rope eruptions. We make comparisons across this set of observations (both with and without clear sigmoidal structures). On examining the magnetic configuration of the source regions, we find that the nonrotation events possess a quadrupolar magnetic configuration. The coronal waves that do show a rotation originate from bipolar source regions. Title: Tracking Solar Active Region Outflow Plasma from Its Source to the Near-Earth Environment Authors: Culhane, J. L.; Brooks, D. H.; van Driel-Gesztelyi, L.; Démoulin, P.; Baker, D.; DeRosa, M. L.; Mandrini, C. H.; Zhao, L.; Zurbuchen, T. H. Bibcode: 2014SoPh..289.3799C Altcode: 2014SoPh..tmp...90C; 2014arXiv1405.2949C Seeking to establish whether active-region upflow material contributes to the slow solar wind, we examine in detail the plasma upflows from Active Region (AR) 10978, which crossed the Sun's disc in the interval 8 to 16 December 2007 during Carrington rotation (CR) 2064. In previous work, using data from the Hinode/EUV Imaging Spectrometer, upflow velocity evolution was extensively studied as the region crossed the disc, while a linear force-free-field magnetic extrapolation was used to confirm aspects of the velocity evolution and to establish the presence of quasi-separatrix layers at the upflow source areas. The plasma properties, temperature, density, and first ionisation potential bias [FIP-bias] were measured with the spectrometer during the disc passage of the active region. Global potential-field source-surface (PFSS) models showed that AR 10978 was completely covered by the closed field of a helmet streamer that is part of the streamer belt. Therefore it is not clear how any of the upflowing AR-associated plasma could reach the source surface at 2.5 R⊙ and contribute to the slow solar wind. However, a detailed examination of solar-wind in-situ data obtained by the Advanced Composition Explorer (ACE) spacecraft at the L1 point shows that increases in O7+/O6+, C6+/C5+, and Fe/O - a FIP-bias proxy - are present before the heliospheric current-sheet crossing. These increases, along with an accompanying reduction in proton velocity and an increase in density are characteristic of both AR and slow-solar-wind plasma. Finally, we describe a two-step reconnection process by which some of the upflowing plasma from the AR might reach the heliosphere. Title: The evolution of writhe in kink-unstable flux ropes and erupting filaments Authors: Török, T.; Kliem, B.; Berger, M. A.; Linton, M. G.; Démoulin, P.; van Driel-Gesztelyi, L. Bibcode: 2014PPCF...56f4012T Altcode: 2014arXiv1403.1565T The helical kink instability of a twisted magnetic flux tube has been suggested as a trigger mechanism for solar filament eruptions and coronal mass ejections (CMEs). In order to investigate if estimations of the pre-emptive twist can be obtained from observations of writhe in such events, we quantitatively analyze the conversion of twist into writhe in the course of the instability, using numerical simulations. We consider the line tied, cylindrically symmetric Gold-Hoyle flux rope model and measure the writhe using the formulae by Berger and Prior which express the quantity as a single integral in space. We find that the amount of twist converted into writhe does not simply scale with the initial flux rope twist, but depends mainly on the growth rates of the instability eigenmodes of higher longitudinal order than the basic mode. The saturation levels of the writhe, as well as the shapes of the kinked flux ropes, are very similar for considerable ranges of initial flux rope twists, which essentially precludes estimations of pre-eruptive twist from measurements of writhe. However, our simulations suggest an upper twist limit of ∼6π for the majority of filaments prior to their eruption. Title: Coronal Magnetic Reconnection Driven by CME Expansion—the 2011 June 7 Event Authors: van Driel-Gesztelyi, L.; Baker, D.; Török, T.; Pariat, E.; Green, L. M.; Williams, D. R.; Carlyle, J.; Valori, G.; Démoulin, P.; Kliem, B.; Long, D. M.; Matthews, S. A.; Malherbe, J. -M. Bibcode: 2014ApJ...788...85V Altcode: 2014arXiv1406.3153V Coronal mass ejections (CMEs) erupt and expand in a magnetically structured solar corona. Various indirect observational pieces of evidence have shown that the magnetic field of CMEs reconnects with surrounding magnetic fields, forming, e.g., dimming regions distant from the CME source regions. Analyzing Solar Dynamics Observatory (SDO) observations of the eruption from AR 11226 on 2011 June 7, we present the first direct evidence of coronal magnetic reconnection between the fields of two adjacent active regions during a CME. The observations are presented jointly with a data-constrained numerical simulation, demonstrating the formation/intensification of current sheets along a hyperbolic flux tube at the interface between the CME and the neighboring AR 11227. Reconnection resulted in the formation of new magnetic connections between the erupting magnetic structure from AR 11226 and the neighboring active region AR 11227 about 200 Mm from the eruption site. The onset of reconnection first becomes apparent in the SDO/AIA images when filament plasma, originally contained within the erupting flux rope, is redirected toward remote areas in AR 11227, tracing the change of large-scale magnetic connectivity. The location of the coronal reconnection region becomes bright and directly observable at SDO/AIA wavelengths, owing to the presence of down-flowing cool, dense (1010 cm-3) filament plasma in its vicinity. The high-density plasma around the reconnection region is heated to coronal temperatures, presumably by slow-mode shocks and Coulomb collisions. These results provide the first direct observational evidence that CMEs reconnect with surrounding magnetic structures, leading to a large-scale reconfiguration of the coronal magnetic field. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2014SoPh..289.1455L Altcode: 2014SoPh..tmp....6L No abstract at ADS Title: Investigating the Dynamics and Density Evolution of Returning Plasma Blobs from the 2011 June 7 Eruption Authors: Carlyle, Jack; Williams, David R.; van Driel-Gesztelyi, Lidia; Innes, Davina; Hillier, Andrew; Matthews, Sarah Bibcode: 2014ApJ...782...87C Altcode: 2014arXiv1401.4824C This work examines in-falling matter following an enormous coronal mass ejection on 2011 June 7. The material formed discrete concentrations, or blobs, in the corona and fell back to the surface, appearing as dark clouds against the bright corona. In this work we examined the density and dynamic evolution of these blobs in order to formally assess the intriguing morphology displayed throughout their descent. The blobs were studied in five wavelengths (94, 131, 171, 193, and 211 Å) using the Solar Dynamics Observatory Atmospheric Imaging Assembly, comparing background emission to attenuated emission as a function of wavelength to calculate column densities across the descent of four separate blobs. We found the material to have a column density of hydrogen of approximately 2 × 1019 cm-2, which is comparable with typical pre-eruption filament column densities. Repeated splitting of the returning material is seen in a manner consistent with the Rayleigh-Taylor instability. Furthermore, the observed distribution of density and its evolution is also a signature of this instability. By approximating the three-dimensional geometry (with data from STEREO-A), volumetric densities were found to be approximately 2 × 10-14 g cm-3, and this, along with observed dominant length scales of the instability, was used to infer a magnetic field of the order 1 G associated with the descending blobs. Title: Density evolution of in-falling prominence material from the 7th June 2011 CME Authors: Carlyle, Jack; Williams, David; van Driel-Gesztelyi, Lidia; Innes, Davina Bibcode: 2014IAUS..300..401C Altcode: This work investigates the density of in-falling prominence material following the 7 th June 2011 eruption. Both the evolution and the distribution of the density is analysed in five discreet ``blobs'' of material. The density appears to be remarkably uniform, both spatially within the blobs, and temporally over the course of the descent of each, although a slight concentration of material towards the leading edge is noted in some cases. Online material is available at bit.ly/jackblob Title: Spectroscopic measurements of EUV ejecta in a CME: a high-blueshift trailing thread Authors: Williams, David; Baker, Deborah; van Driel-Gesztelyi, Lidia; Green, Lucie Bibcode: 2014IAUS..300..464W Altcode: The mass of erupting prominence material can be inferred from the obscuration of emission behind this mass of cool plasma thanks to the rapid cadence of SDO/AIA images in the short EUV wavelength range (Carlyle et al. 2013, these proceedings). In comparing this approach with spectral observations from Hinode/EIS, to monitor contributions from emission seen around the erupting prominence material, we have found an intriguing component of blue-shifted emission, trailing the erupting prominence, with Doppler shifts on the order of 350 km s-1 in bright lines of both He ii and Fe xii. Title: FIP bias in a sigmoidal active region Authors: Baker, D.; Brooks, D. H.; Démoulin, P.; van Driel-Gesztelyi, Lidia; Green, L. M.; Steed, K.; Carlyle, J. Bibcode: 2014IAUS..300..222B Altcode: We investigate first ionization potential (FIP) bias levels in an anemone active region (AR) - coronal hole (CH) complex using an abundance map derived from Hinode/EIS spectra. The detailed, spatially resolved abundance map has a large field of view covering 359'' × 485''. Plasma with high FIP bias, or coronal abundances, is concentrated at the footpoints of the AR loops whereas the surrounding CH has a low FIP bias, ~1, i.e. photospheric abundances. A channel of low FIP bias is located along the AR's main polarity inversion line containing a filament where ongoing flux cancellation is observed, indicating a bald patch magnetic topology characteristic of a sigmoid/flux rope configuration. Title: Active region upflow plasma: its relation to small activity and the solar wind Authors: Mandrini, Cristina H.; Culhane, J. Leonard; Cristiani, Germán; Vásquez, Alberto; Van Driel-Gesztelyi, Lidia; Baker, Deborah; Pick, Monique; Demoulin, Pascal; Nuevo, Federico Bibcode: 2014cosp...40E1979M Altcode: Recent studies show that active region (AR) upflowing plasma, observed by the Hinode EUV Imaging Spectrometer (EIS), can gain access to open field lines and be released into the solar wind via magnetic interchange reconnection occurring below the source surface at magnetic null-points in pseudo-streamer configurations. When only one simple bipolar AR is present on the Sun and it is fully covered by the separatrix of a streamer, like AR 10978 on December 2007, it seems unlikely that the upflowing AR plasma could find its way into the slow solar wind. However, signatures of plasma with AR composition at 1 AU that appears to originate from the West of AR 10978 were recently found by Culhane and coworkers. We present a detailed topology analysis of AR 10978 based on a linear force-free magnetic field model at the AR scale, combined with a global PFSS model. This allows us, on one hand, to explain the variations observed in the upflows to the West of the AR as the result of magnetic reconnection at quasi-separatrix layers (QSLs). While at a global scale, we show that reconnection, occurring in at least two main steps, first at QSLs and later at a high-altitude coronal null-point, allows the AR plasma to get around the topological obstacle of the streamer separatrix and be released into the solar wind. Title: Magnetic reconnection driven by filament eruption in the 7 June 2011 event Authors: van Driel-Gesztelyi, L.; Baker, D.; Török, T.; Pariat, E.; Green, L. M.; Williams, D. R.; Carlyle, J.; Valori, G.; Démoulin, P.; Matthews, S. A.; Kliem, B.; Malherbe, J. -M. Bibcode: 2014IAUS..300..502V Altcode: During an unusually massive filament eruption on 7 June 2011, SDO/AIA imaged for the first time significant EUV emission around a magnetic reconnection region in the solar corona. The reconnection occurred between magnetic fields of the laterally expanding CME and a neighbouring active region. A pre-existing quasi-separatrix layer was activated in the process. This scenario is supported by data-constrained numerical simulations of the eruption. Observations show that dense cool filament plasma was re-directed and heated in situ, producing coronal-temperature emission around the reconnection region. These results provide the first direct observational evidence, supported by MHD simulations and magnetic modelling, that a large-scale re-configuration of the coronal magnetic field takes place during solar eruptions via the process of magnetic reconnection. Title: Initiation of Coronal Mass Ejections by Sunspot Rotation Authors: Valori, G.; Török, T.; Temmer, M.; Veronig, A. M.; van Driel-Gesztelyi, L.; Vršnak, B. Bibcode: 2014IAUS..300..201V Altcode: We report observations of a filament eruption, two-ribbon flare, and coronal mass ejection (CME) that occurred in Active Region NOAA 10898 on 6 July 2006. The filament was located South of a strong sunspot that dominated the region. In the evolution leading up to the eruption, and for some time after it, a counter-clockwise rotation of the sunspot of about 30 degrees was observed. We suggest that the rotation triggered the eruption by progressively expanding the magnetic field above the filament. To test this scenario, we study the effect of twisting the initially potential field overlying a pre-existing flux rope, using three-dimensional zero-β MHD simulations. We consider a magnetic configuration whose photospheric flux distribution and coronal structure is guided by the observations and a potential field extrapolation. We find that the twisting leads to the expansion of the overlying field. As a consequence of the progressively reduced magnetic tension, the flux rope quasi-statically adapts to the changed environmental field, rising slowly. Once the tension is sufficiently reduced, a distinct second phase of evolution occurs where the flux rope enters an unstable regime characterized by a strong acceleration. Our simulation thus suggests a new mechanism for the triggering of eruptions in the vicinity of rotating sunspots. Title: Magnetic Polarity Streams and Subsurface Flows Authors: Howe, R.; Baker, D.; Harra, L.; van Driel-Gesztelyi, L.; Komm, R.; Hill, F.; González Hernández, I. Bibcode: 2013ASPC..478..291H Altcode: An important feature of the solar cycle is the transport of unbalanced magnetic flux from active regions towards the poles, which eventually results in polarity reversal. This transport takes the form of distinct “polarity streams” that are visible in the magnetic butterfly diagram. We compare the poleward migration rate estimated from such streams to that derived from the subsurface meridional flows measured in helioseismic data from the GONG network since 2001, and find that the results are in reasonable agreement. Title: Plasma Composition in a Sigmoidal Anemone Active Region Authors: Baker, D.; Brooks, D. H.; Démoulin, P.; van Driel-Gesztelyi, L.; Green, L. M.; Steed, K.; Carlyle, J. Bibcode: 2013ApJ...778...69B Altcode: 2013arXiv1310.0999B Using spectra obtained by the EUV Imaging Spectrometer (EIS) instrument onboard Hinode, we present a detailed spatially resolved abundance map of an active region (AR)-coronal hole (CH) complex that covers an area of 359'' × 485''. The abundance map provides first ionization potential (FIP) bias levels in various coronal structures within the large EIS field of view. Overall, FIP bias in the small, relatively young AR is 2-3. This modest FIP bias is a consequence of the age of the AR, its weak heating, and its partial reconnection with the surrounding CH. Plasma with a coronal composition is concentrated at AR loop footpoints, close to where fractionation is believed to take place in the chromosphere. In the AR, we found a moderate positive correlation of FIP bias with nonthermal velocity and magnetic flux density, both of which are also strongest at the AR loop footpoints. Pathways of slightly enhanced FIP bias are traced along some of the loops connecting opposite polarities within the AR. We interpret the traces of enhanced FIP bias along these loops to be the beginning of fractionated plasma mixing in the loops. Low FIP bias in a sigmoidal channel above the AR's main polarity inversion line, where ongoing flux cancellation is taking place, provides new evidence of a bald patch magnetic topology of a sigmoid/flux rope configuration. Title: Initiation of Coronal Mass Ejections by Sunspot Rotation Authors: Török, T.; Temmer, M.; Valori, G.; Veronig, A. M.; van Driel-Gesztelyi, L.; Vršnak, B. Bibcode: 2013SoPh..286..453T Altcode: 2014arXiv1401.2922T We study a filament eruption, two-ribbon flare, and coronal mass ejection (CME) that occurred in NOAA Active Region 10898 on 6 July 2006. The filament was located South of a strong sunspot that dominated the region. In the evolution leading up to the eruption, and for some time after it, a counter-clockwise rotation of the sunspot of about 30 degrees was observed. We suggest that the rotation triggered the eruption by progressively expanding the magnetic field above the filament. To test this scenario, we study the effect of twisting the initially potential field overlying a pre-existing flux-rope, using three-dimensional zero-β MHD simulations. We first consider a relatively simple and symmetric system, and then study a more complex and asymmetric magnetic configuration, whose photospheric-flux distribution and coronal structure are guided by the observations and a potential field extrapolation. In both cases, we find that the twisting leads to the expansion of the overlying field. As a consequence of the progressively reduced magnetic tension, the flux-rope quasi-statically adapts to the changed environmental field, rising slowly. Once the tension is sufficiently reduced, a distinct second phase of evolution occurs where the flux-rope enters an unstable regime characterised by a strong acceleration. Our simulations thus suggest a new mechanism for the triggering of eruptions in the vicinity of rotating sunspots. Title: Observations and Modelling of the Inner Heliosphere: Preface and Tribute to the Late Dr. Andy Breen Authors: Bisi, M. M.; Harrison, R. A.; Lugaz, N.; van Driel-Gesztelyi, L.; Mandrini, C. H. Bibcode: 2013SoPh..285....1B Altcode: No abstract at ADS Title: Are subsurface flows and coronal holes related? Authors: Komm, R.; Howe, R.; González Hernández, I.; Harra, L.; Baker, D.; van Driel-Gesztelyi, L. Bibcode: 2013JPhCS.440a2022K Altcode: We study synoptic maps of solar subsurface flows covering six Carrington rotations (2050 to 2055). The subsurface flows are determined with a ring-diagram analysis of GONG high-resolution Doppler data. We identify the locations of coronal holes in synoptic maps of EUV images at 195Å from the EIT instrument and determine the characteristics of associated subsurface flows. We study two long-lived coronal holes that are present during this epoch. We find that large-scale patterns are present in the subsurface flows but appear to be unrelated to these coronal holes. The horizontal subsurface flows associated with the two long-lived coronal holes are weakly divergent (upflows) with small cyclonic vorticity. These flows are thus similar to subsurface flows of quiet regions with regard to the vertical flows and similar to flows of active regions with regard to vorticity. Title: Can we detect local helioseismic parameter shifts in coronal holes? Authors: Howe, R.; Haber, D. A.; Bogart, R. S.; Zharkov, S.; Baker, D.; Harra, L.; van Driel-Gesztelyi, L. Bibcode: 2013JPhCS.440a2019H Altcode: Changes in helioseismic mode parameters in active regions and across the solar disk are well documented, but local magnetic activity and geometric effects may not account for all of the scatter seen in the results. We use results from the Helioseismic and Magnetic Imager ring-diagram pipeline for Carrington rotation 2113 to look for differences in mode amplitude and frequency between coronal holes and other quiet-Sun regions. While we do not find a systematic difference, the results do suggest that the correlation between magnetic activity index and mode parameters shows less scatter in coronal hole regions than in general quiet Sun. Title: Subsurface flows associated with non-Joy oriented active regions: a case study Authors: González Hernández, Irene; Komm, Rudolf; van Driel-Gesztelyi, Lidia; Baker, Deborah; Harra, Louise; Howe, Rachel Bibcode: 2013JPhCS.440a2050G Altcode: Non-Joy oriented active regions (ARs) are a challenge for solar magnetic field modelers. Although significant deviations from Joy's law are relatively rare for simple bipolar ARs, understanding the causes of their particularity could be critical for the big picture of the solar dynamo. We explore the possibility of the sub-surface local dynamics being responsible for the significant rotation of these ARs. We apply the ring-diagram technique, a local helioseismology method, to infer the flows under and surrounding a non-Joy oriented AR and present the results of a case study in this paper. Title: Preface Authors: Gopalswamy, N.; Nieves-Chinchilla, T.; Hidalgo, M.; Zhang, J.; Riley, P.; van Driel-Gesztelyi, L.; Mandrini, C. H. Bibcode: 2013SoPh..284....1G Altcode: 2013arXiv1304.0085G This Topical Issue of Solar Physics, devoted to the study of flux-rope structure in coronal mass ejections (CMEs), is based on two Coordinated Data Analysis Workshops (CDAWs) held in 2010 (20 - 23 September in Dan Diego, California, USA) and 2011 (September 5-9 in Alcala, Spain). The primary purpose of the CDAWs was to address the question: Do all CMEs have flux rope structure? There are 18 papers om this topical issue, including this preface. Title: On the response of the solar atmosphere to small-scale magnetic flux emergence Authors: Vargas Dominguez, Santiago; van Driel-Gesztelyi, Lidia Bibcode: 2013EGUGA..15..925V Altcode: In this work we analyze data from the Hinode spacecraft targeting an emerging magnetic flux region. We focus on small-scale events identified by distinctive dark features in CaII H chromospheric filtergrams. Energy release at low chromospheric heights is detected to be boosted by the disappearance of the dark features after they reached their maximum size. The observed phenomena are explained as evidencing elementary flux emergence into the solar atmosphere. We are thus detecting granular-scale arch filament systems, that emerge and interact with pre-existing fields. The results give new insights on the resistive flux emergence scenario driving the configuration and evolution of solar active regions. We compare the results with emergence of individual magnetic loops seen in quiet sun regions. Title: The 3D Geometry of Active Region Upflows Deduced from Their Limb-to-Limb Evolution Authors: Démoulin, P.; Baker, D.; Mandrini, C. H.; van Driel-Gesztelyi, L. Bibcode: 2013SoPh..283..341D Altcode: 2012arXiv1211.5962D We analyze the evolution of coronal plasma upflows from the edges of AR 10978, which has the best limb-to-limb data coverage with Hinode's EUV Imaging Spectrometer (EIS). We find that the observed evolution is largely due to the solar rotation progressively changing the viewpoint of nearly stationary flows. From the systematic changes in the upflow regions as a function of distance from disc center, we deduce their 3D geometrical properties as inclination and angular spread in three coronal lines (Si VII, Fe XII, and Fe XV). In agreement with magnetic extrapolations, we find that the flows are thin, fan-like structures rooted in quasi separatrix layers (QSLs). The fans are tilted away from the AR center. The highest plasma velocities in these three spectral lines have similar magnitudes and their heights increase with temperature. The spatial location and extent of the upflow regions in the Si VII, Fe XII, and Fe XV lines are different owing to i) temperature stratification and ii) line of sight integration of the spectral profiles with significantly different backgrounds. We conclude that we sample the same flows at different temperatures. Further, we find that the evolution of line widths during the disc passage is compatible with a broad range of velocities in the flows. Everything considered, our results are compatible with the AR upflows originating from reconnections along QSLs between over-pressure AR loops and neighboring under-pressure loops. The flows are driven along magnetic field lines by a pressure gradient in a stratified atmosphere. Our interpretation of the above results is that, at any given time, we observe the superposition of flows created by successive reconnections, leading to a broad velocity distribution. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2013SoPh..283....1L Altcode: No abstract at ADS Title: Mass Estimates of Rapidly Moving Prominence Material from High-cadence EUV Images Authors: Williams, David R.; Baker, Deborah; van Driel-Gesztelyi, Lidia Bibcode: 2013ApJ...764..165W Altcode: 2013arXiv1301.4271W We present a new method for determining the column density of erupting filament material using state-of-the-art multi-wavelength imaging data. Much of the prior work on filament/prominence structure can be divided between studies that use a polychromatic approach with targeted campaign observations and those that use synoptic observations, frequently in only one or two wavelengths. The superior time resolution, sensitivity, and near-synchronicity of data from the Solar Dynamics Observatory's Advanced Imaging Assembly allow us to combine these two techniques using photoionization continuum opacity to determine the spatial distribution of hydrogen in filament material. We apply the combined techniques to SDO/AIA observations of a filament that erupted during the spectacular coronal mass ejection on 2011 June 7. The resulting "polychromatic opacity imaging" method offers a powerful way to track partially ionized gas as it erupts through the solar atmosphere on a regular basis, without the need for coordinated observations, thereby readily offering regular, realistic mass-distribution estimates for models of these erupting structures. Title: Tracking Solar Active Region Outflow Plasma from its Source to the near-Earth Environment Authors: Culhane, J. L.; Brooks, D.; Zurbuchen, T.; van Driel-Gesztelyi, L.; Fazakerley, A. N.; DeRosa, M. L. Bibcode: 2012AGUFMSH53A2255C Altcode: In a recent study of persistent active region outflow from AR 10978 in the period 10 - 15, December, 2007, Brooks and Warren (2011), using the Hinode EUV Imaging Spectrometer (EIS) instrument showed the presence of a strong low-FIP element enhancement in the outflowing plasma that was replicated three days later in the in-situ solar wind measurements made by the ACE/SWICS instrument. In the present work, we examine the outflowing plasma properties (Te, Ne, v, abundances) as a function of time in greater detail as AR 10978 passes the Earth-Sun line. The structure of the magnetic field above the two outflow regions - E and W of the AR, is also examined. Following an assessment of the relevant magnetic structures between Sun and Earth, the properties of the solar wind plasma arriving at ACE approximately three days later are measured and compared with those of the outflowing AR plasma. The relationship of these measurements to the in-situ magnetic field observed by the ACE magnetometer is also studied. Finally the role of persistent AR outflows in contributing to the slow solar wind is assessed. 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: Magnetic Topology of Active Regions and Coronal Holes: Implications for Coronal Outflows and the Solar Wind Authors: van Driel-Gesztelyi, L.; Culhane, J. L.; Baker, D.; Démoulin, P.; Mandrini, C. H.; DeRosa, M. L.; Rouillard, A. P.; Opitz, A.; Stenborg, G.; Vourlidas, A.; Brooks, D. H. Bibcode: 2012SoPh..281..237V Altcode: 2012SoPh..tmp..228V During 2 - 18 January 2008 a pair of low-latitude opposite-polarity coronal holes (CHs) were observed on the Sun with two active regions (ARs) and the heliospheric plasma sheet located between them. We use the Hinode/EUV Imaging Spectrometer (EIS) to locate AR-related outflows and measure their velocities. Solar-Terrestrial Relations Observatory (STEREO) imaging is also employed, as are the Advanced Composition Explorer (ACE) in-situ observations, to assess the resulting impacts on the solar wind (SW) properties. Magnetic-field extrapolations of the two ARs confirm that AR plasma outflows observed with EIS are co-spatial with quasi-separatrix layer locations, including the separatrix of a null point. Global potential-field source-surface modeling indicates that field lines in the vicinity of the null point extend up to the source surface, enabling a part of the EIS plasma upflows access to the SW. We find that similar upflow properties are also observed within closed-field regions that do not reach the source surface. We conclude that some of plasma upflows observed with EIS remain confined along closed coronal loops, but that a fraction of the plasma may be released into the slow SW. This suggests that ARs bordering coronal holes can contribute to the slow SW. Analyzing the in-situ data, we propose that the type of slow SW present depends on whether the AR is fully or partially enclosed by an overlying streamer. Title: Preface Authors: Nakariakov, V. M.; Georgoulis, M. K.; Poedts, S.; van Driel-Gesztelyi, L.; Mandrini, C. H.; Leibacher, J. Bibcode: 2012SoPh..280..295N Altcode: 2012SoPh..tmp..226N No abstract at ADS Title: Identifying the Main Driver of Active Region Outflows Authors: Baker, D.; van Driel-Gesztelyi, L.; Mandrini, C. H.; Démoulin, P.; Murray, M. J. Bibcode: 2012ASPC..454..425B Altcode: Hinode's EUV Imaging Spectrometer (EIS) has discovered ubiquitous outflows of a few to 50 km s-1 from active regions (ARs). The characteristics of these outflows are very curious in that they are most prominent at the AR boundary and appear over monopolar magnetic areas. They are linked to strong non-thermal line broadening and are stronger in hotter EUV lines. The outflows persist for at least several days. Whereas red-shifted down flows observed in AR closed loops are well understood, to date there is no general consensus for the mechanism(s) driving blue-shifted AR-related outflows. We use Hinode EIS and X-Ray Telescope observations of AR 10942 coupled with magnetic modeling to demonstrate for the first time that the outflows originate from specific locations of the magnetic topology where field lines display strong gradients of magnetic connectivity, namely quasi-separatrix layers (QSLs), or in the limit of infinitely thin QSLs, separatrices. The strongest AR outflows were found to be in the vicinity of QSL sections located over areas of strong magnetic field. We argue that magnetic reconnection at QSLs, separating closed field lines of the AR and either large-scale externally connected or ‘open’ field lines, is a viable mechanism for driving AR outflows which are potentially sources of the slow solar wind. In fact, magnetic reconnection along QSLs (including separatricies) is the first theory to explain the most puzzling characteristics of the outflows, namely their occurrence over monopolar areas at the periphery of ARs and their longevity. Title: Does Magnetic Helicity Affect Active Region Evolution and Energetics? Authors: Wallace, A. J.; Green, L. M.; Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.; Matthews, S. A. Bibcode: 2012ASPC..454..281W Altcode: The purpose of this investigation is to determine whether there is a difference between the evolution of an active region with additional new flux emergence if the new flux has either the same or the opposite sign of magnetic helicity from the active region. Of these two scenarios, the one that produces the most energetics is still a topic for debate. We present a study of two active regions following the emergence of a bipole, one with the same and one with the opposite sign of helicity from the active region. We discover that while there is less flaring in the mixed helicity active region the EUV flux normalised to the magnetic field is three times higher than that of the same helicity active region. We propose that reconnection is more likely to occur between opposite helicity structures and thus, the energy can never build up to the levels required for flaring. Title: The Slow Solar Wind: From Formation on the Sun to the Earth Authors: Harra, L. K.; Fazakerley, A. N.; van Driel-Gesztelyi, L. Bibcode: 2012ASPC..454..421H Altcode: Hinode has discovered a potential source of slow solar wind at the edges of active regions with the X-ray Telescope (XRT) and EUV Imaging spectrometer (EIS) on board Hinode e.g. Sakao et al. (2007), Harra et al. (2008), Doschek et al. (2008). These upflows are long-lasting and exist at the edges of most active regions. In this conference paper we first discuss the onset of the upflows. This is related to newly emerged magnetic flux into an active region. Next we discuss whether the flows that we see on the surface of the Sun actually are transported to the Earth in the slow solar wind. To do this we looked at a number of different examples over a Carrington rotation and tracked the response in the solar wind as measured by the ACE spacecraft at L1. We found that there is a significant enhancement of the in situ solar wind speed for active regions located close to a coronal hole. Title: Parallels among the ``music scores'' of solar cycles, space weather and Earth's climate Authors: Kolláth, Zoltán; Oláh, Katalin; van Driel-Gesztelyi, Lidia Bibcode: 2012IAUS..286..423K Altcode: Solar variability and its effects on the physical variability of our (space) environment produces complex signals. In the indicators of solar activity at least four independent cyclic components can be identified, all of them with temporal variations in their timescales.

Time-frequency distributions (see Kolláth & Oláh 2009) are perfect tools to disclose the ``music scores'' in these complex time series. Special features in the time-frequency distributions, like frequency splitting, or modulations on different timescales provide clues, which can reveal similar trends among different indices like sunspot numbers, interplanetary magnetic field strength in the Earth's neighborhood and climate data.

