Author name code: innes ADS astronomy entries on 2022-09-14 author:"Innes, Davina E." ------------------------------------------------------------------------ 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: Spectroscopic EUV observations of impulsive solar energetic particle event sources Authors: Bučík, R.; Fludra, A.; Gómez-Herrero, R.; Innes, D. E.; Kellett, B.; Kumar, R.; Mackovjak, Š. Bibcode: 2018A&A...617A..40B Altcode: 2018arXiv180700861B Context. Remote observations of solar flare ion acceleration are rather limited. Theoretical predictions for signatures of ion acceleration in extreme ultraviolet (EUV) line profiles have been made. Previous tests involve observations of flares with no evidence for energetic ions.
Aims: We aim to examine a source flare of impulsive (or 3He-rich) solar energetic particle events with EUV line spectroscopy.
Methods: We inspected all (more than 90) reported 3He-rich flares of the previous solar cycle 23 and found only 4 (recurrent) jets in the field of view of the Coronal Diagnostic Spectrometer (CDS) on board the Solar and Heliospheric Observatory (SOHO). The jet with the most suitable spatial and temporal coverage was analyzed in detail.
Results: Two enhanced (nonthermal) line broadenings are observed in the cooler chromospheric and transition-region lines, and they are localized near the site where the closed magnetic loops reconnect with the open magnetic field lines. The enhanced broadenings are both found at the sites with redshifts in the lines, surrounded by the region with blueshifts. One enhanced line broadening is associated with a small flare without energetic particle signatures, while another occurs just after the particle acceleration signatures of the main flare terminated.
Conclusions: The observed excess broadening does not appear to be directly related to the energetic ion production and motions. Further investigations are required that cover the critical impulsive phase of the flare, ideally with high-resolution spectrometers that are specifically pointed to the 3He-rich solar energetic particle source. Title: Initial features of an X-class flare observed with SUMER and TRACE Authors: Wang, T. J.; Solanki, S. K.; Innes, D. E.; Curdt, W. Bibcode: 2018arXiv180510418W Altcode: A class X1.5 flare started on the solar limb at 00:43 UT on 21 April 2002, which was associated with a CME observed at 01:27 UT by LASCO C2. The coordinated analyses of this flare include TRACE 195 Å images and SUMER spectra in lines of Fe XXI, Fe XII, and C II. We find that: 1) The flare began with a jet seen by TRACE, which was detected by SUMER in the C II line as a strong brightening with blue shifts up to 170 km s$^{-1}$. At that time only weak emission was detected in Fe XII and Fe XXI. 2) Subsequently, a weak looplike brightening started south of the jet, moving outwards with an average speed of about 150 km s$^{-1}$. The SUMER spectra responded this moving loop as separatingly brightenings, visible only in the Fe XXI line. The southwards moving component contains red- and blue-shifted emission features and has an apparent speed of $\sim$120 km s$^{-1}$. The absence of signatures in Fe XII and C II lines indicates that the moving weak loop seen by TRACE corresponds to the emission from very hot plasma, in a blend line in the 195 Å bandpass due to Fe XXIV formed at T > 10 MK. 3) The trigger mechanism of the flare and associated CME can be interpreted in the same way as that proposed by Wang et al. (2002) for an event with similar initial features. Title: 3He-rich Solar Energetic Particles in Helical Jets on the Sun Authors: Bučík, Radoslav; Innes, Davina E.; Mason, Glenn M.; Wiedenbeck, Mark E.; Gómez-Herrero, Raúl; Nitta, Nariaki V. Bibcode: 2018ApJ...852...76B Altcode: 2017arXiv171109394B Particle acceleration in stellar flares is ubiquitous in the universe; however, our Sun is the only astrophysical object where energetic particles and their source flares can both be observed. The acceleration mechanism in solar flares, tremendously enhancing (up to a factor of 10,000) rare elements like 3He and ultra-heavy nuclei, has been puzzling for almost 50 years. Here we present some of the most intense 3He- and Fe-rich solar energetic particle events ever reported. The events were accompanied by nonrelativistic electron events and type-III radio bursts. The corresponding high-resolution, extreme-ultraviolet imaging observations have revealed for the first time a helical structure in the source flare with a jet-like shape. The helical jets originated in relatively small, compact active regions, located at the coronal-hole boundary. A mini-filament at the base of the jet appears to trigger these events. The events were observed with the two Solar Terrestrial Relations Observatories on the backside of the Sun, during the period of increased solar activity in 2014. The helical jets may be a distinct feature of these intense events that is related to the production of high 3He and Fe enrichments. Title: Evidence for Alfvén Waves in Source Flares of Impulsive Solar Energetic Particle Events Authors: Bucik, R.; Innes, D.; Mason, G. M.; Wiedenbeck, M. E.; Gomez-Herrero, R.; Nitta, N. Bibcode: 2017AGUFMSH44B..05B Altcode: Impulsive solar energetic particle events, characterised by a peculiar elemental composition with the rare elements like 3He and ultra-heavy ions enhanced by factors up to ten thousand above their thermal abundance, have been puzzling for almost 50 years. The solar sources of these events have been commonly associated with coronal jets, believed to be a signature of magnetic reconnection involving field lines open to interplanetary space. Here we present some of the most intense events, highly enriched in both 3He and heavier ions. The corresponding high-resolution, extreme-ultraviolet imaging observations have revealed for the first time a helical structure in the source flare with a jet-like shape. A mini-filament at the base of the jet appears to trigger these events. The events were observed with the two Solar Terrestrial Relations Observatories on the backside of the Sun, during the period of increased solar activity in 2014. During the last decade, it has been established that the helical motions in coronal jets represent propagating Alfvén waves. Revealing such magnetic-untwisting waves in the solar sources of highly enriched events in this study is consistent with a stochastic acceleration mechanism. An examination of jets in previously reported impulsive solar energetic particle events indicates that they tend to be large-scale blowout jets, sometimes cleanly showing a twisted configuration.The work of R. Bucik is supported by the Deutsche Forschungsgemeinschaft grant BU 3115/2-1. Title: Magnetoacoustic and Alfve'nic Black Holes with Hawking Radiation at Horizons Made of Magnephonons and Alphonons Authors: Gheibi, A.; Safari, H.; Innes, D. E. Bibcode: 2017arXiv170302503G Altcode: We introduce analogue black holes (BHs) based on ideal magnetohydrodynamic equations. Similar to acoustic BHs, which trap phonons and emit Hawking radiation (HR) at the sonic horizon where the flow speed changes from super- to sub-sonic, in the horizon of magnetoacoustic and Alfvénic BHs, the magnetoacoustic and Alfve'n waves will be trapped and emit HR made of quantized vibrations similar to phonons which we call magnephonons and Alphonons. We proposed that magnetoacoustic and Alfve'nic BHs may be created in the laboratory using a tube with variable cross section embedded in a uniform magnetic field, and a super-magnetoacoustic or a super-Alfve'nic flow. We show that the Hawking temperature for both BHs is a function of the background magnetic field, number density of fluid, and radius of the tube. For a typical setup, the temperature is estimated to be about 0.0266 K. Title: Association of Impulsive Solar Energetic Particle Events With Large-Scale Coronal Waves Authors: Bucik, R.; Innes, D.; Mason, G. M.; Wiedenbeck, M. E. Bibcode: 2016AGUFMSH41D..07B Altcode: Impulsive or 3He-rich solar energetic particle (SEP) events have been commonly associated with EUV jets and narrow CMEs which are believed to be the signatures of magnetic reconnection involving field lines open to interplanetary space. The elemental and isotopic fractionation in these events are thought to be caused by processes confined to the flare sites. In addition to their anomalous abundances, 3He-rich SEPs show puzzling energy spectral shapes varying from rounded forms to power laws where the later are characteristics of shock acceleration. In this study we identify 32 impulsive SEP events observed by the ACE near the Earth during the solar minimum period 2007-2010 and examine their solar sources with the high resolution STEREO EUV images. Leading the Earth, STEREO-A provided for the first time a direct view on impulsive SEP event sources, which are generally located on the Sun's western hemisphere. Surprisingly, we find that about half of the impulsive SEP events in this survey are associated with large-scale EUV coronal waves. An examination of the wave front propagation and the coronal magnetic field connections suggests that the EUV waves may affect the injection of 3He-rich SEPs into interplanetary space. We found the events with jets tend to be associated with rounded spectra and the events with coronal waves with power laws. This suggests that coronal waves may be related to the unknown second stage mechanism commonly used to interpret spectral forms of 3He-rich SEPs. R. Bucik is supported by the Deutsche Forschungsgemeinschaft under grant BU 3115/2-1. Title: Association of 3He-Rich Solar Energetic Particles with Large-scale Coronal Waves Authors: Bučík, Radoslav; Innes, Davina E.; Mason, Glenn M.; Wiedenbeck, Mark E. Bibcode: 2016ApJ...833...63B Altcode: 2016arXiv160905346B Small, 3He-rich solar energetic particle (SEP) events have been commonly associated with extreme-ultraviolet (EUV) jets and narrow coronal mass ejections (CMEs) that are believed to be the signatures of magnetic reconnection, involving field lines open to interplanetary space. The elemental and isotopic fractionation in these events are thought to be caused by processes confined to the flare sites. In this study, we identify 32 3He-rich SEP events observed by the Advanced Composition Explorer, near the Earth, during the solar minimum period 2007-2010, and we examine their solar sources with the high resolution Solar Terrestrial Relations Observatory (STEREO) EUV images. Leading the Earth, STEREO-A has provided, for the first time, a direct view on 3He-rich flares, which are generally located on the Sun’s western hemisphere. Surprisingly, we find that about half of the 3He-rich SEP events in this survey are associated with large-scale EUV coronal waves. An examination of the wave front propagation, the source-flare distribution, and the coronal magnetic field connections suggests that the EUV waves may affect the injection of 3He-rich SEPs into interplanetary space. Title: Understanding IRIS Observations of Explosive Events in Terms of Magnetic Reconnection Mechanisms Authors: Guo, L.; Innes, D.; Huang, Y. M.; Bhattacharjee, A. Bibcode: 2016AGUFMSH42B..06G Altcode: The explosive events (here after mentioned as EEs) are thought to be driven by small-scale reconnection in the transition region. The reconnection processes take place in scales that are far below the resolution limit of existing imaging telescopes. Nevertheless, the spectral observations from the IRIS mission have the potential to reveal convolved information of density, temperature and velocity of a reconnection site; because reconnection mechanisms, e.g. Sweet-Parker, Petschek and the plasmoid instability, have reconnection sites with very different density and velocity structures and presumably spectral line profiles of different shapes. In our numerical experiments, we trigger different kinds of reconnection, produce synthetic line profiles of the reconnection sites and manage to build connections between reconnection mechanisms with shapes of line profiles. Subsequently, by comparing the observed line profiles of EEs with the synthetic line profiles from simulation, we could probe the reconnection processes that could not be directly observed on the Sun. We find that the observed spectra during EEs can be reproduced by a reconnection site with multiple magnetic islands and null points (or X points) that characterize the plasmoid instability but not by bi-directional jets that characterize the Sweet-Parker or the Petschek mechanism. This result suggests that if EEs are small-scale reconnection sites, then the reconnection proceeds via the plasmoid instability, rather than the Sweet-Parker or Petschek mechanism. Title: Undercover EUV Solar Jets Observed by the Interface Region Imaging Spectrograph Authors: Chen, N. -H.; Innes, D. E. Bibcode: 2016ApJ...833...22C Altcode: 2016arXiv161008149C It is well-known that extreme ultraviolet (EUV) emission emitted at the solar surface is absorbed by overlying cool plasma. Especially in active regions, dark lanes in EUV images suggest that much of the surface activity is obscured. Simultaneous observations from the Interface Region Imaging Spectrograph, consisting of UV spectra and slit-jaw images (SJI), give vital information with sub-arcsecond spatial resolution on the dynamics of jets not seen in EUV images. We studied a series of small jets from recently formed bipole pairs beside the trailing spot of active region 11991, which occurred on 2014 March 5 from 15:02:21 UT to 17:04:07 UT. Collimated outflows with bright roots were present in SJI 1400 Å (transition region) and 2796 Å (upper chromosphere) that were mostly not seen in Atmospheric Imaging Assembly (AIA) 304 Å (transition region) and AIA 171 Å (lower corona) images. The Si IV spectra show a strong blue wing enhancement, but no red wing, in the line profiles of the ejecta for all recurrent jets, indicating outward flows without twists. We see two types of Mg II line profiles produced by the jets spires: reversed and non-reversed. Mg II lines remain optically thick, but turn optically thin in the highly Doppler shifted wings. The energy flux contained in each recurrent jet is estimated using a velocity differential emission measure technique that measures the emitting power of the plasma as a function of the line-of-sight velocity. We found that all the recurrent jets release similar energy (108 erg cm-2 s-1) toward the corona and the downward component is less than 3%. Title: Observations of solar X-ray and EUV jets and their related phenomena Authors: Innes, D. E.; Bučík, R.; Guo, L. -J.; Nitta, N. Bibcode: 2016AN....337.1024I Altcode: 2016arXiv160303258I Solar jets are fast-moving, elongated brightenings related to ejections seen in both images and spectra on all scales from barely visible chromospheric jets to coronal jets extending up to a few solar radii. The largest, most powerful jets are the source of type III radio bursts, energetic electrons and ions with greatly enhanced 3He and heavy element abundances. The frequent coronal jets from polar and equatorial coronal holes may contribute to the solar wind. The primary acceleration mechanism for all jets is believed to be release of magnetic stress via reconnection; however the energy buildup depends on the jets' source environment. In this review, we discuss how certain features of X-ray and EUV jets, such as their repetition rate and association with radio emission, depends on their underlying photospheric field configurations (active regions, polar and equatorial coronal holes, and quiet Sun). Title: Relationship between supergranulation flows, magnetic cancellation and network flares Authors: Attie, R.; Innes, D. E.; Solanki, S. K.; Glassmeier, K. H. Bibcode: 2016A&A...596A..15A Altcode: 2017arXiv170510389A Context. Photospheric flows create a network of often mixed-polarity magnetic field in the quiet Sun, where small-scale eruptions and network flares are commonly seen.
Aims: The aim of this paper is (1) to describe the characteristics of the flows that lead to these energy releases, (2) to quantify the energy build up due to photospheric flows acting on the magnetic field, and (3) to assess its contribution to the energy of small-scale, short-lived X-ray flares in the quiet Sun.
Methods: We used photospheric and X-ray data from the SoHO and Hinode spacecraft combined with tracking algorithms to analyse the evolution of five network flares. The energy of the X-ray emitting thermal plasma is compared with an estimate of the energy built up due to converging and sheared flux.
Results: Quiet-Sun network flares occur above sites of converging opposite-polarity magnetic flux that are often found on the outskirts of network cell junctions, sometimes with observable vortex-like motion. In all studied flares the thermal energy was more than an order of magnitude higher than the magnetic free energy of the converging flux model. The energy in the sheared field was always higher than in the converging flux but still lower than the thermal energy.
Conclusions: X-ray network flares occur at sites of magnetic energy dissipation. The energy is probably built up by supergranular flows causing systematic shearing of the magnetic field. This process appears more efficient near the junction of the network lanes. Since this work relies on 11 case studies, our results call for a follow-up statistical analysis to test our hypothesis throughout the quiet Sun. Title: Energy spectra of 3He-rich solar energetic particles associated with coronal waves Authors: Bučík, R.; Innes, D. E.; Mason, G. M.; Wiedenbeck, M. E. Bibcode: 2016JPhCS.767a2002B Altcode: 2016arXiv160907266B In addition to their anomalous abundances, 3He-rich solar energetic particles (SEPs) show puzzling energy spectral shapes varying from rounded forms to power laws where the later are characteristics of shock acceleration. Solar sources of these particles have been often associated with jets and narrow CMEs, which are the signatures of magnetic reconnection involving open field. Recent reports on new associations with large-scale EUV waves bring new insights on acceleration and transport of 3He-rich SEPs in the corona. We examined energy spectra for 32 3He-rich SEP events observed by ACE at L1 near solar minimum in 2007-2010 and compared the spectral shapes with solar flare signatures obtained from STEREO EUV images. We found the events with jets or brightenings tend to be associated with rounded spectra and the events with coronal waves with power laws. This suggests that coronal waves may be related to the unknown second stage mechanism commonly used to interpret spectral forms of 3He-rich SEPs. Title: Flare-generated Shock Wave Propagation through Solar Coronal Arcade Loops and an Associated Type II Radio Burst Authors: Kumar, Pankaj; Innes, D. E.; Cho, Kyung-Suk Bibcode: 2016ApJ...828...28K Altcode: 2016arXiv160605056K This paper presents multiwavelength observations of a flare-generated type II radio burst. The kinematics of the shock derived from the type II burst closely match a fast extreme ultraviolet (EUV) wave seen propagating through coronal arcade loops. The EUV wave was closely associated with an impulsive M1.0 flare without a related coronal mass ejection, and was triggered at one of the footpoints of the arcade loops in active region NOAA 12035. It was initially observed in the 335 Å images from the Atmospheric Image Assembly with a speed of ∼800 km s-1 and it accelerated to ∼1490 km s-1 after passing through the arcade loops. A fan-spine magnetic topology was revealed at the flare site. A small, confined filament eruption (∼340 km s-1) was also observed moving in the opposite direction to the EUV wave. We suggest that breakout reconnection in the fan-spine topology triggered the flare and associated EUV wave that propagated as a fast shock through the arcade loops. Title: The SPICE Spectral Imager on Solar Orbiter: Linking the Sun to the Heliosphere Authors: Fludra, Andrzej; Haberreiter, Margit; Peter, Hardi; Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina; Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Davila, Joseph; Giunta, Alessandra; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo Bibcode: 2016cosp...41E.607F Altcode: The SPICE (Spectral Imaging of the Coronal Environment) instrument is one of the key remote sensing instruments onboard the upcoming Solar Orbiter Mission. SPICE has been designed to contribute to the science goals of the mission by investigating the source regions of outflows and ejection processes which link the solar surface and corona to the heliosphere. In particular, SPICE will provide quantitative information on the physical state and composition of the solar atmosphere plasma. For example, SPICE will access relative abundances of ions to study the origin and the spatial/temporal variations of the 'First Ionization Potential effect', which are key signatures to trace the solar wind and plasma ejections paths within the heliosphere. Here we will present the instrument and its performance capability to attain the scientific requirements. We will also discuss how different observation modes can be chosen to obtain the best science results during the different orbits of the mission. To maximize the scientific return of the instrument, the SPICE team is working to optimize the instrument operations, and to facilitate the data access and their exploitation. Title: Solar abundances with the SPICE spectral imager on Solar Orbiter Authors: Giunta, Alessandra; Haberreiter, Margit; Peter, Hardi; Vial, Jean-Claude; Harrison, Richard; Parenti, Susanna; Innes, Davina; Schmutz, Werner; Buchlin, Eric; Chamberlin, Phillip; Thompson, William; Bocchialini, Karine; Gabriel, Alan; Morris, Nigel; Caldwell, Martin; Auchere, Frederic; Curdt, Werner; Teriaca, Luca; Hassler, Donald M.; DeForest, Craig; Hansteen, Viggo; Carlsson, Mats; Philippon, Anne; Janvier, Miho; Wimmer-Schweingruber, Robert; Griffin, Douglas; Baudin, Frederic; Davila, Joseph; Fludra, Andrzej; Waltham, Nick; Eccleston, Paul; Gottwald, Alexander; Klein, Roman; Hanley, John; Walls, Buddy; Howe, Chris; Schuehle, Udo; Gyo, Manfred; Pfiffner, Dany Bibcode: 2016cosp...41E.681G Altcode: Elemental composition of the solar atmosphere and in particular abundance bias of low and high First Ionization Potential (FIP) elements are a key tracer of the source regions of the solar wind. These abundances and their spatio-temporal variations, as well as the other plasma parameters , will be derived by the SPICE (Spectral Imaging of the Coronal Environment) EUV spectral imager on the upcoming Solar Orbiter mission. SPICE is designed to provide spectroheliograms (spectral images) using a core set of emission lines arising from ions of both low-FIP and high-FIP elements. These lines are formed over a wide range of temperatures, enabling the analysis of the different layers of the solar atmosphere. SPICE will use these spectroheliograms to produce dynamic composition maps of the solar atmosphere to be compared to in-situ measurements of the solar wind composition of the same elements (i.e. O, Ne, Mg, Fe). This will provide a tool to study the connectivity between the spacecraft (the Heliosphere) and the Sun. We will discuss the SPICE capabilities for such composition measurements. Title: Analysis of UV and EUV emission from impacts on the Sun after 2011 June 7 eruptive flare Authors: Innes, D. E.; Heinrich, P.; Inhester, B.; Guo, L. -J. Bibcode: 2016A&A...592A..17I Altcode: 2016arXiv160306379I Context. On 2011 June 7 debris from a large filament eruption fell back to the Sun causing bright ultraviolet (UV) and extreme ultraviolet (EUV) splashes across the surface. These impacts may give clues on the process of stellar accretion.
Aims: The aim is to investigate how the impact emission is influenced by structures in the falling ejecta and at the solar surface.
Methods: We determine the UV and EUV light curves of a sample of impacts. The ballistic impact velocity is estimated from the ejection and landing times and, where possible, compared with the velocity derived by tracking the downflows in SDO/AIA and STEREO/EUVI images. Estimates of the column density before impact are made from the darkness of the falling plasma in the 193 Å channel.
Results: The impact velocities were between 230 and 450 km s-1. All impacts produced bright EUV emission at the impact site but bright UV was only observed when the impacting fragments reached the chromosphere. There was no clear relation between EUV intensity and kinetic energy. Low UV to EUV intensity ratios (IUV/IEUV) were seen (I) from impacts of low column-density fragments; (II) when splashes, produced by some impacts, prevented subsequent fragments from reaching the chromosphere; and (III) from an impact in an active region. The earliest impacts with the lowest velocity (~250 km s-1) had the highest IUV/IEUV.
Conclusions: The IUV/IEUV decreases with impact velocity, magnetic field at the impact site, and EUV ionising flux. Many of the infalling fragments dissipate above the chromosphere either due to ionisation and trapping in magnetic structures, or to them encountering a splash from an earlier impact. If the same happens in accreting stars then the reduced X-ray compared to optical emission that has been observed is more likely due to absorption by the trailing stream than locally at the impact site. Title: Association of 3He-rich solar energetic particles with large-scale coronal waves Authors: Bucik, Radoslav; Innes, Davina; Guo, Lijia; Mason, Glenn M.; Wiedenbeck, Mark Bibcode: 2016cosp...41E.260B Altcode: Impulsive or 3He-rich solar energetic particle (SEP) events have been typically associated with jets or small EUV brightenings. We identify 30 impulsive SEP events from ACE at L1 during the solar minimum period 2007-2010 and examine their solar sources with high resolution STEREO-A EUV images. At beginning of 2007, STEREO-A was near the Earth while at the end of the investigated period, when there were more events, STEREO-A was leading the Earth by 90°. Thus STEREO-A provided a better (more direct) view on 3He-rich flares generally located on the western Sun's hemisphere. Surprisingly, we find that about half of the events are associated with large-scale EUV coronal waves. This finding provides new insights on acceleration and transport of 3He-rich SEPs in solar corona. It is believed that elemental and isotopic fractionation in impulsive SEP events is caused by more localized processes operating in the flare sites. The EUV waves have been reported in gradual SEP events in association with fast coronal mass ejections. To examine their role on 3He-rich SEPs production the energy spectra and relative abundances are discussed. R. Bucik is supported by the Deutsche Forschungsgemeinschaft under grant BU 3115/2-1. Title: Evidence for a Common Acceleration Mechanism for Enrichments of 3He and Heavy Ions in Impulsive SEP Events Authors: Mason, Glenn M.; Nitta, Nariaki V.; Wiedenbeck, Mark E.; Innes, Davina E. Bibcode: 2016ApJ...823..138M Altcode: We have surveyed the period 1997-2015 for a rare type of 3He-rich solar energetic particle (SEP) event, with enormously enhanced values of the S/O ratio, that differs from the majority of 3He-rich events, which show enhancements of heavy ions increasing smoothly with mass. Sixteen events were found, most of them small but with solar source characteristics similar to other 3He-rich SEP events. A single event on 2014 May 16 had higher intensities than the others, and curved Si and S spectra that crossed the O spectrum above ∼200 keV nucleon-1. Such crossings of heavy-ion spectra have never previously been reported. The dual enhancement of Si and S suggests that element Q/M ratio is critical to the enhancement since this pair of elements uniquely has very similar Q/M ratios over a wide range of temperatures. Besides 3He, Si, and S, in this same event the C, N, and Fe spectra also showed curved shape and enhanced abundances compared to O. The spectral similarities suggest that all have been produced from the same mechanism that enhances 3He. The enhancements are large only in the high-energy portion of the spectrum, and so affect only a small fraction of the ions. The observations suggest that the accelerated plasma was initially cool (∼0.4 MK) and was then heated to a few million kelvin to generate the preferred Q/M ratio in the range C-Fe. The temperature profile may be the distinct feature of these events that produces the unusual abundance signature. Title: IRIS observations and MHD simulations of explosive events in the transition region of the Sun Authors: Guo, Lijia; Innes, Davina; Huang, Yi-Min; Bhattacharjee, Amitava Bibcode: 2016SPD....4710102G Altcode: Small-scale explosive events on the Sun are thought to be related to magnetic reconnection. While Petschek reconnection has been considered as a reconnection mechanism for explosive events on the Sun for quite a long time, the fragmentation of a current sheet in the high-Lundquist-number regime caused by the plasmoid instability has recently been proposed as a possible mechanism for fast reconnection. The actual reconnection sites are too small to be resolved with images but these reconnection mechanisms, Petschek and the plasmoid instability, have very different density and velocity structures and so can be distinguished by high-resolution line profiles observations. We use high-resolution sit-and-stare spectral observations of the Si IV line, obtained by the IRIS spectrometer, to identify sites of reconnection, and follow the development of line profiles. The aim is to obtain a survey of typical line profiles produced by small-scale reconnection events in the transition region and compare them with synthetic line profiles from numerical simulations of a reconnecting current sheet to determine whether reconnection occurs via the plasmoid instabilty or the Petschek mechanism. Direct comparison between IRIS observations and numerical results suggests that the observed Si IV profiles can be reproduced with a fragmented current layer subject to plasmoid instability but not by bi-directional jets that characterise the Petschek mechanism. This result suggests that if these small-scale events are reconnection sites, then fast reconnection proceeds via the plasmoid instability, rather than the Petschek mechanism during small-scale reconnection on the Sun. Title: Observations of solar flares with IRIS and SDO Authors: Li, D.; Innes, D. E.; Ning, Z. J. Bibcode: 2016A&A...587A..11L Altcode: 2015arXiv151205147L Flare kernels brighten simultaneously in all Solar Dynamics Observatory (SDO) Atmospheric Imaging Assembly (AIA) channels making it difficult to determine their temperature structure. The Interface Region Imaging Spectrograph (IRIS) is able to spectrally resolve Fe xxi emission from cold chromospheric brightenings, so it can be used to infer the amount of Fe xxi emission in the 131 Å AIA channel. We use observations of two small solar flares seen by IRIS and SDO to compare the emission measures (EMs) deduced from the IRIS Fe xxi line and the AIA 131 Å channel to determine the fraction of Fe xxi emission in flare kernels in the 131 Å channel of AIA. Cotemporal and cospatial pseudo-raster AIA images are compared with the IRIS results. We use multi-Gaussian line fitting to separate the blending chromospheric emission so as to derive Fe xxi intensities and Doppler shifts in IRIS spectra. We define loop and kernel regions based on the brightness of the 131 Å and 1600 Å intensities. In the loop regions the Fe xxi EMs are typically 80% of the 131 Å values, and range from 67% to 92%. Much of the scatter is due to small misalignments, but the largest site with low Fe xxi contributions was probably affected by a recent injection of cool plasma into the loop. In flare kernels the contribution of Fe xxi increases from less than 10% at the low-intensity 131 Å sites to 40-80% in the brighter kernels. Here the Fe xxi is superimposed on bright chromospheric emission and the Fe xxi line shows blueshifts, sometimes extending up to the edge of the spectral window, 200 km s-1. The AIA 131 Å emission in flare loops is due to Fe xxi emission with a 10-20% contribution from continuum, Fe xxiii, and cooler background plasma emission. In bright flare kernels up to 52% of the 131 Å is from cooler plasma. The wide range seen in the kernels is caused by significant structure in the kernels, which is seen as sharp gradients in Fe xxi EM at sites of molecular and transition region emission. Title: Numerical Modeling of Supra-Arcade Downflows Authors: Huang, Y. M.; Bhattacharjee, A.; Guo, L.; Innes, D. Bibcode: 2015AGUFMSH21A2388H Altcode: Abstract Supra-arcade downflows (SADs) are elongated features usually observed above post-eruption flare arcades, with low emission, low density, and high temperature. Although SADs have been observed and studied extensively, their physical interpretation and mechanism remain not well understood and controversial. In our recent numerical and observational studies, we suggest that SADs may be due to Rayleigh-Taylor type instabilities occurring at the front of reconnection outflow jets as they encounter the underlying arcades (Innes et al. Astrophys. J. 796, 27; Guo et al. Astrophys. J. Lett., 796, L29). In this work, we further improve our three-dimensional magnetohydrodynamic model of SADs by incorporating viscous and resistive heating, anisotropic heat conduction, as well as line-tied lower boundary conditions. Synthetic SDO AIA emission measure profiles are calculated from simulation data and compared with observations. Title: IRIS Si IV Line Profiles: An Indication for the Plasmoid Instability during Small-scale Magnetic Reconnection on the Sun Authors: Innes, D. E.; Guo, L. -J.; Huang, Y. -M.; Bhattacharjee, A. Bibcode: 2015ApJ...813...86I Altcode: 2015arXiv150908837I Our understanding of the process of fast reconnection has undergone a dramatic change in the last 10 years driven, in part, by the availability of high-resolution numerical simulations that have consistently demonstrated the break-up of current sheets into magnetic islands, with reconnection rates that become independent of Lundquist number, challenging the belief that fast magnetic reconnection in flares proceeds via the Petschek mechanism which invokes pairs of slow-mode shocks connected to a compact diffusion region. The reconnection sites are too small to be resolved with images, but these reconnection mechanisms, Petschek and the plasmoid instability, have reconnection sites with very different density and velocity structures and so can be distinguished by high-resolution line-profile observations. Using IRIS spectroscopic observations we obtain a survey of typical line profiles produced by small-scale events thought to be reconnection sites on the Sun. Slit-jaw images are used to investigate the plasma heating and re-configuration at the sites. A sample of 15 events from 2 active regions is presented. The line profiles are complex with bright cores and broad wings extending to over 300 km s-1. The profiles can be reproduced with the multiple magnetic islands and acceleration sites that characterize the plasmoid instability but not by bi-directional jets that characterize the Petschek mechanism. This result suggests that if these small-scale events are reconnection sites, then fast reconnection proceeds via the plasmoid instability, rather than the Petschek mechanism during small-scale reconnection on the Sun. Title: Flarelike brightenings of active region loops observed with SUMER Authors: Wang, T. J.; Innes, D. E.; Solanki, S. K.; Curdt, W. Bibcode: 2015arXiv151000337W Altcode: Coronal loops on the east limb of the Sun were observed by SUMER on SOHO for several days. Small flare-like brightenings are detected very frequently in the hot flare line Fe~{\small XIX}. We find that the relatively intense events are in good coincidence with the transient brightenings seen by Yohkoh/SXT. A statistical analysis shows that these brightenings have durations of 5-84 min and extensions along the slit of 2-67 Mm. The integrated energy observed in Fe~{\small XIX} for each event is in the range of $3\times10^{18}-5\times10^{23}$ ergs, and the estimated thermal energy ranges from $10^{26}-10^{29}$ ergs. Application of the statistical method proposed by Parnell \& Jupp (2000) yields a value of 1.5 to 1.8 for the index of a power law relation between the frequency of the events and the radiated energy in Fe~{\small XIX}, and a value of 1.7 to 1.8 for the index of the frequency distribution of the thermal energy in the energy range $>10^{27}$ ergs. We examine the possibility that these small brightenings give a big contribution to heating of the active region corona. Title: Observations of EUV Waves in 3He-rich Solar Energetic Particle Events Authors: Bučík, R.; Innes, D. E.; Guo, L.; Mason, G. M.; Wiedenbeck, M. E. Bibcode: 2015ApJ...812...53B Altcode: 2015arXiv151204664B Small 3He-rich solar energetic particle (SEP) events with their anomalous abundances, markedly different from the solar system, provide evidence for a unique acceleration mechanism that operates routinely near solar active regions. Although the events are sometimes accompanied by coronal mass ejections (CMEs), it is believed that mass and isotopic fractionation is produced directly in the flare sites on the Sun. We report on a large-scale extreme-ultraviolet (EUV) coronal wave observed in association with 3He-rich SEP events. In the two examples discussed, the observed waves were triggered by minor flares and appeared concurrently with EUV jets and type III radio bursts, but without CMEs. The energy spectra from one event are consistent with so-called class-1 (characterized by power laws) 3He-rich SEP events, while the other with class-2 (characterized by rounded 3He and Fe spectra), suggesting different acceleration mechanisms in the two. The observation of EUV waves suggests that large-scale disturbances, in addition to more commonly associated jets, may be responsible for the production of 3He-rich SEP events. Title: Long-lived energetic particle source regions on the Sun Authors: Bučík, R.; Innes, D. E.; Chen, N. H.; Mason, G. M.; Gómez-Herrero, R.; Wiedenbeck, M. E. Bibcode: 2015JPhCS.642a2002B Altcode: 2015arXiv150702840B Discovered more than 40 years ago, impulsive solar energetic particle (SEP) events are still poorly understood. The enormous abundance enhancement of the rare 3He isotope is the most striking feature of these events, though large enhancements in heavy and ultra-heavy nuclei are also observed. Recurrent 3He-rich SEPs in impulsive events have only been observed for limited time periods, up to a few days which is typically the time that a single stationary spacecraft is magnetically connected to the source active regions on the Sun. With the launch of the two STEREO spacecraft we now have the possibility of longer connection time to solar active regions. We examined the evolution of source regions showing repeated 3He-rich SEP emissions for relatively long time periods. We found that recurrent 3He-rich SEPs in these long-lived sources occur after the emergence of magnetic flux. Title: Destabilization of a Solar Prominence/Filament Field System by a Series of Eight Homologous Eruptive Flares Leading to a CME Authors: Panesar, Navdeep K.; Sterling, Alphonse C.; Innes, Davina E.; Moore, Ronald L. Bibcode: 2015ApJ...811....5P Altcode: 2015arXiv150801952P Homologous flares are flares that occur repetitively in the same active region, with similar structure and morphology. A series of at least eight homologous flares occurred in active region NOAA 11237 over 2011 June 16-17. A nearby prominence/filament was rooted in the active region, and situated near the bottom of a coronal cavity. The active region was on the southeast solar limb as seen from the Solar Dynamics Observatory/Atmospheric Imaging Assembly, and on the disk as viewed from the Solar TErrestrial RElations Observatory/EUVI-B. The dual perspective allows us to study in detail behavior of the prominence/filament material entrained in the magnetic field of the repeatedly erupting system. Each of the eruptions were mainly confined, but expelled hot material into the prominence/filament cavity system (PFCS). The field carrying and containing the ejected hot material interacted with the PFCS and caused it to inflate, resulting in a step-wise rise of the PFCS approximately in step with the homologous eruptions. The eighth eruption triggered the PFCS to move outward slowly, accompanied by a weak coronal dimming. As this slow PFCS eruption was underway, a final “ejective” flare occurred in the core of the active region, resulting in strong dimming in the EUVI-B images and expulsion of a coronal mass ejection (CME). A plausible scenario is that the repeated homologous flares could have gradually destabilized the PFCS, and its subsequent eruption removed field above the acitive region and in turn led to the ejective flare, strong dimming, and CME. Title: Case studies of multi-day 3He-rich solar energetic particle periods Authors: Chen, Nai-hwa; Bučík, Radoslav; Innes, Davina E.; Mason, Glenn M. Bibcode: 2015A&A...580A..16C Altcode: 2015arXiv150604369C Context. Impulsive solar energetic particle events in the inner heliosphere show the long-lasting enrichment of 3He.
Aims: We study the source regions of long-lasting 3He-rich solar energetic particle (SEP) events
Methods: We located the responsible open magnetic field regions, we combined potential field source surface extrapolations with the Parker spiral, and compared the magnetic field of the identified source regions with in situ magnetic fields. The candidate open field regions are active region plages. The activity was examined by using extreme ultraviolet images from the Solar Dynamics Observatory (SDO) and STEREO together with radio observations from STEREO and WIND.
Results: Multi-day periods of 3He-rich SEP events are associated with ion production in single active region. Small flares or coronal jets are their responsible solar sources. We also find that the 3He enrichment may depend on the occurrence rate of coronal jets. Title: Forward Modelling of a Brightening Observed by AIA Authors: Price, D. J.; Taroyan, Y.; Innes, D. E.; Bradshaw, S. J. Bibcode: 2015SoPh..290.1931P Altcode: 2015SoPh..tmp...89P A comprehensive understanding of the different transient events is necessary for any eventual solution of the coronal heating problem. We present a cold loop whose heating caused a short-lived small-scale brightening that was observed by AIA. The loop was simulated using an adaptive hydrodynamic radiation code that considers the ions to be in a state of non-equilibrium. Forward modelling was used to create synthetic AIA intensity plots, which were tested against the observational data to confirm the simulated properties of the event. The hydrodynamic properties of the loop were determined. We found that the energy released by the heating event is within the canonical energy range of a nanoflare. Title: Plasmoid Instability Mediated Turbulent Reconnection, Simulations and Observations Authors: Huang, Yi-Min; Bhattacharjee, A.; Guo, Lijia; Innes, Davina Bibcode: 2015shin.confE..26H Altcode: Abstract It has been established that the Sweet-Parker current layer in high Lundquist number reconnection is unstable to the super-Alfvenic plasmoid instability. Past two-dimensional magnetohydrodynamic simulations have demonstrated that the plasmoid instability leads to a new regime where the Sweet-Parker current layer changes into a chain of plasmoids connected by secondary current sheets, and the averaged reconnection rate becomes nearly independent of the Lundquist number. In this work we present results from recent three-dimensional simulations in which the additional degree of freedom allows development of plasmoid instabilities at oblique angles, which interact and lead to self-generated turbulent reconnection. This turbulent state exhibits typical hallmarks of MHD turbulence, such as power-law spectra of both kinetic and magnetic energy fluctuations, as well as eddies elongated along the local magnetic field direction. The averaged reconnection rate is of the order of a hundredth of the characteristic Alfven speed, which is similar to the two-dimensional result. Because plasmoid instability mediated reconnection has very different density and velocity structures from classic Sweet-Parker and Petschek models, it is possible to distinguish between them by high-resolution line-profiles observations. Comparing the Si iv line profiles obtained by the IRIS spectrometer observations of transition region explosive events with synthetic line profiles from simulations suggests that plasmoid instability mediated reconnection is in better agreement with observations. Title: Study of Solar Energetic Particle Associations with Coronal Extreme-ultraviolet Waves Authors: Park, Jinhye; Innes, D. E.; Bucik, R.; Moon, Y. -J.; Kahler, S. W. Bibcode: 2015ApJ...808....3P Altcode: We study the relationship between large gradual solar energetic particle (SEP) events and associated extreme-ultraviolet (EUV) wave properties in 16 events that occurred between 2010 August and 2013 May and were observed by SDO, the Solar and Heliospheric Observatory (SOHO), and/or STEREO. We determine onset times, peak times, and peak fluxes of the SEP events in the SOHO/ERNE and STEREO/LET proton channels (6-10 MeV). The EUV wave arrival times and their speeds from the source sites to the spacecraft footpoints in the photosphere, which are magnetically connected to the spacecraft by Parker spiral and potential fields, are determined by spacetime plots from the full-Sun heliographic images created by combining STEREO-A and STEREO-B 195 Å and SDO 193 Å images. The SEP peak fluxes increase with the EUV wave speeds, and the SEP spectral indices become harder with the speeds. This shows that higher energetic particle fluxes are associated with faster EUV waves, which are considered as the lateral expansions of coronal-mass-ejection-driven shocks in the low corona. Title: A Prominence/filament eruption triggered by eight homologous flares Authors: Panesar, Navdeep K.; Sterling, Alphonse; Innes, Davina; Moore, Ronald Bibcode: 2015TESS....140805P Altcode: Eight homologous flares occurred in active region NOAA 11237 over 16 - 17 June 2011. A prominence system with a surrounding coronal cavity was adjacent to, but still magnetically connected to the active region. The eight eruptions expelled hot material from the active region into the prominence/filament cavity system (PFCS) where the ejecta became confined. We mainly aim to diagnose the 3D dynamics of the PFCS during the series of eight homologous eruptions by using data from two instruments: SDO/AIA and STEREO/EUVI-B, covering the Sun from two directions. The field containing the ejected hot material interacts with the PFCS and causes it to inflate, resulting in a discontinuous rise of the prominence/filament approximately in steps with the homologous eruptions. The eighth eruption triggers the PFCS to move outward slowly, accompanied by a weak coronal dimming. Subsequently the prominence/filament material drains to the solar surface. This PFCS eruption evidently slowly opens field overlying the active region, which results in a final ‘ejective’ eruption from the core of the active region. A strong dimming appears adjacent to the final eruption’s flare loops in the EUVI-B images, followed by a CME. We propose that the eight homologous flares gradually disrupted the PFCS and removed the overlying field above the active region, leading to the CME via the ‘lid removal’ mechanism. Title: Partial Reflection and Trapping of a Fast-mode Wave in Solar Coronal Arcade Loops Authors: Kumar, Pankaj; Innes, D. E. Bibcode: 2015ApJ...803L..23K Altcode: 2015arXiv150308165K We report on the first direct observation of a fast-mode wave propagating along and perpendicular to cool (171 Å) arcade loops observed by the Solar Dynamics Observatory/Atmospheric Imaging Assembly (AIA). The wave was associated with an impulsive/compact flare near the edge of a sunspot. The EUV wavefront expanded radially outward from the flare center and decelerated in the corona from 1060 to 760 km s-1 within ∼3-4 minutes. Part of the EUV wave propagated along a large-scale arcade of cool loops and was partially reflected back to the flare site. The phase speed of the wave was about 1450 km s-1, which is interpreted as a fast-mode wave. A second overlying loop arcade, orientated perpendicular to the cool arcade, is heated and becomes visible in the AIA hot channels. These hot loops sway in time with the EUV wave, as it propagated to and fro along the lower loop arcade. We suggest that an impulsive energy release at one of the footpoints of the arcade loops causes the onset of an EUV shock wave that propagates along and perpendicular to the magnetic field. Title: Magnetic balltracking: Tracking the photospheric magnetic flux Authors: Attie, R.; Innes, D. E. Bibcode: 2015A&A...574A.106A Altcode: 2014arXiv1412.8294A Context. One aspect of understanding the dynamics of the quiet Sun is to quantify the evolution of the flux within small-scale magnetic features. These features are routinely observed in the quiet photosphere and were given various names, such as pores, knots, magnetic patches.
Aims: This work presents a new algorithm for tracking the evolution of the broad variety of small-scale magnetic features in the photosphere, with a precision equal to the instrumental resolution.
Methods: We have developed a new technique to track the evolution of the individual magnetic features from magnetograms, called "magnetic balltracking". It quantifies the flux of the tracked features, and it can track the footpoints of magnetic field lines inferred from magnetic field extrapolation. The algorithm can detect and quantify flux emergence, as well as flux cancellation.
Results: The capabilities of magnetic balltracking are demonstrated with the detection and the tracking of two cases of magnetic flux emergence that lead to the brightening of X-ray loops. The maximum emerged flux ranges from 1018 Mx to 1019 Mx (unsigned flux) when the X-ray loops are observed.

