schmieder

explanation blue bibcodes open ADS page with paths to full text

Author name code: schmieder
ADS astronomy entries on 2022-09-14
=author:"Schmieder, B." OR =author:"Schmieder, Brigitte"

---------------------------------------------------------
Title: Solar jets observed with the Interface Region Imaging
Spectrograph (IRIS)
Authors: Schmieder, Brigitte; Joshi, Reetika; Chandra, Ramesh
2022AdSpR..70.1580S Altcode: 2021arXiv211109002S
Solar jets are impulsive, collimated plasma ejections that are
triggered by magnetic reconnection. They are observed for many decades
in various temperatures and wavelengths, therefore their kinematic
characteristics, such as velocity and recurrence, have been extensively
studied. Nevertheless, the high spatial resolution of the Interface
Region Imaging Spectrograph (IRIS) launched in 2013 allowed us to
make a step forward in the understanding of the relationship between
surges and hot jets. In this paper we report on several results of
recent studies of jets observed by IRIS. Cool and hot plasma have
been detected with ejections of cool blobs having a speed reaching
300 km s-1 during the impulsive phase of jet formation
and slow velocity surges surrounding hot jets after the reconnection
phase. Plasma characteristics of solar jets, such as the emission
measure, temperature, and density have been quantified. A multi-layer
atmosphere at the reconnection site based on observed IRIS spectra has
been proposed. IRIS evidenced bidirectional flows at reconnection sites,
and tilt along the spectra which were interpreted as the signature of
twist in jets. The search of possible sites for reconnection could be
achieved by the analysis of magnetic topology. Combining Solar Dynamics
Observatory/Helioseismic Magnetic Imager (SDO/HMI) vector magnetograms
and IRIS observations, it was found that reconnection site could be
located at null points in the corona as well as in bald patch regions
low in the photosphere. In one case study a magnetic sketch could
explain the initiation of a jet starting in a bald patch transformed
to a current sheet in a dynamical way, and the transfer of twist from
a flux rope to the jet during the magnetic reconnection process.

---------------------------------------------------------
Title: Over-expansion of coronal mass ejections modelled using 3D
MHD EUHFORIA simulations
Authors: Verbeke, Christine; Schmieder, Brigitte; Démoulin, Pascal;
Dasso, Sergio; Grison, Benjamin; Samara, Evangelia; Scolini, Camilla;
Poedts, Stefaan
2022AdSpR..70.1663V Altcode: 2022arXiv220703168V
Coronal mass ejections (CMEs) are large scale eruptions observed close
to the Sun. They are travelling through the heliosphere and possibly
interacting with the Earth environment creating interruptions or even
damaging new technology instruments. Most of the time their physical
conditions (velocity, density, pressure) are only measured in situ
at one point in space, with no possibility to have information on
the variation of these parameters during their journey from Sun to
Earth. Our aim is to understand the evolution of internal physical
parameters of a set of three particular fast halo CMEs. These
CMEs were launched between 15 and 18 July 2002. Surprisingly, the
related interplanetary CMEs (ICMEs), observed near Earth, have a low,
and in one case even very low, plasma density. We use the EUropean
Heliosphere FORecasting Information Asset (EUHFORIA) model to simulate
the propagation of the CMEs in the background solar wind by placing
virtual spacecraft along the Sun--Earth line. We set up the initial
conditions at 0.1 au, first with a cone model and then with a linear
force free spheromak model. A relatively good agreement between
simulation results and observations concerning the speed, density and
arrival times of the ICMEs is obtained by adapting the initial CME
parameters. In particular, this is achieved by increasing the initial
magnetic pressure so that a fast expansion is induced in the inner
heliosphere. This implied the develop First, we show that a magnetic
configuration with an out of force balance close to the Sun mitigates
the EUHFORIA assumptions related to an initial uniform velocity. Second,
the over-expansion of the ejected magnetic configuration in the inner
heliosphere is one plausible origin for the low density observed
in some ICMEs at 1 au. The in situ observed very low density has a
possible coronal origin of fast expansion for two of the three ICMEs.

---------------------------------------------------------
Title: Prominence oscillations activated by an EUV wave
Authors: Devi, Pooja; Chandra, Ramesh; Joshi, Reetika; Chen, P. F.;
Schmieder, Brigitte; Uddin, Wahab; Moon, Yong-Jae
2022AdSpR..70.1592D Altcode: 2022arXiv220213147D
Prominence oscillations are one of interesting phenomena in the solar
atmosphere, which can be utilized to infer the embedded magnetic field
magnitude. We present here the transverse oscillations of two different
prominences located at the East solar limb on 2011 February 11 using the
multi-wavebands data of the Atmospheric Imaging Assembly (AIA) on-board
the Solar Dynamics Observatory (SDO) satellite. A prominence eruption
was observed towards the east direction with an average speed of ≈
275 km s-1. The eruption is fitted with the combination of
a linear and an exponential functions of time. An extreme ultraviolet
(EUV) wave event was associated with the prominence eruption. This EUV
wave triggered the oscillations of both prominences on the East limb. We
computed the period of each prominence using the wavelet analysis
method. The oscillation period varies from 14 to 22 min. The magnetic
field of the prominences was derived, which ranges from 14 to 20 G.

---------------------------------------------------------
Title: Preface: Magnetic flux ropes in solar environments
Authors: Mandrini, Cristina H.; Schmieder, Brigitte
2022AdSpR..70.1547M Altcode:
Magnetic flux bundles or ropes are the main building blocks forming
active regions. Their destabilization can lead to the most violent
events - flares, coronal mass ejections (CMEs), and energetic particle
events. After eruption, they are observed over a wide range of spatial
scales throughout the heliosphere. Specific configurations of these
structures can produce the strongest geomagnetic storms as they impact
the Earth's magnetosphere.

---------------------------------------------------------
Title: New Insight into UV Compact Bursts - Statistical Analysis of
IRIS Data
Authors: Berlicki, Arkadiusz; Heinzel, Petr; Schmieder, Brigitte;
Michalina Litwicka, M.
2022cosp...44.2532B Altcode:
UV small-scale brightenings have been frequently observed by IRIS in
both NUV and FUV channels. They appear as compact and intense, but short
lived bursts visible within the solar active regions. Some of them seem
to be closely connected with the well-known Ellerman bombs and so-called
IRIS bombs. Based on the IRIS observations of many compact bursts
obtained in chromospheric Mg II h and k lines, Mg II triplet and FUV
lines we present detailed statistical analysis of these phenomena. In
the work of Grubecka et al. (2016), five different compact bursts (CBs)
were selected and analysed in detail. NLTE semi-empirical models of
them were constructed based on their spectral characteristics in the
Mg II h and k lines. In addition, they were preliminarily categorised
into three types. In present work we extend previous analysis and
investigate statistical diversity of Mg II lines of UV bursts and
their visibility in FUV lines such as Si IV or C II. IRIS database
from 2013-2018 was searched for dense rasters of active and emerging
flux regions containing spectra in Mg II, C II and Si IV. A next step
was to reconstruct full rasters in which we were looking for compact
brightenings with size of the order of one arcsec. We found more than
two thousands CBs using criteria based on specific parameters of the
Mg II k line profile. In addition, we analysed also the emission of
Mg II UV triplet and some parameters of Si IV and C II lines. This
database allowed us to make a novel statistical analysis of all bursts
and we categorised them in previously defined three types, depending on
their Mg II line profiles shapes. We also investigated the correlations
between the emission of Mg II lines, "hotter" Si IV lines, and C II
lines in order to find which of these events are linked with IRIS bombs
(Peter et al. 2014). Finally, we analysed some observables of those
UV bursts, which can be defined as candidates for Ellerman bombs.

---------------------------------------------------------
Title: EUHFORIA modeling of slow CMEs with well-defined magnetic
signatures
Authors: Prete, Giuseppe; Carbone, Vincenzo; Wijsen, Nicolas; Poedts,
Stefaan; Schmieder, Brigitte; Esteban Niemela, Antonio; Lepreti, Fabio
2022cosp...44.2467P Altcode:
Coronal mass ejections (CMEs) are one of the main drivers of strong
space weather disturbances. The interaction between CMEs and the
Earth's magnetic field can cause a wide range of phenomena and the
magnetic configuration and orientation are key factors in determining
the geo-effectiveness of this type of events. Modeling these events
accurately is an ongoing challenge, and data-driven simulations
are a valuable operational and research tool, widely used by the
community. Using the 3D data-driven magneto-hydrodynamical (MHD)
heliospheric solar wind and CME evolution model EUHFORIA (European
Heliospheric FORecasting Information Asset), our aim is to model two
CME events previously investigated by Al-Haddad et al. (2018). These
particular events are characterized by propagation slow velocities
and well-organized magnetic field characteristics. We also explore
how these structures affect Earth, even in the absence of an ICME.

---------------------------------------------------------
Title: Fan-shaped jet close to a light bridge
Authors: Liu, Y.; Ruan, G. P.; Schmieder, B.; Masson, S.; Chen, Y.;
Su, J. T.; Wang, B.; Bai, X. Y.; Su, Y.; Cao, Wenda
2022arXiv220713246L Altcode:
On the Sun,jets in light bridges are frequently observed with
high-resolution instruments.The respective roles played by convection
and the magnetic field in triggering such jets are not yet clear.We
report a small fan-shaped jet along a LB observed by the 1.6m Goode
Solar Telescope(GST) with the TiO Broadband Filter Imager(BFI),the
Visible Imaging Spectrometer(VIS) in H{\alpha},and the Near-InfraRed
Imaging Spectropolarimeter(NIRIS),along with the Stokes parameters.The
high spatial and temporal resolution of those instruments allowed us to
analyze the features identified during the jet event.By constructing
the H{\alpha} Dopplergrams,we found that the plasma is first moving
upward,whereas during the second phase of the jet,the plasma is
flowing back.Working with time slice diagrams,we investigated
the propagation-projected speed of the fan and its bright base.The
fan-shaped jet developed within a few minutes,with diverging beams. At
its base,a bright point was slipping along the LB and ultimately invaded
the umbra of the sunspot.The H{\alpha} profiles of the bright points
enhanced the intensity in the wings, similarly to the case of Ellerman
bombs.Co-temporally,the extreme ultraviolet brightenings developed at
the front of the dark material jet and moved at the same speed as the
fan, leading us to propose that the fan-shaped jet material compressed
and heated the ambient plasma at its extremities in the corona.Our
multi-wavelength analysis indicates that the fan-shaped jet could result
from magnetic reconnection across the highly diverging field low in the
chromosphere,leading to an apparent slipping motion of the jet material
along the LB.However,we did not find any opposite magnetic polarity at
the jet base,as would typically be expected in such a configuration.We
therefore discuss other plausible physical mechanisms,based on waves
and convection, that may have triggered the event.

---------------------------------------------------------
Title: Coronal Seismology using the loops Oscillations triggered by
an EUV wave
Authors: Devi, Pooja; Awasthi, Arun Kumar; Chandra, Ramesh; Joshi,
Reetika; Schmieder, Brigitte
2022cosp...44.2489D Altcode:
Coronal seismology is widely utilized to infer the magnetic field
characteristics in the solar corona. Here, we investigate multiple
aspects of the eruptive activities that occurred in active region
NOAA 12287 during a GOES X1.0 class flare on October 28, 2021. This
includes a filament eruption and associated Extreme Ultraviolet
(EUV) wave. The erupted filament material apparently perturbed the
surrounding coronal structures. Interestingly, the associated EUV wave
triggered oscillations in several nearby loop systems. By probing
various oscillation characteristics e.g. time period, amplitude,
density, temperature, decay time etc., in the different loops systems,
we infer the characteristics of the magnetic field that essentially
surrounds the eruptive active region and compare it with the previous
observations and theories.

---------------------------------------------------------
Title: Solar prominence diagnostics from non-LTE modelling of Mgii
h&amp;k line profiles
Authors: Peat, Aaron; Labrosse, Nicolas; Barczynski, Krzysztof;
Schmieder, Brigitte
2022cosp...44.2542P Altcode:
We investigate a new method to obtain the plasma parameters of
solar prominences observed in the Mg II h&amp;k spectral lines by
comparing line profiles from the IRIS satellite to a bank of profiles
computed with a one-dimensional non-LTE radiative transfer code. The
prominence observations were carried out by the IRIS satellite on 19th
April 2018. Using a grid of 22933 one-dimensional non-LTE radiative
transfer models, some including a prominence-corona transition region
(PCTR), we are able to recover satisfactory matches in areas of the
prominence where single-line profiles are observed. Large values of
ionization degree are found by the procedure in areas where the line
of sight crosses mostly plasma from the PCTR, correlating with high
mean temperatures and correspondingly no H$\alpha$α emission. The
models were unable to recover satisfactory fits in the regions where
we see H$\alpha$ emission. This is due to the complex line shapes
manifesting from many unresolved independently moving threads. This
new method naturally returns information on how closely the observed
and computed profiles match, allowing the user to identify areas
where no satisfactory match between models and observations can
be obtained. The inclusion of the PCTR was found to be important,
as regions where satisfactory fits were found were more likely to
contain a model encompassing a PCTR.

---------------------------------------------------------
Title: Detection of Large Amplitude Oscillations in Solar Filaments
Caused by Jets
Authors: Joshi, Reetika; Chandra, Ramesh; Moreno-Insertis, . Fernando,
, Prof; Luna, Manuel; Schmieder, Brigitte
2022cosp...44.2417J Altcode:
Large amplitude oscillations (LAOs) are often observed in
prominences/filaments. Their origin has been associated with shock waves
or their interaction with jets and other eruptions. In this study,
we present two examples of LAOs due to the interaction of solar jets
with filaments on February 3-5 2015 and March 14 2015. The filament
eruption on March 14 was followed by a two step filament eruption along
with a CME which led to the strongest geomagnetic storm of Solar Cycle
24 on 17 March 2015. These LAOs are analysed by using time-distance
diagnostics. The detected LAOs have periods of around 60 minutes and
are damped after three oscillations. The observations are consistent
with the results of a recent developed theoretical model of jet and
filament/fluxrope interaction. The jets are associated with very
weak flares which did not initiate any EUV wave. The role of waves as
trigger of these oscillations can be discarded for these two events.

---------------------------------------------------------
Title: Formation of a flux rope inside an active region and its
failed eruption
Authors: Schmieder, Brigitte; Mandrini, Cristina H.; Chandra, Ramesh;
Mac Cormack, Cecilia; Joshi, Reetika; Cristiani, German
2022cosp...44.2418S Altcode:
In the standard flare model a flux rope is formed in an active
region. After reconnection of the magnetic field lines, the flux
rope rises and is expelled as a coronal mass ejection and ribbons are
formed at the feet of the reconnected loops. We observed such a case,
just more complicated because the region AR that we observed on May
9 2020 is a quadrupolar region . We explored the data of SDO/AIA,
SDO/HMI and the high resolution IRIS slit jaws . Therefore we analyzed
this case to understand the formation of the flux rope and its failed
eruption. The flux rope (filament) is formed by squeezed chromospheric
fibrils due flux cancellation and the eruption is also due to flux
cancellation. We conjecture that the failed eruption is due to the
magnetic strength of large scale loops overlaying the active region
and connecting with the edge of a coronal hole.

---------------------------------------------------------
Title: Analysis of the Evolution of a Multi-Ribbon Flare and Failed
Filament Eruption
Authors: Joshi, Reetika; Mandrini, Cristina H.; Chandra, Ramesh;
Schmieder, Brigitte; Cristiani, Germán D.; Mac Cormack, Cecilia;
Démoulin, Pascal; Cremades, Hebe
2022SoPh..297...81J Altcode: 2022arXiv220600531J
How filaments form and erupt are topics about which solar researchers
have wondered for more than a century and they are still open
to debate. We present observations of a filament formation, its
failed eruption, and the associated flare (SOL2019-05-09T05:51)
that occurred in active region (AR) 12740 using data from the
Solar Dynamics Observatory (SDO), the Solar-Terrestrial Relations
Observatory A (STEREO-A), the Interface Region Imaging Spectrograph
(IRIS) and the Learmonth Solar Observatory (LSO) of the National Solar
Observatory/Global Oscillation Network Group (NSO/GONG). AR 12740
was a decaying region formed by a very disperse following polarity
and a strong leading spot, surrounded by a highly dynamic zone where
moving magnetic features (MMFs) were seen constantly diverging from
the spot. Our analysis indicates that the filament was formed by the
convergence of fibrils at a location where magnetic flux cancellation
was observed. Furthermore, we conclude that its destabilisation was also
related to flux cancellation associated with the constant shuffling
of the MMFs. A two-ribbon flare occurred associated with the filament
eruption; however, because the large-scale magnetic configuration of
the AR was quadrupolar, two additional flare ribbons developed far from
the two main ones. We model the magnetic configuration of the AR using
a force-free field approach at the AR scale size. This local model is
complemented by a global potential-field source-surface one. Based on
the local model, we propose a scenario in which the filament failed
eruption and the flare are due to two reconnection processes, one
occurring below the erupting filament, leading to the two-ribbon flare,
and another one above it between the filament flux-rope configuration
and the large-scale closed loops. Our computation of the reconnected
magnetic flux added to the erupting flux rope, compared to that of
the large-scale field overlying it, allows us to conclude that the
latter was large enough to prevent the filament eruption. A similar
conjecture can be drawn from the computation of the magnetic tension
derived from the global field model.

---------------------------------------------------------
Title: Mini solar flare and jet due to small scale surface motions
Authors: Joshi, Reetika; Vilmer, Nicole; Chandra, Ramesh; Heinzel,
Petr; Bommier, Veronique; Schmieder, Brigitte; Aulanier, Guillaume;
Tomin, James
2022cosp...44.2535J Altcode:
Here we present the study of the fine structure and dynamics of the
plasma at a jet base forming a mini-flare between two emerging magnetic
fluxes (EMFs) observed with Interface Region Imaging Spectrograph
(IRIS) and the Solar Dynamics Observatory instruments. This active
region is an outcome of the collapse of two EMFs overlaid by arch
filament systems. We observed that, before the jet an extension of
the flux rope was present and a part of it was detached and formed
a small bipole with a bald patch region, which dynamically became
an X-current sheet over the dome of one EMF where the reconnection
took place. At the time in the site of reconnection, the IRIS C II,
Si IV, and Mg II line profiles present bi directional flows in a tiny
region. These types of spectra are typically associated with twist,
rotation, or the presence of plasma in helical structures. The tilt
observed in our spectra can be explained by the presence of a helical
structure at the jet base during the reconnection process due to a
transfer of the twist from a flux rope in the vicinity of the jet. We
also combined the observations of the Balmer continuum obtained with
the IRIS (spectra and SJIs 2832 Å). The calibrated Balmer continuum
was compared to non-local thermodynamic equilibrium radiative transfer
flare models and the radiated energy was estimated. Assuming thick
target HXR emission, we calculated the energy of the non thermal
electrons detected by the Fermi/GBM and compared it to the radiated
energy. The electron-beam flux estimated from Fermi/GBM between 10$
^{9}$ and 10$ ^{10}$ erg s$ ^{-1}$ cm$ ^{-2}$ is consistent with the
beam flux required in non-LTE radiative transfer models to obtain the
excess of Balmer continuum emission observed in this IRIS spectra. We
conclude that the bombardment of electrons could be in a region smaller
than the IRIS spatial resolution.

---------------------------------------------------------
Title: Impact of the solar activity cycle on the propagation of ICMEs
Authors: Perri, Barbara; Poedts, Stefaan; Schmieder, Brigitte
2022cosp...44.2444P Altcode:
The propagation of ICMEs in the heliosphere is influenced by a
great number of physical phenomena, related both to the internal
structure of the ICME but also to its interaction with the ambient
solar wind and heliospheric current sheet. The understanding of such
phenomena is crucial to be able to improve numerical modelling and
provide better space weather forecasts for the time of arrival of
perturbations at Earth. As individual structures of the solar wind such
as helmet streamers of high-speed streams have begun to be discussed,
the influence of the long-term variability of solar activity on
transient events is still not clear. Indeed, the solar magnetic field
is modulated by the 11-year dynamo cycle generated inside the Sun,
and then affecting the entire heliosphere structure by means of the
Parker spiral and its shaping of the solar corona. We know that there
are more transient events at maximum of activity and that they are
usually more intense, but the exact influence of solar activity on
their propagation remains to be discussed. It is becoming even more
important to assess these differences as solar cycle 25 is rising,
and thus many models calibrated on the minimum of activity between
cycles 24 and 25 may become less accurate. We perform a theoretical
study to try to answer these questions. We begin by trying to define
what is an average CME at 0.1 AU, using both observations and numerical
simulations. We choose a spheromak to model the CME, as it allows us
to explore also the magnetic interactions along its propagation. We
then use the heliospheric propagator EUHFORIA to inject the same CME
in two different background wind environments: the first corresponds
a very quiet minimum of activity in December 2008, the other one to a
maximum of activity during a solar eclipse as seen form Earth in March
2015. We then study how the flows and magnetic structures impact the
propagation of the ICME towards Earth. We also discuss the influence
of the injection point with regards to specific structures such as
the position of the current sheet.

---------------------------------------------------------
Title: Implementation of the Soloviev equilibrium as a new CME model
in EUHFORIA
Authors: Linan, Luis; Keppens, Rony; Maharana, Anwesha; Poedts,
Stefaan; Schmieder, Brigitte
2022cosp...44.2431L Altcode:
The EUropean Heliosphere FORecasting Information Asset (EUHFORIA) is
designed to model the evolution of solar eruptions in the heliosphere
and to accurately forecast their geo-effectiveness. In EUHFORIA,
Coronal Mass Ejections (CMEs) are superposed on a steady background
solar wind and injected at $r=0.1\;AU$ into a 3D time-dependent ideal
magnetohydrodynamics heliospheric domain. Our study focuses on the
implementation of a new CME model to improve and extend the CME models
that are currently implemented, for instance by providing a more
realistic geometry or a faster execution time. The novel CME model
is based on an analytical solution of the Grad-Shafranov equation,
called the Soloviev solution, which describes a plasma equilibrium in
a toroidal geometry (Soloviev, Reviews of Plasma Physics, 1975). One of
the main advantages is that magnetic field and other physical quantities
like pressure and density can be determined in terms of an analytic
magnetic flux formula. This flux being a polynomial function of the
local coordinates, we can directly control the interior properties
(in terms of shape and topology) within the cross-section of the toroid
with the spherical inner boundary at $r=0.1\;AU$. Hence, in practice,
the numerical computation of this model is less time consuming than the
FRi3D CME model that requires the numerical solution of differential
equations in each time step (Isavnin, Astrophys. J., 2016). Furthermore,
our implementation offers a wide range of free parameters, including the
shape of the model (aspect ratio, shape of the poloidal cross-section)
to the distribution and strength of the magnetic field lines in the
torus. This suffices to approach the geometry and characteristics
of observed CMEs. Some parameters are limited well-defined ranges,
to ensure basic physical aspects like positivity of thermodynamic
quantities. After the Soloviev CME is injected into the heliospheric
domain of EUHFORIA as a time-dependent boundary condition, it is
self-consistently evolved by the magnetohydrodynamics equations to
Earth. Finally, we present a test case CME modelled with Soloviev
and compare the plasma and magnetic field predictions with the
observations. This research has received funding from the European
Union's Horizon 2020 research and innovation programme under grant
agreement No 870405 (EUHFORIA 2.0)

---------------------------------------------------------
Title: Modelling the geoeffectiveness of the CME-CME interaction
event of early September 2014
Authors: Maharana, Anwesha; Scolini, Camilla; Poedts, Stefaan;
Schmieder, Brigitte
2022cosp...44.1391M Altcode:
Coronal mass ejections (CMEs) undergo interaction with other CMEs and
the structures in the solar wind like high-speed streams, co-rotating
interaction regions and stream interaction regions, while propagating
through the heliosphere. In this study, we present the evolution of
two successive CMEs that erupted from the Sun on September 8, 2014,
and September 10, 2014, respectively, from AR12158. The first CME was
a side hit on Earth and provided preconditioning in the heliosphere
for the second CME's propagation. The second CME was predicted to be
geoeffective based on the remote observations of the CME chirality and
tilt. However, a mismatch in the tilt of the second CME was observed
close to Earth (Cho et al., 2017), pointing to CME rotation during its
propagation. The magnetic ejecta, unexpectedly, resulted in positive
Bz but a geoeffective sheath was developed during the evolution
and the interaction in the heliosphere that resulted in a minimum
Dst ~ -100nT at Earth. Hence, the geoeffectiveness of the various
sub-structures involved in this event was mis-predicted. In-situ
observations taken at sparse localized points in the heliosphere pose
a challenge in capturing the complete picture of the CME and solar
wind dynamics. Therefore, we perform 3D MHD simulations that provide
a global picture, making it convenient to probe into the interesting
phenomena of this event. We use the EUropean Heliosphere FORecasting
Information Asset (EUHFORIA) to model the background solar wind in 3D,
launch the flux rope CMEs in it and let the CMEs evolve till Earth. In
this work, we aim to reproduce the observed plasma and magnetic field
properties, especially the negative Bz of the sheath and the positive
Bz of the ejecta at Earth. We investigate the possible factors and
processes responsible for the development of geoeffectiveness, such as
CME rotation, the interplay of the two CMEs, and the interaction with
the surrounding solar wind. This research has received funding from
the European Union's Horizon 2020 research and innovation programme
under grant agreement No 870405 (EUHFORIA 2.0)

---------------------------------------------------------
Title: Pressure balance of coronal mass ejections during their
Sun-Earth journey modelled by 3D MHD EUHFORIA simulations
Authors: Schmieder, Brigitte; Dasso, Sergio; Grison, Benjamin;
Demoulin, Pascal; Verbeke, Christine; Scolini, Camilla; Samara,
Evangelia; Poedts, Stefaan
2022cosp...44.2474S Altcode:
The aim of this work is to understand the signatures of three coronal
mass ejections (CMEs) at the Lagrange point L1 launched from the Sun
between 15 and 18 July 2002. We use the EUropean Heliosphere FORecasting
Information Asset (EUHFORIA) model to simulate their propagation and
interaction in the background solar wind. The approach is to place
virtual spacecraft along the Sun-Earth line. We set up the initial
conditions at 0.1 au, modelling each CME using the linear force free
spheromak model. We perform an analysis on the pressures acting
within the first and the last CMEs of the series (CME1 and CME3)
and investigate the role of pressure (un)balance in their expansion,
while the second CME (CME2) was too compressed to be able to expand
its ejecta during propagation. We find that the magnetic pressure
within CME1 and CME3 was prominent at 0.1 au and rapidly decreased
between 0.1 au and Earth, so that the gas pressure was progressively
dominating in their extended ejecta.

---------------------------------------------------------
Title: Chromospheric Recurrent Jets in a Sunspot Group and Their
Intergranular Origin
Authors: Zhao, Jie; Su, Jiangtao; Yang, Xu; Li, Hui; Schmieder,
Brigitte; Ahn, Kwangsu; Cao, Wenda
2022ApJ...932...95Z Altcode: 2022arXiv220506981Z
We report on high-resolution observations of recurrent fan-like jets
by the Goode Solar Telescope in multiple wavelengths inside a sunspot
group. The dynamics behavior of the jets is derived from the Hα line
profiles. Quantitative values for one well-identified event have been
obtained, showing a maximum projected velocity of 42 km s-1
and a Doppler shift of the order of 20 km s-1. The
footpoints/roots of the jets have a lifted center on the Hα line
profile compared to the quiet Sun, suggesting a long-lasting heating at
these locations. The magnetic field between the small sunspots in the
group shows a very high resolution pattern with parasitic polarities
along the intergranular lanes accompanied by high-velocity converging
flows (4 km s-1) in the photosphere. Magnetic cancellations
between the opposite polarities are observed in the vicinity of
the footpoints of the jets. Along the intergranular lanes horizontal
magnetic field around 1000 G is generated impulsively. Overall, all the
kinetic features at the different layers through the photosphere and
chromosphere favor a convection-driven reconnection scenario for the
recurrent fan-like jets and evidence a site of reconnection between the
photosphere and chromosphere corresponding to the intergranular lanes.

---------------------------------------------------------
Title: Non-LTE Inversion of Prominence Spectroscopic Observations
in Hα and Mg II h&amp;k lines
Authors: Jejčič, Sonja; Heinzel, Petr; Schmieder, Brigitte; Gunár,
Stanislav; Mein, Pierre; Mein, Nicole; Ruan, Guiping
2022ApJ...932....3J Altcode:
We continued our investigation of the plasma characteristics of a
quiescent prominence that occurred on 2017 March 30. The prominence
was observed simultaneously by several instruments, including the
Interface Region Imaging Spectrograph (IRIS) and the Multichannel
Subtractive Double Pass (MSDP) spectrograph operating at the Meudon
solar tower. We focused on IRIS Mg II h&amp;k and MSDP Hα spectra,
selecting 55 well-coaligned points within the prominence. We computed
an extensive grid of 63,000 isothermal and isobaric 1D-slab prominence
models with a non-LTE (i.e., departures from the local thermodynamic
equilibrium) radiative transfer code. We then performed a 1.5D
spectral inversion searching for an optimal model that best fits
five parameters of the observed profiles (observables), namely,
the integrated intensity of the Hα and Mg II k lines, the FWHM of
both lines, and the ratio of intensities of the Mg II k and Mg II h
lines. The latter is sensitive to temperature. Our results show that
the prominence is a low-temperature structure, mostly below 10,000
K, with some excursions to higher values (up to 18,000 K) but also
rather low temperatures (around 5000 K). The microturbulent velocity is
typically low, peaking around 8 km s-1, and electron density
values are of the order of 1010 cm-3. The peak
effective thickness is 500 km, although the values range up to 5000
km. The studied prominence is rather optically thin in the Hα line
and optically thick in the Mg II h&amp;k lines.

---------------------------------------------------------
Title: First high resolution interferometric observation of a solar
prominence with ALMA
Authors: Labrosse, Nicolas; Rodger, Andrew S.; Radziszewski, Krzysztof;
Rudawy, Paweł; Antolin, Patrick; Fletcher, Lyndsay; Levens, Peter J.;
Peat, Aaron W.; Schmieder, Brigitte; Simões, Paulo J. A.
2022MNRAS.513L..30L Altcode: 2022arXiv220212434L; 2022MNRAS.tmpL..22L
We present the first observation of a solar prominence at 84 - 116 GHz
using the high resolution interferometric imaging of ALMA. Simultaneous
observations in Hα from Białkaw Observatory and with SDO/AIA reveal
similar prominence morphology to the ALMA observation. The contribution
functions of 3 mm and Hα emission are shown to have significant
overlap across a range of gas pressures. We estimate the maximum
millimetre-continuum optical thickness to be τ3mm ≍ 2,
and the brightness temperature from the observed Hα intensity. The
brightness temperature measured by ALMA is ~6000 - 7000 K in the
prominence spine, which correlates well with the estimated brightness
temperature for a kinetic temperature of 8000 K.

---------------------------------------------------------
Title: HiRISE - High-Resolution Imaging and Spectroscopy Explorer
- Ultrahigh resolution, interferometric and external occulting
coronagraphic science
Authors: Erdélyi, Robertus; Damé, Luc; Fludra, Andrzej; Mathioudakis,
Mihalis; Amari, T.; Belucz, B.; Berrilli, F.; Bogachev, S.; Bolsée,
D.; Bothmer, V.; Brun, S.; Dewitte, S.; de Wit, T. Dudok; Faurobert,
M.; Gizon, L.; Gyenge, N.; Korsós, M. B.; Labrosse, N.; Matthews,
S.; Meftah, M.; Morgan, H.; Pallé, P.; Rochus, P.; Rozanov, E.;
Schmieder, B.; Tsinganos, K.; Verwichte, E.; Zharkov, S.; Zuccarello,
F.; Wimmer-Schweingruber, R.
2022ExA...tmp...21E Altcode:
Recent solar physics missions have shown the definite role of waves and
magnetic fields deep in the inner corona, at the chromosphere-corona
interface, where dramatic and physically dominant changes occur. HiRISE
(High Resolution Imaging and Spectroscopy Explorer), the ambitious new
generation ultra-high resolution, interferometric, and coronagraphic,
solar physics mission, proposed in response to the ESA Voyage 2050
Call, would address these issues and provide the best-ever and most
complete solar observatory, capable of ultra-high spatial, spectral,
and temporal resolution observations of the solar atmosphere, from the
photosphere to the corona, and of new insights of the solar interior
from the core to the photosphere. HiRISE, at the L1 Lagrangian
point, would provide meter class FUV imaging and spectro-imaging,
EUV and XUV imaging and spectroscopy, magnetic fields measurements,
and ambitious and comprehensive coronagraphy by a remote external
occulter (two satellites formation flying 375 m apart, with a
coronagraph on a chaser satellite). This major and state-of-the-art
payload would allow us to characterize temperatures, densities, and
velocities in the solar upper chromosphere, transition zone, and inner
corona with, in particular, 2D very high resolution multi-spectral
imaging-spectroscopy, and, direct coronal magnetic field measurement,
thus providing a unique set of tools to understand the structure and
onset of coronal heating. HiRISE's objectives are natural complements
to the Parker Solar Probe and Solar Orbiter-type missions. We present
the science case for HiRISE which will address: i) the fine structure
of the chromosphere-corona interface by 2D spectroscopy in FUV at
very high resolution; ii) coronal heating roots in the inner corona by
ambitious externally-occulted coronagraphy; iii) resolved and global
helioseismology thanks to continuity and stability of observing at the
L1 Lagrange point; and iv) solar variability and space climate with,
in addition, a global comprehensive view of UV variability.

---------------------------------------------------------
Title: Solar Jets: SDO and IRIS Observations in the Perspective of
New MHD Simulations
Authors: Schmieder, Brigitte
2022FrASS...920183S Altcode: 2022arXiv220111541S
Solar jets are observed as collimated plasma beams over a large range
of temperatures and wavelengths. They have been observed in H α
and optical lines for more than 50 years and called surges. The term
"jet" comes from X-ray observations after the launch of the Yohkoh
satellite in 1991. They are the means of transporting energy through the
heliosphere and participate to the corona heating and the acceleration
of solar wind. Several characteristics have been derived about their
velocities, their rates of occurrence, and their relationship with
CMEs. However, the initiation mechanism of jets, e.g. emerging flux,
flux cancellation, or twist, is still debated. In the last decade
coordinated observations of the Interface Region Imaging Spectrograph
(IRIS) with the instruments on board the Solar Dynamic Observatory (SDO)
allow to make a step forward for understanding the trigger of jets and
the relationship between hot jets and cool surges. We observe at the
same time the development of 2D and 3D MHD numerical simulations to
interpret the results. This paper summarizes recent studies of jets
showing the loci of magnetic reconnection in null points or in bald
patch regions forming a current sheet. In the pre-jet phase a twist is
frequently detected by the existence of a mini filament close to the
dome of emerging flux. The twist can also be transferred to the jet
from a flux rope in the vicinity of the reconnection by slippage of
the polarities. Bidirectional flows are detected at the reconnection
sites. We show the role of magnetic currents detected in the footprints
of flux rope and quasi-separatrix layers for initiating the jets. We
select a few studies and show that with the same observations, different
interpretations are possible based on different approaches e.g. non
linear force free field extrapolation or 3D MHD simulation.

---------------------------------------------------------
Title: Empirical atmosphere model in a mini flare during magnetic
reconnection
Authors: Schmieder, Brigitte; Joshi, Reetika; Chandra, Ramesh;
Aulanier, Guillaume; Tei, Akiko; Heinzel, Petr; Tomin, James; Vilmer,
Nicole; Bommier, Veronique
2021arXiv211206790S Altcode:
A spatio-temporal analysis of IRIS spectra of MgII, CII, and SiIV ions
allows us to study the dynamics and the stratification of the flare
atmosphere along the line of sight during the magnetic reconnection
phase at the jet base. Strong asymmetric MgII and CII line profiles with
extended blue wings observed at the reconnection site are interpreted
by the presence of two chromospheric temperature clouds: one explosive
cloud with blueshifts at 290 km/s and one cloud with smaller Doppler
shift (around 36 km/s). Simultaneously at the same location a mini
flare was observed with strong emission in multi temperatures (AIA),
in several spectral IRIS lines (e.g. Oiv and Siiv, Mgii), absorption
of identified chromospheric lines in Siiv line profile, enhancement
of the Balmer continuum and X-ray emission by FERMI/GBM. With the
standard thick-target flare model we calculate the energy of non thermal
electrons observed by FERMI and compare it to the energy radiated by
the Balmer continuum emission. We show that the low energy input by
non thermal electrons above 20 keV was still sufficient to produce
the excess of Balmer continuum.

---------------------------------------------------------
Title: Filament Eruption Driving EUV Loop Contraction and Then
Expansion above a Stable Filament
Authors: Chandra, Ramesh; Démoulin, Pascal; Devi, Pooja; Joshi,
Reetika; Schmieder, Brigitte
2021ApJ...922..227C Altcode: 2021arXiv210907821C
We analyze the observations of EUV loop evolution associated with the
filament eruption located at the border of an active region (AR). The
event SOL2013-03-16T14:00 was observed with a large difference in
view point by the Solar Dynamics Observatory and Solar Terrestrial
Relations Observatory. The filament height is fitted with the sum of
a linear and exponential function. These two phases point to different
physical mechanisms such as tether-cutting reconnection and a magnetic
instability. While no X-ray emission is reported, this event presents
classical eruption features like separation of double ribbons and the
growth of flare loops. We report the migration of the southern foot of
the erupting filament flux rope due to the interchange reconnection
with encountered magnetic loops of a neighboring AR. Parallel to the
erupting filament, a stable filament remains in the core of the AR. The
specificity of this eruption is that coronal loops, located above the
nearly joining ends of the two filaments, first contract in phase, then
expand and reach a new stable configuration close to the one present at
the eruption onset. Both contraction and expansion phases last around
20 minutes. The main difference with previous cases is that the PIL bent
about 180° around the end of the erupting filament because the magnetic
configuration is at least tripolar. These observations are challenging
for models that interpreted previous cases of loop contraction within
a bipolar configuration. New simulations are required to broaden the
complexity of the configurations studied.

---------------------------------------------------------
Title: Balmer continuum enhancement detected in a mini flare observed
with IRIS
Authors: Joshi, Reetika; Schmieder, Brigitte; Heinzel, Petr; Tomin,
James; Chandra, Ramesh; Vilmer, Nicole
2021A&A...654A..31J Altcode: 2021arXiv210711651J
Context. Optical and near-UV continuum emissions in flares contribute
substantially to the flare energy budget. Two mechanisms play an
important role for continuum emission in flares: hydrogen recombination
after sudden ionization at chromospheric layers, and transportation of
the energy radiatively from the chromosphere to lower layers in the
atmosphere, the so-called back-warming. Aims: The aim of the
paper is to distinguish between these two mechanisms for the excess of
the Balmer continuum observed in a flare. Methods: We combined
the observations of the Balmer continuum obtained with the Interface
Region Imaging Spectrograph (IRIS) (spectra and slit-jaw images (SJIs)
2832 Å) and hard X-ray (HXR) emission detected by the Fermi/Gamma Burst
Monitor (GBM) during a mini flare. The calibrated Balmer continuum
was compared to non-local thermodynamic equilibrium (LTE) radiative
transfer flare models, and the radiated energy was estimated. Assuming
thick target HXR emission, we calculated the energy of the nonthermal
electrons detected by the Fermi/GBM and compared it to the radiated
energy. Results: The favorable argument of a relation between
the Balmer continuum excess and the HXR emission is that there is
a good time coincidence between them. In addition, the shape of the
maximum brightness in the 2832 SJIs, which is mainly due to this Balmer
continuum excess, is similar to that of the Fermi/GBM light curve. The
electron-beam flux estimated from Fermi/GBM between 109 and
1010 erg s−1 cm−2 is consistent
with the beam flux required in non-LTE radiative transfer models
to obtain the excess of Balmer continuum emission observed in this
IRIS spectra. Conclusions: The low-energy input by nonthermal
electrons above 20 keV is sufficient to produce the enhancement in the
Balmer continuum emission. This could be explained by the topology of
the reconnection site. The reconnection starts in a tiny bald-patch
region, which is transformed dynamically into an X-point current
sheet. The size of the interacting region would be below the spatial
resolution of the instrument.

---------------------------------------------------------
Title: Spectro-imagery of an active tornado-like prominence: Formation
and evolution
Authors: Barczynski, Krzysztof; Schmieder, Brigitte; Peat, Aaron W.;
Labrosse, Nicolas; Mein, Pierre; Mein, Nicole
2021A&A...653A..94B Altcode: 2021arXiv210604259B
Context. The dynamical nature of fine structures in prominences remains
an open issue, including rotating flows in tornado prominences. While
the Atmospheric Imaging Assembly imager aboard the Solar Dynamics
Observatory allowed us to follow the global structure of a tornado-like
prominence for five hours, the Interface Region Imaging Spectrograph,
and the Multichannel Subtractive Double Pass spectrograph permitted
to obtain plasma diagnostics of its fine structures. Aims: We
aim to address two questions. Firstly, is the observed plasma rotation
conceptually acceptable in a flux rope magnetic support configuration
with dips? Secondly, how is the plasma density distributed in the
tornado-like prominence? Methods: We calculated line-of-sight
velocities and non-thermal line widths using Gaussian fitting for Mg II
lines and the bisector method for Hα line. We determined the electron
density from Mg II line integrated intensities and profile fitting
methods using 1D non-LTE radiative transfer theory models. 
Results: The global structure of the prominence observed in Hα, and
Mg II h, and k line fits with a magnetic field structure configuration
with dips. Coherent Doppler shifts in redshifted and blueshifted areas
observed in both lines were detected along rapidly-changing vertical
and horizontal structures. However, the tornado at the top of the
prominence consists of multiple fine threads with opposite flows,
suggesting counter-streaming flows rather than rotation. Surprisingly
we found that the electron density at the top of the prominence could
be larger (1011 cm−3) than in the inner part
of the prominence. Conclusions: We suggest that the tornado
is in a formation state with cooling of hot plasma in a first phase,
and following that, a phase of leakage of the formed blobs with large
transverse flows of material along long loops extended away from the
UV prominence top. The existence of such long magnetic field lines on
both sides of the prominence would stop the tornado-like prominence
from really turning around its axis. Movies are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202140976/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: Solar prominence diagnostics from non-LTE modelling of Mg II
h&amp;k line profiles
Authors: Peat, A. W.; Labrosse, N.; Schmieder, B.; Barczynski, K.
2021A&A...653A...5P Altcode: 2021arXiv210610351P
 Aims: We investigate a new method to for obtaining the plasma
parameters of solar prominences observed in the Mg II h&amp;k spectral
lines by comparing line profiles from the IRIS satellite to a bank
of profiles computed with a one-dimensional non-local thermodynamic
equilibrium (non-LTE) radiative transfer code. Methods: Using a
grid of 1007 one-dimensional non-LTE radiative transfer models, some
including a prominence-corona transition region (PCTR), we carry out
this new method to match computed spectra to observed line profiles
while accounting for line core shifts not present in the models. The
prominence observations were carried out by the IRIS satellite on 19
April 2018. Results: The prominence is very dynamic with many
flows, including a large arm extending from the main body seen near the
end of the observation. This flow is found to be redshifted, as is the
prominence overall. The models are able to recover satisfactory matches
in areas of the prominence where single line profiles are observed. We
recover: mean temperatures of 6000-50 000 K; mean pressures of 0.01-0.5
dyne cm−2; column masses of 3.7 × 10−8-5
× 10−4 g cm−2; a mean electron density
of 7.3 × 108-1.8 × 1011 cm−3;
and an ionisation degree nHII/nHI = 0.03 −
4500. The highest values for the ionisation degree are found in
areas where the line of sight crosses mostly plasma from the PCTR,
correlating with high mean temperatures and correspondingly no Hα
emission. Conclusions: This new method naturally returns
information on how closely the observed and computed profiles match,
allowing the user to identify areas where no satisfactory match between
models and observations can be obtained. The inclusion of the PCTR was
found to be important when fitting models to data as regions where
satisfactory fits were found were more likely to contain a model
encompassing a PCTR. The line core shift can also be recovered from
this new method, and it shows a good qualitative match with that of
the line core shift found by the quantile method. This demonstrates
the effectiveness of the approach to line core shifts in the new
method. Movies associated to Figs. 10 and A.1 are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202140907/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: Fine Structures of an EUV Wave Event from Multi-viewpoint
Observations
Authors: Chandra, Ramesh; Chen, P. F.; Devi, Pooja; Joshi, Reetika;
Schmieder, Brigitte; Moon, Yong-Jae; Uddin, Wahab
2021ApJ...919....9C Altcode: 2021arXiv210614024C
In this study, we investigate an extreme ultraviolet (EUV) wave event
on 2010 February 11, which occurred as a limb event from the Earth
viewpoint and a disk event from the Solar Terrestrial Relations
Observatory-Behind viewpoint. We use the data obtained by the
Atmospheric Imaging Assembly on board the Solar Dynamics Observatory
in various EUV channels. The EUV wave event was launched by a partial
prominence eruption. Compared with some EUV wave events in previous
works, this EUV wave event contains a faster wave with a speed of
~445 ± 6 km s-1, which we call a coronal Moreton wave,
and a slower wave with a speed of ~298 ± 5 km s-1, which
we call the Extreme Ultraviolet Imaging Telescope (EIT) wave. The
coronal Moreton wave is identified as a fast-mode wave and the EIT
wave is identified as an apparent propagation due to successive
field-line stretching. We also observe a stationary front associated
with the fast-mode EUV wave. This stationary front is explained as
mode conversion from the coronal Moreton wave to a slow-mode wave near
a streamer.

---------------------------------------------------------
Title: ICMEs and low plasma density in the solar wind observed at L1
Authors: Schmieder, Brigitte; Verbeke, Christine; Chané, Emmanuel;
Démoulin, Pascal; Poedts, Stefaan; Grison, Benjamin
2021EGUGA..23.1799S Altcode:
Different regimes of the solar wind have been observed at L1 during and
after the passage of ICMEs, particularly anomalies with very low plasma
density. From the observations at L1 (ACE) we identified different
possible cases. A first case was explained by the evacuation of the
plasma due over expansion of the ICME (May 2002). The second case on
July 2002 is intriguing.In July 2002, three halo fast speed ICMEs,
with their origin in the central part of the Sun, have surprisingly
a poor impact on the magnetosphere (Dst &gt; -28 nT). Analyzing the
characteristics of the first ICME at L1, we conclude that the spacecraft
crosses the ICME with a large impact (Bx component in GSE coordinates is
dominant). The plasma density is low, just behind this first ICME. Next,
we explore the generic conditions of low density formation in the
EUHFORIA simulations.The very low density plasma after the sheath
could be explained by the spacecraft crossing, on the side of the
flux rope, while behind the front shock. We investigate two possible
interpretations. The shock was able to compress and accelerate so much
the plasma that a lower density is left behind. This can also be due
to an effect of the sheath magnetic field which extends the flux rope
effect on the sides of it, so a decrease of plasma density could occur
like behind a moving object (here the sheath field). The following ICME,
with also a low density, could be an intrinsic case with the formation
in the corona of a cavity. Finally, we present some runs of EUHFORIA
which fit approximately these data and argue in favor of the possible
interpretations detailed above.

---------------------------------------------------------
Title: Over-expansion of a coronal mass ejection generates
sub-Alfvénic plasma conditions in the solar wind at Earth
Authors: Chané, E.; Schmieder, B.; Dasso, S.; Verbeke, C.; Grison,
B.; Démoulin, P.; Poedts, S.
2021A&A...647A.149C Altcode:
Context. From May 24-25, 2002, four spacecraft located in the solar
wind at about 1 astronomical unit (au) measured plasma densities
one to two orders of magnitude lower than usual. The density was
so low that the flow became sub-Alfvénic for four hours, and the
Alfvén Mach number was as low as 0.4. Consequently, the Earth lost
its bow shock, and two long Alfvén wings were generated. 
Aims: This is one of the lowest density events ever recorded in the
solar wind at 1 au, and the least documented one. Our goal is to
understand what caused the very low density. Methods: Large
Angle and Spectrometric Coronagraph (LASCO) and in situ data were
used to identify whether something unusual occurred that could have
generated such low densities Results: The very low density was
recorded inside a large interplanetary coronal mass ejection (ICME),
which displayed a long, linearly declining velocity profile, typical
of expanding ICMEs. We deduce a normalised radial expansion rate of
1.6. Such a strong expansion, occurring over a long period of time,
implies a radial size expansion growing with the distance from the Sun
to the power 1.6. This can explain a two-orders-of-magnitude drop in
plasma density. Data from LASCO and the Advanced Composition Explorer
show that this over-expanding ICME was travelling in the wake of a
previous ICME. Conclusions: The very low densities measured
in the solar wind in May 2002 were caused by the over-expansion of
a large ICME. This over-expansion was made possible because the ICME
was travelling in a low-density and high-velocity environment present
in the wake of another ICME coming from a nearby region on the Sun and
ejected only three hours previously. Such conditions are very unusual,
which explains why such very low densities are almost never observed.

