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Author name code: innes
ADS astronomy entries on 2022-09-14
author:"Innes, Davina E."

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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.
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.

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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.
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.

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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.
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 &gt;
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.

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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.
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.

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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.
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.

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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.
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.

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Title: Association of Impulsive Solar Energetic Particle Events With
Large-Scale Coronal Waves
Authors: Bucik, R.; Innes, D.; Mason, G. M.; Wiedenbeck, M. E.
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.

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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.
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.

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Title: Understanding IRIS Observations of Explosive Events in Terms
of Magnetic Reconnection Mechanisms
Authors: Guo, L.; Innes, D.; Huang, Y. M.; Bhattacharjee, A.
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.

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Title: Undercover EUV Solar Jets Observed by the Interface Region
Imaging Spectrograph
Authors: Chen, N. -H.; Innes, D. E.
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%.

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Title: Observations of solar X-ray and EUV jets and their related
phenomena
Authors: Innes, D. E.; Bučík, R.; Guo, L. -J.; Nitta, N.
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).

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Title: Relationship between supergranulation flows, magnetic
cancellation and network flares
Authors: Attie, R.; Innes, D. E.; Solanki, S. K.; Glassmeier, K. H.
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.

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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.
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.

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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
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.

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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
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.

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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
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.

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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.
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
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.
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
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.
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.
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.
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.
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 \&amp; 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 $&gt;10^{27}$ 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.
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.
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.
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.
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.
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
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.
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
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.
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.
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 <A
href="http://www.aanda.org/10.1051/0004-6361/201424552/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Persistent Energetic Ion Outbursts from the Sun
Authors: Bucik, R.; Innes, D.; Mason, G. M.
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.
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.
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.
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.
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.
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.
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 <A
href="http://www.aanda.org/10.1051/0004-6361/201424432/olm">http://www.aanda.org</A>

---------------------------------------------------------
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.
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
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.
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.
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
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.
2014ApJ...786...71B Altcode: 2014arXiv1403.4856B
We study the origin of 3He-rich solar energetic particles
(&lt;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
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
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
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
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
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.
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.
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.
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.
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.
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.
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.
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
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.
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.
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.
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&amp;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.
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.
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 <A href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
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.
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
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
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.
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.
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.
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 <A href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
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
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.
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.
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.
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 <A
href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
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.
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.
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.
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 <A href="http://www.aanda.org">http://www.aanda.org</A> and at <A
href="http://www.mps.mpg.de/data/outgoing/tothova/movie.gif">http://www.mps.mpg.de/data/outgoing/tothova/movie.gif</A>

---------------------------------------------------------
Title: The source regions of SEPs observed by SDO in Aug 2010
Authors: Innes, Davina; Park, Jinhye; Bucik, Radoslav
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.

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Title: STEREO quadrature observations of coronal dimming at the
onset of mini-CMEs
Authors: Innes, D. E.; McIntosh, S. W.; Pietarila, A.
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 <A href="http://www.aanda.org">http://www.aanda.org</A>

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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.
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 <A href="http://www.aanda.org">http://www.aanda.org</A>

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Title: STEREO quadrature observations of mass flows in prominences
Authors: Innes, Davina; McIntosh, Scott; Pietarila, Anna
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.

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Title: Impusive heating of bright points observed by EIS and SUMER
Authors: Kamio, Suguru; Curdt, Werner; Teriaca, Luca; Innes, Davina
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.

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Title: STEREO quadrature observations of coronal dimming at the
onset of mini-CMEs
Authors: Innes, Davina; McIntosh, Scott
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.

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Title: Soft X-ray Emission in the Quiet Sun Related to Magnetic
Reconnection
Authors: Attie, Raphael; Innes, Davina; Potts, Hugh
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.

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Title: Quiet Sun mini-coronal mass ejections activated by
supergranular flows
Authors: Innes, D. E.; Genetelli, A.; Attie, R.; Potts, H. E.
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

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Title: Evidence of photospheric vortex flows at supergranular
junctions observed by FG/SOT (Hinode)
Authors: Attie, R.; Innes, D. E.; Potts, H. E.
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).