Movies associated to Figs. 6 and 18 are available in electronic form at http://www.aanda.org Title: Persistent Energetic Ion Outbursts from the Sun Authors: Bucik, R.; Innes, D.; Mason, G. M. Bibcode: 2014AGUFMSH43A4183B Altcode: Following the greatest elongation in 2011, STEREO-A and -B, along with the near-Earth Solar Dynamics Observatory, have provided for the first time a view of the full solar surface. This allows continual tracking of solar active regions for their entire lifetime. With the advantage of a wide angular separation between the two STEREOs and the near-Earth Advanced Composition Explorer, we present the first report of multiple 3He-rich solar energetic particle (SEP) outbursts occurring in single active regions for relatively long time periods, lasting at least a quarter of a solar rotation. We identified several long-lasting 3He- or Fe-rich SEP sources with particle emissions successively observed at least on two of STEREO-B, ACE and STEREO-A spacecraft. Previous single spacecraft observations showed such energetic ion bursts over a limited time interval (about one day) presumably due to the loss of magnetic connection to the flare sites. These new observations reveal that the physical processes responsible for particle acceleration and escape from the Sun appear to be more continuous than previously thought. We discuss conditions in the solar sources which could lead to the reappearance of 3He-rich SEPs by comparing with the cases showing no such feature. Title: Rayleigh-Taylor Type Instabilities in the Reconnection Exhaust Jet as a Mechanism for Supra-arcade Downflows in the Sun Authors: Guo, L. -J.; Huang, Y. -M.; Bhattacharjee, A.; Innes, D. E. Bibcode: 2014ApJ...796L..29G Altcode: 2014arXiv1406.3305G Supra-arcade downflows (hereafter referred to as SADs) are low-emission, elongated, finger-like features observed in active region coronae above post-eruption flare arcades. Observations exhibit downward moving SADs intertwined with bright upward growing spikes. Whereas SADs are dark voids, spikes are brighter, denser structures. Although SADs have been observed for more than a decade, the mechanism of the formation of SADs remains an open issue. Using three-dimensional resistive magnetohydrodynamic simulations, we demonstrate that Rayleigh-Taylor-type instabilities develop in the downstream region of a reconnecting current sheet. The instabilities result in the formation of low-density coherent structures that resemble SADs, and high-density structures that appear to be spike-like. Comparison between the simulation results and observations suggests that Rayleigh-Taylor-type instabilities in the exhaust of reconnecting current sheets provide a plausible mechanism for observed SADs. Title: Secondary Rayleigh-Taylor Instabilities in the Reconnection Exhaust Jet: A Mechanism for Supra-Arcade Downflows in the Solar Corona Authors: Guo, L.; Bhattacharjee, A.; Huang, Y. M.; Innes, D. Bibcode: 2014AGUFMSM44B..02G Altcode: Supra-arcade downflows (hereafter referred to as SADs) are low-emission, elongated, finger-like features usually observed in active-region coronae above post-eruption flare arcades. Observations exhibit downward moving SADs intertwined with bright, upward moving spikes. Whereas SADs are dark voids, spikes are brighter, denser structures. Although SADs have been observed for decades, the mechanism for formation of SADs remains an open issue. Using high-Lundquist-number three-dimensional resistive MHD simulations, we demonstrate that secondary Rayleigh-Taylor type instabilities develop in the downstream region of a reconnecting current sheet. The instability results in the formation of low-density coherent structures that resemble SADs, intertwined with high-density structures that appear to be spike-like. Using SDO/AIA images, we highlight features that have been previously unexplained, such as the splitting of SADs at their heads, but are a natural consequence of instabilities above the arcade. Comparison with siumlations suggest that secondary Rayleigh-Taylor type instabilities in the exhaust of reconnecting current sheets provide a plausible mechanism for observed SADs and spikes. Although the plasma conditions are vastly different, analogous phenomena also occur in the Earth's magnetotail during reconnection. Title: Cool Plasma Observed in the FUV using IRIS Authors: Schmit, D. J.; Innes, D. Bibcode: 2014AGUFMSH51C4177S Altcode: Cool plasma in the outer solar atmosphere is commonly observed in prominences and coronal rain. Theory suggests that these phenomena are related to cooling, and analysis of observations provides a constraint on the time-dependent energetics of the chromosphere and corona. Using the IRIS SG and SJI datasets, we discuss new observations of molecular absorption features in the Si IV emission lines near 1400A. The presence of molecules above the transition region provides an extreme example of complex structure and dynamics at the chromosphere-corona interface. There are two morphological models that can explain the absorption features: cool plasma hundreds of kilometers above the photosphere or a localized transition region deeply embedded in the photosphere. We discuss the merit of these scenarios and introduce complementary IRIS observations of inverted temperature structure in Ellerman bombs and diffuse Si I continuum absorption above active region loops. Title: Observations of Supra-arcade Fans: Instabilities at the Head of Reconnection Jets Authors: Innes, D. E.; Guo, L. -J.; Bhattacharjee, A.; Huang, Y. -M.; Schmit, D. Bibcode: 2014ApJ...796...27I Altcode: 2014arXiv1401.4057I Supra-arcade fans are bright, irregular regions of emission that develop during eruptive flares above flare arcades. The underlying flare arcades are thought to be a consequence of magnetic reconnection along a current sheet in the corona. At the same time, theory predicts plasma jets from the reconnection sites which are extremely difficult to observe directly because of their low densities. It has been suggested that the dark supra-arcade downflows (SADs) seen falling through supra-arcade fans may be low-density jet plasma. The head of a low-density jet directed toward higher-density plasma would be Rayleigh-Taylor unstable, and lead to the development of rapidly growing low- and high-density fingers along the interface. Using Solar Dynamics Observatory/Atmospheric Imaging Assembly 131 Å images, we show details of SADs seen from three different orientations with respect to the flare arcade and current sheet, and highlight features that have been previously unexplained, such as the splitting of SADs at their heads, but are a natural consequence of instabilities above the arcade. Comparison with three-dimensional magnetohydrodynamic simulations suggests that SADs are the result of secondary instabilities of the Rayleigh-Taylor type in the exhaust of reconnection jets. Title: Hot explosions in the cool atmosphere of the Sun Authors: Peter, H.; Tian, H.; Curdt, W.; Schmit, D.; Innes, D.; De Pontieu, B.; Lemen, J.; Title, A.; Boerner, P.; Hurlburt, N.; Tarbell, T. D.; Wuelser, J. P.; Martínez-Sykora, Juan; Kleint, L.; Golub, L.; McKillop, S.; Reeves, K. K.; Saar, S.; Testa, P.; Kankelborg, C.; Jaeggli, S.; Carlsson, M.; Hansteen, V. Bibcode: 2014Sci...346C.315P Altcode: 2014arXiv1410.5842P The solar atmosphere was traditionally represented with a simple one-dimensional model. Over the past few decades, this paradigm shifted for the chromosphere and corona that constitute the outer atmosphere, which is now considered a dynamic structured envelope. Recent observations by the Interface Region Imaging Spectrograph (IRIS) reveal that it is difficult to determine what is up and down, even in the cool 6000-kelvin photosphere just above the solar surface: This region hosts pockets of hot plasma transiently heated to almost 100,000 kelvin. The energy to heat and accelerate the plasma requires a considerable fraction of the energy from flares, the largest solar disruptions. These IRIS observations not only confirm that the photosphere is more complex than conventionally thought, but also provide insight into the energy conversion in the process of magnetic reconnection. Title: Molecular absorption in transition region spectral lines Authors: Schmit, D. J.; Innes, D.; Ayres, T.; Peter, H.; Curdt, W.; Jaeggli, S. Bibcode: 2014A&A...569L...7S Altcode: 2014arXiv1409.1702S
Aims: We present observations from the Interface Region Imaging Spectrograph (IRIS) of absorption features from a multitude of cool atomic and molecular lines within the profiles of Si IV transition region lines. Many of these spectral lines have not previously been detected in solar spectra.
Methods: We examined spectra taken from deep exposures of plage on 12 October 2013. We observed unique absorption spectra over a magnetic element which is bright in transition region line emission and the ultraviolet continuum. We compared the absorption spectra with emission spectra that is likely related to fluorescence.
Results: The absorption features require a population of sub-5000 K plasma to exist above the transition region. This peculiar stratification is an extreme deviation from the canonical structure of the chromosphere-corona boundary. The cool material is not associated with a filament or discernible coronal rain. This suggests that molecules may form in the upper solar atmosphere on small spatial scales and introduces a new complexity into our understanding of solar thermal structure. It lends credence to previous numerical studies that found evidence for elevated pockets of cool gas in the chromosphere.