---------------------------------------------------------
Title: Observations of a prominence eruption and loop contraction
Authors: Devi, Pooja; Démoulin, Pascal; Chandra, Ramesh; Joshi,
Reetika; Schmieder, Brigitte; Joshi, Bhuwan
2021A&A...647A..85D Altcode: 2021arXiv210107682D
Context. Prominence eruptions provide key observations to understand
the launch of coronal mass ejections as their cold plasma traces a
part of the unstable magnetic configuration. Aims: We select a
well observed case to derive observational constraints for eruption
models. Methods: We analyze the prominence eruption and loop
expansion and contraction observed on 02 March 2015 associated with
a GOES M3.7 class flare (SOL2015-03-02T15:27) using the data from
Atmospheric Imaging Assembly (AIA) and the Reuven Ramaty High Energy
Solar Spectroscopic Imager (RHESSI). We study the prominence eruption
and the evolution of loops using the time-distance techniques. 
Results: The source region is a decaying bipolar active region where
magnetic flux cancellation is present for several days before the
eruption. AIA observations locate the erupting prominence within a flux
rope viewed along its local axis direction. We identify and quantify
the motion of loops in contraction and expansion located on the side
of the erupting flux rope. Finally, RHESSI hard X-ray observations
identify the loop top and two foot-point sources. Conclusions:
Both AIA and RHESSI observations support the standard model of eruptive
flares. The contraction occurs 19 min after the start of the prominence
eruption indicating that this contraction is not associated with
the eruption driver. Rather, this prominence eruption is compatible
with an unstable flux rope where the contraction and expansion of
the lateral loop is the consequence of a side vortex developing
after the flux rope is launched. Movies are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202040042/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: Multi-thermal atmosphere of a mini-solar flare during magnetic
reconnection observed with IRIS
Authors: Joshi, Reetika; Schmieder, Brigitte; Tei, Akiko; Aulanier,
Guillaume; Lörinčík, Juraj; Chandra, Ramesh; Heinzel, Petr
2021A&A...645A..80J Altcode: 2020arXiv201015401J
Context. The Interface Region Imaging Spectrograph (IRIS) with its
high spatial and temporal resolution facilitates exceptional plasma
diagnostics of solar chromospheric and coronal activity during magnetic
reconnection. Aims: The aim of this work is to study the fine
structure and dynamics of the plasma at a jet base forming a mini-flare
between two emerging magnetic fluxes (EMFs) observed with IRIS and the
Solar Dynamics Observatory instruments. Methods: We proceed to
a spatio-temporal analysis of IRIS spectra observed in the spectral
ranges of Mg II, C II, and Si IV ions. Doppler velocities from Mg II
lines were computed using a cloud model technique. Results:
Strong asymmetric Mg II and C II line profiles with extended blue
wings observed at the reconnection site (jet base) are interpreted by
the presence of two chromospheric temperature clouds: one explosive
cloud with blueshifts at 290 km s-1 and one cloud with
smaller Doppler shift (around 36 km s-1). Simultaneously at
the same location (jet base), strong emission of several transition
region lines (e.g. O IV and Si IV), emission of the Mg II triplet
lines, and absorption of identified chromospheric lines in Si IV
broad profiles have been observed and analysed. Conclusions:
Such observations of IRIS line and continuum emissions allow us
to propose a stratification model for the white light, mini-flare
atmosphere with multiple layers of different temperatures along the
line of sight in a reconnection current sheet. It is the first time
that we could quantify the fast speed (possibly Alfvénic flows)
of cool clouds ejected perpendicularly to the jet direction via the
cloud model technique. We conjecture that the ejected clouds come from
plasma which was trapped between the two EMFs before reconnection or
be caused by chromospheric-temperature (cool) upflow material similar
to a surge during reconnection. Movies are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202039229/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: Spectral inversion of H-alpha and MgII lines in quiescent
prominences
Authors: Heinzel, Petr; Schmieder, Brigitte; Ruan, Guiping; Mein,
Pierre; Gunár, Stanislav; Jejcic, Sonja; Mein, Nicole
2021cosp...43E1764H Altcode:
Recent spectral analysis of simultaneous H-alpha (MSDP) and MgII
lines (IRIS) (Guiping et al. 2019) has revealed certain bifurcation
in resulting models. Two solutions were found from the line inversions
using the non-LTE modeling: relatively high kinetic temperature and low
non-thermal motions or temperatures mostly compatible with standard ones
plus non-thermal motions of the order of 16 km/sec. Here we will present
an improved spectral line inversion technique which clearly prefers
the latter solution. Strong non-thermal motions are then interpreted
as a mixture of microturbulence and the line-of-sight dynamics of
prominence fine-structure threads. A detailed multithread modeling with
the 2D non-LTE code and stochastic distributions of threads (position,
dynamics) is now in progress and we will show our preliminary results.

---------------------------------------------------------
Title: Magnetic support of the solar filaments
Authors: Schmieder, Brigitte; Aulanier, Guillaume; Gunár, Stanislav;
Dudik, Jaroslav; Heinzel, Petr
2021cosp...43E1766S Altcode:
The scale height in prominence is 500 km at maximum. However, non
activated prominences can reach an altitude of 50000 km or more. Hanging
filaments observed over the limb give the impression of quasi vertical
structures. It was already the view in the past but reactivated by the
movies of Hinode in Ca II line showing fuzzing vertical structures. In
the corona it is not possible to measure the magnetic field supporting
prominences. Only extrapolations of the photospheric magnetic field
explain how cool plasma embedded in the dips of the magnetic field
lines can be supported in the hot corona. I will review a few papers
showing the distribution of the cool plasma dips and the observations
of filaments on the disk visible in H$\alpha$ and in UV. A recent
paper shows how a 3D extrapolation model and a radiative-transfer
based H$\alpha$ visualization method leads to H$\alpha$ prominence
fine structures. Finally, I will discuss the perspective effects on
the perceived morphology of observed and modeled prominences.

---------------------------------------------------------
Title: Active tornado in a prominence observed in H-alpha with MSDP
and Mg II with IRIS
Authors: Barczynski, Krzysztof; Schmieder, Brigitte; Mein, Pierre;
Labrosse, Nicolas; Mein, Nicole; Peat, Aaron
2021cosp...43E.973B Altcode:
Large prominences with highly dynamic plasma features expand outwards in
the solar atmosphere, often in loop or arch-shape or as a tornado. The
origin of the rotating flow in prominence tornadoes is not fully
understood yet. We aim to find an answer to two long-standing questions:
what is the nature of the plasma flow and rotation in the prominence,
and the role of the magnetic field configuration in the prominence
dynamics? To this aim, we use observations from the Atmospheric Imaging
Assembly (AIA) imager aboard the Solar Dynamics Observatory (SDO) to
follow the plasma dynamics related to magnetic field. Simultaneous
observations from the Interface Region Imaging Spectrograph (IRIS)
and the Multi subtractive Double pass spectrograph (MSDP) allow
us to study the plasma properties (intensity, Doppler velocity,
non-thermal line broadening) of a tornado-like structure. We calculate
line-of-sight velocities and non-thermal line width using Gaussian
fitting for Mg II lines (IRIS) and a bisector method for H$\alpha$
line (MSDP). We determine the electron density and temperature from
Mg II line integrated intensities using radiative transfer theory. We
find that the red and blue Doppler-shifted areas present a coherent
position in H$\alpha$ and Mg II h\&amp;k lines along the fast-evolving
prominence features. The EUV observations suggest long magnetic field
lines on the sides of the prominence. The tornado-like at the top of
the prominence consists of multiplefine threads with opposite flows, all
of them being supported in dips of long magnetic field lines. From time
to time, condensed blobs escape along these field lines. We conjecture
that micro or macro turbulence exists at the top of the prominence
and could form the small threads giving the impression of rotation.

---------------------------------------------------------
Title: Twist transfer to a solar jet from a big flux rope detected
in the HMI magnetogram
Authors: Joshi, Reetika; Schmieder, Brigitte; Aulanier, Guillaume;
Chandra, Ramesh; Bommier, Veronique
2021cosp...43E1752J Altcode:
Solar jets often have a helical structure containing both hot and
cool ejected plasma. Different mechanisms are proposed to trigger
jets by magnetic reconnection between the emergence of magnetic flux
and environment, or induced by twisted photospheric motions bringing
the system to instability. Multi-wavelength observations of a twisted
jet observed with the AIA and IRIS is presented to understand how the
twist was injected in the jet from a flux rope, fortunately, IRIS
spectrographic slit was just crossing the reconnection site. This
active region is a result of the collapse of two emerging magnetic
fluxes (EMFs) overlaid by arch filament systems. In the magnetic field
maps, we evidenced the pattern of a long sigmoidal flux rope along
the polarity inversion line between the two EMFs which is the site of
the reconnection. Before the jet, there was an extension of the flux
rope, and a part of it was detached and formed a small bipole with a
bald patch region which dynamically became an X-current sheet over the
dome of one EMF where the reconnection took place. At the time of the
reconnection, the Mg II spectra exhibited a strong extension of the
blue wing which is decreasing over a distance of 10 Mm (from -300 km/s
to a few km/s). This is the signature of the transfer of the twist to
the jet. Comparison with numerical magnetohydrodynamics simulations
confirmed the existence of the long flux rope in the neighborhood
of the jet. We conjecture that there is a transfer of twist to the
jet during the extension of the flux rope to the reconnection site
without the flux rope eruption. The reconnection would start in the
low atmosphere in the bald patch reconnection region and extend at an
X-point along the current sheet formed above.

---------------------------------------------------------
Title: Initiation of CMEs and their geo-effectiveness
Authors: Schmieder, Brigitte; Poedts, Stefaan; Grison, Benjamin;
Demoulin, Pascal; Kim, Rok-Soon; Verbeke, Christine
2021cosp...43E1013S Altcode:
Physical conditions of solar eruptions triggering coronal mass ejections
(CMEs) have been determined by recent multi-wavelength observations
as well by numerical simulations (e.g. OHM). CMEs and flares are the
seeds of the Space Weather. Our analyze consists on a few case studies
of CMEs which have all the good proxies for inducing geo-effectivity
e.g. fast halo CME, central solar disk source. We follow the CMEs
surfing in the solar wind as interplanetary coronal mass ejections
(ICME) or magnetic clouds. We use numerical simulations (EUHFORIA) to
investigate the geo-effectiveness of these ICMEs We study the degree
of deviation of these halo CMEs from the Sun-Earth axis as well as
their deformation and erosion due to their interaction with the ambient
solar wind resulting in magnetic reconnections according to the input
of parameters and their chance to hit other planets. The inhomogeneous
nature of the solar wind and encounters are also important parameters
influencing the impact of CMEs on planetary magnetospheres

---------------------------------------------------------
Title: Modeling Coronal Mass Ejections with EUHFORIA
Authors: Verbeke, Christine; Schmieder, Brigitte; Rodriguez, Luciano;
Poedts, Stefaan; Magdalenic, Jasmina; Pomoell, Jens; Temmer, Manuela;
Asvestari, Eleanna; Scolini, Camilla; Heinemann, Stephan; Hinterreiter,
Jürgen; Samara, Evangelia
2021cosp...43E2358V Altcode:
Fully understanding the origin and evolution of Coronal Mass Ejections
(CMEs) from the Sun to the Earth remains a major topic in current
solar-terrestrial physics and is of key importance to improve our space
weather prediction capabilities. CMEs can drive strong space weather
disturbances at Earth, and their dynamical pressure, magnetic field
configuration and interaction with the solar wind can significantly
alter their arrival time and impact at Earth. One of the key parameters
that determine the geo-effectiveness of the CME is its internal magnetic
configuration. With the EUHFORIA inner-heliosphere magnetohydrodynamics
model, we can model a magnetised CME using a Linear Force Free Spheromak
(LFFS) model, in order to model the internal magnetic structure of
the CME throughout the inner heliosphere. In this talk, we present
an overview of the model assessment efforts that have been made
with EUHFORIA over the past years. We discuss the validation of the
solar wind, as well as the development of the LFFS model. We focus
on determining the sensitivity of the LFFS model input parameters,
as well as some case studies to show our improved modeling of the
CME magnetic field structures at Earth. Finally, we discuss current
limitations and future improvements of the EUHFORIA model.

---------------------------------------------------------
Title: Signature of the expansion of eruptive flux ropes measured
by electric currents
Authors: Schmieder, Brigitte; Aulanier, Guillaume; Janvier, Miho;
Masson, Sophie; Barczynski, Krzysztof
2021cosp...43E1758S Altcode:
MHD models demonstrate that hooks of flare ribbons are the footprints
of eruptive flux ropes and that a decrease of the electric currents
could be the signature of the evolution of the coronal magnetic
field, e.g. the expansion of a line-tied flux rope with constant
end-to-end external twist during the eruption. However in circuit
models the surface electric current has a subsurface fixed source
and therefore the currents should be constant . We analyze 19 X-class
flares observed by Solar Dynamics Observatory (SDO) from 2011 to 2016,
where flare ribbons with hooks are identifiable. For the first time
fine measurements of time-evolution of electric currents inside the
hooks in the observations as well as in the OHM 3D MHD simulation are
performed. Our analysis shows a decrease of the electric current in the
area surrounded by the ribbon hooks during and after the eruption. In
the simulation the rate of current deceasing is similar to that of the
field line elongation. So we interpret the decrease of the electric
currents as due to the expansion of the flux rope in the corona during
the eruption. Our analysis brings a new stone to the standard flare
model in 3D.

---------------------------------------------------------
Title: Imaging Evidence for Solar Wind Outflows Originating from a
Coronal Mass Ejection Footpoint
Authors: Lörinčík, Juraj; Dudík, Jaroslav; Aulanier, Guillaume;
Schmieder, Brigitte; Golub, Leon
2021ApJ...906...62L Altcode: 2020arXiv201004250L
We report on Atmospheric Imaging Assembly observations of plasma
outflows originating in a coronal dimming during a 2015 April 28
filament eruption. After the filament started to erupt, two flare
ribbons formed, one of which had a well-visible hook enclosing a core
(twin) dimming region. Along multiple funnels located in this dimming,
a motion of plasma directed outward started to be visible in the
171 and 193 Å filter channels of the instrument. In time-distance
diagrams, this motion generated a strip-like pattern, which lasted
for more than 5 hr and whose characteristics did not change along
the funnel. We therefore suggest the motion is a signature of
outflows corresponding to velocities ranging between ≍70 and 140
km s-1. Interestingly, the pattern of the outflows and
their velocities were found to be similar to those we observed in a
neighboring ordinary coronal hole. Therefore, the outflows were most
likely a signature of a coronal mass ejection-induced solar wind flowing
along the open-field structures rooted in the dimming region. Further,
the evolution of the hook encircling the dimming region was examined
in the context of the latest predictions imposed for 3D magnetic
reconnection. The observations indicate that the filament's footpoints
were, during their transformation to the dimming region, reconnecting
with surrounding canopies. To our knowledge, our observations present
the first imaging evidence for outflows of plasma from a dimming region.

---------------------------------------------------------
Title: Links between prominence/filament magnetic field and plasma:
What can 3D WPFS models teach us?
Authors: Gunár, Stanislav; Schmieder, Brigitte; Aulanier, Guillaume;
Heinzel, Petr; Mackay, Duncan; Dudik, Jaroslav
2021cosp...43E1769G Altcode:
The magnetic field constitutes the skeleton and the driving force of
prominences/filaments. It supports the dense prominence plasma against
gravity and insulates it from the hot, coronal environment. The
magnetic field is also responsible for the prominence stability,
evolution and eruptions which affect the heliosphere and ultimately
the Earth. However, a strong imbalance exists between the numerous
efforts in detailed modelling of prominence magnetic field and its
understanding from observations. That is due to the complex nature of
the direct (and indirect) observations of solar magnetic fields which
are challenging at the best of times and even more so in prominences
or filaments. The direct observations of the prominence magnetic
field require high-precision spectro-polarimetric measurements and
realistic assumptions about the plasma structure which allow us to
infer the field configuration from its effect on the polarized light
emergent from the observed structures. The indirect observations rely
on the perceived location, shape and dynamics of the prominence or
filament plasma, often using moving small-scale plasma structures
as tracers guided by the field lines. Both methods thus rely on the
presence of observable plasma in the magnetic field configuration,
and on the radiation which carries the information about the in-situ
conditions to the observer. No prominence/filament magnetic field
measurements are made without these two additional components,
which are sometimes an afterthought in the magnetic field models. We
have developed 3D Whole-Prominence Fine Structure (WPFS) models to
illuminate the links between the prominence magnetic field, its plasma
distributed among numerous fine structures and the radiation which
carries the information about the prominence physical conditions to
the observer. What can we learn from these 3D models? For example,
we can see that a small change of the magnetic field configuration
can have a large effect on the perceived structure of prominences and
filaments visible in the H-alpha line. Consequently, this means that
significant changes observed in prominences or filaments do not need
to suggest that equally large changes in the underlying magnetic field
configuration had to occur. In another example, we see that seemingly
incomparable differences in the morphological look of prominences (long
horizontal fine structures versus small blobs of plasma arranged into
more-less vertical features) may not need to imply the existence of
radically different magnetic field configurations. Rather, they might
simply be manifestations of projection effects that can differ greatly
depending on the viewing angle under which we observe the naturally
three-dimensional prominences/filaments.

---------------------------------------------------------
Title: The role of small-scale surface motions in the transfer of
twist to a solar jet from a remote stable flux rope
Authors: Joshi, Reetika; Schmieder, Brigitte; Aulanier, Guillaume;
Bommier, Véronique; Chandra, Ramesh
2020A&A...642A.169J Altcode: 2020arXiv200806887J
Context. Jets often have a helical structure containing ejected plasma
that is both hot and also cooler and denser than the corona. Various
mechanisms have been proposed to explain how jets are triggered,
primarily attributed to a magnetic reconnection between the emergence
of magnetic flux and environment or that of twisted photospheric
motions that bring the system into a state of instability. 
Aims: Multi-wavelength observations of a twisted jet observed with
the Atmospheric Imaging Assembly (AIA) onboard the Solar Dynamics
Observatory and the Interface Region Imaging Spectrograph (IRIS)
were used to understand how the twist was injected into the jet,
thanks to the IRIS spectrographic slit fortuitously crossing the
reconnection site at that time. Methods: We followed the
magnetic history of the active region based on the analysis of the
Helioseismic and Magnetic Imager vector magnetic field computed with
the UNNOFIT code. The nature and dynamics of the jet reconnection site
are characterised by the IRIS spectra. Results: This region
is the result of the collapse of two emerging magnetic fluxes (EMFs)
overlaid by arch filament systems that have been well-observed with AIA,
IRIS, and the New Vacuum Solar Telescope in Hα. In the magnetic field
maps, we found evidence of the pattern of a long sigmoidal flux rope
(FR) along the polarity inversion line between the two EMFs, which is
the site of the reconnection. Before the jet, an extension of the FR
was present and a part of it was detached and formed a small bipole
with a bald patch (BP) region, which dynamically became an X-current
sheet over the dome of one EMF where the reconnection took place. At
the time of the reconnection, the Mg II spectra exhibited a strong
extension of the blue wing that is decreasing over a distance of 10
Mm (from -300 km s-1 to a few km s-1). This
is the signature of the transfer of the twist to the jet. Conclusions: A comparison with numerical magnetohydrodynamics
simulations confirms the existence of the long FR. We conjecture that
there is a transfer of twist to the jet during the extension of the
FR to the reconnection site without FR eruption. The reconnection
would start in the low atmosphere in the BP reconnection region
and extend at an X-point along the current sheet formed above. Movies attached to Figs. 1, 3, 4, and 7 are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202038562/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: Case study of multi-temperature coronal jets for emerging
flux MHD models
Authors: Joshi, Reetika; Chandra, Ramesh; Schmieder, Brigitte;
Moreno-Insertis, Fernando; Aulanier, Guillaume; Nóbrega-Siverio,
Daniel; Devi, Pooja
2020A&A...639A..22J Altcode: 2020arXiv200506064J
Context. Hot coronal jets are a basic observed feature of the solar
atmosphere whose physical origin is still actively debated. 
Aims: We study six recurrent jets that occurred in active region NOAA
12644 on April 4, 2017. They are observed in all the hot filters
of AIA as well as cool surges in IRIS slit-jaw high spatial and
temporal resolution images. Methods: The AIA filters allow us
to study the temperature and the emission measure of the jets using
the filter ratio method. We studied the pre-jet phases by analysing
the intensity oscillations at the base of the jets with the wavelet
technique. Results: A fine co-alignment of the AIA and IRIS
data shows that the jets are initiated at the top of a canopy-like
double-chambered structure with cool emission on one and hot emission
on the other side. The hot jets are collimated in the hot temperature
filters, have high velocities (around 250 km s-1) and
are accompanied by cool surges and ejected kernels that both move
at about 45 km s-1. In the pre-phase of the jets, we find
quasi-periodic intensity oscillations at their base that are in phase
with small ejections; they have a period of between 2 and 6 min,
and are reminiscent of acoustic or magnetohydrodynamic waves. 
Conclusions: This series of jets and surges provides a good case study
for testing the 2D and 3D magnetohydrodynamic emerging flux models. The
double-chambered structure that is found in the observations corresponds
to the regions with cold and hot loops that are in the models below
the current sheet that contains the reconnection site. The cool surge
with kernels is comparable with the cool ejection and plasmoids that
naturally appears in the models. Movies are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202037806/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: Role of the Coronal Environment in the Formation of Four Shocks
Observed without Coronal Mass Ejections at Earth's Lagrangian Point L1
Authors: Pick, M.; Magdalenić, J.; Cornilleau-Wehrlin, N.; Grison,
B.; Schmieder, B.; Bocchialini, K.
2020ApJ...895..144P Altcode:
The main goal of this study is to determine the solar origin of four
single shocks observed at the Lagrange point L1 and followed by storm
sudden commencements (SSCs) during 2002. We look for associated coronal
mass ejections (CMEs), starting from estimates of the transit time from
Sun to Earth. For each CME, we investigate its association with a radio
type II burst, an indicator of the presence of a shock wave. For three
of the events, the type II burst is shown to propagate along the same,
or a similar, direction as the fastest segment of the CME leading
edge. We analyze for each event the role of the coronal environment
in the CME development, the shock formation, and their propagation,
to finally identify its complex evolution. The ballistic velocity
of these shocks during their propagation from the corona to L1 is
compared to the shock velocity at L1. Based on a detailed analysis of
the shock propagation and possible interactions up to 30 solar radii,
we find a coherent velocity evolution for each event, in particular
for one event, the 2002 April 14 SSC, for which a previous study did
not find a satisfactory CME source. For the other three events, we
observe the formation of a white-light shock overlying the different
sources associated with those events. The localization of the event
sources over the poles, together with an origin of the shocks being
due to encounters of CMEs, can explain why at L1 we observe only single
shocks and not interplanetary CMEs.

---------------------------------------------------------
Title: Quasi Periodic Oscillations in the Pre Phases of Recurrent
Jets Highlighting Plasmoids in Current Sheet
Authors: Joshi, Reetika; Chandra, Ramesh; Schmieder, Brigitte;
Aulanier, Guillaume; Devi, Pooja; Moreno-Insertis, Fernando;
Nóbrega-Siverio, Daniel
2020EGUGA..2222351J Altcode:
Solar jets observed at the limb are important to determine the location
of reconnection sites in the corona. In this study, we investigate
six recurrent hot and cool jets occurring in the active region NOAA
12644 as it is crossing the west limb on April 04, 2017. These jets
are observed in all the UV/EUV filters of SDO/AIA and in cooler
temperature formation lines in IRIS slit jaw images. The jets are
initiated at the top of a double chamber vault with cool loops on one
side and hot loops on the other side. The existence of such double
chamber vaults suggests the presence of emerging flux with cool
loops, the hot loops being the reconnected loops similarly as in the
models of Moreno-Insertiset al. 2008, 2013 and Nóbrega-Siverio et
al. 2016. In the preliminary phase of the main jets, quasi periodic
intensity oscillations accompanied by smaller jets are detected in the
bright current sheet between the vault and the preexisting magnetic
field. Individual kernels and plasmoids are ejected in open field lines
along the jets. Plasmoids may launch torsional Alfven waves and the
kernels would be the result of the untwist of the plasmoids in open
magnetic field as proposed in the model of Wyper et al. 2016.

---------------------------------------------------------
Title: Can we explain the low geo-effectiveness of the fast halo
CMEs in 2002 with EUHFORIA?
Authors: Schmieder, Brigitte; Poedts, Stefaan; Verbeke, Christine
2020EGUGA..22.5543S Altcode:
In 2002 (Cycle 23), a weak impact on the magnetosphere of the Earth has
been reported for six halo CMEs related to six X-class flares and with
velocities higher than 1000 km/s. The registered Dst minima are all
between -17 nT and -50 nT. A study of the Sun-Earth chain of phenomena
related to these CMEs reveals that four of them have a source at the
limb and two have a source close to the solar disk center (Schmieder
et al., 2020). All of CME magnetic clouds had a low z-component of the
magnetic field, oscillating between positive and negative values.We
performed a set of EUHFORIA simulations in an attempt to explain the
low observed Dst and the observed magnetic fields. We study the degree
of deviation of these halo CMEs from the Sun-Earth axis and as well as
their deformation and erosion due to their interaction with the ambient
solar wind (resulting in magnetic reconnections) according to the input
of parameters and their chance to hit other planets. The inhomogeneous
nature of the solar wind and encounters are also important parameters
influencing the impact of CMEs on planetary magnetospheres.

---------------------------------------------------------
Title: Modelling and observations: Comparison of the magnetic field
properties in a prominence
Authors: Mackay, D. H.; Schmieder, B.; López Ariste, A.; Su, Y.
2020A&A...637A...3M Altcode:
Context. Direct magnetic field measurements in solar prominences occur
infrequently and are difficult to make and interpret. As a consequence,
alternative methods are needed to derive the main properties of the
magnetic field that supports the prominence mass. This is important for
our understanding of solar prominences, but also for understanding how
eruptive prominences may affect space weather. Aims: We present
the first direct comparison of the magnetic field strength derived
from spectro-polarimetric observations of a solar prominence, with
corresponding results from a theoretical flux rope model constructed
from on-disc normal component magnetograms. Methods: We first
used spectro-polarimetric observations of a prominence obtained with
the magnetograph THEMIS operating in the Canary Islands to derive the
magnetic field of the observed prominence by inverting the Stokes
parameters measured in the He D3 line. Next, we constructed two
data-constrained non-linear force-free field (NLFFF) models of the
same prominence. In one model we assumed a strongly twisted flux rope
solution, and in the other a weakly twisted flux rope solution. 
Results: The physical extent of the prominence at the limb (height
and length) is best reproduced with the strongly twisted flux rope
solution. The line-of-sight average of the magnetic field for the
strongly twisted solution results in a magnetic field that has a
magnitude of within a factor of 1-2 of the observed magnetic field
strength. For the peak field strength along the line of sight,
an agreement to within 20% of the observations is obtained for
the strongly twisted solution. The weakly twisted solution produces
significantly lower magnetic field strengths and gives a poor agreement
with the observations. Conclusions: The results of this first
comparison are promising. We found that the flux rope insertion method
of producing a NLFFF is able to deduce the overall properties of the
magnetic field in an observed prominence.

---------------------------------------------------------
Title: Electric Current Evolution at the Footpoints of Solar Eruptions
Authors: Barczynski, Krzysztof; Aulanier, Guillaume; Janvier, Miho;
Schmieder, Brigitte; Masson, Sophie
2020ApJ...895...18B Altcode: 2020arXiv200407990B
Electric currents play a critical role in the triggering of solar
flares and their evolution. The aim of the present paper is to test
whether the surface electric current has a surface or subsurface
fixed source as predicted by the circuit approach of flare physics,
or is the response of the surface magnetic field to the evolution of
the coronal magnetic field as the MHD approach proposes? Out of all 19
X-class flares observed by SDO from 2011 to 2016 near the disk center,
we analyzed the only nine eruptive flares for which clear ribbon hooks
were identifiable. Flare ribbons with hooks are considered to be the
footprints of eruptive flux ropes in MHD flare models. For the first
time, fine measurements of the time evolution of electric currents
inside the hooks in the observations as well as in the OHM 3D MHD
simulation are performed. Our analysis shows a decrease of the electric
current in the area surrounded by the ribbon hooks during and after the
eruption. We interpret the decrease of the electric currents as due to
the expansion of the flux rope in the corona during the eruption. Our
analysis brings a new contribution to the standard flare model in 3D.

---------------------------------------------------------
Title: Low Geo-Effectiveness of Fast Halo CMEs Related to the 12
X-Class Flares in 2002
Authors: Schmieder, B.; Kim, R. -S.; Grison, B.; Bocchialini, K.;
Kwon, R. -Y.; Poedts, S.; Démoulin, P.
2020JGRA..12527529S Altcode: 2020arXiv200310777S
It is generally accepted that extreme space weather events tend to be
related to strong flares and fast halo coronal mass ejections (CMEs). In
the present paper, we carefully identify the chain of events from
the Sun to the Earth induced by all 12 X-class flares that occurred
in 2002. In this small sample, we find an unusual high rate (58%) of
solar sources with a longitude larger than 74°. Yet all 12 X-class
flares are associated with at least one CME. The fast halo CMEs (50%)
are related to interplanetary CMEs (ICMEs) at L1 and weak Dst minimum
values (more than -51 nT), while five (41%) of the 12 X-class flares
are related to solar proton events (SPEs). We conclude that (i) all
12 analyzed solar events, even those associated with fast halo CMEs
originating from the central disk region, and those ICMEs and SPEs
were not very geo-effective. This unexpected result demonstrates that
the suggested events in the chain (fast halo CME, X-class flares,
central disk region, ICME, and SPE) are not infallible proxies for
geo-effectiveness. (ii) The low value of integrated and normalized
southward component of the interplanetary magnetic field (Bz*) may
explain the low geo-effectiveness for this small sample. In fact,
Bz* is well correlated to the weak Dst and low auroral electrojet
activity. Hence, the only space weather impact at Earth in 2002 we
can explain is based on Bz* at L1.

---------------------------------------------------------
Title: Observation of All Pre- and Post-reconnection Structures
Involved in Three-dimensional Reconnection Geometries in Solar
Eruptions
Authors: Dudík, Jaroslav; Lörinčík, Juraj; Aulanier, Guillaume;
Zemanová, Alena; Schmieder, Brigitte
2019ApJ...887...71D Altcode: 2019arXiv191008620D
We report on observations of the two newly identified reconnection
geometries involving erupting flux ropes. In 3D, a flux rope can
reconnect either with a surrounding coronal arcade (recently named
“ar-rf” reconnection) or with itself (“rr-rf” reconnection),
and both kinds of reconnection create a new flux-rope field line and a
flare loop. For the first time, we identify all four constituents of
both reconnections in a solar eruptive event, the filament eruption
of 2011 June 7 observed by Solar Dynamics Observatory/Atmospheric
Imaging Assembly. The ar-rf reconnection manifests itself as shift of
one leg of the filament by more than 25″ northward. At its previous
location, a flare arcade is formed, while the new location of the
filament leg previously corresponded to a footpoint of a coronal loop
in 171 Å. In addition, the evolution of the flare ribbon hooks is
also consistent with the occurrence of ar-rf reconnection as predicted
by MHD simulations. Specifically, the growing hook sweeps footpoints
of preeruptive coronal arcades, and these locations become inside the
hook. Furthermore, the rr-rf reconnection occurs during the peak phase
above the flare arcade, in an apparently X-type geometry involving a
pair of converging bright filament strands in the erupting filament. A
new flare loop forms near the leg of one of the strands, while a bright
blob, representing a remnant of the same strand, is seen ascending
into the erupting filament. All together, these observations vindicate
recent predictions of the 3D standard solar-flare model.

---------------------------------------------------------
Title: Diagnostics of the Prominence Plasma from Hα and Mg II
Spectral Observations
Authors: Ruan, Guiping; Jejčič, Sonja; Schmieder, Brigitte; Mein,
Pierre; Mein, Nicole; Heinzel, Petr; Gunár, Stanislav; Chen, Yao
2019ApJ...886..134R Altcode:
The goal of this paper is to derive the physical conditions of the
prominence observed on 2017 March 30. To do so, we use a unique set
of data in Mg II lines obtained with the space-borne Interface Region
Imaging Spectrograph (IRIS) and in Hα line with the ground-based
Multi-Channel Subtractive Double Pass spectrograph operating at the
Meudon solar tower. Here, we analyze the prominence spectra of Mg
II h and k lines, and the Hα line in the part of the prominence
which is visible in both sets of lines. We compute a grid of 1D
NLTE (i.e., departures from the local thermodynamical equilibrium)
models providing synthetic spectra of Mg II k and h, and Hα lines
in a large space of model input parameters (temperature, density,
pressure, and microturbulent velocity). We compare Mg II and Hα
line profiles observed in 75 positions of the prominence with the
synthetic profiles from the grid of models. These models allow us
to compute the relationships between the integrated intensities
and between the optical thickness in Hα and Mg II k lines. The
optical thickness τ Hα is between 0.05 and 2, and
{τ }Mg{{II}}{{k}}} is between 3 and 200. We show that
the relationship of the observed integrated intensities agrees well
with the synthetic integrated intensities for models with a higher
microturbulence (16 km s-1) and T around 8000 K, ne =
1.5 × 1010 cm-3, p = 0.05 dyne. In this case,
large microturbulence values could be a way to take into account the
large mixed velocities existing in the observed prominence.

---------------------------------------------------------
Title: Bidirectional Reconnection Outflows in an Active Region
Authors: Ruan, Guiping; Schmieder, Brigitte; Masson, Sophie; Mein,
Pierre; Mein, Nicole; Aulanier, Guillaume; Chen, Yao
2019ApJ...883...52R Altcode:
We report on bidirectional coronal reconnection outflows reaching
±200 km s-1 as observed in an active region with the Si
IV and C II spectra of the Interface Region Imaging Spectrograph
(IRIS). The evolution of the active region with an emerging flux,
a failed filament eruption, and a jet is followed in Solar Dynamical
Observatory (SDO)/Atmospheric Imaging Assembly (AIA) filters from
304 to 94 Å, IRIS slit jaw images, and SDO/Helioseismic and Magnetic
Imager movies. The bidirectional outflow reconnection is located at
a bright point visible in multiwavelength AIA filters above an arch
filament system. This suggests that the reconnection occurs between
rising loops above the emergence of magnetic bipoles and the longer,
twisted magnetic field lines remnant of the failed filament eruption
one hour before. The reconnection occurs continuously in the corona
between quasi-parallel magnetic field lines, which is possible in a
3D configuration. The reconnection also triggers a jet with transverse
velocities around 60 km s-1. Blueshifts and redshifts along
its axis confirm the existence of a twist along the jet, which could
have been transferred from the filament flux rope. The jet finally
blows up the material of the filament before coming back during the
second phase. In the Hα Dopplergrams provided by the MSDP spectrograph,
we see more redshift than blueshift, indicating the return of the jet
and filament plasma.

---------------------------------------------------------
Title: Vortex Formations and Its Associated Surges in a Sunspot
Light Bridge
Authors: Yang, Heesu; Lim, Eun-Kyung; Iijima, Haruhisa; Yurchyshyn,
Vasyl; Cho, Kyung-Suk; Lee, Jeongwoo; Schmieder, Brigitte; Kim,
Yeon-Han; Kim, Sujin; Bong, Su-Chan
2019ApJ...882..175Y Altcode:
We report on the successive occurrence of 0.″5 wide photospheric
vortices with strong transverse shear flows at the edge of a sunspot
light bridge (LB), and the subsequent ejection of chromospheric surges
observed using a Visible Inteferometry Spectrograph, a broadband
TiO filter, and a Near InfRared Imaging Spectrograph of the Goode
Solar Telescope operating at Big Bear Solar Observatory. The Hα
surges ejected at the location of the vortices often appeared in
a hollow cylindrical structure. We also observed quasi-periodic
vortex-associated bright Hα plasma blobs moving upward with a speed
of up to 4 km s-1. In view of the strong shear flow at
the edge of the LB, it is likely that the vortices form under the
Kelvin-Helmholtz instability. The surges may result from either the
magnetic tension generated after magnetic reconnection or an acoustic
impulse of a fast photospheric transverse flow. Otherwise, the surges
could also be associated with Alfvénic waves, in which case their
origin could be torsional magnetic fields generated in the process of
the vortex formation.

---------------------------------------------------------
Title: Reminiscences
Authors: Schmieder, Brigitte
2019SoPh..294...53S Altcode: 2019arXiv190304036S
I would like to thank my Solar Physics colleagues for asking me to write
this chapter on my professional life. My main interest has always been
focused on the Sun, our star, from the heating of the corona, to the
dynamics of prominences and their eruptions, flares and coronal mass
ejections to their impact on the Earth. I built a new group in solar
physics and gave to them my enthusiasm. They brought to me a lot of
satisfaction. We have made important advances in solar physics with a
step forward to understand the triggers of solar activity and their
terrestrial effects. Our avant-garde research and discoveries have
opened new topics for the solar community. Mixing observations obtained
on the ground and in space with theory and numerical simulations brings
about a new perspective in research.

---------------------------------------------------------
Title: Geoeffectiveness of the 12 X-class flares in 2002
Authors: Schmieder, Brigitte; Kim, Rocksoon; Grison, Benjamin;
Bocchialini, Karine; Kwon, Young
2019EGUGA..21.1876S Altcode:
We analyze systematically the chain of events related to the 12
X-ray flares of X class occurring in 2002: source region, CME, ICME,
magnetic field at L1, geomagnetic indices, and SEP to determine if
we could explain their weak geo-effectiveness by usual criteria. No
intense geomagnetic storm is related to any of these flares. Only
one of them is associated with a moderate storm. The three others are
associated with a weak storm (-50 nT &lt; min(Dst) &lt; -30 nT). 75 %
of the flares are associated with a halo CME with a good correlation
rate for the speed/flux of the flare. The flare sources are mainly
close to the limb (70%). We conclude that the association of big
flares and strong geomagnetic disturbances may be valid only for
extreme or intense geomagnetic storms. Otherwise the magnetic energy
of active regions is released in an unexpected way into thermal energy
and kinetic energy or in ejections of energetic particles. The most
important parameter is the Bz value and its orientation. It seems that
the CMEs launched with high speed (around 2000 km/s) avoid the Earth
in our sample. The location of the solar source, the shape of the CME,
and the shock front have a direct impact on the geo-effectiveness.

---------------------------------------------------------
Title: Erratum: Correction to: Statistical Analysis of Solar Events
Associated with Storm Sudden Commencements over One Year of Solar
Maximum During Cycle 23: Propagation from the Sun to the Earth
and Effects
Authors: Bocchialini, K.; Grison, B.; Menvielle, M.; Chambodut,
A.; Cornilleau-Wehrlin, N.; Fontaine, D.; Marchaudon, A.; Pick, M.;
Pitout, F.; Schmieder, B.; Régnier, S.; Zouganelis, I.
2019SoPh..294...38B Altcode:
Correction to: Solar Phys (2018)
293:75https://doi.org/10.1007/s11207-018-1278-5 Please find in
this correction document the correct versions of abstract, Sect. 3.1
and Figs. 3 and 12.

---------------------------------------------------------
Title: Exploration of long-period oscillations in an Hα prominence
Authors: Zapiór, M.; Schmieder, B.; Mein, P.; Mein, N.; Labrosse,
N.; Luna, M.
2019A&A...623A.144Z Altcode: 2019arXiv190300230Z
Context. In previous work, we studied a prominence which appeared like
a tornado in a movie made from 193 Å filtergrams obtained with the
Atmospheric Imaging Assembly (AIA) imager aboard the Solar Dynamics
Observatory (SDO). The observations in Hα obtained simultaneously
during two consecutive sequences of one hour with the Multi-channel
Subtractive Double Pass Spectrograph (MSDP) operating at the solar
tower in Meudon showed that the cool plasma inside the tornado was
not rotating around its vertical axis. Furthermore, the evolution
of the Dopplershift pattern suggested the existence of oscillations
of periods close to the time-span of each sequence. Aims:
The aim of the present work is to assemble the two sequences of
Hα observations as a full data set lasting two hours to confirm the
existence of oscillations, and determine their nature. Methods:
After having coaligned the Doppler maps of the two sequences, we use a
Scargle periodogram analysis and cosine fitting to compute the periods
and the phase of the oscillations in the full data set. Results:
Our analysis confirms the existence of oscillations with periods between
40 and 80 min. In the Dopplershift maps, we identify large areas with
strong spectral power. In two of them, the oscillations of individual
pixels are in phase. However, in the top area of the prominence,
the phase is varying slowly, suggesting wave propagation. 
Conclusions: We conclude that the prominence does not oscillate as a
whole structure but exhibits different areas with their own oscillation
periods and characteristics: standing or propagating waves. We discuss
the nature of the standing oscillations and the propagating waves. These
can be interpreted in terms of gravito-acoustic modes and magnetosonic
waves, respectively. Movie attached to Fig. 2 is available at <A
href="https://www.aanda.org/10.1051/0004-6361/201833614/olm">https://www.aanda.org</A>

---------------------------------------------------------
Title: Generalization of the Magnetic Field Configuration of Typical
and Atypical Confined Flares
Authors: Joshi, Navin Chandra; Zhu, Xiaoshuai; Schmieder, Brigitte;
Aulanier, Guillaume; Janvier, Miho; Joshi, Bhuwan; Magara, Tetsuya;
Chandra, Ramesh; Inoue, Satoshi
2019ApJ...871..165J Altcode: 2018arXiv181101228J
Atypical flares cannot be naturally explained with standard models. To
predict such flares, we need to define their physical characteristics,
in particular, their magnetic environment, and identify pairs of
reconnected loops. Here, we present in detail a case study of a confined
flare preceded by flux cancellation that leads to the formation of a
filament. The slow rise of the noneruptive filament favors the growth
and reconnection of overlying loops. The flare is only of C5.0 class
but it is a long duration event. The reason is that it is comprised
of three successive stages of reconnection. A nonlinear force-free
field extrapolation and a magnetic topology analysis allow us to
identify the loops involved in the reconnection process and build a
reliable scenario for this atypical confined flare. The main result
is that a curved magnetic polarity inversion line in active regions
is a key ingredient for producing such atypical flares. A comparison
with previous extrapolations for typical and atypical confined flares
leads us to propose a cartoon for generalizing the concept.

---------------------------------------------------------
Title: Solar Ultraviolet Bursts
Authors: Young, Peter R.; Tian, Hui; Peter, Hardi; Rutten, Robert J.;
Nelson, Chris J.; Huang, Zhenghua; Schmieder, Brigitte; Vissers, Gregal
J. M.; Toriumi, Shin; Rouppe van der Voort, Luc H. M.; Madjarska, Maria
S.; Danilovic, Sanja; Berlicki, Arkadiusz; Chitta, L. P.; Cheung, Mark
C. M.; Madsen, Chad; Reardon, Kevin P.; Katsukawa, Yukio; Heinzel, Petr
2018SSRv..214..120Y Altcode: 2018arXiv180505850Y
The term "ultraviolet (UV) burst" is introduced to describe small,
intense, transient brightenings in ultraviolet images of solar active
regions. We inventorize their properties and provide a definition
based on image sequences in transition-region lines. Coronal signatures
are rare, and most bursts are associated with small-scale, canceling
opposite-polarity fields in the photosphere that occur in emerging flux
regions, moving magnetic features in sunspot moats, and sunspot light
bridges. We also compare UV bursts with similar transition-region
phenomena found previously in solar ultraviolet spectrometry and
with similar phenomena at optical wavelengths, in particular Ellerman
bombs. Akin to the latter, UV bursts are probably small-scale magnetic
reconnection events occurring in the low atmosphere, at photospheric
and/or chromospheric heights. Their intense emission in lines with
optically thin formation gives unique diagnostic opportunities
for studying the physics of magnetic reconnection in the low solar
atmosphere. This paper is a review report from an International Space
Science Institute team that met in 2016-2017.

---------------------------------------------------------
Title: The nature of imploding loops during solar eruptions as
revealed by MHD simulations and AIA observations
Authors: Aulanier, Guillaume; Dudik, Jaroslav; Zucarello, F. P.;
Demoulin, Pascal; Schmieder, Brigitte
2018csc..confE..19A Altcode:
Over the last years AIA revealed the frequent occurence of contracting
loops at the flanks of erupting active regions. Those have often
been interpreted as an evidence of the implosion conjecture that
relates magnetic energy decreases with volume contractions in the Sun's
corona. So as to unveil the physical nature of these features we carried
out observational analyses of two solar eruptions observed with AIA with
different projection angles, which we coupled with new analyses of a
generic zero-beta MHD simulation of an asymmetric eruption driven by the
torus instability, that was not designed for this particular study. The
simulation does display contracting loops in general. And the synthetic
time-slices of the simulation, when rotated to the right projections,
do match the observed ones. But in the simulation these inward motions
are not due to any volume contraction. Instead they are associated
with two large-scale quasi-incompressible coronal-vortices. Those
develop at the flanks of the erupting flux ropes, as most of the
compressive component of the flow is evacuated away by an Alfven wave
in the early stages of the eruption. We argue that this behavior is
merely a magnetic version of the usual pressure-driven formation of
vortex rings in hydrodyanmics. This result implies that during a solar
eruption, the free magnetic-energy from the pre-erupting active-region
is converted not only in the flare and the CME, but is also "lost"
in the generation of these two large-scale coronal vortices.

---------------------------------------------------------
Title: Importance of the Hα Visibility and Projection Effects for
the Interpretation of Prominence Fine-structure Observations
Authors: Gunár, Stanislav; Dudík, Jaroslav; Aulanier, Guillaume;
Schmieder, Brigitte; Heinzel, Petr
2018ApJ...867..115G Altcode:
We construct a new 3D Whole-prominence Fine-structure (WPFS) model based
on a prominence magnetic field configuration designed to qualitatively
approximate the morphology of a quiescent prominence observed on 2010
June 22. The model represents an entire prominence with its numerous
fine structures formed by a prominence plasma located in dips in
the prominence magnetic field. We use the constructed 3D model and
employ a radiative-transfer-based Hα visualization method to analyze
the Hα visibility of prominence fine structures and its effect
on the perceived morphology of observed and modeled prominences. We
qualitatively compare three techniques used for visualization of modeled
prominences—visualizations drawing magnetic dips up to a height of
1 pressure scale height, drawing the full extent of magnetic dips,
and the synthetic Hα visualization—and discuss their suitability
for direct comparison between models and observations of prominences
and filaments. We also discuss the role of visibility of the prominence
fine structures in the estimation of the total height of prominences,
which may indicate the height of pre-erupting flux ropes. This
parameter is critical for the observational determination of the
flux-rope stability. In addition, we employ the WPFS model to assess
the effects caused by a projection of the naturally three-dimensional
and heterogeneous prominences onto a two-dimensional plane of the
sky. We discuss here how the morphological structures of prominences
differ when observed in projections from different viewing angles. We
also discuss the shapes of the dipped magnetic field lines and the
perceived projection of motions of prominence fine structures along
such field lines.

---------------------------------------------------------
Title: Extreme solar storms based on solar magnetic field
Authors: Schmieder, Brigitte
2018JASTP.180...46S Altcode: 2017arXiv170801790S
Many questions have to be answered before understanding the relationship
between the emerging magnetic flux through the solar surface and the
extreme geoeffective events. Which threshold determines the onset
of the eruption? What is the upper limit in energy for a flare? Is
the size of sunspot the only criteria to get extreme solar events? Based on observations of previous solar cycles, and theory, the main
ingredients for getting X ray class flares and large Interplanetary
Corona Mass Ejections e.g. the built up of the electric current in the
corona, are presented such as the existence of magnetic free energy,
magnetic helicity, twist and stress in active regions. The upper limit
of solar flare energy in space research era and the possible chances
to get super-flares and extreme solar events can be predicted using
MHD simulation of coronal mass ejections.

---------------------------------------------------------
Title: Horizontal photospheric flows trigger a filament eruption
Authors: Roudier, T.; Schmieder, B.; Filippov, B.; Chandra, R.;
Malherbe, J. M.
2018A&A...618A..43R Altcode: 2018arXiv180802272R
Context. A large filament composed principally of two sections
erupted sequentially in the southern hemisphere on January 26,
2016. The central, thick part of the northern section was first
lifted up and lead to the eruption of the full filament. This event
was observed in Hα with the Global Oscillation Network Group (GONG)
and Christian Latouche IMageur Solaire (CLIMSO), and in ultraviolet
(UV) with the Atmospheric Imaging Assembly (AIA) imager on board
the Solar Dynamic Observatory (SDO). Aims: The aim of the
paper is to relate the photospheric motions below the filament and
its environment to the eruption of the filament. Methods: An
analysis of the photospheric motions using Solar Dynamic Observatory
Helioseismic and Magnetic Imager (SDO/HMI) continuum images with
the new version of the coherent structure tracking (CST) algorithm
developed to track granules, as well as large-scale photospheric flows,
has been performed. Following velocity vectors, corks migrate towards
converging areas. Results: The supergranule pattern is clearly
visible outside the filament channel but difficult to detect inside
because the modulus of the vector velocity is reduced in the filament
channel, mainly in the magnetized areas. The horizontal photospheric
flows are strong on the west side of the filament channel and oriented
towards the filament. The ends of the filament sections are found
in areas of concentration of corks. Whirled flows are found locally
around the feet. Conclusions: The strong horizontal flows with
an opposite direction to the differential rotation create strong shear
and convergence along the magnetic polarity inversion line (PIL) in the
filament channel. The filament has been destabilized by the converging
flows, which initiate an ascent of the middle section of the filament
until the filament reaches the critical height of the torus instability
inducing, consequently, the eruption. The n decay index indicated an
altitude of 60 Mm for the critical height. It is conjectured that
the convergence along the PIL is due to the large-scale size cells
of convection that transport the magnetic field to their borders. The movies associated to Figs. 1, 2, 4 and 5 are available at <A
href="https://www.aanda.org/10.1051/0004-6361/201832937/olm">https://www.aanda.org</A>.

---------------------------------------------------------
Title: On the Dynamic Nature of a Quiescent Prominence Observed by
IRIS and MSDP Spectrographs
Authors: Ruan, Guiping; Schmieder, Brigitte; Mein, Pierre; Mein,
Nicole; Labrosse, Nicolas; Gunár, Stanislav; Chen, Yao
2018ApJ...865..123R Altcode:
Quiescent solar prominences are generally considered to have a stable
large-scale structure. However, they consist of multiple small-scale
structures that are often significantly dynamic. To understand
the nature of prominence plasma dynamics we use the high spatial,
temporal, and spectral resolution observations obtained by Interface
Region Imaging Spectrograph (IRIS) during a coordinated campaign
with the Multichannel Subtractive Double Pass spectrograph at the
Meudon Solar Tower. Detailed analysis of the IRIS observations of
Mg II lines, including the analysis of Dopplershift and line width
obtained with two different methods (quantile method and Gaussian-fit
method) are discussed in the frame of the dynamic nature of the
structures. Large-scale coherent blueshift and redshift features are
observed in Mg II lines and Hα exhibiting a slow evolution during 1:40
hr of observations. We explain the presence of several significantly
asymmetric peaks in the observed Mg II line profiles by the presence
of several prominence fine structures moving with different velocities
located along the line of sight (LOS). In such a case, the decrease
of the intensity of individual components of the observed spectra
with the distance from the central wavelength can be explained by the
Doppler dimming effect. We show that C II line profiles may be used
to confirm the existence of multi-components along the LOS.