On the pseudo-Wigner Distribution (PWD) the frequency splitting of all the three main components (the Gleissberg and Schwabe cycles, and an ~5.5 year signal originating from cycle asymmetry, i.e. the Waldmeier effect) can be identified as a ``bubble'' shaped structure after 1950. The same frequency splitting feature can also be found in the heliospheric magnetic field data and the microwave radio flux. Title: Modulated stellar and solar cycles: parallels and differences Authors: Oláh, K.; van Driel-Gesztelyi, L.; Strassmeier, K. G. Bibcode: 2012IAUS..286..279O Altcode: We present examples of activity cycle timescales on different types of stars from lowmass dwarfs to more massive giants, with wide-ranging rotation rates, and compare the observed cyclicities to the irradiance based solar cycle and its modulations. Using annual spectral solar irradiance in wavelength bands typical for stellar observations reconstructed by Shapiro et al. (2011), a direct comparison can be made between cycle timescales and amplitudes derived for the Sun and the stars. We show that cycles on multiple timescales, known to be present in solar activity, also show up on stars when the dataset is long enough to allow recognition. The cycle lengths are not fixed, but evolve - gradually during some periods but there are also changes on short timescales. In case the activity is dominated by spots, i.e., by cooler surface features, the star is redder when fainter, whereas other type of activity make the stars bluer when the activity is higher. We found the Sun to be a member of the former group, based on reconstructed spectral irradiance data by Shapiro et al. (2011). Title: Magnetic topology, coronal outflows, and the solar wind Authors: Mandrini, Cristina H.; Culhane, J. Leonard; Vourlidas, Angelos; Demoulin, Pascal; Stenborg, Guillermo; Opitz, Andrea; Rouillard, Alexis; Van Driel-Gesztelyi, Lidia; Baker, Deborah; DeRosa, Marc; Brooks, David Bibcode: 2012cosp...39.1173M Altcode: 2012cosp.meet.1173M During 2-18 January 2008 a pair of low-latitude opposite polarity coronal holes were observed on the Sun flanked by two ARs with the heliospheric plasma sheet between them. Hinode/EUV Imaging Telescope (EIS) is used to locate AR-related outflows and measure their velocities. The Advanced Composition Explorer (ACE) in-situ observations are employed to assess the resulting impacts on the interplanetary solar wind (SW). Magnetic field extrapolations of the two ARs confirm that AR plasma outflows observed with EIS are co-spatial with quasi-separatrix layer locations, including the separatrix of a null point. Global potential field source-surface modeling indicates that field lines in the vicinity of the null point extend up to the source-surface, enabling a part of the EIS plasma upflows access to the SW. Similar upflow magnitude is also observed within closed field regions. Though part of the plasma upflows observed with EIS remain confined along closed coronal loops, a subset of them are indeed able to make their imprint in the slow SW, making ARs bordering coronal holes a slow SW contributor. Title: CME-related changes in line-of-sight magnetic field strength in dimming regions observed by Hinode on 14 December 2006 Authors: Pedram, Ehsan; Matthews, Sarah A.; Van Driel-Gesztelyi, Lidia Bibcode: 2012cosp...39.1479P Altcode: 2012cosp.meet.1479P No abstract at ADS Title: Are subsurface flows and coronal holes related? Authors: Komm, Rudolf W.; Howe, R.; González Hernández, I.; Harra, L.; Baker, D.; van Driel-Gesztelyi, L. Bibcode: 2012shin.confE.120K Altcode: We study subsurface flows measured with a ring-diagram analysis of GONG high-resolution Doppler data. In previous studies, we have focused on the relationship between active regions and subsurface flows associated with them. Synoptic subsurface flow maps show also large-scale patterns that are not obviously associated with active regions. It is unknown whether these flow patterns correlate with any large-scale magnetic features. Here, we explore whether there is a relationship between subsurface flows and coronal features. We analyze synoptic maps of subsurface flows covering 18 Carrington rotations during the years 2006 and 2007 (CR 2038-2055). Long-lived coronal holes are present during this epoch at low latitudes, which are accessible by ring-diagram analysis of GONG data. We compare subsurface flow maps with EIT synoptic maps of EUV images at 195A (http://sun.stanford.edu/synop/EIT/) and will present the latest results. Title: The Creation of Outflowing Plasma in the Corona at Emerging Flux Regions: Comparing Observations and Simulations Authors: Harra, L. K.; Archontis, V.; Pedram, E.; Hood, A. W.; Shelton, D. L.; van Driel-Gesztelyi, L. Bibcode: 2012SoPh..278...47H Altcode: In this paper we analyse the flux emergence that occurred in the following polarity area of an active region on 1 - 2 December 2006. Observations have revealed the existence of fast outflows at the edge of the emerging flux region. We have performed 3-D numerical simulations to study the mechanisms responsible for these flows. The results indicate that these outflows are reconnection jets or pressure-driven outflows, depending on the relative orientation of the magnetic fields in contact (i.e. the emerging flux and the active region's field which is favourable for reconnection on the west side and nearly parallel with the pre-existing field on the east side of the emerging flux). In the observations, the flows are larger on the west side until late in the flux emergence, when the reverse is true. The simulations show that the flows are faster on the west side, but do not show the east flows increasing with time. There is an asymmetry in the expansion of the emerging flux region, which is also seen in the observations. The west side of the emerging flux region expands faster into the corona than the other side. In the simulations, efficient magnetic reconnection occurs on the west side, with new loops being created containing strong downflows that are clearly seen in the observations. On the other side, the simulations show strong compression as the dominant mechanism for the generation of flows. There is evidence of these flows in the observations, but the flows are stronger than the simulations predict at the later stages. There could be additional small-angle reconnection that adds to the flows from the compression, as well as reconnection occurring in larger loops that lie across the whole active region. Title: Nonlinear Force-Free Extrapolation of Emerging Flux with a Global Twist and Serpentine Fine Structures Authors: Valori, G.; Green, L. M.; Démoulin, P.; Vargas Domínguez, S.; van Driel-Gesztelyi, L.; Wallace, A.; Baker, D.; Fuhrmann, M. Bibcode: 2012SoPh..278...73V Altcode: We study the flux emergence process in NOAA active region 11024, between 29 June and 7 July 2009, by means of multi-wavelength observations and nonlinear force-free extrapolation. The main aim is to extend previous investigations by combining, as much as possible, high spatial resolution observations to test our present understanding of small-scale (undulatory) flux emergence, whilst putting these small-scale events in the context of the global evolution of the active region. The combination of these techniques allows us to follow the whole process, from the first appearance of the bipolar axial field on the east limb, until the buoyancy instability could set in and raise the main body of the twisted flux tube through the photosphere, forming magnetic tongues and signatures of serpentine field, until the simplification of the magnetic structure into a main bipole by the time the active region reaches the west limb. At the crucial time of the main emergence phase high spatial resolution spectropolarimetric measurements of the photospheric field are employed to reconstruct the three-dimensional structure of the nonlinear force-free coronal field, which is then used to test the current understanding of flux emergence processes. In particular, knowledge of the coronal connectivity confirms the identity of the magnetic tongues as seen in their photospheric signatures, and it exemplifies how the twisted flux, which is emerging on small scales in the form of a sea-serpent, is subsequently rearranged by reconnection into the large-scale field of the active region. In this way, the multi-wavelength observations combined with a nonlinear force-free extrapolation provide a coherent picture of the emergence process of small-scale magnetic bipoles, which subsequently reconnect to form a large-scale structure in the corona. Title: Preface Authors: Green, L. M.; Sakurai, T.; van Driel-Gesztelyi, L. Bibcode: 2012SoPh..278....1G Altcode: No abstract at ADS Title: Granular-Scale Elementary Flux Emergence Episodes in a Solar Active Region Authors: Vargas Domínguez, S.; van Driel-Gesztelyi, L.; Bellot Rubio, L. R. Bibcode: 2012SoPh..278...99V Altcode: 2012SoPh..tmp..259F; 2012arXiv1203.6428V We analyse data from Hinode spacecraft taken over two 54-minute periods during the emergence of AR 11024. We focus on small-scale portions within the observed solar active region and discover the appearance of very distinctive small-scale and short-lived dark features in Ca II H chromospheric filtergrams and Stokes I images. The features appear in regions with close-to-zero longitudinal magnetic field, and are observed to increase in length before they eventually disappear. Energy release in the low chromospheric line is detected while the dark features are fading. Three complete series of these events are detected with remarkably similar properties, i.e. lifetime of ≈ 12 min, maximum length and area of 2 - 4 Mm and 1.6 - 4 Mm2, respectively, and all with associated brightenings. In time series of magnetograms a diverging bipolar configuration is observed accompanying the appearance of the dark features and the brightenings. The observed phenomena are explained as evidencing elementary flux emergence in the solar atmosphere, i.e. small-scale arch filament systems rising up from the photosphere to the lower chromosphere with a length scale of a few solar granules. Brightenings are explained as being the signatures of chromospheric heating triggered by reconnection of the rising loops (once they have reached chromospheric heights) with pre-existing magnetic fields, as well as being due to reconnection/cancellation events in U-loop segments of emerging serpentine fields. The characteristic length scale, area and lifetime of these elementary flux emergence events agree well with those of the serpentine field observed in emerging active regions. We study the temporal evolution and dynamics of the events and compare them with the emergence of magnetic loops detected in quiet Sun regions and serpentine flux emergence signatures in active regions. The physical processes of the emergence of granular-scale magnetic loops seem to be the same in the quiet Sun and active regions. The difference is the reduced chromospheric emission in the quiet Sun attributed to the fact that loops are emerging in a region of lower ambient magnetic field density, making interactions and reconnection less likely to occur. Incorporating the novel features of granular-scale flux emergence presented in this study, we advance the scenario for serpentine flux emergence. Title: On Signatures of Twisted Magnetic Flux Tube Emergence Authors: Vargas Domínguez, S.; MacTaggart, D.; Green, L.; van Driel-Gesztelyi, L.; Hood, A. W. Bibcode: 2012SoPh..278...33V Altcode: 2011arXiv1105.0758V Recent studies of NOAA active region 10953, by Okamoto et al. (Astrophys. J. Lett.673, 215, 2008; Astrophys. J.697, 913, 2009), have interpreted photospheric observations of changing widths of the polarities and reversal of the horizontal magnetic field component as signatures of the emergence of a twisted flux tube within the active region and along its internal polarity inversion line (PIL). A filament is observed along the PIL and the active region is assumed to have an arcade structure. To investigate this scenario, MacTaggart and Hood (Astrophys. J. Lett.716, 219, 2010) constructed a dynamic flux emergence model of a twisted cylinder emerging into an overlying arcade. The photospheric signatures observed by Okamoto et al. (2008, 2009) are present in the model although their underlying physical mechanisms differ. The model also produces two additional signatures that can be verified by the observations. The first is an increase in the unsigned magnetic flux in the photosphere at either side of the PIL. The second is the behaviour of characteristic photospheric flow profiles associated with twisted flux tube emergence. We look for these two signatures in AR 10953 and find negative results for the emergence of a twisted flux tube along the PIL. Instead, we interpret the photospheric behaviour along the PIL to be indicative of photospheric magnetic cancellation driven by flows from the dominant sunspot. Although we argue against flux emergence within this particular region, the work demonstrates the important relationship between theory and observations for the successful discovery and interpretation of signatures of flux emergence. Title: Division II: Sun and Heliosphere Authors: Martínez Pillet, Valentín; Klimchuk, James A.; Melrose, Donald B.; Cauzzi, Gianna; van Driel-Gesztelyi, Lidia; Gopalswamy, Natchimuthuk; Kosovichev, Alexander; Mann, Ingrid; Schrijver, Carolus J. Bibcode: 2012IAUTA..28...61M Altcode: 2012IAUTA..28...61P The solar activity cycle entered a prolonged quiet phase that started in 2008 and ended in 2010. This minimum lasted for a year longer than expected and all activity proxies, as measured from Earth and from Space, reached minimum values never observed before (de Toma, 2012). The number of spotless days from 2006 to 2009 totals 800, the largest ever recorded in modern times. Solar irradiance was at historic minimums. The interplanetary magnetic field was measured at values as low as 2.9 nT and the cosmic rays were observed at records-high. While rumors spread that the Sun could be entering a grand minimum quiet phase (such as the Maunder minimum of the XVII century), activity took over in 2010 and we are now well into Solar Cycle 24 (albeit, probably, a low intensity cycle), approaching towards a maximum due by mid 2013. In addition to bringing us the possibility to observe a quiet state of the Sun and of the Heliosphere that was previously not recorded with modern instruments, the Sun has also shown us how little we know about the dynamo mechanism that drives its activity as all solar cycle predictions failed to see this extended minimum coming. Title: Commission 10: Solar Activity Authors: van Driel-Gesztelyi, Lidia; Schrijver, Carolus J.; Klimchuk, James A.; Charbonneau, Paul; Fletcher, Lyndsay; Hasan, S. Sirajul; Hudson, Hugh S.; Kusano, Kanya; Mandrini, Cristina H.; Peter, Hardi; Vršnak, Bojan; Yan, Yihua Bibcode: 2012IAUTA..28...69V Altcode: Commission 10 of the International Astronomical Union has more than 650 members who study a wide range of activity phenomena produced by our nearest star, the Sun. Solar activity is intrinsically related to solar magnetic fields and encompasses events from the smallest energy releases (nano- or even picoflares) to the largest eruptions in the Solar System, coronal mass ejections (CMEs), which propagate into the Heliosphere reaching the Earth and beyond. Solar activity is manifested in the appearance of sunspot groups or active regions, which are the principal sources of activity phenomena from the emergence of their magnetic flux through their dispersion and decay. The period 2008-2009 saw an unanticipated extended solar cycle minimum and unprecedentedly weak polar-cap and heliospheric field. Associated with that was the 2009 historical maximum in galactic cosmic rays flux since measurements begun in the middle of the 20th Century. Since then Cycle 24 has re-started solar activity producing some spectacular eruptions observed with a fleet of spacecraft and ground-based facilities. In the last triennium major advances in our knowledge and understanding of solar activity were due to continuing success of space missions as SOHO, Hinode, RHESSI and the twin STEREO spacecraft, further enriched by the breathtaking images of the solar atmosphere produced by the Solar Dynamic Observatory (SDO) launched on 11 February 2010 in the framework of NASA's Living with a Star program. In August 2012, at the time of the IAU General Assembly in Beijing when the mandate of this Commission ends, we will be in the unique position to have for the first time a full 3-D view of the Sun and solar activity phenomena provided by the twin STEREO missions about 120 degrees behind and ahead of Earth and other spacecraft around the Earth and ground-based observatories. These new observational insights are continuously posing new questions, inspiring and advancing theoretical analysis and modelling, improving our understanding of the physics underlying magnetic activity phenomena. Commission 10 reports on a vigorously evolving field of research produced by a large community. The number of refereed publications containing `Sun', `heliosphere', or a synonym in their abstracts continued the steady growth seen over the preceding decades, reaching about 2000 in the years 2008-2010, with a total of close to 4000 unique authors. This report, however, has its limitations and it is inherently incomplete, as it was prepared jointly by the members of the Organising Committee of Commission 10 (see the names of the primary contributors to the sections indicated in parentheses) reflecting their fields of expertise and interest. Nevertheless, we believe that it is a representative sample of significant new results obtained during the last triennium in the field of solar activity. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2012SoPh..276....1L Altcode: No abstract at ADS Title: Forecasting a CME by Spectroscopic Precursor? Authors: Baker, D.; van Driel-Gesztelyi, L.; Green, L. M. Bibcode: 2012SoPh..276..219B Altcode: Multi-temperature plasma flows resulting from the interaction between a mature active region (AR) inside an equatorial coronal hole (CH) are investigated. Outflow velocities observed by Hinode EIS ranged from a few to 13 km s−1 for three days at the AR's eastern and western edges. However, on the fourth day, velocities intensified up to 20 km s−1 at the AR's western footpoint about six hours prior to a CME. 3D MHD numerical simulations of the observed magnetic configuration of the AR-CH complex showed that the expansion of the mature AR's loops drives persistent outflows along the neighboring CH field (Murray et al. in Solar Phys.261, 253, 2010). Based on these simulations, intensification of outflows observed pre-eruption on the AR's western side where same-polarity AR and CH field interface, is interpreted to be the result of the expansion of a sigmoidal AR, in particular, a flux rope containing a filament that provides stronger compression of the neighboring CH field on this side of the AR. Intensification of outflows in the AR is proposed as a new type of CME precursor. Title: Preface Authors: Marqué, C.; Nindos, A.; van Driel-Gesztelyi, L.; Mandrini, C. H. Bibcode: 2012esrs.book....1M Altcode: No abstract at ADS Title: The Sun-Earth Connection near Solar Minimum: Placing it into Context Authors: Bisi, Mario M.; Thompson, Barbara J.; Emery, Barbara A.; Gibson, Sarah E.; Leibacher, John; van Driel-Gesztelyi, Lidia Bibcode: 2011SoPh..274....1B Altcode: No abstract at ADS Title: Preface Authors: Marqué, C.; Nindos, A.; van Driel-Gesztelyi, L.; Mandrini, C. H. Bibcode: 2011SoPh..273..307M Altcode: 2011SoPh..tmp..385M No abstract at ADS Title: Coronal Jets, Magnetic Topologies, and the Production of Interplanetary Electron Streams Authors: Li, C.; Matthews, S. A.; van Driel-Gesztelyi, L.; Sun, J.; Owen, C. J. Bibcode: 2011ApJ...735...43L Altcode: 2013arXiv1305.5602L We investigate the acceleration source of the impulsive solar energetic particle (SEP) events on 2007 January 24. Combining the in situ electron measurements and remote-sensing solar observations, as well as the calculated magnetic fields obtained from a potential-field source-surface model, we demonstrate that the jets associated with the hard X-ray flares and type-III radio bursts, rather than the slow and partial coronal mass ejections, are closely related to the production of interplanetary electron streams. The jets, originated from the well-connected active region (AR 10939) whose magnetic polarity structure favors the eruption, are observed to be forming in a coronal site, extending to a few solar radii, and having a good temporal correlation with the electron solar release. The open-field lines near the jet site are rooted in a negative polarity, along which energetic particles escape from the flaring AR to the near-Earth space, consistent with the in situ electron pitch angle distribution. The analysis enables us to propose a coronal magnetic topology relating the impulsive SEP events to their solar source. Title: Twisted Flux Tube Emergence Evidenced in Longitudinal Magnetograms: Magnetic Tongues Authors: Luoni, M. L.; Démoulin, P.; Mandrini, C. H.; van Driel-Gesztelyi, L. Bibcode: 2011SoPh..270...45L Altcode: 2011SoPh..tmp...66L Bipolar active regions (ARs) are thought to be formed by twisted flux tubes, as the presence of such twist is theoretically required for a cohesive rise through the whole convective zone. We use longitudinal magnetograms to demonstrate that a clear signature of a global magnetic twist is present, particularly, during the emergence phase when the AR is forming in a much weaker pre-existing magnetic field environment. The twist is characterised by the presence of elongated polarities, called "magnetic tongues", which originate from the azimuthal magnetic field component. The tongues first extend in size before retracting when the maximum magnetic flux is reached. This implies an apparent rotation of the magnetic bipole. Using a simple half-torus model of an emerging twisted flux tube having a uniform twist profile, we derive how the direction of the polarity inversion line and the elongation of the tongues depend on the global twist in the flux rope. Using a sample of 40 ARs, we verify that the helicity sign, determined from the magnetic polarity distribution pattern, is consistent with the sign derived from the photospheric helicity flux computed from magnetogram time series, as well as from other proxies such as sheared coronal loops, sigmoids, flare ribbons and/or the associated magnetic cloud observed in situ at 1 AU. The evolution of the tongues observed in emerging ARs is also closely similar to the evolution found in recent MHD numerical simulations. We also found that the elongation of the tongue formed by the leading magnetic polarity is significantly larger than that of the following polarity. This newly discovered asymmetry is consistent with an asymmetric Ω-loop emergence, trailing the solar rotation, which was proposed earlier to explain other asymmetries in bipolar ARs. Title: Pulsed Flows Along a Cusp Structure Observed with SDO/AIA Authors: Thompson, Barbara; Démoulin, P.; Mandrini, C.; Mays, M.; Ofman, L.; Van Driel-Gesztelyi, L.; Viall, N. Bibcode: 2011SPD....42.2117T Altcode: 2011BAAS..43S.2117T We present observations of a cusp-shaped structure that formed after a flare and coronal mass ejection on 14 February 2011. Throughout the evolution of the cusp structure, blob features up to a few Mm in size were observed flowing along the legs and stalk of the cusp at projected speeds ranging from 50 to 150 km/sec. Around two dozen blob features, on order of 1 - 3 minutes apart, were tracked in multiple AIA EUV wavelengths. The blobs flowed outward (away from the Sun) along the cusp stalk, and most of the observed speeds were either constant or decelerating. We attempt to reconstruct the 3-D magnetic field of the evolving structure, discuss the possible drivers of the flows (including pulsed reconnection and tearing mode instability), and compare the observations to studies of pulsed reconnection and blob flows in the solar wind and the Earth's magnetosphere. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2011SoPh..269....1L Altcode: 2011SoPh..tmp...21L No abstract at ADS Title: Pre-Flare Flows in the Corona Authors: Wallace, A. J.; Harra, L. K.; van Driel-Gesztelyi, L.; Green, L. M.; Matthews, S. A. Bibcode: 2010SoPh..267..361W Altcode: 2010SoPh..tmp..223W; 2010SoPh..tmp..199W Solar flares take place in regions of strong magnetic fields and are generally accepted to be the result of a resistive instability leading to magnetic reconnection. When new flux emerges into a pre-existing active region it can act as a flare and coronal mass ejection trigger. In this study we observed active region 10955 after the emergence of small-scale additional flux at the magnetic inversion line. We found that flaring began when additional positive flux levels exceeded 1.38×1020 Mx (maxwell), approximately 7 h after the initial flux emergence. We focussed on the pre-flare activity of one B-class flare that occurred on the following day. The earliest indication of activity was a rise in the non-thermal velocity one hour before the flare. 40 min before flaring began, brightenings and pre-flare flows were observed along two loop systems in the corona, involving the new flux and the pre-existing active region loops. We discuss the possibility that reconnection between the new flux and pre-existing loops before the flare drives the flows by either generating slow mode magnetoacoustic waves or a pressure gradient between the newly reconnected loops. The subsequent B-class flare originated from fast reconnection of the same loop systems as the pre-flare flows. Title: Temporal evolution and spatial variation of the solar wind from multi-spacecraft measurements Authors: Opitz, A.; Wurz, P.; Fedorov, A.; Sauvaud, J.; Luhmann, J. G.; Riley, P.; Szego, K.; Russell, C. T.; Galvin, A. B.; Rouillard, A. P.; Vourlidas, A.; van Driel-Gesztelyi, L. Bibcode: 2010AGUFMSH33C..07O Altcode: We study the temporal evolution and the spatial variation of the solar wind on different scales. The analyzed multi-spacecraft (STEREO, VEX, SOHO, MEX, and other spacecraft) measurements were obtained between 2007 and 2010 during solar minimum in the inner heliosphere. We derived the temporal and spatial variability of the different solar wind parameters (proton bulk velocity, electron core density, etc). These results support prediction of the solar wind parameters for different heliospheric positions and help to derive its validity range. In order to explain occasional deviations from the nominal solar wind evolution we use imaging data and modeling results. Title: Solar Physics Memoir Series Reinstituted Authors: Cliver, Ed; van Driel-Gesztelyi, Lidia Bibcode: 2010SoPh..267..233C Altcode: 2010SoPh..tmp..194C No abstract at ADS Title: Observational and numerical study of the 25 July 2004 event Authors: Soenen, A.; Jacobs, C.; Poedts, S.; van Driel-Gesztelyi, L.; Torok, T.; Lapenta, G. Bibcode: 2010AGUFMSH23B1843S Altcode: We study the 25 July 2004 event. By analyzing SOHO EIT images we establish a basic understanding of the large-scale interaction going on during this event. Magnetic reconnection between the expanding CME and the Southern hemispheric active regions (AR) will connect the leading polarities of the two ARs, lead to brightening in the ARs and transport CME field line foot points to distant ARs (observable as dimming at the foot points).We reproduce the large scale interactions during this event using three-dimensional magneto-hydrodynamic (MHD) simulations. We superimpose a magnetic source region that resembles the SOHO MDI images on a basic wind model. By emerging new flux at the centre of this region we initiate a Coronal Mass Ejection (CME). We monitor the evolution of this CME and study its interaction with the source region. Title: Preface Authors: Bisi, M. M.; Breen, A. R.; van Driel-Gesztelyi, L.; Mandrini, C. H. Bibcode: 2010SoPh..265....1B Altcode: 2010SoPh..tmp..143B No abstract at ADS Title: Revealing the Fine Structure of Coronal Dimmings and Associated Flows with Hinode/EIS. Implications for Understanding the Source Regions of Sustained Outflow Following CMEs Authors: Attrill, G. D. R.; Harra, L. K.; van Driel-Gesztelyi, L.; Wills-Davey, M. J. Bibcode: 2010SoPh..264..119A Altcode: 2010SoPh..tmp...80A We study two CME events on 13 and 14 December 2006 that were associated with large-scale dimmings. We study the eruptions from pre-event on 11 December through the recovery on 15 December, using a combination of Hinode/EIS, SOHO/EIT, SOHO/MDI, and MLSO Hα data. The GOES X-class flares obscured the core dimmings, but secondary dimmings developed remote from the active region (AR) in both events. The secondary dimmings are found to be formed by a removal of bright coronal material from loops in the plage region to the East of the AR. Using Hinode/EIS data, we find that the outflows associated with the coronal-dimming regions are highly structured. The concentrated outflows are located at the footpoints of coronal loops (which exist before, and are re-established after, the eruptions), and these are correlated with regions of positive magnetic elements. Comparative study of the Hinode/EIS and SOHO/EIT data shows that the reduction in outflow velocity is consistent with the recovery in intensity of the studied regions. We find that concentrated downflows develop during the recovery phase of the dimmings and are also correlated with the same positive magnetic elements that were previously related to outflows. Title: Division II: Sun and Heliosphere Authors: Melrose, Donald B.; Martinez Pillet, Valentin; Webb, David F.; Bougeret, Jean-Louis; Klimchuk, James A.; Kosovichev, Alexander; van Driel-Gesztelyi, Lidia; von Steiger, Rudolf Bibcode: 2010IAUTB..27..146M Altcode: This report is on activities of the Division at the General Assembly in Rio de Janeiro. Summaries of scientific activities over the past triennium have been published in Transactions A, see Melrose et al. (2008), Klimchuk et al. (2008), Martinez Pillet et al. (2008) and Bougeret et al. (2008). The business meeting of the three Commissions were incorporated into the business meeting of the Division. This report is based in part on minutes of the business meeting, provided by the Secretary of the Division, Lidia van Driel-Gesztelyi, and it also includes reports provided by the Presidents of the Commissions (C10, C12, C49) and of the Working Groups (WGs) in the Division. Title: Solar Observation Target Identification Convention for use in Solar Physics Authors: Leibacher, John; Sakurai, Takashi; Schrijver, Carolus J.; van Driel-Gesztelyi, Lidia Bibcode: 2010SoPh..263....1L Altcode: 2010SoPh..263....1.; 2010SoPh..tmp...71. We strongly encourage the use of a standardized target identification to be included in pub- lications on solar events. The primary purpose is to enable the automated identification of publications on the same event, or on other related events, in the on-line literature by search engines such as the Astrophysics Data System (ADS). The convention does not aim to categorize or classify events, but is limited specifically to the identification of regions in space and intervals in time within which events occur. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2010SoPh..262....1L Altcode: 2010SoPh..tmp...18L No abstract at ADS Title: Outflows at the Edges of an Active Region in a Coronal Hole: A Signature of Active Region Expansion? Authors: Murray, M. J.; Baker, D.; van Driel-Gesztelyi, L.; Sun, J. Bibcode: 2010SoPh..261..253M Altcode: 2009arXiv0912.1246M Outflows of plasma at the edges of active regions surrounded by quiet Sun are now a common observation with the Hinode satellite. While there is observational evidence to suggest that the outflows are originating in the magnetic field surrounding the active regions, there is no conclusive evidence that reveals how they are driven. Motivated by observations of outflows at the periphery of a mature active region embedded in a coronal hole, we have used a three-dimensional simulation to emulate the active region's development in order to investigate the origin and driver of these outflows. We find that outflows are accelerated from a site in the coronal hole magnetic field immediately surrounding the active region and are channelled along the coronal hole field as they rise through the atmosphere. The plasma is accelerated simply as a result of the active region expanding horizontally as it develops. Many of the characteristics of the outflows generated in the simulation are consistent with those of observed outflows: velocities up to 45 km s−1, properties akin to the coronal hole, proximity to the active region's draining loops, expansion with height, and projection over monopolar photospheric magnetic concentrations. Although the horizontal expansion occurs as a consequence of the active region's development in the simulation, expansion is also a general feature of established active regions. Hence, it is entirely possible and plausible that the expansion acceleration mechanism displayed in the simulation is occurring in active regions on the Sun and, in addition to reconnection, is driving the outflows observed at their edges. Title: EIT/Coronal waves and coronal dimming: a holistic approach Authors: van Driel-Gesztelyi, Lidia Bibcode: 2010cosp...38.1793V Altcode: 2010cosp.meet.1793V If EIT waves were simple, they would not be such interesting and divisive a subject. I will argue that one of the main reasons for the persistent elusiveness of their interpretation is that they are due to a composite of causes, which include MHD waves, compression of coronal plasma by the expanding CME as well as magnetic reconnection between the CME and surrounding magnetic structures. There is not one single cause which on itself could explain all the observed characteristics. I will show that magnetic reconnection between the CME and other magnetic structures is responsible for some of the transient brightenings which show up along the diffuse bright EIT wave front, as evidenced by long-lived (¿ 1 h) dimming regions which form in their wake. CME-driven dynamic reconnection provides a natural explanation for the formation of widespread secondary dimming regions, indicating that large portions of the Sun become constituents of the CME. This implies that the extent of the secondary dimming matches the final angular width of the CME, as observed. I will review observations and MHD simulations supporting the composite nature of the causes of EIT waves, and will argue in favour of a holistic approach, which will not diminish their interest, but rather bring us closer to understanding them. Title: Magnetic reconnection along QSLs -a major driver of active region outflows Authors: Baker, Deborah; van Driel-Gesztelyi, Lidia; Mandrini, Cristina H.; Demoulin, Pascal Bibcode: 2010cosp...38.2926B Altcode: 2010cosp.meet.2926B The relationship between quasi-separatrix layers (QSLs), or in the limit of infinitely thin QSLs, separatrices, and various activity phenomena has been explored in many different solar magnetic configurations across all scales in recent years. In the absence of magnetic nulls, fast reconnec-tion along QSLs, which are specific locations in the magnetic topology where field lines display strong gradients of magnetic connectivity, was identified as the main physical process at the origin of flares. Recently, it was shown that fast (tens of km/s) persistent hot plasma upflows in active regions (ARs) can also be linked to locations of QSLs. It is likely that these upflows that occur at the edges of ARs over unipolar magnetic field concentrations are accelerated by magnetic reconnection along QSLs. We will show multi-temperature spectral scan observations from Hinode's EIS combined with magnetic modeling of QSLs in two ARs observed on 20-21 February 2007 and 11 January 2008. The latter AR is observed and modeled when it is in the vicinity of the solar central meridian where there are no projection effects, thereby eliminating ambiguity linking the origin of multi-temperature observations of AR upflows to QSLs. We use the Potential Source Surface Model to look for open field lines in the vicinity of upflows and QSL locations in order to demonstrate whether these upflows become outflows and can contribute to the solar wind. Title: Interacting active regions and coronal holes: implications for coronal outflows and solar wind structure Authors: Culhane, J. Leonard; Baker, Deborah; Rouillard, Alexis; van Driel-Gesztelyi, Lidia Bibcode: 2010cosp...38.1863C Altcode: 2010cosp.meet.1863C When active regions are adjacent to coronal holes a variety of magnetic field interactions can result. These may include the interchange reconnection between the closed active region (AR) fields and the open field of the coronal hole (CH), leading to fast and significant evolution of coronal hole boundaries. Outcomes may include variability of -or changes in, active region-associated hot plasma outflows seen with Hinode/EIS and the modulation of the solar wind flows on open field lines. Depending on their relative positions on the Sun, the AR-CH interactions may have their signatures embedded in co-rotating interaction regions (CIRs) or rarefaction regions. During two intervals -8/11 January, 2008 and 7/9 December, 2008, we have made observations with Hinode of two oppositely configured situations on the Sun. For 8/11 January, the coronal hole leads the active region while for 7/9 December the order is reversed. The Hinode EIS instrument is used to locate outflows and measure their velocities while the XRT is used to image the source regions, including the variable nature of the outflows. SOHO EIT imaging is used to follow the longer-term evolution of the coronal hole boundaries while MDI is used to observe changes in the magnetic field. STEREO imaging and in-situ data are also employed -as are ACE observations, to assess the resulting impacts on interplanetary solar wind structures. The contrasting behaviour that results from magnetic interactions in the two different configurations is described and assessed. Title: Coronal magnetic topology and the solar source of beam-like electron events Authors: Li, Chuan; van Driel-Gesztelyi, Lidia; Matthews, Sarah A.; Sun, Jian; Mandrini, Cristina H.; Owen, Christopher Bibcode: 2010cosp...38.2986L Altcode: 2010cosp.meet.2986L More and more evidence indicates a strong correlation between impulsive solar energetic particle (SEP) events and the magnetic reconnections in the vicinity of flaring active regions (ARs). However, it is still not clear how they are related to each other. We present the investigation of the AR 10939, which produced two B-class flares, accompanied by narrow coronal mass ejections (CMEs)and successive beam-like electron events on 24 January 2007. Using in situ electron observations from ACE/EPAM and WIND/3DP, and imaging data from Hinode/EIS, RHESSI, and TRACE, coupled with magnetic modeling, we could establish the correlations of the coronal magnetic topologies, jet activities, and the accelerations of impulsive electrons. Title: Characteristics of the Nonthermal Velocity Signature Observed in the Impulsive Phase of the 2007 May 19 Flare Authors: Hara, H.; Watanabe, T.; Bone, L. A.; Culhane, J. L.; van Driel-Gesztelyi, L.; Young, P. R. Bibcode: 2009ASPC..415..459H Altcode: The Hinode EUV Imaging Spectrometer (EIS) observed a long duration flare with a weak impulsive phase that appears to conform to the standard two-ribbon flare reconnection model. EIS scanned the flare site during the impulsive phase and observed Fe XXIII and Fe XXIV line emission that closely followed the flare hard X-ray emission while the line profiles showed significant non-thermal broadening. We suggest that a shock originating at the reconnection site which sweeps up and heats the coronal plasma can account for our observations. Title: Intensification of Plasma Upflows in an Active Region---Coronal Hole Complex: A CME Precursor Authors: Baker, D.; van Driel-Gesztelyi, L.; Murray, M. J.; Green, L. M.; Török, T.; Sun, J. Bibcode: 2009ASPC..415...75B Altcode: We investigate the plasma flows resulting from the interaction between a mature active region (AR) and a surrounding equatorial coronal hole (CH) observed by Hinode's EIS and XRT from 15 to 18 October 2007. For 3 days, EIS velocity maps showed upflows at the AR's eastern and western edges that were consistently between 5 and 10 km s-1, whereas downflows of up to 30 km s-1 were seen in AR loops. However, on 18 October, velocity profiles of hotter coronal lines revealed intensification in upflow velocities of up to 18 km s-1 at the AR's western footpoints 4.5 hours prior to a CME. We compare the AR's plasma flows with 2.5D MHD numerical simulations of the magnetic configuration, which show that expansion of the mature AR's loops drives upflows along the neighboring CH field. Further, the intensification of upflows observed on the AR's western side prior to a CME is interpreted to be the result of the expansion of a flux rope containing a filament further compressing the neighboring CH field. Title: Solar Physics Publication Ethics Policies Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2009SoPh..260....1L Altcode: No abstract at ADS Title: Magnetic Reconnection along Quasi-separatrix Layers as a Driver of Ubiquitous Active Region Outflows Authors: Baker, D.; van Driel-Gesztelyi, L.; Mandrini, C. H.; Démoulin, P.; Murray, M. J. Bibcode: 2009ApJ...705..926B Altcode: 2009arXiv0909.4738B Hinode's EUV Imaging Spectrometer (EIS) has discovered ubiquitous outflows of a few to 50 km s-1 from active regions (ARs). These outflows are most prominent at the AR boundary and appear over monopolar magnetic areas. They are linked to strong non-thermal line broadening and are stronger in hotter EUV lines. The outflows persist for at least several days. Using Hinode EIS and X-Ray Telescope observations of AR 10942 coupled with magnetic modeling, we demonstrate that the outflows originate from specific locations of the magnetic topology where field lines display strong gradients of magnetic connectivity, namely quasi-separatrix layers (QSLs), or in the limit of infinitely thin QSLs, separatrices. We found the strongest AR outflows to be in the vicinity of QSL sections located over areas of strong magnetic field. We argue that magnetic reconnection at QSLs separating closed field lines of the AR and either large-scale externally connected or "open" field lines is a viable mechanism for driving AR outflows which are likely sources of the slow solar wind. Title: Signatures of interchange reconnection: STEREO, ACE and Hinode observations combined Authors: Baker, D.; Rouillard, A. P.; van Driel-Gesztelyi, L.; Démoulin, P.; Harra, L. K.; Lavraud, B.; Davies, J. A.; Opitz, A.; Luhmann, J. G.; Sauvaud, J. -A.; Galvin, A. B. Bibcode: 2009AnGeo..27.3883B Altcode: 2009arXiv0909.5624B Combining STEREO, ACE and Hinode observations has presented an opportunity to follow a filament eruption and coronal mass ejection (CME) on 17 October 2007 from an active region (AR) inside a coronal hole (CH) into the heliosphere. This particular combination of "open" and closed magnetic topologies provides an ideal scenario for interchange reconnection to take place. With Hinode and STEREO data we were able to identify the emergence time and type of structure seen in the in-situ data four days later. On the 21st, ACE observed in-situ the passage of an ICME with "open" magnetic topology. The magnetic field configuration of the source, a mature AR located inside an equatorial CH, has important implications for the solar and interplanetary signatures of the eruption. We interpret the formation of an "anemone" structure of the erupting AR and the passage in-situ of the ICME being disconnected at one leg, as manifested by uni-directional suprathermal electron flux in the ICME, to be a direct result of interchange reconnection between closed loops of the CME originating from the AR and "open" field lines of the surrounding CH. Title: Formation, Interaction and Merger of an Active Region and a Quiescent Filament Prior to Their Eruption on 19 May 2007 Authors: Bone, L. A.; van Driel-Gesztelyi, L.; Culhane, J. L.; Aulanier, G.; Liewer, P. Bibcode: 2009SoPh..259...31B Altcode: We report observations of the formation of two filaments - one active and one quiescent, and their subsequent interactions prior to eruption. The active region filament appeared on 17 May 2007, followed by the quiescent filament about 24 hours later. In the 26 hour interval preceding the eruption, which occurred at around 12:50 UT on 19 May 2007, we see the two filaments attempting to merge and filament material is repeatedly heated suggesting magnetic reconnection. The filament structure is observed to become increasingly dynamic preceding the eruption with two small hard X-ray sources seen close to the active part of the filament at around 01:38 UT on 19 May 2007 during one of the activity episodes. The final eruption on 19 May at about 12:51 UT involves a complex CME structure, a flare and a coronal wave. A magnetic cloud is observed near Earth by the STEREO-B and WIND spacecraft about 2.7 days later. Here we describe the behaviour of the two filaments in the period prior to the eruption and assess the nature of their dynamic interactions. Title: Preface Authors: Christian, Eric R.; Kaiser, Michael L.; Kucera, Therese A.; St. Cyr, O. C.; van Driel-Gesztelyi, Lidia; Mandrini, Cristina H. Bibcode: 2009SoPh..256....1C Altcode: No abstract at ADS Title: Stereoscopic Analysis of the 19 May 2007 Erupting Filament Authors: Liewer, P. C.; De Jong, E. M.; Hall, J. R.; Howard, R. A.; Thompson, W. T.; Culhane, J. L.; Bone, L.; van Driel-Gesztelyi, L. Bibcode: 2009SoPh..256...57L Altcode: 2009arXiv0904.1055L A filament eruption, accompanied by a B9.5 flare, coronal dimming, and an EUV wave, was observed by the Solar TERrestrial Relations Observatory (STEREO) on 19 May 2007, beginning at about 13:00 UT. Here, we use observations from the SECCHI/EUVI telescopes and other solar observations to analyze the behavior and geometry of the filament before and during the eruption. At this time, STEREO A and B were separated by about 8.5°, sufficient to determine the three-dimensional structure of the filament using stereoscopy. The filament could be followed in SECCHI/EUVI 304 Å stereoscopic data from about 12 hours before to about 2 hours after the eruption, allowing us to determine the 3D trajectory of the erupting filament. From the 3D reconstructions of the filament and the chromospheric ribbons in the early stage of the eruption, simultaneous heating of both the rising filamentary material and the chromosphere directly below is observed, consistent with an eruption resulting from magnetic reconnection below the filament. Comparisons of the filament during eruption in 304 Å and Hα show that when it becomes emissive in He II, it tends to disappear in Hα , indicating that the disappearance probably results from heating or motion, not loss, of filamentary material. Title: Magnetic reconnection and energy release on the Sun and solar-like stars Authors: van Driel-Gesztelyi, Lidia Bibcode: 2009IAUS..259..191V Altcode: Magnetic reconnection is thought to play an important role in liberating free energy stored in stressed magnetic fields. The consequences vary from undetectable nanoflares to huge flares, which have signatures over a wide wavelength range, depending on e.g. magnetic topology, free energy content, total flux, and magnetic flux density of the structures involved. Events of small energy release, which are thought to be the most numerous, are one of the key factors in the existence of a hot corona in the Sun and solar-like stars. The majority of large flares are ejective, i.e. involve the expulsion of large quantities of mass and magnetic field from the star. Since magnetic reconnection requires small length-scales, which are well below the spatial resolution limits of even the solar observations, we cannot directly observe magnetic reconnection happening. However, there is a plethora of indirect evidences from X-rays to radio observations of magnetic reconnection. I discuss key observational signatures of flares on the Sun and solar-paradigm stellar flares and describe models emphasizing synergy between observations and theory. Title: Magnetic Flux Emergence, Activity, Eruptions and Magnetic Clouds: Following Magnetic Field from the Sun to the Heliosphere Authors: van Driel-Gesztelyi, L.; Culhane, J. L. Bibcode: 2009SSRv..144..351V Altcode: 2008SSRv..tmp..185V We present an overview of how the principal physical properties of magnetic flux which emerges from the toroidal fields in the tachocline through the turbulent convection zone to the solar surface are linked to solar activity events, emphasizing the effects of magnetic field evolution and interaction with other magnetic structures on the latter. We compare the results of different approaches using various magnetic observables to evaluate the probability of flare and coronal mass ejection (CME) activity and forecast eruptive activity on the short term (i.e. days). Then, after a brief overview of the observed properties of CMEs and their theoretical models, we discuss the ejecta properties and describe some typical magnetic and composition characteristics of magnetic clouds (MCs) and interplanetary CMEs (ICMEs). We review some individual examples to clarify the link between eruptions from the Sun and the properties of the resulting ejecta. The importance of a synthetic approach to solar and interplanetary magnetic fields and activity is emphasized. Title: The link between CME-associated dimmings and interplanetary magnetic clouds Authors: Mandrini, Cristina H.; Nakwacki, María S.; Attrill, Gemma; van Driel-Gesztelyi, Lidia; Dasso, Sergio; Démoulin, Pascal Bibcode: 2009IAUS..257..265M Altcode: Coronal dimmings often develop in the vicinity of erupting magnetic configurations. It has been suggested that they mark the location of the footpoints of ejected flux ropes and, thus, their magnetic flux can be used as a proxy for the ejected flux. If so, this quantity can be compared to the flux in the associated interplanetary magnetic cloud (MC) to find clues about the origin of the ejected flux rope. In the context of this interpretation, we present several events for which we have done a comparative solar-interplanetary analysis. We combine SOHO/Extreme Ultraviolet Imaging Telescope (EIT) data and Michelson Doppler Imager (MDI) magnetic maps to identify and measure the flux in the dimmed regions. We model the associated MCs and compute their magnetic flux using in situ observations. We find that the magnetic fluxes in the dimmings and MCs are compatible in some events; though this is not the case for large-scale and intense eruptions that occur in regions that are not isolated from others. We conclude that, in these particular cases, a fraction of the dimmed regions can be formed by reconnection between the erupting field and the surrounding magnetic structures, via a stepping process that can also explain other CME associated events. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2009SoPh..255....1L Altcode: No abstract at ADS Title: Division II: Sun and Heliosphere Authors: Melrose, Donald B.; Martínez Pillet, Valentin; Webb, David F.; van Driel-Gesztelyi, Lidia; Bougeret, Jean-Louis; Klimchuk, James A.; Kosovichev, Alexander; von Steiger, Rudolf Bibcode: 2009IAUTA..27...73M Altcode: Division II of the IAU provides a forum for astronomers and astrophysicists studying a wide range of phenomena related to the structure, radiation and activity of the Sun, and its interaction with the Earth and the rest of the solar system. Division II encompasses three Commissions, 10, 12 and 49, and four Working Groups. Title: Commission 10: Solar Activity Authors: Klimchuk, James A.; van Driel-Gesztelyi, Lidia; Schrijver, Carolus J.; Melrose, Donald B.; Fletcher, Lyndsay; Gopalswamy, Natchimuthuk; Harrison, Richard A.; Mandrini, Cristina H.; Peter, Hardi; Tsuneta, Saku; Vršnak, Bojan; Wang, Jing-Xiu Bibcode: 2009IAUTA..27...79K Altcode: 2008arXiv0809.1444K Commission 10 deals with solar activity in all of its forms, ranging from the smallest nanoflares to the largest coronal mass ejections. This report reviews scientific progress over the roughly two-year period ending in the middle of 2008. This has been an exciting time in solar physics, highlighted by the launches of the Hinode and STEREO missions late in 2006. The report is reasonably comprehensive, though it is far from exhaustive. Limited space prevents the inclusion of many significant results. The report is divided into the following sections: Photosphere and chromosphere; Transition region; Corona and coronal heating; Coronal jets; flares; Coronal mass ejection initiation; Global coronal waves and shocks; Coronal dimming; The link between low coronal CME signatures and magnetic clouds; Coronal mass ejections in the heliosphere; and Coronal mass ejections and space weather. Primary authorship is indicated at the beginning of each section. Title: Simulations of emerging flux in a coronal hole: oscillatory reconnection Authors: Murray, M. J.; van Driel-Gesztelyi, L.; Baker, D. Bibcode: 2009A&A...494..329M Altcode: Context: Observations and simulations show that reconnection will take place when a flux tube emerges into a coronal hole, which is characterised by magnetic fieldlines “open” towards interplanetary space. Although the mechanism by which reconnection is initiated has been thoroughly studied, the long-term evolution of this reconnecting magnetic system remains unreported.