Movies associated to Figs. 1 and 2 are available in electronic form at http://www.aanda.org Title: On the Structure and Evolution of a Polar Crown Prominence/Filament System Authors: Panesar, N. K.; Innes, D. E.; Schmit, D. J.; Tiwari, S. K. Bibcode: 2014SoPh..289.2971P Altcode: 2014arXiv1402.4989P; 2014SoPh..tmp...50P Polar crown prominences, that partially circle the Sun's poles between 60° and 70° latitude, are made of chromospheric plasma. We aim to diagnose the 3D dynamics of a polar crown prominence using high-cadence EUV images from the Solar Dynamics Observatory (SDO)/AIA at 304, 171, and 193 Å and the Ahead spacecraft of the Solar Terrestrial Relations Observatory (STEREO-A)/EUVI at 195 Å. Using time series across specific structures, we compare flows across the disk in 195 Å with the prominence dynamics seen on the limb. The densest prominence material forms vertical columns that are separated by many tens of Mm and connected by dynamic bridges of plasma that are clearly visible in 304/171 Å two-colour images. We also observe intermittent but repetitious flows with velocity 15 km s−1 in the prominence that appear to be associated with EUV bright points on the solar disk. The boundary between the prominence and the overlying cavity appears as a sharp edge. We discuss the structure of the coronal cavity seen both above and around the prominence. SDO/HMI and GONG magnetograms are used to infer the underlying magnetic topology. The evolution and structure of the prominence with respect to the magnetic field seems to agree with the filament-linkage model. Title: Jets and Bombs: Characterizing IRIS Spectra Authors: Schmit, Donald; Innes, Davina Bibcode: 2014AAS...22432309S Altcode: For almost two decades, SUMER has provided an unique perspective on explosive events in the lower solar atmosphere. One of the hallmark observations during this tenure is the identification of quiet sun bi-directional jets in the lower transition region. We investigate these events through two distinct avenues of study: a MHD model for reconnection and the new datasets of the Interface Region Imaging Spectrograph (IRIS). Based on forward modeling optically thin spectral profiles, we find the spectral signatures of reconnection can vary dramatically based on viewing angle and altitude. We look to the IRIS data to provide a more complete context of the chromospheric and coronal environment during these dynamic events. During a joint IRIS-SUMER observing campaign, we observed spectra of multiple jets, a small C flare, and an Ellerman bomb event. We discuss the questions that arise from the inspection of these new data. Title: The Study of Solar Energetic Protons Associated with EUV Waves Authors: Park, Jinhye; Innes, Davina; Bucik, Radoslav; Moon, Yong-Jae; Kahler, Stephen W. Bibcode: 2014AAS...22412318P Altcode: We studied the relationship between solar energetic protons (SEPs) and extreme ultraviolet (EUV) wave properties between 2010 August and 2013 May observed by STEREO, SOHO and SDO. We determined the onset times, peak times and peak fluxes of the SEPs in SOHO ERNE and STEREO LET proton channel (6 - 10 MeV). Full Sun heliographic images created by combining STB 195Å, SDO 193Å, and STA 195Å were used for the analysis of the EUV waves. EUV wave arrival times at the spacecraft connecting points and their speed on the low corona were determined by space-time plots. It is noted that there is a significant correlation between the EUV wave arrival times and SEP onset times (r=0.73) but no SEP peak times. SEP peak fluxes increase with EUV wave speed (r=0.69) and the power law spectral index become harder with the EUV wave speed. This suggests that energetic protons are strongly associated with EUV waves, which is considered as the signature of CME shock in the low corona. Title: The SUMER Data in the SOHO Archive Authors: Curdt, W.; Germerott, D.; Wilhelm, K.; Schühle, U.; Teriaca, L.; Innes, D.; Bocchialini, K.; Lemaire, P. Bibcode: 2014SoPh..289.2345C Altcode: 2013arXiv1309.1314C We have released an archive of all observational data of the VUV spectrometer Solar Ultraviolet Measurements of Emitted Radiation (SUMER) on SOHO that have been acquired until now. The operational phase started with `first light' observations on 27 January 1996 and will end in 2014. Future data will be added to the archive when they become available. The archive consists of a set of raw data (Level 0) and a set of data that are processed and calibrated to the best knowledge we have today (Level 1). This communication describes step by step the data acquisition and processing that has been applied in an automated manner to build the archive. It summarizes the expertise and insights into the scientific use of SUMER spectra that has accumulated over the years. It also indicates possibilities for further enhancement of the data quality. With this article we intend to convey our own understanding of the instrument performance to the scientific community and to introduce the new, standard FITS-format database. Title: Investigating Molecular Hydrogen in Active Regions with IRIS Authors: Jaeggli, Sarah A.; Saar, Steven H.; Daw, Adrian N.; Innes, Davina Bibcode: 2014AAS...22432306J Altcode: Molecular hydrogen should be the most abundant molecular species in sunspots, but recent observations with IRIS show that its florescent signature is absent from above the sunspot umbra, but appears brightly during flares. In this poster we continue the analysis of FUV observations of H2 in active regions, examining the correlation between the intensity of the H2 lines and the lines of C II and Si IV which are responsible for their excitation. We particularly focus on differentiating places where H2 is abundant, holes in the chromospheric opacity where FUV photons can enter more deeply into the solar atmosphere, and places where the FUV radiation field is intense, as in flares. Title: Multi-spacecraft Observations of Recurrent 3He-rich Solar Energetic Particles Authors: Bučík, R.; Innes, D. E.; Mall, U.; Korth, A.; Mason, G. M.; Gómez-Herrero, R. Bibcode: 2014ApJ...786...71B Altcode: 2014arXiv1403.4856B We study the origin of 3He-rich solar energetic particles (<1 MeV nucleon-1) that are observed consecutively on STEREO-B, Advanced Composition Explorer (ACE), and STEREO-A spacecraft when they are separated in heliolongitude by more than 90°. The 3He-rich period on STEREO-B and STEREO-A commences on 2011 July 1 and 2011 July 16, respectively. The ACE 3He-rich period consists of two sub-events starting on 2011 July 7 and 2011 July 9. We associate the STEREO-B July 1 and ACE July 7 3He-rich events with the same sizeable active region (AR) producing X-ray flares accompanied by prompt electron events, when it was near the west solar limb as seen from the respective spacecraft. The ACE July 9 and STEREO-A July 16 events were dispersionless with enormous 3He enrichment, lacking solar energetic electrons and occurring in corotating interaction regions. We associate these events with a small, recently emerged AR near the border of a low-latitude coronal hole that produced numerous jet-like emissions temporally correlated with type III radio bursts. For the first time we present observations of (1) solar regions with long-lasting conditions for 3He acceleration and (2) solar energetic 3He that is temporarily confined/re-accelerated in interplanetary space. 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: The relation between solar jets and 3He-rich solar energetic particle events at 1 AU Authors: Chen, Nai-Hwa; Mason, Glenn; Innes, Davina; Bucik, Radoslav Bibcode: 2014cosp...40E.501C Altcode: The solar sources of (3) He-rich solar energetic particle events detected by ULEIS on ACE and SIT on STEREO-A, when two spacecraft were close to quadrature, are investigated in this study. We use the photospheric magnetic field with potential field source surface extrapolations and in-situ magnetic field to identify the candidate connected active regions (ARs). We also examine the activity in all nearby ARs by using SDO and STEREO EUV images and space-based radio observations on Wind and STEREO. The 3He-rich events seem to occur shortly after an increase in jet production from the connected ARs. To study the long-term evolution in the source ARs, we compare the 3He enrichment measured at ACE and STEREO seven days apart which is the time for a region to rotate from the ACE to the STEREO connection point. Title: Observations of post-flare supra-arcade fans: instabilities at the head of reconnection jets Authors: Innes, Davina; Huang, Yi-Min.; Bhattacharjee, Amitava; Guo, Lijia Bibcode: 2014cosp...40E1278I Altcode: Large eruptive flares often develop fans of hot, 10 MK, plasma above the flare arcade. Using SDO and STEREO images, we have investigated the structure of the arcade fans and in particular the formation of dark finger-like downflows, known as supra-arcade downflows (SADs). We find that certain SAD characteristics, such as forking at their heads and a tendency to start near the top of fan spikes, have close similarities to Rayleigh-Taylor fingers. 3-D resistive MHD simulations show that reconnection above the flare arcades produces a jet of low density plasma which when encountering the arcade plasma leads to instabilities at the jet head. We thus propose that SADs are the result of secondary instabilities of the Rayleigh -Taylor type at the head of reconnection jets. Title: Sdo/aia Observations of Reflecting Longitudinal Wave in Coronal Loops Authors: Kumar, Pankaj; Inhester, Bernd; Innes, Davina Bibcode: 2014cosp...40E1686K Altcode: We present high resolution observations from SDO/AIA of intensity oscillations in hot (T=8-10 MK) coronal loops. The AIA images show a large coronal loop that was rapidly heated following plasma ejection from one of the loop’s footpoints. A wave-like intensity enhancement, seen very clearly in the 131 and 94 Å channel images, propagated ahead of the ejecta along the loop, and was reflected at the opposite footpoint. The wave reflected four times before fading. It was only seen in the hot, 131 and 94 Å channels. The characteristic period and the decay time of the oscillation were about ~630 and ~440 s, respectively. The phase speed was about 460-510 km/s which roughly matches the sound speed of the loop (430-480 km/s). The observed properties of the oscillation are consistent with the observations of Dopper-shift oscillations discovered by SUMER and with their interpretation as slow magnetoacoustic waves. We suggest that the impulsive injection of plasma, following reconnection at one of the loop footpoints, led to rapid heating and the propagation of a longitudinal compressive wave along the loop. Title: A solar tornado caused by flares Authors: Panesar, N. K.; Innes, D. E.; Tiwari, S. K.; Low, B. C. Bibcode: 2014IAUS..300..235P Altcode: An enormous solar tornado was observed by SDO/AIA on 25 September 2011. It was mainly associated with a quiescent prominence with an overlying coronal cavity. We investigate the triggering mechanism of the solar tornado by using the data from two instruments: SDO/AIA and STEREO-A/EUVI, covering the Sun from two directions. The tornado appeared near to the active region NOAA 11303 that produced three flares. The flares directly influenced the prominence-cavity system. The release of free magnetic energy from the active region by flares resulted in the contraction of the active region field. The cavity, owing to its superior magnetic pressure, expanded to fill this vacated space in the corona. We propose that the tornado developed on the top of the prominence due to the expansion of the prominence-cavity system. Title: Prominence Mass Supply and the Cavity Authors: Schmit, Donald J.; Gibson, S.; Luna, M.; Karpen, J.; Innes, D. Bibcode: 2013ApJ...779..156S Altcode: 2013arXiv1311.2382S A prevalent but untested paradigm is often used to describe the prominence-cavity system: the cavity is under-dense because it is evacuated by supplying mass to the condensed prominence. The thermal non-equilibrium (TNE) model of prominence formation offers a theoretical framework to predict the thermodynamic evolution of the prominence and the surrounding corona. We examine the evidence for a prominence-cavity connection by comparing the TNE model with diagnostics of dynamic extreme ultraviolet (EUV) emission surrounding the prominence, specifically prominence horns. Horns are correlated extensions of prominence plasma and coronal plasma which appear to connect the prominence and cavity. The TNE model predicts that large-scale brightenings will occur in the Solar Dynamics Observatory Atmospheric Imaging Assembly 171 Å bandpass near the prominence that are associated with the cooling phase of condensation formation. In our simulations, variations in the magnitude of footpoint heating lead to variations in the duration, spatial scale, and temporal offset between emission enhancements in the other EUV bandpasses. While these predictions match well a subset of the horn observations, the range of variations in the observed structures is not captured by the model. We discuss the implications of our one-dimensional loop simulations for the three-dimensional time-averaged equilibrium in the prominence and the cavity. Evidence suggests that horns are likely caused by condensing prominence plasma, but the larger question of whether this process produces a density-depleted cavity requires a more tightly constrained model of heating and better knowledge of the associated magnetic structure. Title: Solar Dynamics Observatory/Atmospheric Imaging Assembly Observations of a Reflecting Longitudinal Wave in a Coronal Loop Authors: Kumar, Pankaj; Innes, D. E.; Inhester, B. Bibcode: 2013ApJ...779L...7K Altcode: 2014arXiv1409.3896K We report high resolution observations from the Solar Dynamics Observatory/Atmospheric Imaging Assembly (SDO/AIA) of intensity oscillations in a hot, T ~ 8-10 MK, loop. The AIA images show a large coronal loop that was rapidly heated following plasma ejection from one of the loop's footpoints. A wave-like intensity enhancement, seen very clearly in the 131 and 94 Å channel images, propagated ahead of the ejecta along the loop, and was reflected at the opposite footpoint. The wave reflected four times before fading. It was only seen in the hot, 131 and 94 Å channels. The characteristic period and the decay time of the oscillation were ~630 and ~440 s, respectively. The phase speed was about 460-510 km s-1 which roughly matches the sound speed of the loop (430-480 km s-1). The observed properties of the oscillation are consistent with the observations of Dopper-shift oscillations discovered by the Solar and Heliospheric Observatory/Solar Ultraviolet Measurement of Emitted Radiation and with their interpretation as slow magnetoacoustic waves. We suggest that the impulsive injection of plasma, following reconnection at one of the loop footpoints, led to rapid heating and the propagation of a longitudinal compressive wave along the loop. The wave bounces back and forth a couple of times before fading. Title: The Source Regions of Solar Energetic Particles Detected by Widely Separated Spacecraft Authors: Park, Jinhye; Innes, D. E.; Bucik, R.; Moon, Y. -J. Bibcode: 2013ApJ...779..184P Altcode: We studied the source regions of 12 solar energetic particle (SEP) events seen between 2010 August and 2012 January at STEREO-A, B, and/or Earth (Advanced Composition Explorer/Solar and Heliospheric Observatory/GOES), when the two STEREO spacecraft were separated by about 180°. All events were associated with flares (C1 to X6) and fast coronal mass ejections and, except for one, accompanied by type II radio bursts. We have determined the arrival times of the SEPs at the three positions. Extreme ultraviolet (EUV) waves, observed in the 195 Å and 193 Å channels of STEREO and the Solar Dynamics Observatory, are tracked across the Sun to determine their arrival time at the photospheric source of open field lines connecting to the spacecraft. There is a good correlation between the EUV wave arrival times at the connecting footpoints and the SEP onset times. The delay time between electron onset and the EUV wave reaching the connecting footpoint is independent of distance from the flare site. The proton delay time increases with distance from the flare site. In three of the events, secondary flare sites may have also contributed to the wide longitudinal spread of SEPs. Title: Multiwavelength Observations of an Eruptive Flare: Evidence for Blast Waves and Break-Out Authors: Kumar, Pankaj; Innes, D. E. Bibcode: 2013SoPh..288..255K Altcode: 2013arXiv1307.3720K Images of an east-limb flare on 3 November 2010 taken in the 131 Å channel of the Atmospheric Imaging Assembly onboard the Solar Dynamics Observatory provide a convincing example of a long current sheet below an erupting plasmoid, as predicted by the standard magnetic reconnection model of eruptive flares. However, the 171 Å and 193 Å channel images hint at an alternative scenario. These images reveal that large-scale waves with velocity greater than 1000 km s−1 propagated alongside and ahead of the erupting plasmoid. Just south of the plasmoid, the waves coincided with type-II radio emission, and to the north, where the waves propagated along plume-like structures, there was increased decimetric emission. Initially, the cavity around the hot plasmoid expanded. Later, when the erupting plasmoid reached the height of an overlying arcade system, the plasmoid structure changed, and the lower parts of the cavity collapsed inwards. Hot loops appeared alongside and below the erupting plasmoid. We consider a scenario in which the fast waves and the type-II emission were a consequence of a flare blast wave, and the cavity collapse and the hot loops resulted from the break-out of the flux rope through an overlying coronal arcade. Title: Flare Ribbon Energetics in the Early Phase of an SDO Flare Authors: Fletcher, L.; Hannah, I. G.; Hudson, H. S.; Innes, D. E. Bibcode: 2013ApJ...771..104F Altcode: 2014arXiv1401.6538F The sites of chromospheric excitation during solar flares are marked by extended extreme ultraviolet ribbons and hard X-ray (HXR) footpoints. The standard interpretation is that these are the result of heating and bremsstrahlung emission from non-thermal electrons precipitating from the corona. We examine this picture using multi-wavelength observations of the early phase of an M-class flare SOL2010-08-07T18:24. We aim to determine the properties of the heated plasma in the flare ribbons, and to understand the partition of the power input into radiative and conductive losses. Using GOES, SDO/EVE, SDO/AIA, and RHESSI, we measure the temperature, emission measure (EM), and differential emission measure of the flare ribbons, and deduce approximate density values. The non-thermal EM, and the collisional thick target energy input to the ribbons are obtained from RHESSI using standard methods. We deduce the existence of a substantial amount of plasma at 10 MK in the flare ribbons, during the pre-impulsive and early-impulsive phase of the flare. The average column EM of this hot component is a few times 1028 cm-5, and we can calculate that its predicted conductive losses dominate its measured radiative losses. If the power input to the hot ribbon plasma is due to collisional energy deposition by an electron beam from the corona then a low-energy cutoff of ~5 keV is necessary to balance the conductive losses, implying a very large electron energy content. Independent of the standard collisional thick-target electron beam interpretation, the observed non-thermal X-rays can be provided if one electron in 103-104 in the 10 MK (1 keV) ribbon plasma has an energy above 10 keV. We speculate that this could arise if a non-thermal tail is generated in the ribbon plasma which is being heated by other means, for example, by waves or turbulence. Title: The source regions of solar energetic particles detected by widely separated spacecraft Authors: Park, Jinhye; Innes, D.; Bucik, R.; Moon, Y. Bibcode: 2013SPD....44..126P Altcode: We studied the source regions of 12 solar energetic particle (SEP) events seen between 2010 August and 2012 January at STEREO-A, B and/or Earth (ACE/SOHO/GOES), when the two STEREO spacecraft were separated by about 180 degrees. All events were associated with flares (C1 to X6) and fast coronal mass ejections (CMEs) and, except for one, accompanied by type II radio bursts. We have determined the arrival times of the SEPs at the three positions. Extreme ultraviolet (EUV) waves, observed in the 195 and 193 angstrom channels of STEREO and SDO, are tracked across the Sun to determine their arrival time at the photospheric source of open field lines connecting to the spacecraft. There is a good correlation between the EUV wave arrival times at the connecting footpoints and the SEP onset times. The delay time between electron onset and the EUV wave reaching the connecting footpoint is independent of distance from the flare site. The proton delay time increases with distance from the flare site. In three of the events secondary flare sites may have also contributed to the wide longitudinal spread of SEPs. Title: Flare-Associated Type III Radio Bursts and Dynamics of the EUV Jet from SDO/AIA and RHESSI Observations Authors: Chen, Naihwa; Ip, Wing-Huen; Innes, Davina Bibcode: 2013ApJ...769...96C Altcode: 2013arXiv1304.2907C We present a detailed description of the interrelation between the Type III radio bursts and energetic phenomena associated with the flare activities in active region AR11158 at 07:58 UT on 2011 February 15. The timing of the Type III radio burst measured by the radio wave experiment on Wind/WAVE and an array of ground-based radio telescopes coincided with an extreme-ultraviolet (EUV) jet and hard X-ray (HXR) emission observed by SDO/AIA and RHESSI, respectively. There is clear evidence that the EUV jet shares the same source region as the HXR emission. The temperature of the jet, as determined by multiwavelength measurements by Atmospheric Imaging Assembly, suggests that Type III emission is associated with hot, 7 MK, plasma at the jet's footpoint. Title: Fast Extreme-ultraviolet Dimming Associated with a Coronal Jet Seen in Multi-wavelength and Stereoscopic Observations Authors: Lee, K. -S.; Innes, D. E.; Moon, Y. -J.; Shibata, K.; Lee, Jin-Yi; Park, Y. -D. Bibcode: 2013ApJ...766....1L Altcode: We have investigated a coronal jet observed near the limb on 2010 June 27 by the Hinode/X-Ray Telescope (XRT), EUV Imaging Spectrograph (EIS), and Solar Optical Telescope (SOT), and by the Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA), and on the disk by STEREO-A/EUVI. From EUV (AIA and EIS) and soft X-ray (XRT) images we have identified both cool and hot jets. There was a small loop eruption seen in Ca II images of the SOT before the jet eruption. We found that the hot jet preceded its associated cool jet by about 2 minutes. The cool jet showed helical-like structures during the rising period which was supported by the spectroscopic analysis of the jet's emission. The STEREO observation, which enabled us to observe the jet projected against the disk, showed dimming at 195 Å along a large loop connected to the jet. We measured a propagation speed of ~800 km s-1 for the dimming front. This is comparable to the Alfvén speed in the loop computed from a magnetic field extrapolation of the photospheric field measured five days earlier by the SDO/Helioseismic and Magnetic Imager, and the loop densities obtained from EIS Fe XIV λ264.79/274.20 line ratios. We interpret the dimming as indicating the presence of Alfvénic waves initiated by reconnection in the upper chromosphere. Title: Quiet Sun Explosive Events: Jets, Splashes, and Eruptions Authors: Innes, D. E.; Teriaca, L. Bibcode: 2013SoPh..282..453I Altcode: 2012arXiv1210.7667I Explosive events appear as broad non-Gaussian wings in the line profiles of small transition-region phenomena. Images from the Solar Dynamics Observatory (SDO) give a first view of the plasma dynamics at the sites of explosive events seen simultaneously in O VI spectra of a region of quiet Sun, taken with the ultraviolet spectrometer Solar Ultraviolet Measurements of Emitted Radiation (SUMER) onboard the Solar and Heliospheric Observatory (SOHO). Distinct event bursts were seen either at the junction of supergranular network cells or near emerging flux. Three are described in the context of their surrounding transition region (304 Å) and coronal (171 Å) activity. One showed plasma ejections from an isolated pair of sites, with a time lag of 50 seconds between events. At the site where the later explosive event was seen, the extreme ultraviolet (EUV) images show a hot core surrounded by a small, expanding ring of chromospheric emission, which we interpret as a "splash." The second explosive-event burst was related to flux cancellation, inferred from Helioseismic and Magnetic Imager (HMI) magnetograms, and a coronal dimming surrounded by a ring of bright EUV emission with explosive events at positions where the spectrometer slit crossed the bright ring. The third series of events occurred at the base of a slow, small coronal mass ejection (mini-CME). All events studied here imply jet-like flows probably triggered by magnetic reconnection at supergranular junctions. Events come from sites close to the footpoints of jets seen in Atmospheric Imaging Assembly (AIA) images, and possibly from the landing site of high-velocity flows. They are not caused by rapid rotation in spicules. Title: Pathway to the Square Kilometre Array - The German White Paper - Authors: Aharonian, F.; Arshakian, T. G.; Allen, B.; Banerjee, R.; Beck, R.; Becker, W.; Bomans, D. J.; Breitschwerdt, D.; Brüggen, M.; Brunthaler, A.; Catinella, B.; Champion, D.; Ciardi, B.; Crocker, R.; de Avillez, M. A.; Dettmar, R. J.; Engels, D.; Enßlin, T.; Enke, H.; Fieseler, T.; Gizon, L.; Hackmann, E.; Hartmann, B.; Henkel, C.; Hoeft, M.; Iapichino, L.; Innes, D.; James, C.; Jasche, J.; Jones, D.; Kagramanova, V.; Kauffmann, G.; Keane, E.; Kerp, J.; Klöckner, H. -R.; Kokkotas, K.; Kramer, M.; Krause, M.; Krause, M.; Krupp, N.; Kunz, J.; Lämmerzahl, C.; Lee, K. J.; List, M.; Liu, K.; Lobanov, A.; Mann, G.; Merloni, A.; Middelberg, E.; Niemeyer, J.; Noutsos, A.; Perlick, V.; Reich, W.; Richter, P.; Roy, A.; Saintonge, A.; Schäfer, G.; Schaffner-Bielich, J.; Schinnerer, E.; Schleicher, D.; Schneider, P.; Schwarz, D. J.; Sedrakian, A.; Sesana, A.; Smolčić, V.; Solanki, S.; Tuffs, R.; Vetter, M.; Weber, E.; Weller, J.; Wex, N.; Wucknitz, O.; Zwaan, M. Bibcode: 2013arXiv1301.4124A Altcode: The Square Kilometre Array (SKA) is the most ambitious radio telescope ever planned. With a collecting area of about a square kilometre, the SKA will be far superior in sensitivity and observing speed to all current radio facilities. The scientific capability promised by the SKA and its technological challenges provide an ideal base for interdisciplinary research, technology transfer, and collaboration between universities, research centres and industry. The SKA in the radio regime and the European Extreme Large Telescope (E-ELT) in the optical band are on the roadmap of the European Strategy Forum for Research Infrastructures (ESFRI) and have been recognised as the essential facilities for European research in astronomy. This "White Paper" outlines the German science and R&D interests in the SKA project and will provide the basis for future funding applications to secure German involvement in the Square Kilometre Array. Title: Recurring 3He-rich Solar Energetic Particle Events Authors: Bučík, R.; Innes, D. E.; Mall, U.; Korth, A.; Mason, G. M. Bibcode: 2013ICRC...33.1424B Altcode: 2013arXiv1307.6342B Using the SIT instrument aboard STEREO we have examined the abundance of the 3He during the ascending phase of solar cycle 24 from January 2010 through December 2012. We report on several cases when 3He-rich solar energetic particle events were successively observed on ACE and STEREO-A with delays consistent with the Carrington rotation rate. In the investigated period ACE and STEREO-A were significantly separated in the heliolongitude corresponding to the solar rotation times from 5 to 10 days. We inspect STEREO- A EUV images and use the potential-field source-surface extrapolations together with in-situ magnetic field data to identify responsible solar sources. We find the 3He/4He ratio highly variable in these events and correlated between the spacecraft for the cases with the same connection region on the Sun. Title: A solar tornado triggered by flares? Authors: Panesar, N. K.; Innes, D. E.; Tiwari, S. K.; Low, B. C. Bibcode: 2013A&A...549A.105P Altcode: 2012arXiv1211.6569P Context. Solar tornados are dynamical, conspicuously helical magnetic structures that are mainly observed as a prominence activity.
Aims: We investigate and propose a triggering mechanism for the solar tornado observed in a prominence cavity by SDO/AIA on September 25, 2011.
Methods: High-cadence EUV images from the SDO/AIA and the Ahead spacecraft of STEREO/EUVI are used to correlate three flares in the neighbouring active-region (NOAA 11303) and their EUV waves with the dynamical developments of the tornado. The timings of the flares and EUV waves observed on-disk in 195 Å are analysed in relation to the tornado activities observed at the limb in 171 Å.
Results: Each of the three flares and its related EUV wave occurred within ten hours of the onset of the tornado. They have an observed causal relationship with the commencement of activity in the prominence where the tornado develops. Tornado-like rotations along the side of the prominence start after the second flare. The prominence cavity expands with the accelerating tornado motion after the third flare.
Conclusions: Flares in the neighbouring active region may have affected the cavity prominence system and triggered the solar tornado. A plausible mechanism is that the active-region coronal field contracted by the "Hudson effect" through the loss of magnetic energy as flares. Subsequently, the cavity expanded by its magnetic pressure to fill the surrounding low corona. We suggest that the tornado is the dynamical response of the helical prominence field to the cavity expansion.