---------------------------------------------------------
Title: Observations of Two Successive EUV Waves and Their Mode
Conversion
Authors: Chandra, Ramesh; Chen, P. F.; Joshi, Reetika; Joshi, Bhuwan;
Schmieder, Brigitte
2018ApJ...863..101C Altcode: 2018arXiv180611350C
In this paper, we present the observations of two successive fast-mode
extreme ultraviolet (EUV) wave events observed on 2016 July 23. Both
fast-mode waves were observed by the Atmospheric Imaging Assembly
instrument on board the Solar Dynamics Observatory satellite, with a
traveling speed of ≈675 and 640 km s-1, respectively. These
two wave events were associated with two filament eruptions and two
GOES M-class solar flares from the NOAA active region 12565, which was
located near the western limb. The EUV waves mainly move toward the
south direction. We observed the interaction of the EUV waves with a
helmet streamer further away to the south. When either or one of the
EUV waves penetrates into the helmet streamer, a slowly propagating wave
with a traveling speed of ≈150 km s-1 is observed along the
streamer. We suggest that the slowly moving waves are slow-mode waves,
and interpret this phenomenon as the magnetohydrodynamic wave-mode
conversion from the fast mode to the slow mode. Furthermore, we observed
several stationary fronts to the north and south of the source region.

---------------------------------------------------------
Title: Signature of flux ropes before and after eruptions: electric
currents in active regions
Authors: Schmieder, Brigitte; Aulanier, Guillaume; Dalmasse, Kévin;
Janvier, Miho; Gilchrist, Stuart; Zhao, Jie; Dudik, Jaroslav
2018cosp...42E3026S Altcode:
Solar observations, nonlinear force-free field extrapolations relying
on these observations, and three-dimensional magnetohydrodynamic (MHD)
models indicate the presence of electric currents in the pre-eruption
state and in the course of eruptions of solar magnetic structures which
are interpreted as flux ropes (sigmoids, filaments, cavities).The MHD
models are able to explain the net currents in active regions by the
existence of strong magnetic shear along the polarity inversion lines,
thus confirming previous observations. The models have also captured
the essence of the behavior of electric currents in active regions
during solar eruptions, predicting current-density increases and
decreases inside flare ribbons and in the interior of expanding flux
ropes, respectively.The observed photospheric current-density maps,
inferred from vector magnetic field observations, exhibit whirling
ribbon patterns similar to the MHD model results, which are interpreted
as the signatures of flux ropes and of quasi-separatrix layers (QSLs)
between the magnetic systems in active regions. We will show how
observations can confirm enhancement of the total current in these
QSLs during the eruptions, and how these observations can be used
to investigate whether current density decrease can be seen at the
footpoints of erupting flux ropes

---------------------------------------------------------
Title: Dynamics in quiescent prominences observed by the IRIS and
MSDP spectrographs
Authors: Gunár, Stanislav; Schmieder, Brigitte; Ruan, Guiping; Mein,
Pierre; Heinzel, Petr
2018cosp...42E1314G Altcode:
Quiescent solar prominences are generally considered to
be stable. However, these prominences consist of a multitude of
small-scale structures or threads that are often significantly
dynamic. To understand the nature of the plasma dynamics we use the
high spatial, temporal and spectral resolution observations obtained
by IRIS during coordinated campaign with the MSDP spectrograph
at the Meudon Solar Tower. Mg II h and k lines observed by IRIS
represent a good diagnostic tool for investigation of the prominence
fine structure dynamics, as they are optically thick under the
prominence conditions. We will present detailed IRIS observations of
Mg II lines. We explain significant asymmetries in the observed Mg II
spectra by the presence of several threads located along the line of
sight with different velocities. In such a case, the decrease of the
intensity of individual components of the observed spectra with the
distance from the central wavelength can be explained by the Doppler
dimming effect. To interpret the observed Mg II profiles in terms
of dynamics we use 1D or 2D radiative transfer models including a
prominence-corona transition region. We also show that the H-alpha
line which is optically thinner than the Mg II doublet is an important
constrain for the radiative transfer radiation modelling.

---------------------------------------------------------
Title: Prominence/Tornado plasma parameters
Authors: Schmieder, Brigitte; Mein, Pierre; Zapior, Maciej; Labrosse,
Nicolas; Lopez Ariste, Arturo
2018cosp...42E3025S Altcode:
We present a comparison of the plasma physical parameters in prominences
and tornadoes using IRIS data and ground based polarimetry measurements
obtained with THEMIS. Mg II lines give a good diagnostics of the
temperature and optical thickness of the structures. The Stokes
parameters from the He D3 line allow to distinguish the behaviour
of the magnetic field in typical prominences and atypical prominences
(e.g. bubbles, eruptive prominence). We concentrate on the Dopplershifts
in a tornado observed in transition region lines and in Halpha. Our
results support the existence of oscillations in tornadoes but not
rotation.A reconstruction of the 3D geometry of a helical prominence
obtained by following the trajectory of kernels yields surprising
results. The loops are shown to be quasi-horizontal structures with
no curvature.We conclude that it is important to take into account the
3D structure of the prominence to study the dynamics of the prominence
plasma.

---------------------------------------------------------
Title: Can 3D whole-prominence fine structure models be used for
assessment of the prominence plasma mass and distribution prior to
the onset of CMEs?
Authors: Gunár, Stanislav; Schmieder, Brigitte; Aulanier, Guillaume;
Anzer, Ulrich; Heinzel, Petr; Mackay, Duncan; Dudik, Jaroslav
2018cosp...42E1316G Altcode:
Two complex 3D models of entire prominences including their numerous
fine structures were recently developed. The first 3D Whole-Prominence
Fine Structure (WPFS) model was developed by Gunár and Mackay. The
second 3D WPFS model was put forward by Gunár, Aulanier, Dudík,
Heinzel, and Schmieder. These 3D prominence models combine simulations
of the 3D magnetic field configuration of an entire prominence with a
detailed description of the prominence plasma. The plasma is located
in magnetic dips in hydrostatic equilibrium and is distributed
along hundreds of fine structures. The assumed prominence plasma
has realistic density and temperature distributions including the
prominence-corona transition region.These 3D WPFS models allow us
to study the distribution and the mass of the prominence plasma
contained in prominence magnetic field configurations. These can
be crucial during the onset and early evolution of CMEs. Moreover,
prominence plasma represents a bulk of the material ejected by CMEs
into the interplanetary space. Here, we investigate the potential of
using the 3D WPFS models for assessment of the role the prominence
plasma plays in the initiation and evolution of CMEs.

---------------------------------------------------------
Title: Statistical Analysis of Solar Events Associated with Storm
Sudden Commencements over One Year of Solar Maximum During Cycle 23:
Propagation from the Sun to the Earth and Effects
Authors: Bocchialini, K.; Grison, B.; Menvielle, M.; Chambodut,
A.; Cornilleau-Wehrlin, N.; Fontaine, D.; Marchaudon, A.; Pick, M.;
Pitout, F.; Schmieder, B.; Régnier, S.; Zouganelis, I.
2018SoPh..293...75B Altcode: 2018arXiv180307593B
Taking the 32 storm sudden commencements (SSCs) listed by the
International Service of Geomagnetic Indices (ISGI) of the Observatory
de l'Ebre during 2002 (solar activity maximum in Cycle 23) as a starting
point, we performed a multi-criterion analysis based on observations
(propagation time, velocity comparisons, sense of the magnetic
field rotation, radio waves) to associate them with solar sources,
identified their effects in the interplanetary medium, and looked at
the response of the terrestrial ionized and neutral environment. We
find that 28 SSCs can be related to 44 coronal mass ejections (CMEs),
15 with a unique CME and 13 with a series of multiple CMEs, among which
19 (68%) involved halo CMEs. Twelve of the 19 fastest CMEs with speeds
greater than 1000 km s−1 are halo CMEs. For the 44 CMEs,
including 21 halo CMEs, the corresponding X-ray flare classes are: 3
X-class, 19 M-class, and 22 C-class flares. The probability for an SSC
to occur is 75% if the CME is a halo CME. Among the 500, or even more,
front-side, non-halo CMEs recorded in 2002, only 23 could be the source
of an SSC, i.e. 5%. The complex interactions between two (or more)
CMEs and the modification of their trajectories have been examined
using joint white-light and multiple-wavelength radio observations. The
detection of long-lasting type IV bursts observed at metric-hectometric
wavelengths is a very useful criterion for the CME-SSC events
association. The events associated with the most depressed Dst values
are also associated with type IV radio bursts. The four SSCs associated
with a single shock at L1 correspond to four radio events exhibiting
characteristics different from type IV radio bursts. The solar-wind
structures at L1 after the 32 SSCs are 12 magnetic clouds (MCs), 6
interplanetary coronal mass ejections (ICMEs) without an MC structure,
4 miscellaneous structures, which cannot unambiguously be classified
as ICMEs, 5 corotating or stream interaction regions (CIRs/SIRs), one
CIR caused two SSCs, and 4 shock events; note than one CIR caused two
SSCs. The 11 MCs listed in 3 or more MC catalogs covering the year 2002
are associated with SSCs. For the three most intense geomagnetic storms
(based on Dst minima) related to MCs, we note two sudden increases
of the Dst, at the arrival of the sheath and the arrival of the MC
itself. In terms of geoeffectiveness, the relation between the CME
speed and the magnetic-storm intensity, as characterized using the Dst
magnetic index, is very complex, but generally CMEs with velocities at
the Sun larger than 1000 km s−1 have larger probabilities
to trigger moderate or intense storms. The most geoeffective events are
MCs, since 92% of them trigger moderate or intense storms, followed
by ICMEs (33%). At best, CIRs/SIRs only cause weak storms. We show
that these geoeffective events (ICMEs or MCs) trigger an increased and
combined auroral kilometric radiation (AKR) and non-thermal continuum
(NTC) wave activity in the magnetosphere, an enhanced convection in
the ionosphere, and a stronger response in the thermosphere. However,
this trend does not appear clearly in the coupling functions, which
exhibit relatively weak correlations between the solar-wind energy
input and the amplitude of various geomagnetic indices, whereas the
role of the southward component of the solar-wind magnetic field is
confirmed. Some saturation appears for Dst values &lt;−100 nT on
the integrated values of the polar and auroral indices.

---------------------------------------------------------
Title: Solar Active Region Electric Currents Before and During
Eruptive Flares
Authors: Schmieder, Brigitte; Aulanier, Guillaume
2018GMS...235..391S Altcode: 2019arXiv190304050S
This chapter discusses electric currents in the preeruption state and in
the course of eruptions of solar magnetic structures, using information
from solar observations, nonlinear force-free field extrapolations
relying on these observations, and three-dimensional magnetohydrodynamic
(MHD) models. The discussion addresses the issue of neutralized versus
nonneutralized currents in active regions and concludes that MHD models
are able to explain nonneutralized currents in active regions by the
existence of strong magnetic shear along the polarity inversion lines,
thus confirming previous observations that already contained this
result. The models have also captured the essence of the behavior of
electric currents in active regions during solar eruptions, predicting
current-density increases and decreases inside flare ribbons and
in the interior of expanding flux ropes, respectively. The observed
photospheric current-density maps, inferred from vector magnetic field
observations, exhibit whirling ribbon patterns similar to the MHD
model results, which are interpreted as the signatures of flux ropes
and of quasi-separatrix layers (QSLs) between the magnetic systems in
active regions. Enhancement of the total current in these QSLs during
the eruptions and decreasing current densities at the footpoint of
erupting flux ropes, has been confirmed in the observations.

---------------------------------------------------------
Title: Kinematic and magnetic coherent structures in solar and
stellar turbulence
Authors: Chian, Abraham C. -L.; Miranda, Rodrigo A.; Rempel, Erico L.;
Schmieder, Brigitte
2018IAUS..340..285C Altcode:
We show that on-off intermittency in solar and stellar cycles is a
result of amplitude-phase synchronization in multiscale interactions
in solar/stellar dynamos or magnetorotational instability which leads
to the formation of kinematic and magnetic coherent structures, and
the novel techniques of Lagrangian coherent structures can detect
transport barriers and vortices such as magnetic flux tubes/ropes in
solar and stellar turbulence with high accuracy.

---------------------------------------------------------
Title: Geoeffective events through solar cycles
Authors: Schmieder, Brigitte; Aulanier, Guillaume
2018IAUS..340..255S Altcode:
Extreme solar storms are well known in the historical databases. Since
the modern era, it has been possible to associate clearly
geomagnetic disturbances with solar events (flares, SEP, CMEs). In
the recent solar cycles the geoeffective events (number and strength)
are decreasing. As an example, in the 2002 maximum activity year,
we present how many flares, and CMEs were geoeffective. Based on
observations and simulations, we discuss on the size of sunspots and
the field strength to get more energetic flares (&gt; 1032
ergs) in the near future.

---------------------------------------------------------
Title: Large-amplitude Longitudinal Oscillations Triggered by the
Merging of Two Solar Filaments: Observations and Magnetic Field
Analysis
Authors: Luna, M.; Su, Y.; Schmieder, B.; Chandra, R.; Kucera, T. A.
2017ApJ...850..143L Altcode: 2017arXiv171101038L
We follow the eruption of two related intermediate filaments observed in
Hα (from GONG) and EUV (from Solar Dynamics Observatory SDO/Atmospheric
Imaging assembly AIA) and the resulting large-amplitude longitudinal
oscillations of the plasma in the filament channels. The events occurred
in and around the decayed active region AR12486 on 2016 January 26. Our
detailed study of the oscillation reveals that the periods of the
oscillations are about one hour. In Hα, the period decreases with
time and exhibits strong damping. The analysis of 171 Å images shows
that the oscillation has two phases: an initial long-period phase and
a subsequent oscillation with a shorter period. In this wavelength,
the damping appears weaker than in Hα. The velocity is the largest
ever detected in a prominence oscillation, approximately 100 {km}
{{{s}}}-1. Using SDO/HMI magnetograms, we reconstruct
the magnetic field of the filaments, modeled as flux ropes by using
a flux-rope insertion method. Applying seismological techniques,
we determine that the radii of curvature of the field lines in which
cool plasma is condensed are in the range 75-120 Mm, in agreement with
the reconstructed field. In addition, we infer a field strength of
≥7 to 30 Gauss, depending on the electron density assumed, that
is also in agreement with the values from the reconstruction (8-20
Gauss). The poloidal flux is zero and the axis flux is on the order
of 1020 to 1021 Mx, confirming the high shear
existing even in a non-active filament.

---------------------------------------------------------
Title: Statistical analysis of solar events associated with SSC over
year of solar maximum during cycle 23: 2. Characterisation on the
Sun-Earth path - Geoeffectiveness
Authors: Cornilleau-Wehrlin, N.; Bocchialini, K.; Menvielle, M.;
Fontaine, D.; Grison, B.; Marchaudon, A.; Pick, M.; Pitout, F.;
Schmieder, B.; Regnier, S.; Zouganelis, Y.; Chambodut, A.
2017AGUFMSH31A2712C Altcode:
Taking the 32 sudden storm commencements (SSC) listed by the observatory
de l'Ebre / ISGI over the year 2002 (maximal solar activity) as a
starting point, we performed a statistical analysis of the related
solar sources, solar wind signatures, and terrestrial responses. For
each event, we characterized and identified, as far as possible, (i)
the sources on the Sun (Coronal Mass Ejections -CME-), with the help
of a series of criteria (velocities, drag coefficient, radio waves,
magnetic field polarity), as well as (ii) the structure and properties
in the interplanetary medium, at L1, of the event associated to the SSC:
magnetic clouds -MC-, non-MC interplanetary coronal mass ejections
-ICME-, co-rotating/stream interaction regions -SIR/CIR-, shocks
only and unclear events that we call "miscellaneous" events. The
geoeffectiveness of the events, classified by category at L1, is
analysed by their signatures in the Earth ionized (magnetosphere
and ionosphere) and neutral (thermosphere) environments, using a
broad set of in situ, remote and ground based instrumentation. The
role of the presence of a unique or of a multiple source at the Sun,
of its nature, halo or non halo CME, is also discussed. The set of
observations is statistically analyzed so as to evaluate and compare
the geoeffectiveness of the events. The results obtained for this
set of geomagnetic storms started by SSCs is compared to the overall
statistics of year 2002, relying on already published catalogues of
events, allowing assessing the relevance of our approach ; for instance
all the 12 well identified Magnetic Clouds of 2002 give rise to SSCs.

---------------------------------------------------------
Title: Statistical Analysis of Solar Events Associated with SSC over
Year of Solar Maximum during Cycle 23: 1. Identification of Related
Sun-Earth Events
Authors: Grison, B.; Bocchialini, K.; Menvielle, M.; Chambodut,
A.; Cornilleau-Wehrlin, N.; Fontaine, D.; Marchaudon, A.; Pick, M.;
Pitout, F.; Schmieder, B.; Regnier, S.; Zouganelis, Y.
2017AGUFMSH31A2711G Altcode:
Taking the 32 sudden storm commencements (SSC) listed by the observatory
de l'Ebre / ISGI over the year 2002 (maximal solar activity) as a
starting point, we performed a statistical analysis of the related
solar sources, solar wind signatures, and terrestrial responses. For
each event, we characterized and identified, as far as possible,
(i) the sources on the Sun (Coronal Mass Ejections -CME-), with the
help of a series of herafter detailed criteria (velocities, drag
coefficient, radio waves, polarity), as well as (ii) the structure
and properties in the interplanetary medium, at L1, of the event
associated to the SSC: magnetic clouds -MC-, non-MC interplanetary
coronal mass ejections -ICME-, co-rotating/stream interaction regions
-SIR/CIR-, shocks only and unclear events that we call "miscellaneous"
events. The categorization of the events at L1 is made on published
catalogues. For each potential CME/L1 event association we compare
the velocity observed at L1 with the one observed at the Sun and the
estimated balistic velocity. Observations of radio emissions (Type II,
Type IV detected from the ground and /or by WIND) associated to the CMEs
make the solar source more probable. We also compare the polarity of
the magnetic clouds with the hemisphere of the solar source. The drag
coefficient (estimated with the drag-based model) is calculated for
each potential association and it is compared to the expected range
values. We identified a solar source for 26 SSC related events. 12
of these 26 associations match all criteria. We finally discuss the
difficulty to perform such associations.

---------------------------------------------------------
Title: Reconstruction of a helical prominence in 3D from IRIS spectra
and images
Authors: Schmieder, B.; Zapiór, M.; López Ariste, A.; Levens, P.;
Labrosse, N.; Gravet, R.
2017A&A...606A..30S Altcode: 2017arXiv170608078S
Context. Movies of prominences obtained by space instruments e.g. the
Solar Optical Telescope (SOT) aboard the Hinode satellite and the
Interface Region Imaging Spectrograph (IRIS) with high temporal
and spatial resolution revealed the tremendous dynamical nature
of prominences. Knots of plasma belonging to prominences appear
to travel along both vertical and horizontal thread-like loops,
with highly dynamical nature. Aims: The aim of the paper
is to reconstruct the 3D shape of a helical prominence observed
over two and a half hours by IRIS. Methods: From the IRIS
Mg II k spectra we compute Doppler shifts of the plasma inside
the prominence and from the slit-jaw images (SJI) we derive the
transverse field in the plane of the sky. Finally we obtain the
velocity vector field of the knots in 3D. Results.We reconstruct the
real trajectories of nine knots travelling along ellipses. 
Conclusions: The spiral-like structure of the prominence observed
in the plane of the sky is mainly due to the projection effect of
long arches of threads (up to 8 × 104 km). Knots run
along more or less horizontal threads with velocities reaching 65 km
s-1. The dominant driving force is the gas pressure. Movies associated to Figs. 1, 9, 10, and 13 are available at <A
href="http://www.aanda.org/10.1051/0004-6361/201730839/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Comparing UV/EUV line parameters and magnetic field in a
quiescent prominence with tornadoes
Authors: Levens, P. J.; Labrosse, N.; Schmieder, B.; López Ariste,
A.; Fletcher, L.
2017A&A...607A..16L Altcode: 2017arXiv170804606L
Context. Understanding the relationship between plasma and the
magnetic field is important for describing and explaining the
observed dynamics of solar prominences. Aims: We determine
if a close relationship can be found between plasma and magnetic
field parameters, measured at high resolution in a well-observed
prominence. Methods: A prominence observed on 15 July 2014 by
the Interface Region Imaging Spectrograph (IRIS), Hinode, the Solar
Dynamics Observatory (SDO), and the Télescope Héliographique pour
l'Étude du Magnétisme et des Instabilités Solaires (THEMIS) is
selected. We perform a robust co-alignment of data sets using a 2D
cross-correlation technique. Magnetic field parameters are derived
from spectropolarimetric measurements of the He I D3 line
from THEMIS. Line ratios and line-of-sight velocities from the Mg II h
and k lines observed by IRIS are compared with magnetic field strength,
inclination, and azimuth. Electron densities are calculated using Fe xii
line ratios from the Hinode Extreme-ultraviolet Imaging Spectrometer,
which are compared to THEMIS and IRIS data. Results: We find
Mg II k/h ratios of around 1.4 everywhere, similar to values found
previously in prominences. Also, the magnetic field is strongest (
30 G) and predominantly horizontal in the tornado-like legs of the
prominence. The k3 Doppler shift is found to be between
±10 km s-1 everywhere. Electron densities at a temperature
of 1.5 × 106 K are found to be around 109
cm-3. No significant correlations are found between the
magnetic field parameters and any of the other plasma parameters
inferred from spectroscopy, which may be explained by the large
differences in the temperatures of the lines used in this study. 
Conclusions: This is the first time that a detailed statistical study of
plasma and magnetic field parameters has been performed at high spatial
resolution in a prominence. Our results provide important constraints
on future models of the plasma and magnetic field in these structures.

---------------------------------------------------------
Title: Slippage of Jets Explained by the Magnetic Topology of NOAA
Active Region 12035
Authors: Joshi, R.; Schmieder, B.; Chandra, R.; Aulanier, G.;
Zuccarello, F. P.; Uddin, W.
2017SoPh..292..152J Altcode: 2017arXiv170902791J
We present the investigation of 11 recurring solar jets that originated
from two different sites (site 1 and site 2) close to each other (≈11
Mm) in NOAA active region (AR) 12035 during 15 - 16 April 2014. The
jets were observed by the Atmospheric Imaging Assembly (AIA) telescope
on board the Solar Dynamics Observatory (SDO) satellite. Two jets
were observed by the telescope of the Aryabhatta Research Institute of
Observational Sciences (ARIES), Nainital, India, in Hα . On 15 April,
flux emergence is strong in site 1, while on 16 April, flux emergence
and cancellation mechanisms are involved in both sites. The jets of
both sites have parallel trajectories and move to the south with a
speed between 100 and 360 km s−1. The jets of site 2
occurred during the second day have a tendency to move toward the
jets of site 1 and merge with them. We conjecture that the slippage
of the jets could be explained by the complex topology of the region,
which included a few low-altitude null points and many quasi-separatrix
layers (QSLs), which could intersect with one another.

---------------------------------------------------------
Title: Prominence and tornado dynamics observed with IRIS and THEMIS
Authors: Schmieder, Brigitte; Levens, Peter; Labrosse, Nicolas; Mein,
Pierre; Lopez Ariste, Arturo; Zapior, Maciek
2017SPD....4820104S Altcode:
Several prominences were observed during campaigns in September 2013 and
July 2014 with the IRIS spectrometer and the vector magnetograph THEMIS
(Tenerife). SDO/AIA and IRIS provided images and spectra of prominences
and tornadoes corresponding to different physical conditions of the
transition region between the cool plasma and the corona. The vector
magnetic field was derived from THEMIS observations by using the He
D3 depolarisation due to the magnetic field. The inversion code (PCA)
takes into account the Hanle and Zeeman effects and allows us to compute
the strength and the inclination of the magnetic field which is shown
to be mostly horizontal in prominences as well as in tornadoes. Movies
from SDO/AIA in 304 A and Hinode/SOT in Ca II show the highly dynamic
nature of the fine structures. From spectra in Mg II and Si IV lines
provided by IRIS and H-alpha observed by the Multi-channel Subtractive
Double Pass (MSDP) spectrograph in the Meudon Solar Tower we derived
the Doppler shifts of the fine structures and reconstructed the 3D
structure of tornadoes. We conclude that the apparent rotation of AIA
tornadoes is due to large-scale quasi-periodic oscillations of the
plasma along more or less horizontal magnetic structures.

---------------------------------------------------------
Title: Expanding and Contracting Coronal Loops as Evidence of Vortex
Flows Induced by Solar Eruptions
Authors: Dudík, J.; Zuccarello, F. P.; Aulanier, G.; Schmieder, B.;
Démoulin, P.
2017ApJ...844...54D Altcode: 2017arXiv170604783D
Eruptive solar flares were predicted to generate large-scale vortex
flows at both sides of the erupting magnetic flux rope. This process
is analogous to a well-known hydrodynamic process creating vortex
rings. The vortices lead to advection of closed coronal loops located
at the peripheries of the flaring active region. Outward flows are
expected in the upper part and returning flows in the lower part of the
vortex. Here, we examine two eruptive solar flares, the X1.1-class flare
SOL2012-03-05T03:20 and the C3.5-class SOL2013-06-19T07:29. In both
flares, we find that the coronal loops observed by the Atmospheric
Imaging Assembly in its 171 Å, 193 Å, or 211 Å passbands show
coexistence of expanding and contracting motions, in accordance with
the model prediction. In the X-class flare, multiple expanding and
contracting loops coexist for more than 35 minutes, while in the C-class
flare, an expanding loop in 193 Å appears to be close by and cotemporal
with an apparently imploding loop arcade seen in 171 Å. Later, the 193
Å loop also switches to contraction. These observations are naturally
explained by vortex flows present in a model of eruptive solar flares.

---------------------------------------------------------
Title: Two-Step Filament Eruption During 14 - 15 March 2015
Authors: Chandra, R.; Filippov, B.; Joshi, R.; Schmieder, B.
2017SoPh..292...81C Altcode: 2017arXiv170408860C
We present here an interesting two-step filament eruption during 14 -
15 March 2015. The filament was located in NOAA AR 12297 and associated
with a halo Coronal Mass Ejection (CME). We use observations from the
Atmospheric Imaging Assembly (AIA) and Heliospheric Magnetic Imager
(HMI) instruments onboard the Solar Dynamics Observatory (SDO),
and from the Solar and Heliospheric Observatory (SOHO) Large Angle
and Spectrometric Coronagraph (LASCO). We also use Hα data from the
Global Oscillation Network Group (GONG) telescope and the Kanzelhoehe
Solar Observatory. The filament shows a first step eruption on 14
March 2015 and it stops its rise at a projected altitude ≈125 Mm
on the solar disk. It remains at this height for ≈12 hrs. Finally
it erupts on 15 March 2015 and produces a halo CME. We also find jet
activity in the active region during both days, which could help the
filament de-stabilization and eruption. The decay index is calculated
to understand this two-step eruption. The eruption could be due to the
presence of successive instability-stability-instability zones as the
filament is rising.

---------------------------------------------------------
Title: Transition from eruptive to confined flares in the same
active region
Authors: Zuccarello, F. P.; Chandra, R.; Schmieder, B.; Aulanier,
G.; Joshi, R.
2017A&A...601A..26Z Altcode: 2017arXiv170202477Z
Context. Solar flares are sudden and violent releases of magnetic
energy in the solar atmosphere that can be divided into two classes:
eruptive flares, where plasma is ejected from the solar atmosphere
resulting in a coronal mass ejection (CME), and confined flares,
where no CME is associated with the flare. Aims: We present
a case study showing the evolution of key topological structures,
such as spines and fans, which may determine the eruptive versus
non-eruptive behavior of the series of eruptive flares followed by
confined flares, which all originate from the same site. 
Methods: To study the connectivity of the different flux domains
and their evolution, we compute a potential magnetic field model of
the active region. Quasi-separatrix layers are retrieved from the
magnetic field extrapolation. Results: The change in behavior
of the flares from one day to the next - from eruptive to confined -
can be attributed to the change in orientation of the magnetic field
below the fan with respect to the orientation of the overlaying spine
rather than an overall change in the stability of the large-scale
field. Conclusions: Flares tend to be more confined when the
field that supports the filament and the overlying field gradually
becomes less anti-parallel as a direct result of changes in the
photospheric flux distribution, being themselves driven by continuous
shearing motions of the different magnetic flux concentrations. Movies associated to Figs. 2, 3, and 5 are available at <A
href="http://www.aanda.org/10.1051/0004-6361/201629836/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Solar filament eruptions and their physical role in triggering
Coronal Mass Ejections
Authors: Schmieder, Brigitte
2017EGUGA..19.2767S Altcode:
Both filaments and CMEs have been related to twisted magnetic
fields. Therefore, nearly all the MHD CME models include a twisted
flux tube, called a flux rope. Either the flux rope is present before
the eruption, or it is built up by reconnection of a sheared arcade
from the beginning of the eruption. Combining observations of SDO
and STEREO and CME theoretical models we have investigated different
mechanisms initiating eruptions : new emergence of flux, shear motions,
and dispersion of the external magnetic field, and/or reconnection
of field lines below or above the flux rope. Their impacts is mainly
to break the overlying magnetic tension and/or to favor the rise of
the flux rope until the torus instability. We used the MHD simulation
(OHM) as a tool to explain the different phases of eruptive flares:
e.g. postflare loops. The prediction of enhancement of electric current
during reconnection is confirmed in the observations.

---------------------------------------------------------
Title: Statistical analysis of solar events associated with SSC over
one year of solar maximum during cycle 23: propagation and effects
from the Sun to the Earth
Authors: Cornilleau-Wehrlin, Nicole; Bocchialini, Karine; Menvielle,
Michel; Chambodut, Aude; Fontaine, Dominique; Grison, Benjamin;
Marchaudon, Aurélie; Pick, Monique; Pitout, Frédéric; Schmieder,
Brigitte; Régnier, Stéphane; Zouganelis, Yannis
2017EGUGA..19.3689C Altcode:
Taking the 32 sudden storm commencements (SSC) listed by the observatory
de l'Ebre / ISGI over the year 2002 (maximal solar activity) as a
starting point, we performed a statistical analysis of the related
solar sources, solar wind signatures, and terrestrial responses. For
each event, we characterized and identified, as far as possible,
(i) the sources on the Sun (Coronal Mass Ejections -CME-), with the
help of a series of criteria (velocities, drag coefficient, radio
waves, helicity), as well as (ii) the structure and properties in the
interplanetary medium, at L1, of the event associated to the SSC:
magnetic clouds -MC-, non-MC interplanetary coronal mass ejections
-ICME-, co-rotating/stream interaction regions -SIR/CIR-, shocks only
and unclear events that we call "miscellaneous" events. The observed
Sun-to-Earth travel times are compared to those estimated using existing
simple models of propagation in the interplanetary medium. This
comparison is used to statistically assess performances of various
models. The geoeffectiveness of the events, classified by category at
L1, is analysed by their signatures in the Earth ionized (magnetosphere
and ionosphere) and neutral (thermosphere) environments, using a
broad set of in situ, remote and ground based instrumentation. The
role of the presence of a unique or of a multiple source at the Sun,
of its nature, halo or non halo CME, is also discussed. The set of
observations is statistically analyzed so as to evaluate and compare
the geoeffectiveness of the events. The results obtained for this
set of geomagnetic storms started by SSCs is compared to the overall
statistics of year 2002, relying on already published catalogues of
events, allowing assessing the relevance of our approach (for instance
the all 12 well identified Magnetic Clouds of 2002 give rise to SSCs).

---------------------------------------------------------
Title: Vortex and Sink Flows in Eruptive Flares as a Model for
Coronal Implosions
Authors: Zuccarello, F. P.; Aulanier, G.; Dudík, J.; Démoulin, P.;
Schmieder, B.; Gilchrist, S. A.
2017ApJ...837..115Z Altcode: 2017arXiv170200199Z
Eruptive flares are sudden releases of magnetic energy that
involve many phenomena, several of which can be explained by the
standard 2D flare model and its realizations in 3D. We analyze a 3D
magnetohydrodynamics simulation, in the framework of this model, that
naturally explains the contraction of coronal loops in the proximity
of the flare sites, as well as the inflow toward the region above the
cusp-shaped loops. We find that two vorticity arcs located along the
flanks of the erupting magnetic flux rope are generated as soon as the
eruption begins. The magnetic arcades above the flux rope legs are then
subjected to expansion, rotation, or contraction depending on which
part of the vortex flow advects them. In addition to the vortices,
an inward-directed magnetic pressure gradient exists in the current
sheet below the magnetic flux rope. It results in the formation of a
sink that is maintained by reconnection. We conclude that coronal loop
apparent implosions observed during eruptive flares are the result
of hydromagnetic effects related to the generation of vortex and sink
flows when a flux rope moves in a magnetized environment.

---------------------------------------------------------
Title: Blowout jets and impulsive eruptive flares in a bald-patch
topology
Authors: Chandra, R.; Mandrini, C. H.; Schmieder, B.; Joshi, B.;
Cristiani, G. D.; Cremades, H.; Pariat, E.; Nuevo, F. A.; Srivastava,
A. K.; Uddin, W.
2017A&A...598A..41C Altcode: 2016arXiv161001918C
Context. A subclass of broad extreme ultraviolet (EUV) and X-ray jets,
called blowout jets, have become a topic of research since they could
be the link between standard collimated jets and coronal mass ejections
(CMEs). Aims: Our aim is to understand the origin of a series of
broad jets, some of which are accompanied by flares and associated with
narrow and jet-like CMEs. Methods: We analyze observations of
a series of recurrent broad jets observed in AR 10484 on 21-24 October
2003. In particular, one of them occurred simultaneously with an M2.4
flare on 23 October at 02:41 UT (SOLA2003-10-23). Both events were
observed by the ARIES Hα Solar Tower-Telescope, TRACE, SOHO, and RHESSI
instruments. The flare was very impulsive and followed by a narrow
CME. A local force-free model of AR 10484 is the basis to compute its
topology. We find bald patches (BPs) at the flare site. This BP topology
is present for at least two days before to events. Large-scale field
lines, associated with the BPs, represent open loops. This is confirmed
by a global potential free source surface (PFSS) model. Following
the brightest leading edge of the Hα and EUV jet emission, we can
temporarily associate these emissions with a narrow CME. Results:
Considering their characteristics, the observed broad jets appear to
be of the blowout class. As the most plausible scenario, we propose
that magnetic reconnection could occur at the BP separatrices forced
by the destabilization of a continuously reformed flux rope underlying
them. The reconnection process could bring the cool flux-rope material
into the reconnected open field lines driving the series of recurrent
blowout jets and accompanying CMEs. Conclusions: Based on
a model of the coronal field, we compute the AR 10484 topology at
the location where flaring and blowout jets occurred from 21 to 24
October 2003. This topology can consistently explain the origin of
these events. The movie associated to Fig. 1 is available at <A
href="http://www.aanda.org/10.1051/0004-6361/201628984/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Observational Evidence of Magnetic Reconnection for
Brightenings and Transition Region Arcades in IRIS Observations
Authors: Zhao, Jie; Schmieder, Brigitte; Li, Hui; Pariat, Etienne;
Zhu, Xiaoshuai; Feng, Li; Grubecka, Michalina
2017ApJ...836...52Z Altcode: 2017arXiv170108356Z
By using a new method of forced-field extrapolation, we study the
emerging flux region AR11850 observed by the Interface Region Imaging
Spectrograph and Solar Dynamical Observatory. Our results suggest
that the bright points (BPs) in this emerging region exhibit responses
in lines formed from the upper photosphere to the transition region,
which have relatively similar morphologies. They have an oscillation
of several minutes according to the Atmospheric Imaging Assembly
data at 1600 and 1700 Å. The ratio between the BP intensities
measured in 1600 and 1700 Å filtergrams reveals that these BPs are
heated differently. Our analysis of the Helioseismic and Magnetic
Imager vector magnetic field and the corresponding topology in AR11850
indicates that the BPs are located at the polarity inversion line and
most of them are related to magnetic reconnection or cancelation. The
heating of the BPs might be different due to different magnetic
topology. We find that the heating due to the magnetic cancelation
would be stronger than the case of bald patch reconnection. The
plasma density rather than the magnetic field strength could play a
dominant role in this process. Based on physical conditions in the
lower atmosphere, our forced-field extrapolation shows consistent
results between the bright arcades visible in slit-jaw image 1400 Å
and the extrapolated field lines that pass through the bald patches. It
provides reliable observational evidence for testing the mechanism
of magnetic reconnection for the BPs and arcades in the emerging flux
region, as proposed in simulation studies.

---------------------------------------------------------
Title: Successive Magnetic Reconnections Observed during Sympathetic
Eruptions
Authors: Chandra Joshi, Navin; Schmieder, Brigitte; Magara, Tetsuya;
Guo, Yang; Aulanier, Guillaume
2017psio.confE.120C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Hα Doppler shifts in a tornado in the solar corona
Authors: Schmieder, B.; Mein, P.; Mein, N.; Levens, P. J.; Labrosse,
N.; Ofman, L.
2017A&A...597A.109S Altcode: 2016arXiv161202232S
Context. High resolution movies in 193 Å from the Atmospheric
Imaging Assembly (AIA) on the Solar Dynamic Observatory (SDO)
show apparent rotation in the leg of a prominence observed during
a coordinated campaign. Such structures are commonly referred to as
tornadoes. Time-distance intensity diagrams of the AIA data show the
existence of oscillations suggesting that the structure is rotating. Aims: The aim of this paper is to understand if the cool plasma
at chromospheric temperatures inside the tornado is rotating around
its central axis. Methods: The tornado was also observed in Hα
with a cadence of 30 s by the MSDP spectrograph, operating at the Solar
Tower in Meudon. The MSDP provides sequences of simultaneous spectra
in a 2D field of view from which a cube of Doppler velocity maps is
retrieved. Results: The Hα Doppler maps show a pattern with
alternatively blueshifted and redshifted areas of 5 to 10” wide. Over
time the blueshifted areas become redshifted and vice versa, with
a quasi-periodicity of 40 to 60 min. Weaker amplitude oscillations
with periods of 4 to 6 min are superimposed onto these large period
oscillations. Conclusions: The Doppler pattern observed in
Hα cannot be interpreted as rotation of the cool plasma inside the
tornado. The Hα velocity observations give strong constraints on the
possible interpretations of the AIA tornado.

---------------------------------------------------------
Title: Heating Mechanisms in the Low Solar Atmosphere through Magnetic
Reconnection in Current Sheets
Authors: Ni, Lei; Lin, Jun; Roussev, Ilia I.; Schmieder, Brigitte
2016ApJ...832..195N Altcode: 2016arXiv161101746N
We simulate several magnetic reconnection processes in the low solar
chromosphere/photosphere; the radiation cooling, heat conduction
and ambipolar diffusion are all included. Our numerical results
indicate that both the high temperature (≳8 × 104 K)
and low temperature (∼104 K) magnetic reconnection events
can happen in the low solar atmosphere (100-600 km above the solar
surface). The plasma β controlled by plasma density and magnetic
fields is one important factor to decide how much the plasma can be
heated up. The low temperature event is formed in a high β magnetic
reconnection process, Joule heating is the main mechanism to heat
plasma and the maximum temperature increase is only several thousand
Kelvin. The high temperature explosions can be generated in a low β
magnetic reconnection process, slow and fast-mode shocks attached
at the edges of the well developed plasmoids are the main physical
mechanisms to heat the plasma from several thousand Kelvin to over 8 ×
104 K. Gravity in the low chromosphere can strongly hinder
the plasmoid instability and the formation of slow-mode shocks in a
vertical current sheet. Only small secondary islands are formed; these
islands, however, are not as well developed as those in the horizontal
current sheets. This work can be applied to understand the heating
mechanism in the low solar atmosphere and could possibly be extended
to explain the formation of common low temperature Ellerman bombs
(∼104 K) and the high temperature Interface Region Imaging
Spectrograph (IRIS) bombs (≳8 × 104) in the future.

---------------------------------------------------------
Title: Height formation of bright points observed by IRIS in Mg II
line wings during flux emergence
Authors: Grubecka, M.; Schmieder, B.; Berlicki, A.; Heinzel, P.;
Dalmasse, K.; Mein, P.
2016A&A...593A..32G Altcode:
Context. A flux emergence in the active region AR 111850 was observed
on September 24, 2013 with the Interface Region Imaging Spectrograph
(IRIS). Many bright points are associated with the new emerging flux
and show enhancement brightening in the UV spectra. Aims:
The aim of this work is to compute the altitude formation of the
compact bright points (CBs) observed in Mg II lines in the context
of searching Ellerman bombs (EBs). Methods: IRIS provided two
large dense rasters of spectra in Mg II h and k lines, Mg II triplet,
C II and Si IV lines covering all the active region and slit jaws in
the two bandpasses (1400 Å and 2796 Å) starting at 11:44 UT and
15:39 UT, and lasting 20 min each. Synthetic profiles of Mg II and
Hα lines are computed with non-local thermodynamic equlibrium (NLTE)
radiative transfer treatment in 1D solar atmosphere model including
a hotspot region defined by three parameters: temperature, altitude,
and width. Results: Within the two IRIS rasters, 74 CBs are
detected in the far wings of the Mg II lines (at +/-1 Å and 3.5
Å). Around 10% of CBs have a signature in Si IV and CII. NLTE models
with a hotspot located in the low atmosphere were found to fit a sample
of Mg II profiles in CBs. The Hα profiles computed with these Mg II
CB models are consistent with typical EB profiles observed from ground
based telescopes e.g. THEMIS. A 2D NLTE modelling of fibrils (canopy)
demonstrates that the Mg II line centres can be significantly affected
but not the peaks and the wings of Mg II lines. Conclusions:
We conclude that the bright points observed in Mg II lines can be
formed in an extended domain of altitudes in the photosphere and/or
the chromosphere (400 to 750 km). Our results are consistent with the
theory of heating by Joule dissipation in the atmosphere produced by
magnetic field reconnection during flux emergence.

---------------------------------------------------------
Title: Magnetic Field in Atypical Prominence Structures: Bubble,
Tornado, and Eruption
Authors: Levens, P. J.; Schmieder, B.; López Ariste, A.; Labrosse,
N.; Dalmasse, K.; Gelly, B.
2016ApJ...826..164L Altcode: 2016arXiv160505964L
Spectropolarimetric observations of prominences have been obtained with
the THEMIS telescope during four years of coordinated campaigns. Our aim
is now to understand the conditions of the cool plasma and magnetism
in “atypical” prominences, namely when the measured inclination
of the magnetic field departs, to some extent, from the predominantly
horizontal field found in “typical” prominences. What is the role
of the magnetic field in these prominence types? Are plasma dynamics
more important in these cases than the magnetic support? We focus our
study on three types of “atypical” prominences (tornadoes, bubbles,
and jet-like prominence eruptions) that have all been observed by THEMIS
in the He I D3 line, from which the Stokes parameters can
be derived. The magnetic field strength, inclination, and azimuth in
each pixel are obtained by using the inversion method of principal
component analysis on a model of single scattering in the presence of
the Hanle effect. The magnetic field in tornadoes is found to be more
or less horizontal, whereas for the eruptive prominence it is mostly
vertical. We estimate a tendency toward higher values of magnetic
field strength inside the bubbles than outside in the surrounding
prominence. In all of the models in our database, only one magnetic
field orientation is considered for each pixel. While sufficient
for most of the main prominence body, this assumption appears to be
oversimplified in atypical prominence structures. We should consider
these observations as the result of superposition of multiple magnetic
fields, possibly even with a turbulent field component.

---------------------------------------------------------
Title: Evidence of flux rope and sigmoid in Active Regions prior
eruptions
Authors: Schmieder, Brigitte; Aulanier, Guillaume; Janvier, Miho;
Bommier, Veronique; Dudik, Jaroslav; Gilchrist, Stuart; Zhao, Jie
2016cosp...41E1750S Altcode:
In the solar corona, the magnetic field is dominant, and the current
density vector is nearly aligned with the magnetic field lines
for strong and stressed field regions. Stressed and highly twisted
flux ropes are at the origin of eruptive events such as flares and
coronal mass ejections, which inject material into the interplanetary
medium. The standard three dimensional (3D) flare model predicts
the complex evolution of flare loops and the flux rope before
the eruption. Flux ropes are not directly observed in the corona,
however it has started to be possible to detect their footprints
in the photosphere. Recent high spatial and temporal resolution
spectro-polarimeters have allowed us to compute the photospheric
electric currents and follow their evolution. Characteristics pattern
like J-shaped ribbons indicate the presence of a flux rope before
the flare. The results confirm the predictions of the 3D MHD standard
model of eruptive flares. It is interesting to compare the magnetic
helicity of the ejected flux rope with the in situ measurements of the
corresponding ICME at L1. We will show some examples (February 15 2011,
July 12 2012, Sept 10 2014).

---------------------------------------------------------
Title: Erratum: "Hooked Flare Ribbons and Flux-rope Related QSL
Footprints"<A href="/abs/2016ApJ...823...62Z">(2016, ApJ, 823, 62)</A>
Authors: Zhao, Jie; Gilchrist, Stuart A.; Aulanier, Guillaume;
Schmieder, Brigitte; Pariat, Etienne; Li, Hui
2016ApJ...825...80Z Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Statistical analysis of CMEs' geoeffectiveness over one year
of solar maximum during cycle 23
Authors: Schmieder, Brigitte; Bocchialini, Karine; Menvielle, Michel
2016cosp...41E1751S Altcode:
Using different propagation models from the Sun to the Earth,
we performed a statistical analysis over the year 2002 on CME's
geoeffectiveness linked to sudden storm commencements (ssc). We
also classified the perturbations of the interplanetary medium that
trigger the sscs. For each CME, the sources on the Sun of the CME are
identified as well as the properties of the parameters deduced from
spacecraft measurements along the path of the CME related event,
in the solar atmosphere, the interplanetary medium, and the Earth
ionized (magnetosphere and ionosphere) and neutral (thermosphere)
environments. The set of observations is statistically analysed so
as to evaluate the geoeffectiveness of CMEs in terms of ionospheric
and thermospheric signatures, with attention to possible differences
related to different kinds of solar sources. The observed Sun-to-Earth
travel times are compared to those estimated using the existing models
of propagation in the interplanetary medium, and this comparison is
used to statistically assess the performances of the various models.

---------------------------------------------------------
Title: Prominence plasma and magnetic field structure - A coordinated
observation with IRIS, Hinode and THEMIS
Authors: Schmieder, Brigitte; Labrosse, Nicolas; Levens, Peter;
Lopez Ariste, Arturo
2016cosp...41E1749S Altcode:
During an international campaign in 2014, utilising both space-based
(IRIS and Hinode) and ground-based (THEMIS) instruments, we focused
on observing prominences. We compare IRIS observations with those of
Hinode (EIS and SOT) in order to build a more complete picture of
the prominence structure for a quiescent prominence observed on 15
July 2014, identified to have tornado-like structure. THEMIS provides
valuable information on the orientation and strength of the internal
magnetic field. Here we find there is almost ubiquitously horizontal
field with respect to the local limb, with possibly a turbulent
component. The Mg II lines form the majority of our IRIS analysis,
with a mixture of reversed and non-reversed profiles present in the
prominence spectra. Comparing the differences between the Mg II data
from IRIS and the Ca II images from Hinode/SOT provides an intriguing
insight into the prominence legs in these channels. We present plasma
diagnostics from IRIS, with line of sight velocities of around 10
km/s in either direction along the magnetic loops of material in the
front of the prominence, and line widths comparable to those found
for prominences by previous authors (e.g. Schmieder et al. 2014). We
also take a look into the lines formed at higher, coronal plasma
temperatures, as seen by Hinode/EIS, to compare plasma structures at
a full range of temperatures.

---------------------------------------------------------
Title: Interaction of Two Filament Channels of Different Chiralities
Authors: Joshi, Navin Chandra; Filippov, Boris; Schmieder, Brigitte;
Magara, Tetsuya; Moon, Yong-Jae; Uddin, Wahab
2016ApJ...825..123J Altcode: 2016arXiv160501812J
We present observations of the interactions between the two filament
channels of different chiralities and associated dynamics that occurred
during 2014 April 18-20. While two flux ropes of different helicity with
parallel axial magnetic fields can only undergo a bounce interaction
when they are brought together, the observations at first glance
show that the heated plasma is moving from one filament channel to
the other. The SDO/AIA 171 Å observations and the potential-field
source-surface magnetic field extrapolation reveal the presence of
a fan-spine magnetic configuration over the filament channels with
a null point located above them. Three different events of filament
activations, partial eruptions, and associated filament channel
interactions have been observed. The activation initiated in one
filament channel seems to propagate along the neighboring filament
channel. We believe that the activation and partial eruption of the
filaments brings the field lines of flux ropes containing them closer
to the null point and triggers the magnetic reconnection between them
and the fan-spine magnetic configuration. As a result, the hot plasma
moves along the outer spine line toward the remote point. Utilizing
the present observations, for the first time we have discussed how
two different-chirality filament channels can interact and show
interrelation.