Aims: We aim to understand the long-term evolution of the reconnecting flux tube and coronal hole system and, in particular, to ascertain whether it can reach an equilibrium state in which all reconnection has ceased. By determining the evolution in this particular scenario, we aim to be able to select a subset from the broad spectrum of reconnecting systems, which will undergo the same progression to equilibrium.
Methods: Using a 2.5-dimensional numerical magnetohydrodynamic (MHD) code, we evolve a simple stratified atmospheric domain, which is endowed with a vertical magnetic field, representing the interior of a coronal hole, and a horizontal buoyant flux tube that is placed near the bottom of the domain. To investigate the long-term evolution of the system, we continue to study the domain long after the flux tube has emerged and reconnection has commenced between the magnetic fields of the flux tube and coronal hole.
Results: We find that a series of reconnection reversals (or oscillatory reconnection) takes place, whereby reconnection occurs in distinct bursts and the inflow and outflow magnetic fields of one burst of reconnection become the outflow and inflow fields in the following burst of reconnection, respectively. During each burst of reconnection the gas pressure in the bounded outflow regions increases above the level of that in the inflow regions and, eventually, gives rise to a reconnection reversal. In consecutive bursts of reconnection, the contrast in the gas pressure across the boundaries of the inflow and outflow regions decreases and, over time, the system settles towards equilibrium. Once the equilibrium state is reached, all reconnection ceases. This is the first reported instance of oscillatory reconnection initiated in a self-consistent manner, and the signatures of the mechanism compare favourably with observations of select flux emergence events and with solar and stellar flares.
Conclusions: Across the broader spectrum of reconnecting systems, oscillatory reconnection will only occur if the outflow regions are quasi-bounded during each burst of reconnection. The swaying outflow jet and periodic heating signatures of oscillatory reconnection are exceedingly similar to those exhibited by MHD modes and, in many observations, distinction between the two mechanisms may be impossible. Title: Magnetic Flux Emergence, Activity, Eruptions and Magnetic Clouds: Following Magnetic Field from the Sun to the Heliosphere Authors: van Driel-Gesztelyi, L.; Culhane, J. L. Bibcode: 2009odsm.book..351V Altcode: We present an overview of how the principal physical properties of magnetic flux which emerges from the toroidal fields in the tachocline through the turbulent convection zone to the solar surface are linked to solar activity events, emphasizing the effects of magnetic field evolution and interaction with other magnetic structures on the latter. We compare the results of different approaches using various magnetic observables to evaluate the probability of flare and coronal mass ejection (CME) activity and forecast eruptive activity on the short term (i.e. days). Then, after a brief overview of the observed properties of CMEs and their theoretical models, we discuss the ejecta properties and describe some typical magnetic and composition characteristics of magnetic clouds (MCs) and interplanetary CMEs (ICMEs). We review some individual examples to clarify the link between eruptions from the Sun and the properties of the resulting ejecta. The importance of a synthetic approach to solar and interplanetary magnetic fields and activity is emphasized. Title: Flux Rope Eruption From the Sun to the Earth: What do Reversals in the Azimuthal Magnetic Field Gradient Tell us About the Evolution of the Magnetic Structure? Authors: Steed, K.; Owen, C. J.; Harra, L. K.; Green, L. M.; Dasso, S.; Walsh, A. P.; Démoulin, P.; van Driel-Gesztelyi, L. Bibcode: 2008AGUFMSH23B1638S Altcode: Using ACE in situ data we identify and describe an interplanetary magnetic cloud (MC) observed near Earth on 13 April 2006. We also use multi-instrument and multi-wavelength observations from SOHO, TRACE and ground-based solar observatories to determine the solar source of this magnetic cloud. A launch window for the MC between 9 and 11 April 2006 was estimated from the propagation time of the ejecta observed near Earth. A number of large active regions were present on the Sun during this period, which were initially considered to be the most likely candidate source regions of the MC. However, it was determined that the solar source of the MC was a small, spotless active region observed in the Northern Hemisphere. Following an eruption from this region on 11 April 2006, the ACE spacecraft detected, 59 h later, the passage of the MC, preceded by the arrival of a weak, forward fast shock. The link between the eruption in this active region and the interplanetary MC is supported by several pieces of evidence, including the location of the solar source near to the disk centre and to the east of the central meridian (in agreement with the spacecraft trajectory through the western leg of the magnetic cloud), the propagation time of the ejecta, the agreement between the amount of flux in the magnetic cloud and in the active region, and the agreement between the signs of helicity of the magnetic cloud and the active region (which differs from the sign of helicity of each of the other active regions on the Sun at this time). In addition, the active region is located on the boundary of a coronal hole, and a high speed solar wind stream originating from this region is observed near Earth shortly after the passage of the magnetic cloud. This event highlights the complexities associated with locating the solar source of an ICME observed near Earth, and serves to emphasise that it is the combination of a number of physical characteristics and signatures that is important for successfully tying together the Earth-end and the Sun-end of an event. Further investigation of this MC has revealed some sub-structure towards its centre, observed as a small scale reversal of the azimuthal magnetic field of the MC, similar to that reported by Dasso et al., 2007. We explore several possible explanations for this signature, including the occurrence of multiple flux ropes and/or warping of the magnetic cloud. We also consider whether magnetic reconnection plays a role in creating the geometry that would explain these observations. Title: Preface Authors: Klein, Karl-Ludwig; Pohjolainen, Silja; van Driel-Gesztelyi, Lidia Bibcode: 2008SoPh..253....1K Altcode: 2008SoPh..tmp..191K No abstract at ADS Title: The Recovery of CME-Related Dimmings and the ICME's Enduring Magnetic Connection to the Sun Authors: Attrill, G. D. R.; van Driel-Gesztelyi, L.; Démoulin, P.; Zhukov, A. N.; Steed, K.; Harra, L. K.; Mandrini, C. H.; Linker, J. Bibcode: 2008SoPh..252..349A Altcode: 2008SoPh..tmp..158A It is generally accepted that transient coronal holes (TCHs, dimmings) correspond to the magnetic footpoints of CMEs that remain rooted in the Sun as the CME expands out into the interplanetary space. However, the observation that the average intensity of the 12 May 1997 dimmings recover to their pre-eruption intensity in SOHO/EIT data within 48 hours, whilst suprathermal unidirectional electron heat fluxes are observed at 1 AU in the related ICME more than 70 hours after the eruption, leads us to question why and how the dimmings disappear whilst the magnetic connectivity is maintained. We also examine two other CME-related dimming events: 13 May 2005 and 6 July 2006. We study the morphology of the dimmings and how they recover. We find that, far from exhibiting a uniform intensity, dimmings observed in SOHO/EIT data have a deep central core and a more shallow extended dimming area. The dimmings recover not only by shrinking of their outer boundaries but also by internal brightenings. We quantitatively demonstrate that the model developed by Fisk and Schwadron (Astrophys. J.560, 425, 2001) of interchange reconnections between "open" magnetic field and small coronal loops is a strong candidate for the mechanism facilitating the recovery of the dimmings. This process disperses the concentration of "open" magnetic field (forming the dimming) out into the surrounding quiet Sun, thus recovering the intensity of the dimmings whilst still maintaining the magnetic connectivity to the Sun. Title: Why are CMEs large-scale coronal events: nature or nurture? Authors: van Driel-Gesztelyi, L.; Attrill, G. D. R.; Démoulin, P.; Mandrini, C. H.; Harra, L. K. Bibcode: 2008AnGeo..26.3077V Altcode: The apparent contradiction between small-scale source regions of, and large-scale coronal response to, coronal mass ejections (CMEs) has been a long-standing puzzle. For some, CMEs are considered to be inherently large-scale events eruptions in which a number of flux systems participate in an unspecified manner, while others consider magnetic reconnection in special global topologies to be responsible for the large-scale response of the lower corona to CME events. Some of these ideas may indeed be correct in specific cases. However, what is the key element which makes CMEs large-scale? Observations show that the extent of the coronal disturbance matches the angular width of the CME an important clue, which does not feature strongly in any of the above suggestions. We review observational evidence for the large-scale nature of CME source regions and find them lacking. Then we compare different ideas regarding how CMEs evolve to become large-scale. The large-scale magnetic topology plays an important role in this process. There is amounting evidence, however, that the key process is magnetic reconnection between the CME and other magnetic structures. We outline a CME evolution model, which is able to account for all the key observational signatures of large-scale CMEs and presents a clear picture how large portions of the Sun become constituents of the CME. In this model reconnection is driven by the expansion of the CME core resulting from an over-pressure relative to the pressure in the CME's surroundings. This implies that the extent of the lower coronal signatures match the final angular width of the CME. Title: Locating the solar source of 13 April 2006 magnetic cloud Authors: Steed, K.; Owen, C. J.; Harra, L. K.; Green, L. M.; Dasso, S.; Walsh, A. P.; Démoulin, P.; van Driel-Gesztelyi, L. Bibcode: 2008AnGeo..26.3159S Altcode: Using Advanced Composition Explorer (ACE) in situ data we identify and describe an interplanetary magnetic cloud (MC) observed near Earth on 13 April 2006. We also use multi-instrument and multi-wavelength observations from the Solar and Heliospheric Observatory (SOHO), the Transition Region and Coronal Explorer (TRACE) and ground-based solar observatories to determine the solar source of this magnetic cloud. A launch window for the MC between 9 and 11 April 2006 was estimated from the propagation time of the ejecta observed near Earth. A number of large active regions (ARs) were present on the Sun during this period, which were initially considered to be the most likely candidate source regions of the MC. However, it was determined that the solar source of the MC was a small, spotless active region observed in the Northern Hemisphere. Following an eruption from this region on 11 April 2006, the ACE spacecraft detected, 59 h later, the passage of the MC, preceded by the arrival of a weak, forward fast shock. The link between the eruption in this active region and the interplanetary MC is supported by several pieces of evidence, including the location of the solar source near to the disk centre and to the east of the central meridian (in agreement with the spacecraft trajectory through the western leg of the magnetic cloud), the propagation time of the ejecta, the agreement between the amount of flux in the magnetic cloud and in the active region, and the agreement between the signs of helicity of the magnetic cloud and the active region (which differs from the sign of helicity of each of the other active regions on the Sun at this time). In addition, the active region is located on the boundary of a coronal hole, and a high speed solar wind stream originating from this region is observed near Earth shortly after the passage of the magnetic cloud. Title: Multi-scale reconnections in a complex CME Authors: van Driel-Gesztelyi, L.; Goff, C. P.; Démoulin, P.; Culhane, J. L.; Matthews, S. A.; Harra, L. K.; Mandrini, C. H.; Klein, K. -L.; Kurokawa, H. Bibcode: 2008AdSpR..42..858V Altcode: A series of three flares of GOES class M, M and C, and a CME were observed on 20 January 2004 occurring in close succession in NOAA 10540. Types II, III, and N radio bursts were associated. We use the combined observations from TRACE, EIT, Hα images from Kwasan Observatory, MDI magnetograms, GOES, and radio observations from Culgoora and Wind/ WAVES to understand the complex development of this event. We reach three main conclusions. First, we link the first two impulsive flares to tether-cutting reconnections and the launch of the CME. This complex observation shows that impulsive quadrupolar flares can be eruptive. Second, we relate the last of the flares, an LDE, to the relaxation phase following forced reconnections between the erupting flux rope and neighbouring magnetic field lines, when reconnection reverses and restores some of the pre-eruption magnetic connectivities. Finally, we show that reconnection with the magnetic structure of a previous CME launched about 8 h earlier injects electrons into open field lines having a local dip and apex (located at about six solar radii height). This is observed as an N-burst at decametre radio wavelengths. The dipped shape of these field lines is due to large-scale magnetic reconnection between expanding magnetic loops and open field lines of a neighbouring streamer. This particular situation explains why this is the first N-burst ever observed at long radio wavelengths. Title: Study of the Physical Properties of Coronal ``Waves'' and Associated Dimmings Authors: Attrill, G. D. R.; Harra, L. K.; van Driel-Gesztelyi, L.; Williams, D.; Alexeev, I. V. Bibcode: 2008ASPC..397..126A Altcode: We present results from our study run by Hinode, designed to obtain information on the physical properties of the diffuse bright fronts known as ``EIT coronal waves'' and their associated dimmings. We analyse data obtained during a frustrated eruption event on 5th May 2007. The event produces a bright front as well as deep and shallow dimmings. We show that the dimmings of this frustrated eruption show similar physical properties to those observed in textbook ``EIT coronal wave'' events. The Hinode/EIS data show that both the deep and shallow dimmings associated with this frustrated eruption show blue-shifted velocities. It is therefore consistent that, like the deep core dimmings, the widespread shallow dimmings observed with many textbook coronal ``wave'' events may also be due to plasma outflows. Title: Long Duration Thermal Hard X-ray Sources Observed in Two Eruptive Flares Authors: Bone, L. A.; Culhane, J. L.; van Driel-Gesztelyi, L.; Hara, H. Bibcode: 2008ASPC..397..160B Altcode: We present observations of two eruptive flares on 17 of December 2006 (C1.9) and 19 of May 2007 (B9.7) which had good coverage with both Hinode and RHESSI. In these flares we see a long lived, gradual thermal hard X-ray source of low emission measure and, relative to the loops observed with GOES and XRT, high temperature. The lack of a non-thermal hard X-ray component and impulsive behaviour is inconsistent with electron beam driven chromospheric evaporation. Title: Hinode EIS and XRT Observations of Hot Jets in Coronal Holes - Does the Plasma Escape? Authors: Baker, D.; van Driel-Gesztelyi, L.; Kamio, S.; Culhane, J. L.; Harra, L. K.; Sun, J.; Young, P. R.; Matthews, S. A. Bibcode: 2008ASPC..397...23B Altcode: X-ray jets have been detected in the extreme ultraviolet (EUV) and soft X-ray observations of Hinode's EIS and XRT instruments. Both instruments were used to observe the jets in polar and on-disk coronal holes (CHs). Here, we present a multi-wavelength study of an X-ray jet and its associated bright point found in an equatorial CH on 19 June 2007. Light curves (LCs) in 22 different emission lines were compared to that of Hinode/XRT. As we found in a previous study of two polar X-ray jets, this jet shows a post-jet increase in its EUV LCs. The post-jet enhancement appears cooler than the jet. We suggest this feature arises because the hot plasma of the jet, having failed to reach escape speeds, cools and falls back along the near vertical paths expected to be created by reconnection with open field lines of CHs. In addition to the increase in post-jet EUV intensity, we found tentative evidence of impact heating possibly caused by the fall-back of plasma. Title: Twist, Writhe and Rotation of Magnetic Flux Ropes in Filament Eruptions and Coronal Mass Ejections Authors: Török, T.; Berger, M. A.; Kliem, B.; Démoulin, P.; Linton, M.; van Driel-Gesztelyi, L. Bibcode: 2008ESPM...12.3.54T Altcode: We present the first quantitative analysis of the conversion of twist into writhe in the course of ideal MHD instabilities in erupting coronal magnetic flux ropes. For our analysis, we consider numerical simulations of two instabilities which have been suggested as trigger and initial driving mechanisms in filament eruptions and coronal mass ejections, namely the helical kink instability and the torus instability. We use two different coronal flux rope models as initial conditions in the simulations, namely the cylindrical Gold-Hoyle equilibrium and the toroidal Titov-Demoulin equilibrium.

For each model, we perform a series of simulations with different amounts of initial flux rope twist. In order to study both confined and ejective eruptions, we additionally use different initial potential fields overlying the flux rope in the simulations of the Titov-Demoulin model.

In all simulations, we measure the writhe of the flux rope and the corresponding rotation of its axis in vertical projection by making use of recently developed expressions which permit us to calculate writhe as a single integral in space. We discuss the implications of our results for filament eruptions, coronal mass ejections and magnetic clouds. Title: Outflows at the Edges of Active Regions: Contribution to Solar Wind Formation? Authors: Harra, L. K.; Sakao, T.; Mandrini, C. H.; Hara, H.; Imada, S.; Young, P. R.; van Driel-Gesztelyi, L.; Baker, D. Bibcode: 2008ApJ...676L.147H Altcode: The formation of the slow solar wind has been debated for many years. In this Letter we show evidence of persistent outflow at the edges of an active region as measured by the EUV Imaging Spectrometer on board Hinode. The Doppler velocity ranged between 20 and 50 km s-1 and was consistent with a steady flow seen in the X-Ray Telescope. The latter showed steady, pulsing outflowing material and some transverse motions of the loops. We analyze the magnetic field around the active region and produce a coronal magnetic field model. We determine from the latter that the outflow speeds adjusted for line-of-sight effects can reach over 100 km s-1. We can interpret this outflow as expansion of loops that lie over the active region, which may either reconnect with neighboring large-scale loops or are likely to open to the interplanetary space. This material constitutes at least part of the slow solar wind. Title: Erratum: "Outflows at the Edges of Active Regions: Contribution to Solar Wind Formation?" (ApJ, 676, L147 [2008]) Authors: Harra, L. K.; Sakao, T.; Mandrini, C. H.; Hara, H.; Imada, S.; Young, P. R.; van Driel-Gesztelyi, L.; Baker, D. Bibcode: 2008ApJ...677L.159H Altcode: No abstract at ADS Title: CME-related dimmings as a signature of interplanetary magnetic cloud footpoints Authors: Mandrini, Cristina H.; Soledad Nakwacki, Ms Maria; Attrill, Gemma; van Driel-Gesztelyi, Lidia; Dasso, Sergio; Demoulin, Pascal Bibcode: 2008cosp...37.1900M Altcode: 2008cosp.meet.1900M Coronal dimmings are often present on both sides of erupting magnetic configurations. It has been suggested that dimmings mark the location of the footpoints of ejected flux ropes and, thus, their magnetic flux can be used as a proxy for the flux involved in the ejection. If so, this quantity can be compared to the flux in the associated interplanetary magnetic cloud to find clues about the origin of the ejected flux rope. In the context of this physical interpretation, we analyse several events, flares and coronal mass ejections (CMEs), for which we can find their interplanetary counterpart. We combine SOHO/Extreme Ultraviolet Imaging Telescope data and Michelson Doppler Imager magnetic maps to identify and measure the flux in the dimming regions. We model the associated clouds and compute their magnetic flux using in situ observations. We find that the magnetic fluxes of the dimmings and magnetic clouds are compatible in some cases; though this is not the case for large-scale events and eruptions that occur in regions that are not isolated from other flux concentrations. We conclude that the interpretation of dimmings requires a deeper analysis of the global magnetic field configuration, since at least a fraction of the dimmed regions could be formed by reconnection between the erupting field and the surrounding magnetic structures. Title: Interaction between emerging flux and coronal hole - observations and simulations Authors: van Driel-Gesztelyi, Lidia; Baker, Deborah; Murray, Michelle; Demoulin, Pascal; Attrill, Gemma; Matthews, Sarah A.; Mandrini, Cristina H.; Toeroek, Tibor Bibcode: 2008cosp...37.3288V Altcode: 2008cosp.meet.3288V Flux emergence in the vicinity of or inside a coronal hole (CH) is expected to induce magnetic reconnection between the closed emerging and open CH magnetic field lines, resulting in an evolution of the CH as formerly closed field lines become topologically open, while at the same time, open field lines close down. Through two case studies we show observational signatures of this (interchange) reconnection process and discuss its implications. First, using SOHO EIT and MDI data, we study a small active region (AR10869) emerging in the close vicinity of a low-latitude coronal hole in April 2006. The interfacing magnetic polarities between the AR and the CH were opposite, favourable for magnetic reconnection. We indeed observe the coupled formation of bright closed loops between the CH and the AR and coronal dimming on the far side of the AR, which we interpret as evidence of interchange reconnection. This process effectively modifies the CH boundary (making it retreat), while simultaneously displacing open field lines to the far side of the AR. In order to study this process in detail, we perform 2.5D MHD simulations, which qualitatively reproduce important aspects of the observations. We expect to find upflows of plasma at the location where previously closed field lines are opening up as well as on the reconnecting side, but since we had no spectroscopic data for this event, we can not verify this. Therefore we analyze Hinode/EIS line-of-sight velocity maps of another low-latitude CH with a small AR in its midst observed on 18 Oct. 2007. We find that while closed loops of the bipole are dominated by downflows in the Fe XII, Fe XIII and Fe XV lines, the strongest coronal plasma upflows are indeed located around and particularly at the "far side" of the bipolar AR, i.e. having the same polarity as the dominant polarity of the CH. The emerging biplole and the series of interchange reconnections it induces create a significant additional plasma upflow in the CH, thus we identify this outflow must contribute to the acceleration of the fast solar wind. Title: Editorial Appreciation Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2008SoPh..247....1L Altcode: 2008SoPh..tmp....5L No abstract at ADS Title: Breaking or maintaining magnetic connection of CMEs to the Sun - solar vs. interplanetary signatures tested Authors: van Driel-Gesztelyi, Lidia; Attrill, Gemma; Demoulin, Pascal; Mandrini, Cristina H.; Harra, Louise K. Bibcode: 2008cosp...37.3287V Altcode: 2008cosp.meet.3287V Though their relationship is complex, the presence of suprathermal unior bi-directional electron streams in ICMEs are treated as signatures of magnetic field lines with one or both ends being connected to the Sun, respectively, while their absence is interpreted as disconnection. However, do we have any reliable signature in the solar corona distinguishing between maintained connection and disconnection? We test two solar signatures against interplanetary suprathermal electron signatures in order to establish their relevance. We test the hypothesis that the recovery of Transient Coronal Holes (TCHs, dimming regions corresponding to the footpoints of CMEs) is a signature of magnetic disconnection from the Sun. Through three case studies we quantitatively demonstrate that magnetic reconnections between field lines of the expanded CME magnetic field and small coronal loops can act to disperse the concentration of CME footpoints (forming the dimming region) out into the surrounding quiet Sun, thus recovering the intensity of the dimming region whilst still maintaining the magnetic connectivity to the Sun. This analysis provides evidence that the recovery of coronal dimming regions can, in fact, be simply reconciled with maintained magnetic connectivity to the Sun. However, disconnection can occur when open field lines are involved in reconnection with CMEs. We show through two well-observed case studies that magnetic reconnection between the expanding CME and a nearby coronal hole (CH) is indeed able to disconnect one leg of the expanding CME magnetic structure, as indicated by uni-directional electron streams in their respective ICMEs. Therefore we suggest that brightenings (signatures of reconnection) appearing along a coronal hole boundary in the wake of a CME can be treated as a signature of (at least partial) disconnection of one of the CME legs from the Sun. Title: Flare and Erupting Filament of 19th May, 2007 - Sources of a Magnetic Cloud Observed by Stereo Authors: Culhane, J. Leonard; Bone, Laura; Hara, Hirohisa; Farrugia, Charles; Galvin, Antoinette; van Driel-Gesztelyi, Lidia; Popecki, Mark; Luhmann, Janet G.; Veronig, Astrid Bibcode: 2008cosp...37..609C Altcode: 2008cosp.meet..609C A GOES Class B9.5 flare was observed on the Sun starting 19-May-2007 at 12:51 UT. Data obtained by the Hinode, TRACE, RHESSI, STEREO and SOHO spacecraft will be discussed. The evolution and eventual eruption of a related Halpha filament were monitored by patrol observations at Kanzelhoehe. These observations and associated detection of EUV-emitting filament material will also be presented. The flare energetics and the possible role of the flare in the filament eruption will be examined. Finally the relationship of the magnetic configuration of the solar eruption along with the temperature and composition of erupting material will be assessed in relation to the properties of a magnetic cloud later detected by STEREO in-situ instruments near Earth on 22-May-2007. Title: What kinking filament eruptions tell us about the physical nature of transient coronal sigmoids ? Authors: van Driel-Gesztelyi, Lidia; Green, Lucie M.; Kliem, Bernhard; Toeroek, Tibor; Attrill, Gemma Bibcode: 2008cosp...37.3289V Altcode: 2008cosp.meet.3289V Soft X-ray images of the Sun have shown that some active regions contain loops, or collections of loops, which appear forward or reverse 'S' in shape. These features have been termed sigmoids. These structures are of interest because their presence in an active region has been linked to eruptive activity and the sense of sigmoid orientation is taken to indicate the sense of shear and twist (or helicity) in the magnetic field. Differing models have been put forward in order to explain the physical nature of sigmoids and the role they play in an eruption. We use multiwavelength observations (Yohkoh/SXT, TRACE, SOHO/EIT and MDI, H-alpha) to investigate how transient sigmoids are formed. We also investigate filament eruptions from these active regions, which show a clear sign of rotation of their apex. We find that for positive (negative) helicity the filament apex rotates clockwise (counterclockwise), consistent with the flux rope taking on a reverse (forward) S shape, which is opposite to that observed for the sigmoid. These observations put constraints on sigmoid models, excluding some of them. We conclude that transient sigmoids are associated with the formation of current sheets and heating along field lines under a dynamic flux rope. Title: Transient Coronal Sigmoids and Rotating Erupting Flux Ropes Authors: Green, L. M.; Kliem, B.; Török, T.; van Driel-Gesztelyi, L.; Attrill, G. D. R. Bibcode: 2007SoPh..246..365G Altcode: To determine the relationship between transient coronal (soft X-ray or EUV) sigmoids and erupting flux ropes, we analyse four events in which a transient sigmoid could be associated with a filament whose apex rotates upon eruption and two further events in which the two phenomena were spatially but not temporally coincident. We find the helicity sign of the erupting field and the direction of filament rotation to be consistent with the conversion of twist into writhe under the ideal MHD constraint of helicity conservation, thus supporting our assumption of flux rope topology for the rising filament. For positive (negative) helicity the filament apex rotates clockwise (counterclockwise), consistent with the flux rope taking on a reverse (forward) S shape, which is opposite to that observed for the sigmoid. This result is incompatible with two models for sigmoid formation: one identifying sigmoids with upward arching kink-unstable flux ropes and one identifying sigmoids with a current layer between two oppositely sheared arcades. We find instead that the observations agree well with the model by Titov and Démoulin (Astron. Astrophys.351, 707, 1999), which identifies transient sigmoids with steepened current layers below rising flux ropes. Title: Hinode EUV Study of Jets in the Sun's South Polar Corona Authors: Culhane, Len; Harra, Louise K.; Baker, Deborah; van Driel-Gesztelyi, Lidia; Sun, Jian; Doschek, George A.; Brooks, David H.; Lundquist, Loraine L.; Kamio, Suguru; Young, Peter R.; Hansteen, Viggo H. Bibcode: 2007PASJ...59S.751C Altcode: A number of coronal bright points and associated plasma jet features were seen in an observation of the South polar coronal hole during 2007 January. The 40" wide slot was used at the focus of the Hinode EUV Imaging Spectrometer to provide spectral images for two of these events. Light curves are plotted for a number of emission lines that include He II 256Å (0.079MK) and cover the temperature interval from 0.4MK to 5.0MK. Jet speed measurements indicate values less than the escape velocity. The light curves show a post-jet enhancement in a number of the cooler coronal lines indicating that after a few minutes cooling, the plasma fell back to its original acceleration site. This behavior has not been previously observed by e.g., the Yohkoh Soft X-ray Telescope due to the comparatively high temperature cut-off in its response. The observations are consistent with the existing models that involve magnetic reconnection between emerging flux and the ambient open field lines in the polar coronal hole. However we do not have sufficient coverage of lines from lower temperature ion species to register the Hα-emitting surge material that is associated with some of these models. Title: Optical flares from the faint mid-dM star 2MASS J00453912+4140395 Authors: Kovári, Zs.; Vilardell, F.; Ribas, I.; Vida, K.; van Driel-Gesztelyi, L.; Jordi, C.; Oláh, K. Bibcode: 2007AN....328..904K Altcode: 2007arXiv0711.0742K We present B and V light curves of a large stellar flare obtained with the Wide Field Camera at the Isaac Newton 2.5-m telescope (La Palma). The source object is a faint (m_V=21.38) foreground star in the field of the Andromeda galaxy, with its most probable spectral type being dM4. We provide an estimate of the total flare energy in the optical range and find it to be of the order of 1035 erg. The cooling phase of the large flare shows three additional weak flare-like events, which we interpret as results of a triggering mechanism also observed on the Sun during large coronal mass ejections. Title: Editors' note Authors: Forgács-Dajka, E.; Ballai, I.; van Driel-Gesztelyi, L. Bibcode: 2007AN....328..725F Altcode: No abstract at ADS Title: Evidence for interchange reconnection between a coronal hole and an adjacent emerging flux region Authors: Baker, D.; van Driel-Gesztelyi, L.; Attrill, G. D. R. Bibcode: 2007AN....328..773B Altcode: Coronal holes are regions of dominantly monopolar magnetic field on the Sun where the field is considered to be `open' towards interplanetary space. Magnetic bipoles emerging in proximity to a coronal hole boundary naturally interact with this surrounding "open" magnetic field. In the case of oppositely aligned polarities between the active region and the coronal hole, we expect interchange reconnection to take place, driven by the coronal expansion of the emerging bipole as well as occasional eruptive events. Using SOHO/EIT and SOHO/MDI data, we present observational evidence of such interchange reconnection by studying AR 10869 which emerged close to a coronal hole. We find closed loops forming between the active region and the coronal hole leading to the retreat of the hole. At the same time, on the far side of the active region, we see dimming of the corona which we interpret as a signature of field line `opening' there, as a consequence of a topological displacement of the `open' field lines of the coronal hole. Title: Coronal ``wave'': A signature of the mechanism making CMEs large-scale in the low corona? Authors: Attrill, G. D. R.; Harra, L. K.; van Driel-Gesztelyi, L.; Démoulin, P.; Wülser, J. -P. Bibcode: 2007AN....328..760A Altcode: We analyse one of the first coronal waves observed by STEREO/EUVI associated with a source region just behind the limb, NOAA 10940. We apply the coronal ``wave'' model proposed by Attrill et al. (2007) to explain the evolution of the observed bright fronts, thereby arguing that the bright fronts and dimmings are due to magnetic reconnections between the expanding CME core and surrounding magnetic structures. We offer a discussion showing that this model provides a mechanism via which CMEs, expanding from a small source region can naturally become large-scale in the low corona. Title: How Does Large Flaring Activity from the Same Active Region Produce Oppositely Directed Magnetic Clouds? Authors: Harra, Louise K.; Crooker, Nancy U.; Mandrini, Cristina H.; van Driel-Gesztelyi, Lidia; Dasso, Sergio; Wang, Jingxiu; Elliott, Heather; Attrill, Gemma; Jackson, Bernard V.; Bisi, Mario M. Bibcode: 2007SoPh..244...95H Altcode: We describe the interplanetary coronal mass ejections (ICMEs) that occurred as a result of a series of solar flares and eruptions from 4 to 8 November 2004. Two ICMEs/magnetic clouds occurring from these events had opposite magnetic orientations. This was despite the fact that the major flares related to these events occurred within the same active region that maintained the same magnetic configuration. The solar events include a wide array of activities: flares, trans-equatorial coronal loop disappearance and reformation, trans-equatorial filament eruption, and coronal hole interaction. The first major ICME/magnetic cloud was predominantly related to the active region 10696 eruption. The second major ICME/magnetic cloud was found to be consistent with the magnetic orientation of an erupting trans-equatorial filament or else a rotation of 160° of a flux rope in the active region. We discuss these possibilities and emphasize the importance of understanding the magnetic evolution of the solar source region before we can begin to predict geoeffective events with any accuracy. Title: CME Propagation Characteristics from Radio Observations Authors: Pohjolainen, S.; van Driel-Gesztelyi, L.; Culhane, J. L.; Manoharan, P. K.; Elliott, H. A. Bibcode: 2007SoPh..244..167P Altcode: 2007arXiv0711.3168P We explore the relationship among three coronal mass ejections (CMEs), observed on 28 October 2003, 7 November 2004, and 20 January 2005, the type II burst-associated shock waves in the corona and solar wind, as well as the arrival of their related shock waves and magnetic clouds at 1 AU. Using six different coronal/interplanetary density models, we calculate the speeds of shocks from the frequency drifts observed in metric and decametric radio wave data. We compare these speeds with the velocity of the CMEs as observed in the plane-of-the-sky white-light observations and calculated with a cone model for the 7 November 2004 event. We then follow the propagation of the ejecta using Interplanetary Scintillation measurements, which were available for the 7 November 2004 and 20 January 2005 events. Finally, we calculate the travel time of the interplanetary shocks between the Sun and Earth and discuss the velocities obtained from the different data. This study highlights the difficulties in making velocity estimates that cover the full CME propagation time. Title: Are CME-Related Dimmings Always a Simple Signature of Interplanetary Magnetic Cloud Footpoints? Authors: Mandrini, C. H.; Nakwacki, M. S.; Attrill, G.; van Driel-Gesztelyi, L.; Démoulin, P.; Dasso, S.; Elliott, H. Bibcode: 2007SoPh..244...25M Altcode: Coronal dimmings are often present on both sides of erupting magnetic configurations. It has been suggested that dimmings mark the location of the footpoints of ejected flux ropes and, thus, their magnetic flux can be used as a proxy for the flux involved in the ejection. If so, this quantity can be compared to the flux in the associated interplanetary magnetic cloud to find clues about the origin of the ejected flux rope. In the context of this physical interpretation, we analyze the event, flare, and coronal mass ejection (CME) that occurred in active region 10486 on 28 October 2003. The CME on this day is associated with large-scale dimmings, located on either side of the main flaring region. We combine SOHO/Extreme Ultraviolet Imaging Telescope data and Michelson Doppler Imager magnetic maps to identify and measure the flux in the dimming regions. We model the associated cloud and compute its magnetic flux using in situ observations from the Magnetometer Instrument and the Solar Wind Electron Proton Alpha Monitor aboard the Advance Composition Explorer. We find that the magnetic fluxes of the dimmings and magnetic cloud are incompatible, in contrast to what has been found in previous studies. We conclude that, in certain cases, especially in large-scale events and eruptions that occur in regions that are not isolated from other flux concentrations, the interpretation of dimmings requires a deeper analysis of the global