Movies are available in electronic form at http://www.aanda.org Title: The study on source regions of solar energetic particles detected by widely separated multiple spacecraft Authors: Park, J.; Innes, D.; Bucik, R.; Moon, Y. Bibcode: 2012AGUFMSH21A2164P Altcode: We studied the source regions of 12 solar energetic particle (SEP) events seen between 2010 August and 2012 January at STEREO-A, B and ACE, when the two stereo spacecraft were separated by about 180o. All events were associated with strong flares (C1 - X6) and fast coronal mass ejections (CMEs) accompanied by type II radio bursts. We have determined the arrival times of the SEP events at the three spacecraft. EUV waves observed in 195{Å} and 193{Å} channels of STEREO and SDO/AIA are tracked across the Sun and the arrival time of the EUV wave at the photospheric source of open field lines extending to the spacecraft connection points at 2.5 Rsun estimated. We found 7 events with flux enhancements in all spacecraft and 4 in two spacecraft. Most events came from a single source. The results show that magnetic field connections between source regions and the spacecraft play an important role in abrupt flux enhancements. In the most of them, EUV waves at the Sun are associated with a wide longitudinal spread of the SEPs. Title: Persistent Doppler Shift Oscillations Observed with Hinode/EIS in the Solar Corona: Spectroscopic Signatures of Alfvénic Waves and Recurring Upflows Authors: Tian, Hui; McIntosh, Scott W.; Wang, Tongjiang; Ofman, Leon; De Pontieu, Bart; Innes, Davina E.; Peter, Hardi Bibcode: 2012ApJ...759..144T Altcode: 2012arXiv1209.5286T Using data obtained by the EUV Imaging Spectrometer on board Hinode, we have performed a survey of obvious and persistent (without significant damping) Doppler shift oscillations in the corona. We have found mainly two types of oscillations from February to April in 2007. One type is found at loop footpoint regions, with a dominant period around 10 minutes. They are characterized by coherent behavior of all line parameters (line intensity, Doppler shift, line width, and profile asymmetry), and apparent blueshift and blueward asymmetry throughout almost the entire duration. Such oscillations are likely to be signatures of quasi-periodic upflows (small-scale jets, or coronal counterpart of type-II spicules), which may play an important role in the supply of mass and energy to the hot corona. The other type of oscillation is usually associated with the upper part of loops. They are most clearly seen in the Doppler shift of coronal lines with formation temperatures between one and two million degrees. The global wavelets of these oscillations usually peak sharply around a period in the range of three to six minutes. No obvious profile asymmetry is found and the variation of the line width is typically very small. The intensity variation is often less than 2%. These oscillations are more likely to be signatures of kink/Alfvén waves rather than flows. In a few cases, there seems to be a π/2 phase shift between the intensity and Doppler shift oscillations, which may suggest the presence of slow-mode standing waves according to wave theories. However, we demonstrate that such a phase shift could also be produced by loops moving into and out of a spatial pixel as a result of Alfvénic oscillations. In this scenario, the intensity oscillations associated with Alfvénic waves are caused by loop displacement rather than density change. These coronal waves may be used to investigate properties of the coronal plasma and magnetic field. Title: LEMUR: Large European module for solar Ultraviolet Research. European contribution to JAXA's Solar-C mission Authors: Teriaca, Luca; Andretta, Vincenzo; Auchère, Frédéric; Brown, Charles M.; Buchlin, Eric; Cauzzi, Gianna; Culhane, J. Len; Curdt, Werner; Davila, Joseph M.; Del Zanna, Giulio; Doschek, George A.; Fineschi, Silvano; Fludra, Andrzej; Gallagher, Peter T.; Green, Lucie; Harra, Louise K.; Imada, Shinsuke; Innes, Davina; Kliem, Bernhard; Korendyke, Clarence; Mariska, John T.; Martínez-Pillet, Valentin; Parenti, Susanna; Patsourakos, Spiros; Peter, Hardi; Poletto, Luca; Rutten, Robert J.; Schühle, Udo; Siemer, Martin; Shimizu, Toshifumi; Socas-Navarro, Hector; Solanki, Sami K.; Spadaro, Daniele; Trujillo-Bueno, Javier; Tsuneta, Saku; Dominguez, Santiago Vargas; Vial, Jean-Claude; Walsh, Robert; Warren, Harry P.; Wiegelmann, Thomas; Winter, Berend; Young, Peter Bibcode: 2012ExA....34..273T Altcode: 2011ExA...tmp..135T; 2011arXiv1109.4301T The solar outer atmosphere is an extremely dynamic environment characterized by the continuous interplay between the plasma and the magnetic field that generates and permeates it. Such interactions play a fundamental role in hugely diverse astrophysical systems, but occur at scales that cannot be studied outside the solar system. Understanding this complex system requires concerted, simultaneous solar observations from the visible to the vacuum ultraviolet (VUV) and soft X-rays, at high spatial resolution (between 0.1'' and 0.3''), at high temporal resolution (on the order of 10 s, i.e., the time scale of chromospheric dynamics), with a wide temperature coverage (0.01 MK to 20 MK, from the chromosphere to the flaring corona), and the capability of measuring magnetic fields through spectropolarimetry at visible and near-infrared wavelengths. Simultaneous spectroscopic measurements sampling the entire temperature range are particularly important. These requirements are fulfilled by the Japanese Solar-C mission (Plan B), composed of a spacecraft in a geosynchronous orbit with a payload providing a significant improvement of imaging and spectropolarimetric capabilities in the UV, visible, and near-infrared with respect to what is available today and foreseen in the near future. The Large European Module for solar Ultraviolet Research (LEMUR), described in this paper, is a large VUV telescope feeding a scientific payload of high-resolution imaging spectrographs and cameras. LEMUR consists of two major components: a VUV solar telescope with a 30 cm diameter mirror and a focal length of 3.6 m, and a focal-plane package composed of VUV spectrometers covering six carefully chosen wavelength ranges between 170 Å and 1270 Å. The LEMUR slit covers 280'' on the Sun with 0.14'' per pixel sampling. In addition, LEMUR is capable of measuring mass flows velocities (line shifts) down to 2 km s - 1 or better. LEMUR has been proposed to ESA as the European contribution to the Solar C mission. Title: Flare Ribbons In The Early Phase Of An SDO Flare: Emission Measure And Energetics Authors: Fletcher, Lyndsay; Hannah, I. G.; Hudson, H. S.; Innes, D. E. Bibcode: 2012AAS...22050902F Altcode: We report on the M1.0 flare of 7th August 2010, which displayed extended early phase chromospheric ribbons, well observed by SDO/AIA and RHESSI. Most large flares saturate rapidly in the high-temperature AIA channels, however this event could be followed in unsaturated AIA images for ten minutes in the build-up to and first few minutes of the impulsive phase. Analysis of GOES, RHESSI and SDO/AIA demonstrates the presence of high temperature ( 10MK), compact plasma volumes in the chromospheric flare ribbons, with a column emission measure of on average 3-7 x 1028 cm-5. We construct a time-resolved energy budget for the ribbon plasma, including also SDO/EVE data, and discuss the implications of the observed ribbon properties for flare energisation.

This work was supported by the UK’s Science and Technology Facilities Council (ST/1001801), and by the European Commission through the FP7 HESPE project (FP7-2010-SPACE-263086). Title: Fast EUV Dimming Associated with a Coronal Jet Seen in Multi-Wavelength and Stereoscopic Observations Authors: Lee, Kyoung-Sun; Innes, D. E.; Moon, Y.; Shibata, K.; Lee, J. Bibcode: 2012AAS...22020120L Altcode: We have investigated a coronal jet observed near the limb on 2010 June 27 by the Hinode/X-Ray Telescope (XRT), EUV Imaging Spectrograph (EIS), and Solar Optical Telescope (SOT), and the SDO/Atmospheric Imaging Assembly (AIA), Helioseismic and Magnetic Imager (HMI), and on the disk by STEREO-A/EUVI. From EUV (AIA and EIS) and soft X-ray (XRT) images we have identified both cool and hot jets. There was a small loop eruption in Ca II images of the SOT before the jet eruption. We found that the hot jet preceded its associated cool jet by about 2 minutes. The cool jet showed helical-like structures during the rising period. According to the spectroscopic analysis, the jet’s emission changed from blue to red shift with time, implying helical motions in the jet. The STEREO observation, which enabled us to observe the jet projected against the disk, showed that there was a dim loop associated with the jet. We measured a propagation speed of ∼ 800 km s-1 for the dimming front. This is comparable to the Alfven speed in the loop computed from a magnetic field extrapolation of the HMI photospheric field measured 5 days earlier and the loop densities obtained from EIS Fe XIV λ 264.79/274.20 line ratios. We interpret the dimming as indicating the presence of Alfvenic waves initiated by reconnection in the upper chromosphere. Title: Break up of returning plasma after the 7 June 2011 filament eruption by Rayleigh-Taylor instabilities Authors: Innes, D. E.; Cameron, R. H.; Fletcher, L.; Inhester, B.; Solanki, S. K. Bibcode: 2012A&A...540L..10I Altcode: 2012arXiv1202.4981I Context. A prominence eruption on 7 June 2011 produced spectacular curtains of plasma falling through the lower corona. At the solar surface they created an incredible display of extreme ultraviolet brightenings.
Aims: To identify and analyze some of the local instabilities which produce structure in the falling plasma.
Methods: The structures were investigated using SDO/AIA 171 Å and 193 Å images in which the falling plasma appeared dark against the bright coronal emission.
Results: Several instances of the Rayleigh-Taylor instability were investigated. In two cases the Alfvén velocity associated with the dense plasma could be estimated from the separation of the Rayleigh-Taylor fingers. A second type of feature, which has the appearance of self-similar branching horns was discussed.

Appendix A and two movies are available in electronic form at http://www.aanda.org Title: Solar Particle Acceleration Radiation and Kinetics (SPARK). A mission to understand the nature of particle acceleration Authors: Matthews, Sarah A.; Williams, David R.; Klein, Karl-Ludwig; Kontar, Eduard P.; Smith, David M.; Lagg, Andreas; Krucker, Sam; Hurford, Gordon J.; Vilmer, Nicole; MacKinnon, Alexander L.; Zharkova, Valentina V.; Fletcher, Lyndsay; Hannah, Iain G.; Browning, Philippa K.; Innes, Davina E.; Trottet, Gerard; Foullon, Clare; Nakariakov, Valery M.; Green, Lucie M.; Lamoureux, Herve; Forsyth, Colin; Walton, David M.; Mathioudakis, Mihalis; Gandorfer, Achim; Martinez-Pillet, Valentin; Limousin, Olivier; Verwichte, Erwin; Dalla, Silvia; Mann, Gottfried; Aurass, Henri; Neukirch, Thomas Bibcode: 2012ExA....33..237M Altcode: 2011ExA...tmp..124M Energetic particles are critical components of plasma populations found throughout the universe. In many cases particles are accelerated to relativistic energies and represent a substantial fraction of the total energy of the system, thus requiring extremely efficient acceleration processes. The production of accelerated particles also appears coupled to magnetic field evolution in astrophysical plasmas through the turbulent magnetic fields produced by diffusive shock acceleration. Particle acceleration is thus a key component in helping to understand the origin and evolution of magnetic structures in, e.g. galaxies. The proximity of the Sun and the range of high-resolution diagnostics available within the solar atmosphere offers unique opportunities to study the processes involved in particle acceleration through the use of a combination of remote sensing observations of the radiative signatures of accelerated particles, and of their plasma and magnetic environment. The SPARK concept targets the broad range of energy, spatial and temporal scales over which particle acceleration occurs in the solar atmosphere, in order to determine how and where energetic particles are accelerated. SPARK combines highly complementary imaging and spectroscopic observations of radiation from energetic electrons, protons and ions set in their plasma and magnetic context. The payload comprises focusing-optics X-ray imaging covering the range from 1 to 60 keV; indirect HXR imaging and spectroscopy from 5 to 200 keV, γ-ray spectroscopic imaging with high-resolution LaBr3 scintillators, and photometry and source localisation at far-infrared wavelengths. The plasma environment of the regions of acceleration and interaction will be probed using soft X-ray imaging of the corona and vector magnetography of the photosphere and chromosphere. SPARK is designed for solar research. However, in addition it will be able to provide exciting new insights into the origin of particle acceleration in other regimes, including terrestrial gamma-ray flashes (TGF), the origin of γ-ray bursts, and the possible existence of axions. Title: An Automatic Detection Method for Extreme-ultraviolet Dimmings Associated with Small-scale Eruption Authors: Alipour, N.; Safari, H.; Innes, D. E. Bibcode: 2012ApJ...746...12A Altcode: 2011arXiv1112.4679A Small-scale extreme-ultraviolet (EUV) dimming often surrounds sites of energy release in the quiet Sun. This paper describes a method for the automatic detection of these small-scale EUV dimmings using a feature-based classifier. The method is demonstrated using sequences of 171 Å images taken by the STEREO/Extreme UltraViolet Imager (EUVI) on 2007 June 13 and by Solar Dynamics Observatory/Atmospheric Imaging Assembly on 2010 August 27. The feature identification relies on recognizing structure in sequences of space-time 171 Å images using the Zernike moments of the images. The Zernike moments space-time slices with events and non-events are distinctive enough to be separated using a support vector machine (SVM) classifier. The SVM is trained using 150 events and 700 non-event space-time slices. We find a total of 1217 events in the EUVI images and 2064 events in the AIA images on the days studied. Most of the events are found between latitudes -35° and +35°. The sizes and expansion speeds of central dimming regions are extracted using a region grow algorithm. The histograms of the sizes in both EUVI and AIA follow a steep power law with slope of about -5. The AIA slope extends to smaller sizes before turning over. The mean velocity of 1325 dimming regions seen by AIA is found to be about 14 km s-1. Title: Multi-wavelength and Stereoscopic observations of a coronal jet supporting the emerging flux reconnection model Authors: Lee, K.; Innes, D.; Moon, Y.; Shibata, K. Bibcode: 2011AGUFMSH13B1940L Altcode: We have investigated a coronal jet near the limb on 2010 June 27 by Hinode/X-Ray Telescope (XRT), EUV Imaging Spectrograph (EIS), Solar Optical Telescope (SOT), SDO/Atmospheric Imaging Assembly (AIA), and STEREO. From EUV (AIA and EIS) and soft X-ray (XRT) images we identify the erupting jet feature in cool and hot temperatures. It is noted that there was a small loop eruption at the low temperature from the SOT observation before the jet eruption. Using the high temporal and multi wavelength AIA images, we found that the hot jet preceded its associated cool jet. The jet also shows the helical-like structures during the rising period. According to the spectroscopic analysis, the jet structure changes from blue shift to red one with time, implying the helical structure of the jet. The STEREO observation, which enables us to observe this jet on the disk, shows that there was a dim loop associated with the jet. Comparing observations from the AIA and STEREO, the dim loop corresponds to the jet structure which implies the heated loop. Considering that the structure of its associated active region seen in STEREO is similar to that in AIA observed 5 days before, we compared the jet morphology on the limb with the magnetic fields extrapolated from a HMI vector magnetogram observed on the disk. Interestingly, the comparison also shows that the open field corresponds to the jet which is seen as the dim loop in STEREO. Our observations (XRT, SDO, SOT, and STEREO) are well consistent with the numerical simulation of the emerging flux reconnection model predicted. Title: EUV jets, type III radio bursts and sunspot waves investigated using SDO/AIA observations Authors: Innes, D. E.; Cameron, R. H.; Solanki, S. K. Bibcode: 2011A&A...531L..13I Altcode: 2011arXiv1106.3417I Context. Quasi-periodic plasma jets are often ejected from the Sun into interplanetary space. The commonly observed signatures are day-long sequences of type III radio bursts.
Aims: The aim is to identify the source of quasi-periodic jets observed on 3 Aug. 2010 in the Sun's corona and in interplanetary space.
Methods: Images from the Solar Dynamics Observatory (SDO) at 211 Å are used to identify the solar source of the type III radio bursts seen in WIND/WAVES dynamic spectra. We analyse a 2.5 h period during which six strong bursts are seen. The radio signals are cross-correlated with emission from extreme ultraviolet (EUV) jets coming from the western side of a sunspot in AR 11092. The jets are further cross-correlated with brightening at a small site on the edge of the sunspot umbra, and the brightening with 3-min sunspot intensity oscillations.
Results: The radio bursts correlate very well with the EUV jets. The EUV jet emission also correlates well with brightening at what looks like their footpoint at the edge of the umbra. The jet emission lags the radio signals and the footpoint brightening by about 30 s because the EUV jets take time to develop. For 10-15 min after strong EUV jets are ejected, the footpoint brightens at roughly 3 min intervals. In both the EUV images and the extracted light curves, it looks as though the brightening is related to the 3-min sunspot oscillations, although the correlation coefficient is rather low. The only open field near the jets is rooted in the sunspot.
Conclusions: Active region EUV/X-ray jets and interplanetary electron streams originate on the edge of the sunspot umbra. They form along a current sheet between the sunspot open field and closed field connecting to underlying satellite flux. Sunspot running penumbral waves cause roughly 3-min jet footpoint brightening. The relationship between the waves and jets is less clear.