---------------------------------------------------------
Title: Hooked Flare Ribbons and Flux-rope-related QSL Footprints
Authors: Zhao, Jie; Gilchrist, Stuart A.; Aulanier, Guillaume;
Schmieder, Brigitte; Pariat, Etienne; Li, Hui
2016ApJ...823...62Z Altcode: 2016arXiv160307563Z
We studied the magnetic topology of active region 12158 on 2014
September 10 and compared it with the observations before and early in
the flare that begins at 17:21 UT (SOL2014-09-10T17:45:00). Our results
show that the sigmoidal structure and flare ribbons of this active
region observed by the Solar Dynamics Observatory/Atmospheric Imaging
Assembly can be well reproduced from a Grad-Rubin nonlinear force-free
field extrapolation method. Various inverse-S- and inverse-J-shaped
magnetic field lines, which surround a coronal flux rope, coincide with
the sigmoid as observed in different extreme-ultraviolet wavelengths,
including its multithreaded curved ends. Also, the observed distribution
of surface currents in the magnetic polarity where it was not prescribed
is well reproduced. This validates our numerical implementation and
setup of the Grad-Rubin method. The modeled double inverse-J-shaped
quasi-separatrix layer (QSL) footprints match the observed flare
ribbons during the rising phase of the flare, including their hooked
parts. The spiral-like shape of the latter may be related to a complex
pre-eruptive flux rope with more than one turn of twist, as obtained
in the model. These ribbon-associated flux-rope QSL footprints are
consistent with the new standard flare model in 3D, with the presence
of a hyperbolic flux tube located below an inverse-teardrop-shaped
coronal QSL. This is a new step forward forecasting the locations of
reconnection and ribbons in solar flares and the geometrical properties
of eruptive flux ropes.

---------------------------------------------------------
Title: Slipping Magnetic Reconnection, Chromospheric Evaporation,
Implosion, and Precursors in the 2014 September 10 X1.6-Class
Solar Flare
Authors: Dudík, Jaroslav; Polito, Vanessa; Janvier, Miho; Mulay,
Sargam M.; Karlický, Marian; Aulanier, Guillaume; Del Zanna, Giulio;
Dzifčáková, Elena; Mason, Helen E.; Schmieder, Brigitte
2016ApJ...823...41D Altcode: 2016arXiv160306092D
We investigate the occurrence of slipping magnetic reconnection,
chromospheric evaporation, and coronal loop dynamics in the 2014
September 10 X-class flare. Slipping reconnection is found to be present
throughout the flare from its early phase. Flare loops are seen to slip
in opposite directions toward both ends of the ribbons. Velocities
of 20-40 km s-1 are found within time windows where the
slipping is well resolved. The warm coronal loops exhibit expanding and
contracting motions that are interpreted as displacements due to the
growing flux rope that subsequently erupts. This flux rope existed and
erupted before the onset of apparent coronal implosion. This indicates
that the energy release proceeds by slipping reconnection and not via
coronal implosion. The slipping reconnection leads to changes in the
geometry of the observed structures at the Interface Region Imaging
Spectrograph slit position, from flare loop top to the footpoints in
the ribbons. This results in variations of the observed velocities of
chromospheric evaporation in the early flare phase. Finally, it is found
that the precursor signatures, including localized EUV brightenings as
well as nonthermal X-ray emission, are signatures of the flare itself,
progressing from the early phase toward the impulsive phase, with
the tether-cutting being provided by the slipping reconnection. The
dynamics of both the flare and outlying coronal loops is found to be
consistent with the predictions of the standard solar flare model in
three dimensions.

---------------------------------------------------------
Title: Magnetic Field and Plasma Diagnostics from Coordinated
Prominence Observations
Authors: Schmieder, B.; Levens, P.; Dalmasse, K.; Mein, N.; Mein,
P.; Lopez-Ariste, A.; Labrosse, N.; Heinzel, P.
2016ASPC..504..119S Altcode:
We study the magnetic field in prominences from a statistical point of
view, by using THEMIS in the MTR mode, performing spectropolarimetry
of the He I D3 line. Combining these measurements with
spectroscopic data from IRIS, Hinode/EIS as well as ground-based
telescopes, such as the Meudon Solar Tower, we infer the temperature,
density, and flow velocities of the plasma. There are a number of
open questions that we aim to answer: - What is the general direction
of the magnetic field in prominences? Is the model using a single
orientation of magnetic field always valid for atypical prominences? %-
Does this depend on the location of the filament on the disk (visible
in Hα, in He II 304 Å) over an inversion line between weak or strong
network ? - Are prominences in a weak environment field dominated by
gas pressure? - Measuring the Doppler shifts in Mg II lines (with IRIS)
and in Hα can tell us if there are substantial velocities to maintain
vertical rotating structures, as has been suggested for tornado-like
prominences. We present here some results obtained with different
ground-based and space-based instruments in this framework.

---------------------------------------------------------
Title: Chain Reconnections Observed in Sympathetic Eruptions
Authors: Joshi, Navin Chandra; Schmieder, Brigitte; Magara, Tetsuya;
Guo, Yang; Aulanier, Guillaume
2016ApJ...820..126J Altcode: 2016arXiv160207792J
The nature of various plausible causal links between sympathetic events
is still a controversial issue. In this work, we present multiwavelength
observations of sympathetic eruptions, associated flares, and coronal
mass ejections (CMEs) occurring on 2013 November 17 in two close active
regions. Two filaments, I.e., F1 and F2, are observed in between
the active regions. Successive magnetic reconnections, caused for
different reasons (flux cancellation, shear, and expansion) have been
identified during the whole event. The first reconnection occurred
during the first eruption via flux cancellation between the sheared
arcades overlying filament F2, creating a flux rope and leading to
the first double-ribbon solar flare. During this phase, we observed
the eruption of overlying arcades and coronal loops, which leads to
the first CME. The second reconnection is believed to occur between
the expanding flux rope of F2 and the overlying arcades of filament
F1. We suggest that this reconnection destabilized the equilibrium of
filament F1, which further facilitated its eruption. The third stage of
reconnection occurred in the wake of the erupting filament F1 between
the legs of the overlying arcades. This may create a flux rope and the
second double-ribbon flare and a second CME. The fourth reconnection
was between the expanding arcades of the erupting filament F1 and the
nearby ambient field, which produced the bi-directional plasma flows
both upward and downward. Observations and a nonlinear force-free
field extrapolation confirm the possibility of reconnection and the
causal link between the magnetic systems.

---------------------------------------------------------
Title: Structure of Prominence Legs: Plasma and Magnetic Field
Authors: Levens, P. J.; Schmieder, B.; Labrosse, N.; López Ariste, A.
2016ApJ...818...31L Altcode: 2015arXiv151204727L
We investigate the properties of a “solar tornado” observed
on 2014 July 15, and aim to link the behavior of the plasma to the
internal magnetic field structure of the associated prominence. We
made multi-wavelength observations with high spatial resolution and
high cadence using SDO/AIA, the Interface Region Imaging Spectrograph
(IRIS) spectrograph, and the Hinode/Solar Optical Telescope (SOT)
instrument. Along with spectropolarimetry provided by the Télescope
Héliographique pour l’Etude du Magnétisme et des Instabilités
Solaires telescope we have coverage of both optically thick emission
lines and magnetic field information. AIA reveals that the two legs
of the prominence are strongly absorbing structures which look like
they are rotating, or oscillating in the plane of the sky. The two
prominence legs, which are both very bright in Ca II (SOT), are not
visible in the IRIS Mg II slit-jaw images. This is explained by the
large optical thickness of the structures in Mg II, which leads to
reversed profiles, and hence to lower integrated intensities at these
locations than in the surroundings. Using lines formed at temperatures
lower than 1 MK, we measure relatively low Doppler shifts on the order
of ±10 km s-1 in the tornado-like structure. Between the two
legs we see loops in Mg II, with material flowing from one leg to the
other, as well as counterstreaming. It is difficult to interpret our
data as showing two rotating, vertical structures that are unrelated
to the loops. This kind of “tornado” scenario does not fit with
our observations. The magnetic field in the two legs of the prominence
is found to be preferentially horizontal.

---------------------------------------------------------
Title: Role of "X point” in Flares and Filament Interactions
Authors: Schmieder, B.; Zuccarello, F. P.; Aulanier, G.; Chandra,
R.; Joshi, N. C.; Filippov, B.
2016CEAB...40...35S Altcode:
Explaining the trigger and energy release processes of flares is a
fundamental problem of solar physics. It is commonly held that magnetic
reconnection plays a key role in converting magnetic energy into other
forms of energy. In 2D magnetic field configurations, when oppositely
directed magnetic fields are brought together they may reconnect thereby
releasing stored magnetic energy eventually resulting in a flare. In
3D configurations, the magnetic topology should be considered and the
reconnection is favored at the intersection of magnetic quasi-separatrix
layers, which is an extension of what is called "X point" in 2D. The
evolution of key topological structures, such as null point, spines
and fans may determine the eruptive behavior of a flare. The presence
of a null point can be very important. We present a few examples, i.e.,
a flare with a circular flare ribbon and the interaction of two parallel
filaments. In the case of flux rope destabilization and triggering
eruption due to the torus instability, the important parameter is
the decay index and not the topology itself. However the complexity
of active regions leads to interpretations where different mechanisms
may be intermixed. The breakout mechanism, which requires a quadrupolar
configuration with QSLs and separator where the reconnection can occur,
is present in many models. That is not always a sufficient condition
to explain the eruptive flares. For one case study, the different
behaviour of a series of eruptive flares followed by confined flares,
all originating in the same site has been attributed to the change of
orientation of the magnetic field below the fan with respect to the
orientation of the spine. Flares tend to be more confined when the
two fields become less antiparallel.

---------------------------------------------------------
Title: ALMA Observations of the Sun in Cycle 4 and Beyond
Authors: Wedemeyer, S.; Fleck, B.; Battaglia, M.; Labrosse, N.;
Fleishman, G.; Hudson, H.; Antolin, P.; Alissandrakis, C.; Ayres, T.;
Ballester, J.; Bastian, T.; Black, J.; Benz, A.; Brajsa, R.; Carlsson,
M.; Costa, J.; DePontieu, B.; Doyle, G.; Gimenez de Castro, G.;
Gunár, S.; Harper, G.; Jafarzadeh, S.; Loukitcheva, M.; Nakariakov,
V.; Oliver, R.; Schmieder, B.; Selhorst, C.; Shimojo, M.; Simões,
P.; Soler, R.; Temmer, M.; Tiwari, S.; Van Doorsselaere, T.; Veronig,
A.; White, S.; Yagoubov, P.; Zaqarashvili, T.
2016arXiv160100587W Altcode:
This document was created by the Solar Simulations for the Atacama
Large Millimeter Observatory Network (SSALMON) in preparation of
the first regular observations of the Sun with the Atacama Large
Millimeter/submillimeter Array (ALMA), which are anticipated to start
in ALMA Cycle 4 in October 2016. The science cases presented here
demonstrate that a large number of scientifically highly interesting
observations could be made already with the still limited solar
observing modes foreseen for Cycle 4 and that ALMA has the potential
to make important contributions to answering long-standing scientific
questions in solar physics. With the proposal deadline for ALMA Cycle
4 in April 2016 and the Commissioning and Science Verification campaign
in December 2015 in sight, several of the SSALMON Expert Teams composed
strategic documents in which they outlined potential solar observations
that could be feasible given the anticipated technical capabilities
in Cycle 4. These documents have been combined and supplemented
with an analysis, resulting in recommendations for solar observing
with ALMA in Cycle 4. In addition, the detailed science cases also
demonstrate the scientific priorities of the solar physics community
and which capabilities are wanted for the next observing cycles. The
work on this White Paper effort was coordinated in close cooperation
with the two international solar ALMA development studies led by
T. Bastian (NRAO, USA) and R. Brajsa, (ESO). This document will be
further updated until the beginning of Cycle 4 in October 2016. In
particular, we plan to adjust the technical capabilities of the solar
observing modes once finally decided and to further demonstrate the
feasibility and scientific potential of the included science cases by
means of numerical simulations of the solar atmosphere and corresponding
simulated ALMA observations.

---------------------------------------------------------
Title: Flare-CME Models: An Observational Perspective (Invited Review)
Authors: Schmieder, B.; Aulanier, G.; Vršnak, B.
2015SoPh..290.3457S Altcode: 2015SoPh..tmp...64S
Eruptions, flares, and coronal mass ejection (CMEs) are due to physical
phenomena mainly driven by an initially force-free current-carrying
magnetic field. We review some key observations relevant to the
current theoretical trigger mechanisms of the eruption and to the
energy release via reconnection. Sigmoids observed in X-rays and UV,
as well as the pattern (double J-shaped) of electric currents in
the photosphere show clear evidence of the existence of currents
parallel to the magnetic field and can be the signature of a flux
rope that is detectable in CMEs. The magnetic helicity of filaments
and active regions is an interesting indirectly measurable parameter
because it can quantify the twist of the flux rope. On the other hand,
the magnetic helicity of the solar structures allows us to associate
solar eruptions and magnetic clouds in the heliosphere. The magnetic
topology analysis based on the 3D magnetic field extrapolated from
vector magnetograms is a good tool for identifying the reconnection
locations (null points and/or the 3D large volumes - hyperbolic flux
tube, HFT). Flares are associated more with quasi-separatrix layers
(QSLs) and HFTs than with a single null point, which is a relatively
rare case. We review various mechanisms that have been proposed to
trigger CMEs and their observable signatures: by "breaking" the field
lines overlying the flux rope or by reconnection below the flux rope
to reduce the magnetic tension, or by letting the flux rope to expand
until it reaches a minimum threshold height (loss of equilibrium or
torus instability). Additional mechanisms are commonly operating in
the solar atmosphere. Examples of observations are presented throughout
the article and are discussed in this framework.

---------------------------------------------------------
Title: Nonlinear MHD Waves in a Prominence Foot
Authors: Ofman, L.; Knizhnik, K.; Kucera, T.; Schmieder, B.
2015ApJ...813..124O Altcode: 2015arXiv150907911O
We study nonlinear waves in a prominence foot using a 2.5D MHD model
motivated by recent high-resolution observations with Hinode/Solar
Optical Telescope in Ca ii emission of a prominence on 2012 October
10 showing highly dynamic small-scale motions in the prominence
material. Observations of Hα intensities and of Doppler shifts show
similar propagating fluctuations. However, the optically thick nature
of the emission lines inhibits a unique quantitative interpretation
in terms of density. Nevertheless, we find evidence of nonlinear wave
activity in the prominence foot by examining the relative magnitude of
the fluctuation intensity (δI/I ∼ δn/n). The waves are evident as
significant density fluctuations that vary with height and apparently
travel upward from the chromosphere into the prominence material
with quasi-periodic fluctuations with a typical period in the range
of 5-11 minutes and wavelengths &lt;2000 km. Recent Doppler shift
observations show the transverse displacement of the propagating
waves. The magnetic field was measured with the THEMIS instrument
and was found to be 5-14 G. For the typical prominence density the
corresponding fast magnetosonic speed is ∼20 km s-1,
in qualitative agreement with the propagation speed of the detected
waves. The 2.5D MHD numerical model is constrained with the typical
parameters of the prominence waves seen in observations. Our numerical
results reproduce the nonlinear fast magnetosonic waves and provide
strong support for the presence of these waves in the prominence
foot. We also explore gravitational MHD oscillations of the heavy
prominence foot material supported by dipped magnetic field structure.

---------------------------------------------------------
Title: A solar tornado observed by EIS. Plasma diagnostics
Authors: Levens, P. J.; Labrosse, N.; Fletcher, L.; Schmieder, B.
2015A&A...582A..27L Altcode: 2015arXiv150801377L
Context. The term "solar tornadoes" has been used to describe apparently
rotating magnetic structures above the solar limb, as seen in high
resolution images and movies from the Atmospheric Imaging Assembly
(AIA) aboard the Solar Dynamics Observatory (SDO). These often form
part of the larger magnetic structure of a prominence, however the
links between them remain unclear. Here we present plasma diagnostics
on a tornado-like structure and its surroundings, seen above the
limb by the Extreme-ultraviolet Imaging Spectrometer (EIS) aboard
the Hinode satellite. Aims: We aim to extend our view of the
velocity patterns seen in tornado-like structures with EIS to a wider
range of temperatures and to use density diagnostics, non-thermal
line widths, and differential emission measures to provide insight
into the physical characteristics of the plasma. Methods:
Using Gaussian fitting to fit and de-blend the spectral lines seen
by EIS, we calculated line-of-sight velocities and non-thermal line
widths. Along with information from the CHIANTI database, we used line
intensity ratios to calculate electron densities at each pixel. Using
a regularised inversion code we also calculated the differential
emission measure (DEM) at different locations in the prominence. Results: The split Doppler-shift pattern is found to be visible
down to a temperature of around log T = 6.0. At temperatures lower
than this, the pattern is unclear in this data set. We obtain an
electron density of log ne = 8.5 when looking towards the
centre of the tornado structure at a plasma temperature of log T =
6.2, as compared to the surroundings of the tornado structure where
we find log ne to be nearer 9. Non-thermal line widths
show broader profiles at the tornado location when compared to the
surrounding corona. We discuss the differential emission measure in
both the tornado and the prominence body, which suggests that there is
more contribution in the tornado at temperatures below log T = 6.0 than
in the prominence. A movie is available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201425586/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Polarimetric measurements in prominences and "tornadoe"
observed by THEMIS
Authors: Schmieder, Brigitte; López Ariste, Arturo; Levens, Peter;
Labrosse, Nicolas; Dalmasse, Kévin
2015IAUS..305..275S Altcode:
Since 2013, coordinated campaigns with the THEMIS spectropolarimeter in
Tenerife and other instruments (space based: Hinode/SOT, IRIS or ground
based: Sac Peak, Meudon) are organized to observe prominences. THEMIS
records spectropolarimetry at the He I D3 and we use the
PCA inversion technique to derive their field strength, inclination
and azimuth.

---------------------------------------------------------
Title: Coronal Mass Ejections from the Same Active Region Cluster:
Two Different Perspectives
Authors: Cremades, H.; Mandrini, C. H.; Schmieder, B.; Crescitelli,
A. M.
2015SoPh..290.1671C Altcode: 2015arXiv150501384C; 2015SoPh..tmp...86C
The cluster formed by active regions (ARs) NOAA 11121 and 11123,
approximately located on the solar central meridian on 11 November 2010,
is of great scientific interest. This complex was the site of violent
flux emergence and the source of a series of Earth-directed events on
the same day. The onset of the events was nearly simultaneously observed
by the Atmospheric Imaging Assembly (AIA) telescope onboard the Solar
Dynamics Observatory (SDO) and the Extreme-Ultraviolet Imagers (EUVI) on
the Sun-Earth Connection Coronal and Heliospheric Investigation (SECCHI)
suite of telescopes onboard the Solar-Terrestrial Relations Observatory
(STEREO) twin spacecraft. The progression of these events in the low
corona was tracked by the Large Angle Spectroscopic Coronagraphs (LASCO)
onboard the Solar and Heliospheric Observatory (SOHO) and the SECCHI/COR
coronagraphs on STEREO. SDO and SOHO imagers provided data from the
Earth's perspective, whilst the STEREO twin instruments procured
images from the orthogonal directions. This spatial configuration of
spacecraft allowed optimum simultaneous observations of the AR cluster
and the coronal mass ejections that originated in it. Quadrature
coronal observations provided by STEREO revealed many more ejective
events than were detected from Earth. Furthermore, joint observations
by SDO/AIA and STEREO/SECCHI EUVI of the source region indicate that
all events classified by GOES as X-ray flares had an ejective coronal
counterpart in quadrature observations. These results directly affect
current space weather forecasting because alarms might be missed when
there is a lack of solar observations in a view direction perpendicular
to the Sun-Earth line.

---------------------------------------------------------
Title: Understanding the Mg II and Hα Spectra in a Highly Dynamical
Solar Prominence
Authors: Heinzel, P.; Schmieder, B.; Mein, N.; Gunár, S.
2015ApJ...800L..13H Altcode:
Mg ii h and k and Hα spectra in a dynamical prominence have been
obtained along the slit of the Interface Region Imaging Spectrograph
(IRIS) and with the Meudon Multi-channel Subtractive Double Pass
spectrograph on 2013 September 24, respectively. Single Mg ii line
profiles are not much reversed, while at some positions along
the IRIS slit the profiles show several discrete peaks that are
Doppler-shifted. The intensity of these peaks is generally decreasing
with their increasing Doppler shift. We interpret this unusual behavior
as being due to the Doppler dimming effect. We discuss the possibility
to interpret the unreversed single profiles by using a two-dimensional
(2D) model of the entire prominence body with specific radiative
boundary conditions. We have performed new 2D isothermal-isobaric
modeling of both Hα and Mg ii lines and show the ability of such models
to account for the line profile variations as observed. However, the Mg
ii line-center intensities require the model with a temperature increase
toward the prominence boundary. We show that even simple one-dimensional
(1D) models with a prominence-to-corona transition region (PCTR) fit the
observed Mg ii and Hα lines quite well, while the isothermal-isobaric
models (1D or 2D) are inconsistent with simultaneous observations in
the Mg ii h and k and Hα lines, meaning that the Hα line provides a
strong additional constraint on the modeling. IRIS far-UV detection of
the C ii lines in this prominence seems to provide a direct constraint
on the PCTR part of the model.

---------------------------------------------------------
Title: Can we explain atypical solar flares?
Authors: Dalmasse, K.; Chandra, R.; Schmieder, B.; Aulanier, G.
2015A&A...574A..37D Altcode: 2014arXiv1410.8194D
Context. We used multiwavelength high-resolution data from ARIES,
THEMIS, and SDO instruments to analyze a non-standard, C3.3 class
flare produced within the active region NOAA 11589 on 2012 October
16. Magnetic flux emergence and cancellation were continuously detected
within the active region, the latter leading to the formation of
two filaments. Aims: Our aim is to identify the origins of
the flare taking the complex dynamics of its close surroundings into
account. Methods: We analyzed the magnetic topology of the active
region using a linear force-free field extrapolation to derive its 3D
magnetic configuration and the location of quasi-separatrix layers
(QSLs), which are preferred sites for flaring activity. Because the
active region's magnetic field was nonlinear force-free, we completed a
parametric study using different linear force-free field extrapolations
to demonstrate the robustness of the derived QSLs. Results:
The topological analysis shows that the active region presented a
complex magnetic configuration comprising several QSLs. The considered
data set suggests that an emerging flux episode played a key role in
triggering the flare. The emerging flux probably activated the complex
system of QSLs, leading to multiple coronal magnetic reconnections
within the QSLs. This scenario accounts for the observed signatures:
the two extended flare ribbons developed at locations matched by
the photospheric footprints of the QSLs and were accompanied with
flare loops that formed above the two filaments, which played no
important role in the flare dynamics. Conclusions: This is a
typical example of a complex flare that can a priori show standard
flare signatures that are nevertheless impossible to interpret with
any standard model of eruptive or confined flare. We find that a
topological analysis, however, permitted us to unveil the development
of such complex sets of flare signatures. Movies associated to
Figs. 1, 3, and 9 are only available at the CDS via anonymous ftp to <A
href="http://cdsarc.u-strasbg.fr">http://cdsarc.u-strasbg.fr</A>
(ftp://130.79.128.5) or via <A
href="http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/574/A37">http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/574/A37</A>

---------------------------------------------------------
Title: Magnetic Flux Emergence Along the Solar Cycle
Authors: Schmieder, B.; Archontis, V.; Pariat, E.
2015sac..book..227S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: VizieR Online Data Catalog: Movies of 2012-10-16 solar flare
(Dalmasse+, 2015)
Authors: Dalmasse, K.; Chandra, R.; Schmieder, B.; Aulanier, G.
2015yCat..35740037D Altcode: 2015yCat..35749037D
Part of the observations of NOAA 11589 presented here were obtained
with the Atmospheric Imaging Assembly imager (AIA) and the Helioseismic
and Magnetic Imager (HMI) onboard the Solar Dynamic Observatory (SDO)
satellite. The AIA instrument observes the Sun over a wide range of
temperatures from the photosphere to the corona. The pixel size of the
AIA images is 0.6". In this study, we considered the 1600, 304, 193,
and 171Å data. The magnetic field in the AR was studied by using the
line-of-sight magnetograms of the HMI instrument, which observes the
full disk with a pixel size of 0.5". We also used ground-based
observations of the AR obtained with the Indian telescope from the
Aryabhatta Research Institute of observational Sciences (ARIES) and
with the French Telescope Heliographique pour l'Etude du Magnetisme
et des Instabilites Solaires (THEMIS). The 15-cm f/15 Coude telescope
of the ARIES, operating in Nainital (India), observes in the Hα line
with a spatial resolution of 0.58". The THEMIS telescope, operating
in Tenerife (Canary Islands), allows a simultaneous mapping of the
Hα emission and the full Stokes parameters in the Fe 6302.5Å of a
field of view of about 240"x100" in one hour. (2 data files).

---------------------------------------------------------
Title: Magnetic Flux Emergence Along the Solar Cycle
Authors: Schmieder, B.; Archontis, V.; Pariat, E.
2014SSRv..186..227S Altcode: 2014SSRv..tmp...47S
Flux emergence plays an important role along the solar cycle. Magnetic
flux emergence builds sunspot groups and solar activity. The sunspot
groups contribute to the large scale behaviour of the magnetic field
over the 11 year cycle and the reversal of the North and South magnetic
polarity every 22 years. The leading polarity of sunspot groups is
opposite in the North and South hemispheres and reverses for each
new solar cycle. However the hemispheric rule shows the conservation
of sign of the magnetic helicity with positive and negative magnetic
helicity in the South and North hemispheres, respectively. MHD models
of emerging flux have been developed over the past twenty years but
have not yet succeeded to reproduce solar observations. The emergence
of flux occurs through plasma layers of very high gradients of pressure
and changing of modes from a large β to a low β plasma (&lt;1). With
the new armada of high spatial and temporal resolution instruments
on the ground and in space, emergence of magnetic flux is observed
in tremendous detail and followed during their transit through the
upper atmosphere. Signatures of flux emergence in the corona depend
on the pre-existing magnetic configuration and on the strength of the
emerging flux. We review in this paper new and established models as
well as the recent observations.

---------------------------------------------------------
Title: Recurrent Coronal Jets Induced by Magnetic Emergence in the
Solar Atmosphere
Authors: Guo, Y.; Démoulin, P.; Schmieder, B.; Ding, M. D.; Vargas
Domínguez, S.; Liu, Y.
2014RMxAC..44...45G Altcode:
Jets are part of the observed phenomenology in the solar corona. They
are thought to be a consequence of magnetic reconnection but the physics
involved is not completely understood. We study some recurrent jetting
events with unprecedented temporal and spatial resolutions.

---------------------------------------------------------
Title: Open questions on prominences from coordinated observations
by IRIS, Hinode, SDO/AIA, THEMIS, and the Meudon/MSDP
Authors: Schmieder, B.; Tian, H.; Kucera, T.; López Ariste, A.;
Mein, N.; Mein, P.; Dalmasse, K.; Golub, L.
2014A&A...569A..85S Altcode: 2014arXiv1407.3171S
Context. A large prominence was observed by multiple instruments on the
ground and in space during an international campaign on September 24,
2013, for three hours (12:12 UT -15:12 UT). Instruments used in the
campaign included the newly launched (June 2013) Interface Region
Imaging Spectrograph (IRIS), THEMIS (Tenerife), the Hinode Solar
Optical Telescope (SOT), the Solar Dynamic Observatory's Atmospheric
Imaging Assembly (SDO/AIA), and the Multichannel Subtractive Double
Pass spectrograph (MSDP) in the Meudon Solar Tower. The movies obtained
in 304 Å with the EUV imager SDO/AIA, and in Ca II line by SOT show
the dynamic nature of the prominence. Aims: The aim of this
work is to study the dynamics of the prominence fine structures in
multiple wavelengths to understand their formation. Methods:
The spectrographs IRIS and MSDP provided line profiles with a high
cadence in Mg II h (2803.5 Å) and k (2796.4 Å) lines along four
slit positions (IRIS), and in Hα in a 2D field of view (MSDP). The
spectropolarimetry of THEMIS (Tenerife) allowed us to derive the
magnetic field of the prominence using the He D3 line
depolarization (Hanle effect combined with the Zeeman effect). 
Results: The magnetic field is found to be globally horizontal with
a relatively weak field strength (8-15 Gauss). On the other hand,
the Ca II movie reveals turbulent-like motion that is not organized in
specific parts of the prominence. We tested the addition of a turbulent
magnetic component. This model is compatible with the polarimetric
observations at those places where the plasma turbulence peaks. On the
other hand, the Mg II line profiles show multiple peaks well separated
in wavelength. This is interpreted by the existence of small threads
along the line of sight with a large dispersion of discrete values of
Doppler shifts, from 5 km s-1 (a quasi-steady component) to
60-80 km s-1. Each peak corresponds to a Gaussian profile,
and not to a reversed profile as was expected by the present non-LTE
radiative transfer modeling. This is a very surprising behavior for
the Mg II line observed in prominences. Conclusions: Turbulent
fields on top of the macroscopic horizontal component of the magnetic
field supporting the prominence give rise to the complex dynamics of
the plasma. The plasma with the high velocities (70 km s-1 to
100 km s-1 if we take into account the transverse velocities)
may correspond to condensation of plasma along more or less horizontal
threads of the arch-shape structure visible in 304 Å. The steady
flows (5 km s-1) would correspond to a more quiescent plasma
(cool and prominence-corona transition region) of the prominence packed
into dips in horizontal magnetic field lines. The very weak secondary
peaks in the Mg II profiles may reflect the turbulent nature of parts
of the prominence. Movies are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201423922/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Magnetic field and radiative transfer modelling of a quiescent
prominence
Authors: Gunár, S.; Schwartz, P.; Dudík, J.; Schmieder, B.; Heinzel,
P.; Jurčák, J.
2014A&A...567A.123G Altcode:
 Aims: The aim of this work is to analyse the multi-instrument
observations of the June 22, 2010 prominence to study its structure in
detail, including the prominence-corona transition region and the dark
bubble located below the prominence body. Methods: We combined
results of the 3D magnetic field modelling with 2D prominence fine
structure radiative transfer models to fully exploit the available
observations. Results: The 3D linear force-free field model
with the unsheared bipole reproduces the morphology of the analysed
prominence reasonably well, thus providing useful information about
its magnetic field configuration and the location of the magnetic
dips. The 2D models of the prominence fine structures provide a good
representation of the local plasma configuration in the region dominated
by the quasi-vertical threads. However, the low observed Lyman-α
central intensities and the morphology of the analysed prominence
suggest that its upper central part is not directly illuminated from the
solar surface. Conclusions: This multi-disciplinary prominence
study allows us to argue that a large part of the prominence-corona
transition region plasma can be located inside the magnetic dips in
small-scale features that surround the cool prominence material located
in the dip centre. We also argue that the dark prominence bubbles
can be formed because of perturbations of the prominence magnetic
field by parasitic bipoles, causing them to be devoid of the magnetic
dips. Magnetic dips, however, form thin layers that surround these
bubbles, which might explain the occurrence of the cool prominence
material in the lines of sight intersecting the prominence bubbles. Movie and Appendix A are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201322777/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: Time Evolution of the Altitude of an Observed Coronal Wave
Authors: Delannée, C.; Artzner, G.; Schmieder, B.; Parenti, S.
2014SoPh..289.2565D Altcode: 2014SoPh..tmp...49D; 2013arXiv1310.5623D
The nature of coronal wave fronts is intensely debated. They are
observed in several wavelength bands and are frequently interpreted as
magnetosonic waves propagating in the lower solar atmosphere. However,
they can also be attributed to the line-of-sight projection of the
edges of coronal mass ejections. Therefore, estimating the altitude of
these features is crucial for deciding in favor of one of these two
interpretations. We took advantage of a set of observations obtained
from two different view directions by the EUVI instrument onboard
the STEREO mission on 7 December 2007 to derive the time evolution of
the altitude of a coronal wave front. We developed a new technique to
compute the altitude of the coronal wave and found that the altitude
increased during the initial 5 min and then slightly decreased back to
the low corona. We interpret the evolution of the altitude as follows:
the increase in the altitude of the wave front is linked to the rise
of a bubble-like structure depending on whether it is a magnetosonic
wave front or a CME in the initial phase. During the second phase, the
observed brightness of the wave front was mixed with the brightening
of the underlying magnetic structures as the emission from the wave
front faded because the plasma became diluted with altitude.

---------------------------------------------------------
Title: Electric Currents in Flare Ribbons: Observations and
Three-dimensional Standard Model
Authors: Janvier, M.; Aulanier, G.; Bommier, V.; Schmieder, B.;
Démoulin, P.; Pariat, E.
2014ApJ...788...60J Altcode: 2014arXiv1402.2010J
We present for the first time the evolution of the photospheric electric
currents during an eruptive X-class flare, accurately predicted by the
standard three-dimensional (3D) flare model. We analyze this evolution
for the 2011 February 15 flare using Helioseismic and Magnetic
Imager/Solar Dynamics Observatory magnetic observations and find
that localized currents in J-shaped ribbons increase to double their
pre-flare intensity. Our 3D flare model, developed with the OHM code,
suggests that these current ribbons, which develop at the location of
extreme ultraviolet brightenings seen with Atmospheric Imaging Assembly
imagery, are driven by the collapse of the flare's coronal current
layer. These findings of increased currents restricted in localized
ribbons are consistent with the overall free energy decrease during a
flare, and the shapes of these ribbons also give an indication of how
twisted the erupting flux rope is. Finally, this study further enhances
the close correspondence obtained between the theoretical predictions
of the standard 3D model and flare observations, indicating that the
main key physical elements are incorporated in the model.

---------------------------------------------------------
Title: Topological Analysis of Emerging Bipole Clusters Producing
Violent Solar Events
Authors: Mandrini, C. H.; Schmieder, B.; Démoulin, P.; Guo, Y.;
Cristiani, G. D.
2014SoPh..289.2041M Altcode: 2013arXiv1312.3359M
During the rising phase of Solar Cycle 24 tremendous activity occurred
on the Sun with rapid and compact emergence of magnetic flux leading
to bursts of flares (C to M and even X-class). We investigate the
violent events occurring in the cluster of two active regions (ARs),
NOAA numbers 11121 and 11123, observed in November 2010 with instruments
onboard the Solar Dynamics Observatory and from Earth. Within one day
the total magnetic flux increased by 70 % with the emergence of new
groups of bipoles in AR 11123. From all the events on 11 November,
we study, in particular, the ones starting at around 07:16 UT in GOES
soft X-ray data and the brightenings preceding them. A magnetic-field
topological analysis indicates the presence of null points,
associated separatrices, and quasi-separatrix layers (QSLs) where
magnetic reconnection is prone to occur. The presence of null points
is confirmed by a linear and a non-linear force-free magnetic-field
model. Their locations and general characteristics are similar in both
modelling approaches, which supports their robustness. However, in order
to explain the full extension of the analysed event brightenings,
which are not restricted to the photospheric traces of the null
separatrices, we compute the locations of QSLs. Based on this more
complete topological analysis, we propose a scenario to explain the
origin of a low-energy event preceding a filament eruption, which is
accompanied by a two-ribbon flare, and a consecutive confined flare in
AR 11123. The results of our topology computation can also explain the
locations of flare ribbons in two other events, one preceding and one
following the ones at 07:16 UT. Finally, this study provides further
examples where flare-ribbon locations can be explained when compared
to QSLs and only, partially, when using separatrices.

---------------------------------------------------------
Title: Temporal Evolution of the Magnetic Topology of the NOAA Active
Region 11158
Authors: Zhao, Jie; Li, Hui; Pariat, Etienne; Schmieder, Brigitte;
Guo, Yang; Wiegelmann, Thomas
2014ApJ...787...88Z Altcode: 2014arXiv1404.5004Z
We studied the temporal evolution of the magnetic topology of the active
region (AR) 11158 based on the reconstructed three-dimensional magnetic
fields in the corona. The non-linear force-free field extrapolation
method was applied to the 12 minute cadence data obtained with the
Helioseismic and Magnetic Imager on board the Solar Dynamics Observatory
during 5 days. By calculating the squashing degree factor Q in the
volume, the derived quasi-separatrix layers (QSLs) show that this AR has
an overall topology, resulting from a magnetic quadrupole, including a
hyperbolic flux tube (HFT) configuration that is relatively stable at
the timescale of the flare (~1-2 hr). A strong QSL, which corresponds
to some highly sheared arcades that might be related to the formation
of a flux rope, is prominent just before the M6.6 and X2.2 flares,
respectively. These facts indicate the close relationship between the
strong QSL and the high flare productivity of AR 11158. In addition,
with a close inspection of the topology, we found a small-scale HFT
that has an inverse tear-drop structure above the aforementioned
QSL before the X2.2 flare. It indicates the existence of magnetic
flux rope at this place. Even though a global configuration (HFT)
is recognized in this AR, it turns out that the large-scale HFT only
plays a secondary role during the eruption. In conclusion, we dismiss
a trigger based on the breakout model and highlight the central role
of the flux rope in the related eruption.

---------------------------------------------------------
Title: Detection of Coherent Structures in Photospheric Turbulent
Flows
Authors: Chian, Abraham C. -L.; Rempel, Erico L.; Aulanier, Guillaume;
Schmieder, Brigitte; Shadden, Shawn C.; Welsch, Brian T.; Yeates,
Anthony R.
2014ApJ...786...51C Altcode: 2013arXiv1312.2405C
We study coherent structures in solar photospheric flows in a plage in
the vicinity of the active region AR 10930 using the horizontal velocity
data derived from Hinode/Solar Optical Telescope magnetograms. Eulerian
and Lagrangian coherent structures (LCSs) are detected by computing
the Q-criterion and the finite-time Lyapunov exponents of the velocity
field, respectively. Our analysis indicates that, on average, the
deformation Eulerian coherent structures dominate over the vortical
Eulerian coherent structures in the plage region. We demonstrate the
correspondence of the network of high magnetic flux concentration to the
attracting Lagrangian coherent structures (aLCSs) in the photospheric
velocity based on both observations and numerical simulations. In
addition, the computation of aLCS provides a measure of the local rate
of contraction/expansion of the flow.

---------------------------------------------------------
Title: Slipping Magnetic Reconnection during an X-class Solar Flare
Observed by SDO/AIA
Authors: Dudík, J.; Janvier, M.; Aulanier, G.; Del Zanna, G.;
Karlický, M.; Mason, H. E.; Schmieder, B.
2014ApJ...784..144D Altcode: 2014arXiv1401.7529D
We present SDO/AIA observations of an eruptive X-class flare of
2012 July 12, and compare its evolution with the predictions of a
three-dimensional (3D) numerical simulation. We focus on the dynamics of
flare loops that are seen to undergo slipping reconnection during the
flare. In the Atmospheric Imaging Assembly (AIA) 131 Å observations,
lower parts of 10 MK flare loops exhibit an apparent motion with
velocities of several tens of km s-1 along the developing
flare ribbons. In the early stages of the flare, flare ribbons consist
of compact, localized bright transition-region emission from the
footpoints of the flare loops. A differential emission measure analysis
shows that the flare loops have temperatures up to the formation of
Fe XXIV. A series of very long, S-shaped loops erupt, leading to a
coronal mass ejection observed by STEREO. The observed dynamics are
compared with the evolution of magnetic structures in the "standard
solar flare model in 3D." This model matches the observations well,
reproducing the apparently slipping flare loops, S-shaped erupting
loops, and the evolution of flare ribbons. All of these processes are
explained via 3D reconnection mechanisms resulting from the expansion
of a torus-unstable flux rope. The AIA observations and the numerical
model are complemented by radio observations showing a noise storm
in the metric range. Dm-drifting pulsation structures occurring
during the eruption indicate plasmoid ejection and enhancement of the
reconnection rate. The bursty nature of radio emission shows that the
slipping reconnection is still intermittent, although it is observed
to persist for more than an hour.

---------------------------------------------------------
Title: Proper horizontal photospheric flows in a filament channel
Authors: Schmieder, B.; Roudier, T.; Mein, N.; Mein, P.; Malherbe,
J. M.; Chandra, R.
2014A&A...564A.104S Altcode:
Context. An extended filament in the central part of the active
region NOAA 11106 crossed the central meridian on Sept. 17, 2010 in
the southern hemisphere. It has been observed in Hα with the THEMIS
telescope in the Canary Islands and in 304 Å with the EUV imager (AIA)
onboard the Solar Dynamic Observatory (SDO). Counterstreaming along the
Hα threads and bright moving blobs (jets) along the 304 Å filament
channel were observed during 10 h before the filament erupted at 17:03
UT. Aims: The aim of the paper is to understand the coupling
between magnetic field and convection in filament channels and relate
the horizontal photospheric motions to the activity of the filament. Methods: An analysis of the proper photospheric motions using SDO/HMI
continuum images with the new version of the coherent structure tracking
(CST) algorithm developed to track granules, as well as the large
scale photospheric flows, was performed for three hours. Using corks,
we derived the passive scalar points and produced a map of the cork
distribution in the filament channel. Averaging the velocity vectors
in the southern hemisphere in each latitude in steps of 3.5 arcsec,
we defined a profile of the differential rotation. Results:
Supergranules are clearly identified in the filament channel. Diverging
flows inside the supergranules are similar in and out of the filament
channel. Converging flows corresponding to the accumulation of corks
are identified well around the Hα filament feet and at the edges of
the EUV filament channel. At these convergence points, the horizontal
photospheric velocity may reach 1 km s-1, but with a mean
velocity of 0.35 km s-1. In some locations, horizontal
flows crossing the channel are detected, indicating eventually large
scale vorticity. Conclusions: The coupling between convection
and magnetic field in the photosphere is relatively strong. The
filament experienced the convection motions through its anchorage
points with the photosphere, which are magnetized areas (ends, feet,
lateral extensions of the EUV filament channel). From a large scale
point-of-view, the differential rotation induced a shear of 0.1 km
s-1 in the filament. From a small scale point-of-view,
any convective motions favored the interaction of the parasitic
polarities responsible for the anchorages of the filament to the
photosphere with the surrounding network and may explain the activity
of the filament. Two movies are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201322861/olm">http://www.aanda.org
</A>

---------------------------------------------------------
Title: Erratum: "Propagating Waves Transverse to the Magnetic Field
in a Solar Prominence" <A href="/abs/2013ApJ...777..108S">(2013,
ApJ, 777, 108)</A>
Authors: Schmieder, B.; Kucera, T. A.; Knizhnik, K.; Luna, M.;
Lopez-Ariste, A.; Toot, D.
2014ApJ...781..129S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Propagating waves transverse to the magnetic field in a
solar prominence
Authors: Kucera, Therese; Schmieder, Brigitte; Knizhnik, Kalman;
Lopez-Ariste, Arturo; Luna, Manuel; Toot, David
2014IAUS..300..435K Altcode:
We have observed a quiescent prominence with the Hinode Solar Optical
Telescope (SOT) (Ca II and Hα lines), Sacramento Peak Dunn Solar
Telescope using the Universal Birefringent Filter (DST/UBF, in Hα,
Hβ and Sodium-D lines), THEMIS (Télescope Héliographique pour l
Etude du Magnétisme et des Instabilités Solaires/MTR (Multi Raies)
spectromagnetograph (He D3), and the Solar Dynamics
Observatory Atmospheric Imaging Assembly (SDO/AIA) in EUV over a 4
hour period on 2012 October 10. The small fields of view of the SOT,
DST, and MTR are centered on a large prominence footpoint extending
towards the surface. This feature appears in the larger field of view
of the AIA/304 Å filtergram as a large, quasi-vertical pillar with
loops on each side. The THEMIS/MTR data indicate that the magnetic
field in the pillar is essentially horizontal and the observations in
the optical domain show a large number of horizontally aligned features
in the pillar. The data are consistent with a model of cool prominence
plasma trapped in the dips of horizontal field lines. The SOT and DST
data show what appear to be moving wave pulses. These pulses, which
include a Doppler signature, move vertically, perpendicular to the
field direction, along quasi-vertical columns of horizontal threads in
the pillar. The pulses have a velocity of propagation of about 10 km/s,
a wavelength about 2000 km in the plane of the sky, and a period about
280 sec. We interpret these waves in terms of fast magnetosonic waves.

---------------------------------------------------------
Title: Magnetic flux emergence, flares, and coronal mass ejections
Authors: Mandrini, Cristina H.; Schmieder, Brigitte; Cristiani,
Germán; Demoulin, Pascal; Guo, Yang
2014cosp...40E1980M Altcode:
We study the violent events occurring in the cluster of two active
regions (ARs), NOAA numbers 11121 and 11123, observed in November
2010 with instruments onboard the Solar Dynamics Observatory and from
Earth. Within one day the total magnetic flux increased by 70 per
cent with the emergence of new groups of bipoles in AR 11123. These
emergences led to a very complex magnetic configuration in which around
ten solar flares, some of them accompanied by coronal mass ejections
(CMEs), occurred. A magnetic-field topology somputation indicates the
presence of null points, associated separatrices and quasi-separatrix
layers (QSLs) where magnetic reconnection is prone to occur. Based
on this analysis, we propose a scenario to explain the origin of a
low-energy event preceding a filament eruption, which is accompanied
by a two-ribbon flare and CME, and a consecutive confined flare in AR
11123. The results of our topology computation can also explain the
locations of flare ribbons in two other events, one preceding and one
following the ones just mentioned.

---------------------------------------------------------
Title: Dynamics of a prominence observed in Mg II lines by IRIS
Authors: Schmieder, Brigitte; Mein, Pierre; Dalmasse, Kévin; Tian,
Hui; Kucera, Therese; Lopez-Ariste, Arturo
2014cosp...40E2927S Altcode:
In September 2013 several prominences were observed with the IRIS
spectrograph during a 60 day-long international program. We will present
one set of observations obtained using multiple instruments on September
24. SDO/AIA and IRIS slit jaws provided images of the prominence
corresponding to different physical conditions of the transition
region between the cool plasma and the corona. The vector magnetic
field was derived from THEMIS (Tenerife) observations using the He D3
depolarisation due to the magnetic field. The inversion code (CPA) takes
into account the Hanle and the Zeeman effects. Movies from SDO/AIA in
304 A and Hinode/SOT in Ca II show the dynamics of the fine structures
in the plane of the sky. From Mg II and Si IV line spectra observed by
IRIS and H-alpha observed by the Multi-channel subtractive spectrograph
(MSDP) in the Meudon solar tower we derived the Dopplershifts of the
fine structures. The profiles of the Mg II lines are narrow (FHWM =0.15
A) and not reversed, contrary to the predictions of the theoretical
models (Paletou et al 1993). We could resolve the velocity of several
structures along the LOS with Dopplershifts as high as 60 km/s.

---------------------------------------------------------
Title: Electric current variations and 3D magnetic configuration of
coronal jets
Authors: Schmieder, Brigitte; Harra, Louise K.; Aulanier, Guillaume;
Guo, Yang; Demoulin, Pascal; Moreno-Insertis, Fernando, , Prof
2014cosp...40E2928S Altcode:
Coronal jets (EUV) were observed by SDO/AIA on September 17, 2010. HMI
and THEMIS measured the vector magnetic field from which we derived the
magnetic flux, the phostospheric velocity and the vertical electric
current. The magnetic configuration was computed with a non linear
force-free approach. The phostospheric current pattern of the recurrent
jets were associated with the quasi-separatrix layers deduced from the
magnetic extrapolation. The large twisted near-by Eiffel-tower-shape
jet was also caused by reconnection in current layers containing a
null point. This jet cannot be classified precisely within either the
quiescent or the blowout jet types. We will show the importance of
the existence of bald patches in the low atmosphere

---------------------------------------------------------
Title: A confined flare above filaments
Authors: Dalmasse, K.; Chandra, R.; Schmieder, B.; Aulanier, G.
2014IAUS..300..227D Altcode: 2013arXiv1310.0667D
We present the dynamics of two filaments and a C-class flare observed
in NOAA 11589 on 2012 October 16. We used the multi-wavelength
high-resolution data from SDO, as well as THEMIS and ARIES ground-based
observations. The observations show that the filaments are progressively
converging towards each other without merging. We find that the
filaments have opposite chirality which may have prevented them from
merging. On October 16, a C3.3 class flare occurred without the eruption
of the filaments. According to the standard solar flare model, after
the reconnection, post-flare loops form below the erupting filaments
whether the eruption fails or not. However, the observations show
the formation of post-flare loops above the filaments, which is not
consistent with the standard flare model. We analyze the topology of
the active region's magnetic field by computing the quasi-separatrix
layers (QSLs) using a linear force-free field extrapolation. We find
a good agreement between the photospheric footprints of the QSLs and
the flare ribbons. We discuss how slipping or slip-running reconnection
at the QSLs may explain the observed dynamics.

---------------------------------------------------------
Title: Einar Tandberg-Hanssen
Authors: Schmieder, Brigitte; Pecker, Jean-Claude; Gary, Allen; Wu,
S. T.; Moore, Ronald; Biesmann, Else
2014IAUS..300....4S Altcode:
I would like to report first on the scientific career of Einar
Tandberg-Hanssen: how he became a Solar Physicist particularly
interested in prominences. In the second part of my talk I will show
what he brought to the French community from the science perspective.

---------------------------------------------------------
Title: Clarifying some issues on the geoeffectiveness of limb
halo CMEs
Authors: Cid, Consuelo; Cremades, Hebe; Aran, Angels; Mandrini,
Cristina; Sanahuja, Blai; Schmieder, Brigitte; Menvielle, Michel;
Rodriguez, Luciano; Saiz, Elena; Cerrato, Yolanda; Dasso, Sergio;
Jacobs, Carla; Lathuillere, Chantal; Zhukov, Andrei
2014IAUS..300..285C Altcode:
A recent study by Cid et al. (2012) showed that full halo coronal
mass ejections (CMEs) coming from the limb can disturb the terrestrial
environment. Although this result seems to rise some controversies with
the well established theories, the fact is that the study encourages
the scientific community to perform careful multidisciplinary analysis
along the Sun-to-Earth chain to fully understand which are the solar
triggers of terrestrial disturbances. This paper aims to clarify some
of the polemical issues arisen by that paper.