magnetic configuration, since at least a fraction of the dimmed regions is formed by reconnection between the erupting field and the surrounding magnetic structures. Title: Hinode Euv Study Of Jets In The Sun’s South Polar Corona Authors: Culhane, J. L.; Brooks, D. H.; Doschek, G. A.; Harra, L. K.; van Driel-Gesztelyi, L.; Baker, D.; Lundquist, L. L.; Hansteen, V. H.; Kamio, S. Bibcode: 2007AAS...210.7201C Altcode: 2007BAAS...39..178C Using the Hinode EUV Imaging Spectrometer coronal jets were observed on 20-JAN-2007 over a range of emission lines and corresponding plasma temperatures using the 40 arc sec wide slot images. In this preliminary analysis, jet plasma temperature and emissivity have been estimated while, based on assumptions about the jet morphology, electron density estimates are given and jet velocity measured. The evolution of the jets will be followed in a number of different EUV emission lines and jet energy input as a function of time will be assessed with reference to the magnetic field topologies involved. Title: Coronal "wave": Magnetic Footprint Of A Cme? Authors: Attrill, Gemma; Harra, L. K.; van Driel-Gesztelyi, L.; Demoulin, P.; Wuelser, J. Bibcode: 2007AAS...210.2921A Altcode: 2007BAAS...39..141A We propose a new mechanism for the generation of "EUV coronal waves". This work is based on new analysis of data from SOHO/EIT, SOHO/MDI & STEREO/EUVI. Although first observed in 1997, the interpretation of coronal waves as flare-induced or CME-driven remains a debated topic. We investigate the properties of two "classical" SOHO/EIT coronal waves in detail. The source regions of the associated CMEs possess opposite helicities & the coronal waves display rotations in opposite senses. We observe deep dimmings near the flare site & also widespread diffuse dimming, accompanying the expansion of the EIT wave. We report a new property of these EIT waves, namely, that they display dual brightenings: persistent ones at the outermost edge of the core dimming regions & simultaneously diffuse brightenings constituting the leading edge of the coronal wave, surrounding the expanding diffuse dimmings. We show that such behaviour is consistent with a diffuse EIT wave being the magnetic footprint of a CME. We propose a new mechanism where driven magnetic reconnections between the skirt of the expanding CME & quiet-Sun magnetic loops generate the observed bright diffuse front. The dual brightenings & widespread diffuse dimming are identified as innate characteristics of this process. In addition we present some of the first analysis of a STEREO/EUVI limb coronal wave. We show how the evolution of the diffuse bright front & dimmings can be understood in terms of the model described above. We show that an apparently stationary part of the bright front can be understood in terms of magnetic interchange reconnections between the expanding CME & the "open" magnetic field of a low-latitude coronal hole. We use both the SOHO/EIT & STEREO/EUVI events to demonstrate that through successive reconnections, this new model provides a natural mechanism via which CMEs can become large-scale in the lower corona. Title: Commission 10: Solar Activity Authors: Melrose, Donald B.; Klimchuk, James A.; Benz, A. O.; Craig, I. J. D.; Gopalswamy, N.; Harrison, R. A.; Kozlovsky, B. Z.; Poletto, G.; Schrijver, K. J.; van Driel-Gesztelyi, L.; Wang, J. -X. Bibcode: 2007IAUTA..26...75M Altcode: Commission 10 aims at the study of various forms of solar activity, including networks, plages, pores, spots, fibrils, surges, jets, filaments/prominences, coronal loops, flares, coronal mass ejections (CMEs), solar cycle, microflares, nanoflares, coronal heating etc., which are all manifestation of the interplay of magnetic fields and solar plasma. Increasingly important is the study of solar activities as sources of various disturbances in the interplanetary space and near-Earth "space weather".Over the past three years a major component of research on the active Sun has involved data from the RHESSI spacecraft. This review starts with an update on current and planned solar observations from spacecraft. The discussion of solar flares gives emphasis to new results from RHESSI, along with updates on other aspects of flares. Recent progress on two theoretical concepts, magnetic reconnection and magnetic helicity is then summarized, followed by discussions of coronal loops and heating, the magnetic carpet and filaments. The final topic discussed is coronal mass ejections and space weather.The discussions on each topic is relatively brief, and intended as an outline to put the extensive list of references in context.The review was prepared jointly by the members of the Organizing Committee, and the names of the primary contributors to the various sections are indicated in parentheses. Title: A Multiple Flare Scenario where the Classic Long-Duration Flare Was Not the Source of a CME Authors: Goff, C. P.; van Driel-Gesztelyi, L.; Démoulin, P.; Culhane, J. L.; Matthews, S. A.; Harra, L. K.; Mandrini, C. H.; Klein, K. L.; Kurokawa, H. Bibcode: 2007SoPh..240..283G Altcode: A series of flares (GOES class M, M and C) and a CME were observed in close succession on 20 January 2004 in NOAA 10540. Radio observations, which took the form of types II, III and N bursts, were associated with these events. We use the combined observations from TRACE, EIT, Hα images from Kwasan, MDI magnetograms and GOES to understand the complex development of this event. Contrary to a standard interpretation, we conclude that the first two impulsive flares are part of the CME launch process while the following long-duration event flare represents simply the recovery phase. Observations show that the flare ribbons not only separate but also shift along the magnetic inversion line so that magnetic reconnection progresses stepwise to neighboring flux tubes. We conclude that "tether cutting" reconnection in the sheared arcade progressively transforms it to a twisted flux tube, which becomes unstable, leading to a CME. We interpret the third flare, a long-duration event, as a combination of the classical two-ribbon flare with the relaxation process following forced reconnection between the expanding CME structure and neighboring magnetic fields. Title: Decametric N Burst: A Consequence of the Interaction of Two Coronal Mass Ejections Authors: Démoulin, P.; Klein, K. -L.; Goff, C. P.; van Driel-Gesztelyi, L.; Culhane, J. L.; Mandrini, C. H.; Matthews, S. A.; Harra, L. K. Bibcode: 2007SoPh..240..301D Altcode: Radio emissions of electron beams in the solar corona and interplanetary space are tracers of the underlying magnetic configuration and of its evolution. We analyse radio observations from the Culgoora and WIND/WAVES spectrographs, in combination with SOHO/LASCO and SOHO/MDI data, to understand the origin of a type N burst originating from NOAA AR 10540 on January 20, 2004, and its relationship with type II and type III emissions. All bursts are related to the flares and the CME analysed in a previous paper (Goff et al., 2007). A very unusual feature of this event was a decametric type N burst, where a type III-like burst, drifting towards low frequencies (negative drift), changes drift first to positive, then again to negative. At metre wavelengths, i.e., heliocentric distances ≲1.5R⊙, these bursts are ascribed to electron beams bouncing in a closed loop. Neither U nor N bursts are expected at decametric wavelengths because closed quasi-static loops are not thought to extend to distances ≫1.5R⊙. We take the opportunity of the good multi-instrument coverage of this event to analyse the origin of type N bursts in the high corona. Reconnection of the expanding ejecta with the magnetic structure of a previous CME, launched about 8 hours earlier, injects electrons in the same manner as with type III bursts but into open field lines having a local dip and apex. The latter shape was created by magnetic reconnection between the expanding CME and neighbouring (open) streamer field lines. This particular flux tube shape in the high corona, between 5R⊙ and 10R⊙, explains the observed type N burst. Since the required magnetic configuration is only a transient phenomenon formed by reconnection, severe timing and topological constraints are present to form the observed decametric N burst. They are therefore expected to be rare features. Title: Coronal ``Wave'': Magnetic Footprint of a Coronal Mass Ejection? Authors: Attrill, Gemma D. R.; Harra, Louise K.; van Driel-Gesztelyi, Lidia; Démoulin, Pascal Bibcode: 2007ApJ...656L.101A Altcode: We investigate the properties of two ``classical'' EUV Imaging Telescope (EIT) coronal waves. The two source regions of the associated coronal mass ejections (CMEs) possess opposite helicities, and the coronal waves display rotations in opposite senses. We observe deep core dimmings near the flare site and also widespread diffuse dimming, accompanying the expansion of the EIT wave. We also report a new property of these EIT waves, namely, that they display dual brightenings: persistent ones at the outermost edge of the core dimming regions and simultaneously diffuse brightenings constituting the leading edge of the coronal wave, surrounding the expanding diffuse dimmings. We show that such behavior is consistent with a diffuse EIT wave being the magnetic footprint of a CME. We propose a new mechanism where driven magnetic reconnections between the skirt of the expanding CME magnetic field and quiet-Sun magnetic loops generate the observed bright diffuse front. The dual brightenings and the widespread diffuse dimming are identified as innate characteristics of this process. Title: From The Photosphere to the Interplanetary Medium: The Magnetic Helicity Sign from Observations Authors: Luoni, M. L.; Mandrini, C. H.; Dasso, S.; Démoulin, P.; Van Driel-Gesztelyi, L. Bibcode: 2007BAAA...50...43L Altcode: The helicity sign of the solar magnetic field exhibits a hemispheric preference. On a certain statistical base, it is negative (positive) in the northern (southern) hemisphere. In this work we study a set of active regions, observed from 1997 to 2001, for which we can determine the magnetic helicity sign from the evolution of their polarities during flux emergence. We confirm this sign analyzing the coronal field of the studied regions. Then, we combine this analysis with ``in situ'' observations of the magnetic clouds associated with the coronal mass ejections that occurred in those regions. Finally, we find that the helicity sign predicted by the distribution of the photospheric flux agrees with the one observed at coronal and interplanetary level. Title: Study of CME transit speeds for the event of 07-NOV-2004 Authors: Culhane, J. L.; Pohjolainen, S.; van Driel-Gesztelyi, L.; Manoharan, P. K.; Elliott, H. A. Bibcode: 2007AdSpR..40.1807C Altcode: Several methods for CME speed estimation are discussed. These include velocity derivation based on the frequency drifts observed in metric and decametric radio wave data using a range of coronal density models. Coronagraph height-time plots allow measurement of plane-of-sky and expansion speeds. These in turn can enable propagation speeds to be derived from a range of empirical relations. Simple geometric e.g., cone, models can provide propagation velocity estimates for suitable halo or partial halo events. Interplanetary scintillation observations allow speed estimates at large distances from the Sun detecting in particular the deceleration of the faster CMEs. Related interplanetary shocks and the arrival times and speeds of the associated magnetic clouds at Earth can also be considered. We discuss the application of some of these methods to the transit to Earth of a complex CME that originated earlier than 16:54 U.T. on 07-NOV-2004. The difficulties in making velocity estimates from radio observations, particularly under disturbed coronal conditions, are highlighted. Title: Using the Evolution of Coronal Dimming Regions to Probe the Global Magnetic Field Topology Authors: Attrill, G.; Nakwacki, M. S.; Harra, L. K.; Van Driel-Gesztelyi, L.; Mandrini, C. H.; Dasso, S.; Wang, J. Bibcode: 2006SoPh..238..117A Altcode: 2006SoPh..tmp...31A We demonstrate that study of the evolving magnetic nature of coronal dimming regions can be used to probe the large-scale magnetic structure involved in the eruption of a coronal mass ejection (CME). We analyse the intensity evolution of coronal dimming regions using 195 Å data from the Extreme ultraviolet Imaging Telescope (EIT) on board the Solar and Heliospheric Observatory (SOHO). We measure the magnetic flux, using data from the SOHO/Michelson Doppler Imager (MDI), in the regions that seem most likely to be related to plasma removal. Then, we compare these magnetic flux measurements to the flux in the associated magnetic cloud (MC). Here, we present our analysis of the well-studied event on 12 May 1997 that took place just after solar minimum in a simple magnetic configuration. We present a synthesis of results already published and propose that driven "interchange reconnection" between the expanding CME structure with ``open'' field lines of the northern coronal hole region led to the asymmetric temporal and spatial evolution of the two main dimming regions, associated with this event. As a result of this reconnection process, we find the southern-most dimming region to be the principal foot-point of the MC. The magnetic flux from this dimming region and that of the MC are found to be in close agreement within the same order of magnitude, 1021 Mx. Title: Build-up of a CME and its Interaction with Large-Scale Magnetic Structures Authors: van Driel-Gesztelyi, L.; Goff, C. P.; Demoulin, P.; Culhane, J. L.; Klein, K. L.; Mandrini, C. H.; Matthews, S. A.; Harra, K. L.; Kurokawa, H. Bibcode: 2006IAUJD...3E..86V Altcode: Introduction: A series of flares (GOES class M, M and C) and a CME were observed on 20-JAN-2004 occurring in close succession in NOAA 10540. Types II, III and a N radio bursts were associated. We investigate the link between the flares (two impulsive flares followed by an LDE) and the CME as well as the origin of the rare decametric N-burst. Methods: We use the combined observations from TRACE, SOHO/EIT, H-alpha images from Kwasan Observatory, SOHO/MDI magnetograms, GOES and radio observations from Culgoora and Wind/WAVES as well as magnetic modelling to understand the complex development of this event. Results: We link the first two impulsive flares to tether-cutting reconnections and the launch of the CME, while the last of the flares, an LDE, to the relaxation phase following forced reconnections between the erupting flux rope and neighbouring magnetic field lines. We show that reconnection with the magnetic structure of a previous CME, launched about 8 hours earlier, injects electrons into open field lines having a local dip and apex of about 6 solar radii height. The dipped shape of these field lines was due to large-scale magnetic reconnection between expanding magnetic loops and open field lines of a neighbouring streamer. This particular situation explains the observed decametric N burst. Discussion: This complex observation shows that impulsive quadrupolar flares can be eruptive, while an LDE may remain a confined event. We find that reconnection forced by the expanding CME structure is followed by a relaxation phase, when reconnection reverses and restores some of the pre-eruption magnetic connectivities. The observed decametric N-burst was caused by the interaction of two CMEs and reconnection of their expanding magnetic field with neighbouring streamer field lines - a very particular interplay, which explains why N-bursts are so rare. Title: Magnetic Fields and Large-Scale SXR and EUV Coronal Structures Authors: van Driel-Gesztelyi, Lidia Bibcode: 2006IAUS..233..205V Altcode: An overview is presented of large-scale coronal structures as observed in soft X-rays (SXR) and extreme ultraviolet (EUV) wavelengths in the context of their magnetic properties. These structures include large-scale interconnecting and trans-equatorial loops, coronal streamers, coronal holes, filaments and filament channels. Since the general appearance of the corona and its structures change with evolving underlying fields, evolutionary trends and solar cycle dependence of these coronal structures are discussed as well. Title: Editorial Appreciation Authors: Engvold, Oddbjørn; Harvey, Jack; Leibacher, John; Sakurai, Takashi; Švestka, Zdeněk; van Driel-Gesztelyi, Lidia; Solar Physics editors Bibcode: 2006SoPh..233....1E Altcode: No abstract at ADS Title: Combined analysis of the 15-16 May, 1997, magnetic cloud and of its solar source region Authors: Nakwacki, M. S.; Atrill, G.; Dasso, S.; Mandrini, C. H.; van Driel-Gesztelyi, L.; Harra, L.; Wang, J. Bibcode: 2006BAAA...49...46N Altcode: In this work we analise the structure of the magnetic cloud (MC) observed by Wind between 15-16 May 1997, and the related solar event, a long duration C1.3 flare which ocurred on 12 May 1997. This event presented two dark regions in EUV (dimmings) with asymmetric evolution. The magnetic structure of the MC was modeled using three cylindrical helicoidal models, considering the asymmetry between its front and its final part. We calculate the magnetic flux in the dimmings and their evolution, and the flux through the surface perpendicular to the cloud axis and to the azimuthal direction. Finally, we compare the total flux of both, MC and dimmings, and propose a topological model for the solar event. FULL TEXT IN SPANISH Title: A combined analysis of the magnetic cloud on 15-16 May 1997 and its solar source region Authors: Nakwacki, M. S.; Attrill, G.; Dasso, S.; Mandrini, C. H.; van Driel-Gesztelyi, L.; Harra, L. K.; Wang, J. Bibcode: 2006cosp...36.2479N Altcode: 2006cosp.meet.2479N Coronal Mass Ejections CMEs are the most important short-lived agents that transport magnetic flux from the Sun to the interplanetary medium Thus detailed studies of the solar sources of CMEs and the associated magnetic clouds MCs are an important key to understand and constrain solar and interplanetary models We analyze the magnetic structure of the MC observed on 15-16 May 1997 by the spacecraft Wind and its associated solar event a C1 3 long duration event that occurred on 12 May 1997 in AR8038 Two main dimming regions that exhibit an asymmetric temporal and spatial evolution were observed in association with this event We compute the magnetic flux in the dimmings and follow its evolution using magnetograms from the Michelson Doppler Imager SoHO MDI The MC structure is inferred using three different helical cylindrical models with a significantly different radial twist distribution We also take into account the asymmetry observed between the front and the rear part of the cloud We fit the free parameters of each model comparing models with in situ observations Then we estimate the flux across the surface perpendicular to the axis of the cylinder and the flux across the surface formed by this axis and the cloud radial direction Finally we compare the MC total flux with that corresponding to both observed dimmings By combining our interplanetary measurements and the dimmings flux evolution we propose a topological model for the 12 May eruptive event We discuss the constrains set by solar observations on Title: Multi-scale reconnections in a complex CME Authors: van Driel-Gesztelyi, L.; Goff, C.; Demoulin, P.; Culhane, J. L.; Matthews, S. A.; Harra, L. K.; Mandrini, C. H.; Klein, K. L.; Kurokawa, H. Bibcode: 2006cosp...36.2371V Altcode: 2006cosp.meet.2371V A series of flares GOES class M M and C and a CME were observed on 20-JAN-2004 occurring in close succession in NOAA 10540 Types II III and an N radio bursts were associated We use the combined observations from TRACE EIT H-alpha images from Kwasan Observatory MDI magnetograms GOES and radio observations from Culgoora and Wind WAVES to understand the complex development of this event We link the first two impulsive flares to tether-cutting reconnections and the launch of the CME while the last of the flares an LDE to the relaxation phase following forced reconnections between the erupting flux rope and neighbouring magnetic field lines We show that reconnection with the magnetic structure of a previous CME launched about 8 hours earlier injects electrons into open field lines having a local dip and apex of about 6 solar radii height The dipped shape of these field lines was due to large-scale magnetic reconnection between expanding magnetic loops and open field lines of a neighbouring streamer This particular situation explains the observed decametric N burst and why N-bursts are so rare Title: Sun-to-earth propagation speeds for three CMEs Authors: Culhane, L.; Pohjolainen, S.; van Driel-Gesztelyi, L.; Elliott, H. Bibcode: 2006cosp...36.2544C Altcode: 2006cosp.meet.2544C Several methods for CME speed estimation are discussed for events that occurred on 28-OCT-2003 7-NOV-2004 and 20-JAN-2005 These include velocity derivation based on the frequency drifts observed in metric and decametric radio wave data using a range of coronal density models These estimated speeds are compared with plane of the sky values and with estimates made from the application of a cone model The related interplanetary shocks and the arrival times of the associated magnetic clouds at Earth are also considered The range of speeds and Sun-Earth transit times obtained from these studies is assessed The difficulties in making velocity estimates from radio observations particularly under disturbed coronal conditions will be highlighted Title: The MOSES spectral imager for KuaFu-A Authors: Harra, L. K.; van Driel-Gesztelyi, L.; Cole, R.; Sun, J.; Winter, B.; Hancock, B. Bibcode: 2006cosp...36.3670H Altcode: 2006cosp.meet.3670H We will describe the instrument design for a spectral imager on the KuaFu mission KuaFu s science goals are aimed at understanding space weather with a spacecraft located at L1 and 2 spacecraft in a polar orbit around the Earth The spectral imager will provide crucial information on the source region of coronal mass ejections It will achieve this by measuring the Doppler velocities and intensity over the field of view of the solar activity zone which is geoeffective This allows us to determine whether activity on the Sun does actually releases material into the interplanetary medium BEFORE we observe it in coronagraphs We will summarise the instrument design and the scientific drivers for it Title: Tracing magnetic helicity from the solar corona to the interplanetary space Authors: Luoni, M. L.; Mandrini, C. H.; Dasso, Sergio; van Driel-Gesztelyi, L.; Démoulin, P. Bibcode: 2005JASTP..67.1734L Altcode: 2005JATP...67.1734L On October 14, 1995, a C1.6 long duration event (LDE) started in active region (AR) NOAA 7912 at approximately 5:00 UT and lasted for about 15 h. On October 18, 1995, the Solar Wind Experiment and the Magnetic Field Instrument (MFI) on board the Wind spacecraft registered a magnetic cloud (MC) at 1 AU, which was followed by a strong geomagnetic storm. We identify the solar source of this phenomenon as AR 7912. We use magnetograms obtained by the Imaging Vector Magnetograph at Mees Solar Observatory, as boundary conditions to the linear force-free model of the coronal field, and, we determine the model in which the field lines best fit the loops observed by the Soft X-ray Telescope on board Yohkoh. The computations are done before and after the ejection accompanying the LDE. We deduce the loss of magnetic helicity from AR 7912. We also estimate the magnetic helicity of the MC from in situ observations and force-free models. We find the same sign of magnetic helicity in the MC and in its solar source. Furthermore, the helicity values turn out to be quite similar considering the large errors that could be present. Our results are a first step towards a quantitative confirmation of the link between solar and interplanetary phenomena through the study of magnetic helicity. Title: Erupting Flux Rope, Rising X-Ray Source and a Slow CME on 16 April 2002 Authors: Goff, C. P.; van Driel-Gesztelyi, L.; Harra, L. K.; Matthews, S. A.; Mandrini, C. H. Bibcode: 2005ESASP.600E..46G Altcode: 2005ESPM...11...46G; 2005dysu.confE..46G No abstract at ADS Title: Relating Near-Earth Observations of AN Interplanetary Coronal Mass Ejection to the Conditions at its Site of Origin in the Solar Corona Authors: Fazakerley, A. N.; Harra, L. K.; Culhane, J. L.; van Driel-Gesztelyi, L.; Lucek, E.; Matthews, S. A.; Owen, C. J.; Mazelle, C.; Balogh, A.; Réme, H. Bibcode: 2005ESASP.600E..47F Altcode: 2005dysu.confE..47F; 2005ESPM...11...47F No abstract at ADS Title: Quantitative Link Between Solar Ejecta and Interplanetary Magnetic Clouds: Magnetic Helicity Authors: Mandrini, C. H.; Dasso, S.; Luoni, M. L.; Pohjolainen, S.; Démoulin, P.; van Driel-Gesztelyi, L. Bibcode: 2005ESASP.596E..29M Altcode: 2005ccmf.confE..29M No abstract at ADS Title: Linking Coronal to Heliospheric Magnetic Helicity: A New Model-Independent Technique to Compute Helicity in Magnetic Clouds Authors: Dasso, Sergio; Mandrini, Cristina H.; Luoni, Maria L.; Gulisano, Adriana M.; Nakwacki, Maria S.; Pohjolainen, Silja; van Driel-Gesztelyi, Lidia; Démoulin, Pascal Bibcode: 2005ESASP.592..605D Altcode: 2005soho...16E.117D; 2005ESASP.592E.117D No abstract at ADS Title: Flows in the solar atmosphere due to the eruptions on the 15th July, 2002 Authors: Harra, L. K.; Démoulin, P.; Mandrini, C. H.; Matthews, S. A.; van Driel-Gesztelyi, L.; Culhane, J. L.; Fletcher, L. Bibcode: 2005A&A...438.1099H Altcode: Which kind of flows are present during flares? Are they compatible with the present understanding of energy release and which model best describes the observations? We analyze successive flare events in order to answer these questions. The flares were observed in the magnetically complex NOAA active region (AR) 10030 on 15 July 2002. One of them is of GOES X-class. The description of these flares and how they relate to the break-out model is presented in Gary & Moore (2004). The Coronal Diagnostic Spectrometer on board SOHO observed this active region for around 14 h. The observed emission lines provided data from the transition region to the corona with a field of view covering more than half of the active region. In this paper we analyse the spatially resolved flows seen in the atmosphere from the preflare to the flare stages. We find evidence for evaporation occurring before the impulsive phase. During the main phase, the ongoing magnetic reconnection is demonstrated by upflows located at the edges of the flare loops (while downflows are found in the flare loops themselves). We also report the impact of a filament eruption on the atmosphere, with flows up to 300 km s-1 observed at transition-region temperatures in regions well away from the location of the pre-eruptive filament. Our results are consistent with the predictions of the break out model before the impulsive phase of the flare; while, as the flare progresses, the directions of the flows are consistent with flare models invoking evaporation followed by cooling and downward plasma motions in the flare loops. Title: Eruption of a Kink-unstable Filament in NOAA Active Region 10696 Authors: Williams, David R.; Török, Tibor; Démoulin, Pascal; van Driel-Gesztelyi, Lidia; Kliem, Bernhard Bibcode: 2005ApJ...628L.163W Altcode: 2005astro.ph..7661W We present rapid-cadence Transition Region and Coronal Explorer (TRACE) observations that show evidence of a filament eruption from NOAA active region 10696, accompanied by an X2.5 flare, on 2004 November 10. The eruptive filament, which manifests as a fast coronal mass ejection some minutes later, rises as a kinking structure with an apparently exponential growth of height within TRACE's field of view. We compare the characteristics of this filament eruption with MHD numerical simulations of a kink-unstable magnetic flux rope, finding excellent qualitative agreement. We suggest that while tether weakening by breakout-like quadrupolar reconnection may be the release mechanism for the previously confined flux rope, the driver of the expansion is most likely the MHD helical kink instability. Title: Relating near-Earth observations of an interplanetary coronal mass ejection to the conditions at its site of origin in the solar corona Authors: Fazakerley, A. N.; Harra, L. K.; Culhane, J. L.; van Driel-Gesztelyi, L.; Lucek, E.; Matthews, S. A.; Owen, C. J.; Mazelle, C.; Balogh, A.; Rème, H. Bibcode: 2005GeoRL..3213105F Altcode: A halo coronal mass ejection (CME) was detected on January 20, 2004. We use solar remote sensing data (SOHO, Culgoora) and near-Earth in situ data (Cluster) to identify the CME source event and show that it was a long duration flare in which a magnetic flux rope was ejected, carrying overlying coronal arcade material along with it. We demonstrate that signatures of both the arcade material and the flux rope material are clearly identifiable in the Cluster and ACE data, indicating that the magnetic field orientations changed little as the material traveled to the Earth, and that the methods we used to infer coronal magnetic field configurations are effective. Title: Editorial Authors: Leibacher, John; Sakurai, Takashi; van Driel-Gesztelyi, Lidia Bibcode: 2005SoPh..229....3L Altcode: No abstract at ADS Title: A slow coronal mass ejection with rising X-ray source Authors: Goff, C. P.; van Driel-Gesztelyi, L.; Harra, L. K.; Matthews, S. A.; Mandrini, C. H. Bibcode: 2005A&A...434..761G Altcode: An eruptive event, which occurred on 16th April 2002, is discussed. Using images from the Transition Region and Coronal Explorer (TRACE) at 195 Å, we observe a lifting flux rope which gives rise to a slow coronal mass ejection (CME). There are supporting velocity observations from the Coronal Diagnostic Spectrometer (CDS) on the Solar and Heliospheric Observatory (SOHO), which illustrate the helical nature of the structure. Additionally a rising coronal hard X-ray source, which is observed with the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI), is shown to follow the flux rope with a speed of ~60 km s-1. It is also sampled by the CDS slit, although it has no signature in the Fe XIX band. Following the passage of this source, there is evidence from the CDS for down-flowing (cooling) material along newly reconnected loops through Doppler velocity observations, combined with magnetic field modeling. Later, a slow CME is observed with the Large Angle and Spectroscopic Coronagraph (LASCO). We combine a height-time profile of the flux rope at lower altitudes with the slow CME. The rising flux rope speeds up by a factor of 1.7 at the start of the impulsive energy release and goes through further acceleration before reaching 1.5 solar radii. These observations support classical CME scenarios in which the eruption of a filament precedes flaring activity. Cusped flare loops are observed following the erupting flux rope and their altitude increases with time. In addition we find RHESSI sources both below and above the probable location of the reconnection region. Title: Interplanetary flux rope ejected from an X-ray bright point. The smallest magnetic cloud source-region ever observed Authors: Mandrini, C. H.; Pohjolainen, S.; Dasso, S.; Green, L. M.; Démoulin, P.; van Driel-Gesztelyi, L.; Copperwheat, C.; Foley, C. Bibcode: 2005A&A...434..725M Altcode: Using multi-instrument and multi-wavelength observations (SOHO/MDI and EIT, TRACE and Yohkoh/SXT), as well as computing the coronal magnetic field of a tiny bipole combined with modelling of Wind in situ data, we provide evidences for the smallest event ever observed which links a sigmoid eruption to an interplanetary magnetic cloud (MC). The tiny bipole, which was observed very close to the solar disc centre, had a factor one hundred less flux than a classical active region (AR). In the corona it had a sigmoidal structure, observed mainly in EUV, and we found a very high level of non-potentiality in the modelled magnetic field, 10 times higher than we have ever found in any AR. From May 11, 1998, and until its disappearance, the sigmoid underwent three intense impulsive events. The largest of these events had extended EUV dimmings and a cusp. The Wind spacecraft detected 4.5 days later one of the smallest MC ever identified (about a factor one hundred times less magnetic flux in the axial component than that of an average MC). The link between this last eruption and the interplanetary magnetic cloud is supported by several pieces of evidence: good timing, same coronal loop and MC orientation, same magnetic field direction and magnetic helicity sign in the coronal loops and in the MC. We further quantify this link by estimating the magnetic flux (measured in the dimming regions and in the MC) and the magnetic helicity (pre- to post-event change in the solar corona and helicity content of the MC). Within the uncertainties, both magnetic fluxes and helicities are in reasonable agreement, which brings further evidences of their link. These observations show that the ejections of tiny magnetic flux ropes are indeed possible and put new constraints on CME models. Title: Relationship between X-ray and ultraviolet emission of flares from dMe stars observed by XMM-Newton Authors: Mitra-Kraev, U.; Harra, L. K.; Güdel, M.; Audard, M.; Branduardi-Raymont, G.; Kay, H. R. M.; Mewe, R.; Raassen, A. J. J.; van Driel-Gesztelyi, L. Bibcode: 2005A&A...431..679M Altcode: 2004astro.ph.10592M We present simultaneous ultraviolet and X-ray observations of the dMe-type flaring stars AT Mic, AU Mic, EV Lac, UV Cet and YZ CMi obtained with the XMM-Newton observatory. During 40 h of simultaneous observation we identify 13 flares which occurred in both wave bands. For the first time, a correlation between X-ray and ultraviolet flux for stellar flares has been observed. We find power-law relationships between these two wavelength bands for the flare luminosity increase, as well as for flare energies, with power-law exponents between 1 and 2. We also observe a correlation between the ultraviolet flare energy and the X-ray luminosity increase, which is in agreement with the Neupert effect and demonstrates that chromospheric evaporation is taking place. Title: Coronal Mass Ejections and Magnetic Helicity Authors: Van Driel-Gesztelyi, L. Bibcode: 2005ASSL..320...57V Altcode: 2005smp..conf...57V No abstract at ADS Title: The smallest source region of an interplanetary magnetic cloud: A mini-sigmoid Authors: Mandrini, C. H.; Pohjolainen, S.; Dasso, S.; Green, L. M.; Démoulin, P.; van Driel-Gesztelyi, L.; Foley, C.; Copperwheat, C. Bibcode: 2005AdSpR..36.1579M Altcode: We provide evidence for the smallest sigmoid eruption - CME - interplanetary magnetic cloud event ever observed by combining multi-wavelength remote sensing and in situ observations, as well as computing the coronal and interplanetary magnetic fields. The tiny bipole had 100 times less flux than an average active region (AR). It had a sigmoidal structure in the corona and we detected a very high level of twist in its magnetic field. On 11 May 1998, at about 8 UT, the sigmoid underwent eruption evidenced by expanding elongated EUV loops, dimmings and formation of a cusp. The Wind spacecraft, 4.5 days later, detected one of the smallest magnetic clouds (MC) ever identified (100 times less magnetic flux than an average MC). The link between the EUV bright point eruption and the interplanetary MC is supported by several pieces of evidence: timing, same coronal loop and MC orientation relative to the ecliptic, same magnetic field direction and magnetic helicity sign in the coronal loops and in the MC, comparable magnetic flux measured in the dimming regions and in the interplanetary MC and, most importantly, the pre- to post-event change of magnetic helicity in the solar corona is found to be comparable to the helicity content of the cloud. Title: Source Regions of Coronal Mass Ejections Authors: Schmieder, Brigitte; van Driel-Gesztelyi, L. Bibcode: 2005IAUS..226..149S Altcode: The majority of flare activity arises in active regions which contain sunspots, while CME activity can also originate from decaying active regions and even so-called quiet solar regions which contain a filament. Two classes of CME, namely flare-related CME events and CMEs associated with filament eruption are well reflected in the evolution of active regions, flare related CMEs mainly occur in young active regions containing sunspots and as the magnetic flux of active region is getting dispersed, the filament-eruption related CMEs will become dominant. This is confirmed by statistical analyses.</p>All the CMEs are, nevertheless, caused by loss of equilibrium of the magnetic structure. With observational examples we show that the association of CME, flare and filament eruption depends on the characteristics of the source regions: (i) the strength of the magnetic field, the amount of possible free energy storage, (ii) the small- and large-scale magnetic topology of the source region as well as its evolution (new flux emergence, photospheric motions, canceling flux), and (iii) the mass loading of the configuration (effect of gravity). These examples are discussed in the framework of theoretical models. Title: Linking Coronal to Interplanetary Magnetic Helicity Authors: Luoni, M. L.; Dasso, S.; Mandrini, C. H.; Van Driel-Gesztelyi, L.; Démoulin, P. Bibcode: 2005ASSL..320..243L Altcode: 2005smp..conf..243L No abstract at ADS Title: Solar and Interplanetary Magnetic Helicity Balance of Active Regions Authors: Mandrini, Cristina H.; Démoulin, Pascal; van Driel-Gesztelyi, Lidia; Dasso, Sergio; Green, Lucinda M.; López Fuentes, Marcelo Bibcode: 2005HiA....13..122M Altcode: No abstract at ADS Title: Relating magnetic field strengths to hard X-ray emission in solar flares Authors: Goff, C. P.; Matthews, S. A.; van Driel-Gesztelyi, L.; Harra, L. K. Bibcode: 2004A&A...423..363G Altcode: The observation of hard X-ray (HXR) emission in solar flares provides important diagnostic information about the acceleration and subsequent transport of energetic electrons in the flare process. However, while hard X-rays are thought to be emitted from the flare footpoints through thick-target bremsstrahlung interactions, the details of the transport of accelerated electrons through the solar atmosphere still remains unclear.

Trapping of the electrons is one particular effect that is expected to occur as a result of the convergence of the magnetic field between the corona and the chromosphere. In this case the brightness of the HXR footpoints should be related to the strength of the magnetic field present and we would expect greater precipitation and higher HXR intensities at the footpoints with lower magnetic field strength. This relationship has been observed to hold in many flares (see \citealt{Sakaothesis}) but interestingly the opposite relationship, where the stronger HXR source is found at the stronger magnetic field region, has also been observed in an event studied by \citet{Asai}.