Movie is available in electronic form at http://www.aanda.org Title: Evolution of microflares associated with bright points in coronal holes and in quiet regions Authors: Kamio, S.; Curdt, W.; Teriaca, L.; Innes, D. E. Bibcode: 2011A&A...529A..21K Altcode: 2010arXiv1009.1957K
Aims: We aim to find similarities and differences between microflares at coronal bright points found in quiet regions and coronal holes, and to study their relationship with large scale flares.
Methods: Coronal bright points in quiet regions and in coronal holes were observed with Hinode/EIS using the same sequence. Microflares associated with bright points are identified from the X-ray lightcurve. The temporal variation of physical properties was traced in the course of microflares.
Results: The lightcurves of microflares indicated an impulsive peak at hot emission followed by an enhancement at cool emission, which is compatible with the cooling model of flare loops. The density was found to increase at the rise of the impulsive peak, supporting chromospheric evaporation models. A notable difference is found in the surroundings of microflares; diffuse coronal jets are produced above microflares in coronal holes while coronal dimmings are formed in quiet regions.
Conclusions: The microflares associated with bright points share common characteristics to active region flares. The difference in the surroundings of microflares are caused by open and closed configurations of the pre-existing magnetic field. Title: Multi-wavelength Observation Of A Coronal Jet Supporting The Emerging Flux Reconnection Model Authors: Lee, Kyoung-Sun; Innes, D.; Moon, Y.; Shibata, K. Bibcode: 2011SPD....42.2109L Altcode: 2011BAAS..43S.2109L We have investigated a coronal jet near the limb on 2010 June 27 by Hinode/X-Ray Telescope (XRT), EUV Imaging Spectrograph (EIS), SDO/Atmospheric Imaging Assembly (AIA), and STEREO. From EUV (AIA and EIS) and soft X-ray (XRT) images we identify the erupting jet feature in cool and hot temperatures. Using the high temporal and multi wavelength AIA images, we found that the hot jet preceded its associated cool jet and their structures are well consistent with the numerical simulation of the emerging flux-reconnection model. From the spectroscopic analysis, we found that the jet structure changes from blue shift to red one with time, which may indicate the helical structure of the jet. The STEREO observation, which enables us to observe this jet on the disk, shows that there was a dim loop associated with the jet. Considering that the structure of its associated active region seen in STEREO is similar to that in AIA observed 5 days before, we compared the jet morphology on the limb with the magnetic fields extrapolated from a HMI vector magnetogram observed on the disk. Interestingly, the comparison shows that the open and closed magnetic fields correspond to the jet and the dim loop, respectively, as the emerging flux reconnection model predicted. Title: Oscillations in the wake of a flare blast wave Authors: Tothova, D.; Innes, D. E.; Stenborg, G. Bibcode: 2011A&A...528L..12T Altcode: 2011arXiv1102.3124T Context. Oscillations of coronal loops in the Sun have been reported in both imaging and spectral observations at the onset of flares. Images reveal transverse oscillations, whereas spectra detect line-of-sight velocity or Doppler-shift oscillations. The Doppler-shift oscillations are commonly interpreted as longitudinal modes.
Aims: Our aim is to investigate the relationship between loop dynamics and flows seen in TRACE 195 Å images and Doppler shifts observed by SUMER in Si iii 1113.2 Å and FeXIX 1118.1 Å at the time of a C.8-class limb flare and an associated CME.
Methods: We carefully co-aligned the sequence of TRACE 195 Å images to structures seen in the SUMER Si iii, CaX, and FeXIX emission lines. Additionally, Hα observations of a lifting prominence associated with the flare and the coronal mass ejection (CME) are available in three bands around 6563.3 Å. They give constraints on the timing and geometry.
Results: Large-scale Doppler-shift oscillations in FeXIX and transverse oscillations in intensity images were observed over a large region of the corona after the passage of a wide bright extreme-ultraviolet (EUV) disturbance, which suggests ionization, heating, and acceleration of hot plasma in the wake of a blast wave.

The online movie associated to Fig. 2 is available at http://www.aanda.org and at http://www.mps.mpg.de/data/outgoing/tothova/movie.gif Title: The source regions of SEPs observed by SDO in Aug 2010 Authors: Innes, Davina; Park, Jinhye; Bucik, Radoslav Bibcode: 2011EGUGA..1311481I Altcode: The source regions of Solar Energetic Particle events observed in Aug 2010 are investigated using EUV images obtained by the Solar Dynamics Observatory and the two STEREO telescopes. The high cadence SDO observations allow a detailed analysis of flows around the sites of energy release and the STEREO spacecraft give complimentary, almost 90 degree, views of the eruption sites. For each event, we show the sites of flaring and filament eruptions in relation to the large-scale magnetic field obtained from potential field extrapolations of the photospheric fields and the evolving smaller scale magnetic fields. We determine the speeds of eruptions and waves close to the Sun and identify them with coronagraph CME observations. The fluxes, energy dispersions, and abundances of energetic particles are measured by ACE, STEREO-A and STEREO-B. Title: STEREO quadrature observations of coronal dimming at the onset of mini-CMEs Authors: Innes, D. E.; McIntosh, S. W.; Pietarila, A. Bibcode: 2010A&A...517L...7I Altcode: 2010arXiv1005.2097I Context. Using unique quadrature observations with the two STEREO spacecraft, we investigate coronal dimmings at the onset of small-scale eruptions. In CMEs they are believed to indicate the opening up of the coronal magnetic fields at the start of the eruption.
Aims: It is to determine whether coronal dimming seen in small-scale eruptions starts before or after chromospheric plasma ejection.
Methods: One STEREO spacecraft obtained high cadence, 75 s, images in the He II 304 Å channel, and the other simultaneous images in the Fe IX/Fe X 171 Å channel. We concentrate on two well-positioned chromospheric eruptions that occurred at disk center in the 171 Å images, and on the limb in 304 Å. One was in the quiet Sun and the other was in an equatorial coronal hole. We compare the timing of chromospheric eruption seen in the 304 Å limb images with the brightenings and dimmings seen on disk in the 171 Å images. Further we use off-limb images of the low frequency 171 Å power to infer the coronal structure near the eruptions.
Results: In both the quiet Sun and the coronal hole eruption, on disk 171 Å dimming was seen before the chromospheric eruption, and in both cases it extends beyond the site of the chromospheric eruption. The quiet Sun eruption occurred on the outer edge of the enclosing magnetic field of a prominence and may be related to a small disruption of the prominence just before the 171 Å dimming.
Conclusions: These small-scale chromospheric eruptions started with a dimming in coronal emission just like their larger counterparts. We therefore suggest that a fundamental step in triggering them was the removal of overlying coronal field.

Movies are only available in electronic form at http://www.aanda.org Title: STEREO observations of quasi-periodically driven high velocity outflows in polar plumes Authors: McIntosh, S. W.; Innes, D. E.; de Pontieu, B.; Leamon, R. J. Bibcode: 2010A&A...510L...2M Altcode: 2010arXiv1001.3377M Context. Plumes are one of the most ubiquitous features seen at the limb in polar coronal holes and are considered to be a source of high density plasma streams to the fast solar wind.
Aims: We analyze STEREO observations of plumes and aim to reinterpret and place observations with previous generations of EUV imagers within a new context that was recently developed from Hinode observations.
Methods: We exploit the higher signal-to-noise, spatial and temporal resolution of the EUVI telescopes over that of SOHO/EIT to study the temporal variation of polar plumes in high detail. We employ recently developed insight from imaging (and spectral) diagnostics of active region, plage, and quiet Sun plasmas to identify the presence of apparent motions as high-speed upflows in magnetic regions as opposed to previous interpretations of propagating waves.
Results: In almost all polar plumes observed at the limb in these STEREO sequences, in all coronal passbands, we observe high speed jets of plasma traveling along the structures with a mean velocity of 135 km s-1 at a range of temperatures from 0.5-1.5 MK. The jets have an apparent brightness enhancement of ~5% above that of the plumes they travel on and repeat quasi-periodically, with repeat-times ranging from five to twenty-five minutes. We also notice a very weak, fine scale, rapidly evolving, but ubiquitous companion of the plumes that covers the entire coronal hole limb.
Conclusions: The observed jets are remarkably similar in intensity enhancement, periodicity and velocity to those observed in other magnetic regions of the solar atmosphere. They are multi-thermal in nature. We infer that the jets observed on the plumes are a source of heated mass to the fast solar wind. Further, based on the previous results that motivated this study, we suggest that these jets originated in the upper chromosphere.

Five movies are only available in electronic form at http://www.aanda.org Title: STEREO quadrature observations of mass flows in prominences Authors: Innes, Davina; McIntosh, Scott; Pietarila, Anna Bibcode: 2010cosp...38.2917I Altcode: 2010cosp.meet.2917I Understanding the structure and dynamics of prominences is much easier when both the promi-nence on the limb and the filament on the disk are seen together. In February 2009, we obtained STEREO quadrature observations with a cadence of 75 s and simultaneous images of promi-nences in 304 A at the limb, and 171 A at disk center. We show how the observed flows in the prominence are associated with microflares seen in 171 at disk center for a couple of representative cases. Title: Impusive heating of bright points observed by EIS and SUMER Authors: Kamio, Suguru; Curdt, Werner; Teriaca, Luca; Innes, Davina Bibcode: 2010cosp...38.2838K Altcode: 2010cosp.meet.2838K We studied the temporal variation of bright points (BPs) in the quiet region and in the coronal hole. Time series of X-ray images show significant emission increases in BPs with durations shorter than 10 min. Since these impulsive brightenings are frequently found all over the Sun, study of their mechanism is important for understanding the dynamics in the quiescent corona. Characteristics of light curves of BPs in the transition region and in the corona are similar to those of solar flares, though at a much smaller scale. Fast raster scans with SOHO/SUMER and Hinode/EIS allowed us to obtain light curves in multiple emission lines. At the peak of X-ray flux, a significant emission in Fe XV (2MK), which is normally very weak in BPs, is detected. In addition, diagnostic using the Fe XII line pair indicate density increase in BPs. These results suggest that impulsive heating takes place in the corona, which causes chromospheric evaporation supplying hot plasma into coronal loops. After the X-ray peak, delayed emission increase in He II and O IV is observed, which is interpreted as the cooling of hot plasma. We will discuss the relationship between these small scale flares and jets. Title: STEREO quadrature observations of coronal dimming at the onset of mini-CMEs Authors: Innes, Davina; McIntosh, Scott Bibcode: 2010cosp...38.1821I Altcode: 2010cosp.meet.1821I We study small solar eruptions using observations from the STEREO spacecraft in quadrature. One spacecraft obtained images through the 171 A filter and the other simultaneously through the 304 A filter, with a cadence 75 s. By co-aligning the disk center 171 A images with the limb 304 A images, we investigate the temporal and spatial relationship for the emissions at the different wavelengths from the different perspectives. We concentrate on two small eruptions: one in a coronal hole and one in the quiet Sun. In each case dimming in the 171 A filter precedes and surrounds brightening at 171 A and the chromospheric eruption. Similar coronal dimmings are often associated with the onset of large CMEs just before and simultaneous with flares and/or filament eruptions. The observations reinforce the idea of a single, scale-free process for solar eruption. Title: Soft X-ray Emission in the Quiet Sun Related to Magnetic Reconnection Authors: Attie, Raphael; Innes, Davina; Potts, Hugh Bibcode: 2010cosp...38.1957A Altcode: 2010cosp.meet.1957A The X-ray telescope on Hinode is discovering small, intense X-ray brightenings throughout the quiet Sun, on the scale of a few Mm. The driving mechanism is thought to be magnetic reconnection. With the high spatial and temporal resolution of the Hinode instruments it is now possible to test the hypothesis. We analyze a 4-hour time series of Hinode/XRT images, taken simultaneously with Hinode/SOT Na I Stokes V/I and blue continuum images. The photospheric horizontal flows are derived from the granulation seen in the blue continuum. The dynamic of the longitudinal magnetic eld at several supergranulation junctions is analyzed and compared with the number and form of their associated X-ray brightenings. Quiet Sun bright X-ray emission originates predominately at supergranular junctions where the flow is the most converging and twisted. The transients are related to the cancellation of magnetic ux at these specific sites, most probably caused by magnetic reconnection. Convergence and twist appear as two necessary-and-non-sufficient conditions for the occurrence of these processes. Title: Quiet Sun mini-coronal mass ejections activated by supergranular flows Authors: Innes, D. E.; Genetelli, A.; Attie, R.; Potts, H. E. Bibcode: 2009A&A...495..319I Altcode: 2008arXiv0811.2744I Context: The atmosphere of the quiet Sun is controlled by photospheric flows sweeping up concentrations of mixed polarity magnetic field. Along supergranule boundaries and junctions, there is a strong correlation between magnetic flux and bright chromospheric and transition region emission.
Aims: The aim is to investigate the relationship between photospheric flows and small flare-like brightenings seen in Extreme Ultraviolet images.
Methods: We describe observations of small eruptions seen in quiet Sun images taken with the Extreme UltraViolet Imager (EUVI) on STEREO. The photospheric flows during the eruption build-up phase are investigated by tracking granules in high resolution MDI continuum images.
Results: Eruptions with characteristics of small coronal mass ejections (CMEs) occur at the junctions of supergranular cells. The eruptions produce brightening at the onset site, dark cloud or small filament ejections, and faint waves moving with plane-of-sky speeds up to 100 km s-1. In the two examples studied, they appear to be activated by converging and rotating supergranular flows, twisting small concentrations of opposite polarity magnetic field. An estimate of the occurrence rate is about 1400 events per day over the whole Sun. One third of these events seem to be associated with waves. Typically, the waves last for about 30 min and travel a distance of 80 Mm, so at any one time they cover 1/50th of the lower corona.

Movies are only available in electronic form at http://www.aanda.org Title: Evidence of photospheric vortex flows at supergranular junctions observed by FG/SOT (Hinode) Authors: Attie, R.; Innes, D. E.; Potts, H. E. Bibcode: 2009A&A...493L..13A Altcode: 2008arXiv0811.3445A Context: Twisting motions of different sorts are observed in several layers of the solar atmosphere. Chromospheric sunspot whorls and rotation of sunspots or even higher up in the lower corona sigmoids are examples of the large-scale twisted topology of many solar features. Nevertheless, their occurrence on a large scale in the quiet photosphere has not been investigated yet.
Aims: The present study reveals the existence of vortex flows located at the supergranular junctions of the quiet Sun.
Methods: We used a 1-h and a 5-h time series of the granulation in blue continuum and G-band images from FG/SOT to derive the photospheric flows. A feature-tracking technique called balltracking was performed to track the granules and reveal the underlying flow fields.
Results: In both time series, we identify long lasting vortex flow located at supergranular junctions. The first vortex flow lasts at least 1 h and is ~20´´ wide (~15.5 Mm). The second vortex flow lasts more than 2 h and is ~27´´ wide (~21 Mm). Title: A nanoflare model for active region radiance: application of artificial neural networks Authors: Bazarghan, M.; Safari, H.; Innes, D. E.; Karami, E.; Solanki, S. K. Bibcode: 2008A&A...492L..13B Altcode: 2008arXiv0808.3925B Context: Nanoflares are small impulsive bursts of energy that blend with and possibly make up much of the solar background emission. Determining their frequency and energy input is central to understanding the heating of the solar corona. One method is to extrapolate the energy frequency distribution of larger individually observed flares to lower energies. Only if the power law exponent is greater than 2 is it considered possible that nanoflares contribute significantly to the energy input.
Aims: Time sequences of ultraviolet line radiances observed in the corona of an active region are modelled with the aim of determining the power law exponent of the nanoflare energy distribution.
Methods: A simple nanoflare model based on three key parameters (the flare rate, the flare duration, and the power law exponent of the flare energy frequency distribution) is used to simulate emission line radiances from the ions Fe XIX, Ca XIII, and Si III, observed by SUMER in the corona of an active region as it rotates around the east limb of the Sun. Light curve pattern recognition by an Artificial Neural Network (ANN) scheme is used to determine the values.
Results: The power law exponents, α≈2.8, 2.8, and 2.6 are obtained for Fe XIX, Ca XIII, and Si III respectively.
Conclusions: The light curve simulations imply a power law exponent greater than the critical value of 2 for all ion species. This implies that if the energy of flare-like events is extrapolated to low energies, nanoflares could provide a significant contribution to the heating of active region coronae. Title: EIS/ Hinode Observations of Doppler Flow Seen through the 40-Arcsec Wide-Slit Authors: Innes, D. E.; Attie, R.; Hara, H.; Madjarska, M. S. Bibcode: 2008SoPh..252..283I Altcode: 2008SoPh..tmp..174I; 2008arXiv0807.1185I The Extreme ultraviolet Imaging Spectrometer (EIS) onboard Hinode is the first solar telescope to obtain wide-slit spectral images that can be used for detecting Doppler flows in transition region and coronal lines on the Sun and to relate them to their surrounding small-scale dynamics. We select EIS lines covering the temperature range 6×104 to 2×106 K that give spectrally pure images of the Sun with the 40-arcsec slit. In these images Doppler shifts are seen as horizontal brightenings. Inside the image it is difficult to distinguish shifts from horizontal structures but emission beyond the image edge can be unambiguously identified as a line shift in several lines separated from others on their blue or red side by more than the width of the spectrometer slit (40 pixels). In the blue wing of He II, we find a large number of events with properties (size and lifetime) similar to the well-studied explosive events seen in the ultraviolet spectral range. Comparison with X-Ray Telescope (XRT) images shows many Doppler shift events at the footpoints of small X-ray loops. The most spectacular event observed showed a strong blue shift in the transition region and lower corona lines from a small X-ray spot that lasted less than 7 min. The emission appears to be near a cool coronal loop connecting an X-ray bright point to an adjacent region of quiet Sun. The width of the emission implies a line-of-sight velocity of 220 km s−1. In addition, we show an example of an Fe XV shift with a velocity of about 120 km s−1, coming from what looks like a narrow loop leg connecting a small X-ray brightening to a larger region of X-ray emission. Title: Explosive Event in the Quiet Sun Seen by XRT-EIS and SUMER Authors: Attie, R.; Innes, D. Bibcode: 2008ASPC..397..155A Altcode: On 10th April 2007, XRT-EIS/Hinode and SUMER/Soho were coaligned on the same region of the quiet Sun. Here we present an empirical description of an X-ray brightening observed with these instruments. Different layers were observed using transition region and coronal lines : N V (1238 Å), O V (629 Å) and Mg X (624 Å) with SUMER, in soft x-ray with XRT through its Al-mesh filter, and in He II (256 Å), Fe XII (195 Å) and Fe XV (284 Å) with EIS through its 40 arcsec wide slit. Title: SUMER-Hinode Observations of Microflares: Excitation of Molecular Hydrogen Authors: Innes, D. E. Bibcode: 2008ASPC..397..174I Altcode: Observations of active region plage with SUMER and Hinode have detected small concentrations of H_2 near the footpoints of X-ray microflares. The H_2 is excited by the O VI line at 1031.94 Å which, although not observed, must be brightening along with the observed transition region line (Si III 1113.24 Å). About one third of the strong transition region brightenings in the plage excited observable H_2 emission. Each of the H_2 events occur at a footpoint of a brightening X-ray loop. It is suggested that microflare energy dissipation in the loop footpoint heats and reduces the opacity of the chromosphere, so that O VI microflare emission is able to excite the H_2. Title: High Speed Plasma Acceleration and Loop Oscillations at Flare Onset Authors: Tothova, D.; Innes, D. Bibcode: 2008ESPM...122.101T Altcode: We analyse the postflare loop dynamics of events observed at the limb during the SUMER Flare Watch campaigns in 2000 and 2002. Observations of high blue and red Doppler shifts (up to 700 km/s in the line-of-sight) and large Doppler broadening have been made with the SUMER spectrometer in the emission lines Si III 1113.22 Å (0.1 MK), Ca X 557.8 Å (1 MK), and mainly in the flare lines Fe XIX 1118.1 Å (10 MK) and Fe XXI 1354 Å (12 MK). Some of the events have been simultaneously observed with the Transition Region and Coronal Explorer (TRACE) in the 195 Å passband and with the Nancay radioheliograph at 327 MHz. We propose that the recorded high Doppler shifts spreading over the large portion of the spectrometer slit sometimes followed by the emission at 327 MHz high up in the corona, are a signature of high speed plasma acceleration and loop oscillation in the wake of a propagating large scale wave. Title: Quiet Sun Mini-CMEs Observed in STEREO Authors: Innes, D.; Genetelli, A.; Attie, R.; Potts, H. Bibcode: 2008ESPM...12.2.86I Altcode: Mini-CMEs are eruptions of cool chromospheric material into the corona seen up to 50 Mm from the source. They are usually accompanied by flare-like brightenings at the onset site. The velocities are typically 20-30 km/s, but may be 5 times faster at onset.