---------------------------------------------------------
Title: Dynamics in the filament of september 17 2010 and in its
channel
Authors: Mein, Nicole; Mein, Pierre; Schmieder, Brigitte; Malherbe,
Jean-Marie; Roudier, Thierry
2014IAUS..300..451M Altcode:
Dynamics of a filament is investigated in Hα. Counterstreaming flows
are observed along the filament. Photospheric horizontal motions have
been computed by using a Coherent Structure Tracking algorithm in the
filament environment.

---------------------------------------------------------
Title: Proper horizontal photospheric flows below an eruptive filament
Authors: Schmieder, Brigitte; Mein, Pierre; Mein, Nicole; Roudier,
Thierry; Chandra, Ramseh
2014cosp...40E2926S Altcode:
An analysis of the proper motions using SDO/HMI continuum images with
the new version of the coherent structure tracking (CST) algorithm
developed to track the granules as well as the large scale photospheric
flows, was perfomed during three hours in a region containing a large
filament channel on September 17, 2010. Supergranules were idenfied
in the filament channel. Diverging flows inside the supergranules are
similar in and out the filament channel. Using corks, we derived the
passive scalar points and produced maps of cork distribution. The
anchorage structures with the photosphere (feet) of the filament
are located in the areas of converging flows with accumulations of
corks. Averaging the velocity vectors for each latitude we defined a
profile of the differential rotation. We conclude that the coupling
between the convection and magnetic field in the photosphere is
relatively strong. The filament experienced the convection motions
through its feet. On a large scale point-of-view the differential
rotation induced a shear of 0.1 km/s in the filament. On a small scale
point-of-view convection motions favored the interaction/cancellation of
the parasitic polarities at the base of the feet with the surrounding
network explaining the brightenings,/jets and the eruption that were
observed in the EUV filament.

---------------------------------------------------------
Title: Nature of Prominences and their role in Space Weather
Authors: Schmieder, Brigitte; Malherbe, Jean-Marie; Wu, S. T.
2014IAUS..300.....S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Topological study of active region 11158
Authors: Zhao, Jie; Li, Hui; Pariat, Etienne; Schmieder, Brigitte;
Guo, Yang; Wiegelmann, Thomas
2014IAUS..300..479Z Altcode:
With the cylindrical equal area (CEA) projection data from the
Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics
Observatory (SDO), we reconstructed the three-dimensional (3D)
magnetic fields in the corona, using a non-linear force-free field
(NLFFF) extrapolation method every 12 minutes during five days, to
calculate the squashing degree factor Q in the volume. The results
show that this AR has an hyperbolic flux tube (HFT) configuration,
a typical topology of quadrupole, which is stable even during the two
large flares (M6.6 and X2.2 class flares).

---------------------------------------------------------
Title: Nonlinear MHD waves in a Prominence Foot: Observations
and Models
Authors: Ofman, Leon; Schmieder, Brigitte; Kucera, Therese; Knizhnik,
Kalman
2014cosp...40E2338O Altcode:
Recent high-resolution observations with Hinode/SOT in Ca II emission
of a prominence on October 12, 2012 show highly dynamic small-scale
motions in the prominence material. Observations in Hα and of Doppler
shifts show similar propagating fluctuations. However the optically
thick nature of the emission lines inhibits unique quantitative
interpretation in terms of density. Nevertheless, we find evidence of
nonlinear wave activity in the prominence foot by examining the relative
magnitude of the fluctuation intensity (dI/I~ dn/n). The waves are
evident as significant density fluctuations (dn/n~O(1)) with weak height
dependence, and apparently travel upward from the chromosphere into the
prominence material with quasi-periodic fluctuations on the order of 5
minutes, and wavelengths ~&lt;2000 km. Doppler shift observations show
the transverse displacement of the propagating waves. The magnetic
field is measured with THEMIS and is found to be 5-14 G. For the
typical prominence density the corresponding fast magnetosonic speed
is ~20 km/s in qualitative agreement with the propagation speed of
the detected wave. We use 2D and 3D MHD numerical models to reproduce
the nonlinear magnetosonic waves with the typical parameters of the
prominence guided by observations. We investigate the parameter range
of the model that fits the observed properties of the waves in order
confirm the identification of the wave nature of these observations.

---------------------------------------------------------
Title: Recurrent filament eruptions and associated CMEs
Authors: Schmieder, Brigitte; Cremades, Hebe; Mandrini, Cristina;
Démoulin, Pascal; Guo, Yang
2014IAUS..300..489S Altcode:
We investigate the violent events in the cluster of two active regions
(ARs), NOAA numbers 11121 and 11123, observed on 11 November 2010
by the Solar Dynamics Observatory (SDO). Within one day the magnetic
field intensity increased by 70% with the emergence of new groups of
bipoles in AR 11123, where three filaments are seen along the complex
inversion line. The destabilization of the filaments led to flares
and CMEs. The CMEs around 08:24 UT and 17:00 UT are directly related
to the partial eruption of one filament in the new AR, as shown by a
topology computation and analysis. The other CMEs on this day are due
to either other ARs or to the destabilization of the global magnetic
configuration of the two ARs. This conclusion can be only reached by
using the three eyes of SOHO, STEREO and SDO.

---------------------------------------------------------
Title: Twisting solar coronal jet launched at the boundary of an
active region
Authors: Schmieder, B.; Guo, Y.; Moreno-Insertis, F.; Aulanier, G.;
Yelles Chaouche, L.; Nishizuka, N.; Harra, L. K.; Thalmann, J. K.;
Vargas Dominguez, S.; Liu, Y.
2013A&A...559A...1S Altcode: 2013arXiv1309.6514S
 Aims: A broad jet was observed in a weak magnetic field area
at the edge of active region NOAA 11106 that also produced other
nearby recurring and narrow jets. The peculiar shape and magnetic
environment of the broad jet raised the question of whether it was
created by the same physical processes of previously studied jets
with reconnection occurring high in the corona. Methods:
We carried out a multi-wavelength analysis using the EUV images
from the Atmospheric Imaging Assembly (AIA) and magnetic fields
from the Helioseismic and Magnetic Imager (HMI) both on-board the
Solar Dynamics Observatory, which we coupled to a high-resolution,
nonlinear force-free field extrapolation. Local correlation tracking
was used to identify the photospheric motions that triggered the jet,
and time-slices were extracted along and across the jet to unveil its
complex nature. A topological analysis of the extrapolated field was
performed and was related to the observed features. Results:
The jet consisted of many different threads that expanded in around 10
minutes to about 100 Mm in length, with the bright features in later
threads moving faster than in the early ones, reaching a maximum speed
of about 200 km s-1. Time-slice analysis revealed a striped
pattern of dark and bright strands propagating along the jet, along with
apparent damped oscillations across the jet. This is suggestive of a
(un)twisting motion in the jet, possibly an Alfvén wave. Bald patches
in field lines, low-altitude flux ropes, diverging flow patterns, and a
null point were identified at the basis of the jet. Conclusions:
Unlike classical λ or Eiffel-tower-shaped jets that appear to be caused
by reconnection in current sheets containing null points, reconnection
in regions containing bald patches seems to be crucial in triggering
the present jet. There is no observational evidence that the flux
ropes detected in the topological analysis were actually being ejected
themselves, as occurs in the violent phase of blowout jets; instead,
the jet itself may have gained the twist of the flux rope(s) through
reconnection. This event may represent a class of jets different from
the classical quiescent or blowout jets, but to reach that conclusion,
more observational and theoretical work is necessary.

---------------------------------------------------------
Title: Propagating Waves Transverse to the Magnetic Field in a
Solar Prominence
Authors: Schmieder, B.; Kucera, T. A.; Knizhnik, K.; Luna, M.;
Lopez-Ariste, A.; Toot, D.
2013ApJ...777..108S Altcode: 2013arXiv1309.1568S
We report an unusual set of observations of waves in a large prominence
pillar that consist of pulses propagating perpendicular to the
prominence magnetic field. We observe a huge quiescent prominence with
the Solar Dynamics Observatory Atmospheric Imaging Assembly in EUV on
2012 October 10 and only a part of it, the pillar, which is a foot or
barb of the prominence, with the Hinode Solar Optical Telescope (SOT;
in Ca II and Hα lines), Sac Peak (in Hα, Hβ, and Na-D lines), and
THEMIS ("Télescope Héliographique pour l' Etude du Magnétisme et des
Instabilités Solaires") with the MTR (MulTi-Raies) spectropolarimeter
(in He D3 line). The THEMIS/MTR data indicates that
the magnetic field in the pillar is essentially horizontal and the
observations in the optical domain show a large number of horizontally
aligned features on a much smaller scale than the pillar as a whole. The
data are consistent with a model of cool prominence plasma trapped in
the dips of horizontal field lines. The SOT and Sac Peak data over
the four hour observing period show vertical oscillations appearing
as wave pulses. These pulses, which include a Doppler signature,
move vertically, perpendicular to the field direction, along thin
quasi-vertical columns in the much broader pillar. The pulses have
a velocity of propagation of about 10 km s-1, a period of
about 300 s, and a wavelength around 2000 km. We interpret these waves
in terms of fast magnetosonic waves and discuss possible wave drivers.

---------------------------------------------------------
Title: Propagating Waves Transverse to the Magnetic Field in a
Solar Prominence
Authors: Kucera, Therese A.; Knizhnik, K.; Lopez Ariste, A.; Luna
Bennasar, M.; Schmieder, B.; Toot, D.
2013SPD....4410403K Altcode:
We have observed a quiescent prominence with the Hinode Solar Optical
Telescope (SOT, in Ca II and H-alpha lines), Sacramento Peak Observatory
(in H-alpha, H-beta and Sodium-D lines), and THEMIS/MTR (Télescope
Héliographique pour l'Étude du Magnétisme et des Instabilités
Solaires/MulTi Raies, providing vector magnetograms), and SDO/AIA (Solar
Dynamics Observatory Atmospheric Imaging Assembly, in EUV) over a 4 hour
period on 2012 October 10. The small fields of view of SOT, Sac Peak
and THEMIS are centered on a large pillar-like prominence footpoint
extending towards the surface. This feature appears in the larger
field of view of the 304 Å band, as a large, quasi-vertical column
with material flowing horizontally on each side. The THEMIS/MTR data
indicate that the magnetic field in the pillar is essentially horizontal
and the observations in the optical wavelengths show a large number of
horizontally aligned features on a much smaller scale than the pillar
as a whole. The data are consistent with a model of cool prominence
plasma trapped in the dips of horizontal field lines. The SOT and Sac
Peak data show what appear to be moving wave pulses. These pulses,
which include a Doppler signature, move vertically, perpendicular to
the field direction, along quasi-vertical columns. The pulses have
a velocity of propagation of about 10 km/s, a period about 260 sec,
and a wavelength around 2000 km. We interpret these waves in terms of
fast magneto-sonic waves and discuss possible wave drivers.

---------------------------------------------------------
Title: Recurrent coronal jets induced by repetitively accumulated
electric currents
Authors: Guo, Y.; Démoulin, P.; Schmieder, B.; Ding, M. D.; Vargas
Domínguez, S.; Liu, Y.
2013A&A...555A..19G Altcode: 2013arXiv1305.0902G
Context. Jets of plasma are frequently observed in the solar corona. A
self-similar recurrent behavior is observed in a fraction of them. Aims: Jets are thought to be a consequence of magnetic reconnection;
however, the physics involved is not fully understood. Therefore,
we study some jet observations with unprecedented temporal and
spatial resolutions. Methods: The extreme-ultraviolet (EUV)
jets were observed by the Atmospheric Imaging Assembly on board the
Solar Dynamics Observatory (SDO). The Helioseismic and Magnetic Imager
(HMI) on board SDO measured the vector magnetic field, from which
we derive the magnetic flux evolution, the photospheric velocity
field, and the vertical electric current evolution. The magnetic
configuration before the jets is derived by the nonlinear force-free
field extrapolation. Results: Three EUV jets recurred in about
one hour on 17 September 2010 in the following magnetic polarity
of active region 11106. We derive that the jets are above a pair of
parasitic magnetic bipoles that are continuously driven by photospheric
diverging flows. The interaction drove the buildup of electric currents,
which we observed as elongated patterns at the photospheric level. For
the first time, the high temporal cadence of the HMI allows the
evolution of such small currents to be followed. In the jet region,
we found that the integrated absolute current peaks repetitively in
phase with the 171 Å flux evolution. The current buildup and its
decay are both fast, about ten minutes each, and the current maximum
precedes the 171 Å also by about ten minutes. Then, the HMI temporal
cadence is marginally fast enough to detect such changes. 
Conclusions: The photospheric current pattern of the jets is found to
be associated with the quasi-separatrix layers deduced from the magnetic
extrapolation. From previous theoretical results, the observed diverging
flows are expected to continuously build such currents. We conclude
that the magnetic reconnection occurs periodically, in the current
layer created between the emerging bipoles and the large-scale active
region field. The periodic magnetic reconnection induced the observed
recurrent coronal jets and the decrease of the vertical electric
current magnitude. Two movies are available in electronic form
at <A href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: Solar filament eruptions and their physical role in triggering
coronal mass ejections
Authors: Schmieder, B.; Démoulin, P.; Aulanier, G.
2013AdSpR..51.1967S Altcode: 2012arXiv1212.4014S
Solar filament eruptions play a crucial role in triggering coronal
mass ejections (CMEs). More than 80% of eruptions lead to a CME. This
correlation has been studied extensively during the past solar cycles
and the last long solar minimum. The statistics made on events occurring
during the rising phase of the new solar cycle 24 is in agreement with
this finding. Both filaments and CMEs have been related to twisted
magnetic fields. Therefore, nearly all the MHD CME models include
a twisted flux tube, called a flux rope. Either the flux rope is
present long before the eruption, or it is built up by reconnection
of a sheared arcade from the beginning of the eruption.

---------------------------------------------------------
Title: The geoeffectiveness of Halo CMEs far from central meridian
Authors: Schmieder, Brigitte
2013EGUGA..15.1537S Altcode:
Fast halo CMEs are considered as the most geoeffective solar
events. When the halo CME comes with velocities higher than 1000 km/s
and originating from the Western hemisphere close to the solar center,
a large disturbance is expected at terrestrial environment. However,
large disturbances have been also associated to halo CMEs from regions
located far from central solar meridian, as Hallowing storm, related
to CMEs from active regions farther than W80 and resulting a Dst index
below -400 nT. In this work we have studied all halo CMEs of solar
cycle 23, as observed by the Solar and Heliospheric Observatory (SOHO)
mission, with solar source close to solar limb, from 60° up to 90° far
from central meridian. For this task, we have analyzed not only solar
atmosphere and the terrestrial surface, but every link in the Sun-Earth
chain. The results of this work are useful, not only for understanding
solar-terrestrial interaction, but also in order to establish the
requirements of space weather models based on solar observations.

---------------------------------------------------------
Title: SDO/AIA Prominence physical conditions
Authors: Schmieder, B.; Parenti, S.; Dudik, J.; Aulanier, G.; Heinzel,
P.; Zapior, M.; Golub, L.
2013enss.confE..27S Altcode:
SDO/AIA has carried out continuous observations of prominences in
multiple wavelengths, with high spatial and temporal resolution. These
data provide us an opportunity to understand the physical conditions
and dynamics of prominences. The surprising brightness of prominences
in some coronal lines has been well explained by the presence of
transition region lines in the bandpass of the filters (171 A, 131 A),
a result that leads us to revise our model of the transition region
of prominences and to consider a relatively dense transition region in
some prominence evolutionary phases or in some viewing orientation. An
additional aspect of prominence dynamics will be presented with a new
quasi-static MHD model proposed for bubbles and plumes. We propose
an alternative to the interpretation that thermal instabilities are
responsible for the formation of bubbles. The bubbles are found to
correspond to magnetic separatrices formed by emerging magnetic field
close to prominence footpoints.

---------------------------------------------------------
Title: The standard flare model in three dimensions. II. Upper limit
on solar flare energy
Authors: Aulanier, G.; Démoulin, P.; Schrijver, C. J.; Janvier, M.;
Pariat, E.; Schmieder, B.
2013A&A...549A..66A Altcode: 2012arXiv1212.2086A
Context. Solar flares strongly affect the Sun's atmosphere as well as
the Earth's environment. Quantifying the maximum possible energy of
solar flares of the present-day Sun, if any, is thus a key question in
heliophysics. Aims: The largest solar flares observed over the
past few decades have reached energies of a few times 1032
erg, possibly up to 1033 erg. Flares in active Sun-like
stars reach up to about 1036 erg. In the absence of direct
observations of solar flares within this range, complementary methods
of investigation are needed to assess the probability of solar flares
beyond those in the observational record. Methods: Using
historical reports for sunspot and solar active region properties
in the photosphere, we scaled to observed solar values a realistic
dimensionless 3D MHD simulation for eruptive flares, which originate
from a highly sheared bipole. This enabled us to calculate the magnetic
fluxes and flare energies in the model in a wide paramater space. 
Results: Firstly, commonly observed solar conditions lead to modeled
magnetic fluxes and flare energies that are comparable to those
estimated from observations. Secondly, we evaluate from observations
that 30% of the area of sunspot groups are typically involved in
flares. This is related to the strong fragmentation of these groups,
which naturally results from sub-photospheric convection. When the
model is scaled to 30% of the area of the largest sunspot group ever
reported, with its peak magnetic field being set to the strongest value
ever measured in a sunspot, it produces a flare with a maximum energy of
~6 × 1033 erg. Conclusions: The results of the model
suggest that the Sun is able to produce flares up to about six times as
energetic in total solar irradiance fluence as the strongest directly
observed flare of Nov. 4, 2003. Sunspot groups larger than historically
reported would yield superflares for spot pairs that would exceed tens
of degrees in extent. We thus conjecture that superflare-productive
Sun-like stars should have a much stronger dynamo than in the Sun.

---------------------------------------------------------
Title: A Multi-spacecraft View of a Giant Filament Eruption during
2009 September 26/27
Authors: Gosain, Sanjay; Schmieder, Brigitte; Artzner, Guy; Bogachev,
Sergei; Török, Tibor
2012ApJ...761...25G Altcode: 2012arXiv1210.6686G
We analyze multi-spacecraft observations of a giant filament eruption
that occurred during 2009 September 26 and 27. The filament eruption was
associated with a relatively slow coronal mass ejection. The filament
consisted of a large and a small part, and both parts erupted nearly
simultaneously. Here we focus on the eruption associated with the
larger part of the filament. The STEREO satellites were separated
by about 117° during this event, so we additionally used SoHO/EIT
and CORONAS/TESIS observations as a third eye (Earth view) to aid our
measurements. We measure the plane-of-sky trajectory of the filament as
seen from STEREO-A and TESIS viewpoints. Using a simple trigonometric
relation, we then use these measurements to estimate the true direction
of propagation of the filament which allows us to derive the true
R/R ⊙-time profile of the filament apex. Furthermore, we
develop a new tomographic method that can potentially provide a more
robust three-dimensional (3D) reconstruction by exploiting multiple
simultaneous views. We apply this method also to investigate the 3D
evolution of the top part of filament. We expect this method to be
useful when SDO and STEREO observations are combined. We then analyze
the kinematics of the eruptive filament during its rapid acceleration
phase by fitting different functional forms to the height-time
data derived from the two methods. We find that for both methods an
exponential function fits the rise profile of the filament slightly
better than parabolic or cubic functions. Finally, we confront these
results with the predictions of theoretical eruption models.

---------------------------------------------------------
Title: Magnetic Topology of Bubbles in Quiescent Prominences
Authors: Dudík, J.; Aulanier, G.; Schmieder, B.; Zapiór, M.;
Heinzel, P.
2012ApJ...761....9D Altcode:
We study a polar-crown prominence with a bubble and its plume observed
in several coronal filters by the SDO/AIA and in Hα by the MSDP
spectrograph in Białków (Poland) to address the following questions:
what is the brightness of prominence bubbles in EUV with respect to the
corona outside of the prominence and the prominence coronal cavity? What
is the geometry and topology of the magnetic field in the bubble? What
is the nature of the vertical threads seen within prominences? We
find that the brightness of the bubble and plume is lower than the
brightness of the corona outside of the prominence, and is similar to
that of the coronal cavity. We constructed linear force-free models of
prominences with bubbles, where the flux rope is perturbed by inclusion
of parasitic bipoles. The arcade field lines of the bipole create the
bubble, which is thus devoid of magnetic dips. Shearing the bipole or
adding a second one can lead to cusp-shaped prominences with bubbles
similar to the observed ones. The bubbles have complex magnetic
topology, with a pair of coronal magnetic null points linked by a
separator outlining the boundary between the bubble and the prominence
body. We conjecture that plume formation involves magnetic reconnection
at the separator. Depending on the viewing angle, the prominence can
appear either anvil-shaped with predominantly horizontal structures,
or cusp-shaped with predominantly vertical structuring. The latter
is an artifact of the alignment of magnetic dips with respect to the
prominence axis and the line of sight.

---------------------------------------------------------
Title: Study of an Extended EUV Filament Using SoHO/SUMER Observations
of the Hydrogen Lyman Lines. II. Lyman α Line Observed During a
Multi-wavelength Campaign
Authors: Schwartz, P.; Schmieder, B.; Heinzel, P.; Kotrč, P.
2012SoPh..281..707S Altcode: 2012SoPh..tmp..201S
A filament and its channel close to the solar disk were observed in the
complete hydrogen Lyman spectrum, and in several EUV lines by the SUMER
(Solar Ultraviolet Measurement of Emitted Radiation) and CDS (Coronal
Diagnostic Spectrometer) spectrographs on the SoHO satellite, and in
Hα by ground-based telescopes during a multi-instrument campaign in
May 2005. It was a good opportunity to get an overview of the volume
and the density of the cold plasma in the filament channel; these are
essential parameters for coronal mass ejections. We found that the
width of the filament depends on the wavelength in which the filament
is observed (around 15 arcsec in Hα, 30 arcsec in Lα, and 60 arcsec
in EUV). In Lα the filament is wider than in Hα because cool plasma,
not visible in Hα, is optically thick at the Lα line center, and its
presence blocks the coronal emission. We have derived physical plasma
properties of this filament fitting the Lyman spectra and Hα profiles
by using a 1D isobaric NLTE model. The vertical temperature profile
of the filament slab is flat (T≈7000 K) with an increase to ≈ 20
000 K at the top and the bottom of the slab. From an analysis of the
Lα and Hα source functions we have concluded that these lines are
formed over the whole filament slab. We have estimated the geometrical
filling factor in the filament channel. Its low value indicates the
presence of multi-threads.

---------------------------------------------------------
Title: Can a halo CME from the limb be geoeffective?
Authors: Cid, C.; Cremades, H.; Aran, A.; Mandrini, C.; Sanahuja,
B.; Schmieder, B.; Menvielle, M.; Rodriguez, L.; Saiz, E.; Cerrato,
Y.; Dasso, S.; Jacobs, C.; Lathuillere, C.; Zhukov, A.
2012JGRA..11711102C Altcode:
The probability for a halo coronal mass ejection (CME) to be
geoeffective is assumed to be higher the closer the CME launch site
is located to the solar central meridian. However, events far from the
central meridian may produce severe geomagnetic storms, like the case
in April 2000. In this work, we study the possible geoeffectiveness of
full halo CMEs with the source region situated at solar limb. For this
task, we select all limb full halo (LFH) CMEs that occurred during solar
cycle 23, and we search for signatures of geoeffectiveness between 1
and 5 days after the first appearance of each CME in the LASCO C2 field
of view. When signatures of geomagnetic activity are observed in the
selected time window, interplanetary data are carefully analyzed in
order to look for the cause of the geomagnetic disturbance. Finally,
a possible association between geoeffective interplanetary signatures
and every LFH CME in solar cycle 23 is checked in order to decide
on the CME's geoeffectiveness. After a detailed analysis of solar,
interplanetary, and geomagnetic data, we conclude that of the 25
investigated events, there are only four geoeffective LFH CMEs, all
coming from the west limb. The geoeffectiveness of these events seems to
be moderate, turning to intense in two of them as a result of cumulative
effects from previous mass ejections. We conclude that ejections from
solar locations close to the west limb should be considered in space
weather, at least as sources of moderate disturbances.

---------------------------------------------------------
Title: Velocity Vector, Ionization Degree, and Temperature of
Prominence Fine Structures Observed by Hinode/SOT
Authors: Schmieder, B.; Mein, P.; Chandra, R.; Molodij, G.; Heinzel,
P.; Berlicki, A.; Schwartz, P.; Fárník, F.; Labrosse, N.; Anzer,
U.; Watanabe, T.
2012ASPC..454..107S Altcode:
Prominences have been successfully observed by Hinode in April 2007
exhibiting a strong dynamics of their fine structures. The dynamics
of a prominence is a challenge to understand the formation of cool
prominence plasma embedded in the hot corona. Combining simultaneous
observations obtained in Hα with Hinode/SOT and the MSDP spectrograph
operating at the Meudon solar tower, velocity vectors have been
derived. The Doppler-shifts of bright threads are of the same order
as the velocities measured perpendicular to the line of sight. This
suggests that the vertical structures of the prominence could be a pile
up of dips in magnetic field lines viewed in 3D. Using Hα, Hinode/XRT
and TRACE data, the hydrogen ionization degree has been determined to
be 0.5-0.8, and the optical thickness in Hα between 0.2 and 1.3. The
Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode produced images
of the prominence in 11 selected lines with formation temperatures
between log(T) = 4.7 and log(T) = 6.1. We comment on the absorption,
emissivity blocking and emission involved for interpreting the different
structures of the prominence in terms of the temperature and density.

---------------------------------------------------------
Title: Reconstruction of 3D Coronal Magnetic Structures from
THEMIS/MTR and Hinode/SOT Vector Maps
Authors: Schmieder, B.; Guo, Y.; Aulanier, G.; Démoulin, P.; Török,
T.; Bommier, V.; Wiegelmann, T.; Gosain, S.
2012ASPC..454..363S Altcode:
Coordinated campaigns using THEMIS, Hinode, and other instruments have
allowed us to study the magnetic fields of faculae, filaments, and
active regions. In a first case, we modelled the 3D magnetic field in a
flaring active region with a nonlinear force-free field extrapolation,
using magnetic vectors observed by THEMIS/MTR as boundary condition. In
order to construct a consistent bottom boundary for the model, we
first removed the 180 degree ambiguity of the transverse fields and
minimized the force and torque in the observed vector fields. We found
a twisted magnetic flux rope, well aligned with the polarity inversion
line and a part of an Hα filament, and located where a large flare is
initiated about two hours later. In a second case, Hinode/SOT allowed
us to detect fine flux concentrations in faculae, while MTR provided us
with magnetic information at different levels in the atmosphere. The
polarimetry analysis of the MTR and SOT data gave consistent results,
using both UNNOFIT and MELANIE inversion codes.

---------------------------------------------------------
Title: Prominences observations with SDO/AIA
Authors: Parenti, Susanna; Schmieder, Brigitte; Golub, Leon; Heinzel,
Petr
2012cosp...39.1447P Altcode: 2012cosp.meet.1447P
The Prominence-Corona-Transition-Region (PCTR) plays a key role in
the thermal and pressure equilibrium of prominences. However, several
open issues limit our knowledge of this important interface. Among
them we find the thermal structure and the maximum temperature of
its emitting plasma. This work is a new step toward resolving these
issues. By noting that prominences may be observed in emission in
the 171 and 131 SDO/AIA images, while they are seen in absorption in
others (e.g. 193) we investigate the temperature content of these
channels. Using the CHIANTI atomic database and previously derived
prominence DEMs, we built synthetic spectra in these AIA channels to
establish the main contributors. We find that the Fe IX line always
dominates the 171 band, even in absence of a coronal plasma, while
the 131 channel is dominated by Fe VIII. Our conclusion is that the
PCTR reaches, at least, 4x 10^5 K.

---------------------------------------------------------
Title: On the Nature of Prominence Emission Observed by SDO/AIA
Authors: Parenti, S.; Schmieder, B.; Heinzel, P.; Golub, L.
2012ApJ...754...66P Altcode: 2012arXiv1205.5460P
The prominence-corona transition region (PCTR) plays a key role in the
thermal and pressure equilibrium of solar prominences. Our knowledge
of this interface is limited and several major issues remain open,
including the thermal structure and, in particular, the maximum
temperature of the detectable plasma. The high signal-to-noise
ratio of images obtained by the Atmospheric Imaging Assembly (AIA)
on NASA's Solar Dynamics Observatory clearly shows that prominences
are often seen in emission in the 171 and 131 bands. We investigate the
temperature sensitivity of these AIA bands for prominence observations,
in order to infer the temperature content in an effort to explain the
emission. Using the CHIANTI atomic database and previously determined
prominence differential emission measure distributions, we build
synthetic spectra to establish the main emission-line contributors
in the AIA bands. We find that the Fe IX line always dominates
the 171 band, even in the absence of plasma at &gt;106 K
temperatures, while the 131 band is dominated by Fe VIII. We conclude
that the PCTR has sufficient plasma emitting at &gt;4 × 105
K to be detected by AIA.

---------------------------------------------------------
Title: Can bubbles in quiescent prominences be purely magnetic
phenomena?
Authors: Dudik, Jaroslav; Schmieder, Brigitte; Aulanier, Guillaume;
Zapior, Maciej; Heinzel, Petr
2012cosp...39..486D Altcode: 2012cosp.meet..486D
We present a model of the magnetic field constituting quiescent
prominences. The model assumes a linear force-free field with a
weakly twisted flux-tube in an OX/OF topology perturbed by presence
of parasitic polarities within the filament channel. The parasitic
polarities locally create the cusp-shaped prominences with bubbles
exactly as those observed by the SDO/AIA and Bialkow Observatory. We
find that the observations are best reproduced if the parasitic bipoles
are sheared with respect to the main inversion line. We show that
the bubbles are in fact constituted by the arcade-like field lines,
as opposed to that of the prominence, which is created by magnetic
dips. A pair of null points is always associated with the parasitic
bipole. These null points are connected by a separator passing through
the prominence bubble. We show how the presence of an additional
parasitic bipole moves the separator to the boundary between the bubble
and the rest of the prominence, producing a topology favorable for
reconnection and possibly for the formation of plumes.

---------------------------------------------------------
Title: Prominence fine-structure dynamics as inferred from 2D
non-LTE models
Authors: Gunar, Stanislav; Schmieder, Brigitte; Mein, Pierre;
Heinzel, Petr
2012cosp...39..683G Altcode: 2012cosp.meet..683G
2D multi-thread prominence fine structure models are able to
produce synthetic Lyman spectra in very good agreement with spectral
observations by SOHO/SUMER including the spectral line asymmetries. The
synthetic differential emission measure curves derived from these
models are also in a good agreement with observations. Now we show that
these models are also able to produce synthetic H-alpha line profiles
in very good agreement with observations which allows us to analyze
not only the physical parameters of the prominence fine-structure
plasma but also some aspects of its dynamical behaviour. We compare
the synthetic H-alpha spectra with the observed spectra of the
April 26, 2007 prominence using three statistical parameters: the
line integrated intensity, the line full-width at the half-maximum
(FWHM), and the Doppler velocity derived from shifts of the line
profiles. This statistical analysis allows us to conclude that the
overall statistical distribution of the LOS velocities in the April 26,
2007 prominence at the time of the observations was below +/-15 km/s
and in the prominence core was close to +/-10 km/s. In combination
with the analysis of the Lyman spectra we determine several physical
parameters of the observed prominence fine structures which show that
the April 26, 2007 prominence was relatively less massive. We are also
able to put some constrains on the prominence core temperature that
might be relatively low, reaching values below 6000 K.

---------------------------------------------------------
Title: Impulsive Eruptive Flare on 23 October, 2003, from NOAA
AR 10484
Authors: Chandra, Ramesh; Schmieder, Brigitte; Cristiani, Germán.;
Mandrini, Cristina H.; Joshi, Bhuwan; Srivastava, Abhishek K.;
Uddin, Wahab
2012cosp...39..302C Altcode: 2012cosp.meet..302C
No abstract at ADS

---------------------------------------------------------
Title: Solar filament eruptions and their physical role in triggering
CMEs
Authors: Schmieder, Brigitte
2012cosp...39.1723S Altcode: 2012cosp.meet.1723S
CMEs are due to physical phenomena that drive both, eruptions and
flares in active regions. Eruptions/CMEs must be driven from initially
force-free current-carrying magnetic field. Twisted flux ropes,
sigmoids, current lanes and pattern in photospheric current maps show
a clear evidence of currents parallel to the magnetic field. Eruptions
occur starting from equilibriums , which have reached some instability
threshold. Boundary motions related to magnetic flux emergence and
shearing favour the increase of coronal currents leading to the large
flares. On the other hand, during the rising solar cycle phase,
filament eruptions are characterized by a gradual (slow) and weak
acceleration and therefore not accompanied by significant flaring. The
gradual acceleration is due to a rather shallow profile of the overlying
magnetic field. As the solar cycle is progressing, the magnetic field
increases and stronger flares may occur due to the diffusion of the
magnetic field, then reducing the magnetic tension. The basic driving
mechanism is the torus instability or loss of equilibrium in both
types of eruptions.

---------------------------------------------------------
Title: The standard flare model in three dimensions. I. Strong-to-weak
shear transition in post-flare loops
Authors: Aulanier, G.; Janvier, M.; Schmieder, B.
2012A&A...543A.110A Altcode:
Context. The standard CSHKP model for eruptive flares is
two-dimensional. Yet observational interpretations of photospheric
currents in pre-eruptive sigmoids, shear in post-flare loops, and
relative positioning and shapes of flare ribbons, all together require
three-dimensional extensions to the model. Aims: We focus on
the strong-to-weak shear transition in post-flare loops, and on the
time-evolution of the geometry of photospheric electric currents, which
occur during the development of eruptive flares. The objective is to
understand the three-dimensional physical processes, which cause them,
and to know how much the post-flare and the pre-eruptive distributions
of shear depend on each other. Methods: The strong-to-weak shear
transition in post-flare loops is identified and quantified in a flare
observed by STEREO, as well as in a magnetohydrodynamic simulation
of CME initiation performed with the OHM code. In both approaches,
the magnetic shear is evaluated with field line footpoints. In the
simulation, the shear is also estimated from ratios between magnetic
field components. Results: The modeled strong-to-weak shear
transition in post-flare loops comes from two effects. Firstly,
a reconnection-driven transfer of the differential magnetic shear,
from the pre- to the post-eruptive configuration. Secondly, a vertical
straightening of the inner legs of the CME, which induces an outer shear
weakening. The model also predicts the occurrence of narrow electric
current layers inside J-shaped flare ribbons, which are dominated
by direct currents. Finally, the simulation naturally accounts for
energetics and time-scales for weak and strong flares, when typical
scalings for young and decaying solar active regions are applied. Conclusions: The results provide three-dimensional extensions to
the standard flare model. These extensions involve MHD processes that
should be tested with observations.

---------------------------------------------------------
Title: Topology analysis of emerging bipole clusters producing
violent solar events observed by SDO
Authors: Schmieder, Brigitte; Demoulin, Pascal; Mandrini, Cristina H.;
Guo, Yang
2012cosp...39.1724S Altcode: 2012cosp.meet.1724S
During the rising phase of Solar Cycle 24, tremendous magnetic solar
activity occurs on the Sun with fast and compact emergence of magnetic
flux leading to burts of flares (C to M and even X class) . We have
investigated the violent events occuring in the cluster of two active
regions AR 11121 and AR11123 observed in November by SDO. In less
than two days the magnetic field increases by a factor of 10 with
the emergence of groups of bipoles. A topology analysis demonstrates
the formation of multiple separatrices and quasi-separatrix layers
explaining possible mechanisms for destabilization of the magnetic
structures such as filaments and coronal loops.

---------------------------------------------------------
Title: Slip-running reconnection and evolution of shear in post-flare
loops
Authors: Janvier, Miho; Schmieder, Brigitte; Pariat, Etienne;
Aulanier, Guillaume
2012cosp...39..816J Altcode: 2012cosp.meet..816J
We analyze the physical mechanisms of an eruptive flare via 3D
magnetohydrodynamic simulations of a flux rope. We focus on the
relaxation process associated with the reconnection of magnetic field
lines driven by the free expansion of the magnetic field. First, the
origin of the shearing of post-flare magnetic loops is investigated
in relation to the pre-flare geometry of the magnetic field. Indeed,
space-borne satellites can observe the temporal changes of post-flare
structures that are important observational manifestations of the
solar flare phenomenon. As such, understanding the evolution of
post-flare loops can reveal the characteristics of the pre-flare
magnetic field. Here, we introduce different proxies to quantify
the shear angle. We show that strong geometrical similarities exist
between the initial magnetic field and the post-flare loops. Analysis
of the eruption dynamics shows that magnetic reconnection at the origin
of the post-flare field lines forms less and less sheared magnetic
loops on top of one another. We confirm this tendency by direct
measurements of the shear angle seen in flare events such as that
of May 9, 2011 recorded by STEREO-B/EUVI. Our results also highlight
that vertical stretching of the magnetic field lines may play a role
in the shear angle evolution of post-flare loops. The analysis of
the eruptive flare evolution is followed by a detailed investigation
of the flux rope growth and of the post-flare loops formation due to
coronal slip-running reconnection. For that, we study the dynamics of
different regions around two ribbons of opposite current. We find that
these ribbons correspond to quasi-separatrix layers (QSLs), associated
with J-shaped pre-flare magnetic field lines, reconnected S-shaped
flux rope lines and post-flare loops. Simulations with very small time
steps are required so as to show the detailed time evolution of those
QSLs as well as the time variations of the slip-running velocities. Our
results provide a fully 3D extension of the standard 2D flare model.

---------------------------------------------------------
Title: Dynamics of quiescent prominence fine structures analyzed by
2D non-LTE modelling of the Hα line
Authors: Gunár, S.; Mein, P.; Schmieder, B.; Heinzel, P.; Mein, N.
2012A&A...543A..93G Altcode:
 Aims: We analyze the dynamics of the prominence fine
structures of a quiescent prominence observed on April 26, 2007
during a coordinated campaign of several spaceborne and ground-based
instruments. We use Lyman spectra observed by SOHO/SUMER and the
Hα line spectra obtained by MSDP spectrograph working at the
Meudon Solar Tower. Methods: We employ the 2D multi-thread
prominence fine-structure modelling that includes randomly distributed
line-of-sight (LOS) velocities of individual threads to derive models
producing synthetic Lyman lines in good agreement with the SOHO/SUMER
observations. We then use these models to produce synthetic Hα
line spectra that we compare with the observed spectra using three
statistical parameters: the line integrated intensity, the line
full-width at half-maximum (FWHM), and the Doppler velocity derived
from shifts of the line profiles. Results: We demonstrate that
the 2D multi-thread models that produce synthetic Lyman spectra in
agreement with observations also generate synthetic Hα spectra in
good agreement with the observed ones. The statistical analysis of the
FWHM and Doppler velocities of the synthetic Hα line profiles show
that the overall LOS velocities in the April 26, 2007 prominence at
the time of the observations were below 15 km s-1 and in
the prominence core were close to 10 km s-1. In combination
with the analysis of the Lyman spectra, we determine several physical
parameters of the observed prominence fine-structures that show
that the April 26, 2007 prominence had a relatively low-mass weakly
magnetized structure. We are also able to impose some constraints
on the prominence core temperature, which may be relatively low,
with values below 6000 K. Conclusions: The combination of
2D non-LTE prominence fine-structure modelling with the statistical
analysis of the observed and synthetic Lyman and Hα spectra allows us
to analyze the influence of the model input parameters and the velocity
fields on the synthetic Hα line profiles, thus determine the overall
dynamics of the observed prominence as well as the physical parameters
of its plasma. Appendix A is available in electronic form at <A
href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: Resistive magnetic flux emergence and formation of solar
active regions
Authors: Pariat, E.; Schmieder, B.; Masson, S.; Aulanier, G.
2012EAS....55..115P Altcode:
Magnetic flux emergence as the mechanism leading to the formation of
magnetized structures in the solar atmosphere plays a key role in the
dynamic of the Sun. Observed as a whole, emerging flux regions show
clear signs of twisted structure, bearing the magnetic free energy
necessary to power active events. The high resolution observations
of the recent solar observatories (e.g. Hinode, SDO) have revealed
how intermittent the magnetic field appears and how various active
events induced by flux emergence are. Magnetic field reconstructions
methods show that the topology of the field in interspot regions
presents a serpentine structure, i.e. field lines having successive U
and Ω parts. Associated with the appearance of magnetic polarities,
a tremendous number of brief small scale brightening are observed
in different photospheric and chromospheric lines, e.g. Ellerman
Bombs, along with small scale jet-like structures. These events are
believed to be the observational signatures of the multiple magnetic
reconnections which enable the magnetic field to emerge further up
and magnetically structure the corona above active region. Meanwhile
a world-wide effort to numerically model the emergence of magnetic
field forming solar active region is been carried on. Using different
types of physical paradigm - e.g. idealized magnetohydrodynamic model,
advanced treatment of the physical equations, data-driven simulations
- these numerical experiments highlight how electric currents can
build-up during flux emergence, lead to reconnection and thus explain
the formation of the different observed transients.

---------------------------------------------------------
Title: What are the physical mechanisms of eruptions and CMEs?
Authors: Schmieder, Brigitte; Aulanier, Guillaume
2012AdSpR..49.1598S Altcode:
CMEs are due to physical phenomena that drive both, eruptions and
flares in active regions. Eruptions/CMEs must be driven from initially
force-free current-carrying magnetic field. Twisted flux ropes,
sigmoids, current lanes and pattern in photospheric current maps show
a clear evidence of currents parallel to the magnetic field. Eruptions
occur starting from equilibria which have reached some instability
threshold. Revisiting several data sets of CME observations we
identified different mechanisms leading to this unstable state from a
force free field. Boundary motions related to magnetic flux emergence
and shearing favor the increase of coronal currents leading to the
large flares of November 2003. On the other hand, we demonstrated by
numerical simulations that magnetic flux emergence is not a sufficient
condition for eruptions. Filament eruptions are interpreted either
by a torus instability for an event occurring during the minimum of
solar activity either by the diffusion of the magnetic flux reducing
the tension of the restraining arcade. We concluded that CME models
(tether cutting, break out, loss of equilibrium models) are based on
these basic mechanisms for the onset of CMEs.

---------------------------------------------------------
Title: Observations of Multiple Surges Associated with Magnetic
Activities in AR 10484 on 2003 October 25
Authors: Uddin, Wahab; Schmieder, B.; Chandra, R.; Srivastava,
Abhishek K.; Kumar, Pankaj; Bisht, S.
2012ApJ...752...70U Altcode: 2012arXiv1204.2053U
We present a multi-wavelength study of recurrent surges observed in
Hα, UV (Solar and Heliospheric Observatory (SOHO)/EIT), and Radio
(Learmonth, Australia) from the super-active region NOAA 10484 on
2003 October 25. Several bright structures visible in Hα and UV
corresponding to subflares are also observed at the base of each
surge. Type III bursts are triggered and RHESSI X-ray sources are
evident with surge activity. The major surge consists of bunches of
ejective paths forming a fan-shaped region with an angular size of
(≈65°) during its maximum phase. The ejection speed reaches up to
~200 km s-1. The SOHO/Michelson Doppler Imager magnetograms
reveal that a large dipole emerges from the east side of the active
region on 2003 October 18-20, a few days before the surges. On 2003
October 25, the major sunspots were surrounded by "moat regions"
with moving magnetic features (MMFs). Parasitic fragmented positive
polarities were pushed by the ambient dispersion motion of the MMFs
and annihilated with negative polarities at the borders of the moat
region of the following spot to produce flares and surges. A topology
analysis of the global Sun using Potential Field Source Surface shows
that the fan structures visible in the EIT 171 Å images follow magnetic
field lines connecting the present active region to a preceding active
region in the southeast. Radio observations of Type III bursts indicate
that they are coincident with the surges, suggesting that magnetic
reconnection is the driver mechanism. The magnetic energy released by
the reconnection is transformed into plasma heating and provides the
kinetic energy for the ejections. A lack of a radio signature in the
high corona suggests that the surges are confined to follow the closed
field lines in the fans. We conclude that these cool surges may have
some local heating effects in the closed loops, but probably play a
minor role in global coronal heating and the surge material does not
escape to the solar wind.

---------------------------------------------------------
Title: Electric current density and related sigmoid in an active
region
Authors: Joulin, V.; Schmieder, B.; Aulanier, G.; Bommier, V.
2012EAS....55..143J Altcode:
Using THEMIS vector magnetograms we measured vertical electric current
density in the leading sunspot of NOAA 11127 active region during
its disk passage. The current structures evolve versus time. MHD
modelling allows us to explain the spiral pattern by torsion. We found
observational visible counterparts in the SDO/AIA 335 A images. The
field lines are visible as loops in the AIA images. When the torsion
is increasing, a sigmoid is observed. In the present event observed
on November 24th 2010, we find that reconnection is also necessary to
explain their sigmoidal shape.

---------------------------------------------------------
Title: New perspectives on solar prominences
Authors: Schmieder, B.; Aulanier, G.
2012EAS....55..149S Altcode:
Recent observations of prominences obtained with high spatial and
temporal resolution instruments, on board satellites (Hinode, SDO) as
well as on the ground (SST) have provided very intriguing movies and
open a new area for understanding the nature of prominences. The main
topics are still debate: formation, dynamics, and characteristics of the
plasma in the core and in the transition zone between the prominence
and corona. We will review briefly the recent advances made in these
topics, observationally as well as theoretically.

---------------------------------------------------------
Title: Magnetic Field Structures in a Facular Region Derived from
THEMIS and Hinode Vector Magnetic Field
Authors: Guo, Y.; Schmieder, B.; Bommier, V.; Mein, P.
2012ASPC..456...55G Altcode:
In order to compare vector magnetic fields obtained by two spectral
polarimeters (THEMIS/MTR and Hinode SOT/SP) and two inversion codes
(UNNOFIT and MELANIE), we observed a facular region in the active region
NOAA 10996 on 2008 May 23. We found that they give consistent results
concerning the distributions of field strengths, azimuth and inclination
angles. SOT/SP could resolve small magnetic polarities with sizes of
1” to 2”, and detect convergence and divergence of the horizontal
components of magnetic fields in the facular cells. These findings
support the models suggesting the existence of flux tube bundles
in faculae. With this model and multi spectral line observations,
we could infer the relative formation heights of those spectral lines.

---------------------------------------------------------
Title: On the Visibility of Solar Prominences in SDO/AIA Channels
Authors: Heinzel, P.; Schmieder, B.; Parenti, S.; Golub, L.
2012ASPC..456...75H Altcode:
Prominences in EUV lines are observed as dark structures over the
limb due absorption and emission blocking mechanisms. However, at 171
Å is observed emission in prominences with TRACE and SDO/AIA, and
it is believed to be due to the prominence-corona transition region
(PCTR) emitting in cool lines. To check this, we use the Differential
Emission Measure (DEM) recently obtained for quiescent prominences
using SOHO/SUMER spectra (Parenti and Vial 2007) and compute the
synthetic spectra in selected AIA channels. We then compare 171 Å and
195 Å channels and derive conclusions concerning the PCTR emissivity,
as well well as the absorption and blocking. The emission seen in the
171 Å channel can be used to better constrain prominence DEM curves.

---------------------------------------------------------
Title: On the Nature of Prominence Bubbles and Plumes
Authors: Schmieder, B.; Zapior, M.; Heinzel, P.; Aulanier, G.
2012ASPC..456...77S Altcode:
An example of bubble and related plume, using time series in
selected SDO/AIA channels and co-temporal MSDP observations in the
Hα line obtained at Wroclaw-Bialkow observatory on April 20, 2011 is
presented. The formation of bubbles may be due to emerging arcades in
the filament channel, below the prominence. After discussing on MHD
modeling, we conclude that bubbles and plumes are parts of the corona
observed through gaps/windows in the prominence.

---------------------------------------------------------
Title: Temperature Diagnostic of a Brightening Observed by Hinode/XRT
Authors: Dudík, J.; Reeves, K. K.; Schmieder, B.; Dzifčáková,
E.; Golub, L.
2012ASPC..456..137D Altcode:
We analyze the temperature distribution of the active region brightening
observed by HINODE/XRT. The temperature structure is derived using
various filter-ratio techniques and DEM analysis. The results are
compared and it is found that the filter-ratio techniques are accurate
only for relatively narrow DEMs.

---------------------------------------------------------
Title: Evolution of Hard X-Ray Sources and Ultraviolet Solar Flare
Ribbons for a Confined Eruption of a Magnetic Flux Rope
Authors: Guo, Y.; Ding, M. D.; Schmieder, B.; Démoulin, P.; Li, H.
2012ApJ...746...17G Altcode: 2011arXiv1111.1790G
We study the magnetic field structures of hard X-ray (HXR) sources and
flare ribbons of the M1.1 flare in active region NOAA 10767 on 2005 May
27. We have found in a nonlinear force-free field extrapolation over the
same polarity inversion line, a small pre-eruptive magnetic flux rope
located next to sheared magnetic arcades. RHESSI and the Transition
Region and Coronal Explorer (TRACE) observed this confined flare in
the X-ray bands and ultraviolet (UV) 1600 Å bands, respectively. In
this event magnetic reconnection occurred at several locations. It
first started at the location of the pre-eruptive flux rope. Then,
the observations indicate that magnetic reconnection occurred between
the pre-eruptive magnetic flux rope and the sheared magnetic arcades
more than 10 minutes before the flare peak. This implies the formation
of the larger flux rope, as observed with TRACE. Next, HXR sources
appeared at the footpoints of this larger flux rope at the peak of the
flare. The associated high-energy particles may have been accelerated
below the flux rope in or around a reconnection region. Still, the close
spatial association between the HXR sources and the flux rope footpoints
favors an acceleration within the flux rope. Finally, a topological
analysis of a large solar region, including active regions NOAA 10766
and 10767, shows the existence of large-scale Quasi-Separatrix Layers
(QSLs) before the eruption of the flux rope. No enhanced emission was
found at these QSLs during the flare, but the UV flare ribbons stopped
at the border of the closest large-scale QSL.