Using Data from Yohkoh's Hard X-Ray Telescope (HXT) and SOHO's Michelson Doppler Imager (MDI) we have studied the magnetic field strengths at the footpoints of a sample of 32 flares and have compared them to the hard X-ray brightness to determine whether the expected ratios are seen. We find that contrary to the expected relationship the brighter HXR footpoint is found in the region of stronger magnetic field in approximately one third of our sample of events. We discuss the implications of these results in terms of the transport mechanisms. Title: Intensity variations in EIT shutterless mode: Waves or flows? Authors: De Groof, A.; Berghmans, D.; van Driel-Gesztelyi, L.; Poedts, S. Bibcode: 2004A&A...415.1141D Altcode: On 11 July 2001 an EIT shutterless campaign was conducted which provided 120 high-cadence (68 s) 304 Å images of the north eastern quarter of the Sun. The most interesting feature seen in the data is an off-limb half loop structure along which systematic intensity variations are seen which appear to propagate from the top of the loop towards its footpoint. We investigate the underlying cause of these propagating disturbances, i.e. whether they are caused by waves or by plasma flows. First we identify 7 blobs with the highest intensities and follow them along the loop. By means of a location-time plot, bulk velocities can be measured at several locations along the loop. The velocity curve found this way is then compared with characteristic wave speeds and with the free-fall speed in order to deduce the nature of the intensity variations. Additional information on density and temperature is derived by measuring the relative intensity enhancements and comparing the EIT 304 Å sequence with Big Bear data and 171 Å data (TRACE/EIT). The combination of all these constraints gives us an insight on the nature and origin of these intensity variations. The idea of slow magneto-acoustic waves is rejected, and we find several arguments supporting that these intensity variations are due to flowing/falling plasma blobs. Title: Magnetic Helicity Budget of Solar-Active Regions from the Photosphere to Magnetic Clouds Authors: Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.; van Driel-Gesztelyi, L.; van Driel-Gesztelyi, L.; van Driel-Gesztelyi, L. L. M.; López Fuentes, M. C. Bibcode: 2004Ap&SS.290..319M Altcode: We have analyzed the long-term evolution of two active regions (ARs) from their emergence through their decay using observations from several instruments on board SoHO (MDI, EIT and LASCO) and Yohkoh/SXT. We have computed the evolution of the relative coronal magnetic helicity combining data from MDI and SXT with a linear force-free model of the coronal magnetic field. Next, we have computed the injection of helicity by surface differential rotation using MDI magnetic maps. To estimate the depletion of helicity we have counted all the CMEs of which these ARs have been the source, and we have evaluated their magnetic helicity assuming a one to one correspondence with magnetic clouds with an average helicity contain. When these three values (variation of coronal magnetic helicity, injection by differential rotation and ejection via CMEs) are compared, we find that surface differential rotation is a minor contributor to the helicity budget since CMEs carry away at least 10 times more helicity than the one differential rotation can provide. Therefore, the magnetic helicity flux needed in the global balance should come from localized photospheric motions that, at least partially, reflect the emergence of twisted flux tubes. We estimate that the total helicity carried away in CMEs can be provided by the end-to-end helicity of the flux tubes forming these ARs. Therefore, we conclude that most of the helicity ejected in CMEs is generated below the photosphere and emerges with the magnetic flux. Title: Evidence of Magnetic Reconnection along Coronal Hole Boundaries Authors: Madjarska, M. S.; Doyle, J. G.; van Driel-Gesztelyi, L. Bibcode: 2004ApJ...603L..57M Altcode: The present study reveals for the first time the existence of bidirectional jets, which are a signature of magnetic reconnection, occurring along coronal hole boundaries. The Solar Ultraviolet Measurement of Emitted Radiation spectrometer observations obtained in the N IV 765.15 Å (1.3×105 K) and Ne VIII 770.42 Å (6×105 K) emission lines in an equatorial extension of a polar coronal hole, known as the ``Elephant's Trunk'' coronal hole, show small regions of a few arcseconds size with strong blue- and redshifted emission reaching Doppler shifts of up to 150 km s-1, i.e., bidirectional jets. The jets' number density along coronal hole boundaries was found to be about 4-5 times higher with respect to the quiet Sun. Title: An Observational Test for Coronal Heating Models Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Mandrini, C. H.; Harra, L. K.; Klimchuk, J. A. Bibcode: 2004IAUS..219..473V Altcode: 2003IAUS..219E..97V We correlate the evolution of the mean X-ray flux emission measure and temperature (Yohkoh SXT & BCS) with the magnetic flux density (SOHO/MDI) in active region NOAA 7978 from its birth throughout its decay for five solar rotations. We show that these plasma parameters together with other quantities deduced from them such as the density and the pressure follow power-law relationships with the mean magnetic flux density (bar{B}). We derive the dependence of the mean coronal heating rate on the magnetic flux density. We use the obtained scaling laws of coronal loops in thermal equilibrium to derive observational estimates of the scaling of the coronal heating with bar{B}. These results are used to test the validity of coronal heating models. We find that models invoking stochastic buildup of energy current layers and MHD turbulence are in best agreement with the observations. This narrows down the range of possible models retained by previous results obtained for individual coronal loops as well as for the global coronal emission of the Sun and cool stars. Title: Bi-Directional Jets at Coronal Hole Boundaries Authors: Madjarska, M. S.; Doyle, J. G.; van Driel-Gesztelyi, L. Bibcode: 2004ESASP.547..397M Altcode: 2004soho...13..397M Our study reveals, for the first time, the presence of bi-directional jets which are considered to be signatures of magnetic reconnection occurring along coronal hole boundaries. The SUMER observations obtained in Ne VIII 770.42 Å (6 10 K) and N IV 765.15 Å (1.3 10 K) show small regions of a few arcsec size with strong blueand red-shifted emission reaching Doppler shifts up to 150 km s which appear along the coronal hole boundaries where evolving loop systems are present. Title: Intensity Variations in EIT Shutterless Mode: Waves or Flows? Authors: de Groof, A.; Berghmans, D.; van Driel-Gesztelyi, L.; Poedts, S. Bibcode: 2004ESASP.547..245D Altcode: 2004soho...13..245D On 11 July 2001 an EIT shutterless campaign was conducted which provided 120 high-cadence (68s) 304 Å images of the north eastern quarter of the Sun. The most interesting feature seen in the data is an off-limb half loop structure along which systematic intensity variations appear to propagate from the top of the loop towards its footpoint. We investigate the underlying cause of these propagating disturbances, i.e. whether they are caused by waves or by plasma flows. First we identify 7 blobs with the highest intensities and follow them along the loop. By means of a location-time plot, bulk velocities can be measured at several locations along the loop. The velocity curve found this way is then compared with characteristic wave speeds and with the free-fall speed in order to deduce the nature of the intensity variations. Additional information is derived by measuring the relative intensity enhancements and comparing the EIT 304 Å sequence with Big Bear and 171 Å data. The idea of slow magneto-acoustic waves is rejected, and we find several arguments supporting that these intensity variations are due to flowing/falling plasma blobs. Title: Linking coronal observations of a `mini´active region with its interplanetary manifestation Authors: Dasso, S.; Mandrini, C. H.; Pohjolainen, S.; Green, L. M.; Démoulin, P.; van Driel-Gesztelyi, L.; Foley, C.; Copperwheat, C. Bibcode: 2004BAAA...47...18D Altcode: We analyze the smallest 'sigmoidal eruption - CME - interplanetary magnetic cloud' event even observed before. We find: (a) the same magnetic helicity sign and (b) similar magnetic flux values in the coronal source region and associated cloud, and (c) that the magnetic helicity changes, before and after the ejection, in approximately the same amount as the helicity content in the interplanetary cloud. These results stress the importance of complementary solar and interplanetary studies, to achieve a better understanding of the origin of eruptive phenomena. Title: Flux Cancellation in a Decaying Active Region Authors: Martinez Pillet, V.; Sainz Dalda, A.; van Driel-Gesztelyi, L. Bibcode: 2004cosp...35.1133M Altcode: 2004cosp.meet.1133M Flux Cancellation in a Decaying Active Region Flux cancellation is observed in many regions on the Sun as internetwork, network and active regions fields. It clearly plays a crucial role in the constant flux processing observed in the solar surface. During the decay of an active region, we have observed the in-situ dissapearance of 70 % of its flux (from SOHO/MDI). Active region flux decay is a global, large-scale, process crucial to the solar cycle. But the flux cancellations, where the flux actually disappears, do take place in very small scale regions. There opposite polarities meet and vanish. The process needs of observations with sufficient sensitivity and angular resolution. In the example presented here, we show how up to 4 of these cancellations are associated with outward moving material in the Corona (as observed by TRACE), including a major active region filament eruption. Solar Orbiter, profiting from the advantage observing position and near-corotation can follow these subtle, but crucial, processes with the necessary set of instruments: Magnetographs, Coronal imagers and spectrographs. For those events occurring in the spacecraft solar vertical, one should not exclude the detection of the phenomena in the in-situ instruments. Title: The smallest source region of an interplanetary magnetic cloud: a mini-sigmoid Authors: Mandrini, C.; Pohjolainen, S.; Dasso, S.; Green, L.; Demoulin, P.; van Driel-Gesztelyi, L.; Copperwheat, C.; Foley, C. Bibcode: 2004cosp...35..290M Altcode: 2004cosp.meet..290M Using multi-instrument and multi-wavelength observations (SOHO/MDI and EIT, TRACE and Yohkoh/SXT), as well as computing the coronal magnetic field of a tiny bipole combined with modelling of WIND in situ data, we provide evidence for the smallest sigmoid eruption - CME - interplanetary magnetic cloud event ever observed. The tiny bipole, which was observed very close to the solar disc centre, had 100 times less flux than an average active region (AR). In the corona it had a sigmoidal structure and we detected a very high level of twist. On 11 May 1998, at about 8 UT, the sigmoid underwent eruption evidenced by expanding elongated EUV loops, dimmings and formation of a cusp. The WIND spacecraft detected 4.5 days later one of the smallest magnetic clouds (MC) ever identified (100 times less flux and radius than an average MC). The link between the sigmoidal EUV bright point eruption and the interplanetary magnetic cloud is supported by several pieces of evidence: good timing, same coronal loop and MC orientation relative to the ecliptic, same magnetic field direction and magnetic helicity sign in the coronal loops and in the MC, comparable magnetic flux measured in the dimming regions and in the interplanetary MC and, most importantly, the pre- to post-event change of magnetic helicity in the solar corona is found to be similar to the helicity content of the cloud, when assuming a length compatible with the fact that the cloud can be detached from the Sun one day after its ejection. These observations are a challenge to present theoretical CME models, and show us the need of missions such us Solar B and Stereo to contribute to our understanding of the broad spectrum covered by solar eruptive phenomena. Title: How small can an interplanetary magnetic cloud source-region be? Authors: Mandrini, C.; Pohjolainen, S.; Dasso, S.; Green, L.; Demoulin, P.; van Driel-Gesztelyi, L.; Copperwheat, C.; Foley, C. Bibcode: 2004cosp...35..282M Altcode: 2004cosp.meet..282M Using multi-instrument and multi-wavelength observations (SOHO/MDI and EIT, TRACE and Yohkoh/SXT), as well as computing the coronal magnetic field of a tiny bipole combined with modelling of WIND in situ data, we provide evidence for the smallest sigmoid eruption - CME - interplanetary magnetic cloud event ever observed. The tiny bipole, which was observed very close to the solar disc centre, had 100 times less flux than an average active region (AR). In the corona it had a sigmoidal structure and we detected a very high level of twist. On 11 May 1998, at about 8 UT, the sigmoid underwent eruption evidenced by expanding elongated EUV loops, dimmings and formation of a cusp. The WIND spacecraft detected 4.5 days later one of the smallest magnetic clouds (MC) ever identified (100 times less flux and radius than an average MC). The link between the sigmoidal EUV bright point eruption and the interplanetary magnetic cloud is supported by several pieces of evidence: good timing, same coronal loop and MC orientation relative to the ecliptic, same magnetic field direction and magnetic helicity sign in the coronal loops and in the MC, comparable magnetic flux measured in the dimming regions and in the interplanetary MC and, most importantly, the pre- to post-event change of magnetic helicity in the solar corona is found to be similar to the helicity content of the cloud, when assuming a length compatible with the fact that thecloud can be dettached from the Sun one day after its ejection. These observations are a challenge to present theoretical CME models, and show us the need of missions such us Solar B and Stereo to contribute to our understandig of the broad spectrum covered by solar eruptive phenomena. Title: An Introduction to Magnetohydrodynamics Authors: van Driel-Gesztelyi, Lidia Bibcode: 2004spsc.book..279V Altcode: No abstract at ADS Title: The possible back-rotation of sunspots Authors: Williams, D. R.; van Driel-Gesztelyi, L.; Nakariakov, V. M. Bibcode: 2004cosp...35.4391W Altcode: 2004cosp.meet.4391W The curious case of sunspot rotation in two senses, presented by Kucera (1982), provided an interesting challenge to the idea of sunspot rotation being due simply to the differential rotation of the Sun above the tachocline. As the rotation rate and direction, in that case, are seen to vary as a damped sinusoid, this presents the possibility that such motion is the result of torsional waves trapped in the sunspot's sub-photospheric flux tube. We therefore analyse the rotation of a number of sunspots using SoHO/MDI and track their rotation, presenting evidence of 'back-rotation' -- rotational motion which reverses -- in a several of these spots. Intuitively, this raises the possibility of extending the field of 'Coronal Seismology' back down to beneath the photosphere (where helioseismology already exists). Title: Evidence of Flaring in a Transequatorial Loop on the Sun Authors: Harra, Louise K.; Matthews, Sarah A.; van Driel-Gesztelyi, Lidia Bibcode: 2003ApJ...598L..59H Altcode: We present evidence of flaring behavior in a transequatorial loop (TEL) that lights up in soft X-rays on 2000 July 13. The large loop structure connects NOAA Active Regions 9070/9066 in the northern hemisphere and AR 9069/9068 in the southern hemisphere. We follow the loop systems for 2 days and observe several pieces of evidence strongly suggesting flare behavior of the form seen in standard flaring in active regions. These include brightenings of the loop structure, cooling of plasma that is seen both in soft X-rays and in the transition region temperatures, morphological evidence of reconnection inflow, and blueshifts around the footpoint of the TEL suggestive of chromospheric evaporation. We present, to our knowledge for the first time, observations of TEL in the O V emission line. Title: A catalogue of white-light flares observed by Yohkoh Authors: Matthews, S. A.; van Driel-Gesztelyi, L.; Hudson, H. S.; Nitta, N. V. Bibcode: 2003A&A...409.1107M Altcode: The aspect camera of the Soft X-ray Telescope (SXT) on Yohkoh provided the first systematic survey of white-light flares from an observatory in space. The observations were made in the Fraunhofer g-band at a pixel size of 2.46 arcsec and a typical sample interval on the order of ten seconds. A total of 28 flares with clear white-light signatures were detected, corresponding to GOES events down to the C7.8 level in one case. Above the X-class threshold, all 5 events observed by SXT were observed in white light, and the maximum average contrast observed was 30% relative to the pre-flare continuum brightness of the flare location. We have made comprehensive comparisons of Yohkoh soft X-ray and hard X-ray data for this list of flares. In addition we compare the properties of the WLF sample to a sample of 31 flares that showed no white-light emission. These comparisons show that while white-light continuum emission has a strong association with hard X-ray emission it is also strongly related to coronal overpressure, as determined from the soft X-ray spectrum, indicating a component with a thermal, rather than non-thermal origin.

Appendices are only available in electronic form at http://www.edpsciences.org Title: How are Emerging Flux, Flares and CMEs Related to Magnetic Polarity Imbalance in Midi Data? Authors: Green, L. M.; Démoulin, P.; Mandrini, C. H.; Van Driel-Gesztelyi, L. Bibcode: 2003SoPh..215..307G Altcode: 2003astro.ph..4092G In order to understand whether major flares or coronal mass ejections (CMEs) can be related to changes in the longitudinal photospheric magnetic field, we study 4 young active regions during seven days of their disk passage. This time period precludes any biases which may be introduced in studies that look at the field evolution during the short-term flare or CME period only. Data from the Michelson Doppler Imager (MDI) with a time cadence of 96 min are used. Corrections are made to the data to account for area foreshortening and angle between line of sight and field direction, and also the underestimation of the flux densities. We make a systematic study of the evolution of the longitudinal magnetic field, and analyze flare and CME occurrence in the magnetic evolution. We find that the majority of CMEs and flares occur during or after new flux emergence. The flux in all four active regions is observed to have deviations from polarity balance both on the long term (solar rotation) and on the short term (few hours). The long-term imbalance is not due to linkage outside the active region; it is primarily related to the east-west distance from central meridian, with the sign of polarity closer to the limb dominating. The sequence of short-term imbalances are not closely linked to CMEs and flares and no permanent imbalance remains after them. We propose that both kinds of imbalance are due to the presence of a horizontal field component (parallel to the photospheric surface) in the emerging flux. Title: The Long-Term Evolution of AR 7978: The Scalings of the Coronal Plasma Parameters with the Mean Photospheric Magnetic Field Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Mandrini, C. H.; Harra, L.; Klimchuk, J. A. Bibcode: 2003ApJ...586..579V Altcode: We analyze the evolution of the fluxes observed in X-rays and correlate them with the magnetic flux density in active region (AR) NOAA 7978 from its birth throughout its decay, for five solar rotations. We use Solar and Heliospheric Observatory Michelson Doppler Imager (MDI) data, together with Yohkoh Soft X-Ray Telescope (SXT) and Yohkoh Bragg Crystal Spectrometer (BCS) data, to determine the global evolution of the temperature and the emission measure of the coronal plasma at times when no significant brightenings were observed. We show that the mean X-ray flux and derived parameters, temperature and emission measure (together with other quantities deduced from them, such as the density and the pressure), of the plasma in the AR follow power-law relationships with the mean magnetic flux density (B). The exponents (b) of these power-law functions (aBb) are derived using two different statistical methods, a classical least-squares method in log-log plots and a nonparametric method, which takes into account the fact that errors in the data may not be normally distributed. Both methods give similar exponents, within error bars, for the mean temperature and for both instruments (SXT and BCS); in particular, b stays in the range [0.27, 0.31] and [0.24, 0.57] for full-resolution SXT images and BCS data, respectively. For the emission measure, the exponent b lies in the range [0.85, 1.35] and [0.45, 1.96] for SXT and BCS, respectively. The determination of such power-law relations, when combined with the results from coronal heating models, can provide us with powerful tools for determining the mechanism responsible for the existence of the high-temperature corona. Title: The Long-Term Evolution of AR 7978: Testing Coronal Heating Models Authors: Démoulin, P.; van Driel-Gesztelyi, L.; Mandrini, C. H.; Klimchuk, J. A.; Harra, L. Bibcode: 2003ApJ...586..592D Altcode: We derive the dependence of the mean coronal heating rate on the magnetic flux density. Our results are based on a previous study of the plasma parameters and the magnetic flux density (B) in the active region NOAA 7978 from its birth to its decay, throughout five solar rotations using the Solar and Heliospheric Observatory Michelson Doppler Imager, Yohkoh Soft X-Ray Telescope (SXT), and Yohkoh Bragg Crystal Spectrometer (BCS). We use the scaling laws of coronal loops in thermal equilibrium to derive four observational estimates of the scaling of the coronal heating with B (two from SXT and two from BCS observations). These results are used to test the validity of coronal heating models. We find that models based on the dissipation of stressed, current-carrying magnetic fields are in better agreement with the observations than models that attribute coronal heating to the dissipation of MHD waves injected at the base of the corona. This confirms, with smaller error bars, previous results obtained for individual coronal loops, as well as for the global coronal emission of the Sun and cool stars. Taking into account that the photospheric field is concentrated in thin magnetic flux tubes, both SXT and BCS data are in best agreement with models invoking a stochastic buildup of energy, current layers, and MHD turbulence. Title: How to test coronal heating models? Authors: Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.; Klimchuk, J. A.; Harra, L. K. Bibcode: 2003BAAA...46....5M Altcode: We have tested coronal heating models following two different approaches. In the first case, we compared the dependence of the coronal heating rate predicted by theoretical models with the observed one, deriving the scalings of parameters, such as: the density, temperature and intensity of the coronal magnetic field, with the length of magnetic field lines. To do so, we combined density and temperature measurements for 47 coronal loops with magnetic field models for 14 active regions. In the second case, we analyzed the long term evolution of an active region observed during seven rotations on the solar disk and we determined the dependence of the observed heating rate with the magnetic field density (bar{B}), after finding the scalings of plasma parameters with bar{B}. In both cases, we found that models based on the dissipation of stressed, current-carrying magnetic fields (called direct current models) are in better agreement with observations than models that attribute coronal heating to the dissipation of MHD waves injected at the base of the corona (called alternate current models). Taking into account that the photospheric field is concentrated in thin magnetic flux tubes, observations are in best agreement with models invoking a stochastic buildup of energy, current layers and MHD turbulence, within direct current models. Title: Active region helicity evolution and related coronal mass ejection activity Authors: Green, L. M.; López Fuentes, M. C.; Mandrini, C. H.; van Driel-Gesztelyi, L.; Démoulin, P. Bibcode: 2003AdSpR..32.1959G Altcode: The computation of magnetic helicity has become increasingly important in the studies of solar activity. Observations of helical structures in the solar atmosphere, and their subsequent ejection into the interplanetary medium, have resulted in considerable interest to find the link between the amount of helicity in the coronal magnetic field and the origin of coronal mass ejections (CMEs), which provide a natural method to remove helicity from the corona. Recent works have endeavored to find the source of helicity to explain the observed CME activity in specific cases. The main candidates being differential rotation, shear motions or a transfer of helicity from below the photosphere into the corona. We study an active region for several rotations during 1997 and 1998 to investigate the relative importance of these mechanisms. We find that photospheric differential rotation cannot provide the required magnetic helicity to the corona and the ejected CMEs. Localized photospheric motions can provide a larger helicity flux, though still not sufficient. Title: Magnetic twist and writhe of active regions. On the origin of deformed flux tubes Authors: López Fuentes, M. C.; Démoulin, P.; Mandrini, C. H.; Pevtsov, A. A.; van Driel-Gesztelyi, L. Bibcode: 2003A&A...397..305L Altcode: 2014arXiv1411.5626L We study the long term evolution of a set of 22 bipolar active regions (ARs) in which the main photospheric polarities are seen to rotate one around the other during several solar rotations. We first show that differential rotation is not at the origin of this large change in the tilt angle. A possible origin of this distortion is the nonlinear development of a kink-instability at the base of the convective zone; this would imply the formation of a non-planar flux tube which, while emerging across the photosphere, would show a rotation of its photospheric polarities as observed. A characteristic of the flux tubes deformed by this mechanism is that their magnetic twist and writhe should have the same sign. From the observed evolution of the tilt of the bipoles, we derive the sign of the writhe of the flux tube forming each AR; while we compute the sign of the twist from transverse field measurements. Comparing the handedness of the magnetic twist and writhe, we find that the presence of kink-unstable flux tubes is coherent with no more than 35% of the 20 cases for which the sign of the twist can be unambiguously determined. Since at most only a fraction of the tilt evolution can be explained by this process, we discuss the role that other mechanisms may play in the inferred deformation. We find that 36% of the 22 cases may result from the action of the Coriolis force as the flux tube travels through the convection zone. Furthermore, because several bipoles overpass in their rotation the mean toroidal (East-West) direction or rotate away from it, we propose that a possible explanation for the deformation of all these flux tubes may lie in the interaction with large-scale vortical motions of the plasma in the convection zone, including also photospheric or shallow sub-photospheric large scale flows. Title: Observations of magnetic helicity Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Mandrini, C. H. Bibcode: 2003AdSpR..32.1855V Altcode: The first observational signature of magnetic helicity in the solar atmosphere (sunspot whirls) was discovered 77 years ago. Since then, the existence of a cycle-invariant hemispheric helicity pattern has been firmly established through current helicity and morphological studies. During the last years, attempts were made to estimate/ measure magnetic helicity from solar and interplanetary observations. Magnetic helicity (unlike current helicity) is one of the few global quantities that is conserved even in resistive magnetohydrodynamics (MHD) on a timescale less than the global diffusion timescale, thus magnetic helicity studies make it possible to trace helicity as it emerges from the sub-photospheric layers to the corona and then is ejected via coronal mass ejections (CMEs) into the interplanetary space reaching the Earth in a magnetic cloud. We give an overview of observational studies on the relative importance of different sources of magnetic helicity, i.e. whether photospheric plasma motions (photospheric differential rotation and localized shearing motions) or the twist of the emerging flux tubes created under the photosphere (presumably by the radial shear in the differential rotation in the tachocline) is the dominant helicity source. We examine the sources of errors present in these early results and try to judge how realistic they are. Title: Why to determine the magnetic helicity in corona and interplanetary medium? Authors: Luoni, M. L.; Dasso, S.; Mandrini, C. H.; van Driel-Gesztelyi, L.; Démoulin, P. Bibcode: 2003BAAA...46....8L Altcode: Magnetic clouds are huge objects that travel in the interplanetary medium, transporting magnetic helicity (MH) produced by the Sun. Since the dissipation time of MH is much larger than the typical time associated with the dynamical processes in the solar corona and the heliosphere, MH is the natural magnetohydrodinamic (MHD) magnitude to compare interplanetary manifestations with the associated solar processes. In this work we study an active region that produced a coronal mass ejection (CME). We model the coronal magnetic field using a linear force free approach, and we calculate the magnetic flux and the variation of MH, before and after the ejection of the CME. We model also the magnetic field configuration of the associated interplanetary cloud, using several cylindrical models, and estimate the flux and the content of MH. Finally, we compare the coronal and the interplanetary values for the flux and the MH, and we find a very good agreement. The coronal flux is 1022Mx, while the magnetic flux for the cloud is around 1021Mx (∼ 10% of the coronal flux, as typically observed). The variation of the coronal MH turns out to be 3x1042Mx2, while we obtain that the MH contained in the magnetic cloud is in the range (2-8)x1042Mx2. Our results indicate that MH is a very useful tool to link phenomena in very different regimes and can be used to constrain both coronal and interplanetary models. Title: CME shock warps coronal streamer - observation and MHD simulation Authors: van der Holst, B.; van Driel-Gesztelyi, L.; Poedts, S. Bibcode: 2002ESASP.506...71V Altcode: 2002svco.conf...71V; 2002ESPM...10...71V A fast (v ≥ 1000 km s-1) CME was observed on 14 January 2002, which was linked to an M4.4 long-duration flare event and a post-eruption loop system visible on, but partially occulted by, the SW limb. The fast expanding CME collided with a North-hemispheric helmet streamer, which was located above NOAA AR 9773 and was in 60° distance from the CME source region. An interaction with the CME (I) pushed the streamer aside and (II) created a deflection, setting off an outward propagating wavelike deformation along it. At the same time, a decametric-hectometric type-II radio burst was observed with the WAVES RAD2 instrument onboard the WIND spacecraft. Type-II bursts are indicative of shock waves. At about the time of the CME-streamer interaction a splitting was seen in the type-II emission, which indicated a shock continuing to propagate away from the Sun (thus getting into lower and lower density domains) and another branch, which indicated a shock propagating into denser plasma domain. We interpret this fine-structure of the type-II bursts as a result of the CME-streamer interaction. We suggest that the shock wave, which was associated with this fast CME, penetrated into the helmet streamer and then died away in the denser plasma (the splitting lasted for about 30 minutes). With our 2-D MHD code we simulate this CME-streamer interaction, using the observed configuration and magnetic topology. The simulation results confirm our hypothesis. Title: Global budget for an eruptive active region . I. Equilibrium reconstruction approach Authors: Bleybel, A.; Amari, T.; van Driel-Gesztelyi, L.; Leka, K. D. Bibcode: 2002A&A...395..685B Altcode: We present results on the magnetic structure of NOAA Active Region #7912 which was involved in a long duration flare on 14 October 1995, and was the source region for a magnetic cloud observed by the WIND spacecraft from October 18-20. Using vector magnetograms from the Imaging Vector Magnetograph (``IVM''), we reconstruct the magnetic field above this active region, assuming it is in a non-linear force-free state. This reconstruction is used to determine global properties of the active region magnetic field including topology, magnetic energy, and relative magnetic helicity. A comparison of some global quantities before and after the eruptive event is discussed. We show that the magnetic energy and relative helicity of the active region decreased after the eruption, consistent with the ejection of a large amount of helicity (in the magnetic cloud). We also show that the relaxed post-flare state still contains nonlinearities and is not consistent with a linear force-free state as predicted by Taylor's theory of relaxation. These results agree with those of recent numerical simulations concerning plasmoid ejection and helicity redistribution in the disruption of magnetic configurations. We propose as an explanation that the anchoring of field lines in the photosphere prevents a full cascade to the Taylor state, and that a variational formulation in which the action functional would describe this constraint should be derived. Title: On the origin of peculiar active regions Authors: Mandrini, C. H.; López Fuentes, M. C.; Démoulin, P.; van Driel-Gesztelyi, L.; Pevtsov, A. A. Bibcode: 2002ESASP.505..121M Altcode: 2002solm.conf..121M; 2002IAUCo.188..121M We study the long term evolution of a set of bipolar active regions (ARs) in which the main photospheric polarities are seen to rotate one around the other during several solar rotations. After showing that differential rotation cannot produce this large change in the tilt angle, we interpret this peculiar evolution as being the result of the emergence of magnetic flux tubes that are distorted with respect to the classical Ω-loop shape. A possible origin of this distortion is the nonlinear development of a kink-instability. Flux tubes deformed by this mechanism must have the same sign of twist and writhe. From the observed evolution of the tilt of the bipoles, we derive the sign of the writhe of the tube forming each AR; while we compute the sign of the twist from transverse field measurements. Comparing the handedness of the magnetic twist and writhe, we find that the presence of kink-unstable flux tubes is coherent with no more than 32% of the studied cases; so, a small fraction of these peculiar ARs can be explained by this process. Then we discuss the role that other mechanisms may play inducing the inferred deformation, such as the Coriolis force or external rotational motions of the plasma as the tube ascends in the convection zone. Title: Dedication (SOLMAG 2002): Karen L. Harvey 1942 - 2002 Authors: Schrijver, Karel; van Driel-Gesztelyi, Lidia Bibcode: 2002ESASP.505D..15S Altcode: 2002IAUCo.188D..15S; 2002solm.confD..15S No abstract at ADS Title: Emergence and loss of magnetic flux on the solar surface Authors: van Driel-Gesztelyi, Lidia Bibcode: 2002ESASP.505..113V Altcode: 2002solm.conf..113V; 2002IAUCo.188..113V This review is focused on observations and theoretical advances on large-scale flux emergence and decay, which forms and dominates the magnetic field patterns on the Sun. The basic characteristics of emerging flux (asymmetry, inclination to the vertical, twist, sea-serpent-like appearance in the early stage of flux emergence in the photosphere) are described together with the results of relevant MHD simulations, which help us to interpret these observations. Magnetic flux emergence is far from being a random process in the active belt: it has a grouping (nesting) tendency, which has important implications for the operation of the solar dynamo. As soon as active regions are fully formed, they start decaying. Their magnetic flux gradually speads over an ever-increasing area and gets removed from the photosphere via small scale processes (e.g. Ohmic dissipation and flux cancellation, including flux submergence). Emergence of U-loops may play an important role in the removal of large-scale flux from the photopshere. Title: The Magnetic Helicity Budget of a cme-Prolific Active Region Authors: Green, L. M.; López fuentes, M. C.; Mandrini, C. H.; Démoulin, P.; Van Driel-Gesztelyi, L.; Culhane, J. L. Bibcode: 2002SoPh..208...43G Altcode: Coronal mass ejections (CMEs) are thought to be the way by which the solar corona expels accumulated magnetic helicity which is injected into the corona via several methods. DeVore (2000) suggests that a significant quantity is injected by the action of differential rotation, however Démoulin et al. (2002b), based on the study of a simple bipolar active region, show that this may not be the case. This paper studies the magnetic helicity evolution in an active region (NOAA 8100) in which the main photospheric polarities rotate around each other during five Carrington rotations. As a result of this changing orientation of the bipole, the helicity injection by differential rotation is not a monotonic function of time. Instead, it experiences a maximum and even a change of sign. In this particular active region, both differential rotation and localized shearing motions are actually depleting the coronal helicity instead of building it. During this period of five solar rotations, a high number of CMEs (35 observed, 65 estimated) erupted from the active region and the helicity carried away has been calculated, assuming that each can be modeled by a twisted flux rope. It is found that the helicity injected by differential rotation (≈−7×1042 Mx2) into the active region cannot provide the amount of helicity ejected via CMEs, which is a factor 5 to 46 larger and of the opposite sign. Instead, it is proposed that the ejected helicity is provided by the twist in the sub-photospheric part of the magnetic flux tube forming the active region. Title: The Magnetic Helicity Injected by Shearing Motions Authors: Démoulin, P.; Mandrini, C. H.; Van Driel-Gesztelyi, L.; Lopez Fuentes, M. C.; Aulanier, G. Bibcode: 2002SoPh..207...87D Altcode: Photospheric shearing motions are one of the possible ways to inject magnetic helicity into the corona. We explore their efficiency as a function of their particular properties and those of the magnetic field configuration. Based on the work of M. A. Berger, we separate the helicity injection into two terms: twist and writhe. For shearing motions concentrated between the centers of two magnetic polarities the helicity injected by twist and writhe add up, while for spatially more extended shearing motions, such as differential rotation, twist and writhe helicity have opposite signs and partially cancel. This implies that the amount of injected helicity can change in sign with time even if the shear velocity is time independent. We confirm the amount of helicity injected by differential rotation in a bipole in the two particular cases studied by DeVore (2000), and further explore the parameter space on which this injection depends. For a given latitude, tilt and magnetic flux, the generation of helicity is slightly more efficient in young active regions than in decayed ones (up to a factor 2). The