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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.
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.

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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.
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.

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Title: Explosive Event in the Quiet Sun Seen by XRT-EIS and SUMER
Authors: Attie, R.; Innes, D.
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.
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.

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Title: High Speed Plasma Acceleration and Loop Oscillations at
Flare Onset
Authors: Tothova, D.; Innes, D.
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.

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Title: Quiet Sun Mini-CMEs Observed in STEREO
Authors: Innes, D.; Genetelli, A.; Attie, R.; Potts, H.
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.

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Title: SOHO/SUMER observations of prominence oscillation before
eruption
Authors: Chen, P. F.; Innes, D. E.; Solanki, S. K.
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.

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Title: SUMER-Hinode observations of microflares: excitation of
molecular hydrogen
Authors: Innes, D. E.
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
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.

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Title: Coronal Heating by Small Scale Eruptive Events on Quiet sun
Investigated By Coaligned Observations From Soho and Hinode
Authors: Attie, R.; Innes, D.
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.

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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.
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.

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Title: High Velocity Doppler Shift Observations of 10 MK Flare Plasma
Authors: Innes, D. E.; Wang, T. J.
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.

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Title: Determination of the Coronal Magnetic Field from Hot-Loop
Oscillations Observed by SUMER and SXT
Authors: Wang, Tongjiang; Innes, Davina E.; Qiu, Jiong
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.

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Title: Nanoflare model of emission line radiance distributions in
active region coronae
Authors: Safari, H.; Innes, D. E.; Solanki, S. K.; Pauluhn, A.
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.

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Title: Wavelet-based method for coronal loop oscillations analysis
Authors: Tothova, D.; Innes, D. E.; Solanki, S. K.
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.
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 &gt; 6 MK by soft X-ray microflares.

---------------------------------------------------------
Title: Microflares and Loop Oscillations
Authors: Innes, D. E.; Wang, T. J.; Solanki, S. K.; Tothova, D.
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.
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.
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.
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.
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.
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.
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.
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 &amp;
Peter (2004, A&amp;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.
2004ESASP.575..465B Altcode: 2004soho...15..465B
No abstract at ADS

---------------------------------------------------------
Title: SUMER Observations of Active Region Loop Dynamics
Authors: Innes, D.; Wang, T.
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.
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.
2004ESASP.547..297N Altcode: 2004soho...13..297N
No abstract at ADS

---------------------------------------------------------
Title: Transition Region Dynamics
Authors: Innes, D. E.
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.
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.
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
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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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 &gt; 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.
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.
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 (&gt;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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
1989ASIC..290..403A Altcode: 1989tad..conf..403A
No abstract at ADS

---------------------------------------------------------
Title: Interpretation Difficulties of Supernova Remnant Shock Spectra
Authors: Innes, D. E.
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.
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.
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.
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.

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Title: Dynamical models of radiative shocks. I - Steady shocks
Authors: Innes, D. E.; Giddings, J. R.; Falle, S. A. E. G.
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.

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Title: A jet model of Herbig-Haro objects.
Authors: Wilson, M. J.; Falle, S. A. E. G.; Innes, D. E.
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.

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Title: Theoretical models for non-steady radiative shocks in
supernova remnants.
Authors: Innes, Davina E.
1986PhDT........13I Altcode:
No abstract at ADS

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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.
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.

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Title: Theoretical Models for Non-steady Radiative Shocks in
Supernova Remnants
Authors: Innes, Davina E.
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 &gt; 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.

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Title: Non-steady radiative shocks
Authors: Innes, D. E.; Giddings, J. R.; Falle, S. A. E. G.
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.

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Title: Are we in an old superbubble?
Authors: Innes, D. E.; Hartquist, T. W.
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.

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Title: Investigation of the Remnant Shell of the North Polar Spur
Supernova
Authors: Innes, D.
1984iue..prop.1961I Altcode:
No abstract at ADS

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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.
1977BAAS....9..353H Altcode:
No abstract at ADS