---------------------------------------------------------
Title: Multi-wavelength observations to understand the solar magnetic
activity and its feedback on the interplanetary medium
Authors: Molodij, G.; Schmieder, B.; Bommier, V.
2012mfu3.conf...93M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A filament supported by different magnetic field configurations
Authors: Guo, Y.; Schmieder, B.; Démoulin, P.; Wiegelmann, T.;
Aulanier, G.; Török, T.; Bommier, V.
2011IAUS..273..328G Altcode:
A nonlinear force-free magnetic field extrapolation of vector
magnetogram data obtained by THEMIS/MTR on 2005 May 27 suggests the
simultaneous existence of different magnetic configurations within
one active region filament: one part of the filament is supported by
field line dips within a flux rope, while the other part is located
in dips within an arcade structure. Although the axial field chirality
(dextral) and the magnetic helicity (negative) are the same along the
whole filament, the chiralities of the filament barbs at different
sections are opposite, i.e., right-bearing in the flux rope part and
left-bearing in the arcade part. This argues against past suggestions
that different barb chiralities imply different signs of helicity of
the underlying magnetic field. This new finding about the chirality of
filaments will be useful to associate eruptive filaments and magnetic
cloud using the helicity parameter in the Space Weather Science.

---------------------------------------------------------
Title: Solar activity due to magnetic complexity of active regions
Authors: Schmieder, Brigitte; Mandrini, Cristina; Chandra, Ramesh;
Démoulin, Pascal; Török, Tibor; Pariat, Etienne; Uddin, Wahab
2011IAUS..273..164S Altcode:
Active regions (ARs), involved in the Halloween events during
October-November 2003, were the source of unusual activity during
the following solar rotation. The flares on 18-20 November 2003 that
occur in the AR NOAA10501 were accompanied by coronal mass ejections
associated to some particularly geoeffective magnetic clouds. Our
analysis of the magnetic flux and helicity injection revealed that
a new emerging bipole and consequent shearing motions continuously
energized the region during its disk passage. The stored energy was
eventually released through the interaction of the various systems
of magnetic loops by several magnetic reconnection events. Active
events on November 18 (filament eruptions and CMEs) were originated by
shearing motions along a section of the filament channel that injected
magnetic helicity with sign opposite to that of the AR. Two homologous
flares, that occurred on November 20, were apparently triggered by
different mechanisms as inferred from the flare ribbons evolution
(filament eruption and CMEs). We studied in detail the behaviour of
two North-South oriented filaments on November 20 2003. They merged
and split following a process suggestive of `sling-shot' reconnection
between two coronal flux ropes. We successfully tested this scenario
in a 3D MHD simulation that is presented in this paper.

---------------------------------------------------------
Title: Vector magnetic field and vector current density in and around
the δ-spot NOAA 10808†
Authors: Bommier, Véronique; Landi Degl'Innocenti, Egidio; Schmieder,
Brigitte; Gelly, Bernard
2011IAUS..273..338B Altcode:
The context is that of the so-called “fundamental ambiguity”
(also azimuth ambiguity, or 180° ambiguity) in magnetic field
vector measurements: two field vectors symmetrical with respect to
the line-of-sight have the same polarimetric signature, so that they
cannot be discriminated. We propose a method to solve this ambiguity by
applying the “simulated annealing” algorithm to the minimization of
the field divergence, added to the longitudinal current absolute value,
the line-of-sight derivative of the magnetic field being inferred by the
interpretation of the Zeeman effect observed by spectropolarimetry in
two lines formed at different depths. We find that the line pair Fe I
λ 6301.5 and Fe I λ 6302.5 is appropriate for this purpose. We treat
the example case of the δ-spot of NOAA 10808 observed on 13 September
2005 between 14:25 and 15:25 UT with the THEMIS telescope. Besides the
magnetic field resolved map, the electric current density vector map
is also obtained. A strong horizontal current density flow is found
surrounding each spot inside its penumbra, associated to a non-zero
Lorentz force centripetal with respect to the spot center (i.e.,
oriented towards the spot center). The current wrapping direction
is found to depend on the spot polarity: clockwise for the positive
polarity, counterclockwise for the negative one. This analysis is made
possible thanks to the UNNOFIT2 Milne-Eddington inversion code, where
the usual theory is generalized to the case of a line (Fe I λ 6301.5)
that is not a normal Zeeman triplet line (like Fe I λ 6302.5).

---------------------------------------------------------
Title: EUV lines observed with EIS/Hinode in a solar prominence
Authors: Labrosse, N.; Schmieder, B.; Heinzel, P.; Watanabe, T.
2011A&A...531A..69L Altcode: 2011arXiv1105.1400L
Context. During a multi-wavelength observation campaign with Hinode
and ground-based instruments, a solar prominence was observed for
three consecutive days as it crossed the western limb of the Sun
in April 2007. Aims: We report on observations obtained on
26 April 2007 using EIS (Extreme ultraviolet Imaging Spectrometer)
on Hinode. They are analysed to provide a qualitative diagnostic
of the plasma in different parts of the prominence. Methods:
After correcting for instrumental effects, the rasters at different
wavelengths are presented. Several regions within the same prominence
are identified for further analysis. Selected profiles for lines
with formation temperatures between log (T) = 4.7 and log (T) = 6.3,
as well as their integrated intensities, are given. The profiles of
coronal, transition region, and He ii lines are discussed. We pay
special attention to the He ii line, which is blended with coronal
lines. Results: Some quantitative results are obtained by
analysing the line profiles. They confirm that depression in EUV lines
can be interpreted in terms of two mechanisms: absorption of coronal
radiation by the hydrogen and neutral helium resonance continua, and
emissivity blocking. We present estimates of the He ii line integrated
intensity in different parts of the prominence according to different
scenarios for the relative contribution of absorption and emissivity
blocking to the coronal lines blended with the He ii line. We estimate
the contribution of the He ii 256.32 Å line to the He ii raster image
to vary between ~44% and 70% of the raster's total intensity in the
prominence according to the different models used to take into account
the blending coronal lines. The inferred integrated intensities of
the He ii 256 Å line are consistent with the theoretical intensities
obtained with previous 1D non-LTE radiative transfer calculations,
yielding a preliminary estimate of the central temperature of 8700 K,
a central pressure of 0.33 dyn cm-2, and a column mass of
2.5 × 10-4 g cm-2. The corresponding theoretical
hydrogen column density (1020 cm-2) is about
two orders of magnitude higher than those inferred from the opacity
estimates at 195 Å. The non-LTE calculations indicate that the He
ii 256.32 Å line is essentially formed in the prominence-to-corona
transition region by resonant scattering of the incident radiation. The movie associated to Fig. 2 is available in electronic form at
<A href="http://www.aanda.org">http://www.aanda.org</A>

---------------------------------------------------------
Title: 2D radiative-magnetohydrostatic model of a prominence observed
by Hinode, SoHO/SUMER and Meudon/MSDP
Authors: Berlicki, A.; Gunar, S.; Heinzel, P.; Schmieder, B.;
Schwartz, P.
2011A&A...530A.143B Altcode:
 Aims: Prominences observed by Hinode show very dynamical and
intriguing structures. To understand the mechanisms that are responsible
for these moving structures, it is important to know the physical
conditions that prevail in fine-structure threads. In the present work
we analyse a quiescent prominence with fine structures, which exhibits
dynamic behaviour, which was observed in the hydrogen Hα line with
Hinode/SOT, Meudon/MSDP and Ondřejov/HSFA2, and simultaneously in
hydrogen Lyman lines with SoHO/SUMER during a coordinated campaign. We
derive the fine-structure physical parameters of this prominence and
also address the questions of the role of the magnetic dips and of
the interpretation of the flows. Methods: We calibrate the
SoHO/SUMER and Meudon/MSDP data and obtain the line profiles of the
hydrogen Lyman series (Lβ to L6), the Ciii (977.03 Å) and Svi (933.40
Å), and Hα along the slit of SoHO/SUMER that crosses the Hinode/SOT
prominence. We employ a complex 2D radiation-magnetohydrostatic (RMHS)
modelling technique to properly interpret the observed spectral
lines and derive the physical parameters of interest. The model
was constrained not only with integrated intensities of the lines,
but also with the hydrogen line profiles. Results: The slit
of SoHO/SUMER is crossing different prominence structures: threads
and dark bubbles. Comparing the observed integrated intensities, the
depressions of Hα bubbles are clearly identified in the Lyman, Ciii,
and Svi lines. To fit the observations, we propose a new 2D model
with the following parameters: T = 8000 K, pcen = 0.035
dyn cm-2, B = 5 Gauss, ne = 1010
cm-3, 40 threads each 1000 km wide, plasma β is 3.5 ×
10-2. Conclusions: The analysis of Ciii and Svi
emission in dark Hα bubbles allows us to conclude that there is no
excess of a hotter plasma in these bubbles. The new 2D model allows us
to diagnose the orientation of the magnetic field versus the LOS. The
40 threads are integrated along the LOS. We demonstrate that integrated
intensities alone are not sufficient to derive the realistic physical
parameters of the prominence. The profiles of the Lyman lines and also
those of the Hα line are necessary to constrain 2D RMHS models. The
magnetic field in threads is horizontal, perpendicular to the LOS,
and in the form of shallow dips. With this geometry the dynamics of
fine structures in prominences could be interpreted by a shrinkage of
the quasi-horizontal magnetic field lines and apparently is not caused
by the quasi-vertical bulk flows of the plasma, as Hinode/SOT movies
seemingly suggest.

---------------------------------------------------------
Title: Actors of the main activity in large complex centres during
the 23 solar cycle maximum
Authors: Schmieder, B.; Démoulin, P.; Pariat, E.; Török, T.;
Molodij, G.; Mandrini, C. H.; Dasso, S.; Chandra, R.; Uddin, W.;
Kumar, P.; Manoharan, P. K.; Venkatakrishnan, P.; Srivastava, N.
2011AdSpR..47.2081S Altcode:
During the maximum of Solar Cycle 23, large active regions had a long
life, spanning several solar rotations, and produced large numbers of
X-class flares and CMEs, some of them associated to magnetic clouds
(MCs). This is the case for the Halloween active regions in 2003. The
most geoeffective MC of the cycle (Dst = -457) had its source during
the disk passage of one of these active regions (NOAA 10501) on
18 November 2003. Such an activity was presumably due to continuous
emerging magnetic flux that was observed during this passage. Moreover,
the region exhibited a complex topology with multiple domains of
different magnetic helicities. The complexity was observed to reach
such unprecedented levels that a detailed multi-wavelength analysis
is necessary to precisely identify the solar sources of CMEs and
MCs. Magnetic clouds are identified using in situ measurements and
interplanetary scintillation (IPS) data. Results from these two
different sets of data are also compared.

---------------------------------------------------------
Title: Magnetic Field, Density Current, and Lorentz Force Full Vector
Maps of the NOAA 10808 Double Sunspot: Evidence of Strong Horizontal
Current Flows in the Penumbra
Authors: Bommier, V.; Landi Degl'Innocenti, E.; Schmieder, B.;
Gelly, B.
2011ASPC..437..491B Altcode:
The context is that of the so-called “fundamental ambiguity”
(also azimuth ambiguity, or 180° ambiguity) in magnetic field
vector measurements: two field vectors symmetrical with respect to
the line-of-sight have the same polarimetric signature, so that they
cannot be discriminated. We propose a method to solve this ambiguity by
applying the “simulated annealing” algorithm to the minimization of
the field divergence, added to the longitudinal current absolute value,
the line-of-sight derivative of the magnetic field being inferred by the
interpretation of the Zeeman effect observed by spectropolarimetry in
two lines formed at different depths. We find that the line pair Fe I
λ 6301.5 and Fe I λ 6302.5 is appropriate for this purpose. We treat
the example case of the δ-spot of NOAA 10808 observed on 13 September
2005 between 14:25 and 15:25 UT with the THEMIS telescope. Besides the
magnetic field resolved map, the electric current density vector map
is also obtained. A strong horizontal current density flow is found
surrounding each spot inside its penumbra, associated to a non-zero
Lorentz force centripetal with respect to the spot center (i.e.,
oriented towards the spot center). The current wrapping direction
is found to depend on the spot polarity: clockwise for the positive
polarity, counterclockwise for the negative one. This analysis is made
possible thanks to the UNNOFIT2 Milne-Eddington inversion code, where
the usual theory is generalized to the case of a line Fe I λ 6301.5)
that is not a normal Zeeman triplet line (like Fe I λ 6302.5).

---------------------------------------------------------
Title: Homologous Flares and Magnetic Field Topology in Active Region
NOAA 10501 on 20 November 2003
Authors: Chandra, R.; Schmieder, B.; Mandrini, C. H.; Démoulin, P.;
Pariat, E.; Török, T.; Uddin, W.
2011SoPh..269...83C Altcode: 2010arXiv1011.1187C; 2010SoPh..tmp..249C
We present and interpret observations of two morphologically homologous
flares that occurred in active region (AR) NOAA 10501 on 20 November
2003. Both flares displayed four homologous Hα ribbons and were
both accompanied by coronal mass ejections (CMEs). The central flare
ribbons were located at the site of an emerging bipole in the centre
of the active region. The negative polarity of this bipole fragmented
in two main pieces, one rotating around the positive polarity by
≈ 110° within 32 hours. We model the coronal magnetic field and
compute its topology, using as boundary condition the magnetogram
closest in time to each flare. In particular, we calculate the
location of quasi-separatrix layers (QSLs) in order to understand the
connectivity between the flare ribbons. Though several polarities were
present in AR 10501, the global magnetic field topology corresponds
to a quadrupolar magnetic field distribution without magnetic null
points. For both flares, the photospheric traces of QSLs are similar
and match well the locations of the four Hα ribbons. This globally
unchanged topology and the continuous shearing by the rotating bipole
are two key factors responsible for the flare homology. However, our
analyses also indicate that different magnetic connectivity domains
of the quadrupolar configuration become unstable during each flare,
so that magnetic reconnection proceeds differently in both events.

---------------------------------------------------------
Title: Filament Interaction Modeled by Flux Rope Reconnection
Authors: Török, T.; Chandra, R.; Pariat, E.; Démoulin, P.;
Schmieder, B.; Aulanier, G.; Linton, M. G.; Mandrini, C. H.
2011ApJ...728...65T Altcode:
Hα observations of solar active region NOAA 10501 on 2003 November
20 revealed a very uncommon dynamic process: during the development
of a nearby flare, two adjacent elongated filaments approached each
other, merged at their middle sections, and separated again, thereby
forming stable configurations with new footpoint connections. The
observed dynamic pattern is indicative of "slingshot" reconnection
between two magnetic flux ropes. We test this scenario by means
of a three-dimensional zero β magnetohydrodynamic simulation,
using a modified version of the coronal flux rope model by Titov
and Démoulin as the initial condition for the magnetic field. To
this end, a configuration is constructed that contains two flux
ropes which are oriented side-by-side and are embedded in an ambient
potential field. The choice of the magnetic orientation of the flux
ropes and of the topology of the potential field is guided by the
observations. Quasi-static boundary flows are then imposed to bring
the middle sections of the flux ropes into contact. After sufficient
driving, the ropes reconnect and two new flux ropes are formed,
which now connect the former adjacent flux rope footpoints of opposite
polarity. The corresponding evolution of filament material is modeled
by calculating the positions of field line dips at all times. The dips
follow the morphological evolution of the flux ropes, in qualitative
agreement with the observed filaments.

---------------------------------------------------------
Title: Driving mechanism of a failed eruption
Authors: Guo, Y.; Ding, M. D.; Schmieder, B.; Li, H.; Törö, T.;
Wiegelmann, T.
2011ASInC...2..307G Altcode:
We find a magnetic flux rope before the M1.1 flare in active
region 10767 on 2005 May 27 by a nonlinear force-free field
extrapolation. TRACE observations of the filament eruption show that the
erupting structure performed a writhing deformation and stopped rising
at a certain height, suggesting that the flux rope converted some of its
twist into writhe and was confined in the corona. After calculating the
twist of the flux rope, we find that it was comparable to thresholds
of the helical kink instability found in numerical simulations. We
conclude that the activation and rise of the flux rope were triggered
and initially driven by the kink instability. The decay index of
the external magnetic field stays below the threshold for the torus
instability within a long height range. The confinement of the eruption
could be explained by the failure of the torus instability. Hard X-ray
sources at the peak of the M1.1 flare coincided with the footpoints
of the erupting helical structure, which indicates a high possibility
that hard X-ray sources were produced more efficiently in the flux rope.

---------------------------------------------------------
Title: Study of solar flares and filament interaction in NOAA 10501
on 20 November, 2003
Authors: Chandra, R.; Schmieder, B.; Mandrini, C. H.; Démoulin, P.;
Pariat, E.; Török, T.; Aulanier, G.; Uddin, W.; Linton, M. G.
2011ASInC...2..323C Altcode:
We analyze the observations of two flares from NOAA AR 10501 on 20
November, 2003. The flares are homologous, exhibit four ribbons and
are located in a quadrupolar magnetic configuration. The evolution
of the ribbons suggests that the first eruption is triggered by
"tether cutting" (with subsequent quadrupolar reconnection as in the
"magnetic breakout" model), whereas the second one is consistent
with the "magnetic breakout" model. Another interesting feature of
our observations is the interaction of two filaments elongated in the
north-south direction. The filaments merge at their central parts and
afterwards change their orientation to the east-west direction. This
merging and splitting is closely related to the evolution found in an
MHD simulation as a result of reconnection between two flux ropes.

---------------------------------------------------------
Title: Three-dimensional morphology of a coronal prominence cavity
Authors: Gibson, S. E.; Kucera, T. A.; Rastawicki, D.; Dove, J.; de
Toma, G.; Hao, J.; Hill, S. M.; Hudson, H. S.; Marque, C.; McIntosh,
P. S.; Rachmeler, L.; Reeves, K. K.; Schmieder, B.; Schmit, D. J.;
Sterling, A.; Tripathi, D.; Williams, D. R.; Zhang, M.
2010AGUFMSH51A1667G Altcode:
We present a three-dimensional density model of coronal prominence
cavities, and a morphological fit that has been tightly constrained
by a uniquely well-observed cavity. Observations were obtained as part
of an International Heliophysical Year campaign by instruments from a
variety of space- and ground-based observatories, spanning wavelengths
from radio to soft-X-ray to integrated white light. From these data
it is clear that the prominence cavity is the limb manifestation of
a longitudinally-extended polar-crown filament channel, and that
the cavity is a region of low density relative to the surrounding
corona. As a first step towards quantifying density and temperature
from campaign spectroscopic data, we establish the three-dimensional
morphology of the cavity. This is critical for taking line-of-sight
projection effects into account, since cavities are not localized in the
plane of the sky and the corona is optically thin. We have augmented
a global coronal streamer model to include a tunnel-like cavity with
elliptical cross-section and a Gaussian variation of height along
the tunnel length. We have developed a semi-automated routine that
fits ellipses to cross-sections of the cavity as it rotates past the
solar limb, and have applied it to Extreme Ultraviolet Imager (EUVI)
observations from the two Solar Terrestrial Relations Observatory
(STEREO) spacecraft. This defines the morphological parameters of our
model, from which we reproduce forward-modeled cavity observables. We
find that cavity morphology and orientation, in combination with the
viewpoints of the observing spacecraft, explains the observed variation
in cavity visibility for the east vs. west limbs.

---------------------------------------------------------
Title: Three-dimensional Morphology of a Coronal Prominence Cavity
Authors: Gibson, S. E.; Kucera, T. A.; Rastawicki, D.; Dove, J.; de
Toma, G.; Hao, J.; Hill, S.; Hudson, H. S.; Marqué, C.; McIntosh,
P. S.; Rachmeler, L.; Reeves, K. K.; Schmieder, B.; Schmit, D. J.;
Seaton, D. B.; Sterling, A. C.; Tripathi, D.; Williams, D. R.;
Zhang, M.
2010ApJ...724.1133G Altcode:
We present a three-dimensional density model of coronal prominence
cavities, and a morphological fit that has been tightly constrained
by a uniquely well-observed cavity. Observations were obtained as part
of an International Heliophysical Year campaign by instruments from a
variety of space- and ground-based observatories, spanning wavelengths
from radio to soft X-ray to integrated white light. From these data
it is clear that the prominence cavity is the limb manifestation of
a longitudinally extended polar-crown filament channel, and that the
cavity is a region of low density relative to the surrounding corona. As
a first step toward quantifying density and temperature from campaign
spectroscopic data, we establish the three-dimensional morphology
of the cavity. This is critical for taking line-of-sight projection
effects into account, since cavities are not localized in the plane of
the sky and the corona is optically thin. We have augmented a global
coronal streamer model to include a tunnel-like cavity with elliptical
cross-section and a Gaussian variation of height along the tunnel
length. We have developed a semi-automated routine that fits ellipses
to cross-sections of the cavity as it rotates past the solar limb, and
have applied it to Extreme Ultraviolet Imager observations from the
two Solar Terrestrial Relations Observatory spacecraft. This defines
the morphological parameters of our model, from which we reproduce
forward-modeled cavity observables. We find that cavity morphology
and orientation, in combination with the viewpoints of the observing
spacecraft, explain the observed variation in cavity visibility for
the east versus west limbs.

---------------------------------------------------------
Title: Driving Mechanism and Onset Condition of a Confined Eruption
Authors: Guo, Y.; Ding, M. D.; Schmieder, B.; Li, H.; Török, T.;
Wiegelmann, T.
2010ApJ...725L..38G Altcode:
We study a confined eruption accompanied by an M1.1 flare in solar
active region (AR) NOAA 10767 on 2005 May 27, where a pre-eruptive
magnetic flux rope was reported in a nonlinear force-free field (NLFFF)
extrapolation. The observations show a strong writhing motion of the
erupting structure, suggesting that a flux rope was indeed present
and converted some of its twist into writhe in the course of the
eruption. Using the NLFFF extrapolation, we calculate the twist of
the pre-eruptive flux rope and find that it is in very good agreement
with thresholds of the helical kink instability found in numerical
simulations. We conclude that the activation and rise of the flux
rope were triggered and driven by the instability. Using a potential
field extrapolation, we also estimate the height distribution of the
decay index of the external magnetic field in the AR 1 hr prior to the
eruption. We find that the decay index stays below the threshold for
the torus instability for a significant height range above the erupting
flux rope. This provides a possible explanation for the confinement
of the eruption to the low corona.

---------------------------------------------------------
Title: Flare Energy Build-Up in a Decaying Active Region Near a
Coronal Hole
Authors: Su, Yingna; van Ballegooijen, Adriaan; Schmieder, Brigitte;
Berlicki, Arkadiusz; Guo, Yang; Golub, Leon; Huang, Guangli
2010shin.confE.131S Altcode:
A B1.7 two-ribbon flare occurred in a highly non-potential decaying
active region near a coronal hole at 10:00 UT on May 17, 2008. This
flare is large in the sense that it involves the entire region, and
it is associated with both a filament eruption and a CME. We present
multi-wavelength observations from EUV (TRACE, STEREO/EUVI), X-rays
(Hinode/XRT), and H-alpha (THEMIS, BBSO) prior to, during and after
the flare. Prior to the flare, the region contained two filaments. The
long J-shaped sheared loops corresponding to the southern filament
were evolved from two short loop systems, which happened around 22:00
UT after a filament eruption on May 16. Formation of highly sheared
loops in the south eastern part of the region was observed by STEREO
8 hours before the flare. We also perform non-linear force free field
(NLFFF) modeling for the region at two times prior to the flare, using
the flux rope insertion method. The models include the non-force-free
effect of magnetic buoyancy in the photosphere. The best-fit NLFFF
models show good fit to observations both in the corona (X-ray and EUV
loops) and chromosphere (H-alpha filament). We find that the horizontal
fields in the photosphere are relatively insensitive to the present of
flux ropes in the corona. The axial flux of the flux rope in the NLFFF
model on May 17 is twice that on May 16, and the model on May 17 is only
marginally stable. We also find that the quasi-circular flare ribbons
are associated with the separatrix between open and closed fields. This
observation and NLFFF modeling suggest that this flare may be triggered
by the reconnection at the null point on the separatrix surface.

---------------------------------------------------------
Title: Statistical comparison of the observed and synthetic hydrogen
Lyman line profiles in solar prominences
Authors: Gunár, S.; Schwartz, P.; Schmieder, B.; Heinzel, P.;
Anzer, U.
2010A&A...514A..43G Altcode:
 Aims: We analyse a unique set of prominence SOHO/SUMER
Lyman spectra by comparing it with synthetic spectra obtained by 2D
multi-thread prominence fine-structure models. Methods: We
employed a novel statistical approach to the analysis of the observed
and synthetic Lyman spectra. We compared the statistical distributions
of the line properties of the observed and synthetic Lyman spectra using
a set of four statistical criteria. Results: We demonstrate
the very good agreement between the observed Lyman spectra and
synthetic spectra obtained by modelling. Conclusions: Our set
of statistical criteria is well-suited to analyses of the prominence
Lyman spectra because of its sensitivity to a number of different
parameters governing the conditions in the prominence fine structures.

---------------------------------------------------------
Title: Velocity vectors of a quiescent prominence observed by
Hinode/SOT and the MSDP (Meudon)
Authors: Schmieder, B.; Chandra, R.; Berlicki, A.; Mein, P.
2010A&A...514A..68S Altcode: 2009arXiv0911.5091S
Context. The dynamics of prominence fine structures present a
challenge to our understanding of the formation of cool plasma
prominence embedded in the hot corona. Aims: Observations
performed by the high resolution Hinode/SOT telescope allow us to
compute velocities perpendicular to the line-of-sight or transverse
velocities. Combining simultaneous observations obtained in Hα with
Hinode/SOT and the MSDP spectrograph operating in the Meudon solar
tower, we derive the velocity vectors of a quiescent prominence. Methods: The velocities perpendicular to the line-of-sight are
measured using a time-slice technique and the Doppler shifts velocity
using the bisector method. Results: The Doppler shifts of
bright threads derived from the MSDP show counterstreaming of the
order of 5 km s-1 in the prominence and reaching 15 km
s-1 at the edges of the prominence. Even though they are
minimum values because of seeing effects, they are of the same order
as the transverse velocities. Conclusions: These measurements
are very important because they suggest that the vertical structures
detected by SOT may not be true vertical magnetic structures in the sky
plane. The vertical structures could be a pile up of dips in more or
less horizontal magnetic field lines in a 3D perspective, as proposed
by many MHD modelers. In our analysis, we also calibrate the Hinode
Hα data using MSDP observations obtained simultaneously. A movie
is available in electronic form at http://www.aanda.org

---------------------------------------------------------
Title: Coexisting Flux Rope and Dipped Arcade Sections Along One
Solar Filament
Authors: Guo, Y.; Schmieder, B.; Démoulin, P.; Wiegelmann, T.;
Aulanier, G.; Török, T.; Bommier, V.
2010ApJ...714..343G Altcode:
We compute the three-dimensional magnetic field of an active
region in order to study the magnetic configuration of active region
filaments. The nonlinear force-free field model is adopted to compute
the magnetic field above the photosphere, where the vector magnetic
field was observed by THEMIS/MTR on 2005 May 27. We propose a new
method to remove the 180° ambiguity of the transverse field. Next, we
analyze the implications of the preprocessing of the data by minimizing
the total force and torque in the observed vector fields. This step
provides a consistent bottom boundary condition for the nonlinear
force-free field model. Then, using the optimization method to compute
the coronal field, we find a magnetic flux rope along the polarity
inversion line. The magnetic flux rope aligns well with part of an Hα
filament, while the total distribution of the magnetic dips coincides
with the whole Hα filament. This implies that the magnetic field
structure in one section of the filament is a flux rope, while the
other is a sheared arcade. The arcade induced a left-bearing filament
in the magnetic field of negative helicity, which is opposite to the
chirality of barbs that a flux rope would induce in a magnetic field
of the same helicity sign. The field strength in the center of the flux
rope is about 700 G, and the twist of the field lines is ~1.4 turns.

---------------------------------------------------------
Title: Physics of Solar Prominences: I—Spectral Diagnostics and
Non-LTE Modelling
Authors: Labrosse, N.; Heinzel, P.; Vial, J. -C.; Kucera, T.; Parenti,
S.; Gunár, S.; Schmieder, B.; Kilper, G.
2010SSRv..151..243L Altcode: 2010SSRv..tmp...34L; 2010arXiv1001.1620L
This review paper outlines background information and covers recent
advances made via the analysis of spectra and images of prominence
plasma and the increased sophistication of non-LTE ( i.e. when there is
a departure from Local Thermodynamic Equilibrium) radiative transfer
models. We first describe the spectral inversion techniques that have
been used to infer the plasma parameters important for the general
properties of the prominence plasma in both its cool core and the
hotter prominence-corona transition region. We also review studies
devoted to the observation of bulk motions of the prominence plasma and
to the determination of prominence mass. However, a simple inversion
of spectroscopic data usually fails when the lines become optically
thick at certain wavelengths. Therefore, complex non-LTE models become
necessary. We thus present the basics of non-LTE radiative transfer
theory and the associated multi-level radiative transfer problems. The
main results of one- and two-dimensional models of the prominences and
their fine-structures are presented. We then discuss the energy balance
in various prominence models. Finally, we outline the outstanding
observational and theoretical questions, and the directions for future
progress in our understanding of solar prominences.

---------------------------------------------------------
Title: A Technique for Removing Background Features in SECCHI -
EUVI He II 304 Å Filtergrams: Application to the Filament Eruption
of 22 May 2008
Authors: Artzner, G.; Gosain, S.; Schmieder, B.
2010SoPh..262..437A Altcode: 2010SoPh..tmp...41A; 2010SoPh..tmp...53A; 2010arXiv1001.4884A
The STEREO mission has been providing a stereoscopic view of filament
eruptions in the EUV. The clearest view during a filament eruption
is seen in He II 304 Å observations. One of the main problems in
visualizing filament dynamics in He II 304 Å is the strong background
contrast due to surface features. We present a technique that removes
background features and leaves behind only the filamentary structure, as
seen by STEREO-A and -B. The technique uses a pair of STEREO He II 304
Å images observed simultaneously. The STEREO-B image is geometrically
transformed to a STEREO-A view so that the background images appear
similar. Filaments, being elevated structures, i.e., not lying on the
same spherical surface as background features, do not appear similar
in the transformed view. Thus, subtracting the two images cancels
the background but leaves behind the filament structure. We apply this
technique to study the dynamics of the filament-eruption event of 22 May
2008, which was observed by STEREO and followed by several ground-based
observatories participating in the Joint Observing Programme (JOP 178).

---------------------------------------------------------
Title: Physics of Solar Prominences: II—Magnetic Structure and
Dynamics
Authors: Mackay, D. H.; Karpen, J. T.; Ballester, J. L.; Schmieder,
B.; Aulanier, G.
2010SSRv..151..333M Altcode: 2010SSRv..tmp...32M; 2010arXiv1001.1635M
Observations and models of solar prominences are reviewed. We focus on
non-eruptive prominences, and describe recent progress in four areas of
prominence research: (1) magnetic structure deduced from observations
and models, (2) the dynamics of prominence plasmas (formation and
flows), (3) Magneto-hydrodynamic (MHD) waves in prominences and (4)
the formation and large-scale patterns of the filament channels in
which prominences are located. Finally, several outstanding issues in
prominence research are discussed, along with observations and models
required to resolve them.

---------------------------------------------------------
Title: Magnetic Field Structures in a Facular Region Observed by
THEMIS and Hinode
Authors: Guo, Y.; Schmieder, B.; Bommier, V.; Gosain, S.
2010SoPh..262...35G Altcode: 2010SoPh..tmp...30G; 2010arXiv1002.4355G
The main objective of this paper is to build and compare vector
magnetic maps obtained by two spectral polarimeters, i.e. THEMIS/MTR and
Hinode SOT/SP, using two inversion codes (UNNOFIT and MELANIE) based
on the Milne - Eddington solar atmosphere model. To this end, we used
observations of a facular region within active region NOAA 10996 on 23
May 2008, and found consistent results concerning the field strength,
azimuth and inclination distributions. Because SOT/SP is free from the
seeing effect and has better spatial resolution, we were able to resolve
small magnetic polarities with sizes of 1″ to 2″, and we could
detect strong horizontal magnetic fields, which converge or diverge
in negative or positive facular polarities. These findings support
models which suggest the existence of small vertical flux tube bundles
in faculae. A new method is proposed to get the relative formation
heights of the multi-lines observed by MTR assuming the validity of
a flux tube model for the faculae. We found that the Fe I 6302.5 Å
line forms at a greater atmospheric height than the Fe I 5250.2 Å line.

---------------------------------------------------------
Title: How do unresolved motions affect the prominence hydrogen
Lyman spectrum.
Authors: Gunar, Stanislav; Schwartz, Pavol; Schmieder, Brigitte;
Heinzel, Petr; Anzer, Ulrich
2010cosp...38.2830G Altcode: 2010cosp.meet.2830G
Space-born observations of quiescent prominences in the hydrogen
Lyman line series provide a considerable amount of information
about their structure and physical properties. Lyman line series
thus represents a focus of several detailed studies. However, the
substantial asymmetries exhibited by considerable number of observed
Lyman line profiles present a strong indication for the existence of
hidden fine-structure dynamics. If attributed merely to the Doppler
shift effect, these asymmetries would correspond to radial velocities
of the order of 100 km/s. Such high velocities, however, were never
observed in quiescent prominences. Typical fine-structure velocities are
of the order of 10 km/s. To tackle this problem, we have modified our
2D multi-thread prominence models and randomly assigned line-of-sight
(LOS) velocities of the order of 10 km/s to each thread. The obtained
synthetic Lyman spectrum exhibits substantial asymme-tries of the line
profiles comparable with SOHO/SUMER observations. Moreover, our results
do indicate that the synthetic Lyman-α profiles may exhibit an opposite
asymmetry to that of the higher Lyman lines. This is consistent with
observations which often show opposite asym-metries of these lines at
the same prominence location. We have demonstrated the agreement of
synthetic and observed spectra not only by comparing asymmetries of
individual profiles but also by exploiting statistically significant
sets of the observed and synthetic data. These results represent an
important step in our understanding of hidden fine-structure dynamics
of quiescent prominences.

---------------------------------------------------------
Title: Counterstreaming in quiescent prominences observed by
Hinode/SOT and Meudon/MSDP
Authors: Schmieder, Brigitte; Chandra, Ramesh; Berlicki, Arkadiusz;
Mein, Pierre
2010cosp...38.2943S Altcode: 2010cosp.meet.2943S
Prominences have been successfully observed by Hinode in April 2007
exhibiting a strong dy-namics of their fine structures. The dynamics
of a prominence is a challenge to understand the formation of cool
prominence plasma embedded in the hot corona. Combining simultaneous
observations obtained in Hα with Hinode/SOT and the MSDP spectrograph
operating at the Meudon solar tower, velocity vectors have been
derived. The Doppler-shifts of bright threads are of the same order
as the transverse velocities measured perpendicularly to the line of
sight. Counterstreamings are detected at the top of the prominence. The
vertical structures of the prominence could be a pile up of dips in
magnetic field lines viewed in 3D

---------------------------------------------------------
Title: How Can a Negative Magnetic Helicity Active Region Generate
a Positive Helicity Magnetic Cloud?
Authors: Chandra, R.; Pariat, E.; Schmieder, B.; Mandrini, C. H.;
Uddin, W.
2010SoPh..261..127C Altcode: 2009arXiv0910.0968C
The geoeffective magnetic cloud (MC) of 20 November 2003 was associated
with the 18 November 2003 solar active events in previous studies. In
some of these, it was estimated that the magnetic helicity carried by
the MC had a positive sign, as did its solar source, active region (AR)
NOAA 10501. In this article we show that the large-scale magnetic field
of AR 10501 has a negative helicity sign. Since coronal mass ejections
(CMEs) are one of the means by which the Sun ejects magnetic helicity
excess into interplanetary space, the signs of magnetic helicity in
the AR and MC must agree. Therefore, this finding contradicts what is
expected from magnetic helicity conservation. However, using, for the
first time, correct helicity density maps to determine the spatial
distribution of magnetic helicity injections, we show the existence
of a localized flux of positive helicity in the southern part of AR
10501. We conclude that positive helicity was ejected from this portion
of the AR leading to the observed positive helicity MC.

---------------------------------------------------------
Title: Estimation of width and inclination of a filament sheet using
He II 304 Å observations by STEREO/EUVI
Authors: Gosain, S.; Schmieder, B.
2010AnGeo..28..149G Altcode: 2010arXiv1001.3004G
The STEREO mission has been providing stereoscopic view of the
filament eruptions in EUV wavelengths. The most extended view during
filament eruptions is seen in He II 304 Å observations, as the
filament spine appears darker and sharper. The projected filament
width appears differently when viewed from different angles by STEREO
satellites. Here, we present a method for estimating the width and
inclination of the filament sheet using He II 304 Å observations
by STEREO-A and B satellites from the two viewpoints. The width of
the filament sheet, when measured from its feet to its apex, gives
estimate of filament height above the chromosphere.

---------------------------------------------------------
Title: A Flaring Twisted Emerging Flux Region
Authors: Chandra, R.; Schmieder, B.; Aulanier, G.; Malherbe, J. M.
2010ASSP...19..523C Altcode: 2010mcia.conf..523C
We present signatures of the emergence of a twisted flux tube in
decaying active region NOAA AR10365 on 27 May 2003. When the magnetic
flux tube is twisted, an asymmetry appears in the magnetogram because
of the contribution of the azimuthal component to the observed vertical
component of the field. In this case, the vertical component produces
two "tongues" (Fig. 1, left). The twist of the flux tube is revealed
by the photospheric longitudinalmagnetic field pattern: diverging
flows of opposite polarities, elongated polarities with a "tongue"
shape. The asymmetry of the opposite polarities is interpreted as
right-hand twist of the emerging flux tube.

---------------------------------------------------------
Title: Vector Magnetic Field in Emerging Flux Regions
Authors: Schmieder, B.; Pariat, E.
2010ASSP...19..505S Altcode: 2010mcia.conf..505S
A crucial phase in magnetic flux emergence is the rise of magnetic
flux tubes through the solar photosphere, which represents a severe
transition between the very different environments of the solar interior
and corona. Multi-wavelength observations with Flare Genesis, TRACE,
SoHO, and more recently with the vector magnetographs at THEMIS and Hida
(DST) led to the following conclusions. The fragmented magnetic field
in the emergence region - with dipped field lines or bald patches -
is directly related with Ellerman bombs, arch filament systems, and
overlying coronal loops. Measurements of vector magnetic fields have
given evidence that undulating "serpentine" fields are present while
magnetic flux tubes cross the photosphere. See the sketch below, and
for more detail see Pariat et al. (2004, 2007); Watanabe et al. (2008):

---------------------------------------------------------
Title:

---------------------------------------------------------
Title: Can purely emissive Ly_beta prominence spectra be
caused by the line of sight oriented parallelly to the magnetic field?
Authors: Schwartz, Pavol; Gunar, Stanislav; Heinzel, Petr; Schmieder,
Brigitte
2010cosp...38.2852S Altcode: 2010cosp.meet.2852S
Small bright prominence was observed on the SW limb on April 26,
2007 between 13:01 and 23:50 UT by SUMER spectrograph on-board SoHO
in hydrogen Lyman line series except the Lyα line. Profiles of the
Lyβ line are peculiar for a prominence because they do not exhibit any
central reversals (dips in cores of the lines). This could be explained
by the fact that the line of sight is parallel with the direction of
the magnetic field in the prominence. We can investigate this fact
by a statistical comparison of observed profiles with the synthetic
ones computed using the 2D multi-thread model of the prominence. We
use synthetic profiles obtained for various orientations of the
line of sight with respect to the magnetic field, ranging from
perpendicular to parallel. Profiles are compared statistically using
their characteristics such as integral intensities, so-called Lyman
decrement (ratio of integral intensity of the line to integral intensity
of the Lyβ line, etc.).

---------------------------------------------------------
Title: Ejective events from a complex active region
Authors: Mandrini, Cristina H.; Chandra, Ramesh; Pariat, Etienne;
Schmieder, Brigitte; Demoulin, Pascal; Toeroek, Tibor; Uddin, Wahab
2010cosp...38.1886M Altcode: 2010cosp.meet.1886M
On 18 and 20 November 2003 active region (AR) 10501 produced a series of
M flares all of them associated with coronal mass ejections (CMEs). The
particularity of this AR is that while observational tracers of the
magnetic helicity sign indicate that the large scale field in the
region had a negative magnetic helicity sign, the MC associated
to the most intense flare/CME on November 18 showed the opposite
sign. Furthermore, the filaments observed on November 20 present
morphological characteristics that correspond to a negative magnetic
helicity sign, the rotation of the polarities of an emerging bipole
indicate negative magnetic helicity sign injection; however, the flare
ribbons observed after two homologous events can be connected either
by field lines computed using a positive or a negative helicity sign
magnetic field. We combine Hα, EUV, hard X-rays, and magnetic field
data analysis with magnetic field modelling, and magnetic helicity
injection computations to understand the origin of the helicity
sign discrepancies discussed above. On November 20 magnetic field
modeling and topology computations (in particular, the location of
quasi-separatrix layers in relation to flare ribbons and evolution)
give us clues about the CME initiation process.

---------------------------------------------------------
Title: Relations between theoretical and observational plasma
parameters and the radiation of the prominence
Authors: Berlicki, Arkadiusz; Schwartz, Pavol; Schmieder, Brigitte;
Heinzel, Petr; Gunar, Stanislav
2010cosp...38.2945B Altcode: 2010cosp.meet.2945B
On April 26, 2007 the quiescent prominence was observed during the
coordinated campaign of prominence studies icluding SOT, XRT, and
EIS on Hinode, MDI, EIT, SUMER, and CDS on SOHO, TRACE, and several
ground-based observatories. This was the first Hinode-SUMER ob-serving
campaign. In this analysis we use the data obtained with Hinode/SOT,
SOHO/SUMER and Multichannel Spectrograph MSDP (Meudon, France). The
SUMER instrument provide us the UV spectra of the prominence in several
spectral lines along the 120 arcsec slit crossing the prominence. We
used the following lines: Lβ, Lγ, Lδ, L , C III and S VI. Using
these spectra we calculated the integrated intensities along the slit
for all these lines. We also calculated the integrated intensity of
the Hα line from the spectroscopic ground-based MSDP observations
for the same parts of the prominence observed at the same time. These
intensities were used to calibrate the Hinode/SOT data. Next, we
analyzed the relations between different observed intensities in these
lines and compared them with the values obtained from the theoretical
simulations. We analyzed the correlations between observations and
theoretical modeling and as a results we estimated the different
physical parameters of the prominence plasma.

---------------------------------------------------------
Title: A 3D view of eruptive filaments by STEREO
Authors: Gosain, Sanjay; Schmieder, Brigitte; Venkatakrishnan, P.;
Chandra, Ramesh; Artzner, Guy
2010cosp...38.2916G Altcode: 2010cosp.meet.2916G
STEREO/SECHI/EUVI A and B observe different views of the eruption of a
quiescent filament. We will concentrate on two events: (i) May 20 to 22,
2008 event (A and B separated by 52.4 degrees from each other), and (ii)
September 25 to 26, 2009 event (A and B more than 100 degrees from each
other. After using different techniques of reconstruction we obtained
a 3 dimensional view of untwisted flux ropes in He II 304 Angstrom,
with fine structures. The entire disappearance phase lasted more than
ten hours. The filament evolved very slowly ( 5 km/s) from a dense
structure with a thick spine into fine threads. Individual threads are
seen to be oscillating and rising to an altitude of about 150 Mm with
velocities of about 100 km/s. The plasma disappears by diffusion in
the corona. Weak CME events are recorded by LASCO at the beginning of
the disappearance. In this paper we shall present the dynamics of the
filament eruptions as viewed in 3D by STEREO using different methods. We
shall explore the causes and consequences of the filament disappearance.

---------------------------------------------------------
Title: Actors of the main activity of large complex centres during
the 23 Solar Cycle maximum
Authors: Schmieder, Brigitte; Chandra, Ramesh; Demoulin, Pascal;
Mandrini, Cristina H.; Venkatakrishnan, P.; Manoharan, P. K.; Uddin,
Wahab; Pariat, Etienne; Toeroek, Tibor; Molodij, Guillaume; Kumar, P.
2010cosp...38.1861S Altcode: 2010cosp.meet.1861S
During the maximum of the last Solar Cycle solar cycle 23, large
active regions had a long life spanning several solar rotations and
produced a large number of X-ray class flares, CMEs and Magnetic
clouds (MC). This was the case for the Halloween active regions in
2003. The most geoeffective magnetic cloud of the cycle (Dst=-457)
has its source in one passage of the active region (NOAA 10501) on
November 18, 2003. Such an activity is presumably due to continuous
emerging magnetic flux that was observed during this passage. Moreover,
the region exhibited a complex topology with multiple domains of
distinct magnetic helicities. The complexity is observed to reach
such unprecedented levels that a detailed multi wavelength analysis
is necessary to precisely identify the sources of CMEs and MCs.

---------------------------------------------------------
Title: Hinode/SOT Measurements of Flows and Waves in Solar Prominences
Authors: Berger, Thomas; Okamoto, Takenori; Schmieder, Brigitte
2010cosp...38.2913B Altcode: 2010cosp.meet.2913B
We review Hinode Solar Optical Telescope (SOT) measurements of flows
and waves in quies-cent and active solar prominences. In quiescent
prominences, Hinode/SOT observations have revealed a new mode of
buoyant transport in the form of dark upflows that originate at
the chromospheric base of the prominence. The upflows can take the
form of large-scale (10 Mm) "bubbles" that rise through the entire
prominence into the overlying coronal cavity, or they can take the form
of numerous small-scale (1 Mm) plumes that generate from an apparent
Rayleigh-Taylor instability on the boundary between the prominence and
the impinging buoy-ant flow system. The episodic flows directly inject
mass, magnetic flux, and helicity into the overlying coronal cavity,
moving the system towards destabilization and eruption in the form of
CMEs. Hinode/SOT quiescent prominence observations have also verified
the existence of ubiquitous downflow streams and vortex flows confirming
that prominences are far from magne-tostatic conditions. Tracking and
doppler measurements of prominence downflows find speeds of 5-15 km s-1
and imply that the trajectories are not strictly vertical. Active region
promi-nence studies find counter-streaming flows along horizontal
magnetic field lines with velocities of 20-30 km s-1 ; upflows,
downflow streams, and rotational flows have not been observed in
these systems. Active Region prominence field lines exhibit transverse
oscillations indicative of Alfv`n waves with periods of several minutes,
amplitudes of 1 Mm, and wavelengths of 250 Mm or more. These properties
are consistent with magnetic field strengths of 50 gauss or more at
typical prominence density conditions and carry enough energy to heat
the surrounding prominence/corona transition region (PCTR).

---------------------------------------------------------
Title: Flare Energy Build-up in a Decaying Active Region Near a
Coronal Hole
Authors: Su, Yingna; van Ballegooijen, Adriaan; Schmieder, Brigitte;
Berlicki, Arkadiusz; Guo, Yang; Golub, Leon; Huang, Guangli
2009ApJ...704..341S Altcode:
A B1.7 two-ribbon flare occurred in a highly non-potential decaying
active region near a coronal hole at 10:00 UT on 2008 May 17. This
flare is "large" in the sense that it involves the entire region,
and it is associated with both a filament eruption and a coronal mass
ejection. We present multi-wavelength observations from EUV (TRACE,
STEREO/EUVI), X-rays (Hinode/XRT), and Hα (THEMIS, BBSO) prior to,
during and after the flare. Prior to the flare, the region contained
two filaments. The long J-shaped sheared loops corresponding to the
southern filament were evolved from two short loop systems, which
happened around 22:00 UT after a filament eruption on May 16. Formation
of highly sheared loops in the southeastern part of the region was
observed by STEREO 8 hr before the flare. We also perform nonlinear
force-free field (NLFFF) modeling for the region at two times prior
to the flare, using the flux rope insertion method. The models include
the non-force-free effect of magnetic buoyancy in the photosphere. The
best-fit NLFFF models show good fit to observations both in the corona
(X-ray and EUV loops) and chromosphere (Hα filament). We find that
the horizontal fields in the photosphere are relatively insensitive
to the present of flux ropes in the corona. The axial flux of the
flux rope in the NLFFF model on May 17 is twice that on May 16,
and the model on May 17 is only marginally stable. We also find that
the quasi-circular flare ribbons are associated with the separatrix
between open and closed fields. This observation and NLFFF modeling
suggest that this flare may be triggered by the reconnection at the
null point on the separatrix surface.

---------------------------------------------------------
Title: 3D Evolution of a Filament Disappearance Event Observed
by STEREO
Authors: Gosain, S.; Schmieder, B.; Venkatakrishnan, P.; Chandra,
R.; Artzner, G.
2009SoPh..259...13G Altcode: 2009arXiv0910.0786G
A filament disappearance event was observed on 22 May 2008 during
our recent campaign JOP 178. The filament, situated in the Southern
Hemisphere, showed sinistral chirality consistent with the hemispheric
rule. The event was well observed by several observatories,
in particular by THEMIS. One day, before the disappearance, Hα
observations showed up- and down-flows in adjacent locations along the
filament, which suggest plasma motions along twisted flux rope. THEMIS
and GONG observations show shearing photospheric motions leading
to magnetic flux canceling around barbs. STEREO A, B spacecraft
with separation angle 52.4°, showed quite different views of this
untwisting flux rope in He II 304 Å images. Here, we reconstruct the
three-dimensional geometry of the filament during its eruption phase
using STEREO EUV He II 304 Å images and find that the filament was
highly inclined to the solar normal. The He II 304 Å movies show
individual threads, which oscillate and rise to an altitude of about
120 Mm with apparent velocities of about 100 km s−1
during the rapid evolution phase. Finally, as the flux rope expands
into the corona, the filament disappears by becoming optically thin to
undetectable levels. No CME was detected by STEREO, only a faint CME
was recorded by LASCO at the beginning of the disappearance phase at
02:00 UT, which could be due to partial filament eruption. Further,
STEREO Fe XII 195 Å images showed bright loops beneath the filament
prior to the disappearance phase, suggesting magnetic reconnection
below the flux rope.