helicity injection is mostly affected by the tilt of the AR with respect to the solar equator. The total helicity injected by shearing motions, with both spatial and temporal coherence, is at most equivalent to that of a twisted flux tube having the same magnetic flux and a number of turns of 0.3. In the solar case, where the motions have not such global coherence, the injection of helicity is expected to be much smaller, while for differential rotation this maximum value reduces to 0.2 turns. We conclude that shearing motions are a relatively inefficient way to bring magnetic helicity into the corona (compared to the helicity carried by a significantly twisted flux tube). Title: Long-term helicity evolution in NOAA active region 8100 Authors: Green, L. M.; López Fuentes, M. C.; Mandrini, C. H.; van Driel-Gesztelyi, L.; Démoulin, P. Bibcode: 2002ESASP.477...43G Altcode: 2002scsw.conf...43G Magnetic helicity is the topological parameter used to describe the structure in the magnetic field and has become increasingly important in coronal studies. Helicity is well preserved in the corona even under non-ideal MHD conditions (see Biskamp 1993), and the Sun can avoid endless accumulation of helicity by ejecting it via the launch of coronal mass ejections (eg. Rust 1994; Low 1996; Devore 2000). Computations are made for NOAA active region 8100 to determine the coronal helicity and helicity injected into the region by differential rotation. These values are then compared to the total amount of helicity lost via coronal mass ejections to test whether differential rotation can inject a significant amount of helicity into the corona. It is found that differential rotation cannot inject a significant amount of helicity to be a viable source for the coronal mass ejection activity. Instead, helicity is likely to be brought into the corona by the emergence of twisted and distorted flux tubes. Title: Numerical modeling of CME initiation and propagation Authors: Poedts, S.; van der Holst, B.; de Sterck, H.; van Driel-Gesztelyi, L.; Csík, A.; Milesi, A.; Deconinck, H. Bibcode: 2002ESASP.477..263P Altcode: 2002scsw.conf..263P The shocks in the solar corona caused by fast Coronal Mass Ejections (CMEs) and the shock at the Earth's magnetosphere caused by the corresponding magnetic clouds (superposed on the solar wind) are studied in the framework of computational magnetohydrodynamics (MHD). Due to the presence of three characteristic velocities and the anisotropy induced by the magnetic field, MHD shocks can have a complicated structure including secondary shock fronts, overcompressive and compound shocks, etc. Numerical simulations show that CME shocks (in the lower corona) and the shock at the Earth's magnetosphere (at times of the impact of a magnetic cloud) have such a complex structure. The CME shocks are important for 'space weather' because they can easily be observed in radio wavelengths. This makes it possible to track the position of the CMEs/magnetic clouds and, hence, to follow their propagation through the corona. The collision of two such shocks is discussed. Also, the possibility of locating the magnetic cloud from the passage of a satellite through the leading shock front is discussed. Moreover, the topology of the shock at the Earth's magnetosphere at the impact of a magnetic cloud is important for the 'geo-effectiveness' of the magnetic storms. Hence, a detailed study of the MHD shocks generated by CMEs may reveal some of the key properties space weather. Title: The distribution of peculiar active regions along two solar cycles Authors: Mandrini, C. H.; López Fuentes, M. C.; Démoulin, P.; van Driel-Gesztelyi, L. Bibcode: 2002ESASP.477...27M Altcode: 2002scsw.conf...27M We perform a statistical study of the spatial and temporal distribution of "peculiar" active regions (ARs) along solar cycles 21 and 22. ARs usually appear in the photosphere in the form of bipolar concentrations of magnetic flux, by "peculiar" we mean regions in which the the main polarities rotate one around the other along several solar rotations. Our results show that these regions are spatially distributed as usual ARs when no selection on their magnetic flux is applied. When classified according to their flux, the latitudinal distribution of ARs above 1022 Mx closely follow the butterfly diagram; while those with lower flux are more randomly distributed. The number of rotating ARs follow the activity cycle, with a tendency to dual-peak maxima. Title: Magnetic build-up and precursors of CMEs Authors: van Driel-Gesztelyi, Lidia; Schmieder, Brigitte; Poedts, Stefaan Bibcode: 2002ESASP.477...47V Altcode: 2002scsw.conf...47V CMEs are fundamentally magnetic phenomena, thus to improve CME forecast we have to find out more about the characteristics of the small and large-scale magnetic field in and around their source region prior to CME occurrence. In this paper we show examples of the magnetic evolution of CME-prolific active regions using SOHO/MDI data. It appears that CMEs are preceded by magnetic evolution during which the helicity of the source region is increasing due to twisted flux emergence, shearing motions between opposite polarity footpoints of subsequently emerging bipoles and, in a smaller extend, by the differential rotation acting on the emerged flux. Furthermore, we find short-term magnetic precursors of CME events, typically a combination of major flux emergence, cancellation and fast shearing motions in active regions with strong concentrated magnetic fields prior to flare-related CMEs and small-scale cancellation events along the magnetic inversion line in decayed active regions with low magnetic flux density prior to filament eruption-related CMEs. We make an overview of recent studies on magnetic helicity and suggest that such analyses will be able to provide a key to unlock the secrets of CME buildup and initiation. Title: Multi-wavelength observations of an X-class flare without a coronal mass ejection. Authors: Green, L. M.; Matthews, S. A.; van Driel-Gesztelyi, L.; Harra, L. K.; Culhane, J. L. Bibcode: 2002SoPh..205..325G Altcode: Developments in our knowledge of coronal mass ejections (CMEs) have shown that many of these transients occur in association with solar flares. On the occasions when there is a common occurrence of the eruption and the flare, it is most likely that the flare is of high intensity and/or long-duration (Burkepile, Hundhausen, and Webb, 1994; Munro et al., 1979; Webb and Hundhausen, 1987). A model for the relationship between the long-duration event and eruption has been developed (Carmichael, 1964; Sturrock, 1966; Hirayama, 1974; Kopp and Pneuman, 1976), but not so for the high-intensity flares and eruptions. This work investigates the magnetic topology changes that occur for a X1.2 GOES classification flare which has no associated CME. It is found that the flare is likely to result from the interaction between two pre-existing loops low in the corona, producing a confined flare. Slightly higher in the corona, a loop is observed which exhibits an outward motion as a result of the reconfiguration during reconnection. The objective of this work is to gain insight on the magnetic topology of the event which is critical in order to determine whether a high-intensity flare is likely to be related to a CME or not. Title: What is the source of the magnetic helicity shed by CMEs? The long-term helicity budget of AR 7978 Authors: Démoulin, P.; Mandrini, C. H.; van Driel-Gesztelyi, L.; Thompson, B. J.; Plunkett, S.; Kovári, Zs.; Aulanier, G.; Young, A. Bibcode: 2002A&A...382..650D Altcode: An isolated active region (AR) was observed on the Sun during seven rotations, starting from its birth in July 1996 to its full dispersion in December 1996. We analyse the long-term budget of the AR relative magnetic helicity. Firstly, we calculate the helicity injected by differential rotation at the photospheric level using MDI/SoHO magnetograms. Secondly, we compute the coronal magnetic field and its helicity selecting the model which best fits the soft X-ray loops observed with SXT/Yohkoh. Finally, we identify all the coronal mass ejections (CMEs) that originated from the AR during its lifetime using LASCO and EIT/SoHO. Assuming a one to one correspondence between CMEs and magnetic clouds, we estimate the magnetic helicity which could be shed via CMEs. We find that differential rotation can neither provide the required magnetic helicity to the coronal field (at least a factor 2.5 to 4 larger), nor to the field ejected to the interplanetary space (a factor 4 to 20 larger), even in the case of this AR for which the total helicity injected by differential rotation is close to the maximum possible value. However, the total helicity ejected is equivalent to that of a twisted flux tube having the same magnetic flux as the studied AR and a number of turns in the interval [0.5,2.0]. We suggest that the main source of helicity is the inherent twist of the magnetic flux tube forming the active region. This magnetic helicity is transferred to the corona either by the continuous emergence of the flux tube for several solar rotations (i.e. on a time scale much longer than the classical emergence phase), or by torsional Alfvén waves. Title: Relation between the coronal magnetic helicity to the helicity in interplanetary magnetic clouds Authors: Luoni, M. L.; Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.; López Fuentes, M. C. Bibcode: 2002BAAA...45...20L Altcode: On October 18, 1995, the Solar Wind Experiment and the Magnetic Field Instrument on board the WIND spacecraft registered a magnetic cloud at 1 AU, which was followed by a strong geomagnetic storm. The solar source of this phenomenon was located in active region (AR) NOAA 7912. On October 14, 1995, a C1.6 long duration event (LDE) started at approximately 5:00 UT and lasted for around 15 hours. In this work, we compute the variation of the coronal magnetic helicity using a linear force-free model of the field. We use magnetograms obtained at Kitt Peak National Solar Observatory as boundary conditions to extrapolate the photospheric magnetic field to the corona. The magnetic helicity is calculated at three different times, changing the parameters of the magnetic field model to fit the loops observed in soft X-rays by the Soft X-ray Telescope on board of Yohkoh (SXT/Yohkoh). The computations are done before the LDE, during its maximun and its decay phase. The variation of the coronal magnetic helicity is compared to the helicity of the interplanetary magnetic cloud observed by WIND. These values turn out to be quite similar, considering the errors involved. Our results confirm quantitatively the link between solar and interplanetary phenomena. Title: Active region helicity evolution and related coronal mass ejection activity. Authors: Green, L.; Mandrini, C.; van Driel-Gesztelyi, L.; Demoulin, P. Bibcode: 2002cosp...34E1213G Altcode: 2002cosp.meetE1213G The computation of magnetic helicity has become increasingly important in the studies of solar activity. Observations of helical structures in the solar atmosphere, and their subsequent ejection into the interplanetary medium, have resulted in considerable interest to find the link between the amount of helicity in the coronal magnetic field and the origin of coronal mass ejections (CMEs). This is reinforced by theory which shows magnetic helicity to be a well preserved quantity (Berger, 1984), and so with a continued injection into the corona an endless accumulation will occur. CMEs therefore provide a natural method to remove helicity from the corona. Recent works (DeVore, 2000, Chae, 2001, Chae et al., 2001, Demoulin et al., 2002, Green et al., 2002) have endeavoured to find the source of helicity in the corona to explain the observed CME activity in specific cases. The main candidates being differential rotation, shear motions or a transfer of helicity from below the photosphere into the corona. In order to establish a confident relation between CMEs and helicity, these works needs to be expanded to include CME source regions with different characteristics. A study of a very different active region will be presented and the relationship between helicity content and CME activity will be discussed in the framework of the previous studies. Title: Helicity Loading and Dissipation: The Helicity Budget of AR 7978 from the Cradle to the Grave Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Mandrini, C. H.; Plunkett, S.; Thompson, B.; Kövári, Zs.; Aulanier, G.; Young, A.; López Fuentes, M.; Poedts, S. Bibcode: 2002mwoc.conf..143V Altcode: An isolated active region was observed on the Sun during seven rotations, starting in July 1996. I will present a study of its magnetic field, concentrating on its helicity budget. The photospheric field is extrapolated into the corona in a linear force-free approach, using SOHO/MDI magnetograms and Yohkoh/SXT images, allowing us to compute, in a crude way, the relative coronal magnetic helicity of the active region. Using the observed magnetic field distribution (SOHO/MDI magnetograms) we also calculate the helicity injected by the differential rotation during seven solar rotations. Finally, using SOHO/LASCO and EIT as well as Yohkoh/SXT observations, we identify all the 26 CMEs which originated from this active region during its lifetime and using average values of the field and radius of magnetic clouds, we estimate the helicity which should be shed via CMEs. We compare these three values to evaluate the importance of the differential rotation relative to twisted flux emergence as a source of magnetic helicity. We find that the differential rotation can neither provide enough helicity to account for the diagnosed coronal heicity values, nor for the helicity carried away by CMEs. We suggest that the main source of the magnetic helicity must be the inherent twist of the magnetic flux tube forming the active region. This magnetic helicity is transferred to the corona either by a slow continuous emergence of the flux tube or by torsional Alfven waves, during several solar rotations. Title: Multi-Wavelength Observations of Yohkoh White-Light Flares Authors: Matthews, S. A.; van Driel-Gesztelyi, L.; Hudson, H. S.; Nitta, N. V. Bibcode: 2002mwoc.conf..289M Altcode: The problem of accounting for the continuum emission that is observed in solar flares is still one which is largely unresolved. These white-light flares place severe constraints on the energy requirements and transport mechanisms operating in the flare, raising the question of whether partial or total in-situ heating is required to account for this deep atmospheric heating. Since it is widely believed that the energy release in solar flares occurs in the corona and that energy is then transported to the low chromosphere where the optical emission is produced, most attempts to explain the origin of white-light flares have centred on canonical mechanisms. However, it has become clear that the spatial and temporal correspondence between white-light and HXR is not one-to one. In order to further our understanding of these events we study the temporal and spatial relationships between emission in the visible, SXR and HXR regimes in all of the white-light flares observed by Yohkoh prior to the failure of the Soft X-ray Telescope (SXT) Aspect Camera in 1992; a total of approximately 30 events. Title: Observations of emerging flux tubes Authors: van Driel-Gesztelyi, Lidia Bibcode: 2002ocnd.confE...6V Altcode: No abstract at ADS Title: Inferring the Writhe of Emerging Flux Tubes from the Evolution of the Orientation of Bipole Axes Authors: López Fuentes, M. C.; Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.; Pevtsov, A. Bibcode: 2002RMxAC..14..108L Altcode: No abstract at ADS Title: Observations of helicity Authors: van Driel-Gesztelyi, L. Bibcode: 2002cosp...34E1455V Altcode: 2002cosp.meetE1455V I will review attempts made during the last decade to evaluate and measure current helicity and magnetic helicity from solar and interplanetary observations. I will show the main results of the current helicity studies, which led to important discoveries like e.g. the hemispheric helicity pattern. Then I give an overview of multiwavelength observational studies on magnetic helicity. Magnetic helicity (unlike current helicity) is one of the few global quantities, which is conserved even in resistive MHD on a timescale less than the global diffusion timescale, thus magnetic helicity studies make it possible to trace helicity as it emerges from the sub-photospheric layers to the corona and then is ejected via CMEs into the interplanetary space reaching the Earth in a magnetic cloud. I will give an overview of observational studies on the relative importance of different sources of magnetic helicity, i.e. whether photospheric plasma motions (differential rotation and localised shearing motions) generate the bulk of helicity ejected in CMEs or the twist of the emerging flux tubes created under the photosphere (presumably by differential rotation in the tachocline) is the dominant helicity source. Title: Peculiar Active Regions during the Last Two Solar Cycles Authors: López Fuentes, M. C.; Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L. Bibcode: 2002RMxAC..14R.107L Altcode: No abstract at ADS Title: Evolution of the source region of the interplanetary magnetic cloud of 18-20 Oct. 1995 Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Baranyi, T. Bibcode: 2002AdSpR..29.1489V Altcode: We follow the evolution and activity of the reversed polarity AR 7912 using multi-wavelength observations. We find that the presence of high shear increased by flux emergence led to the occurrence of a long-duration eruptive flare on 14 October 1995, which was manifested in the SXR corona by an arcade of expanding sigmoidal loops. A twisted magnetic cloud was observed at 1 AU between October 18-20. We propose that it was ejected from this reversed polarity AR, and it was associated with the expanding sigmoids. Title: Relationships between CME's and prominences Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Aulanier, G.; Démoulin, P.; Thompson, B.; De Forest, C.; Wiik, J. E.; Saint Cyr, C.; Vial, J. C. Bibcode: 2002AdSpR..29.1451S Altcode: We have studied the erupting prominences which were associated with coronal mass ejections during a series of campaigns involving both spacecraft and ground-based observatories. The evolution of the physical conditions within the prominences was established from Hα and magnetic field observations. Particular attention ahs been paid to the presence of mixed amgnetic polarity in the filament channel, the evolution of the shear of the large-scale magnetic field, and the existence of multiple magnetic inversion lines. We conclude that reconnection of large-scale coronal magnetic fields is responsible for both the CME and filament eruption. Title: Long-Term Evolution of Active Regions Authors: López Fuentes, M.; Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L. Bibcode: 2001ASPC..248..131L Altcode: 2001mfah.conf..131L No abstract at ADS Title: An Observational Test for Solar Atmospheric Heating Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Ireland, J.; Thompson, B.; Fludra, A.; Oláh, K.; Kövári, Zs.; Harra, L. K.; Mandrini, C. H.; Bocchialini, K.; Orlando, S. Bibcode: 2001IAUS..203..514V Altcode: We study the evolution of the emissivity and heating correlated with magnetic observables of an active region from its birth throughout its decay during seven solar rotations (July-Dec. 1996). Taking one "snapshot" per g:wq: Command not found. time of flares, we analyse multi-wavelength and multi-instrument data obtained from SOHO (MDI, EIT, CDS and SUMER), Yohkoh (SXT), GOES, SOLSTICE and 10.7 cm radio data from DRAO, Canada. We utilise our results to test the validity of coronal heating models. We find that models which are based on the dissipation of stressed, current-carrying magnetic fields are in better agreement with the observations than the models which attribute coronal heating to the dissipation of MHD waves. Title: The Relationship between CMEs and Prominence Eruptions Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Delannée, C.; Simnett, G. M.; Wiik, J. E. Bibcode: 2001IAUS..203..310S Altcode: From multi-wavelength studies of eruptions of prominences observed by Yohkoh, SoHO and ground-based observatories, we find a good correlation between prominence eruptions and CMEs (i.e. May 1 1996, Sept 25 1996, May 31 1997). Focusing our interest on their temporal relationship, we observe that it is not clear that filament eruption is prior to the CME. Nevertheless they are both signatures of destabilization of the global coronal magnetic field. The magnetic configuration in the corona should involve the initial presence of a twisted flux tube. The eruption could be driven by a fast increase of the poloidal field in the flux tube or by photospheric shearing motions of the flux tube. Title: Magnetic Evolution of a Long-Lived Active Region: The Sources of Magnetic Helicity Authors: Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.; Aulanier, G.; Thompson, B.; Plunkett, S.; Kövári, Zs. Bibcode: 2001ASPC..248..139M Altcode: 2001mfah.conf..139M No abstract at ADS Title: Flux Ratios of Solar and Stellar Active Regions (CD-ROM Directory: contribs/olah2) Authors: Oláh, K.; van Driel-Gesztelyi, L. Bibcode: 2001ASPC..223..709O Altcode: 2001csss...11..709O No abstract at ADS Title: Emergence of a U-loop - sub-photospheric link between solar active regions Authors: van Driel-Gesztelyi, L.; Malherbe, J. -M.; Démoulin, P. Bibcode: 2000A&A...364..845V Altcode: Using SOHO/MDI magnetic maps we present the first direct observational evidence for the emergence of a U-loop in the solar photosphere. We show that two active regions (ARs), i.e. two adjacent Omega -loops, which were emerging at the same time at the same solar latitude, about 150000 km distance in longitude from each other, emerged from at least partially the same toroidal flux strand, and we bring five independent arguments to prove this assertion. The opposite polarity legs of the two Omega -loops were connected below the photosphere by a U-shaped loop. Following the emergence of the Omega -loops, the U-loop started emerging, manifested by the fast proper motion of the leading spots of the eastern (smaller) active region, which, after forming an elongated channel, collided with the following spots of the westerly AR and started cancelling with them. The full cancellation could not be followed because the ARs rotated out of sight. The total magnetic flux of the two ARs was unequal, the flux in the smaller AR was a quarter of that of the larger one. We propose scenarios for the formation of such a U-loop and discuss the implications of the confirmed existence of U-loops for the solution of such puzzles as the in-situ disappearance of magnetic flux from active regions, active nests and the formation of inter-AR filaments. Title: Initiation of CMEs: the role of magnetic twist Authors: van Driel-Gesztelyi, L.; Manoharan, P. K.; Démoulin, P.; Aulanier, G.; Mandrini, C. H.; Lopez-Fuentes, M.; Schmieder, B.; Orlando, S.; Thompson, B.; Plunkett, S. Bibcode: 2000JASTP..62.1437V Altcode: 2000JATP...62.1437V Recent multiwavelength observations, modelling results and theoretical developments indicate the importance of twisted magnetic configurations in solar active regions (ARs) in the initiation of coronal mass ejections (CMEs). Through multiwavelength analysis of a few representative events we make an attempt to provide constraints for CME models. The two events presented here in detail start with the expansion of sigmoids (S- or inverse S-shaped loops) observed in soft X-rays. Both events (on 25 October /1994 and 14 October /1995) occurred before the launch of the SOHO spacecraft, but indirect evidences (i.e. signatures of an outward propagation traced up to /~20 solar radii and an associated magnetic cloud) suggest that both of them were related to CMEs. We show evidence that sigmoids are the coronal manifestations of twisted magnetic flux tubes, which start expanding presumably due to a loss of equilibrium. It is noteworthy that the analysed CMEs occurred in a complex (not simply bipolar) magnetic environment and in all cases we found evidences of the interaction (magnetic reconnection) with the surrounding fields. We propose a scenario for sigmoid expansion related CME events and suggest that twisted magnetic configurations are good candidates for being source regions of CMEs. Title: The Counterkink Rotation of a Non-Hale Active Region Authors: López Fuentes, M. C.; Demoulin, P.; Mandrini, C. H.; van Driel-Gesztelyi, L. Bibcode: 2000ApJ...544..540L Altcode: 2014arXiv1412.1456L We describe the long-term evolution of a bipolar non-Hale active region that was observed from 1995 October to 1996 January. During these four solar rotations the sunspots and subsequent flux concentrations, during the decay phase of the region, were observed to move in such a way that by December their orientation conformed to the Hale-Nicholson polarity law. The sigmoidal shape of the observed soft X-ray coronal loops allows us to determine the sense of the twist in the magnetic configuration. This sense is confirmed by extrapolating the observed photospheric magnetic field, using a linear force-free approach, and comparing the shape of computed field lines with the observed coronal loops. This sense of twist agrees with that of the dominant helicity in the solar hemisphere where the region lies, as well as with the evolution observed in the longitudinal magnetogram during the first rotation. At first sight the relative motions of the spots may be misinterpreted as the rising of an Ω loop deformed by a kink instability, but we deduce from the sense of their relative displacements a handedness for the flux-tube axis (writhe) that is opposite to that of the twist in the coronal loops and, therefore, to what is expected for a kink-unstable flux tube. After excluding the kink instability, we interpret our observations in terms of a magnetic flux tube deformed by external motions while rising through the convective zone. We compare our results with those of other related studies, and we discuss, in particular, whether the kink instability is relevant to explain the peculiar evolution of some active regions. Title: Magnetic Activity Associated With Radio Noise Storms Authors: Bentley, R. D.; Klein, K. -L.; van Driel-Gesztelyi, L.; Démoulin, P.; Trottet, G.; Tassetto, P.; Marty, G. Bibcode: 2000SoPh..193..227B Altcode: As it crossed the solar disk in May and June 1998, AR 8227 was tracked by TRACE, Yohkoh, SOHO, and many ground-based observatories. We have studied how the evolution of the magnetic field resulted in changes in activity in the corona. In particular, we examine how the evolving field may have led to the acceleration of electrons which emit noise storms observed by the Nançay Radio Heliograph between 30 May and 1 June 1998, in the absence of any flare. The magnetic changes were related to moving magnetic features (MMFs) in the vicinity of the leading spot and are related to the decay of this spot. Within the limits of the instrumental capabilities, the location in time and space of the radio emissions followed the changes observed in the photospheric magnetograms. We have extrapolated the photospheric magnetic field with a linear force-free approximation and find that the active region magnetic field was very close to being potential. These computations show a complex magnetic topology associated to the MMFs. The observed photospheric evolution is expected to drive magnetic reconnection in such complex magnetic topology. We therefore propose that the MMFs are at the origin of the observed metric noise-storms. Title: Large-Scale Evolution of the Active Region NOAA 7978, 7981, 7986 Observed by Goes, Soho, and Yohkoh Authors: Orlando, S.; Khan, J.; van Driel-Gesztelyi, L.; Thompson, B.; Fludra, A.; Foing, B. Bibcode: 2000AdSpR..25.1913O Altcode: We took part in a joint project aimed to study the large-scale evolution of an active region from its emergence throughout its decay for several solar rotations. Our interest focuses on the understanding of how energy is generated, released, deposited, and transformed in active regions. To this end, we determined physical parameters like intensity, temperature, and emission measure of the whole active region as a function of time for the entire period selected. We present the preliminary results of the analysis of GOES (Geosynchronous Operational Environmental Satellite), SOHO (Solar and Heliospheric Observatory) and Yohkoh data of the active region named NOAA 7978, 7981, and 7986 observed between July and October 1996 Title: Yohkoh Observations of White-Light Flares Authors: Matthews, S.; van Driel-Gesztelyi, L.; Hudson, H.; Nitta, N. Bibcode: 2000ASPC..206..239M Altcode: 2000hesp.conf..239M No abstract at ADS Title: Long-term evolution of an AR Authors: van Driel-Gesztelyi, L. Bibcode: 2000ssls.work...95V Altcode: I summarize the results of a complex and comprehensive analysis of the evolution of an isolated active region (AR) in the period of July-November 1996. Using SOHO/MDI full-disc magnetic maps, we follow the magnetic evolution of the AR for several months. We extrapolate the photospheric magnetic fields in the linear force-free approximation and match the modelled field lines with the soft X-ray loops observed with the Yohkoh/SXT in order to diagnose the coronal magnetic shear. We find that while the turbulent motions diffuse the flux, the differential rotation, and possibly twisted flux emergence, increase the magnetic shear. Flares are observed during the first three rotations, while CME events (observed by SOHO/EIT and LASCO) originate from this AR from its emergence throughout its decay. Several early CMEs, while none of the late CMEs, are related to flare events above the GOES B1 level. We find that the late CMEs occur when the magnetic shear, after accumulating for four rotations, reaches a high level and saturates. We propose that CME activity serves as a valve through which the AR could get rid of excess shear and helicity. Furthermore, we study the evolution of the emissivity and heating correlated with magnetic observables of the AR from its birth throughout its decay. Taking one "snapshot" per rotation at each consecutive central meridian passage (CMP) of the AR, outside the time of flares, we analyse multi-wavelength and multi-instrument data obtained from SOHO (MDI and SUMER), Yohkoh (SXT), GOES and 10.7 cm radio data from DRAO, Canada. We find that the magnetic flux density - emitted radiation relations follow a power-law with exponents which appear to depend on the formation temperature (height) of the emission. Title: 3-D Magnetic Configurations for Filaments and Flares: The Role of ``Magnetic Dips'' and ``Bald Patches'' Authors: Aulanier, G.; Schmieder, B.; van Driel-Gesztelyi, L.; Kucera, T.; Démoulin, P.; Fang, C.; Mein, N.; Vial, J. -C.; Mein, P.; Tang, Y. H.; Deforest, C. Bibcode: 2000AdSpR..26..485A Altcode: The 3-D magnetic configuration of a filament and of a low energy flare is reconstructed, using linear mag- netohydrostatic (lmhs) extrapolations. In both cases, we find observational signatures of energy release at the locations of computed ``bald patches'' separatrices, characterised by field lines which are tangent to the photosphere.The filament was observed on Sept. 25, 1996, in Hα with the MSDP on the German VTT, Tenerife, as well as in Si IV with SOHO/SUMER. It is modeled as a twisted flux-tube deformed by the magnetic polarities observed with SOHO/MDI. The shape and location of the computed dipped field lines are in good agreement with the shape of the filament and its feet observed in Hα. Some ``bald patches'' (BPs) are present where the distribution of dips reaches the photosphere. We show that some of the large scale field lines rooted in BPs can be related to bright fine structures in Si IV. We propose that the plasma there is heated by ohmic dissipation from the currents expected to be present along the BP separatrices.The flare was observed on May 18, 1994, in soft X-rays with Yohkoh/SXT, and in Hα at Mitaka (Japan). The magnetic field is directly extrapolated from a photospheric magnetogram from Kitt Peak Observatory. The intersections with the photosphere of the computed separatrices match well the bright Hα ribbons. The later are associated to three BPs, with overlaying dipped field lines. We show that enhanced densities are present in these dips, which can be correlated with dark Hα fibrils.Both cases show the importance of dipped field lines and BPs in the solar atmosphere. Energy release via ohmic dissipation as well as reconnection along BP separatrices is proposed to provide heating observed as UV brightenings in filament channels and even as small flares Title: Flares and Large Scale Evolution of a Solar Active Region Observed in 1996 by GOES, SOHO and YOHKOH: Implications for X-Ray stellar Variability Authors: Orlando, S.; van Driel-Gesztelyi, L.; Thomson, B.; Khan, J.; Foing, B. H. Bibcode: 2000ASIC..544..783O Altcode: 2000vsea.conf..783O No abstract at ADS Title: What Can we Learn Studying Long-Term Magnetic Evolution of Solar Active Regions? Authors: van Driel-Gesztelyi, L.; Kovari, Zs.; Lopez-Fuentes, M.; Mandrini, C. H.; Demoulin, P. Bibcode: 2000ESASP.463..451V Altcode: 2000sctc.proc..451V No abstract at ADS Title: Non Linear Force-Free Reconstruction of a Flaring Active Region Authors: Bleybel, A.; Amari, T.; van Driel-Gesztelyi, L.; Leka, K. D. Bibcode: 1999ESASP.448..709B Altcode: 1999ESPM....9..709B; 1999mfsp.conf..709B No abstract at ADS Title: The Total Eclipse Experience in Hungary Authors: van Driel-Gesztelyi, L.; Jankovics, I.; Kovács, J.; Schmieder, B.; Vincze, I. J. Bibcode: 1999ESASP.448.1297V Altcode: 1999ESPM....9.1297V; 1999mfsp.conf.1297V No abstract at ADS Title: On the Topology of Magnetic Reconnection in Flares - Constraints from Multiwavelength Observations Authors: van Driel-Gesztelyi, L. Bibcode: 1999ESASP.448..901V Altcode: 1999mfsp.conf..901V; 1999ESPM....9..901V No abstract at ADS Title: Flare loop geometry Authors: Nitta, N.; Van Driel-Gesztelyi, L.; Harra-Murnion, L. K. Bibcode: 1999SoPh..189..181N Altcode: In selected flares that occurred in AR 7260, we have studied the geometry of the brightest soft X-ray loop by tracing it on an image. Even under the assumption that the loop is contained in a plane, it is clear that a single image does not permit us to determine the full geometry. It only provides possible loop shapes as a function of the inclination angle of the loop plane with respect to the vertical. However, all the loops that reproduce the observed appearance give the same direction of increasing height as projected on to the image plane. This direction is compared with two relevant observations. Based on 2-D reconnection models that involve a cusp configuration, it is expected that the soft X-ray loop top source moves upward with time and that a higher temperature region exists above the loop top. Several flares are found to contradict these predictions, presumably implying the inadequacy of the models. Lastly we discuss a possibility of constraining the inclination angle (and hence the loop shape) with spatially-unresolved soft X-ray line spectra which are Doppler-shifted due to plasma upflows. Title: Working Group 1: Magnetic Field Structuring Authors: van Driel-Gesztelyi, L.; Martinez Pillet, V. Bibcode: 1999ESASP.446...71V Altcode: 1999soho....8...71V No abstract at ADS Title: Long-Term Evolution Of Emissivity And Heating In A Solar Active Region Authors: van Driel-Gesztelyi, L.; Thompson, B.; Démoulin, P.; Orlando, S.; Bocchialini, K.; Oláh, K.; Kövári, Z.; Deforest, C.; Khan, J.; Fludra, A.; Mandrini, C. Bibcode: 1999ESASP.446..663V Altcode: 1999soho....8..663V We study the evolution of the heating and emissivity of an active region from its birth throughout its decay during six solar rotations (July-Nov. 1996). We analyse multi-wavelength and multi-instrument data obtained from SOHO (EIT, SUMER, CDS, MDI), Yohkoh (SXT), GOES and 10.7cm radio data from DRAO, Canada. We take one "snapshot" per rotation at the time of the central meridian passage (CMP) of the AR, outside of time of flares, which appears to be representative enough to allow us to make some general conclusions about the long-term evolution. Deriving physical parameters like intensity (flux), temperature and emission measure of the entire AR vs. time, we formulate mathematically the change in radiation emitted by the decaying AR at several wavelengths. Combining the emissivity data with the evolution of magnetic flux density as the flux is being dispersed by small- and larger-scale convective motions, we make an attempt to understand the physics behind the emission and heating. We also analyse the effects of flaring on the heating of the AR, and study whether and how the flare properties evolve during the life of the active region. Title: Analysis of evolution of NOAA 7912 active region on 19 October 1995 Authors: Rudawy, P.; van Driel-Gesztelyi, L.; Cader-Sroka, B.; Mein, P.; Mein, N.; Schmieder, B.; Malherbe, J. -M.; Rompolt, B. Bibcode: 1999A&AS..139...89R Altcode: An analysis of a minor (B3.2) flare related to an X-ray jet in the reversed polarity NOAA 7912 active region is presented, focusing on various kinds of activity observed in the Hα line with the MSDP instrument. Using complementary Yohkoh soft X-ray observations and a Kitt Peak magnetic field map we study the influence of a rather low and graduate energy release on filaments, fibrils and chromospheric brightenings and their relevant coronal features. We find that this small flare affected the entire AR and was associated with strong up- and downflows along remote fibrils and filaments, which appear to be connected by large-scale loops. It is shown that at least one of the observed brightenings was caused by downflow of the matter, thus, by the kinematic heating of the material. The filament in the vicinity of the flare footpoints changed the most: it broke into two parts, temporarily rose to higher altitudes inside the AR and even erupted outside of the AR, re-forming only three hours later. We show that even a minor flare can lead to important morphological and dynamical changes in an active region. Title: The Role of "Magnetic Dips" and "Bald Patches" for a Filament Observed by SOHO and GBO Authors: Aulanier, G.; Schmieder, B.; Kucera, T.; van Driel-Gesztelyi, L.; Démoulin, P.; Mein, N.; Vial, J. -C.; Mein, P. Bibcode: 1999ASPC..184..291A Altcode: The studied filament was observed on Sept. 25, 1996, in Hα with the MSDP on the German VTT, Tenerife, as well as in Si IV with SOHO/SUMER. The 3-D magnetic configuration of the filament channel is reconstructed, using linear magnetohydrostatic (lmhs) extrapolations from a SOHO/MDI magnetogram, which is modified by a background magnetic component constraining a twisted flux-tube. This flux-tube is deformed by the magnetic polarities observed with SOHO/MDI. The shape and location of the computed "dipped field lines" are in good agreement with the shape of the filament and its feet observed in Hα. Some "bald patches" (BPs) are present where the distribution of dips reaches the photosphere. We find observational signatures in Si IV brightenings of energy release at the locations of computed "bald patch separatrices", defined by field lines which are tangent to the photosphere. We propose that the plasma is there heated by ohmic dissipation from the expected currents in the BP separatrices. The results show the importance of "dipped field lines" and "bald patches" in filament channels. Title: Making sense of sunspot decay - II. Deviations from the Mean Law and Plage Effects Authors: Petrovay, K.; Martínez Pillet, V.; van Driel-Gesztelyi, L. Bibcode: 1999SoPh..188..315P Altcode: 1999astro.ph..6258P In a statistical analysis of Debrecen Photoheliographic Results sunspot area data we find that the logarithmic deviation (log D)' of the area decay rate D from the parabolic mean decay law (derived in the