STEREO 171 A observations of a region around a small equatorial coronal hole when it was crossing the disk center are studied over a period of 24 hours. Many events are seen. Events are generally characterized by dark clouds in the 171 images and strong brightening in the chromosphere. Selected events will be discussed with emphasis on the underlying photospheric magnetic field and photospheric flows. Title: SOHO/SUMER observations of prominence oscillation before eruption Authors: Chen, P. F.; Innes, D. E.; Solanki, S. K. Bibcode: 2008A&A...484..487C Altcode: 2008arXiv0802.1961C Context: Coronal mass ejections (CMEs), as a large-scale eruptive phenomenon, often reveal some precursors in the initiation phase, e.g., X-ray brightening, filament darkening, etc., which are useful for CME modelling and space weather forecasting.
Aims: With the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectroscopic observations of the 2000 September 26 CME, we propose another precursor for CMEs, namely, long-time prominence oscillations.
Methods: We observed the prominence oscillation-and-eruption event by ground-based Hα telescopes and space-borne white-light, EUV imaging, and spectroscopic instruments. In particular, the SUMER slit was observing the prominence in a sit-and-stare mode.
Results: The observations indicate that a siphon flow was moving from the proximity of the prominence to a site at a projected distance of 270'', which was followed by repetitive Hα surges and continual prominence oscillations. The oscillation lasted 4 hours before the prominence erupted as a blob-like CME. The analysis of the multiwavelength data indicates that the whole series of processes fits well into the emerging flux trigger mechanism for CMEs. In this mechanism, emerging magnetic flux drives a siphon flow due to increased gas pressure where the background polarity emerges. It also drives Hα surges through magnetic reconnection where the opposite polarity emerges. The magnetic reconnection triggers the prominence oscillations, as well as its loss of equilibrium, which finally leads to the eruption of the prominence. It is also found that the reconnection between the emerging flux and the pre-existing magnetic loop proceeds in an intermittent, probably quasi-periodic, way. Title: SUMER-Hinode observations of microflares: excitation of molecular hydrogen Authors: Innes, D. E. Bibcode: 2008A&A...481L..41I Altcode: 2007arXiv0712.0983I Context: Concentrations of H2 have been detected by SUMER in active region plage. The H2 is excited by O VI line emission at 1031.94 Å which, although not observed, must be brightening along with the observed transition region line, Si III 1113.24 Å.
Aims: We investigate the excitation of H2 and demonstrate the association between the observed H2 emission and footpoints of X-ray microflares.
Methods: We have made co-ordinated observations of active region plage with the spectrometer SUMER/SoHO in lines of H2 1119.10 Å and Si III 1113.24 Å and with XRT/Hinode X-ray and SOT/Hinode Ca II filters.
Results: In six hours of observation, six of the seven H2 events seen occurred near a footpoint of a brightening X-ray loop. The seventh is associated with an unusually strong Si III plasma outflow.
Conclusions: Microflare energy dissipation heats the chromosphere, reducing its opacity, so that O VI microflare emission is able to reach the lower layers of the chromosphere and excite the H2. Title: SOHO/SUMER observations of prominence oscillation before eruption Authors: Chen, P. F.; Innes, D. E.; Solanki, Sami Bibcode: 2008cosp...37..502C Altcode: 2008cosp.meet..502C Coronal mass ejections (CMEs) often reveal some precursors in the initiation phase, such as X- ray brightening and filament darkening, which are useful for CME modeling and space weather forecast. With the SOHO/SUMER spectroscopic observations of the 2000 September 26 event, we propose another precursor for CME eruptions, namely, long-time prominence oscillations. The observations indicate that a siphon flow was moving from the proximity of the prominence to a far site, which was followed by repetitive Hα surges and continual prominence oscillations. The oscillation lasted 4 hours before the prominence erupted as a blob-like CME. The analysis of the multiwavelength data indicates that the whole series of processes fits well into the emerging flux trigger mechanism for CMEs. In this mechanism, emerging magnetic flux drives a siphon flow due to increased gas pressure where the background polarity emerges. It also drives Hα surges through magnetic reconnection where the opposite polarity emerges. The magnetic reconnection triggers the prominence oscillations, as well as its loss of equilibrium, which finally leads to the eruption of the prominence. It is also found that the reconnection between the emerging flux and the pre-existing magnetic loop proceeds in an intermittent, probably quasiperiodic, way. Title: Coronal Heating by Small Scale Eruptive Events on Quiet sun Investigated By Coaligned Observations From Soho and Hinode Authors: Attie, R.; Innes, D. Bibcode: 2007AGUFMSH22A0835A Altcode: Co-ordinated observations with Soho and Hinode were made of all layers of the quiet Sun atmosphere. Observations were made from photospheric to lower corona lines. The region covered quiet Sun and soft X-ray bright points. Magnetic data and Doppler maps are provided by high resolution MDI-SUMER/Soho and SP- SOT/Hinode. In the meantime XRT-EIS/Hinode could track the whole evolution of microflares showing up on some bright points. In many aspects they look like coronal jets. These observations provide evidence of acceleration and heating of plasma in quiet Sun expelled in the lower corona. Title: Jets or High-Velocity Flows Revealed in High-Cadence Spectrometer and Imager Co-observations? Authors: Madjarska, M. S.; Doyle, J. G.; Innes, D. E.; Curdt, W. Bibcode: 2007ApJ...670L..57M Altcode: 2007arXiv0710.2199M We report on active region EUV dynamic events observed simultaneously at high cadence with SOHO SUMER and TRACE. Although the features appear in the TRACE Fe IX/X 171 Å images as jets seen in projection on the solar disk, the SUMER spectral line profiles suggest that the plasma has been driven along a curved large-scale magnetic structure, a preexisting loop. The SUMER observations were carried out in spectral lines covering a large temperature range from 104 to 106 K. The spectral analysis revealed that a sudden heating from an energy deposition is followed by a high-velocity plasma flow. The Doppler velocities were found to be in the range from 90 to 160 km s-1. The heating process has a duration which is below the SUMER exposure time of 25 s while the lifetime of the events is from 5 to 15 minutes. The additional check on soft X-ray Yohkoh images shows that the features most probably reach 3 MK (X-ray) temperatures. The spectroscopic analysis showed no existence of cold material during the events. Title: High Velocity Doppler Shift Observations of 10 MK Flare Plasma Authors: Innes, D. E.; Wang, T. J. Bibcode: 2007ASPC..369..481I Altcode: SOHO/SUMER observations in the corona above limb active regions have detected high Doppler shifts at the time of flares in high temperature lines in three situations: 1) At CME onset as the active region loops disrupt; 2) At the top of a supra-arcade at the time of downflows; 3) In oscillating flare loops. The main aspects of each are given. Questions arising from the observations and their resolution by Solar-B are suggested. Title: Determination of the Coronal Magnetic Field from Hot-Loop Oscillations Observed by SUMER and SXT Authors: Wang, Tongjiang; Innes, Davina E.; Qiu, Jiong Bibcode: 2007ApJ...656..598W Altcode: 2006astro.ph.12566W We apply a new method to determine the magnetic field in coronal loops, using observations of coronal loop oscillations. We analyze seven Doppler-shift oscillation events detected by SUMER in the hot flare line Fe XIX to obtain the oscillation periods of these events. The geometry, temperature, and electron density of the oscillating loops are measured from coordinated multichannel soft X-ray imaging observations from SXT. All the oscillations are consistent with standing slow waves in their fundamental mode. These parameters are used to calculate the magnetic field of coronal loops based on MHD wave theory. For the seven events, the plasma β is in the range 0.15-0.91 with a mean of 0.33+/-0.26, and the estimated magnetic field varies between 21 and 61 G with a mean of 34+/-14 G. With background emission subtracted, the estimated magnetic field is reduced by 9%-35%. The maximum background subtraction gives a mean of 22+/-13 G in the range 12-51 G. We discuss measurement uncertainties and the prospect of determining coronal loop magnetic fields from future observations of coronal loops and Doppler-shift oscillations. Title: Nanoflare model of emission line radiance distributions in active region coronae Authors: Safari, H.; Innes, D. E.; Solanki, S. K.; Pauluhn, A. Bibcode: 2007msfa.conf..359S Altcode: Nanoflares are small impulsive bursts of energy that blend with and possibly make up much of the solar background emission. Determining their overall contribution is central to understanding the heating of the solar corona. Here, a simple nanoflare model based on three key parameters: the flare rate, the flare damping time, and the power-law slope of the flare energy frequency distribution has been used to simulate emission line radiances observed by SUMER in the corona above an active region. The three lines analysed, Fe XIX, Ca XIII, and Si III have very different formation temperatures, damping times and flare rates but all suggest a power-law slope greater than 2. Thus it is possible that nanoflares provide a significant fraction of the flare energy input to active region coronae. Title: Wavelet-based method for coronal loop oscillations analysis Authors: Tothova, D.; Innes, D. E.; Solanki, S. K. Bibcode: 2007msfa.conf..265T Altcode: We study the properties of Doppler shift oscillations observed in hot coronal loops by SoHO/SUMER. These oscillations have been identified as magnetoacoustic slow mode standing waves and may be an important magnetic field diagnostic for the oscillating loops. Visual inspection of the SUMER data suggests that one in three microflares trigger oscillation. So for an average active region we can expect several oscillation events per hour. To study the statistics of the oscillations, automatic identification and classification of the events is required. We have performed a Wavelet analysis on a 12 hour time series of SUMER Fe XIX data and find that almost all of the oscillation events in the data set are identified by this technique, with very few false positives. The method is expected to be useful for the analysis of future Ca XVII and Fe XXIV spectra of microflares observed with HINODE/EIS. Title: Fe XIX observations of active region brightenings in the corona Authors: Wang, T. J.; Innes, D. E.; Solanki, S. K. Bibcode: 2006A&A...455.1105W Altcode: Small flarelike brightenings seen in the hot flare line, Fe XIX, by the spectrometer SUMER on SOHO are analysed. We observe active region coronae about 30 Mm off the limb of the Sun for a period of several days. Brightenings are observed with a frequency 3-14 per hour and their lifetimes range from 5-150 min, with an average of about 25 min. The measured size of the events along the spectrometer slit range from 2-67 Mm, but most are around 7 Mm. Like soft X-ray active region transient brightenings, they range in estimated thermal energy from 1026 to 1029 erg with a power law index of 1.7 to 1.8, beyond 1027 erg. We conclude that they are the coronal parts of loops heated to > 6 MK by soft X-ray microflares. Title: Microflares and Loop Oscillations Authors: Innes, D. E.; Wang, T. J.; Solanki, S. K.; Tothova, D. Bibcode: 2006ESASP.617E.132I Altcode: 2006soho...17E.132I No abstract at ADS Title: Determination of the Coronal Magnetic Field by Hot Loop Oscillations Observed by SUMER and SXT Authors: Wang, Tongjiang; Innes, D. E.; Qiu, J. Bibcode: 2006SPD....37.1803W Altcode: 2006BAAS...38..246W Strongly damped Doppler shift oscillations in hot coronal loops were recently detected with SOHO/SUMER as a new phenomenon, which are best interpreted in terms of standing slow mode waves. A series of papers have been done to explore their physical properties, damping mechanism and excitations. In this paper, we analyze seven oscillation cases observed with both SUMER and SXT. With SXT images we measure the geometrical parameters, plasma density and temperature of the oscillating loops. Combined with the oscillation periods measured from SUMER, we show that their information can be applied to determine the mean coronal field strength in the loops based on the MHD wave theory. The restriction of this method and measurement uncertainties will be discussed. Title: Microflares and Hot Coronal Loop Oscillations Authors: Tothova, Danica; Innes, D. E. Bibcode: 2006SPD....37.1316T Altcode: 2006BAAS...38..243T Detailed observations of waves and oscillations in coronal loops may be useful in the diagnostics of coronal plasma (Roberts et. al 1984). Very recent SOHO/SUMER spectroscopic observations have revealed strongly damped slow-mode oscillations in the hot coronal loops (e.g. Wang et al. 2002). They can be seen in the hot flare-like lines (e.g. Fe XIX) as intensity and Doppler shift fluctuations with large initial Doppler velocities. They are triggered by microflares, small A to C class X-ray brightenings that occur at a rate of about 10 per hour in an 'average' active region (Shimizu et al. 1992). We study the basic characteristics of the oscillations and discuss their importance in the context of models of microflare loop excitation. Title: Flarelike Brightenings of Active Region Loops Observed with SUMER Authors: Wang, T. J.; Innes, D. E.; Solanki, S. K.; Curdt, W. Bibcode: 2005ESASP.600E.105W Altcode: 2005ESPM...11..105W; 2005dysu.confE.105W No abstract at ADS Title: International Scientific Conference on Chromospheric and Coronal Magnetic Fields Authors: Innes, D. E.; Lagg, A.; Solanki, S. A. Bibcode: 2005ESASP.596E....I Altcode: 2005ccmf.confE....I No abstract at ADS Title: International Scientific Conference on Chromospheric and Coronal Magnetic Fields Authors: Innes, D. E.; Lagg, A.; Solanki, S. A. Bibcode: 2005ESASP.596.....I Altcode: 2005ccmf.conf.....I No abstract at ADS Title: Initiation of hot coronal loop oscillations: Spectral features Authors: Wang, T. J.; Solanki, S. K.; Innes, D. E.; Curdt, W. Bibcode: 2005A&A...435..753W Altcode: We explore the excitation of hot loop oscillations observed with the SUMER spectrograph on SOHO by analysing Fe XIX and Fe XXI spectral line profiles in the initial phase of the events. We investigate all 54 Doppler shift oscillations in 27 flare-like events, whose physical parameters have been measured so far. In nearly 50% of the cases, the spectral evolution reveals the presence of two spectral components, one of them almost undisturbed, the other highly shifted. We find that the shifted component reaches maximum Doppler shift (on the order of 100-300 km s-1) and peak intensity almost simultaneously. The velocity amplitude of the shifted component has no correlation with the oscillation amplitudes. These features imply that in these events the initial shifts are not caused by the locally oscillating plasma (or waves), but most likely by a pulse of hot plasma travelling along the loop through the slit position. This interpretation is also supported by several examples showing that standing slow mode waves are set up immediately after the initial line shift pulse (standing slow mode waves are inferred from the 1/4-period phase relationship between the velocity and intensity oscillations). We re-measure the physical parameters of the 54 Doppler oscillations by fitting the time profiles excluding the first peak, and find that the periods are almost unchanged, damping times are shorter by 5%, and amplitudes are smaller by 37% than measured when the first peak is included. We also measure the velocity of the net (background) flow during the oscillations, which is found to be nearly zero. Our result of initial hot flows supports the model of single footpoint (asymmetric) excitation, but contradicts chromospheric evaporation as the trigger. Title: Comparison of blinkers and explosive events: A case study Authors: Bewsher, D.; Innes, D. E.; Parnell, C. E.; Brown, D. S. Bibcode: 2005A&A...432..307B Altcode: Blinkers are brightenings at network cell junctions that are traditionally identified with SOHO/CDS and explosive events or high velocity events are identified in high resolution UV spectra obtained from HRTS and SOHO/SUMER. Criteria are determined to facilitate objective automatic identification of both blinkers and explosive events in both SOHO/CDS and SOHO/SUMER data. Blinkers are identified in SUMER data, if the temporal resolution of the data is reduced to that of CDS. Otherwise short lived, localised intensity enhancements that make up the blinker are identified. Explosive events are identified in CDS data when the line width is significantly increased, and occasionally if there is an enhancement in the wing of the line profile. A theoretical statistical model is presented which hypothesises that blinkers and explosive events are random and not connected in any way. The results given in this paper suggest that this hypothesis can not be rejected and our probability interpretation of the recent results of Brković & Peter (2004, A&A, 422, 709) are inconclusive.

Appendices A and B are only available in electronic form at http://www.edpscienc es.org Title: Probability Analysis of Coincident Blinkers and Explosive Events Authors: Bewsher, D.; Brown, D.; Innes, D.; Parnell, C. Bibcode: 2004ESASP.575..465B Altcode: 2004soho...15..465B No abstract at ADS Title: SUMER Observations of Active Region Loop Dynamics Authors: Innes, D.; Wang, T. Bibcode: 2004ESASP.575..553I Altcode: 2004soho...15..553I No abstract at ADS Title: Line profile characteristics of solar explosive event bursts Authors: Ning, Z.; Innes, D. E.; Solanki, S. K. Bibcode: 2004A&A...419.1141N Altcode: The spatial structure and temporal evolution of explosive events are explored using spectral observations of the Si IV 1393 Å line obtained with the Solar Ultraviolet Measurements of Emitted Radiation spectrograph (SUMER). Three areas of quiet Sun near disk center, 8 arcsec×120 arcsec each, were rastered with a cadence of less than 1 min for a period of over half an hour. Events were identified by a non-Gaussian excess in the blue and/or red wings of the line. We found 21 sites where events re-occur. The sites are clustered near regions of evolving network fields seen in low resolution Michelson Doppler Imager (MDI) magnetic field images. Events tend to expand and shrink across the surface with a speed ∼ 25 km s-1. Individual events were also seen to move at this speed across the solar surface. Consecutive events often have different line profile characteristics and sizes, suggesting changes in the structure of the accelerated plasma from event to event. In the majority of events, blue and red wing brightenings do not produce a simultaneous line intensity increase. Also, the red and blue wing emission is mostly co-spatial implying either non-directed flow or jets orientated along the line-of-sight (i.e. out from and towards the solar surface). The explosive events within a burst are in some cases separated by 3-5 min, suggesting that oscillations, which are known to have such periods, may play a role in triggering the individual events of a burst. Title: Dynamic Behaviors of the Quiet Sun Seen by SUMER Authors: Ning, Z.; Innes, D. E.; Solanki, S. K. Bibcode: 2004ESASP.547..297N Altcode: 2004soho...13..297N No abstract at ADS Title: Transition Region Dynamics Authors: Innes, D. E. Bibcode: 2004ESASP.547..215I Altcode: 2004soho...13..215I The transition region appears to be a complicated mix of highly dynamic, rapidly cooling loop-like structures in a background of steady loops and funnels with gravitationally stratified chromosphere-corona transition zones. This review concentrates on the time varying emission. The heating and plasma acceleration appears to be strongly dependent on the photospheric field. Parallels are discussed with active region dynamics and in particular the influence of the underlying field on event character. Explosive events are mostly found above complex field configurations, whereas brightenings not associated with flows occur at closed-bipole sites. Simulations of reconnection, rotation and shock generation are briefly described in the context of the transition region flows. Title: Overview of Slow Mode Oscillations in Hot Coronal Loops Observed by SUMER Authors: Wang, T. J.; Solanki, S. K.; Curdt, W.; Innes, D. E. Bibcode: 2004IAUS..219..712W Altcode: 2003IAUS..219E..70W No abstract at ADS Title: Observations of Sunward Flows in the 21 April 2002 Postflare Supra-Arcade Authors: Innes, D. E.; Wang, T. Bibcode: 2004ESASP.547..479I Altcode: 2004soho...13..479I Observations of the 21 April 2002 postflare emission are analysed to determine the properties of the dark structures falling sunward through the bright supra-arcade emission. TRACE 195 Å images show that the structures consist of a head followed by an undulating tail, falling with velocity km s. We examine two examples of relatively isolated inflows where the tail oscillations can be seen over about two and a half periods. The wavelength is , leading to a period min at any particular height. The head and tail structure do not appear to change as they fall through the outer 30-40 of the arcade, but as the head approaches the brighter arcade emission, it breaks and the tail undulations are rapidly damped. SUMER detected Fe XXI plasma emission with oscillating red and blue Doppler shifts of about 10 km s along the inflow edges. The wave amplitude of the tail oscillations both along and perpendicular to the line-of sight is about 2 . Title: SUMER spectral observations of post-flare supra-arcade inflows Authors: Innes, D. E.; McKenzie, D. E.; Wang, Tongjiang Bibcode: 2003SoPh..217..247I Altcode: On 21 April 2002 a large eruptive flare on the west limb of the Sun developed a bright, very dynamic, post-flare arcade. In TRACE 195 Å images, a series of dark, sunward moving flows were seen against the bright extreme ultraviolet (EUV) arcade. SUMER obtained a series of spectra of the dark EUV flows in the lines C ii, Fe xii, and Fe xxi at a fixed position above the limb. These spectra give spatially resolved line-of-sight velocities and emission measures for the arcade plasma over a temperature range 2×104 to 107 K. The flows are dark in all SUMER lines. The UV continuum longward (∼ 1350 Å) and shortward (∼ 675 Å) of the hydrogen Lyman limit is used to determine whether the dark 195 Å inflows are due to regions of low plasma density (plasma voids) or cold absorbing material. There is some evidence of absorption near the front of one of the inflows; however, along most of the dark channels there is no change in continuum ratio and we therefore conclude, as originally suggested by McKenzie and Hudson (1999), that they are plasma voids. Title: Observations of 1000 km s−1 Doppler shifts in 107 K solar flare supra-arcade Authors: Innes, D. E.; McKenzie, D. E.; Wang, Tongjiang Bibcode: 2003SoPh..217..267I Altcode: An X1.5 flare on the west limb of the Sun on 21 April 2002 developed a large supra-arcade about 30 min after flare onset. The growth of the supra-arcade can be followed in both TRACE 195 Å images and SUMER spectra. Its growth seems to be associated with dark (in TRACE images), sunward moving channels that descend onto the arcade from above. SUMER recorded Doppler shifts of 800-1000 km s−1 in Fe xxi 1354 Å from positions where this sunward flow interacts with the arcade tops. We describe the observations, focusing on the relationship of the high Fe xxi line shifts to the sunward moving dark flows. Title: Hot coronal loop oscillations observed with SUMER: Examples and statistics Authors: Wang, T. J.; Solanki, S. K.; Curdt, W.; Innes, D. E.; Dammasch, I. E.; Kliem, B. Bibcode: 2003A&A...406.1105W Altcode: We give an extensive overview of Doppler shift oscillations in hot active region loops obtained with SUMER. The oscillations have been detected in loops sampled 50-100 arcsec off the limb of the Sun in ultraviolet lines, mainly Fe Xix and Fe Xxi, with formation temperature greater than 6 MK. The spectra were recorded along a 300 arcsec slit placed at a fixed position in the corona above the active regions. Oscillations are usually seen along an extended section of the slit and often appear to be from several different portions of the loops (or from different loops). Different portions are sometimes in phase, sometimes out of phase and sometimes show phase shifts along the slit. We measure physical parameters of 54 Doppler shift oscillations in 27 flare-like events and give geometric parameters of the associated hot loops when soft X-ray (SXR) images are available. The oscillations have periods in the range 7-31 min, with decay times 5.7-36.8 min, and show an initial large Doppler shift pulse with peak velocities up to 200 km s-1. The oscillation periods are on average a factor of three longer than the TRACE transverse loop oscillations. The damping times and velocity amplitude are roughly the same, but the derived displacement amplitude is four or five times larger than the transverse oscillation amplitude measured in TRACE images. Unlike TRACE oscillations, only a small fraction of them are triggered by large flares, and they often recur 2-3 times within a couple of hours. All recurring events show initial shifts of the same sign. These data provide the following evidence to support the conclusion that these oscillations are slow magnetoacoustic standing waves in hot loops: (1) the phase speeds derived from observed periods and loop lengths roughly agree with the sound speed; (2) the intensity fluctuation lags the Doppler shifts by 1/4 period; (3) The scaling of the dissipation time of slow waves with period agrees with the observed scaling for 49 cases. They seem to be triggered by micro- or subflares near a footpoint, as revealed in one example with SXR image observations. However other mechanisms cannot as yet be ruled out. Some oscillations showed phase propagation along the slit in one or both directions with apparent speeds in the range of 8-102 km s-1, together with distinctly different intensity and line width distributions along the slit. These features can be explained by the excitation of the oscillation at a footpoint of an inhomogeneous coronal loop, e.g. a loop with fine structure.