---------------------------------------------------------
Title: Fan-Spine Topology Formation Through Two-Step Reconnection
Driven by Twisted Flux Emergence
Authors: Török, T.; Aulanier, G.; Schmieder, B.; Reeves, K. K.;
Golub, L.
2009ApJ...704..485T Altcode: 2009arXiv0909.2235T
We address the formation of three-dimensional nullpoint topologies
in the solar corona by combining Hinode/X-ray Telescope (XRT)
observations of a small dynamic limb event, which occurred beside
a non-erupting prominence cavity, with a three-dimensional (3D)
zero-β magnetohydrodynamics (MHD) simulation. To this end, we model
the boundary-driven "kinematic" emergence of a compact, intense,
and uniformly twisted flux tube into a potential field arcade that
overlies a weakly twisted coronal flux rope. The expansion of the
emerging flux in the corona gives rise to the formation of a nullpoint
at the interface of the emerging and the pre-existing fields. We unveil
a two-step reconnection process at the nullpoint that eventually yields
the formation of a broad 3D fan-spine configuration above the emerging
bipole. The first reconnection involves emerging fields and a set of
large-scale arcade field lines. It results in the launch of a torsional
MHD wave that propagates along the arcades, and in the formation of
a sheared loop system on one side of the emerging flux. The second
reconnection occurs between these newly formed loops and remote arcade
fields, and yields the formation of a second loop system on the opposite
side of the emerging flux. The two loop systems collectively display
an anenome pattern that is located below the fan surface. The flux that
surrounds the inner spine field line of the nullpoint retains a fraction
of the emerged twist, while the remaining twist is evacuated along
the reconnected arcades. The nature and timing of the features which
occur in the simulation do qualititatively reproduce those observed
by XRT in the particular event studied in this paper. Moreover, the
two-step reconnection process suggests a new consistent and generic
model for the formation of anemone regions in the solar corona.

---------------------------------------------------------
Title: Evidence of Magnetic Helicity in Emerging Flux and Associated
Flare
Authors: Chandra, R.; Schmieder, B.; Aulanier, G.; Malherbe, J. M.
2009SoPh..258...53C Altcode: 2009arXiv0906.1210C
The aim of this paper is to look at the magnetic helicity structure
of an emerging active region and show that both emergence and flaring
signatures are consistent with a same sign for magnetic helicity. We
present a multiwavelength analysis of an M1.6 flare occurring in the
NOAA active region 10365 on 27 May 2003, in which a large new bipole
emerges in a decaying active region. The diverging flow pattern and the
"tongue" shape of the magnetic field in the photosphere with elongated
polarities are highly suggestive of the emergence of a twisted flux
tube. The orientation of these tongues indicates the emergence of a flux
tube with a right-hand twist (i.e., positive magnetic helicity). The
flare signatures in the chromosphere are ribbons observed in Hα
by the MSDP spectrograph in the Meudon solar tower and in 1600 Å by
TRACE. These ribbons have a J shape and are shifted along the inversion
line. The pattern of these ribbons suggests that the flare was triggered
by magnetic reconnection at coronal heights below a twisted flux tube of
positive helicity, corresponding to that of the observed emergence. It
is the first time that such a consistency between the signatures of
the emerging flux through the photosphere and flare ribbons has been
clearly identified in observations. Another type of ribbons observed
during the flare at the periphery of the active region by the MSDP and
SOHO/EIT is related to the existence of a null point, which is found
high in the corona in a potential field extrapolation. We discuss
the interpretation of these secondary brightenings in terms of the
"breakout" model and in terms of plasma compression/heating within
large-scale separatrices.

---------------------------------------------------------
Title: Three frontside full halo coronal mass ejections with a
nontypical geomagnetic response
Authors: Rodriguez, L.; Zhukov, A. N.; Cid, C.; Cerrato, Y.; Saiz,
E.; Cremades, H.; Dasso, S.; Menvielle, M.; Aran, A.; Mandrini, C.;
Poedts, S.; Schmieder, B.
2009SpWea...7.6003R Altcode:
Forecasting potential geoeffectiveness of solar disturbances (in
particular, of frontside full halo coronal mass ejections) is important
for various practical purposes, e.g., for satellite operations, radio
communications, global positioning system applications, power grid,
and pipeline maintenance. We analyze three frontside full halo coronal
mass ejections (CMEs) that occurred in the year 2000 (close to the
activity maximum of solar cycle 23), together with associated solar
and heliospheric phenomena as well as their impact on the Earth's
magnetosphere. Even though all three were fast full halos (with plane
of the sky speeds higher than 1100 km/s), the geomagnetic response
was very different for each case. After analyzing the source regions
of these halo CMEs, it was found that the halo associated with the
strongest geomagnetic disturbance was the one that initiated farther
away from disk center (source region at W66); while the other two CMEs
originated closer to the central meridian but had weaker geomagnetic
responses. Therefore, these three events do not fit into the general
statistical trends that relate the location of the solar source and
the corresponding geoeffectivity. We investigate possible causes of
such a behavior. Nonradial direction of eruption, passage of the Earth
through a leg of an interplanetary flux rope, and strong compression
at the eastern flank of a propagating interplanetary CME during its
interaction with the ambient solar wind are found to be important
factors that have a direct influence on the resulting north-south
interplanetary magnetic field (IMF) component and thus on the CME
geoeffectiveness. We also find indications that interaction of two CMEs
could help in producing a long-lasting southward IMF component. Finally,
we are able to explain successfully the geomagnetic response using
plasma and magnetic field in situ measurements at the L1 point. We
discuss the implications of our results for operational space weather
forecasting and stress the difficulties of making accurate predictions
with the current knowledge and tools at hand.

---------------------------------------------------------
Title: Magnetic Nonpotentiality Accumulation Prior to a "Large"
B1.7 Two-Ribbon Flare
Authors: Su, Yingna; van Ballegooijen, A.; Schmieder, B.; Berlicki,
A.; Guo, Y.; Golub, L.
2009SPD....40.2002S Altcode:
A B1.7 two-ribbon flare occurred in a highly non-potential decaying
active region near a coronal hole at 10:00 UT on May 17, 2008. This
flare is "large" in the sense that it involves the entire region, and
it is associated with both a filament eruption and a CME. We present
multi-wavelength observations from EUV (TRACE, STEREO/EUVI), X-rays
(Hinode/XRT), and H-alpha (THEMIS, BBSO) prior to, during and after
the flare. Prior to the flare, the observed coronal loops are mainly
two sets of highly sheared loops surrounding two filaments. The sheared
loops in the southern part of the region appeared in TRACE around 22:00
UT after a filament ejection on May 16. We also performed non-linear
force free field (NLFFF) modeling for the region prior to the flare,
using the flux rope insertion method. The model at 11:42 UT on May 16 is
based on THEMIS (vector) and MDI magnetograms, and the model at 08:03 UT
on May 17 is based only on MDI magnetogram. The best-fit NLFFF models
show good fit to observations both in the corona (X-ray and EUV loops)
and chromosphere (H-alpha filament). In the photosphere, the vectors
in the best-fit NLFFF model are similar to those in the potential
model. However, in the chromosphere, the vectors in the best-fit NLFFF
model present strong non-potentiality, especially at the end of the
inserted flux rope. We also found that the axial flux of the flux rope
in the NLFFF model on May 17 is much higher than that on May 16.

---------------------------------------------------------
Title: Coronal loops, flare ribbons and aurora during slip-running
Authors: Schmieder, Brigitte; Aulanier, Guillaume; Démoulin, Pascal;
Pariat, Etienne
2009EP&S...61..565S Altcode: 2009EP&S...61L.565S
Solar two ribbon flares are commonly explained by magnetic field
reconnections in the low corona. During the reconnection energetic
particles (electrons and protons) are accelerated from the reconnection
site. These particles are following the magnetic field lines down
to the chromosphere. As the plasma density is higher in these lower
layers, there are collisions and emission of radiation. Thus bright
ribbons are observed at both ends of flare loops. These ribbons are
typically observed in Hα and in EUV with SoHO and TRACE. As the
time is going, these ribbons are expanding away of each other. In
most studied models, the reconnection site is a separator line,
where two magnetic separatrices intersect. They define four distinct
connectivity domains, across which the magnetic connectivity changes
discontinuously. In this paper, we present a generalization of this
model to 3D complex magnetic topologies where there are no null points,
but quasi-separatrices layers instead. In that case, while the ribbons
spread away during reconnection, we show that magnetic field lines
can quickly slip along them. We propose that this new phenomenon could
explain fast extension of Hα and TRACE 1600 Å ribbons, fast moving
HXR footpoints along the ribbons as observed by RHESSI, and that it
is observed in soft X rays with Hinode/XRT.

---------------------------------------------------------
Title: Evidence for a Pre-Eruptive Twisted Flux Rope Using the Themis
Vector Magnetograph
Authors: Canou, A.; Amari, T.; Bommier, V.; Schmieder, B.; Aulanier,
G.; Li, H.
2009ApJ...693L..27C Altcode:
Although there is evidence that twisted structures form during
large-scale eruptive events, it is not yet clear whether these exist in
the pre-eruptive phase as twisted flux ropes (TFRs) in equilibrium. This
question has become a major issue since several theoretical mechanisms
can lead to the formation of TFRs. These models consider either the
evolution of a coronal configuration driven by photospheric changes or
the emergence of TFR from the convection zone. We consider as a target
for addressing this issue the active region NOAA AR 10808 known at
the origin of several large-scale eruptive phenomena, and associated
with the emergence of a δ-spot. Using the THEMIS vector magnetogram
as photospheric boundary conditions for our nonlinear force-free
reconstruction model of the low corona and without any other assumption,
we show that the resulting pre-eruptive configuration exhibits a TFR
above the neutral line of the emerging δ-spot. In addition, the free
magnetic energy of this configuration could even be large enough to
explain such resulting large-scale eruptive events.

---------------------------------------------------------
Title: Solar prominences
Authors: Schmieder, Brigitte; Aulanier, Guillaume; Török, Tibor
2009IAUS..257..223S Altcode:
Solar filaments (or prominences) are magnetic structures in the
corona. They can be represented by twisted flux ropes in a bipolar
magnetic environment. In such models, the dipped field lines of the
flux rope carry the filament material and parasitic polarities in the
filament channel are responsible for the existence of the lateral feet
of prominences. Very simple laws do exist for the chirality of
filaments, the so-called “filament chirality rules”: commonly
dextral/sinistral filaments corresponding to left- (resp. right)
hand magnetic twists are in the North/South hemisphere. Combining
these rules with 3D weakly twisted flux tube models, the sign of the
magnetic helicity in several filaments were identified. These rules
were also applied to the 180° disambiguation of the direction of the
photospheric transverse magnetic field around filaments using THEMIS
vector magnetograph data (López Ariste et al. 2006). Consequently,
an unprecedented evidence of horizontal magnetic support in filament
feet has been observed, as predicted by former magnetostatic and
recent MHD models. The second part of this review concerns the
role of emerging flux in the vicinity of filament channels. It has been
suggested that magnetic reconnection between the emerging flux and the
pre-existing coronal field can trigger filament eruptions and CMEs. For
a particular event, observed with Hinode/XRT, we observe signatures of
such a reconnection, but no eruption of the filament. We present a 3D
numerical simulation of emerging flux in the vicinity of a flux rope
which was performed to reproduce this event and we briefly discuss,
based on the simulation results, why the filament did not erupt.

---------------------------------------------------------
Title: Linking two consecutive nonmerging magnetic clouds with their
solar sources
Authors: Dasso, S.; Mandrini, C. H.; Schmieder, B.; Cremades, H.; Cid,
C.; Cerrato, Y.; Saiz, E.; Démoulin, P.; Zhukov, A. N.; Rodriguez,
L.; Aran, A.; Menvielle, M.; Poedts, S.
2009JGRA..114.2109D Altcode: 2009JGRA..11402109D; 2012arXiv1212.5546D
On 15 May 2005, a huge interplanetary coronal mass ejection (ICME) was
observed near Earth. It triggered one of the most intense geomagnetic
storms of solar cycle 23 (Dst peak = -263 nT). This
structure has been associated with the two-ribbon flare, filament
eruption, and coronal mass ejection originating in active region 10759
(NOAA number). We analyze here the sequence of events, from solar wind
measurements (at 1 AU) and back to the Sun, to understand the origin
and evolution of this geoeffective ICME. From a detailed observational
study of in situ magnetic field observations and plasma parameters
in the interplanetary (IP) medium and the use of appropriate models
we propose an alternative interpretation of the IP observations,
different to those discussed in previous studies. In our view, the
IP structure is formed by two extremely close consecutive magnetic
clouds (MCs) that preserve their identity during their propagation
through the interplanetary medium. Consequently, we identify two
solar events in Hα and EUV which occurred in the source region
of the MCs. The timing between solar and IP events, as well as the
orientation of the MC axes and their associated solar arcades are in
good agreement. Additionally, interplanetary radio type II observations
allow the tracking of the multiple structures through inner heliosphere
and pin down the interaction region to be located midway between the
Sun and the Earth. The chain of observations from the photosphere to
interplanetary space is in agreement with this scenario. Our analysis
allows the detection of the solar sources of the transients and explains
the extremely fast changes of the solar wind due to the transport of
two attached (though nonmerging) MCs which affect the magnetosphere.

---------------------------------------------------------
Title: Magnetic helicity and solar prominence formation
Authors: Aulanier, G.; Schmieder, B.
2008sf2a.conf..543A Altcode:
Simple laws have long-since been put forward from the chirality of
observed features to derive the direction of the axial magnetic field
inside solar filaments. These are the so-called “filament chirality
rules”. Here, we report on two uses of these rules applied to THEMIS
and SVST observations and to MHD simulations. Being the first to
apply these rules to the 180° disambiguation of the direction of
the photospheric transverse magnetic field around filaments, we found
the unprecedented evidence of magnetic support in filament feet, as
predicted by former magnetostatic and recent MHD models. By combining
these rules with 3D weakly twisted flux tube models, we identified
the sign of the magnetic helicity in several filaments. Following
their interactions with one another over a few days, we found that the
observational condition for two filaments to merge is that their flux
tubes must have the same helicity sign. We theoretically recovered
these results, by conducting a parametric study of 3D numerical MHD
simulations of sheared bipoles. This study also provided new conditions
for filament merging, in yet-unobserved configurations in which sheared
bipoles are oppositely oriented.

---------------------------------------------------------
Title: Photospheric flows around a quiescent filament at Large and
small scale and their ffects on filament destabilization
Authors: Roudier, Th.; Malherbe, J. M.; Švanda, M.; Molodij, G.;
Keil, S.; Sütterlin, P.; Schmieder, B.; Bommier, V.; Aulanier, G.;
Meunier, N.; Rieutord, M.; Rondi, S.
2008sf2a.conf..569R Altcode:
We study the influence of large and small scales photospheric
motions on the destabilization of an eruptive filament, observed
on October 6, 7, and 8, 2004 as part of an international observing
campaign (JOP 178). Large-scale horizontal flows are invetigated
from a series of MDI/SOHO full-disc Dopplergrams and magnetograms
from THEMIS. Small-scale horizontal flows were derived using local
correlation tracking on TRACE satellite, Dutch Open Telescope (DOT)
and The Dunn Solar telescope (DST) data. The topology of the flow field
changed significantly during the filament eruptive phase, suggesting
a possible coupling between the surface flow field and the coronal
magnetic field. We measured an increase of the shear below the point
where the eruption starts and a decrease in shear after the eruption. We
conclude that there is probably a link between changes in surface flow
and the disappearance of the eruptive filament.

---------------------------------------------------------
Title: On Lyman-line asymmetries in quiescent prominences
Authors: Gunár, S.; Heinzel, P.; Anzer, U.; Schmieder, B.
2008A&A...490..307G Altcode:
Aims: We study the asymmetries of the synthetic hydrogen Lyman
lines and the process responsible for their formation. Methods: To obtain the synthetic Lyman line profiles, we use a
multi-thread prominence fine-structure model consisting of identical
2D threads. The 2D thread models are in MHS equilibrium, include an
empirical prominence-corona transition region, and solve consistently
2D non-LTE radiative transfer. Each thread of the multi-thread model
has a randomly assigned line-of-sight (LOS) velocity. Results:
The synthetic Lyman spectrum obtained by multi-thread modelling
exhibits substantial asymmetries of the line profiles, even though
the LOS velocities of individual threads are only of the order of 10
km s-1. Moreover, our results indicate that the synthetic
Lyman-α profiles may exhibit an opposite asymmetry to that of the
higher Lyman lines. Conclusions: The presence and behaviour
of the asymmetrical profiles of the synthetic Lyman lines agree with
observed profiles acquired by SUMER. Appendix A is only available
in electronic form at http://www.aanda.org

---------------------------------------------------------
Title: NLTE modelling of the flaring atmosphere above sunspot
Authors: Berlicki, A.; Heinzel, P.; Schmieder, B.; Li, H.
2008A&A...490..315B Altcode:
Aims: We performed an analysis of the solar flaring atmosphere above
sunspots. During the flare on October 20, 2003 many flaring structures
were observed projected onto the sunspots. We analysed the Hα and
Ca II line profiles emitted by the ribbons partially overlapping the
sunspots. In the penumbra, the line intensity in the far wings is lower
than in a typical quiet Sun profile but the core emission of Hα and
Ca II lines is typical for flares. We tried to find the structure of
the flare observed above the sunspot penumbra using the observations
of these chromospheric line profiles. Methods: NLTE radiative
transfer techniques allowed us to model the atmosphere of flaring
structures and fit both the synthetic Hα and Ca II line profiles to
the observed ones. We have derived semiempirical models of the flaring
structure observed above sunspots. Results: Our analysis shows
that the flare emission observed within the sunspot penumbra comes from
geometrically thin loop-like structures (cool flare loops) located
above the fibrils of the penumbra. The structure of the penumbra
located below the flare is almost not affected by the flare i.e. the
flare emission in Hα and Ca II comes not from the upper chromosphere
but from the structures that are higher in the corona. Therefore, a
two-component modelling is necessary to reproduce the flare emission
above the sunspot penumbra detected in our observations.

---------------------------------------------------------
Title: Hinode, TRACE, SOHO, and Ground-based Observations of a
Quiescent Prominence
Authors: Heinzel, P.; Schmieder, B.; Fárník, F.; Schwartz, P.;
Labrosse, N.; Kotrč, P.; Anzer, U.; Molodij, G.; Berlicki, A.;
DeLuca, E. E.; Golub, L.; Watanabe, T.; Berger, T.
2008ApJ...686.1383H Altcode:
A quiescent prominence was observed by several instruments on
2007 April 25. The temporal evolution was recorded in Hα by the
Hinode SOT, in X-rays by the Hinode XRT, and in the 195 Å channel by
TRACE. Moreover, ground-based observatories (GBOs) provided calibrated
Hα intensities. Simultaneous extreme-UV (EUV) data were also taken by
the Hinode EIS and SOHO SUMER and CDS instruments. Here we have selected
the SOT Hα image taken at 13:19 UT, which nicely shows the prominence
fine structure. We compare this image with cotemporaneous ones taken
by the XRT and TRACE and show the intensity variations along several
cuts parallel to the solar limb. EIS spectra were obtained about half
an hour later. Dark prominence structure clearly seen in the TRACE and
EIS 195 Å images is due to the prominence absorption in H I, He I,
and He II resonance continua plus the coronal emissivity blocking due
to the prominence void (cavity). The void clearly visible in the XRT
images is entirely due to X-ray emissivity blocking. We use TRACE, EIS,
and XRT data to estimate the amount of absorption and blocking. The
Hα integrated intensities independently provide us with an estimate of
the Hα opacity, which is related to the opacity of resonance continua
as follows from the non-LTE radiative-transfer modeling. However,
spatial averaging of the Hα and EUV data have quite different natures,
which must be taken into account when evaluating the true opacities. We
demonstrate this important effect here for the first time. Finally,
based on this multiwavelength analysis, we discuss the determination
of the column densities and the ionization degree of hydrogen in
the prominence.

---------------------------------------------------------
Title: Modelling of the Flare Observed Above Sunspot Penumbra
Authors: Berlicki, A.; Heinzel, P.; Schmieder, B.; Li, H.
2008ESPM...12.3.19B Altcode:
The solar flaring atmosphere above sunspot observed during the event
on October 20, 2003 was analysed. Many flaring structures were visible
in projection onto the sunspot penumbra. We analysed the H? and Ca
II line profiles emitted by the ribbons partially overlapping the
sunspots. These observations were performed with the Multi-channel
Infrared Solar Spectrograph (MISS) at Purple Mountain Observatory (PMO,
China). In the sunspot penumbra, the line intensity in far wings
is lower than in a typical quiet-Sun profile but in the line centre
the intensity of H? and Ca II lines is typical for flares. Using 1D
approximation we tried to find the vertical structure of the flare
observed above sunspot penumbra using the observations of these
chromospheric line profiles. NLTE radiative transfer techniques
allowed us to model the atmosphere of flaring structures and fit both
the synthetic H? and Ca II line profiles to the observed ones. We
have determined semiempirical models of the flaring structure observed
above sunspots. In our analysis we showed that the flare emission
observed within sunspot penumbra comes from geometrically thin loop-like
structures located above the fibrils of the penumbra. The structure
of the penumbra located below the flare is almost not affected by
the flare. The flare emission in chromospheric lines comes not from
the upper chromosphere but from the structures located higher in the
corona. Therefore, we performed two-component modelling which well
reproduce the flare emission above sunspot penumbra. In our model of
the flaring layer we included the transition region which is necessary
to obtain agreement between the observed and calculated line profiles.

---------------------------------------------------------
Title: Prominence and its Coronal Cavity Observed by Hinode, TRACE
and SOHO
Authors: Schmieder, B.; Heinzel, P.; Schwartz, P.; Gunar, S.
2008ESPM...12.2.95S Altcode:
We will first give a definition of what is a prominence according to
the glossary of Solar Physicists. A prominence is a filament observed
at the limb. A filament lies over the inversion line of photospheric
longitudinal magnetic field and is supported in dips of horizontal
magnetic field lines. Recent models of flux tubes prove that fine
structures of prominences could be represented by vertical structures
embedded in dips of horizontal field lines. Observations of a
prominence observed in H? by Hinode/SOT and the solar tower of Meudon
show a very high dynamic nature. SUMER spectra in Lyman series show
no reverse profiles indicating a large prominence corona transition
region. This prominence is surrounded by a large coronal cavity
as show spatial telescopes (TRACE, XRT). These results will be
discussed in term of different formation models.

---------------------------------------------------------
Title: On Lyman-line Asymmetries in Quiescent Prominences
Authors: Gunár, S.; Heinzel, P.; Anzer, U.; Schmieder, B.
2008ESPM...12.3.18G Altcode:
We present a new study of the asymmetries of synthetic hydrogen Lyman
line profiles and suggest the mechanism of their formation. In
order to obtain the synthetic Lyman line profiles, we use multi-thread
prominence fine-structure model consisting of identical vertical
2D threads. The 2D thread models are in magnetohydrostatic (MHS)
equilibrium, include an empirical prominence-corona transition
region (PCTR) and consistently solve the 2D non-LTE radiative
transfer. Individual threads of the multi-thread fine-structure model
have a randomly assigned LOS velocities. The synthetic Lyman
spectrum obtained by our multi-thread modelling exhibits substantial
asymmetries of the line profiles even thought the LOS velocities
of individual threads are only of the order of 10 km s-1. Moreover,
our results show that the synthetic Lyman-? profiles may exhibit an
opposite asymmetry as compared to higher Lyman lines. These results are
in agreement with the observed Lyman line profiles from SOHO/SUMER. The presence and the behaviour of the asymmetrical profiles of the
synthetic Lyman spectrum is in agreement with observed profiles taken
by SUMER.

---------------------------------------------------------
Title: Solar Prominence Diagnostic with Hinode/EIS
Authors: Labrosse, N.; Schmieder, B.; Heinzel, P.; Gunar, S.
2008ESPM...12.2.21L Altcode:
We report here on observations of a solar prominence obtained on 26
April 2007 using the Extreme Ultraviolet Imaging Spectrometer (EIS)
on Hinode. Selected profiles for lines with formation temperatures
between log(T)=4.7 and log(T)=6.3 are given and are used to explain
the existence of dark features in the raster images. We estimate
the contribution of the He II 256.32 Å line in the raster image at
256 Å in the prominence region. We compare the observed prominence
profiles with theoretical profiles from non-LTE radiative transfer
models and deduce the contribution of resonant scattering in the He
II 256 Å emission.

---------------------------------------------------------
Title: Magnetic field changes preceding filament eruptions and
coronal mass ejections
Authors: Schmieder, B.; Török, T.; Aulanier, G.
2008AIPC.1043..260S Altcode:
Solar filaments (or prominences) can be represented by twisted flux
ropes in a bipolar magnetic environment. In such models, the dipped
field lines of the flux rope carry the filament material and parasitic
polarities in the filament channel are responsible for the existence
of the lateral feet of filaments. Most filaments eventually erupt, in
many cases as part of a coronal mass ejection (CME). Such eruptions are
often preceded by detectable changes in the photospheric magnetic field
in the vicinity of the filament. We first review recent observations of
such changes due to large-scale flows or variations of the background
magnetic field, and we discuss their role in eruptions. We then focus
on emerging flux in the vicinity of filament channels. It has been
suggested that magnetic reconnection between the emerging flux and
the pre-existing coronal field can trigger filament eruptions and
CMEs. For a particular event, observed with Hinode/XRT, we observe
signatures of such reconnection, but no eruption of the filament. We
present a numerical simulation of this event and we briefly argue why
no eruption took place in this case.

---------------------------------------------------------
Title: Multiple Ribbons of a M1.6 Flare Related to the Magnetic
Configuration of the NOAA AR 365
Authors: Chandra, R.; Schmieder, B.; Aulanier, G.; Malherbe, M. J.
2008ESPM...12.2.65C Altcode:
The aim of this paper is to understand the magnetic configuration
of an active region NOAA 365 and its evolution before and after the
occurrence of a M1.6 flare in order to understand the magnetic origin
of the flare and its development at particularly the ribbons. We analyze a M1.6 flare occurring in the active region NOAA 365,
using space instruments (SOHO/MDI, EIT, TRACE, RHESSI) as well as
ground based instruments i.e. the MSDP spectrograph of the Meudon
solar tower. The analysis of the magnetic topology of the region is
done by using a force-free field linear extrapolation code of the
photospheric field proposed in the database FROMAGE. Two series
of ribbons are identified, signature of the reconnection, the main
ribbons in the center of the active region and secondary ribbons at
the periphery of the active region. The main ribbons have a `J' shape,
typical shape for large emerging flux tube. The secondary ribbons are
explained by the magnetic configuration.

---------------------------------------------------------
Title: Topological Departures from Translational Invariance along
a Filament Observed by THEMIS
Authors: Dudík, J.; Aulanier, G.; Schmieder, B.; Bommier, V.;
Roudier, T.
2008SoPh..248...29D Altcode: 2008SoPh..tmp...53D
We study the topology of the 3D magnetic field in a filament channel
to address the following questions: Is a filament always formed in a
single flux tube? How does the photospheric magnetic field lead to
filament interruptions and to feet formation? What is the relation
between feet-related field lines and the parasitic polarities? What
can topological analyses teach us about EUV filament channels? To do
so, we consider a filament observed on 6 October 2004 with THEMIS/MTR,
in Hα with the full line profile simultaneously and cospatially with
its photospheric vector magnetic field. The coronal magnetic field
was calculated from a "linear magnetohydrostatic" extrapolation of a
composite THEMIS-MDI magnetogram. Its free parameters were adjusted
to get the best match possible between the distribution of modeled
plasma-supporting dips and the Hα filament morphology. The model
results in moderate plasma β≤1 at low altitudes in the filament,
in conjunction with non-negligible departures from force-freeness
measured by various metrics. The filament here is formed by a split
flux tube. One part of the flux tube is rooted in the photosphere aside
an observed interruption in the filament. This splitted topology is
due to strong network polarities on the edge of the filament channel,
not to flux concentrations closer to the filament. We focus our study
to the northwest portion of the filament. The related flux tube is
highly fragmented at low altitudes. This fragmentation is due to small
flux concentrations of two types. First, some locally distort the
tube, leading to noticeable thickness variations along the filament
body. Second, parasitic polarities, associated with filament feet,
result in secondary dips above the related local inversion line. These
dips belong to long field lines that pass below the flux tube. Many
of these field lines are not rooted near the related foot. Finally,
the present model shows that the coronal void interpretation cannot
be ruled out to interpret the wideness of EUV filament channels.

---------------------------------------------------------
Title: Large-scale horizontal flows in the solar
photosphere. III. Effects on filament destabilization
Authors: Roudier, T.; Švanda, M.; Meunier, N.; Keil, S.; Rieutord,
M.; Malherbe, J. M.; Rondi, S.; Molodij, G.; Bommier, V.; Schmieder, B.
2008A&A...480..255R Altcode: 2007arXiv0711.3112R
Aims:We study the influence of large-scale photospheric motions on
the destabilization of an eruptive filament, observed on October 6,
7, and 8, 2004, as part of an international observing campaign (JOP
178). Methods: Large-scale horizontal flows were investigated
from a series of MDI full-disc Dopplergrams and magnetograms. From
the Dopplergrams, we tracked supergranular flow patterns using the
local correlation tracking (LCT) technique. We used both LCT and manual
tracking of isolated magnetic elements to obtain horizontal velocities
from magnetograms. Results: We find that the measured flow
fields obtained by the different methods are well-correlated on large
scales. The topology of the flow field changed significantly during
the filament eruptive phase, suggesting a possible coupling between
the surface flow field and the coronal magnetic field. We measured
an increase in the shear below the point where the eruption starts
and a decrease in shear after the eruption. We find a pattern in the
large-scale horizontal flows at the solar surface that interact with
differential rotation. Conclusions: We conclude that there is
probably a link between changes in surface flow and the disappearance
of the eruptive filament.

---------------------------------------------------------
Title: Magnetic Causes of the Eruption of a Quiescent Filament
Authors: Schmieder, B.; Bommier, V.; Kitai, R.; Matsumoto, T.; Ishii,
T. T.; Hagino, M.; Li, H.; Golub, L.
2008SoPh..247..321S Altcode: 2007SoPh..tmp..213S
During the JOP178 campaign in August 2006, we observed the
disappearance of our target, a large quiescent filament located at
S25°, after an observation time of three days (24 August to 26
August). Multi-wavelength instruments were operating: THEMIS/MTR
("MulTi-Raies") vector magnetograph, TRACE ("Transition Region and
Coronal Explorer") at 171 Å and 1600 Å and Hida Domeless Solar
telescope. Counter-streaming flows (+/−10 km s−1) in the
filament were detected more than 24 hours before its eruption. A slow
rise of the global structure started during this time period with a
velocity estimated to be of the order of 1 km s−1. During
the hour before the eruption (26 August around 09:00 UT) the velocity
reached 5 km s−1. The filament eruption is suspected to
be responsible for a slow CME observed by LASCO around 21:00 UT on 26
August. No brightening in Hα or in coronal lines, no new emerging
polarities in the filament channel, even with the high polarimetry
sensitivity of THEMIS, were detected. We measured a relatively large
decrease of the photospheric magnetic field strength of the network
(from 400 G to 100 G), whose downward magnetic tension provides
stability to the underlying stressed filament magnetic fields. According
to some MHD models based on turbulent photospheric diffusion, this
gentle decrease of magnetic strength (the tension) could act as the
destabilizing mechanism which first leads to the slow filament rise
and its fast eruption.

---------------------------------------------------------
Title: Magnetic clouds seen at different locations in the heliosphere
Authors: Rodriguez, L.; Zhukov, A. N.; Dasso, S.; Mandrini, C. H.;
Cremades, H.; Cid, C.; Cerrato, Y.; Saiz, E.; Aran, A.; Menvielle,
M.; Poedts, S.; Schmieder, B.
2008AnGeo..26..213R Altcode:
We analyze two magnetic clouds (MCs) observed in different points
of the heliosphere. The main aim of the present study is to provide
a link between the different aspects of this phenomenon, starting
with information on the origins of the MCs at the Sun and following
by the analysis of in-situ observations at 1 AU and at Ulysses. The
candidate source regions were identified in SOHO/EIT and SOHO/MDI
observations. They were correlated with H-α images that were obtained
from ground-based observatories. Hints on the internal magnetic field
configuration of the associated coronal mass ejections are obtained
from LASCO C2 images. In interplanetary space, magnetic and plasma
moments of the distribution function of plasma species (ACE/Ulysses)
were analyzed together with information on the plasma composition,
and the results were compared between both spacecraft in order to
understand how these structures interact and evolve in their cruise
from the Sun to 5 AU. Additionally, estimates of global magnitudes of
magnetic fluxes and helicity were obtained from magnetic field models
applied to the data in interplanetary space. We have found that these
magnetic characteristics were well kept from their solar source, up to
5 AU where Ulysses provided valuable information which, together with
that obtained from ACE, can help to reinforce the correct matching of
solar events and their interplanetary counterparts.

---------------------------------------------------------
Title: Magnetic Field Vector Measurements with THEMIS
Authors: Bommier, V.; González, M. J. M.; Schmieder, B.; Landi
Degl'Innocenti, E.
2008ASPC..383..123B Altcode:
The aim of the present work is twofold: a) to validate the
Milne-Eddington UNNOFIT inversion by comparing its results with
those of the SIR inversion, which is in LTE but does not assumes
the Milne-Eddington atmosphere; b) to present a decrease of the
network local average magnetic field strength in the vicinity of a
filament/prominence, observed before its disppearance, suggesting that
the disappearance results from a weakening of the magnetic support.

---------------------------------------------------------
Title: Interaction of magnetic field systems leading to an X1.7
flare due to large-scale flux tube emergence
Authors: Li, H.; Schmieder, B.; Song, M. T.; Bommier, V.
2007A&A...475.1081L Altcode:
Aims:The aim of this paper is to understand the magnetic configuration
and evolution of an active region, which permitted an X1.7 flare to
be observed during the decaying phase of a long-duration X1.5 flare
on 2005 September 13. Methods: We performed a multi-wavelength
analysis using data from space-borne (Solar and Heliospheric Observatory
(SOHO), Transition Region and Coronal Explorer (TRACE), Reuven Ramaty
High-Energy Solar Spectroscopic Imager (RHESSI), GOES) and ground-based
(the French-Italian THEMIS telescope and the Huairou Video Vector
Magnetograph (HVVM)) instruments. We coaligned all the data in order to
study the origin of the flare by comparing the observed magnetic field
structures with the emissions detected by different instruments. Results: Reconstructed RHESSI images show three hard X-ray (HXR)
sources. In TRACE 195 Å images, two loops are seen: a short bright loop
and a longer one. Five ribbons are identified in Hα images, with two
of them remnant ribbons of the previous flare. We propose the following
scenario to explain the X1.7 flare. A reconnection occurs between the
short loop system and the longer loops (TRACE 195 Å). Two X-ray sources
could be the footpoints of the short loop, while the third one between
the two others is the site of the reconnection. The Hα ribbons are
the footprints in the chromosphere of the reconnected loops. During the
reconnection, the released energy is principally nonthermal according
to the RHESSI energy spectrum analysis (two orders of magnitude higher
than the maximum thermal energy). The proposed scenario is confirmed
by a nonlinear force-free field (NLFFF) extrapolation, which shows the
presence of short sheared magnetic field lines before the eruption
and less sheared ones after the reconnection, and the connectivity
of the field lines involved in the flaring activity is modified after
the reconnection process. The evolution of the photospheric magnetic
field over a few days shows the continuous emergence of a large-scale
magnetic flux tube, the tongue-shape of the two main polarities of
the active region being the signature of such an emergence. After the
previous X1.5 flare, the emergence of the tube continues and favors
new magnetic energy storage and the onset of the X1.7 flare.

---------------------------------------------------------
Title: Division II / Working Group International Collaboration in
Space Weather
Authors: Webb, David F.; Gopalswamy, Nat; Liu, William; Sibeck,
David G.; Schmieder, Brigitte; Wang, Jingxiu; Wang, Chi
2007IAUTB..26..107W Altcode:
The IAU Division II WG on International Collaboration in Space Weather
has as its main goal to help coordinate the many activities related to
space weather at an international level. The WG currently includes
the international activities of the International Heliospheric
Year (IHY), the International Living with a Star (ILWS) program,
the CAWSES (Climate and Weather of the Sun-Earth System) Working
Group on Sources of Geomagnetic Activity, and Space Weather Studies
in China. The coordination of IHY activities within the IAU is led
by Division II under this working group. The focus of this half-day
meeting was on the activities of the IHY program. About 20 people
were in attendance. The Chair of the WG, David F. Webb, gave a brief
introduction noting that the meeting would have two parts: first, a
session on IHY activities emphasizing IHY Regional coordination and,
second, a general discussion of the other programs of the WG involving
international Space Weather activities.

---------------------------------------------------------
Title: Spectrophotometric analysis of Ellerman bombs in the Ca II,
Hα, and UV range
Authors: Pariat, E.; Schmieder, B.; Berlicki, A.; Deng, Y.; Mein,
N.; López Ariste, A.; Wang, S.
2007A&A...473..279P Altcode:
Context: Even if Ellerman bombs have been observed in the Hα line
within emerging magnetic flux regions since the early 20th century,
their origin and the mechanisms that lead to their formation have been
strongly debated. Recently, new arguments in favor of chromospheric
magnetic reconnection have been advanced. Ellerman bombs seem to be
the signature of reconnections that take place during the emergence
of the magnetic field. Aims: We have observed an active region
presenting emergence of magnetic flux. We detected and studied
Ellerman bombs in two chromospheric lines: Ca ii 8542 Å and Hα. We
investigated the link between Ellerman bombs and other structures and
phenomena appearing in an emerging active region: UV bright points,
arch filament systems, and magnetic topology. Methods: On August
3, 2004, we performed multi-wavelength observations of the active
region NOAA 10655. This active region was the target of SoHO Joint
Observation Program 157. Both SoHO/MDI and TRACE (195 Å and 1600 Å)
were used. Simultaneously, we observed in the Ca ii and Na D1 lines
with the spectro-imager MSDP mode of THEMIS. Alternately to the MSDP,
we used the MTR spectropolarimeter on THEMIS to observe in Hα and
in the Fe i doublet at 6302 Å. We derived the magnetic field vectors
around some Ellerman bombs. Results: We present the first images
of EBs in the Ca ii line and confirm that Ellerman bombs can indeed
be observed in the Ca ii line, presenting the same “moustache”
geometry profiles as in the Hα line, but with a narrower central
absorption in the Ca ii line, in which the peaks of emission are
around ±0.35 Å. We noticed that the Ellerman bombs observed in the
wings of Ca ii line have an elongated shape - the length about 50%
greater than the width. We derived mean semi-axis lengths of 1.4”
× 2.0”. In the UV time profiles of the Ellerman bombs, we noticed
successive enhanced emissions. The distribution of lifetimes of these
individual impulses presents a strong mode around 210 s. Study of the
magnetic topology shows that 9 out of the 13 EBs are located on the
inversion line of the longitudinal field and that some typical examples
might be associated with a bald patch topology. Conclusions: We
provide new arguments in favor of the reconnection origin of Ellerman
bombs. The different individual impulses observed in UV may be related
to a bursty mode of reconnection. We also show that this Ca ii 8542
Å chromospheric line is a good indicator of Ellerman bombs and can
bring new information about these phenomena.

---------------------------------------------------------
Title: What can We learn about Filaments from Vector Magnetograms?
Authors: Schmieder, B.; Aulanier, G.; Lopez Ariste, A.
2007ASPC..369..137S Altcode:
Theoretical MHD models of filaments have predicted the existence
of dips in magnetic field lines supporting the cool filament
plasma. Condensation would be one of the possible mechanism of filament
formation. The controversy is still alive. Filament fine structures are
of dynamical nature and injection of cold material (like surges) from
the photosphere would be the proposed mechanism. With the presence of
dips, the magnetic lines are predicted to be tangent to the photosphere,
near the barbs, footpoints of the prominences. The injection model
predicted nearly vertical structures of the barbs rooted in the
minority polarities. Measurements of vector magnetic field in
filament channels can answer to these questions and will be possible
with Solar-B. Recent results have been obtained with THEMIS vector
magnetograph in Tenerife, suggesting that dips are really present in
filament channel leading to the conclusion that the observed magnetic
topology in the photosphere fully supports models of prominences based
on dips.

---------------------------------------------------------
Title: Eruptive and Compact Flares
Authors: Schmieder, B.; Aulanier, G.; Delannée, C.; Berlicki, A.
2007AIPC..934...22S Altcode:
Solar two ribbon flares are commonly explained by magnetic field
reconnections in the high corona. During the reconnection energetic
particles (electrons and protons) are accelerated from the reconnection
site. These particles are following the magnetic field lines down
to the chromosphere. As the plasma density is higher in these lower
layers, there are collisions and emission of radiation. Thus after
the flare bright ribbons are observed at both ends of loops. These
ribbons are typically observed in Hα and in EUV with SoHO and
TRACE. As the time is going, these ribbons are expanding away of each
other. In most studied models, the reconnection site is an X-point,
where two magnetic separatrices intersect. They define four distinct
connectivity domains, across which the magnetic connectivity changes
discontinuously. In this paper, we present a generalization of this
model to 3D complex magnetic topologies where there are no null points,
but quasi-separatrices layers instead. In that case, while the ribbons
spread away during reconnection, we show that magnetic field lines
can quickly slip along them. We propose that this new phenomenon could
explain fast extension of Hα and TRACE 1600 Å ribbons, fast moving
HXR footpoints as observed by RHESSI, and that it is observed in soft
X rays with Hinode/XRT. We also show how this concept can be applied
to model the non-wave nature of EIT waves.

---------------------------------------------------------
Title: Properties of prominence fine-structure threads derived from
SOHO/SUMER hydrogen Lyman lines
Authors: Gunár, S.; Heinzel, P.; Schmieder, B.; Schwartz, P.;
Anzer, U.
2007A&A...472..929G Altcode:
Context: The SOHO/SUMER observations provide us for the first time with
the prominence spectra in the Lyman-α line outside the attenuator
together with the higher members of the hydrogen Lyman series. Aims: We derive the prominence fine-structure thread properties
by comparing the SOHO/SUMER hydrogen Lyman series observations with
the synthetic Lyman lines. Methods: To obtain the synthetic
profiles of the Lyman lines, we used 2D prominence fine-structure
thread models with a PCTR and consistently solved the 2D non-LTE
multilevel radiative transfer. The trial-and-error method was applied
to find the model with the best agreement between the synthetic Lyman
line profiles and the observed ones. Results: The properties of
the resulting model with the best match of the synthetic and observed
line profiles are central (minimum) temperature T0 = 7000
K, maximum column mass in the centre of the thread M0 =
1.1×10-4 g cm-2, horizontal field strength in
the middle of the thread Bx(0) = 6 Gauss and the boundary
pressure p0 = 0.015 dyn cm-2. Conclusions:
The Lyman line profiles observed by SOHO/SUMER can be better reproduced
by using multi-thread models consisting of a set of the 2D prominence
fine-structure threads placed perpendicularly to the line-of-sight,
rather than with the single-thread model.

---------------------------------------------------------
Title: Photospheric flows around a quiescent filament
Authors: Rondi, S.; Roudier, Th.; Molodij, G.; Bommier, V.; Keil,
S.; Sütterlin, P.; Malherbe, J. M.; Meunier, N.; Schmieder, B.;
Maloney, P.
2007A&A...467.1289R Altcode:
Context: The horizontal photospheric flows below and around a
filament are one of the components in the formation and evolution of
filaments. Few studies exist because they require multiwalength time
sequences at high spatial resolution. Aims: Our objective
is to measure the horizontal photospheric flows associated
with the evolution and eruption of a filament. Methods:
We present observations obtained in 2004 during the international
JOP 178 campaign which involved eleven instruments both in space
and at ground based observatories. We use TRACE WL, DOT and DST
observation to derive flow maps which are then coaligned with
intensity images and with the vector magnetic field map obtained with
THEMIS/MTR. Results: Several supergranulation cells cross the
Polarity Inversion Line (PIL) and can transport magnetic flux through
the PIL, in particular parasitic polarities. We present a detailed
example of the formation of a secondary magnetic dip at the location
of a filament footpoint. Large-scale converging flows, which could
exist along the filament channel and contribute to its formation, are
not observed. Before the filament's eruptive phase, we observe both
parasitic and normal polarities being swept by a continuously diverging
horizontal flow located in the filament gap. The disappearance of the
filament initiates in this gap. Such purely horizontal motions could
lead to destabilization of the filament and could trigger the sudden
filament disappearance.

---------------------------------------------------------
Title: Prominence Parameters from 2D Modeling of Lyman Lines Measured
with SUMER
Authors: Gunár, S.; Heinzel, P.; Schmieder, B.; Anzer, U.
2007ASPC..368..317G Altcode:
We present SOHO/SUMER observations of a solar prominence in the hydrogen
Lyman series lines and compare the line profiles with the synthetic
ones obtained using our 2D prominence modeling. The observations
contain the Ly-β, Ly-γ, and Ly-δ lines on 25 May 2005. In
order to derive the prominence parameters we used our 2D fine structure
models of vertical threads in magnetohydrostatic (MHS) equilibrium. By
varying the input model parameters (central temperature, boundary
pressure, magnetic field, central column mass and turbulent velocity)
we obtained a model having the synthetic Lyman line profiles in good
agreement with the observed ones. In this way we are able to determine
the structure of the magnetic dip and the thermodynamical parameters
in the observed prominence.

---------------------------------------------------------
Title: Spectrophotometry of Ellerman Bombs with THEMIS
Authors: Pariat, E.; Schmieder, B.; Berlicki, A.; López Ariste, A.
2007ASPC..368..253P Altcode:
During coordinated campaigns with THEMIS and space missions (TRACE,
SOHO) emerging flux was observed in multi-wavelengths. Ellerman bombs
(EBs) have been identified in TRACE 1600 Å and in chromospheric
lines. The Hα and Ca II 8542 Å lines present two enhanced emission
peaks respectively at 1 Å and at 0.35 Å which are signatures of
EBs. Vector magnetic field measured in the photosphere are consistent
with previous results indicating the presence of bald-patches under
the EBs and consequently the emergence of horizontal flux tubes from
below the photosphere.

---------------------------------------------------------
Title: Slip running reconnection in the Sun's atmosphere observed
by RHESSI, SOHO, TRACE and Hinode
Authors: Schmieder, B.; Aulanier, G.; Démoulin, P.; Pariat, E.;
Golub, L.
2007AGUSMSH22A..01S Altcode:
Solar double ribbon flares are commonly explained by magnetic field
reconnections in the high corona. The bright ribbons, typically
observed in Halpha, in EUV with SoHO, TRACE correspond to the ends
of the reconnected loops. In most studied cases, the reconnection
site is an X-point, where two magnetic separatrices intersect. In
this presentation, we show a generalization of this model to 3D
complex magnetic topologies where there are no null points, but
quasi-separatrices layers instead. In that case, while the ribbons
spread away during reconnection, we show that magnetic field lines
can quickly slip along them. We propose that this new phenomenon
could explain also fast moving HXR footpoints as observed by RHESSI,
and that it may be observed in soft X rays with XRT.

---------------------------------------------------------
Title: Non-LTE Analysis of Lyman-Line Observations of a Filament
with SUMER
Authors: Schwartz, P.; Schmieder, B.; Heinzel, P.
2007ASPC..368..359S Altcode: 2007arXiv0704.3539S
We present non-LTE diagnostics of the filament observed by SOHO/SUMER
on May 27, 2005 in the whole Lyman series. The filament was situated
close to the disk center. The Lα observations were carried out with
normal voltage of detector A. The slit was placed at the central part
of the detector -- outside the Lα attenuator. Therefore, the observed
profiles of this line could be calibrated reliably.

---------------------------------------------------------
Title: Improvement of the Coimbra Spectroheliograph (1988 -- 1992)
Authors: Bualé, I.; Mouradian, Z.; Schmieder, B.
2007ASPC..368...15B Altcode:
We summarize the parallel modernization of the identical
spectroheliographs at Coimbra and Meudon.

---------------------------------------------------------
Title: Spectral Diagnostics of the Magnetic Field Orientation in a
Prominence Observed with SOHO/SUMER
Authors: Schmieder, B.; Gunár, S.; Heinzel, P.; Anzer, U.
2007SoPh..241...53S Altcode:
During several campaigns focused on prominences we have obtained
coordinated spectral observations from the ground and from space. The
SOHO/SUMER spectrometer allows us to observe, among others, the
whole Lyman series of hydrogen, while the Hα line was observed
by the MSDP spectrograph at the VTT. For the Lyman lines, non-LTE
radiative-transfer computations have shown the importance of the optical
thickness of the prominence - corona transition region (PCTR) and its
relation to the magnetic field orientation for the explanation of the
observed line profiles. Moreover, Heinzel, Anzer, and Gunár (2005,
Astron. Astrophys.442, 331) developed a 2D magnetostatic model of
prominence fine structures that demonstrates how the shapes of Lyman
lines vary, depending on the orientation of the magnetic field with
respect to the line of sight. To support this result observationally,
we focus here on a round-shaped filament observed during three days as
it was crossing the limb. The Lyman profiles observed on the limb are
different from day to day. We interpret these differences as being due
to the change of orientation of the prominence axis (and therefore the
magnetic field direction) with respect to the line of sight. The Lyman
lines are more reversed if the line of sight is across the prominence
axis as compared to the case when it is aligned along its axis.