first paper in this series) follows a Gaussian probability distribution. As a consequence, the actual decay rate D and the time-averaged decay rate are also characterized by approximately lognormal distributions, as found in an earlier work. The correlation time of (log D)' is about 3 days. We find a significant physical anticorrelation between (log D)' and the amount of plage magnetic flux of the same polarity in an annulus around the spot on Kitt Peak magnetograms. The anticorrelation is interpreted in terms of a generalization of the turbulent erosion model of sunspot decay to the case when the flux tube is embedded in a preexisting homogeneous `plage' field. The decay rate is found to depend inversely on the value of this plage field, the relation being very close to logarithmic, i.e., the plage field acts as multiplicative noise in the decay process. A Gaussian probability distribution of the field strength in the surrounding plage will then naturally lead to a lognormal distribution of the decay rates, as observed. It is thus suggested that, beside other multiplicative noise sources, the environmental effect of surrounding plage fields is a major factor in the origin of lognormally distributed large random deviations from the mean law in the sunspot decay rates. Title: Long-Term Magnetic Evolution of an AR and its CME Activity Authors: van Driel-Gesztelyi, L.; Mandrini, C. H.; Thompson, B.; Plunkett, S.; Aulanier, G.; Démoulin, P.; Schmieder, B.; de Forest, C. Bibcode: 1999ASPC..184..302V Altcode: Using SOHO/MDI full-disc magnetic maps, we follow the magnetic evolution of a solar active region for several months in the period of July-November 1996. We extrapolate the photospheric magnetic fields in the linear force-free approximation and match the modelled field lines with the soft X-ray loops observed with the Yohkoh/SXT in order to diagnose the coronal magnetic shear. We find that while the turbulent motions diffuse the flux, the differential rotation, and possibly twisted flux emergence, increase the magnetic shear. Flares are observed during the first three rotations, while CME events (observed by SOHO/EIT and LASCO) originate from this AR from its emergence throughout its decay. Several early CMEs, while none of the late CMEs, are related to flare events above the GOES B1 level. We find that the late CMEs occur when the magnetic shear, after accumulating for four rotations, reaches a high level and saturates. We propose that CME activity serves as a valve through which the AR could get rid of excess shear and helicity. Title: Modelling the Sun as an active star. I. A diagnosis of photometric starspot models Authors: Oláh, K.; van Driel-Gesztelyi, L.; Kővári, Zs.; Bartus, J. Bibcode: 1999A&A...344..163O Altcode: We provide a diagnosis of photometric starspot models through modelling active areas on the Sun using softwares originally written for starspot modelling. The data we used were one-dimensional measurements of the Sun in radio (10.7 cm, DRAO, Canada) and in soft X-rays (GOES satellites). In these wavelengths the response to magnetic activity results in similar amplitude variability on the Sun to those we attribute to starspots in visual wavelengths. The modelling results were compared with contemporaneous direct images (obtained at Nobeyama, Japan and with the Yohkoh and SOHO spacecraft). We found that: a) knowing well the basic physical parameters of a star, the resulting total spotted area is a fairly good approximation of the reality, thus making sense of photometric starspot modelling; b) long-term variability coupled with the rotational modulation may result in artificially high latitude spots; c) in two- or multi-spot models a resulting small spot can account for short living spots; d) systematic change in spot size could be partially due to flux ratio changes. The contrast between the studied bright active region and the undisturbed area on the Sun decreased in time following roughly a power law. At the same time, the emission measure of the active region's core similarly decreased. Title: 3-D magnetic configurations supporting prominences. III. Evolution of fine structures observed in a filament channel Authors: Aulanier, G.; Démoulin, P.; Mein, N.; van Driel-Gesztelyi, L.; Mein, P.; Schmieder, B. Bibcode: 1999A&A...342..867A Altcode: On September 25() th 1996, a quiescent filament located near the center disc (S2, E5) was observed on the German VTT (Tenerife) with the MSDP instrument, in the Hα line center and wings. SOHO/MDI line-of-sight magnetograms were co-aligned with the MSDP images, showing the position and evolution of the lateral feet of the filament in the vicinity of the parasitic magnetic polarities observed in the filament channel. Using the assumptions developed in the previous papers of this series related to the reconstruction of the 3-D magnetic configuration of filaments, we perform ``linear magnetohydrostatic'' extrapolations (taking into account the effects of plasma pressure and gravity) on the SOHO/MDI magnetograms. The main hypothesis is the presence of a twisted flux-tube located above the photospheric inversion line. Assuming that the parameters of the model do not need to be significantly modified during the evolution of the configuration for a duration of 1 day, we have shown that the 3-D distribution of dipped field lines is well correlated with Hα dark absorbing features in the filament channel: the filament itself, its lateral feet and some of the surrounding dark fibrils. In this way we confirm what was suggested in our earlier papers, i.e. that the feet are composed of the dipped portions of some field lines, which form a continuous pattern from the corona to the photosphere. We propose the same explanation for the magnetic configuration of some of the dark Hα fibrils in the channel. We show that the plasma effects are not responsible for the existence of most of the magnetic dips, however their inclusion helps to get a better correspondence between the model and the observations. We find that the average Hα Doppler velocities associated with the filament and with the chromospheric fibrils is of the order of a few hundred m s(-1) (though it can go locally up to 3 km s(-1) in the filament). These upward velocities are consistent with a quasi-static evolution of the magnetic configuration and with the support of dense plasma in magnetic dips. Title: What can we learn from Modelling the Sun as a Star? Authors: Oláh, K.; van Driel-Gesztelyi, L.; Kővári, Zs.; Bartus, J. Bibcode: 1999ASPC..158..170O Altcode: 1999ssa..conf..170O No abstract at ADS Title: The NOAA AR 6718 magnetic field extrapolation with localized current filaments. Authors: Karlický, M.; Démoulin, P.; Aulanier, G.; van Driel-Gesztelyi, L.; Hénoux, J. C.; Jirička, K. Bibcode: 1999joso.proc...97K Altcode: The 3-D extrapolation of magnetic field lines of the July 11, 1991 Kitt Peak magnetogram shows a differential magnetic field shear in the NOAA 6718 active region. A new combined extrapolation technique, which includes localized current filaments is suggested and applied in modelling of this shear. First, the potential field extrapolation is made and then force-free current paths for several current filaments in specific positions are computed. It is shown that with the electric current increase the localized magnetic field shear is increasing. The total electric current in 16 current filaments is considered up to 1.2×1012A. Title: On the role of beam driven return current instabilities in white-light flares Authors: Matthews, S. A.; Brown, J. C.; van Driel-Gesztelyi, L. Bibcode: 1998A&A...340..277M Altcode: It has been shown previously that the low ionization levels in the deep chromosphere of solar flares can cause the return current driven by a thick target electron beam to be unstable to ion aoustic wave generation, contrary to conventional wisdom. We investigate, using Yohkoh data, the possibility that anomalous heating as a result of this instability is capable of producing sufficient heating, in the right places at the right times, to account for the enhanced continuum emission actually observed in white-light flares. The Soft X-ray Telescope (SXT) onboard \it Yohkoh incorporates an aspect camera which, prior to its failure in 1992, provided white-light images at 431 nm with a bandpass of 3 nm. A number of white-light flares were observed during its operational lifetime for which there was coincident hard X-ray data from the Hard X-ray Telescope (HXT), providing suitable candidates for study. Four such events are discussed, and the model found to be viable. Title: Multi-wavelength observations of POST flare loops in two long duration solar flares Authors: Harra-Murnion, L. K.; Schmieder, B.; van Driel-Gesztelyi, L.; Sato, J.; Plunkett, S. P.; Rudawy, P.; Rompolt, B.; Akioka, M.; Sakao, T.; Ichimoto, K. Bibcode: 1998A&A...337..911H Altcode: We have analysed two Long Duration solar Events (LDEs) which produced large systems of Post Flare Loops (PFLs) and which have been observed by Yohkoh and ground-based observatories. Using the Maximum Entropy Method (MEM) image synthesis technique with new modulation patterns we were able to make hard X-ray (HXR) images of the post flare loops recorded in the L Channel (13.9-22.7 keV) of the Yohkoh Hard X-ray Telescope. We obtained co-aligned 2-D maps in Hα (10(4) K), in soft X-rays (5x 10(6) K) and in hard X-rays (20x 10(6) K). We conclude that the soft X-ray (SXR) loops lie higher than the Hα loops and the former are overlaid by HXR emission. This is suggestive of the magnetic reconnection process. However some details are not consistent with the standard models. Firstly the separation between the HXR source and the SXR loop increases with time, with the HXR source being approximately a factor of five larger than the equivalent source in impulsive flares. Secondly the cooling times deduced from observations are longer than the theoretically expected ones and the discrepancy increases with time. We review the current models in view of these results. Title: 3-D magnetic configurations supporting prominences. II. The lateral feet as a perturbation of a twisted flux-tube Authors: Aulanier, G.; Demoulin, P.; van Driel-Gesztelyi, L.; Mein, P.; Deforest, C. Bibcode: 1998A&A...335..309A Altcode: In a previous paper we have shown that a twisted flux-tube is the most probable magnetic configuration supporting prominences. The model interprets many observations in a natural way (in particular the magnetic measurements in prominences and the chirality properties). Moreover, prominence feet appear as a direct consequence of the parasitic polarities present in the filament channel. Here we investigate further the link between feet and parasitic polarities by modelling explicitly these polarities. We show that the prominence lateral feet appear naturally, above secondary photospheric inversion lines and we describe the morphological change of feet as parasitic polarities evolve. This approach is applied to an observed filament in Hα with the MSDP on the German VTT (Tenerife) where SOHO/MDI magnetograms are available. We show that the shape of the prominence is defined by the distribution of the dips in the computed magnetic configuration. Then we analyse the topology of the magnetic field using the quasi-separatrix layers (QSLs) method. We describe the basic changes in the topology as the parasitic polarities evolve, in particular how the configuration pass from an OX to an OF topology. We find a correspondance between the computed QSLs and some of the chromospheric brightenings, observed around the feet of filaments in the y line (Ca II, 8542 Angstroms). It confirms the deduced magnetic configuration and shows that energy release is present at a low level in the complex topology of the filament configuration. Title: The Postflare Loops and the Nearby Active Chromosphere of 1992 June 26: Addendum Authors: Malherbe, J. -M.; Tarbell, T.; Wiik, J. E.; Schmieder, B.; Frank, Z.; Shine, R. A.; van Driel-Gesztelyi, L. Bibcode: 1998ApJ...495..502M Altcode: Video segments are presented that were processed from a quantitative study of the dynamics of the evolution of Hα postflare loops developed after a large solar flare. The high spatial resolution of the Swedish Vacuum Solar Telescope (SVST) at La Palma provided a unique set of data for such an event. Title: Asymmetric Magnetic Field Distribution in Active Regions Authors: Cauzzi, Gianna; van Driel-Gesztelyi, Lidia Bibcode: 1998ASPC..140..105C Altcode: 1998ssp..conf..105C No abstract at ADS Title: Evolution of the Magnetic Field and Chromospheric Fine Structure in a Filament Channel Authors: van Driel-Gesztelyi, L.; Mein, P.; Mein, N.; Schmieder, B.; Malherbe, J. -M.; Aulanier, G.; Démoulin, P.; Deforest, C.; Staiger, J. Bibcode: 1998ASPC..155..321V Altcode: 1998sasp.conf..321V No abstract at ADS Title: Evolution and Decay of Active Regions (Invited review) Authors: van Driel-Gesztelyi, L. Bibcode: 1998ASPC..155..202V Altcode: 1998sasp.conf..202V No abstract at ADS Title: Reorganization of solar magnetic field by a flare event Authors: Manoharan, P. K.; van Driel-Gesztelyi, L.; Pick, M.; Démoulin, P. Bibcode: 1998BASI...26..319M Altcode: No abstract at ADS Title: Non potentiality of coronal loops above active regions Authors: Aulanier, G.; Schmieder, B.; Démoulin, P.; van Driel-Gesztelyi, L.; Deforest, C. Bibcode: 1998ASPC..155..105A Altcode: 1998sasp.conf..105A No abstract at ADS Title: Filament Disparition Brusque and CME - September 25-26, 1996 Event Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Aulanier, G.; Demoulin, P.; Martens, P. C. H.; Zarro, D.; Deforest, C.; Thompson, B.; St. Cyr, C.; Kucera, T.; Burkepile, J. T.; White, O. R.; Hanaoka, Y.; Nitta, N. Bibcode: 1998ASPC..150..366V Altcode: 1998IAUCo.167..366V; 1998npsp.conf..366V No abstract at ADS Title: 3-D Modelling of a Filament Observed in Hα and with SOHO Authors: Aulanier, G.; Schmieder, B.; Démoulin, P.; Mein, N.; van Driel-Gesztelyi, L.; Mein, P.; Vial, J. C.; Deforest, C. Bibcode: 1998ESASP.417..217A Altcode: 1998cesh.conf..217A No abstract at ADS Title: A study of activity in interacting sunspot groups Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Hénoux, J. -C. Bibcode: 1998PAICz..88...13S Altcode: No abstract at ADS Title: 3-D Modelling of a Filament Observed in Hα and with SOHO/MDI Authors: Aulanier, G.; Démoulin, P.; van Driel-Gesztelyi, L.; Mein, P.; Deforest, C. Bibcode: 1998ASPC..155..326A Altcode: 1998sasp.conf..326A No abstract at ADS Title: Evolution of a reversed polarity active region NOAA 7912 in the photosphere, the chromosphere and the corona. Authors: van Driel-Gesztelyi, L.; Baranyi, T.; Mein, N.; Cader-Sroka, B.; Rudawy, P.; Mein, P.; Rompolt, B.; Schmieder, B.; Malherbe, J. -M.; Willson, R.; Kile, J. N.; Raoult, A. Bibcode: 1998joso.proc..103V Altcode: The authors follow the evolution and activity of NOAA 7912, a reversed polarity region, in the photosphere (Kitt Peak magnetograms and Debrecen white-light photoheliograms), chromosphere (MSDP instrument mounted on the German VTT at Tenerife), and the corona (Yohkoh/SXT, Nançay radioheliograph and the VLA) between October 12-20, 1995. They find that in spite of the high shear and creation of several mixed-polarity regions through flux emergence, the flares in the group did not exceed the M-class level. This might be due to the fact that the highly inclined bipolar fields emerging in the following part of the primary reversed dipole were relatively small and quickly "consumed" by cancellation enhanced by sunspot motions. On the other hand, the presence of high shear and minor fast-moving parasitic polarities in NOAA 7912 was sufficient to produce eruptive events like X-ray jets with important coronal and interplanetary effects. Title: X-Ray Jets and Their Radio Signatures at Metric and Centimeter Wavelenths Authors: van Driel-Gesztelyi, L.; Willson, R. F.; Kile, J. N.; Raoult, A.; Klein, L.; Mein, N.; Rudawy, P.; Cader, B.; Rompolt, B.; Schmieder, B.; Mein, P.; Malherbe, J. M. Bibcode: 1998ASPC..154..707V Altcode: 1998csss...10..707V On October 19, 1995 at 10:30 UT and 17:00 UT, two semi-homologous X-ray jets were observed with the Yohkoh/SXT from AR 7912, a region having a reversed polarity group with vortex-like Hα fibril pattern and X-ray loops. The jets appeared over a mixed magnetic polarity region in the vicinity of the leading spot. The first event was also observed with the Nancay radio heliograph at 167, 236, and 327 MHz. Type III activity, indicating the presence of electron beams, superimposed on a noise-storm was clearly visible. Type III activity first appeared at 10:25 UT, coincident with the onset of the X-ray jet, at 164 MHz and 236 MHz close to the storm position, and in the direction of the X-ray jet. At 10:28:40 UT a new group of sources appeared eastward of the former activity, which may correspond to another jet branch along a more easterly path seen in the ohkoh} images. The second X-ray jet event was also observed with the Very Large Array (VLA) at 6.2, 20.7, and 91.6 cm. For this event, VLA snapshot maps at 6.2 and 20.7 cm reveal low-brightness temperature changes in source structure at the site of the X-ray jet during the preburst, impulsive, and decay phases. The VLA 91.6 cm observations also show noise storm emission above the active region but there is no clear temporal correlation between this later X-ray jet and the impulsive decimetric bursts that were observed during this period. Although the X-ray observations show that the two jets had similar temperatures, emission measures, speeds and trajectories they appear to have had dissimilar metric responses to these events. This surprising result may question our understanding of the process of electron beam acceleration in jets. Title: Making Sense of Sunspot Decay. I. Parabolic Decay Law and Gnevyshev-Waldmeier Relation Authors: Petrovay, K.; van Driel-Gesztelyi, L. Bibcode: 1997SoPh..176..249P Altcode: 1997astro.ph..6029P In a statistical study of the decay of individual sunspots based on DPR data we find that the mean instantaneous area decay rate is related to the spot radius ro and the maximum radius ro as D = CD r/ro, CD = 32.0±0.26 MSH day -1. This implies that sunspots on the mean follow a parabolic decay law; the traditional linear decay law is excluded by the data. The validity of the Gnevyshev-Waldmeier relationship between the maximum area A 0 and lifetime T of a spot group, A0/T ≃10 MSH day-1, is also demonstrated for individual sunspots. No evidence is found for a supposed supergranular `quantization' of sunspot areas. Our results strongly support the recent turbulent erosion model of sunspot decay while all other models are excluded. Title: Magnetic reconnection driven by emergence of sheared magnetic field. Authors: Schmieder, B.; Aulanier, G.; Demoulin, P.; van Driel-Gesztelyi, L.; Roudier, T.; Nitta, N.; Cauzzi, G. Bibcode: 1997A&A...325.1213S Altcode: Recurrent subflares (Class C) were observed in the NOAA 7608 active region on 27 October 1993. From multi-wavelength observations (white-light, magnetic field, H-alpha, X-ray), obtained during a coordinated campaign between Pic du Midi and Yohkoh, it appears that these flares were double ribbon flares caused by new flux emergence. As the flare begins, the X-ray emission observed with Yohkoh/SXT is loop-shaped with the axis almost parallel to the magnetic inversion line, while during the flare development, X-ray loops appear at the location of the emerging flux. The extrapolation of the photospheric magnetic field in a linear force-free field configuration allows identification of the magnetic configuration given by the flares. The Hα flare ribbons are located at the intersections of the computed quasi-separatrice layers (QSLs) with the chromosphere. We show that the initial loop-shaped X-ray emission region is in fact formed by several smaller loops directed in a nearly orthogonal direction with their feet anchored close to or in the Hα ribbons. During the flare development there are X-ray loops which represent only one foot of open or largescale magnetic loops. For the studied flares the puzzling soft X-rays observations could only be understood with the help of Hα and magnetic data combined with a modeling of the coronal magnetic field. Further, from the deduced magnetic field topology, the width of the QSLs and our present knowledge of 3-D magnetic reconnection, we conclude that the flare was due to magnetic reconnection driven by emergence of sheared magnetic field impacting in the pre-existing coronal field. Title: Evidence of Magnetic Reconnection from Hα, Soft X-Ray and Photospheric Magnetic Field Observations Authors: Mandrini, C. H.; DÉmoulin, P.; BagalÁ, L. G.; Van Driel-Gesztelyi, L.; HÉnoux, J. C.; Schmieder, B.; Rovira, M. G. Bibcode: 1997SoPh..174..229M Altcode: A conventional view of magnetic reconnection is mainly based on the 2-D picture of an X-type neutral point, or on the extension of it to 3-D, and it is thought to be accompanied by flux transport across separatrices (places where the field-line mapping is discontinuous). This view is too restrictive when we realize the variety of configurations that are seen flaring. We designed an algorithm, called Source Method (SM), to determine the magnetic topology of active regions (ARs). The observed photospheric field was extrapolated to the corona using subphotospheric sources and the topology was defined by the link between these sources. Hα flare brightenings were found to be located at the intersection with the chromosphere of the separatrices so defined. These results and the knowledge we gained on the properties of magnetic field-line linkage, led us to generalize the concept of separatrices to `quasi-separatrix layers' (QSLs) and to design a new method (`quasi-separatrix layers method', QSLM) to determine the magnetic topology of ARs. QSLs are regions where the magnetic field-line linkage changes drastically (discontinuously when they behave like separatrices) and the QSLM can be applied to ARs where the photospheric field has been extrapolated using any kind of technique. In this paper we apply the QSLM to observed flaring regions presenting very different configurations and also to a decaying AR where a minor phenomenon, like an X-ray bright point (XBP), is observed. We find that the locations of flare and XBP brightenings are related to the properties of the field-line linkage of the underlying magnetic region, as expected from recent developments of 3-D magnetic reconnection. The extrapolated coronal field lines representing the structures involved in the analyzed events have their photospheric footpoints located at both sides of QSLs. Our results strongly support the hypothesis that magnetic reconnection is at work in various coronal phenomena, ranging from the less energetic ones to large-scale eruptions. Title: Post-Flare Loops of 26 June 1992 - IV. Formation and Expansion of Hot and Cool Loops Authors: Van Driel-Gesztelyi, L.; Wiik, J. E.; Schmieder, B.; Tarbell, T.; Kitai, R.; Funakoshi, Y.; Anwar, B. Bibcode: 1997SoPh..174..151V Altcode: Observations of the post-flare loops after the X3.9 flare which occurred on 25 June, 1992 at 20:11 UT by the Yohkoh/SXT in X-rays, as well as in Hα obtained at 5 different observatories, have provided a unique, longest ever, set of data for a study of the relationship between the hot and cool post-flare loops as they evolve. At any given time, the altitude difference between the hot X-ray loops of 6-7× 106 K and the cool Hα loops of 1.5× 104 K is related to the expansion rate of the loop systems and their cooling time. Therefore, measurements of the expansion rate and relative height of hot and cool loops can provide direct observational values for their cooling times. We measured the altitude of hot and cool loops for 15 and 19 hours, respectively, and found that the cooling time increased as the density of the loops decreased. We found a reasonably good agreement between the observed cooling times and those obtained from model calculations, although the observed values were always somewhat longer than the theoretical ones. Taking into account evolutionary effects, we also found similar shapes and configurations of hot and cool loops during the entire observing period and confirmed that, at any time, hot loops are at higher altitude than cool loops, suggesting that cool loops indeed evolve from hot loops. These results were used to check the validity of the reconnection model. Title: The Postflare Loops and the Nearby Active Chromosphere of 1992 June 26 Authors: Malherbe, J. -M.; Tarbell, T.; Wiik, J. E.; Schmieder, B.; Frank, Z.; Shine, R. A.; van Driel-Gesztelyi, L. Bibcode: 1997ApJ...482..535M Altcode: The main objective of this paper is to present a quantitative study of the dynamics of the evolution of Hα postflare loops developed after a large solar flare and the processed videos produced from the observations. The high spatial resolution of the Swedish Vacuum Solar Telescope (SVST) at La Palma has provided a unique set of data for such an event. A Gaussian fitting method is proposed to derive intensities and Doppler shifts from observations taken at three wavelengths (Hα center and Hα +/- 0.07 nm). Moving condensations or ``blobs'' of cold material provide transverse velocities, which, together with the radial component, enable us to derive their velocity vector magnitude. Plasma velocities are around free-fall velocities near the top of the loops but are significantly smaller close to their footpoints, suggesting a deceleration mechanism. The loops are anchored in the chromosphere, which shows tremendous activity in the active region and in the nearby ``quiet Sun.'' Spicules and ejection of plasmoids are also observed at the limb. Title: Solar Magnetic Field Events related to CMEs observed with SOHO (MDI, EIT, SUMER, LASCO) Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Wiik, J. E.; Thompson, B.; de Forest, C.; Saint Cyr, C.; Vial, J. -C.; Nitta, N.; Simnett, G. Bibcode: 1997IAUJD..19E..42S Altcode: We shall present two CMEs observed by LASCO during the minimum of activity of the Sun. These are associated with filament disparitions brusques (DB). CME and DB definitively seem to be consequences of global magnetic field instability, which causes reconnection of pre-existing field lines in the corona. We shall demonstrate how cancelling flux and converging magnetic field in photosphere may destabilize coronal streamers overlying one or two filament channels. Title: 3-D reconnection related to new emerging flux Authors: Schmeider, B.; Démoulin, P.; Aulanier, G.; Malherbe, J. M.; van Driel-Gesztelyi, L.; Mandrini, C. H.; Roudier, T.; Nitta, N.; Harra-Murnion, L. K. Bibcode: 1997AdSpR..19.1871S Altcode: We present evidences that emergence of new flux in the lower atmosphere leads to magnetic reconnection of field lines. In a first phase the phenomenon is observed in the chromosphere by the formation of dark filaments (arch filament system) which are overlaid by bright loops visible in soft X-rays. Different types of event appear according to the magnetic field configuration and the amount of energy involved. 3-D modelling of the photospheric magnetic field provides a new tool for understanding reconnection in real configurations. The observed chromospheric and coronal loops are good diagnostics for the modelling. We document our statement by examples obtained during coordinated campaigns with the Hα Multichannel Subtractive Double Pass spectrographs-MSDP (Pic du Midi and Tenerife) and the Yohkoh instruments. Title: Prominence Activity Related to CME Observed by SOHO, YOHKOH and Ground-Based Observatories Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Wiik, J. E.; Kucera, T.; Thompson, B.; de Forest, C.; Saint Cyr, C.; Simnett, G. M. Bibcode: 1997ESASP.404..663S Altcode: 1997cswn.conf..663S No abstract at ADS Title: Sunspot Decay as Turbulent Erosion of a Magnetic Flux Tube Authors: Petrovay, K.; van Driel-Gesztelyi, L. Bibcode: 1997ASPC..118..145P Altcode: 1997fasp.conf..145P Decisive evidence is presented against the validity of the conventional linear decay law for sunspots. Preliminary results from a statistical analysis of Debrecen Photoheliographic Results data show that the decay rate of sunspots is significantly slower in late phases of the decay than in earlier phases. Our findings are compatible with the predictions of a recently developed turbulent erosion model for sunspot decay. Title: East-West inclination of field lines in active regions Authors: Cauzzi, G.; van Driel-Gesztelyi, L. Bibcode: 1997MmSAI..68..487C Altcode: No abstract at ADS Title: Magnetic reconnection driven by an emerging flux. Authors: Aulanier, G.; Démoulin, P.; Schmieder, B.; Malherbe, J. M.; van Driel-Gesztelyi, L.; Roudier, T. Bibcode: 1997joso.proc...51A Altcode: No abstract at ADS Title: Analysis of long duration flares Authors: Harra-Murnion, L. K.; Plunkett, S. P.; Helsdon, S. F.; Phillips, K. J. H.; van Driel-Gesztelyi, L.; Schmieder, B.; Rompolt, B.; Akioka, M. Bibcode: 1997AdSpR..20.2333H Altcode: Yohkoh has observed many long duration events permitting a statistical study of the properties of these interesting events. We have selected ten flares for analysis which have durations between 5 and 20 hours, and size ranging from C to X GOES class. Employing the Soft X-ray Telescope, the Bragg Crystal Spectrometer, GOES spacecraft, and ground-based H_alpha data, we examine the morphology, temperature, emission measure, location of the hard X-ray source, non-thermal velocities and upflows of the plasma at different stages in the flare development. Our results are used to address the question of the energy source that maintains the hot plasma at temperatures of several million degrees for many hours. Title: Post-flare loops in the chromosphere and corona. Authors: van Driel-Gesztelyi, L.; Wiik, J. E.; Schmieder, B. Bibcode: 1997ASIC..494...85V Altcode: 1997topr.conf...85V Post-flare loops, which may last for several hours during the gradual phase of powerful flares, can provide spectacular limb events during solar eclipses. According to models, on-going magnetic reconnection keeps creating new loops at an ever-increasing altitude. The newly formed hot loops can cool down to chromospheric temperatures quickly, in a few minutes, or slowly, over a few hours, depending on their density. A good test of the model is to measure the altitude difference between loops observed at different wavelengths which show the loops at different stages of the cooling process. Title: Reorganization of the solar corona following a C4.7 flare Authors: van Driel-Gesztelyi, L.; Manoharan, P. K.; Pick, M.; Démoulin, P. P. Bibcode: 1997AdSpR..19.1883V Altcode: Yohkoh X-ray images, multifrequency two-dimensional observations of the Nancay Radioheliograph, Kitt Peak and Mees magnetograms provide a unique set of data with which to study a C4.7 long-duration flare that was observed close to the equator (S07, W11) on 25 Oct. 1994 at 09:49 UT. Linear force-free field extrapolations indicate a very high degree of non-potentiality in the active region. The X-ray flare started with the expansion of spectacular twisted loops. Fifteen minutes after the flare onset sporadic radio (type III) bursts were observed spreading over an area of almost <FR SHAPE="SOL">1<DE>3</DE></FR> of the solar disc and two remote X-ray brightenings appeared over quiet regions of opposite magnetic polarity located in on opposite hemispheres of the Sun. In the close vicinity of these remote brightenings two coronal holes formed. The timing and location of these events combined with the overall magnetic configuration provide evidence for a large-scale magnetic reconnection occurring between the expanding twisted loops and the overlying huge loops which inter-connect quiet solar regions. Title: Emerging Flux Tube Geometry and Sunspot Proper Motions Authors: van Driel-Gesztelyi, Lidia Bibcode: 1997ASPC..118...81V Altcode: 1997fasp.conf...81V As sunspots appear at the intersection of rising flux tubes with the photosphere, the observed proper motions of a bipolar sunspot pair is a good indicator of the geometry of the underlying emerging flux tube. An emerging bipole caused by a simple symmetric potential flux tube should display a symmetric divergence of the two spots in diametrically opposite directions, while the proper motions of bipolar spot-pairs belonging to tilted or/and twisted (non-potential) emerging flux tubes are more complicated: asymmetric, not diametrically opposite and may follow a curved pattern. Observation of such motions may help to prove that emerging flux tubes are tilted and frequently twisted, in good agreement with predictions by recent simulation studies. Title: Evidence for Large-Scale Solar Magnetic Reconnection from Radio and X-Ray Measurements Authors: Manoharan, P. K.; van Driel-Gesztelyi, L.; Pick, M.; Demoulin, P. Bibcode: 1996ApJ...468L..73M Altcode: Utilizing Yohkoh Soft X-ray Telescope and Nancay radioheliograph data, we present, for the first time, observations of expanding twisted X-ray loops and a series of nonthermal radio bursts that follow the loop expansion in time and space up to ~12' distance. The loops were produced during a long-duration C4.7 flare close to disk center on 1994 October 25 at 1049 UT. The series of radio bursts were observed on the southern hemisphere above a weak positive-polarity region. The Kitt Peak magnetogram shows the existence of a weak negative-polarity region on the northern hemisphere at the same heliolongitude. Simultaneously with the nonthermal radio bursts, we observed the appearance of two remote X-ray brightenings and subsequent formation of two coronal holes above these weak (quiet) magnetic regions of opposite polarity, which strongly suggest the involvement of these remote regions in the event. During the 6 hr--long gradual phase of the flare, new X-ray loop connections developed among the active region and the remote quiet regions. A nonthermal radio continuum emission originating from the active region was also observed. We propose that the series of radio bursts, two remote X-ray brightenings, and new coronal loop connections were all signatures of a large-scale reconnection process between the expanding twisted flare loops and overlying transequatorial loops connecting quiet-Sun regions. The reconnection was only partial; the external part of the overlying large-scale fields were pushed out in the solar wind by the expanding twisted loops, leading to the formation of the coronal holes. The interaction between the active region and the large-scale fields seemed to be active during the entire gradual phase of the flare. This scenario may also explain the measurement of high-energy electrons in the interplanetary medium from 74 deg south heliolatitude as observed by Ulysses. Title: 3D Magnetic Reconnection at an X-Ray Bright Point Authors: Mandrini, C. H.; Démoulin, P.; Van Driel-Gesztelyi, L.; Schmieder, B.; Cauzzi, G.; Hofmann, A. Bibcode: 1996SoPh..168..115M Altcode: On May 1, 1993, a flaring X-ray bright point (XBP) was observed for about 16 hours in the old, disintegrating, bipolar active region (AR) NOAA 7493. During this period, a minor magnetic bipole (1020 Mx) emerged in the region. We have found observational evidence showing that the XBP brightenings were due to magnetic reconnection between the new bipole and pre-existing plage fields. The aim of the present work is to substantiate with magnetic modelling what has been shown by the observations. For this purpose we extrapolate the observed photospheric magnetic fields in the linear force-free approximation and follow its evolution during the lifetime of the XBP. From the computed coronal field lines we determine the location of regions of drastic change in field-line linkage, called `quasi-separatrix layers' or QSLs. QSLs are open layers that behave physically like separatrices: the break down of ideal magnetohydrodynamics and the release of free magnetic energy may occur at these locations when their thickness is small enough. The extrapolated field lines, with photospheric footpoints on both sides of QSLs, match the observed chromospheric and coronal structures (arch filament system, XBP and faint X-ray loops (FXL)). We study also the evolution of the width of the QSL located over the new negative polarity pore: the calculated QSL is very thin (typically less than 100 m) during the lifetime of the XBP, but becomes much thicker (≥ 104 m) after the XBP has faded. Furthermore we show that peaks in X-ray brightness propagate along the FXL with a velocity of ≈ 670 km s-1, starting from the XBP location, implying that the energy is released where the emerging bipole impacts against pre-existing coronal loops. We discuss the possible mechanism of energy transport and conclude that the energy is conducted to the remote footpoints of the FXL by a thermal front. These results strongly support the supposition that the XBP brightness and flaring are due to the interaction of different flux systems, through 3D magnetic reconnection, at QSLs. Title: Post-Flare Loops of 26 June 1992, II Authors: Schmieder, B.; Heinzel, P.; Van Driel-Gesztelyi, L.; Lemen, J. R. Bibcode: 1996SoPh..165..303S Altcode: We observed the large post-flare loop system, which developed after the X 3.9 flare of 25 June 1992 at 20∶11 UT, in Hα with the Multichannel Subtractive Double Pass Spectrograph at Pic-du-Midi and in X-rays with the it Yohkoh/SXT instrument. Following the long-term development of cool and hot plasmas, we have determined the emission measure of the cool plasma and, for the first time, the temporal evolution of the hot-loop emission measure and temperature during the entire gradual phase. Thus, it was possible to infer the temporal variation of electron densities, leading to estimates of cooling times. A gradual decrease of the hot-loop emission measure was observed, from 4 × 1030 cm−5 at 23∶00 UT on 25 June 1992 to 3 × 1028 cm−5 at 13∶10 UT on 26 June 1992. During the same period, the temperature decreased only slowly from 7.2 to 6.0 × 106 K. Using recent results of NLTE modeling of prominence-like plasmas, we also derive the emission measure of cool Hα loops and discuss their temperature and ionisation degree. During two hours of Hα observations (11-13 hours after the flare) the averaged emission measure does not show any significant change, though the amount of visible cool material decreases and the volume of the loops increases. The emission measure in Hα, after correction for the Doppler-brightening effect, is slightly lower than in soft X-rays. Since the hot plasma seems to be more spatially extended, we arrive at electron densities in the range ninfesupho≤ ninfesupcool∼ 2 × 1010 cm−3 at the time of the Hα observations. Title: Evidence for Current-carrying Emerging Flux Authors: Leka, K. D.; Canfield, R. C.; McClymont, A. N.; van Driel-Gesztelyi, L. Bibcode: 1996ApJ...462..547L Altcode: To determine the relationship between electric currents and magnetic flux in emerging sunspots, we use observations of the morphology, proper motion, magnetic flux, and currents associated with several well-observed growing bipoles. Our target was NOAA Active Region 7260, which included a preexisting large spot and a fast-growing area of new magnetic flux. Magnetic bipoles in this region are well documented by X-ray images from the Yohkoh spacecraft and optical images and vector magnetograms from several ground-based observatories.

In this paper we show that (1) the Hα and X-ray structures associated with these bipoles do not agree with potential-field extrapolations of magnetograms; (2) proper motions imply that the flux bundles that make up these new bipoles are twisted before they emerge; (3) these new bipoles are cospatial with significant vertical electric currents; (4) the morphology, proper motion, and measured currents of these bipoles all imply the same sense of twist; (5) this sense of twist is the same as the large-scale twist of the preexisting large spot; and (6) the increase of these currents, as new flux emerges, is not consistent with their generation by photospheric motions.