Table \ref{osctab} and Appendices A and B are only available in electronic form at http://www.edpsciences.org Title: Overview of Recent Results on Coronal Loop Oscillations Authors: Wang, T. J.; Solanki, S. K.; Curdt, W.; Innes, D. E. Bibcode: 2003ANS...324...19W Altcode: 2003ANS...324..B18W No abstract at ADS Title: Slow-mode standing waves observed by SUMER in hot coronal loops Authors: Wang, T. J.; Solanki, S. K.; Innes, D. E.; Curdt, W.; Marsch, E. Bibcode: 2003A&A...402L..17W Altcode: We report the first detection of postflare loop oscillations seen in both Doppler shift and intensity. The observations were recorded in an Fe Xix line by the SUMER spectrometer on SOHO in the corona about 70 min after an M-class flare on the solar limb. The oscillation has a period of about 17 min in both the Doppler velocity and the intensity, but their decay times are different (i.e., 37 min for the velocity and 21 min for the intensity). The fact that the velocity and the intensity oscillations have exactly a 1/4-period phase difference points to the existence of slow-mode standing waves in the oscillating loop. This interpretation is also supported by two other pieces of evidence: (1) the wave period and (2) the amplitude relationship between the intensity and velocity are as expected for a slow-mode standing wave. Title: Comparison of Blinkers and Explosive Events Authors: Bewsher, D.; Innes, D.; Parnell, C. E. Bibcode: 2003SPD....34.1617B Altcode: 2003BAAS...35Q.836B There has been much speculation over recent years as to whether blinkers and explosive events are the same phenomena observed with different instruments.

Blinkers were first observed by Harrison (1997) by eye using SOHO/CDS, but more recently Brković et al. (2001) and Bewsher et al. (2002) have developed automated methods of identifying these events. Blinkers are small scale intensity enhancements seen in the transition region, with a mean area of 3 x 107 km2 and a mean lifetime of 16 minutes. The Doppler velocities of blinkers are preferentially more red-shifted than the typical transition region plasma. The range of these enhanced velocities, however, are no larger than the typical spread of Doppler velocities in these regions.

Explosive events were first observed using HRTS (Bruckener and Bartoe, 1983) as high energy turbulent events and jets. More recently, they have been observed using SOHO/SUMER. They have a typical size of 2" - 4" and have an average lifetime of 60 seconds. Line profiles of explosive events show strong non-Gaussian enhancements of both wings of the profile, and velocities associated with them range from +/- 50 - +/- 250 km s-1.

Examples will be presented showing (i) a co-spatial and co-incident blinker and explosive event; (ii) a blinker with no associated explosive event; and (iii) an explosive event with no associated blinker. We investigate the lightcurves and line profiles of the regions to explain the relationship, if any, between blinkers and explosive events. Title: Simultaneous SUMER and TRACE Observations of Supra-arcade Downflows and Oscillations Authors: McKenzie, D. E.; Innes, D. E.; Wang, T. Bibcode: 2003SPD....34.1510M Altcode: 2003BAAS...35..832M The 21 April 2002 X-class solar flare exhibited supra-arcade downflows of the type described by McKenzie and Hudson (1999). The flare was observed simultaneously by several observatories, and the downflows were clearly imaged by TRACE and SOHO/SUMER. We present a comparison of the TRACE and SUMER data concerning the supra-arcade downflows, and demonstrate that the dark downflow features are consistent with regions of locally depressed plasma density. Furthermore, the implications of the oscillatory behavior of the supra-arcade spikes for coronal seismology will be considered.