We conclude that the new magnetic flux that emerged in this active region carried currents generated below the photosphere. Title: Flare Activity Associated with Large-Scale Loops in AR 7260 Authors: Nitta, N.; van Driel-Gesztelyi, L. Bibcode: 1996AAS...188.1901N Altcode: 1996BAAS...28..849N Active region NOAA AR 7260 (August 1992) is marked as one of the fastest growing regions in solar cycle 22 and has extensively been studied by several workers. We have learned from the Yohkoh SXT data that flares in this region were generally confined rather than eruptive. In addition to the flares, we notice the formation of large-scale X-ray loops connecting the large preceding spot and the emerging flux region as the latter became complexed. One of them produced a LDE after a cusp structure formed on top it. These loops were occasionally observed to erupt, perhaps responsible for coronal mass ejections. Even some of the apparently localized flares may have been due to interactions of compact loops with such large-scale loops. It is possible that they also caused sympathetic flares. We try to understand how such loops formed in the context of evolution of the region, which is known to have consisted of intrinsically twisted magnetic field. Title: Chromospheric ejections and their signatures in X-ray observed by YOHKOH Authors: Schmieder, B.; Mein, N.; Shibata, K.; van Driel-Gesztelyi, L.; Kurokawa, H. Bibcode: 1996AdSpR..17d.193S Altcode: 1996AdSpR..17..193S Surges, or condensations of chromospheric material, are commonly observed in active regions when new emerging magnetic flux (EMF) occurs. In order to study EMF-related phenomena in the corona, observing campaigns were organized with the Yohkoh X-ray satellite and ground based observatories. EMFs could be detected in magnetograms made in Potsdam and Hawaii, surge and arch filament system (AFS) events (on Oct 7 1991, May 1 1993, respectively) with the Multichannel Subtractive Double Pass instruments operating at Meudon and on the Canary Islands and with the Hida telescope at Kyoto University. Bright X-ray loops coincident with chromospheric surge activity were detected in the high resolution Yohkoh SXT images. We also found coincident brightness variations between an X-ray bright point (XBP) and the underlying chromospheric plage related to EMF. We interpret the appearance of AFS as condensation of material among magnetic field lines, the X-ray bright points as the result of a magnetic reconnection process, and surges as ejection of cold plasma bubbles squeezed between field lines as a result of reconnection. Title: Emerging flux and flares in NOAA 7260 Authors: Nitta, N.; van Driel-Gesztelyi, L.; Leka, K. D.; Shibata, K. Bibcode: 1996AdSpR..17d.201N Altcode: 1996AdSpR..17..201N We have studied the relation between flux emergence and flare activity in the active region NOAA 7260, using images from the Soft X-ray Telescope aboard the Yohkoh spacecraft and other supporting ground-based data. It is found that microflares start around the time of flux emergence as recorded in white-light data, which generally precedes a major flare by several hours. We interpret the microflares as due to fast reconnection that takes place intermittently in the slow reconnection stage while more energy is accumulated in preparation for a larger flare. Title: Flare Associated Large-Scale Magnetic Reconnection Authors: Manoharan, P. K.; van Driel-Gesztelyi, L.; Pick, M.; Demoulin, P. Bibcode: 1996ASPC..111..398M Altcode: 1997ASPC..111..398M Reports a unique set of observations, for a low heliolatitude flare, obtained with the Yohkoh satellite and the Nançay radioheliograph. This flare starts with the expansion of spectacularly twisted loops, followed by sporadic radio bursts (some of them are detected at high heliolatitude, ≡65°S), appearance of two remote X-ray brightenings and formation of two coronal holes on opposite hemispheres of the Sun. The timing and location of these events provide evidence for a large-scale magnetic reconnection between the expanding twisted flare loops and overlying huge loops inter-connecting quiet regions on the Sun. Title: Asymmetries in solar active regions and flux emergence models Authors: Cauzzi, G.; Moreno-Insertis, F.; van Driel-Gesztelyi, L. Bibcode: 1996ASPC..109..121C Altcode: 1996csss....9..121C No abstract at ADS Title: Beam Driven Return Current Instabilities and White-Light Flares Authors: Matthews, S. A.; Brown, J. C.; van Driel-Gesztelyi, L. Bibcode: 1996ASPC..111..304M Altcode: 1997ASPC..111..304M It has been shown that the low ionization levels in the deep chromosphere of solar flares can cause the return current driven by a thick target flare beam to be unstable to ion acoustic wave generation, contrary to previous conventional wisdom. The authors investigate the possibility that anomalous heating as a result of this instability may produce sufficient heating to power the white-light flare. Four white-light flares observed by Yohkoh are examined: 1991 Oct 27, 1991 Nov 15, 1992 Jan 26, and 1992 Feb 14. Title: X-Ray Bright Point Flares Due to Magnetic Reconnection Authors: Van Driel-Gesztelyi, L.; Schmieder, B.; Cauzzi, G.; Mein, N.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, P.; Staiger, J. Bibcode: 1996SoPh..163..145V Altcode: Ground-based optical observations coordinated with Yohkoh/SXT X-ray observations of an old, disintegrating bipolar active region AR NOAA 7493 (May 1, 1993) provided a multiwavelength data base to study a flaring `active region' X-ray bright point (XBP) of about 16 hr lifetime, and the activity related to it in different layers of the solar atmosphere. The XBP appeared to be related to a new minor bipole of about 1020 Mx. Superposed on a global evolution of soft X-ray brightness, the XBP displayed changes of brightness, lasting for 1-10 min. During the brightenings the XBP apparently had a spatial structure, which was (tiny) loop-like rather than point-like. The X-ray brightenings were correlated with chromospheric activity: (i) brightenings of underlying chromospheric faculae, and (ii) appearance of strong turbulent velocities in the arch filament system. We propose that the XBP brightenings were due to reconnection of the magnetic field lines (sketched in 3D) between the new bipole and a pre-existing plage field induced by the motion of one of the new pores (v = 0.2 km s−1) towards the plage, and that the XBP itself was a reconnected hot loop between them. Title: Hot and Cool Post-Flare Loops: Formation and Dynamics Authors: Schmieder, B.; Heinzel, P.; van Driel-Gesztelyi, L.; Wiik, J. E.; Lemen, J. Bibcode: 1996mpsa.conf..211S Altcode: 1996IAUCo.153..211S No abstract at ADS Title: Reconexión magnética en una región activa en decaimiento Authors: Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.; Schmieder, B.; Bagalá, L. G.; Rovira, M. G. Bibcode: 1996BAAA...40....5M Altcode: Se han obtenido observaciones desde Tierra (Hα y magnetogramas) coordinadas con el Soft X-ray Telescope (SXT), a bordo del satélite japonés Yohkoh, de una región activa bipolar en decaimiento. Estos datos constituyen la base para el estudio de un punto brillante en rayos X (PBX) y de la actividad relacionada con el mismo en distintas capas de la atmósfera solar. Las observaciones muestran que el PBX está relacionado con la aparición de un bipolo menor (~ 1020 Mx) y que su abrillantamiento continuo, así como sus aumentos de brillo esporádicos (``fulguraciones"), son el resultado de la reconexión entre el pequeño arco emergente (visto en Hα como un sistema de filamentos arqueados, SFA) y arcos mayores asociados al campo facular preexistente. Se ha extrapolado el campo magnético observado en la aproximación libre de fuerzas lineal y se ha seguido su evolución a lo largo de la vida del PBX. Se ha calculado la posición de las cuasiseparatrices (CSs) a partir del campo modelado. Las líneas de campo extrapoladas, cuyas bases fotosféricas se encuentran a ambos lados de las CSs, están de acuerdo con las estructuras cromosféricas y coronales observadas. Se ha calculado el espesor de la CD ubicada a lo largo de la polaridad negativa emergente, encontrándose que su variación está de acuerdo con la evolución de la intensidad del PBX; la CS es muy delgada durante la vida del PBX (~ 100 m), mientras que su espesor aumenta considerablemente (>= 10^4 m) cuando el PBX desaparece de las imágenes del SXT. Estos resultados señalan que el abrillantamiento y las ``fulguraciones" de este PBX se deben al proceso de reconexión en 3D que tiene lugar en las CSs. Title: Relative Altitude of Hot and Cool Post-Flare Loops Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Wiik, J. E.; Tarbell, T.; Heinzel, P.; Kitai, R.; Funakoshi, Y.; Anwar, B. Bibcode: 1996ASPC..111..359V Altcode: 1997ASPC..111..359V The authors collected a unique set of data obtained simultaneously at 4 different ground based observatories and with the Yohkoh satellite to study the relationship between hot X-ray and cool Hα post-flare loops as they evolved during the long gradual phase of the X3.9 flare which occurred on 25 June 1992. They found reasonably good agreement between the computed 'theoretical' cooling times and the 'observed' cooling times derived from the relative altitudes of hot and cool loops. Taking into account evolutionary effects, the authors also found similar shape and configuration of hot and cool loops during the entire observing period and confirmed that at any time hot loops are at higher altitude than cool loops, suggesting that cool loops indeed descend from hot loops. The results provide support for the reconnection model. Title: Signatures of New Emerging Flux in the Solar Atmosphere Authors: Schmieder, B.; Malherbe, J. M.; Mein, P.; Mein, N.; van Driel-Gesztelyi, L.; Roudier, T.; Nitta, N.; Harra-Murnion, L. K. Bibcode: 1996ASPC..111...43S Altcode: 1997ASPC..111...43S The emergence of new flux in the low atmosphere leads to magnetic reconnection of field lines. In a stable phase the phenomenon is observed in the chromosphere by the formation of dark filaments (arch filament system, AFS). The authors show how bright loops visible in soft X-rays are co-aligned with the AFS. Different types of events appear as the released energy increases. With less energetic phenomena than flares one observes surges, jets or X-ray bright points, according to the configuration of the field lines (open/closed). A low-level reconnection process is detectable as an X-ray bright point. If the energy is ≡1028ergs cm-3, one observes subflares. The authors document their statement by showing examples observed in coordinated observations obtained with the MSDP (Pic du Midi and Tenerife) and Yohkoh/SXT and BCS for the events occurring on Oct 5, 1994, Oct 27, 1993, and May 1, 1993. Title: 3D Magnetic Reconnection: Example of an X-Ray Bright Point Authors: Demoulin, P.; Mandrini, C. H.; van Driel-Gesztelyi, L.; Priest, E. R.; Henoux, J. C.; Schmieder, B. Bibcode: 1996ASPC..111...49D Altcode: 1997ASPC..111...49D In the classical view magnetic reconnection occurs at neutral points and implies transport of magnetic field-lines across separatrices. The authors show that reconnection may also occur in the absence of neutral points at so-called "quasi-separatrix layers" (QSLs), where there is a steep gradient in field-line linkage at the boundaries. Reconnection occurs in QSLs where the field-line velocity becomes larger than the allowed maximal plasma velocity or where the electric-current density becomes too great. The authors describe both a theoretical and an observed configuration. In the case of a simple sheared X-field they show that even a smooth continuous shear flow, imposed at the boundary, gives strong plasma jetting inside and parallel to the QSLs. Applying the QSL method to an X-ray bright point observed by Yohkoh, they find field lines in the extrapolated field which are on both sides of QSLs and which are in good agreement with loops observed in Hα and X-rays related to emerging flux. The evolution of the QSL width may explain the brightness evolution of the XBP. Title: Emerging Flux, Reconnection, and XBP Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Demoulin, P.; Mandrini, C.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, N.; Mein, P. Bibcode: 1996mpsa.conf..459V Altcode: 1996IAUCo.153..459V No abstract at ADS Title: Emerging flux seen by Yohkoh. Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Mandrini, C.; Démoulin, P.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, N.; Mein, P. Bibcode: 1996joso.proc..124V Altcode: No abstract at ADS Title: Active Region Evolution and Flare Activity Authors: Nitta, N.; van Driel-Gesztelyi, L.; Leka, K. D.; Hudson, H. S. Bibcode: 1996mpsa.conf..515N Altcode: 1996IAUCo.153..515N No abstract at ADS Title: Hα surges and associated Soft X-ray loops Authors: Schmieder, B.; Shibata, K.; van Driel-Gesztelyi, L.; Freeland, S. Bibcode: 1995SoPh..156..245S Altcode: A recurrent Hα surge was observed on 7 October, 1991 on the western solar limb with the Meudon MSDP spectrograph. The GOES satellite recorded X-ray subflares coincident with all three events. During two of the surges high-resolutionYohkoh Soft X-ray Telescope (SXT) images have been taken. Low X-ray loops overlying the active region where the surges occurred were continuously restructuring. A flare loop appeared at the onset of each surge event and somewhat separated from the footpoint of the surge. The loops are interpreted as causally related to the surges. It is suggested that surges are due to magnetic reconnection between a twisted cool loop and open field lines. Cold plasma bubbles or jets squeezed among untwisting magnetic field lines could correspond to the surge material. No detection was made of either X-ray emission along the path of the surges or X-ray jets, possibly because of the finite detection threshold of theYohkoh SXT. Title: The Magnetic Evolution of the Activity Complex AR:7260 - a Roadmap Authors: Leka, K. D.; Canfield, R. C.; Mickey, D. L.; van Driel-Gesztelyi, L.; Nitta, N.; Sakurai, T.; Ichimoto, K. Bibcode: 1994SoPh..155..301L Altcode: The active region NOAA 7260 rotated onto the north solar hemisphere as a mature bipole: a dominant negative-polarity sunspot with trailing plage and scattered small spots in attendance. The dominantp spot itself had strong magnetic fields and covered almost 400 × 10−6 of a solar hemisphere. For a period of seven days beginning 14 August, 1992 this active region displayed rapid and drastic evolution: no fewer than 50 magnetic bipoles emerged in the area trailing the large sunspot, increasing the region's magnetic flux by more than 1022 Mx. This new group of sunspots formed a complexβγδ configuration with twoδ spots and a high degree of magnetic shear. Title: A Yohkoh search for ``black-light flares'' Authors: van Driel-Gesztelyi, Lidia; Hudson, Hugh S.; Anwar, Bachtiar; Hiei, Eijiro Bibcode: 1994SoPh..152..145V Altcode: 1994svs..coll..145V; 1994IAUCo.143..145V Calculations which predict that a phenomenon analogous to stellar negative pre-flares could also exist on the Sun were published by Hénouxet al. (1990), and Aboudarhamet al., (1990), who showed that at the beginning of a solar white-light flare (WLF) event an electron beam can cause a transient darkening before the WLF emission starts, under certain conditions. They named this event a "black light flare" (BLF). Such a BLF event should appear as diffuse dark patches lasting for about 20 seconds preceding the WLF emission, which would coincide with intense and impulsive hard X-ray bursts. The BLF location would be at (or in the vicinity of) the forthcoming bright patches. Their predicted contrast depends on the position of the flare on the solar disc and on the wavelength band of the observation. Title: Erratum: A study of surges and flares within an active region Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Gerlei, O.; Simnett, G. M. Bibcode: 1994SoPh..151..399S Altcode: No abstract at ADS Title: Relationship between electric currents, photospheric motions, chromospheric activity, and magnetic field topology Authors: van Driel-Gesztelyi, L.; Hofmann, A.; Demoulin, P.; Schmieder, B.; Csepura, G. Bibcode: 1994SoPh..149..309V Altcode: Through coordinated observations made during the Max'91 campaign in June 1989 in Potsdam (magnetograms), Debrecen (white light and Hα), and Meudon (MSDP), we follow the evolution of the sunspot group in active region NOAA 5555 for 6 days. The topology of the coronal magnetic field is investigated by using a method based on the concept of separatrices - applied previously (Mandriniet al., 1991) to a magnetic region slightly distorted by field-aligned currents. The present active region differs by having significant magnetic shear. We find that the Hα flare kernels and the main photospheric electric current cells are located close to the intersection of the separatrices with the chromosphere, in a linear force-free field configuration adapted to the observed shear. Sunspot motions, strong currents, isolated polarities, or intersecting separatrices are not in themselves sufficient to produce a flare. A combination of them all is required. This supports the idea that flares are due to magnetic reconnection, when flux tubes with field-aligned currents move towards the separatrix locations. Title: Evidence for Twisted Emerging Flux in NOAA AR 7260 Authors: Leka, K. D.; van Driel-Gesztelyi, L.; Canfield, R. C. Bibcode: 1994ASPC...68..145L Altcode: 1994sare.conf..145L No abstract at ADS Title: Diagnostics of Twisted Flux Emergence (noaa AR7260) Authors: Leka, K. D.; van Driel-Gesztelyi, L.; Anwar, B.; Canfield, R. C.; Hudson, H. S.; Metcalf, T. R.; Mickey, D. L.; Nitta, N.; Kurokawa, H. Bibcode: 1994xspy.conf...25L Altcode: No abstract at ADS Title: Flares in Active Region NOAA 7260 Authors: Nitta, N.; van Driel-Gesztelyi, L.; Leka, K. D.; Sakurai, T.; Shibata, K.; Ichimoto, K.; Canfield, R. C.; Wülser, J. -P.; Metcalf, T. R.; Mickey, D. L. Bibcode: 1994xspy.conf..111N Altcode: No abstract at ADS Title: Emerging Flux Tube Geometry and Sunspot Proper Motions Authors: van Driel-Gesztelyi, L.; Leka, K. D. Bibcode: 1994ASPC...68..138V Altcode: 1994sare.conf..138V No abstract at ADS Title: Twisted Flux Tubes and Sunspot Motions in AR 5555 Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Schmieder, B.; Hofmann, A.; Csepura, G. Bibcode: 1994emsp.conf..115V Altcode: No abstract at ADS Title: A Study of Surges and Flares Within an Active Region Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Gerlei, O.; Simnett, G. M. Bibcode: 1993SoPh..146..163S Altcode: Active region 2684 was observed by the Solar Maximum Mission and ground-based observatories simultaneously for over 12 hours on September 23, 1980. During these observations, recurrent surges were detected above an area with complex parasitic magnetic polarity located at the periphery of the active region. The time evolution of the Hα surges, CIV brightenings and X-ray spikes leads to the conclusion that the energy source is in the corona, from magnetic reconnection. The energy is transported by energetic charged particles along the loops, thereby heating the chromosphere as the particles lose their energy. The divergent motion of the spots corresponding to small dipoles at the base of the surge indicates that there is important magnetic reorganisation. According to the magnetic field-line configuration (large loop or open structures), X-rays can (or cannot) be associated with surges. Title: Evidence for Twisted Emerging Flux: NOAA AR 7260 Authors: Leka, K. D.; van Driel-Gesztelyi, L.; Canfield, R. C.; Anwar, B.; Metcalf, T. R.; Mickey, D. L.; Nitta, N. Bibcode: 1993BAAS...25R1187L Altcode: No abstract at ADS Title: Common Evolution of Adjacent Sunspot Groups Authors: van Driel-Gesztelyi, L.; Csepura, G.; Nagy, I.; Gerlei, O.; Schmieder, B.; Rayrole, J.; Demoulin, P. Bibcode: 1993SoPh..145...77V Altcode: The evolution of two adjacent bipolar sunspot groups is studied using Debrecen full-disc, white-light photoheliograms and Hα filtergrams as well as Meudon magnetograms. The proper motions of the principal preceding spots of both groups show quite similar patterns; the spots move along almost parallel tracks and change the direction of their motion on the same day at almost the same heliographic longitude. Also, three simultaneous emergences of magnetic flux were observed in both groups. These observations support the idea that these adjacent sunspot groups were magnetically linked below the photosphere. Matching the extrapolated magnetic field lines with the chromospheric fibril structure appears to be different in the two groups since they indicate quite different model solutions for each group, i.e., a near-potential magnetic field configuration in the older group (1) and a twisted force-free field configuration in the younger group (2). The latter configuration could be created by a considerable twist of the main bunch of flux tubes in Group 2, which is reflected in the relative sunspot motions. It is also showed how this twist contributed to the formation of a filament between the two groups. Title: Evidence for magnetic reconnection in solar flares Authors: Demoulin, P.; van Driel-Gesztelyi, L.; Schmieder, B.; Hemoux, J. C.; Csepura, G.; Hagyard, M. J. Bibcode: 1993A&A...271..292D Altcode: From a study of the magnetic field topology in an active region, evidence is derived that solar flares are produced by magnetic reconnection. We study a complex group with two active regions (AR 25 t 1 and AR 2512) for three consecutive days, June 13-15 1980. The observed longitudinal magnetic field is used to model the coronal magnetic field by the potential field created by a series of magnetic charges. This computed field matches satisfactorily the Ho fibrils and the observed transverse field direction. A set of flares occurs principally in the northern group (AR 2511). During these three days, two different magnetic configurations in succession are responsible for the occurrence of these flares: first the intrusion of a new opposite flux in the following polarity, secondly the emergence of new flux between the main polarities. In this last case flares occurred, although the emerging bipole is almost parallel to the main bipole. We show that even in this bipolar configuration a separator is present and that observed H flare ribbons are located near the intersection of the computed separatrices with the photosphere. This provides strong support to a model where reconnection releases the stored magnetic energy. The induced evolution of the magnetic field forces reconnection along others separators. They are connected by magnetic field lines to fainter kernels. Title: Book reviews Authors: van Driel-Gesztelyi, L.; Meynet, G.; Gaizauskas, V.; Cook, J. W.; McKenna-Lawlor, S. M. P.; Garmany, C. D.; Jugaku, Jun; Lamers, Henny J. G. L. M.; Achterberg, A.; De Greve, J. P.; Dommanget, J.; van der Kruit, P. C. Bibcode: 1993SSRv...64..165V Altcode: No abstract at ADS Title: Rotation Rates of Active Nests on the Sun Authors: van Driel-Gesztelyi, L.; van der Zalm, E. B. J.; Zwaan, C. Bibcode: 1993ASPC...46..504V Altcode: 1993mvfs.conf..504V; 1993IAUCo.141..504V No abstract at ADS Title: Book Review: Solar observations: techniques and interpretation / Cambridge U Press, 1991 Authors: van Driel Gesztelyi, L. Bibcode: 1993SSRv...64..167V Altcode: 1993SSRv...64..167S; 1993SSRv...64..167G No abstract at ADS Title: Book Review: Opening the frontiers in solar research / Pergamon, 1991 Authors: van Driel-Gesztelyi, Lidia; Bumba, V.; van Driel Gesztelyi, L. Bibcode: 1992SoPh..141..203V Altcode: 1992SoPh..141..203F No abstract at ADS Title: Active Nests on the Sun Authors: van Driel-Gesztelyi, Lidia; van der Zalm, Ed B. J.; Zwaan, Cornelis Bibcode: 1992ASPC...27...89V Altcode: 1992socy.work...89V No abstract at ADS Title: Conditions for flare and filament formation in interacting solar active regions Authors: Schmieder, B.; Henoux, J. -C.; van Driel-Gesztelyi, L.; Simnett, G. M. Bibcode: 1991A&A...244..533S Altcode: The evolution of two interacting sunspot groups of different ages is traced over a period of three days. The photospheric velocity field is obtained and compared with the general evolution of the region in an attempt to better understand the conditions that lead to flare activity and filament formation. It is shown that the observed photospheric motions can generate dc electric currents, which, in effect, could lead to energy storage. Title: Flares and filament formation due to the interaction between two active regions Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Hénoux, J. C.; Simnett, G. Bibcode: 1991AdSpR..11e..95S Altcode: 1991AdSpR..11...95S We follow the evolution (flare activity, filament formation) of two interacting active regions of different ages over three days, through observations at white-light, Hα, UV, and X-ray wavelengths. We show that the observed photospheric motions could generate DC electric currents and that they could lead to free energy storage. Flares were observed more-or-less simultaneously in remote locations of the sunspot group. This suggests that the same perturbation affected an ensemble of lines of force. Filament formation took place due to DC current generation by photospheric shearing motions with a velocity up to 350 m s-1. Title: Effect of Electron Beams during Solar Flares Authors: Aboudarham, J.; Henoux, J. C.; Brown, J. C.; van den Oord, G. H. J.; van Driel-Gesztelyi, L.; Gerlei, O. Bibcode: 1990SoPh..130..243A Altcode: Electron bombardment of the solar atmosphere has two effects: one is to enhance hydrogen recombination emission, the other is to increase the opacity via an increase of H− population. The first effect is the most important in the upper part of the atmosphere and the second in the lower part. We predict that, when enhanced absorption dominates in the part of the atmosphere where radiation originates, there will be a decrease in the white-light emission, leading to a `negative flare', or what we call a `Black-Light Flare'. This phenomenon occurs only for a short duration, not more than ∼ 20 s. `Black-Light Flares' have already been observed in the case of flare stars and we suggest here that they could also be present on the Sun, just prior to a White-Light Flare. Title: Homologous and Homologous like Microwave Solar Radio Bursts Authors: Trevisan, R. H.; Sawant, H. S.; Kalman, B.; Gesztelyi, L. Bibcode: 1990RMxAA..21..557T Altcode: ABSTRACT. Solar radio observations at 1.6 GHz were carried out in the month of July, 1985 by using 13.7 m diameter Itapetinga antenna with time resolution of 3 ms. Homologous Bursts, with total duration of about couple of seconds and repeated by some seconds were observed associated with Homologous H- flares. These H- flares were having periodicities of about 40 min. Observed long periodicities were attributed to oscillation of prominences, and small periods were attributed to removal of plasma from the field interaction zone. Also observed are "Homologous-Like" bursts. These bursts are double peak bursts with same time profile repeating in time. In addition to this, the ratio of the total duration of the bursts to time difference in the peaks of bursts remain constant. Morphological studies of these bursts have been presented. Keq tuoit : SUN-BURSTS - SUN-FLARE Title: Black and white flares? Authors: Henoux, J. -C.; Aboudarham, J.; Brown, J. C.; van den Oord, G. H. J.; van Driel-Gesztelyi, L. Bibcode: 1990A&A...233..577H Altcode: It is shown that the nonthermal ionization of a solar flare atmosphere by beam bombardment can result, in the initial stages of a flare, in dimunitions in the continuum solar flare brightness (termed 'black light flares'). The most favorable conditions for observing this diagnostic phenomenon are investigated in terms of flare location and wavelength. In terms of bombarding beam parameters, electron beams of large peak flux are shown to be the most favorable as are target atmospheres with minimal preheating. Title: Asymmetric Flux Loops in Active Regions - Part Two Authors: Petrovay, K.; Brown, J. C.; van Driel-Gesztelyi, L.; Fletcher, L.; Marik, M.; Stewart, G. Bibcode: 1990SoPh..127...51P Altcode: We propose that magnetic flux loops in the subphotospheric layers of the Sun are seriously asymmetrical as a consequence of the drag force exerted on them because of the different rotational rate of the surrounding plasma. In numerical models of stationary slender flux loops in the plane parallel approximation we show that a serious tilt is both possible and probable. Observational facts (see van Driel-Gesztelyi and Petrovay, 1989; Paper I) strongly support the case for high asymmetry. The different stability of p and f spots may also be related to such an asymmetry. Title: Asymmetric flux loops in active regions, I Authors: van Driel-Gesztelyi, L.; Petrovay, K. Bibcode: 1990SoPh..126..285V Altcode: 1990SoPh..126..285G We investigate asymmetries of bipolar sunspot groups. We find that the magnetic field distribution of simple bipolar sunspot groups is significantly asymmetrical: the polarity inversion line is usually nearer to the main following polarity spot than to the main preceding one. This asymmetry grows with the age of the sunspot group. We suggest that this asymmetry has a causal link with two long-established asymmetries- the one in the proper motions of young sunspots, the other in the relative stability of p and f spots. Title: Negative Flares on the Sun Authors: van Driel-Gesztelyi, L.; Brown, J. C.; Hénoux, J. -C.; Aboudarham, J.; van den Oord, G. H. J.; Gerlei, O.; Fárnik, F. Bibcode: 1990PDHO....7..202V Altcode: 1990dysu.conf..202V; 1990ESPM....6..202V The authors showed that under certain conditions at the beginning of a solar white-light flare (WLF) event an electron beam can cause a transient darkening before the WLF emission starts. They propose optimal conditions for possible observation of solar negative flares and present an observation, which may be the first identified observation of such events. Title: Interaction between Bipolar Sunspot Groups Authors: Csepura, G.; van Driel-Gesztelyi, L.; Nagy, I.; Gerlei, O.; Schmieder, B.; Rayrole, J. Bibcode: 1990PDHO....7...88C Altcode: 1990ESPM....6...88C; 1990dysu.conf...88C The authors find some evidence for the interaction of two close-by developing sunspot groups. Title: Photospheric-induced destabilization and ejection of prominence material Authors: Raadu, M. A.; Schmieder, B.; Mein, N.; Gesztelyi, L. Bibcode: 1988A&A...197..289R Altcode: The sequence of events leading up to prominence activation in two different cases is studied. In one case, observed on September 3, 1980, strong velocity shears were produced indicating filament twisting. In the other case, observed on June 22, 1980, activation results in the ejection of prominence material. The paper presents new evidence for a common initial triggering mechanism, the birth or motion of pores at one end of the activated filament sections. This is taken as an indication of emerging magnetic flux and current induction in the filaments. The difference in the final results is partly due to the different ambient magnetic field structures. In particular in the case leading to material ejection there is a subsequent associated flare occurred indicating the storage of magnetic energy in the region. Models are proposed for the two sequences of events, clarifying the underlying similarities and interpreting the distinct features of the two sets of observations. Title: Solar Global Background Magnetic Field Changes Accompanying the Development of the White-Light Flare Region of April 1984 (NOAA 4474) Authors: Bumba, V.; Gesztelyi, L. Bibcode: 1988BAICz..39....1B Altcode: In investigating the large-scale distribution changes of solar background magnetic field during a wide time interval around the formation of this very complex region, it is demonstrated that this development must be taken as part of a global process in the solar atmosphere. Complete reorganizations are seen in the magnetic active longitude patterns and the solar magnetic-field sector structure, clearly related to its maximum stage. It is also shown that, at the same time, restructuralization of coronal holes took place. The relation of large-scale cellularlike structures to this development is also studied. It is concluded that the formation of this strong white-light flare region was casually related to the rebuilding of the global solar magnetic field. Title: Rotation of Individual Background Magnetic Field Components During the Formation of the White-Light Flare Region of April 1984 (NOAA 4474) Authors: Bumba, V.; Gesztelyi, L. Bibcode: 1987BAICz..38..351B Altcode: In the present continuation of their study of processes related to the development of the white-light flare region of April 1984, the authors pay greater attention to the problem of rotation rates of certain components of the background magnetic field, constituting the main patterns of the weak as well as strong fields, from three points of view: as they are demonstrated by the distribution of chromospheric filaments, from point of view of the existence of so-called "pivot points" (Mouradian et al., 1987) and of the rotation of the strongest magnetic flux sources. Title: Local rigid rotation and the emergence of active centres Authors: Mouradian, Z.; Martres, M. J.; Soru-Escaut, I.; Gesztelyi, L. Bibcode: 1987A&A...183..129M Altcode: Deviations from the mean solar rotation rule of filaments are frequent. They correspond to real physical behaviour. Using filaments as tracers, limited solar areas of rigid rotation are observed: these are "pivot points" around which the filaments rotate during two or more successive rotations. It is shown that a relation exists between the pivot points and Active Centres: many Active Centres appear close to a pivot point whatever their latitude, whereas filaments which reveal the classical differential rotation do not generate any Active Centres. The magnetic flux emergence is associated in time with apparent reduced speed of the filament tilt about the pivot point. Some examples show that the relation exists using a reduced time scale of several days as well. The new Active Centre may destroy or displace the associated pivot point. Title: Photospheric Induced Destabilization and Ejection of Prominence Material Authors: Raadu, M. A.; Schmieder, B.; Mein, N.; Gesztelyi, L. Bibcode: 1987HvaOB..11..105R Altcode: The cause of the sudden activation of solar prominences is not clear. The authors present observations of two cases which were preceded by the emergence and motion of pores (new flux) in the near vicinity of the filaments, which seem to be closely related to the process which triggered the filament destabilization. These observations may be well described by a theoretical model in which the new flux interacts with the older "stable" magnetic field. Title: High flare activity and redistribution of solar global magnetic fields. Authors: Bumba, V.; Hejna, L.; Gesztelyi, L. Bibcode: 1987PAICz..66..129B Altcode: 1987eram....1..129B The authors demonstrate that both in the global scale and in the scale of large and complex active regions the high flare activity is closely related to the changes in the whole background magnetic field distribution. Title: Starspot proper motion in HK Lac. Authors: Oláh, K.; Gesztelyi, L.; Holl, A. Bibcode: 1987PAICz..70...95O Altcode: 1987eram....5...95O HK Lac is a long period RS CVn system with complex behaviour due to spots on the surface of the primary. Significant spot changes occur on long time scales (years), sometimes changes are seen over a few stellar rotation (months). The authors try to interpret these occasional events as spot proper motions on the primary star of the system. Title: Sunspot groups as tracers of radial differential rotation. Authors: Gesztelyi, L.; Pap, J. Bibcode: 1987PAICz..66...77G Altcode: 1987eram....1...77G Measurements of the proper motions of young bipolar sunspot groups show that these groups rotate faster than the surrounding photosphere. The faster proper motion of the young sunspot groups as well as the 24 days periodicity of the young active spot areas might indicate that the young sunspots are connected to the deeper regions of the Sun which rotate faster than the photosphere. Thus, the sunspot groups in the early stage of their life would be an indicator of rotation of the deeper layers of the Sun. Title: Filament eruption connected to photospheric activity. Authors: Simon, G.; Gesztelyi, L.; Schmieder, B.; Mein, N. Bibcode: 1986NASCP2442..229S Altcode: 1986copp.nasa..229S Two cases of activation of filaments that occured in regions of intense magnetic activity was studied. The simultaneous observations from Debrecen Observatory (white light and H alpha filtergram), and from Meudon Observatory (magnetogram, MSDP dopplergram and intensity maps in H alpha) gave a complementary set of data from which can be produced evidence of the influence of the photospheric magnetic field on the destabilization process of the filaments. On June 22, 1980, the eruption of the filament is associated with the motion of pores, which are manifestations of emerging flux knots. On September 3, 1980, the twisting motions in the filament are associated to the birth of a pore in its neighborhood. These observations are discussed. Title: White light flares and atmospheric modeling (Working Group report). Authors: Machado, M. E.; Avrett, E. H.; Falciani, R.; Fang, C.; Gesztelyi, L.; Henoux, J. -C.; Hiei, E.; Neidig, D. F.; Rust, D. M.; Sotirovski, P.; Svestka, Z.; Zirin, H. Bibcode: 1986lasf.conf..483M Altcode: The authors give a short summary of their discussions, and a set of recommendations which may help in the study of white light flare emission processes. Title: Motion of small sunspots in a channel Authors: Gesztelyi, L. Bibcode: 1986CoSka..15..251G Altcode: In the old bipolar sunspot group in Hale region 17117 new fluxes emerged. Numerous small spots became settled to a curved shape channel around the old leader spot. During 5 days (11 - 15 Sept. 1980) the spots were emerging and moving along this channel or joined it, irrespective of their polarities. This channel of sunspot motion might be in connection with large-scale flows of photospheric or sub-photospheric layers, perhaps with supergranular flows. Title: Sunspot proper motions in connection with the white-light flare of 25 April 1984 Authors: Gesztelyi, L.; Kalman, B. Bibcode: 1986AdSpR...6f..21G Altcode: 1986AdSpR...6...21G During the descending phase of the present cycle of solar activity one of the largest events was the 3B/X13.0 white-light flare in NOAA Active Region No. 4474 near the eastern limb on 24/25 April 1984. We present a study of the evolution of the very complex and extended active region 4474, the proper motion of the sunspots and the changes in the magnetic field in connection with the large flare, with special emphasis on the magnetic shear and other possible types of motion leading to flare build-up, and following the flare. Title: White-light flare of 26 July 1981. Authors: Gesztelyi, L.; Karlicky, M.; Farnik, F.; Gerlei, O.; Valnicek, B. Bibcode: 1986lasf.conf..163G Altcode: 1986lasf.symp..163G Making use of series of white light heliograms the authors studied the development of a flare-active sunspot group in Hale region 17760, where a white-light flare (WLF) was observed on 26 July 1981. The WLF appeared in a disintegrating delta-configuration, where rapid motion of newly emerged spots and of separating fragments of older umbrae was shearing and distorting the magnetic field. On the basis of optical, X-ray and radio observations the authors analysed the WLF event. Some observational indications exist supporting the hypothesis that the WLF knots are situated in the places of concentrated electric current which electrically couples sub-photospheric, photospheric and higher layers. Provided this is true the WL emission has been interpreted as the response of deep layers of the solar atmosphere to the dissipation-spreading process propagating along the electric current system. Intensity of the WLF knots relatively to the photosphere has been deduced and the power emitted between 545 and 555 nm estimated. The total energy emitted by the WLF knots is roughly estimated. Title: Preflare Activity of Solar Prominences Authors: Simon, G.; Mein, N.; Mein, P.; Gesztelyi, L. Bibcode: 1984SoPh...93..325S Altcode: The preflare activity of a plage filament is analysed from Hα observations made with the Multichannel Subtractive Double Pass Spectrograph (MSDP) of the Meudon Solar Tower. The June 22, 1980 event is studied and interpreted in terms of preflare heating of a filament, connected to the rise of emerging flux, and the relative approach of pores of different magnetic polarity, prior to the onset of a two-ribbon flare. Title: Relationships of a growing magnetic flux region to flares Authors: Martin, S. F.; Bentley, R. D.; Schadee, A.; Antalova, A.; Kucera, A.; Dezső, L.; Gesztelyi, L.; Harvey, K. L.; Jones, H.; Livi, S. H. B.; Wang, J. Bibcode: 1984AdSpR...4g..61M Altcode: 1984AdSpR...4...61M Some sites for solar flares are known to develop where new magnetic flux emerges and becomes abutted against opposite polarity pre-existing magnetic flux (review by Galzauskas/1/). We have identified and analyzed the evolution of such flare sites at the boundaries of a major new and growing magnetic flux region within a complex of active regions, Hale No. 16918. This analysis was done as a part of a continuing study of the circumstances associated with flares in Hale Region 16918, which was designated as an FBS target during the interval 18 - 23 June 1980. We studied the initiation and development of both major and minor flares in Hα images in relation to the identified potential flare sites at the boundaries of the growing flux region and to the general development of the new flux. This study lead to our recognition of a spectrum of possible relationships of growing flux regions to flares as follows: (1) intimate interaction with adjacent old flux - flare sites centered at new/old flux boundary, (2) forced or ``intimidated'' interaction in which new flux pushes old field having lower flux density towards a neighboring old polarity inversion line where a flare then takes place, (3) ``influential'' interaction - magnetic lines of force over an old polarity inversion line, typically containing a filament, reconnect to the new emerging flux; a flare occurs with erupting filament when the magnetic field overlying the filament becomes too weak to prevent its eruption, (4) inconsequential interaction - new flux region is too small or has wrong orientation for creating flare conditions, (5) incidental - flare occurs without any significant relationship to new flux regions. Title: Consecutive homologous flares and their relation to sunspot motions Authors: Gesztelyi, L. Bibcode: 1984AdSpR...4g..19G Altcode: 1984AdSpR...4Q..19G The large sunspot group in Hale region 17098 was in the decaying phase of its development when a new flux emerged in its middle part on 3 September 1980. This region displayed chromospheric activity all that day. By the next day the spot of highest velocity (0.37 km s-1) formed a delta-configuration with one of the spots of following polarity of the old group. The centre of the observed flares was not in the vicinity of this spot moving parallel to the magnetic zero-line, it was in the western part of the group, where two spots were moving nearly perpendicularly to the magnetic zero-line (v=0.09 km s-1), and deformed the border of a gulf of opposite polarity. With the changing configuration the form of the observed flares also changed. Title: The development of activity in Hale region 17098 (28 August - 8 September 1980). Authors: Gesztelyi, L.; Kondás, L. Bibcode: 1983PDHO....5..133G Altcode: 1984PDHO....5..133G Proper motions and some respects of chromospheric activities of a relatively simple large sunspot group were studied on the basis of full-disc white light photoheliograms and Hα filtergrams. The large sunspot group consisted of two, subsequently developing groups. In the course of their development, the umbrae of the two groups collided with each other. The observed chromospheric activity was relatively low. Title: Motions in the solar atmosphere associated with the white light flare of 11 July 1978 Authors: Dezso, L.; Gesztelyi, L.; Kondas, L.; Kovacs, A.; Rostas, S. Bibcode: 1980SoPh...67..317D Altcode: Series of white light heliograms and oft- and on-band Hα filtergrams have been obtained, with an average spatial resolution of 1″, to study the flare active McMath region 15403 on 11 July, 1978. A great number of accurate heliographic positions were determined for the umbrae, the white light flare patches and several bright Hα flare knots, as well as along the principal zero filament and an arch prominence. Using the measured heliographic coordinates of these objects their motions could be analyzed in some detail. The velocities of several different objects could be deduced from the coordinates. Since the heliocentric angle of the region was about 45°, the variation in apparent heliographic coordinates also enabled some variations in heights to be determined. Title: Umbral proper motions in the large sunspot group of the great flare activity of August 1972. Authors: Gesztelyi, L. Bibcode: 1977PDHO....3...93G Altcode: No abstract at ADS