We gratefully acknowledge support from NASA, DARA, CNES, and ESA. Title: Hot loop oscillations seen by SUMER Authors: Wang, T. J.; Solanki, S. K.; Curdt, W.; Innes, D. E.; Dammasch, I. E. Bibcode: 2003AN....324..340W Altcode: No abstract at ADS Title: Mass Motions and Plasma Properties in the 107 K Flare Solar Corona Authors: Landi, E.; Feldman, U.; Innes, D. E.; Curdt, W. Bibcode: 2003ApJ...582..506L Altcode: In the present work, we analyze Solar Ultraviolet Measurement of Emitted Radiation (SUMER) observations of a solar limb flare that occurred on 1999 May 9. The analyzed data cover a time span of around 6.4 hr, during which an M-7.6 flare erupted and decayed in the field of view. Two selected regions along the SUMER slit have been considered for quantitative analysis. The main purpose of the present analysis is to measure the mass motions and the nonthermal velocities of the postflare plasmas and their temporal evolution. To achieve this we use lines having formation temperatures in the 2.5×106 to 2×107 K range from which we derive net mass motions and nonthermal velocities and compare them with the properties of the surrounding plasma not affected by the flare activity. To understand the physical conditions of the flaring plasma and of the surrounding material, we derive electron temperature, electron density, and emission measures of the emitting plasma. We find that bulk motions, initially of the order of several hundreds of kilometers per second in both directions, decay within 10 minutes from the flare onset; nonthermal velocities decay to preflare values of around 30 km s-1 in less than 2 hr from the maximum value of around 100 km s-1 at flare onset. The measured electron density does not seem to change during activity, while the flare plasma temperature steadily decays to preflare values. The temperature evolution is consistent with a radiatively cooling plasma, although the uncertainties associated to the measurement of the variation of thermal energy of the flare plasma prevent a definitive conclusion on possible continuous heating of the flaring plasma. Title: Doppler oscillations in hot coronal loops Authors: Curdt, W.; Wang, T. J.; Innes, D. E.; Solanki, S. K.; Dammasch, I. E.; Kliem, B.; Ofman, L. Bibcode: 2002ESASP.506..581C Altcode: 2002ESPM...10..581C; 2002svco.conf..581C Recently, a new kind of damped oscillations of hot coronal loops was revealed by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on SOHO. Such events seem to be a common feature observed in active region loops, seen very often when these lines brighten. The oscillations always have an impulsive trigger and are strongly damped while they cool down. However, in lines formed at coronal temperatures of ≍2 MK never any signature of these oscillations has been observed. In this study, we present the main properties of Doppler oscillations derived from a statistical study of 17 flare-like events, and a comparison with TRACE transverse loop oscillations. We also discuss the oscillation modes and their damping mechanism. Title: Initial features of an X-class flare observed with SUMER and TRACE Authors: Wang, T. J.; Solanki, S. K.; Innes, D. E.; Curdt, W. Bibcode: 2002ESASP.505..607W Altcode: 2002IAUCo.188..607W; 2002solm.conf..607W A class X1.5 flare started on the solar limb at 00:43 UT on 21 April 2002, which was associated with a CME observed at 01:27 UT by LASCO C2. The coordinated analyses of this flare include TRACE 195 Å images and SUMER spectra in lines of Fe XXI, Fe XII, and C II. We find that: 1) The flare began with a jet seen by TRACE, which was detected by SUMER in the C II line as a strong brightening with blue shifts up to 170 km s-1. At that time only weak emission was detected in Fe XII and Fe XXI. 2) Subsequently, a weak looplike brightening started south of the jet, moving outwards with an average speed of about 150 km s-1. The SUMER spectra responded this moving loop as separatingly brightenings, visible only in the Fe XXI line. The southwards moving component contains red- and blue-shifted emission features and has an apparent speed of ~120 km s-1. The absence of signatures in Fe XII and C II lines indicates that the moving weak loop seen by TRACE corresponds to the emission from very hot plasma, in a blend line in the 195 Å bandpass due to Fe XXIV formed at T > 10 MK. 3) The trigger mechanism of the flare and associated CME can be interpreted in the same way as that proposed by Wang et al. (2002) for an event with similar initial features. Title: Hot loop oscillations seen by SUMER: examples and statistics Authors: Wang, T. J.; Solanki, S. K.; Curdt, W.; Innes, D. E.; Dammasch, I. E. Bibcode: 2002ESASP.505..199W Altcode: 2002solm.conf..199W; 2002IAUCo.188..199W We measure physical parameters of Doppler-shift oscillations in 17 flare-like events. These events have been recorded by the Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on SOHO, along a slit fixed above limb active regions. The selected spectral windows contain emission lines with formation temperatures from ~104 to 107K. The events were only detected in hot flare lines, without any signature in lines formed around 2×106K. Similarly, the Doppler shift oscillations occur in regions coincident with hot soft X-ray loops, but not with EUV loops. The oscillations have periods of 11 - 31 min, with an exponential decay time of 5.5 - 29 min, and show an initial large shift pulse with peak velocities up to 200 km s-1. Several indications suggest that the Doppler oscillations are incompressible coronal loop oscillations, that are usually excited impulsively by weak flare (or microflare) events that also produced a strong emission increase at 5 - 8×106K. Title: Doppler Shift Oscillations of Hot Solar Coronal Plasma Seen by SUMER: A Signature of Loop Oscillations? Authors: Wang, Tongjiang; Solanki, S. K.; Curdt, W.; Innes, D. E.; Dammasch, I. E. Bibcode: 2002ApJ...574L.101W Altcode: We report observations of strongly damped Doppler shift oscillations detected in a flare line, Fe XIX, with the Solar Ultraviolet Measurement of Emitted Radiation spectrometer. Spectra were recorded above an active region at the western limb of the Sun, from lines with formation temperatures ranging from 0.01 to 10 MK. However, the oscillations were seen only in the hot plasma (>6 MK) lines. The Doppler oscillations have periods of 14-18 minutes, with an exponential decay time of 12-19 minutes, and show an initial large blueshift pulse with peak velocities up to 77 km s-1. Several indications suggest that the Doppler oscillations are incompressible coronal loop oscillations that are excited impulsively by a flarelike event that also produced a strong increase in Fe XIX emission. Title: Oscillating hot loops observed by SUMER Authors: Wang, T. J.; Solanki, S. K.; Curdt, W.; Innes, D. E.; Dammasch, I. E. Bibcode: 2002ESASP.508..465W Altcode: 2002soho...11..465W We report observations of Doppler shift oscillations in hot flare lines emitted from active region loops. The Solar Ultraviolet Measurements of Emitted Radiation (SUMER) spectrometer on SOHO recorded spectra of limb active regions loops in several emission lines with formation temperatures from ~104 to 107K. The events were only detected in the hot flare lines, without any signature in lines formed around 2×106K. There is a large shift pulse of up to 190 km s-1 during the rising phase of the flux which is followed by two or three periods of strongly damped alternating red and blue shift oscillations with periods in the range 12-31 min. Slow mode standing waves match the observed period. However, the initial large Doppler shift pulse suggests that the waves are impulsively generated. Unlike the oscillating loops seen in the TRACE images, these Doppler shift oscillations are sometimes seen without an associated flare. Title: Coordinated observations of the quiet Sun transition region using SUMER spectra, TRACE images and MDI magnetograms Authors: Innes, D. E. Bibcode: 2001A&A...378.1067I Altcode: The relationship between the transition region ultraviolet emission and the underlying magnetic field is explored through a detailed analysis of SUMER SI IV line profiles, TRACE C IV, continuum and 171 Å intensities, and MDI high resolution magnetic field measurements. The observations track a narrow area of quiet Sun near disk center over a period of 3 hours. Highly variable emission is found throughout. The most dramatic line Doppler shift and brightness variations come from a region of complex field evolution. The brightenings sometimes have faint elongated extensions in the TRACE C IV images. In most events with high Doppler shifts, the SI IV line wing reveals plasma flow 1-2 min before the line core brightens which suggests that plasma acceleration precedes plasma compression and/or heating. SImultaneous measurement of transition region densities using O IV line ratios imply large density fluctuations in the transition region plasma. There is an indication of waves of compression and rarefaction crossing the spectrometer's field-of-view. The waves' speed across the solar surface is between 20-40 \kms, and the compression may be as high as 10. In space-time images density fluctuations are much more prevalent and conspicuous than brightenings. In several cases the waves seem to start at the position of SI IV brightenings. Title: Large Doppler Shifts in X-Ray Plasma: An Explosive Start to Coronal Mass Ejection Authors: Innes, D. E.; Curdt, W.; Schwenn, R.; Solanki, S.; Stenborg, G.; McKenzie, D. E. Bibcode: 2001ApJ...549L.249I Altcode: We report observations, taken with the Solar Ultraviolet Measurements of Emitted Radiation spectrometer, of spatially resolved high red and blue Doppler shifts (up to 650 km s-1) from X-ray-emitting plasma in the corona above a flare. The high Doppler shifts are seen minutes after a fast, faint optical front is seen racing through the same part of the corona in images taken with the Mirror Coronagraph for Argentina. The association of the large-scale fast optical emission front with soft X-ray emission and high Doppler shifts suggests plasma heating and acceleration in the wake of a shock. Title: Flare and CME onset: UV spectra show fast 3-D flow Authors: Innes, D. E. Bibcode: 2001IAUS..203..374I Altcode: We present observations taken in the corona above a flare that occurred on the west limb of the Sun. SUMER spectra show large red (400 km/s) and blue (700 km/s) Dopplershifts in Fe XX (107 K), Cr XVI (5×106 K), Si IX (106 K) and O III (105 K) emission lines. These shifts are associated with a fast moving (500 km/s) optical emission front detected in high cadence images, taken with the coronagraph MICA. Yohkoh images, taken 8 min after the hard X-ray peak, show fast soft X-ray ejecta that can be extrapolated back to the position of pre-flare coronal arcade structure seen in EIT 195 images. The observations are interpreted as evidence of a blast wave propagating through the active region coronal loop structure very early in the flare evolution. Title: Spectroscopic features in the EUV emission of a M8 flare observed by SUMER Authors: Curdt, W.; Landi, E.; Feldman, U.; Innes, D.; Dwivedi, B.; Wilhelm, K. Bibcode: 2001IAUS..203..260C Altcode: On May 9, 1999 a flare of size M8 occurred while SUMER obtained a spectral scan above the active region NOAA 8537 at the west limb. We recorded spectra during the pre-flare phase, at flare onset, and during the decay phase. More than 60 flare lines were observed during this event, which include Fe XVIII - Fe XXIII lines that provide evidence of 107 K plasmas. We also recorded lines from He-like ions, such as Ne IX, Na X, Mg XI or Si XIII. Accurate wavelength measurements of such lines are of interest in basic atomic physics studies. Using plasma diagnostic techniques, we investigated the temporal evolution of the electron densities and temperatures during the event. Since the spectra contain lines from many different elements, we were able to determine elemental abundances in the flaring plasma. Title: Injection of energetic protons during solar eruption on 1999 May 9: Effect of flare and coronal mass ejection Authors: Torsti, J.; Kocharov, L.; Innes, D. E.; Laivola, J.; Sahla, T. Bibcode: 2001A&A...365..198T Altcode: A solar energetic particle (SEP) event was observed on 1999 May 9 by the Energetic and Relativistic Nuclei and Electron instrument (ERNE) onboard the Solar and Heliospheric Observatory (SOHO) spacecraft in association with a coronal mass ejection (CME) and X-ray flare at the western limb. Near flare onset the active region coronal loop structure was seen to erupt and simultaneous blue and red shift velocities of the hot plasma were recorded by the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) instrument onboard SOHO. We observe for the first time three periods of the SEP injection in a single event: (i) the first, extremely-hard spectrum injection triggered by the passage of the flare initiated coronal (shock) wave; (ii) a moderately-hard spectrum phase starting about half a hour later, proceeding and ceasing concurrently with metric continuum radio burst; (iii) a prolonged soft spectrum injection dominating in the late phase of the event, after about 1.5 h from the first proton production. The CME bow shock acceleration provides a straightforward explanation of the final spectral redressing, whereas the first acceleration seems triggered by the flare. These observations lead us to conclude that the 1999 May 9 SEP event was caused by a combination of coronal and interplanetary acceleration processes contributing with varying importance at different stages of the solar eruption associated with both flare and CME. Comparison with other events suggests that it is a common property of mixed SEP events. Title: Transition Region: Explosive Events Authors: Innes, D. Bibcode: 2000eaa..bookE2003I Altcode: Explosive events are frequent, very small bursts that occur throughout the solar transition region. There are something like thirty to forty thousand of these events on the Sun at any time. Each event lasts for roughly a minute so every second there are about 600 new events. Present-day solar telescopes are just able to resolve the largest of these events. The events give an impression of explosi... Title: A study of opacity in SOHO-SUMER and SOHO-CDS spectral observations. I. Opacity deduction at the limb Authors: Brooks, D. H.; Fischbacher, G. A.; Fludra, A.; Harrison, R. A.; Innes, D. E.; Landi, E.; Landini, M.; Lang, J.; Lanzafame, A. C.; Loch, S. D.; McWhirter, R. W. P.; Summers, H. P. Bibcode: 2000A&A...357..697B Altcode: A study is presented of the optical thickness of spectral lines of carbon, nitrogen and oxygen ions in the quiet sun. The observations consist of cross limb scans by the SUMER and CDS spectrometers on the SOHO spacecraft. A maximum likelihood spectral line fitting code has been adapted to analyse the multiplet profiles and to provide an assessment of errors in the count rates, especially of close lying components. Branching multiplet component ratios are presented as a function of position across the limb and contrasted with theoretical ratios in the optically thin case. The emergent fluxes are analysed in an escape probability model to deduce the optical thicknesses in the various spectral lines. Different specifications of the escape probability are examined. These are used to compare the observations with a geometric model of the emitting layer thickness across the limb and the thinning of the emitting layer above the limb. Classification of the deviations of quiet sun spectral line intensities from the optically thin case is given to assist in the critical selection of lines for differential emission measure analysis. This is linked to a general purpose code for the calculation of the influence of the line radiation fields on the local excited state population structure of the selected ions so that the fluxes in any spectral lines can be predicted. The Atomic Data and Analysis Structure (ADAS) was used for the atomic calculations and data of the paper. Title: A study of extreme ultraviolet blinker activity Authors: Harrison, R. A.; Lang, J.; Brooks, D. H.; Innes, D. E. Bibcode: 1999A&A...351.1115H Altcode: In a previous paper (Harrison, 1997a), we reported on the existence of extreme ultraviolet (EUV) flashes, known as blinkers, which were identified in the quiet Sun network using the CDS instrument on board the Solar and Heliospheric Observatory. Since then a number of dedicated observations have been made and we report here on an analysis of 97 blinker events. We identify blinker spectral, temporal and spatial characteristics, their distribution, frequency and general properties, across a broad range of temperatures, from 20,000 K to 1,200,000 K. The most significant brightenings were found in the transition region temperature lines of O III, O IV and O V, with modest or no detectable increases at higher or lower temperatures. A typical blinker event has a duration of order 1000 s, though the detection of short-duration blinkers may well be limited by the observation methods. However, a long tail of longer-duration blinkers puts the average blinker duration at almost 2400 s. Comparisons to plasma cooling times establish firmly that there is a continuous energy input throughout the blinker event. The projected blinker onset rate for the entire solar surface is 1.24 s-1 i.e. 3,000 blinker events may be in progress at any point in time. An examination of the line ratios shows a remarkable feature. Ratios of lines from O III, O IV and O V show no significant change throughout the blinker event and this indicates that the blinkers are predominantly caused by inceases in density or filling factor. The intensity signatures of the blinkers are modelled using a basic time dependent code and this confirms that the lack of a change in the oxygen line ratios is consistent with a density or filling factor increase in a plasma cooling from a temperature above 5 x 105 K. We estimate the thermal energy content of an average blinker at 2 x 1025 erg and consider this figure and the total blinker rate in the light of the energy required for coronal heating. The results are used to compare blinker activity to reported micro-flare, network flare and explosive event activity, and to discuss their potential role in coronal heating and solar wind acceleration processes. Finally, a blinker model is presented which consists of the merging of a closed magnetic system with pre-existing open field lines in the network. Title: SUMER Observations of Intensity Oscillations in the Transition Region of a Sunspot Authors: Rendtel, J.; Staude, J.; Innes, D. E.; Wilhelm, K. Bibcode: 1999ASPC..184..271R Altcode: UV spectroscopic data obtained with the SUMER spectrograph aboard SOHO have been analysed to detect oscillations in the chromosphere-corona transition region (TR) above sunspots. We observed the active region NOAA 7986 in the wavelength bands around the Ne VIII line at 770.4 Å and the C IV line at 1548.1 Å on August 29, 1996, between 09:08 UT and 13:31 UT. Simultaneous observations with the Normal Incidence Spectrometer of CDS aboard SOHO have shown, that the spot had a bright EUV plume at TR temperatures. A preliminary data analysis indicates intensity oscillations in the 2-minute range (7.3...7.9 mHz) in both spectral lines. The temporal variation of oscillatory power in the two spectral lines is generally in opposite directions, i.e. during an increase of oscillatory power in the Ne VIII line we find a decrease in the C IV line. A similar but smaller tendency is observed in the average intensity of the line profiles. This hints at a non-adiabatic behaviour of the oscillations and a slow cooling of the emitting sunspot plume region. Title: The quiet Sun extreme ultraviolet spectrum observed in normal incidence by the SOHO coronal diagnostic spectrometer Authors: Brooks, D. H.; Fischbacher, G. A.; Fludra, A.; Harrison, R. A.; Innes, D. E.; Landi, E.; Landini, M.; Lang, J.; Lanzafame, A. C.; Loch, S. D.; McWhirter, R. W. P.; Summers, H. P.; Thompson, W. T. Bibcode: 1999A&A...347..277B Altcode: The extreme ultraviolet quiet Sun spectrum, observed at normal incidence by the Coronal Diagnostic Spectrometer on the SOHO spacecraft, is presented. The spectrum covers the wavelength ranges 308-381 Ä and 513-633 Ä and is based on data recorded at various positions on the solar disk between October 1996 and February 1997. Datasets at twelve of these `positions' were judged to be free from active regions and data faults and selected for detailed study. A constrained maximum likelihood spectral line fitting code was used to analyse the spectral features. In all over 200 spectrum lines have been measured and about 50% identified. The line identification process consisted of a number of steps. Firstly assignment of well known lines was made and used to obtain the primary wavelength calibration. Variations of wavelengths with position were used to assess the precision of calibration achievable. Then, an analysis method first used in studies with the CHASE experiment, was applied to the new observations. The behaviour of the intensities of lines from like ions over the twelve positions, called `position patterns', were used to distinguish probable emitters of weaker lines and extend the identifications. Spectral line widths and expected multiplet intensities were examined to identify lines and probable blends. The product of the study is a table which includes all clearly observed emission lines, their measured wavelengths, widths and count rates. Adopted laboratory wavelengths, ion and transition designations are also presented for identified lines. The table has an estimate of the uncertainty of the count rates based on a statistical analysis of the variability of each line. A marked spectrum is also provided. Title: Multi-wavelength observations of the onset phase of a coronal mass ejection Authors: Innes, D. E.; Inhester, B.; Srivastava, N.; Brekke, P.; Harrison, R. A.; Matthews, S. A.; Noëns, J. C.; Schmieder, B.; Thompson, B. J. Bibcode: 1999SoPh..186..337I Altcode: The structure and dynamics of the initial phases of a coronal mass ejection (CME) seen in soft X-ray, extreme ultraviolet and optical emission are described. The event occurred on the SW limb of the Sun in active region AR 8026 on 9 April 1997. Just prior to the CME there was a class C1.5 flare. Images taken with the Extreme Ultraviolet Imaging Telescope (EIT) reveal the emergence of a candle-flame shaped extreme ultraviolet (EUV) cavity at the time of the flare. Yohkoh images, taken about 15 min later, show that this cavity is filled with hot X-ray emitting gas. It is most likely that this is the site of the flare. Almost simultaneous to the flare, an Hα surge or small filament eruption occurs about 50 arc sec northwards along the limb from the EUV cavity. At both the site of the core of the hot, EUV cavity and the filament ejection are X-ray jets. These jets seem to be connected by hot loops near their bases. Both jets disappear within a few minutes of one another. Title: Simulations of small-scale explosive events on the Sun Authors: Innes, D. E.; Tóth, G. Bibcode: 1999SoPh..185..127I Altcode: 1999astro.ph..1342I Small-scale explosive events or microflares occur throughout the chromospheric network of the Sun. They are seen as sudden bursts of highly Doppler-shifted spectral lines of ions formed at temperatures in the range 2×104−5×105 K. They tend to occur near regions of cancelling photospheric magnetic fields and are thought to be directly associated with magnetic field reconnection. Recent observations have revealed that they have a bi-directional jet structure reminiscent of Petschek reconnection. In this paper compressible MHD simulations of the evolution of a current sheet to a steady Petschek, jet-like configuration are computed using the Versatile Advection Code. We obtain velocity profiles that can be compared with recent ultraviolet line-profile observations. By choosing initial conditions representative of magnetic loops in the solar corona and chromosphere, it is possible to explain the fact that jets flowing outward into the corona are more extended and appear before jets flowing towards the chromosphere. This model can reproduce the high Doppler-shifted components of the line profiles, but the brightening at low velocities, near the center of the bi-directional jet, cannot be explained by this simple MHD model. Title: The evolution of solar bipolar jets observed in the UV by SUMER on SOHO. Authors: Mendoza-Torres, J. E.; Wilhelm, K.; Innes, D. E.; Curd, W.; Kliem, B.; Brekke, P. Bibcode: 1998larm.confE..17M Altcode: Observations of bipolar jets made in the UV by SUMER onboard SOHO are presented. The observations were carried out in the interval 74.9-79.0 nm which contains some chromospheric and transition region lines. The theory predicts that under the conditions of the solar chromosphere the reconnection of magnetic lines accelerates plasma into two oppositely directed jets. In the chromosphere, as well as in other solar layers, different phenomena, where plasma acceleration take place, are observed. Of them the UV jets, observed by SUMER, represent one of the most clear evidences of the link between magnetic reconnection and plasma acceleration. The jets are clearly revealed by a considerably intensity increase and large doppler shifts of the line wings. It should be noted that the enhancement of only one wing also occurs and that the central component of the line also undergoes velocity shifts and amplitude enhancement. The behavior of the wings found in this work is consistent with results obtained for other events (Innes et al. 1997) namely: 1)The wings are observed during few minutes 2) The doppler velocities of the line wings (red and blue) are similar to each other and typical values are of the order of 100 km/sec, 3) In general, the blue component is more long-lived than the red one, 4)the red component is, in general, more intense than the blue one. In this work, an analysis of the velocities of the three spectral components (the central and the wings) as a function of the location on the slit, used for the observations, is also done. The ratios of two OV (density sensitive) and two OIV (temperature sensitive) lines, whose wavelengths are in the observed range, are also analyzed. An important result is that these parameters show gradients along the slit. An analysis of the spatial distributions and the correlations between them is done. A discussion of these results, in relation with the appearance and the evolution of the jets, will be done. Title: Ultraviolet Observations of a Dynamic Event in the Solar Corona Authors: Innes, D. E.; Curdt, W.; Dwivedi, B. N.; Wilhelm, K. Bibcode: 1998SoPh..181..103I Altcode: The Solar Ultraviolet Measurements of Emitted Radiation instrument (SUMER) observations show high Doppler shifts and temporal variations in profiles of ultraviolet lines from low temperature gas in the corona above the active region NOAA 7974. The profiles indicate ≈ 100 km s-1 flows coming from an almost stationary source that appears bright in the lines of N III and Si III. The variations in line-of-sight velocities and intensities suggest small knots of cooling plasma emanating from a small region high in the corona. A few arc sec sunward of the region where the cool flows are seen is an elongated region of enhanced higher temperature, low velocity Ne VI and Mg VI line emission. Title: SUMER observations of bi-directional flows in coronal plasmas Authors: Curdt, W.; Innes, D. E.; Wilhelm, K. Bibcode: 1998ESASP.421..123C Altcode: 1998sjcp.conf..123C No abstract at ADS Title: Sunspot Oscillations from SUMER Spectra Authors: Rendtel, J.; Staude, J.; Innes, D.; Wilhelm, K.; Gurman, J. B. Bibcode: 1998ESASP.417..277R Altcode: 1998cesh.conf..277R No abstract at ADS Title: Surges and filaments in active regions during SOHO campaigns Authors: Schmieder, B.; Deng, Y.; Rudawy, P.; Nitta, N.; Mandrini, C. H.; Fletcher, L.; Martens, P.; Innes, D.; Young, P.; Mason, H. Bibcode: 1998ESASP.421..323S Altcode: 1998sjcp.conf..323S No abstract at ADS Title: Oscillations in a Sunspot Transition Region Observed with SOHO Authors: Staude, J.; Rendtel, J.; Innes, D.; Wilhelm, K.; Gurman, J. B. Bibcode: 1998ESASP.418..651S Altcode: 1998soho....6..651S Measurements of oscillations in the chromosphere-corona transition region (TR) above sunspots are of fundamental importance for investigating sunspot structure and dynamics; for instance, resonator models of magneto-atmospheric waves and their non-adiabatic behavior can be tested in this way (Staude et al., 1985). UV spectroscopic data obtained with the SUMER spectrograph aboard SOHO have been analyzed to detect such oscillations. The longest time series was obtained on August 29, 1996, between 09:08 UT and 13:31 UT. During this period, scans were made over the active region NOAA 7986 in the wavelength bands around 770.4 AA (Ne VIII line, formed at T ~6 times 105 K) and 1548.1 AA (C IV line, T ~7 times 104 dots 1.3 times 105 K). The large dominating sunspot of this active region was close to the disk centre. Simultaneous observations with the Normal Incidence Spectrometer of CDS aboard SOHO have shown, that the spot had a bright EUV plume at TR temperatures (Maltby et al., 1998). For compensating possible instrumental and exposure effects, we extract background information from each image. A preliminary data analysis indicates intensity oscillations in the 2-minute range (at 7.4 dots 7.7 mHz) in both spectral lines and a slow temporal decrease of oscillatory power in the Ne VIII line, but an increase in the C IV line. These results hint at a non-adiabatic behavior of the oscillations and a slow cooling of the emitting sunspot plume region. Further supplementary observations of the active region NOAA 7986 are from EIT aboard SOHO (in the Fe IX/X lines at 171 AA --- T ~1.3 times 106 K --- a time series of 2 hours has been obtained simultaneous to the first part of the SUMER series, moreover, single high-resolution pictures in 4 UV lines exist) as well as from the magnetograph of the Einsteinturm observatory at Potsdam showing a rather complex polarity distribution. It is planned to extend the study towards velocity variations and to correlations between the oscillations in the two SUMER lines. Furthermore, correlations will be investigated towards the EIT time series. Title: CESRA Workshop on Coronal Explosive Events Authors: Curdt, W.; Innes, D. E. Bibcode: 1998cee..workE...6C Altcode: Recently, the increasing observational evidence for small-scale transient solar phenomena has intensified the discussion about the mechanism behind these events and their potential relevance for outstanding questions of solar physics. The spectrometers on SOHO - CDS, the Coronal Diagnostic Spectrometer and SUMER, the Solar Ultraviolet Measurements of Emitted Radiation instrument - have returned a wealth of observations of small-scale transient events. Small-scale transient brightenings, mostly in combination with high velocity Doppler flows are occuring continually throughout the quiet Sun (Dere 1991, Innes 1997, Harrison 1997). Similar phenomena have been seen in off limb observations higher in the corona (Curdt 1997). Some of these observations are presented here, and typical parameters and common characteristics in terms of morphology and temporal evolution of the phenomena are described. Many groups suggested that magnetic field cancellations convert magnetic energy into kinetic and thermal plasma energy leading to bursts of high velocity plasma ejected from small sites (e.g. Innes 1998). A joint observation was performed by SUMER and the MDI instrument, the Michelson Doppler Interferometer, which can observe the magnetic field. Both instruments observed the same plasma volume at the same time. The results are presented here. There is clear observational evidence that small-scale transient events are linked to magnetic field variations in support of the flux-cancellation model. Title: Bursts of Explosive Events in the Solar Network Authors: Innes, D. E.; Brekke, P.; Germerott, D.; Wilhelm, K. Bibcode: 1997SoPh..175..341I Altcode: Observations of the quiet-Sun network in the UV emission line Siiv 1393 Å over a time period of two hours are presented. Bursts of explosive events, highly Doppler-shifted emission, seem to be sporadically emitted from the brighter regions of the network lanes. Individual events have typical lifetimes of ≈ 1-6 min and come in bursts of up to 30 min. The most spectacular burst in this dataset, shown in the accompanying movie, lasts ≈ 30 min and shows a wide variety of line profiles with both red and blue shifts ≈180 km s1. There appears to be no characteristic form or evolutionary pattern to the line profiles in either the individual events or series of events. There are about twice as many blue shifts as red shifts. Title: Bi-directional plasma jets produced by magnetic reconnection on the Sun Authors: Innes, D. E.; Inhester, B.; Axford, W. I.; Wilhelm, K. Bibcode: 1997Natur.386..811I Altcode: Magnetic reconnection, the process by which magnetic lines of force break and rejoin into a lower-energy configuration, is considered to be the fundamental process by which magnetic energy is converted into plasma kinetic energy1. The Sun has a large reservoir of magnetic energy, and the energy released by magnetic reconnection has been invoked to explain both large-scale events, such as solar flares2,3 and coronal mass ejections4, and small-scale phenomena, such as the coronal and chromospheric microflares that probably heat and accelerate the solar wind5,6. But the observational evidence for reconnection is largely indirect, resting on observations of variations in solar X-ray morphology and sudden changes in the magnetic topology7,8, and on the apparent association between some small-scale dynamic events and magnetic bipoles9,10. Here we report ultraviolet observations of explosive events in the solar chromosophere that reveal the presence of bi-directional plasma jets ejected from small sites above the solar surface. The structure of these jets evolves in the manner predicted by theoretical models of magnetic reconnection11,12, thereby lending strong support to the view that reconnection is the fundamental process for accelerating plasma on the Sun. Title: EUV Observations of Bi-Directional Jets in the Solar Corona Authors: Curdt, W.; Dwivedi, B. N.; Innes, D. E. Bibcode: 1997ESASP.404..303C Altcode: 1997cswn.conf..303C No abstract at ADS Title: First Observations SUMER - VTT, SI IV - CA II K Authors: Balthasar, H.; von Uexkull, M.; Innes, D.; Gigas, D.; Wilhelm, K. Bibcode: 1997ASPC..118..315B Altcode: 1997fasp.conf..315B We tried to do a comparison of Ca II K (393.3 nm) filtergrams obtained at the Vacuum Tower Telescope on Tenerife with spectra in the line Si IV 139.4 nm obtained simultaneously with the SUMER telescope on the SOHO-spacecraft. Some bright features can be well identified in both observations. We compare temporal changes of the brightness for these common features. Title: A 2D Numerical Study of Explosive Events in the Solar Atmosphere Authors: Jin, S. -P.; Inhester, B.; Innes, D. Bibcode: 1996SoPh..168..279J Altcode: Two-dimensional (2D) compressible magnetohydrodynamic simulations are performed to explore the idea that the asymmetric reconnection between newly emerging intranetwork magnetic field flux and pre-existing network flux causes the explosive events in the solar atmosphere. The dependence of the reconnection rate as a function of time on the density and temperature of the emerging flux are investigated. For a Lundquist number of Lu= 5000 we find that the tearing mode instability can lead to the formation and growth of small magnetic islands. Depending on the temperature and density ratio of the emerging plasma, the magnetic island can be lifted upward and convected out of the top boundary, or is suppressed downward and convected out of the top boundary, or is suppressed downward nad submerged below the bottom boundary. The motions of the magnetic islands with different direction are accompanied respectively with upward or downward high velocity flow which might be associated with the red- and blue-shifted components detected in the explosive events. Title: Models of Explosive Events Authors: Innes, D.; Jin, S. -P.; Inhester, B. Bibcode: 1996ApL&C..34..127I Altcode: No abstract at ADS Title: Three-Dimensional Modelling of EUVE Observations of the Io Plasma Torus Authors: Thomas, N.; Innes, D. E.; Lieu, R. Bibcode: 1996aeu..conf..457T Altcode: 1996IAUCo.152..457T No abstract at ADS Title: Characteristics and Riemann invariants for multi-ion plasmas in the presence of Alfvén waves Authors: Ratkiewicz, R.; Innes, D. E.; McKenzie, J. F. Bibcode: 1994JPlPh..52..297R Altcode: In this paper the characteristics for a single- and a bi-ion plasma in the presence of Alfvén waves are given. In the single-ion case, the analysis is extended to the situation where Alfvén waves saturate and dissipatively heat the plasma. When there is no dissipation, there are three sound waves and one entropy wave in the single-ion plasma. Each sound wave is associated with two Riemann invariants relating the changes in density and wave pressure to changes in the flow. In the case when the Alfvén waves saturate and heat the plasma, there are two sound waves and one modified entropy sound wave. Each wave is associated with two Riemann invariants relating changes in density and entropy to changes in the flow. The analysis for the bi-ion plasma is simplified to very sub-Alfvénic flows. In this case the Alfvén waves behave like another plasma component, and both the electric and Alfvén wave forces have the same structure. The system possesses two entropy waves and four sound waves. Each sound wave is associated with two Riemann invariants relating changes in density and flow velocity along the characteristic curves. Title: Catastrophic Cooling Diagnostics Authors: Innes, D. E. Bibcode: 1994Ap&SS.216..311I Altcode: This paper presents models of optical emission line features that characterise catastrophic cooling in radiative shocks. The computations are based on a 1-D magnetohydrodynamic model. Runaway cooling results in the formation of secondary shocks which travel through the previously shocked cooling layer. Several filaments of emission with specific properties and spectral signatures are produced. Title: Dynamics and spectra of magnetically cushioned radiative shocks Authors: Innes, D. E. Bibcode: 1992A&A...256..660I Altcode: This paper investigates the effects of magnetic fields on the evolution and spectral appearance of unstable radiative shocks. In this work, a detailed treatment of the ionization evolution, the photoionizing radiation and its transfer through the gas, is coupled to a 1D MHD scheme. The cushioning effect of the magnetic field on the formation of secondary shocks in the postshock cooling flow is clearly demonstrated by our results. The field strengths required to suppress shock formation are at least a factor two greater than predicted by linear stability analysis. Thus a field strength, transverse to the flow, of 9 micro-G is required to suppress shock formation behind a 175 km/s shock, travelling into a density of 1/cu cm. Inclusion of the magnetic field results in realistic pressures and densities in the cool postshock photoionized shell. This allows us to follow the dynamics of the evolving photoionization zone where much of the low excitation optical radiation is emitted. We discuss characteristic features in the spectra of unstable shocks and describe spectral diagnostics, based on the optical and UV line ratios and spatial intensity distributions, for their identification. Title: Line Radiation from Stationary Accretion Disks Authors: Adam, J.; Innes, D. E.; Shaviv, G.; Störzer, H.; Wehrse, R. Bibcode: 1989ASIC..290..403A Altcode: 1989tad..conf..403A No abstract at ADS Title: Interpretation Difficulties of Supernova Remnant Shock Spectra Authors: Innes, D. E. Bibcode: 1988LNP...316...74I Altcode: 1988sstb.conf...74I Emission line ratios of unsteady radiative shocks are shown to be indistinguishable from those of steady shocks with velocities about 100 km s-1, although shock parameters such as velocity and preshock density are significantly different. If the shocks are radiatively unstable, then it may be possible to observe time variations of line ratios in SNRs over a period of a few years. Title: Dynamical models of radiative shocks. III - Spectra Authors: Innes, D. E.; Giddings, J. R.; Falle, S. A. E. G. Bibcode: 1987MNRAS.227.1021I Altcode: The authors have investigated the spectral characteristics of steady and unsteady radiative shock models in the context of Supernova Remnants (SNRs). By means of detailed, multi-level radiative transfer calculations, they have generated emission and absorption line profiles for selected shock models. Geometrical effects are simulated by forming the plane models into a thin spherical shell, which is then observed along different lines-of-sight. The authors show that the nature of unsteady shocks can best be studied through observations of absorption and emission line profiles along lines-of-sight near to the centre of the SNR. Also, they show why emission maps in the light of optically thick transitions should not exhibit the bright filaments associated with optically thin lines. Title: Dynamical models of radiative shocks. II - Unsteady shocks Authors: Innes, D. E.; Giddings, J. R.; Falle, S. A. E. G. Bibcode: 1987MNRAS.226...67I Altcode: This paper describes the results of numerical calculations of the flow behind plane-parallel radiative shocks driven by a constant pressure piston. The authors have included both time-dependent dynamics and a detailed calculation of the ionization state and the radiation field. They find that shocks with speeds greater than or equal to 150 km s-1 are unstable in the sense that a small upstream perturbation triggers large and persistent variations in the shock velocity. This has a dramatic effect on the emission-line ratios and suggests that steady models of shock excited emission are of little use in such cases. Title: Steady stellar jets. Authors: Falle, S. A. E. G.; Innes, D. E.; Wilson, M. J. Bibcode: 1987MNRAS.225..741F Altcode: This paper contains some results of axisymmetric numerical calculations of the shock structures in steady supersonic jets in which there is significant radiative cooling. It is found that the regularly spaced shock cells found in adiabatic jets still occur and that cooling can by itself induce shocks if it is fast enough. The forbidden O I line emission from such jets is calculated and compared to that seen in stellar jets. The pattern of emission is very similar to that observed, which suggests that a number of the features of stellar jets can be understood in this way. Title: Dynamical models of radiative shocks. I - Steady shocks Authors: Innes, D. E.; Giddings, J. R.; Falle, S. A. E. G. Bibcode: 1987MNRAS.224..179I Altcode: The ionization structure and line emission behind a steady radiative shock are calculated with a consistent treatment of the radiation field and the shock precursor. The results agree well with those of previous authors, except that the Hβ intensity is about twice that found in earlier calculations. Only relatively low velocity shocks are considered, since, as will be shown in later papers, high velocity shocks are unstable and unlikely to be steady. Title: A jet model of Herbig-Haro objects. Authors: Wilson, M. J.; Falle, S. A. E. G.; Innes, D. E. Bibcode: 1987IAUS..122..193W Altcode: The authors present results of steady jet calculations in which the cooling and compression behind internal shocks leads to optical emission with an intensity pattern similar to the regular well-aligned emission knots characteristic of stellar jets. Title: Theoretical models for non-steady radiative shocks in supernova remnants. Authors: Innes, Davina E. Bibcode: 1986PhDT........13I Altcode: No abstract at ADS Title: Gas Dynamic Calculations of Non-Steady Radiative Shocks : Variations in Emission Line Ratios Authors: Innes, D. E.; Giddings, J. R.; Falle, S. A. E. G. Bibcode: 1986mone.work..153I Altcode: Coupled gas-dynamic and ionization calculations for the evolution of radiative shocks moving into a region of enhanced density demonstrate the importance of secondary shock formation on their structure and on observable emission-line ratios. Title: Theoretical Models for Non-steady Radiative Shocks in Supernova Remnants Authors: Innes, Davina E. Bibcode: 1985PhDT........14I Altcode: Earlier numerical calculations have demonstrated that the radiative shell of a supernova remnant (SNR) in the post-adiabatic phase is unstable and continues to develop secondary shocks until the mean velocity has dropped below 100 km/s. In the past, theoretical models have either calculated the detailed ionization of 'steady' shocks or the evolution of shocks without accounting for the effects of time-dependent ionization on cooling. The work presented in this Thesis provides the first numerical models of detailed, time-dependent ionization coupled to the gas dynamical evolution of non-steady radiative shocks. The aim of this work has been to investigate the stability of 'steady', plane-parallel shocks. This has been done for a range of shock models, with initial velocities 100 - 200 km/s, by following their evolution as they move into a medium containing a single, small density perturbation. It is shown that shocks with velocities > 150 km/s are unstable and subject to the formation of secondary shocks. During their evolution the shock velocity and structure undergo gross variations. At high initial shock velocities (175 - 200 km/s) strong secondary shocks are produced, and although the evolution is punctuated by the formation and destruction of these shocks, the model structure is chaotic: it depends on the history of changes in dynamics and ionization. At 150 km/s weaker shocks are formed, and the structure evolves through a series of cycles. These structural changes result in dramatic variations in emission line ratios. The extent of the variation, particularly for faster shocks, is such that classical line ratio diagnostics (e.g. [oIIIfPIlI) are rendered useless for the determination of either the initial or the instantaneous shock velocity. Detailed line transfer calculations have been used to show that the models with multiple shocks have complex C IV absorption and emission profiles. The structure of the latter being considerably more complicated due to scattering effects. The results from this work have important implications for the analysis of filamentary structure in SNRs. Title: Non-steady radiative shocks Authors: Innes, D. E.; Giddings, J. R.; Falle, S. A. E. G. Bibcode: 1985cgd..conf..143I Altcode: Earlier work has shown that supernova shocks entering the radiative phase go through a period of unstable (catastrophic) cooling, in which one or more secondary shocks are produced. It has been demonstrated that the cooling instability is fundamental and not related to the way in which the shocks are formed. this has been done by means of detailed hydrodynamical and ionization calculations for a 'steady' 200 km/s shock moving into a medium containing a small (but plausible) density perturbation. It is found that even small perturbations are capable of setting the shock into a phase of catastrophic cooling. The results reinforce the conclusion that the 'steady' flow assumption is incorrect for radiative shock models with velocities greater than about 150 km./s. Title: Are we in an old superbubble? Authors: Innes, D. E.; Hartquist, T. W. Bibcode: 1984MNRAS.209....7I Altcode: Using a simple model for the thermal properties of very old supernova remnants and superbubbles, it is found that the observed background soft X-ray and extreme ultraviolet spectra can be produced by a superbubble formed by the injection of about 1052 erg into the interstellar medium surrounding the Earth roughly 4×106 yr ago. Title: Investigation of the Remnant Shell of the North Polar Spur Supernova Authors: Innes, D. Bibcode: 1984iue..prop.1961I Altcode: No abstract at ADS Title: Carbon Monoxide J=3-2 and J=2-1 Observations of Molecular Clouds. Authors: Huggins, P. J.; Phillpis, T. G.; Neugebauer, G.; Werner, M. W.; Wannier, P. G.; Innes, D.; Scoville, N. Z. Bibcode: 1977BAAS....9..353H Altcode: No abstract at ADS