---------------------------------------------------------
Title: The dynamic solar chromosphere
Authors: Schmieder, B.
2007AIPC..895...49S Altcode:
With the new ground-based and space instrumentation observing the solar
atmosphere, it is clear nowadays that the quiet sun is of dynamical
nature. The Swedish 1m telescope (SST) with its spatial resolution
better than 0.2 arc sec. allows us to follow the dynamics of the
fine structures observed in photospheric, as well in chromospheric
lines. THEMIS with its high magnetic sensitivity reaching 10-5
permits to relate the dynamics of fine structures of spicules and
prominences to the small scale magnetic evolution: i.e. canceling and
emerging flux. Space instruments (SOHO/MDI, TRACE 1600 Å) observe the
activity of the photosphere/chromosphere with high cadence (&lt; 10
sec) and high resolution (larger than 0.5 arc sec). This review
concerns observations of spicules, mottles and filaments obtained
in chromospheric lines. The dynamics is obtained by measuring the
flows using Dopplershifts and horizontal displacements by time slice
methods. The observed velocities are interpreted either by acoustic
shock wave or magnetic reconnection models.

---------------------------------------------------------
Title: What is the role of magnetic null points in large flares?
Authors: Schmieder, B.; Mandrini, C. H.; Démoulin, P.; Aulanier,
G.; Li, H.; Berlicki, A.
2007AdSpR..39.1840S Altcode:
We have performed the analysis of the magnetic topology of active
region NOAA 10486 before two large flares occurring on October 26
and 28, 2003. The 3D extrapolation of the photospheric magnetic field
shows the existence of magnetic null points when using two different
methods. We use TRACE 1600 Å and 195 Å brightenings as tracers of
the energy release due to magnetic reconnections. We conclude on the
three following points: The small events observed before the flares are
related to low lying null points. They are long lasting and associated
with low energy release. They are not triggering the large flares. On October 26, a high altitude null point is found. We look for
bright patches that could correspond to the signatures of coronal
reconnection at the null point in TRACE 1600 Å images. However,
such bright patches are not observed before the main flare, they are
only observed after it. On October 28, four ribbons are observed
in TRACE images before the X17 flare. We interpret them as due to a
magnetic breakout reconnection in a quadrupolar configuration. There
is no magnetic null point related to these four ribbons, and this
reconnection rather occurs at quasi-separatrix layers (QSLs). We
conclude that the existence of a null point in the corona is neither
a sufficient nor a necessary condition to give rise to large flares.

---------------------------------------------------------
Title: New results and future perspectives of THEMIS .
Authors: Schmieder, B.
2007MmSAI..78..191S Altcode:
We reported on scientific results obtained during the run of two
Joint Observing Programs in 2003, 2004 concerning “New emergence flux
and active regions “ (JOP157), “Filaments and their environment”
(JOP178) and preliminary results of more recent campaigns. Results
concerning filament support show the capability of THEMIS/MTR to
detect weak magnetic polarities and measure the vector magnetic field
curvature. Tangent magnetic field lines to the solar surface were found
at the feet of filaments and also in Halpha +/-0.35 Å bright points
close to penumbra. The bright points would be not due to high magnetic
field concentration (1 KG) but to magnetic reconnection. The stability
of filaments could be due to the existence of constant flux in its
corridor where overlying arcades are anchored. The comparison
between THEMIS/MSDP and MDI shows the gain that we get. THEMIS is
well adapted for measurements of weak field, the noise is much reduce
compared to other instruments. For future campaigns we recommand to
use alternatively the two modes: MSDP and MTR.

---------------------------------------------------------
Title: Photospheric flows around a quiescent filament and CALAS
first results .
Authors: Rondi, S.; Roudier, Th.; Molodij, G.; Bommier, V.; Malherbe,
J. M.; Schmieder, B.; Meunier, N.; Rieutord, M.; Beigbeder., F.
2007MmSAI..78..114R Altcode:
The horizontal photospheric flows below and around a filament are one of
the components in the formation and evolution of filaments. Few studies
have been done so far because this requires multiwalength time sequences
with high spatial resolution. We present observations obtained in 2004
during the international JOP 178 campaign in which eleven instruments
were involved, from space and ground based observatories. Several
supergranulation cells are crossing the Polarity Inversion Line (PIL)
allowing the transport of magnetic flux through the PIL, in particular
the parasitic polarities. Before the filament eruptive phase, parasitic
and normal polarities are swept by a continuous diverging horizontal
flow located in the filament gap where the disappearance of the filament
starts. In the future, observations at high spatial resolution on a
large field-of-view would be very useful to study filaments, as they are
very large structures. We also present the first images obtained with
the use of our new 14 MPixel camera CALAS (CAmera for the LArge Scales
of the Solar Surface) (10 arcmin× 6.7 arcmin) . These are the first
large-scale and high-resolution images of the solar surface ever made.

---------------------------------------------------------
Title: Magnetic Support of Prominences
Authors: Schmieder, Brigitte
2007RoAJ...17S..53S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Gradual Phase of the X17 Flare on October 28, 2003
Authors: del Zanna, G.; Schmieder, B.; Mason, H.; Berlicki, A.;
Bradshaw, S.
2006SoPh..239..173D Altcode: 2006SoPh..239..173Z; 2006SoPh..tmp...74Z
We present SOHO/CDS observations taken during the gradual phase of
the X17 flare that occurred on October 28, 2003. The CDS data are
supplemented with TRACE and ground-based observations. The spectral
observations allow us to determine velocities from the Doppler
shifts measured in the flare loops and in the two ribbon kernels,
one hour and a half after the flare peak. Strong downflows (&gt;70 km
s-1) are observed along the loop legs at transition-region
temperatures. The velocities are close to those expected for free
fall. Observations and results from a hydrodynamic simulation are
consistent with the heating taking place for a short time near the
top of the arcade. Slight upflows are observed in the outer edges of
the ribbons (&lt;60 km s-1) in the EUV lines formed at log
T &lt; 6.3. These flows could correspond to the so-called “gentle
evaporation.” At “flare” temperatures (Fe xix, log T = 6.9),
no appreciable flows are observed. The observations are consistent
with the general standard reconnection models for two-ribbons flares.

---------------------------------------------------------
Title: Companion Event and Precursor of the X17 Flare on 28 October
2003
Authors: Mandrini, C. H.; Demoulin, P.; Schmieder, B.; Deluca, E. E.;
Pariat, E.; Uddin, W.
2006SoPh..238..293M Altcode: 2006SoPh..tmp...79M
A major two-ribbon X17 flare occurred on 28 October 2003, starting
at 11:01 UT in active region NOAA 10486. This flare was accompanied
by the eruption of a filament and by one of the fastest halo coronal
mass ejections registered during the October-November 2003 strong
activity period. We focus on the analysis of magnetic field (SOHO/MDI),
chromospheric (NainiTal observatory and TRACE), and coronal (TRACE) data
obtained before and during the 28 October event. By combining our data
analysis with a model of the coronal magnetic field, we concentrate
on the study of two events starting before the main flare. One
of these events, evident in TRACE images around one hour prior to
the main flare, involves a localized magnetic reconnection process
associated with the presence of a coronal magnetic null point. This
event extends as long as the major flare and we conclude that it is
independent from it. A second event, visible in Hα and TRACE images,
simultaneous with the previous one, involves a large-scale quadrupolar
reconnection process that contributes to decrease the magnetic field
tension in the overlaying field configuration; this allows the filament
to erupt in a way similar to that proposed by the breakout model,
but with magnetic reconnection occurring at Quasi-Separatrix Layers
(QSLs) rather than at a magnetic null point.

---------------------------------------------------------
Title: Study of an extended EUV filament using SoHO/SUMER observations
of the hydrogen Lyman lines
Authors: Schwartz, P.; Heinzel, P.; Schmieder, B.; Anzer, U.
2006A&A...459..651S Altcode:
Context: .In previous work we determined the 3D structure of an
EUV extension of the filament observed by SoHO/CDS on 15 October
1999. The determination of the 3D structure depends on the optical
thickness τ912 at the hydrogen Lyman-continuum edge at
912 Å. The τ912 value was unknown, therefore it was taken
as a free parameter for the 3D-structure determinations. Aims:
.The plasma properties (including τ912) of this EUV filament
are estimated using non-LTE modelling of profiles of the hydrogen Lyman
lines. Methods: .The lines Lβ, Lδ, L ɛ, L6 and L7 were observed
by SoHO/SUMER with the slit positioned across the EUV filament. In our
modelling the EUV filament was approximated by a horizontal 1D slab with
constant pressure and the temperature decreasing vertically from the
edges to interior of the slab. The values of the geometrical thickness
of the slab in the EUV extension were taken from its 3D structure
determined for the τ912 values estimated iteratively. The
synthetic profiles were fitted to observed ones using the χ2
minimization. Results: .For the Hα-filament part we obtained
the expected results: a small geometrical thickness between several
thousand and 15 000 km, temperatures around 5000 K in the interior and
around 20 000 K in PCTRs, and pressure ~0.1~dyn~cm-2. That
leads to an optical thickness in the Hα line center larger than 1. In
the EUV extension, temperatures of 10 000-40 000 K in the interior
and 35 000-50 000 K in the vertically extended PCTRs and a pressure
of ~0.01~dyn~cm-2 were determined. Such large variations
of the temperature lead to large variations of τ912. 
Conclusions: .The EUV extension is inhomogeneous - areas both optically
thick and thin at 912 Å are present close to each other. Parts
optically thick at 912 Å are visible also in Hα as faint and tiny dark
structures around the very dark and well pronounced Hα filament. The
volume blocking mechanism is an important mechanism throughout the
whole EUV extension even in its optically thick parts. The absorption
dominates only in the Hα-filament part of the EUV filament.

---------------------------------------------------------
Title: Evolving Photospheric Flux Concentrations and Filament
Dynamic Changes
Authors: Schmieder, B.; Aulanier, G.; Mein, P.; Ariste, A. López
2006SoPh..238..245S Altcode: 2006SoPh..tmp...64S
We analyze the role of weak photospheric flux concentrations that
evolve in a filament channel, in the triggering of dynamic changes in
the shape of a filament. The high polarimetric sensitivity of THEMIS
allowed us to detect weak flux concentrations (few Gauss) associated
with the filament development. The synoptic instruments (MDI, SOLIS)
even if their sensitivity is much less than THEMIS were useful to
follow any subsequent strengthening of these flux concentrations after
their identification in the THEMIS magnetograms. We found that (1)
the northern part of the filament develops an Hα barb at the same
time that weak minority polarity elements develop near a plage; (2)
a section in the southern part of the Hα filament gradually disappears
and later reforms at the same time that several mixed-polarity magnetic
elements appear, then subsequently cancel or spread away from each
other. These changes correspond to increases in EUV emission, as
observed by TRACE, EIT, and CDS. This suggests that the plasma is
temporarily heated along the filament spine. An idealized sequence of
force-free models of this filament channel, based on plasma-supporting
magnetic dips occurring in the windings of a very weakly twisted flux
tube, naturally explains the evolution of its southern part as being
due to changes in the topology of the coronal magnetic field as the
photospheric flux concentrations evolve.

---------------------------------------------------------
Title: Magnetic Source Regions of Coronal Mass Ejections
Authors: Schmieder, Brigitte
2006JApA...27..139S Altcode:
The majority of flare activity arises in active regions which contain
sunspots, while Coronal Mass Ejection (CME) activity can also originate
from decaying active regions and even so-called quiet solar regions
which contain a filament. Two classes of CME, namely flare-related CME
events and CMEs associated with filament eruption are well reflected
in the evolution of active regions. The presence of significant
magnetic stresses in the source region is a necessary condition for
CME. In young active regions magnetic stresses are increased mainly by
twisted magnetic flux emergence and the resulting magnetic footpoint
motions. In old, decayed active regions twist can be redistributed
through cancellation events. All the CMEs are, nevertheless, caused
by loss of equilibrium of the magnetic structure. With observational
examples we show that the association of CME, flare and filament
eruption depends on the characteristics of the source regions: - the
strength of the magnetic field, the amount of possible free energy
storage, - the small- and large-scale magnetic topology of the source
region as well as its evolution (new flux emergence, photospheric
motions, cancelling flux), and - the mass loading of the configuration
(effect of gravity). These examples are discussed in the framework of
theoretical models. %k Coronal mass ejection,flare,filament eruption

---------------------------------------------------------
Title: First observation of bald patches in a filament channel and
at a barb endpoint
Authors: López Ariste, A.; Aulanier, G.; Schmieder, B.; Sainz
Dalda, A.
2006A&A...456..725L Altcode:
The 3D magnetic field topology of solar filaments/prominences is
strongly debated, because it is not directly measureable in the
corona. Among various prominence models, several are consistent
with many observations, but their related topologies are very
different. We conduct observations to address this paradigm. We
measure the photospheric vector magnetic field in several small
flux concentrations surrounding a filament observed far from disc
center. Our objective is to test for the presence/absence of magnetic
dips around/below the filament body/barb, which is a strong constraint
on prominence models, and that is still untested by observations. Our
observations are performed with the THEMIS/MTR instrument. The four
Stokes parameters are extracted, from which the vector magnetic fields
are calculated using a PCA inversion. The resulting vector fields
are then deprojected onto the photospheric plane. The 180° ambiguity
is then solved by selecting the only solution that matches filament
chirality rules. Considering the weakness of the resulting magnetic
fields, a careful analysis of the inversion procedure and its error
bars was performed, to avoid over-interpretation of noisy or ambiguous
Stokes profiles. Thanks to the simultaneous multi-wavelength THEMIS
observations, the vector field maps are coaligned with the Hα image of
the filament. By definition, photospheric dips are identifiable where
the horizontal component of the magnetic field points from a negative
toward a positive polarity. Among six bipolar regions analyzed in the
filament channel, four at least display photospheric magnetic dips,
i.e. bald patches. For barbs, the topology of the endpoint is that of
a bald patch located next to a parasitic polarity, not of an arcade
pointing within the polarity. The observed magnetic field topology in
the photosphere tends to support models of prominence based on magnetic
dips located within weakly twisted flux tubes. Their underlying and
lateral extensions form photospheric dips both within the channel and
below barbs.

---------------------------------------------------------
Title: Is Pre-Eruptive Null Point Reconnection Required for Triggering
Eruptions?
Authors: Li, Hui; Schmieder, Brigitte; Aulanier, Guillaume; Berlicki,
Arkadiusz
2006SoPh..237...85L Altcode: 2006SoPh..tmp...22L; 2006SoPh..tmp...18L
We study the magnetic field evolution and topology of the active
region NOAA 10486 before the 3B/X1.2 flare of October 26, 2003,
using observational data from the French-Italian THEMIS telescope,
the Michelson Doppler Imager (MDI) onboard Solar and Heliospheric
Observatory (SOHO), the Solar Magnetic Field Telescope (SMFT) at
Huairou Solar Observation Station (HSOS), and the Transition Region
and Coronal Explorer (TRACE). Three dimensional (3D) extrapolation of
photospheric magnetic field, assuming a potential field configuration,
reveals the existence of two magnetic null points in the corona above
the active region. We look at their role in the triggering of the main
flare, by using the bright patches observed in TRACE 1600 Å images as
tracers at the solar surface of energy release associated with magnetic
reconnection at the null points. All the bright patches observed before
the flare correspond to the low-altitude null point. They have no
direct relationship with the X1.2 flare because the related separatrix
is located far from the eruptive site. No bright patch corresponds
to the high-altitude null point before the flare. We conclude that
eruptions can be triggered without pre-eruptive coronal null point
reconnection, and the presence of null points is not a sufficient
condition for the occurrence of flares. We propose that this eruptive
flare results from the loss of equilibrium due to persistent flux
emergence, continuous photospheric motion and strong shear along the
magnetic neutral line. The opening of the coronal field lines above
the active region should be a byproduct of the large 3B/X1.2 flare
rather than its trigger.

---------------------------------------------------------
Title: What We Have Learned about Prominences and Filaments from
SOHO/SUMER and CDS Spectral Observations
Authors: Heinzel, P.; Schmieder, B.; Vial, J. -C.
2006ESASP.617E..65H Altcode: 2006soho...17E..65H
No abstract at ADS

---------------------------------------------------------
Title: Importance of Absorption and Volume Blocking for Line Intensity
Depression in EUV Filaments
Authors: Schwartz, P.; Schmieder, B.; Heinzel, P.
2006ESASP.617E..75S Altcode: 2006soho...17E..75S
No abstract at ADS

---------------------------------------------------------
Title: Magnetic Sources of Flares and CMEs from Multi-Wavelength
Flare Studies
Authors: Schmieder, B.; Mandrini, C.; Berlicki, A.; Démoulin, P.;
Li, H.
2006ESASP.617E.145S Altcode: 2006soho...17E.145S
No abstract at ADS

---------------------------------------------------------
Title: New perspectives on prominences as observed by SOHO/SUMER
Authors: Schmieder, B.; Vial, J. -C.; Heinzel, P.
2006sf2a.conf..563S Altcode:
We summarize the results of our prominence and filament studies
based on extensive spectral observations with SOHO/SUMER and CDS
instruments. During the past decade we have gathered several sets
of UV and EUV spectral data, containing various emission lines of
different species. Our main objective was to better understand the
formation of hydrogen Lyman lines and continuum (using the results
of complex non-LTE transfer simulations). However we have also
analysed also UV and EUV lines formed under transition-region and
coronal conditions. Some highlights of our studies are: reproduction
of Lyman-line profiles with partial redistribution, understanding the
role of prominence-corona interface in the formation of Lyman-line
cores, establishing the effect of the magnetic-field orientation
on the shape of Lyman lines, discovery of EUV filament extensions
(invisible in the Hα line) and their explanation, reconstruction of
a 3D topology of the filament using EUV coronal lines, temperature
diagnostics based on measurements of the hydrogen Lyman continuum,
proper explanation of a prominence darkening detected in coronal lines.

---------------------------------------------------------
Title: Magnetic Sources of flares and CMEs in October 2003
Authors: Schmieder, B.; Démoulin, P.; Berlicki, A.; Mandrini, C.;
Hui, Li
2006sf2a.conf..565S Altcode:
We present the data analysis of an observing campaign on October 2003
with the objective of understanding the onset of Coronal Mass Ejections
(CME) and solar flares. The magnetic field was observed with THEMIS
and MDI, the chromosphere with the MSDP operating on THEMIS, the EUV
images with SOHO/EIT and TRACE, the X-rays with RHESSI. Two examples
of flares will be presented: the 28 Oct 2003 X17 flare and the 20
October 2003 M1.9 flare. The magnetic field analysis of the active
regions is done using a linear-force-free field code. The X17 flare is
at the origin of a halo CME while the M1.9 flare has no corresponding
CME. Before the X17 flare there was a pre-flare event which allowed
to change the connectivities in a first phase and to destabilize the
stressed field in a second phase producing the X17 flare. A compact
twisted emerging flux was responsible of the M1.9 flare, which remains
a compact flare due to very tied overlaying loops. These two examples
illustrate the major role of the magnetic configuration involved on
the flare physical characteristics.

---------------------------------------------------------
Title: A Multi-Wavelength Study of the Compact M1 Flare on October
22, 2002
Authors: Zanna, G. Del; Berlicki, A.; Schmieder, B.; Mason, H. E.
2006SoPh..234...95Z Altcode:
In this paper we present a further study of the Ml class
flare observed on October 22, 2002. We focus on the SOHO Coronal
Diagnostic Spectrometer (CDS) spectral observations performed during a
multi-wavelength campaign with TRACE and ground-based instruments (VTT,
THEMIS). Strong blue-shifts are observed in the CDS coronal lines in
flare kernels during the impulsive phase of this flare. From a careful
wavelength calibration we deduce upflows of 140 km/s for the Fe XIX
flare emission, with a pattern of progressively smaller flows at lower
temperatures. Large line-widths were observed, especially for the Fe XIX
line, which indicate the existence of turbulent velocities. The strong
upflows correspond to full shifts of the line profiles. These flows
are observed at the initial phase of the flare, and correspond to the
"explosive evaporation". The regions of the blueshifted kernels, a few
arc seconds away from the flare onset location, could be explained by
the chain reaction of successive magnetic reconnections of growing
emerging field line with higher and higher overlying field. This
interpretation is evidenced by the analysis of the magnetic topology
of the active region using a linear force-free-field extrapolation of
THEMIS magnetograms.

---------------------------------------------------------
Title: A Multi-Wavelength Study of the Compact M1 Flare on October
22, 2002
Authors: del Zanna, G.; Berlicki, A.; Schmieder, B.; Mason, H. E.
2006SoPh..234...95D Altcode: 2006SoPh..234...95Z
In this paper we present a further study of the Ml class
flare observed on October 22, 2002. We focus on the SOHO Coronal
Diagnostic Spectrometer (CDS) spectral observations performed during a
multi-wavelength campaign with TRACE and ground-based instruments (VTT,
THEMIS). Strong blue-shifts are observed in the CDS coronal lines in
flare kernels during the impulsive phase of this flare. From a careful
wavelength calibration we deduce upflows of 140 km/s for the Fe XIX
flare emission, with a pattern of progressively smaller flows at lower
temperatures. Large line-widths were observed, especially for the Fe
XIX line, which indicate the existence of turbulent velocities. The
strong upflows correspond to full shifts of the line profiles. These
flows are observed at the initial phase of the flare, and correspond
to the “explosive evaporation”. The regions of the blueshifted
kernels, a few arc seconds away from the flare onset location, could be
explained by the chain reaction of successive magnetic reconnections of
growing emerging field line with higher and higher overlying field. This
interpretation is evidenced by the analysis of the magnetic topology
of the active region using a linear force-free-field extrapolation of
THEMIS magnetograms.

---------------------------------------------------------
Title: IHY Science and Organization in Europe
Authors: Bougeret, J. -L.; Briand, C.; Bonet Navaro, J. A.; Breen,
A.; Candidi, M.; Georgevia, K.; Harrison, R.; Marsden, R.; Schmieder,
B.; von Steiger, R.
2006cosp...36.3226B Altcode: 2006cosp.meet.3226B
We present the scientific and organizational approach to the
International Heliophysical Year in Europe A summary is given of the
First European General Assembly of the IHY that was held in Paris in
January 2006 Initiatives and expected returns are described

---------------------------------------------------------
Title: THEMIS/MSDP magnetic field measurements
Authors: Berlicki, A.; Mein, P.; Schmieder, B.
2006A&A...445.1127B Altcode:
We present an analysis of longitudinal magnetic field measurements
using the spectral data obtained with the French - Italian
polarisation free telescope THEMIS working in Multichannel Subtractive
Double Pass (MSDP) mode. We also used SOHO/MDI data to extend our
analysis. THEMIS observations in the MSDP mode allows us to perform
imaging spectropolarimetry characterized by high spatial and time
resolution. In our analysis we used the observations of solar active
region NOAA 10484 performed on October 20, 2003. From THEMIS 2D
spectral images recorded in Na D1 5896 Å line we obtained
the longitudinal magnetic field in the active region. The value of
the magnetic field was calculated at different distances from the
Na D1 line centre. We determine the LOS magnetic field at
different heights in the solar atmosphere. SOHO/MDI observations provide
the longitudinal magnetic field in Ni I (6768 Å) line. THEMIS/MSDP
measurements at Δλ= 0.30 Å are similar to SOHO/MDI results. Gradients
of longitudinal magnetic fields derived from MSDP measurements at Δλ=
0.08 and Δλ=0.24 Å exhibit different behaviours according to solar
targets. A decrease with height is seen in spot umbrae and penumbrae,
while the gradient in facular and network areas suggests a slight
increase of the longitudinal magnetic field, which might be explained
by the 3D-structure of canopies.

---------------------------------------------------------
Title: Magnetic Topology before a 3B/X1.2 Flare and the Associated CME
Authors: Li, H.; Schmieder, B.; Aulanier, G.; Berlicki, A.
2006IAUS..233..399L Altcode:
We extrapolated observed photospheric magnetic field before the 3B/X1.2
flare occurred in NOAA 10486 on 2003 October 26. Two magnetic null
points exist above the active region, which have no crucial role in
triggering the flare, even though enhanced TRACE EUV/UV emission was
observed before the main flare due to magnetic reconnection near the
lower-altitude null point. We conclude that this flare results from the
loss of equilibrium due to persistent flux emergence and photospheric
motion, and strong shear. The accompanying fast CME with velocity of
∼ 800 km s^{-1} shows quick mass pickup and energy increase in the low
corona. Its kinetic energy is always larger than its potential energy.

---------------------------------------------------------
Title: Multi-wavelength Observations of the solar eruptive activity
Authors: Schmieder, Brigitte
2006IAUS..233..472S Altcode:
We review what we have learnt about flares and prominences using
multi-wavelength observations in the perspective of testing theoretical
models.

---------------------------------------------------------
Title: Magnetic reconfiguration before the X 17 Solar flare of
October 28 2003
Authors: Schmieder, B.; Mandrini, C. H.; Démoulin, P.; Pariat, E.;
Berlicki, A.; Deluca, E.
2006AdSpR..37.1313S Altcode:
An active region (AR) NOAA 10486, which produced a large number of
X-ray flares during October November 2003, was observed during a
multi-wavelength campaign with ground based and space instruments. We
focus our analysis on the observations of October 28, 2003. The
magnetic field was observed with THEMIS (Na D1) and MDI (Ni I), the
chromosphere with THEMIS (Ca II 8542 Å) and with the Meudon heliograph
in Hα, the EUV images with SOHO/EIT and TRACE. Two pre-events started
just before the major X 17 flare. One was related to localized flux
emergence and lasted until the decay phase of the X flare; while the
second one involved a large scale quadrupolar reconnection, that we
infer by modeling the AR magnetic field. Extended dimming areas across
the equator (EIT), large arcades of post-flare loops (TRACE 195 Å)
and a halo CME (LASCO) were observed consequently after the flare. We
perform an extrapolation of the magnetic field above the photosphere
using a linear force-free-field approximation that allows us to find
the connectivity among the four polarities that would be involved
in the quadrupolar reconnection event. The X 17 flare is plausibly
due to the destabilisation of a twisted flux tube, the bottom part
of this magnetic structure can be visualized by the presence of a
filament. The destabilization is caused by converging and shearing
photospheric motions towards the main magnetic inversion line. The
large scale quadrupolar reconnection related to the second pre-event
would favour the opening of the field above the twisted flux tube and,
consequently, the coronal mass ejection.

---------------------------------------------------------
Title: On the origin of the 28 October 2003 X17 event and its
companion event
Authors: Mandrini, C. H.; Demoulin, P.; Schmieder, B.; de Luca, E. E.;
Pariat, E.; Uddin, W.
2006BAAA...49..109M Altcode:
An X17 flare started at 11:01 UT on 28 October, 2003, in active region
(AR) NOAA 10486. This event was accompanied by a filament eruption
and one of the fastest coronal mass ejections (CMEs) observed during
the extreme activity period of October-November 2003. Combining
chromospheric, coronal and magnetic field data with modeling, we
concentrate in the study of two events that started before the X17
flare. One of them, which appears in UV images one hour before the major
event, is associated with localized magnetic reconnection occurring at
a magnetic mull point. T his event lasts as long as the X17 flare and
our analysis indicates that it is independent of it. The other one,
visible in Hα and UV images and simultaneous with the previous one,
is related to a large scale quadrupolar reconnection process. This
process is similar to the one proposed by the breakout model for the
initiation of CMEs, but it takes place at quasiseparatrices and not
in null points. These results will be published in Solar Physics.

---------------------------------------------------------
Title: Emergence of undulatory magnetic flux tubes by small scale
reconnections
Authors: Pariat, E.; Aulanier, G.; Schmieder, B.; Georgoulis, M. K.;
Rust, D. M.; Bernasconi, P. N.
2006AdSpR..38..902P Altcode:
With Flare Genesis Experiment (FGE), a balloon borne observatory
launched in Antarctica on January 2000, series of high spatial
resolution vector magnetograms, Dopplergrams, and Hα filtergrams
have been obtained in an emerging active region (AR 8844). Previous
analyses of this data revealed the occurence of many short-lived
and small-scale H α brightenings called 'Ellerman bombs'
(EBs) within the AR. We performed an extrapolation of the field above
the photosphere using the linear force-free field approximation. The
analysis of the magnetic topology reveals a close connexion between
the loci of EBs and the existence of "Bald patches" (BP) regions
(BPs are regions where the vector magnetic field is tangential to
the photosphere). Some of these EBs/BPs are magnetically connected
by low-lying field lines, presenting a serpentine shape. This results
leads us to conjecture that arch filament systems and active regions
coronal loops do not result from the smooth emergence of large scale
Ω-loops, but rather from the rise of flat undulatory flux tubes which
get released from their photospheric anchorage by reconnection at BPs,
which observational signature is Ellerman bombs.

---------------------------------------------------------
Title: The International Heliophysical Year in France
Authors: Schmieder, B.
2006cosp...36..978S Altcode: 2006cosp.meet..978S
We are preparing in France the anniversary of IGY 50 We are gathering
our efforts around few actions 1 We planned to follow the international
campaigns with our solar Telescope THEMIS in Tenerife with the
spacecrafts SOHO Cluster and the magnetometers of Superdarn A group
is already formed with C Hanuise as responsible to understand some
physical processes involved in these phenomena by using former data 2
On the initiative of CAWSES SCOSTEP program we plan to rehabilitate
our heliograph in Meudon in order to be able to participate to the
international network of flare survey The Japonese are leading this
program Shibata and Kurokawa 3 We are developping lectures for students
in different places in France We planned to work on the development
of a DVD and video games in a IHY European context 4 We have also an
outreach program which consists of an exhibition This exibition could
be duplicated in France and for French speaking countries

---------------------------------------------------------
Title: The role of null points in large flares
Authors: Schmieder, B.; Mandrini, C.; Démoulin, P.; Aulanier, G.;
Li, H.
2006cosp...36..156S Altcode: 2006cosp.meet..156S
We have performed the analysis of the magnetic topology of the active
region NOAA 10486 before two large flares occurring on October 26 and
28 2003 The 3D extrapolation of photospheric magnetic field show the
existence of magnetic null points We used TRACE 1600 A brightenings
as tracers of the energy release during magnetic reconnections We
conclude on the three following points 1 The observed small pre-events
observed before the flares were related to low lying null points They
were long lasting and associated with low energy release They were not
triggering of the large flares 2 On October 26 a high altitude null
point was detected We looked at the TRACE 1600 A images for bright
patches corresponding to a possible coronal reconnection at the null
point However no bright patch was observed before the main flare 3
On October 28 a breakout of the large scale overlaying magnetic field
lines occurred but without the presence of a null point in the corona
So the existence of a null point in the corona is not a sufficient
and or necessary condition for getting large flares

---------------------------------------------------------
Title: Active Region Magnetic Field Observed with Themis/msdp and
Soho/mdi Instruments
Authors: Berlicki, A.; Mein, P.; Schmieder, B.
2005ESASP.600E..57B Altcode: 2005ESPM...11...57B; 2005dysu.confE..57B
No abstract at ADS

---------------------------------------------------------
Title: Multi-Wavelength Analysis of Plasma Flows during Solar Flares
Authors: Berlicki, A.; Schmieder, B.; Heinzel, P.; Li, H.; Del Zanna,
G.; Rudawy, P.
2005ESASP.600E..58B Altcode: 2005dysu.confE..58B; 2005ESPM...11...58B
No abstract at ADS

---------------------------------------------------------
Title: A Multi-Wavelength Study of the 3B/X1.2 Flare Observed on
2003 October 26
Authors: Li, Hui; Li, Jian-Ping; Fang, Cheng; Schmieder, Brigitte;
Berlicki, Arkadiusz; Du, Qiu-Sheng
2005ChJAA...5..645L Altcode:
We report results from a multi-wavelength study of the 3B/X1.2
two-ribbon disk flare (S15E44), which was well observed by both
ground-based and space-borne instruments. Two pairs of conjugate kernels
K1 and K4, and K2 and K3 in the Hα images are identified. These kernels
are linked by two different systems of EUV loops. K1 and K4 correspond
to the two 17 GHz and 34 GHz microwave sources observed by the Nobeyama
Radioheliograph (NoRH), while K2 and K3 have no corresponding microwave
sources. Optical spectroscopic observations suggest that all the four
kernels are possible precipitating sites of non-thermal electrons. Thus
the energy of electron deposited in K2 and K3 should be less than 100
keV. Two-dimensional distributions of the full widths at half maximum
(FWHM) of the Hα profiles and the line-of-sight (LOS) velocities
derived from the Ca II 8542 Å profiles indicate that the largest
FWHM and LOS velocity tends to be located near the outer edges of Hα
kernels, which is consistent with the scenario of current two-ribbon
flare models and previous results. When non-thermal electron bombardment
is present, the observed Hα and Ca II 8542 Å profiles are similar to
previous observational and theoretical results, while the He I 10830
Å profiles are different from the theoretical ones. This puts some
constraints on future theoretical calculation of the He I 10830 Å line.

---------------------------------------------------------
Title: Non-Lte Modelling of the EUV Filament Based on Soho/sumer
Observations of the Hydrogen Lyman Lines
Authors: Schwartz, P.; Heinzel, P.; Schmieder, B.
2005ESASP.600E..97S Altcode: 2005dysu.confE..97S; 2005ESPM...11...97S
No abstract at ADS

---------------------------------------------------------
Title: Observation of Small Scale Reconnection Role in Undulated
Flux Tube Emergence
Authors: Pariat, E.; Aulanier, G.; Schmieder, B.; Georgoulis, M. K.;
Rust, D. M.; Bernasconi, P. N.
2005ESASP.596E..34P Altcode: 2005ccmf.confE..34P
No abstract at ADS

---------------------------------------------------------
Title: Observational Evidence of Photoshperic Magnetic Dips in
Filament Channels
Authors: Schmieder, B.; López Ariste, A.; Aulanier, G.
2005ESASP.596E..19S Altcode: 2005ccmf.confE..19S
No abstract at ADS

---------------------------------------------------------
Title: Flows and Heating of the Solar Atmosphere during Solar Flares
Authors: Schmieder, B.; Berlicki, A.; Li, H.; Del Zanna, G.; Mason, H.
2005ESASP.592..543S Altcode: 2005soho...16E.102S; 2005ESASP.592E.102S
No abstract at ADS

---------------------------------------------------------
Title: Thermal and non-thermal effects driven by magnetic
reconnections observed in a confined flare
Authors: Li, H.; Berlicki, A.; Schmieder, B.
2005A&A...438..325L Altcode:
In order to better understand the energy processes occurring during
the impulsive phase of solar flares we compare observations with our
magnetic model calculations. We study the 1N/M1.9 confined flare of
20 October 2003 observed during a Joint Observation Program (JOP157),
and concentrate on the spectral analysis of the Reuven Ramaty High
Energy Solar Spectroscopic Imager (RHESSI). These X-ray observations
are combined with those from the Solar and Heliospheric Observatory
(SOHO) instruments, the French Italian magnetograph (THEMIS), and the
Multi-channel Infrared Solar Spectrograph (MISS). The flare occurred
in a complex active region, NOAA 10484, with a δ configuration. For
model calculations we extrapolate magnetic field lines, which allows
us to understand the magnetic topology of the region. This topology
and the long impulsive phase of the flare with numerous peaks (GOES,
RHESSI) suggest multiple magnetic field reconnection processes. The
RHESSI images show a bright structure in hard X-rays (HXR) that could
be the tops of the loops. We measure a significant displacement
of this structure between the two main maxima of emission, which
infers different sites for the reconnection process. The energy
release processes can be understood by analyzing the RHESSI spectra
using different models. First, using the thermal plus broken power law
non-thermal component, we derive the low energy cutoff for the power law
distribution of the high-energy electrons (≈25 keV). Then, we apply
two models (thermal plus thick-target and thermal plus thin-target
non-thermal component) that allow us to fit the observations. These
two models lead to similar results; non-thermal energy contributes a
significant amount (approximately 20%) of the total flare energy only
during the first peak of the impulsive phase. This suggests that the
energy that heats the chromosphere is transported mainly by thermal
conduction. The temperature of the thermal plasma is 34 MK and 20 MK
at the first and second peaks, respectively.

---------------------------------------------------------
Title: Non-LTE diagnostics of velocity fields during the gradual
phase of a solar flare
Authors: Berlicki, A.; Heinzel, P.; Schmieder, B.; Mein, P.; Mein, N.
2005A&A...430..679B Altcode:
We perform an analysis of the velocity field within the Hα ribbons
during the gradual phase of an M 1.0 solar flare observed on October 22,
2002. We use spectroscopic observations performed with the German VTT
(Vacuum Tower Telescope) working in the MSDP (Multichannel Subtractive
Double Pass spectrograph) observing mode. From these observations
the Hα line profiles in chosen areas of the flare ribbons were
reconstructed and these observational profiles were compared with
a grid of synthetic Hα line profiles calculated by the non-LTE
radiative-transfer code. This code allows us to calculate different
models of the chromosphere with a prescribed velocity field. By
optimising the best fit between the observed and synthetic profiles
we find the most appropriate models of the chromosphere and vertical
structure of the velocity field in the analysed areas of the flare
ribbons. By means of the non-LTE radiative-transfer calculations
we show that in most analysed areas of the Hα flare ribbons the
chromospheric plasma exhibited upward motion with a mean velocity of
a few km;s-1. These results are consistent with previous
estimates and support the scenario of a gentle evaporation during the
gradual phase.

---------------------------------------------------------
Title: Source Regions of Coronal Mass Ejections
Authors: Schmieder, Brigitte; van Driel-Gesztelyi, L.
2005IAUS..226..149S Altcode:
The majority of flare activity arises in active regions which
contain sunspots, while CME activity can also originate from decaying
active regions and even so-called quiet solar regions which contain a
filament. Two classes of CME, namely flare-related CME events and CMEs
associated with filament eruption are well reflected in the evolution
of active regions, flare related CMEs mainly occur in young active
regions containing sunspots and as the magnetic flux of active region
is getting dispersed, the filament-eruption related CMEs will become
dominant. This is confirmed by statistical analyses.&lt;/p&gt;All the
CMEs are, nevertheless, caused by loss of equilibrium of the magnetic
structure. With observational examples we show that the association
of CME, flare and filament eruption depends on the characteristics
of the source regions: (i) the strength of the magnetic field, the
amount of possible free energy storage, (ii) the small- and large-scale
magnetic topology of the source region as well as its evolution (new
flux emergence, photospheric motions, canceling flux), and (iii) the
mass loading of the configuration (effect of gravity). These examples
are discussed in the framework of theoretical models.

---------------------------------------------------------
Title: Flux tube emergence, from photosphere to corona
Authors: Pariat, E.; Schmieder, B.; Aulanier, G.
2004sf2a.conf..103P Altcode: 2004sf2a.confE.339P
From a campaign of multi-wavelength observations of an emerging active
region, we have studied the dynamics of the solar atmosphere due to
this emergence and the magnetic field topology of the active region. In
addition with the observations obtained with Yohkoh, SOHO and TRACE,
a balloon borne 80 cm telescope (Flare Genesis Experiment) provided us
a series of high spatial resolution vector magnetograms. For the first
time we highlight that magnetic flux tubes do not directly emerge with
a large Omega-loop shape, as suggest the TRACE observations of the
corona, but rather within an undulatory shape. We demonstrated that
the resistive Parker instability allows the flux tube to go through
the low atmosphere. This result has been obtained by performing
an extrapolation of the field above the active region.

---------------------------------------------------------
Title: Resistive Emergence of Undulatory Flux Tubes
Authors: Pariat, E.; Aulanier, G.; Schmieder, B.; Georgoulis, M. K.;
Rust, D. M.; Bernasconi, P. N.
2004ApJ...614.1099P Altcode:
During its 2000 January flight, the Flare Genesis Experiment observed
the gradual emergence of a bipolar active region, by recording a series
of high-resolution photospheric vector magnetograms and images in the
blue wing of the Hα line. Previous analyses of these data revealed the
occurrence of many small-scale, transient Hα brightenings identified
as Ellerman bombs (EBs). They occur during the flux emergence,
and many of them are located near moving magnetic dipoles in which
the vector magnetic field is nearly tangential to the photosphere. A
linear force-free field extrapolation of one of the magnetograms was
performed to study the magnetic topology of small-scale EBs and their
possible role in the flux emergence process. We found that 23 out of 47
EBs are cospatial with bald patches (BPs), while 15 are located at the
footpoints of very flat separatrix field lines passing through distant
BPs. We conclude that EBs can be due to magnetic reconnection, not only
at BP locations, but also along their separatrices, occurring in the
low chromosphere. The topological analysis reveals, for the first time,
that many EBs and BPs are linked by a hierarchy of elongated flux tubes
showing aperiodic spatial undulations, whose wavelengths are typically
above the threshold of the Parker instability. These findings suggest
that arch filament systems and coronal loops do not result from the
smooth emergence of large-scale Ω-loops from below the photosphere,
but rather from the rise of undulatory flux tubes whose upper parts
emerge because of the Parker instability and whose dipped lower parts
emerge because of magnetic reconnection. EBs are then the signature
of this resistive emergence of undulatory flux tubes.

---------------------------------------------------------
Title: Evolution and magnetic topology of the M 1.0 flare of October
22, 2002
Authors: Berlicki, A.; Schmieder, B.; Vilmer, N.; Aulanier, G.;
Del Zanna, G.
2004A&A...423.1119B Altcode:
In this paper we analyse an M 1.0 confined flare observed mainly
during its gradual phase. We use the data taken during a coordinated
observational campaign between ground based instruments (THEMIS and
VTT) and space observatories (SoHO/CDS and MDI, TRACE and RHESSI). We
use these multi-wavelength observations to study the morphology
and evolution of the flare, to analyse its gradual phase and to
understand the role of various heating mechanisms. During the flare,
RHESSI observed emission only within the 3-25 keV spectral range. The
RHESSI spectra indicate that the emission of the flare was mainly of
thermal origin with a small non-thermal component observed between
10 and 20 keV. Nevertheless, the energy contained in the non-thermal
electrons is negligible compared to the thermal energy of the flaring
plasma. The temperature of plasma obtained from the fitting of the
RHESSI X-ray spectra was between 8.5 and 14 MK. The lower temperature
limit is typical for a plasma contained in post flare loops observed
in X-rays. Higher temperatures were observed during a secondary peak
of emission corresponding to a small impulsive event. The SoHO/CDS
observations performed in EUV Fe XIX line also confirm the presence
of a hot plasma at temperatures similar to those obtained from RHESSI
spectra. The EUV structures were located at the same place as RHESSI
X-ray emission. The magnetic topology analysis of the AR coming from a
linear force-free field extrapolation explains the observed features
of the gradual phase of the flare i.e. the asymmetry of the ribbons
and their fast propagation. The combination of the multi-wavelength
observations with the magnetic model further suggests that the onset
of the flare would be due to the reconnection of an emerging flux in
a sheared magnetic configuration.

---------------------------------------------------------
Title: Magnetic changes observed in the formation of two filaments
in a complex active region: TRACE and MSDP observations
Authors: Schmieder, Brigitte; Mein, Nicole; Deng, Yuanyong; Dumitrache,
Cristiana; Malherbe, Jean-Marie; Staiger, Joachim; Deluca, E. E.
2004SoPh..223..119S Altcode:
This paper is focused on the formation of two filaments in a complex
center of decaying active regions (AR 8329 and AR 8326), located in
the northern hemisphere. The observations were obtained in Hα by
the Multi-channel Subtractive Double Pass spectrograph (MSDP mounted
on the German telescope VTT in Tenerife) and EUV lines with TRACE
(Transition Region And Corona Explorer). High Doppler shifts are found
to be related to the ends of filament segments where canceling magnetic
fields are also located (as seen on magnetograms from Big Bear Solar
Observatory). At these locations, velocities along the line of sight,
derived by using a cloud model method reach −20 km s−1,
the segments of filaments merge and frequently a time-related sub-flare
is observed by TRACE. The chirality of the filament segments has been
determined by different methods: the segments of dextral chirality
join together and form a long dextral filament, and a single filament
of sinistral chirality forms end to end with the dextral filament
but does not merge with it. Assuming a model of twisted flux tube for
filament material, we suggest that the dextral filament has negative
helicity and a relationship between its formation and the close by
sunspot with the same sign of helicity.

---------------------------------------------------------
Title: Determination of the 3D structure of an EUV-filament observed
by SoHO/CDS, SoHO/SUMER and VTT/MSDP
Authors: Schwartz, P.; Heinzel, P.; Anzer, U.; Schmieder, B.
2004A&A...421..323S Altcode:
Heinzel et al. (\cite{hein1}) found that filaments seem to be much
more extended in EUV spectral lines than in Hα. In this paper we
reconstruct the 3D structure of the extensions of the EUV-filament
observed on 15 October 1999 by SoHO/CDS and SoHO/SUMER. Small Hα
structures were observed by VTT/MSDP. We computed the bottom and top
heights of the EUV-filament extensions for several values of the
hydrogen Lyman-continuum optical thickness τ912 using
the spectroscopic model of Heinzel et al. (\cite{hein2}). For this
we used CDS observations of the two coronal lines Mg X 624.94 Å and
Si XII 520.60 Å. Further, we develop a new method for estimating
τ912 using the O V line measured by CDS and the O VI
measured by SUMER onboard SoHO. The latter line is used as a proxy to
deduce the intensity variations of O V underneath the filament. This
method also takes into account the presence of prominence-corona
transition regions. Resulting heights of the EUV-filament
extensions are around 15 000 km for the bottom and around 40 000 km
for the top boundaries. However, there are significant variations
around these representative values and we show that in about half
of observed pixels the Lyman-continuum absorption dominates in
the coronal-line depression, while in the other half it is the
volume blocking effect. The latter situation corresponds to a large
(larger than 30 000 km) geometrical thickness of the EUV-filament
extension. From the heights of the boundaries of the EUV-filament the
geometrical thickness can be computed and used to estimate the total
mass loading which was found to be comparable to that of typical CMEs.

---------------------------------------------------------
Title: Multi-wavelength study of a high-latitude EUV filament
Authors: Schmieder, Brigitte; Lin, Yong; Heinzel, Petr; Schwartz, Pavol
2004SoPh..221..297S Altcode:
A large filament was observed during a multi-wavelength coordinated
campaign on June 19, 1998 in the Hα line with the Swedish Vacuum Solar
Telescope (SVST) at La Palma, in the coronal lines Fe ix/x 171 Å and
Fe xi 195 Å with the Transition Region and Coronal Explorer (TRACE)
and in EUV lines with the SOHO/CDS spectrometer and the hydrogen Lyman
series with the SOHO/SUMER spectrometer. Because of its high-latitude
location, it is possible to disentangle the physical properties of the
Hα filament and the filament channel seen in EUV lines. TRACE images
point out a dark region fitting the Hα fine-structure threads and a
dark corridor (filament channel), well extended south of the magnetic
inversion line. A similar pattern is observed in the CDS EUV-line
images. The opacity of the hydrogen and helium resonance continua at
171 Å is almost two orders of magnitude lower than that at the Hi head
(912 Å) and thus similar to the opacity of the Hα line. Since we do
not see the filament channel in Hα, this would imply that it should
also be invisible in TRACE lines. Thus, the diffuse dark corridor is
interpreted as due to the coronal `volume blocking' by a cool plasma
which extends to large altitudes. Such extensions were also confirmed by
computing the heights from the projection geometry and by simulations
of the CDS and TRACE line intensities using the spectroscopic model
of EUV filaments (Heinzel, Anzer, and Schmieder, 2003). Finally,
our NLTE analysis of selected hydrogen Lyman lines observed by SUMER
also leads to a conclusion that the dark filament channel is due to
a presence of relatively cool plasma having low densities and being
distributed at altitudes reaching the Hα filament.

---------------------------------------------------------
Title: Emerging Flux and the Heating of Coronal Loops
Authors: Schmieder, B.; Rust, D. M.; Georgoulis, M. K.; Démoulin,
P.; Bernasconi, P. N.
2004ApJ...601..530S Altcode:
We use data collected by a multiwavelength campaign of observations
to describe how the fragmented, asymmetric emergence of magnetic flux
in NOAA active region 8844 triggers the dynamics in the active-region
atmosphere. Observations of various instruments on board Yohkoh, SOHO,
and TRACE complement high-resolution observations of the balloon-borne
Flare Genesis Experiment obtained on 2000 January 25. We find that
coronal loops appeared and evolved rapidly ~6+/-2 hr after the first
detection of emerging magnetic flux. In the low chromosphere, flux
emergence resulted in intense Ellerman bomb activity. Besides the
chromosphere, we find that Ellerman bombs may also heat the transition
region, which showed “moss” ~100% brighter in areas with Ellerman
bombs as compared to areas without Ellerman bombs. In the corona,
we find a spatiotemporal anticorrelation between the soft X-ray (SXT)
and the extreme ultraviolet (TRACE) loops. First, SXT loops preceded
the appearance of the TRACE loops by 30-40 minutes. Second, the TRACE
and SXT loops had different shapes and different footpoints. Third,
the SXT loops were longer and higher than the TRACE loops. We conclude
that the TRACE and the SXT loops were formed independently. TRACE loops
were mainly heated at their footpoints, while SXT loops brightened in
response to coronal magnetic reconnection. In summary, we observed a
variety of coupled activity, from the photosphere to the active-region
corona. Links between different aspects of this activity lead to
a unified picture of the evolution and the energy release in the
active region.

---------------------------------------------------------
Title: Multi-wavelength flare study and magnetic configuration
Authors: Schmieder, Brigitte; Berlicki, A.; Vilmer, N.; Aulanier,
G.; Démoulin, P.; Mein, P.; Mandrini, C.; Deluca, E.
2004IAUS..223..397S Altcode: 2005IAUS..223..397S
Recent results of two observation campaigns (October 2002 and October
2003) are presented with the objective of understanding the onset
of flares and CMEs. The magnetic field was observed with THEMIS and
MDI, the chromosphere with the MSDP operating on the German telescope
VTT and on THEMIS, the EUV images with SOHO/CDS and TRACE, the X-ray
with RHESSI. We show how important is the magnetic configuration of
the active region to produce CMEs using two examples: the October 28
2003 X 17 flare and the October 22 2002 M 1.1 flare. The X 17 flare
gave a halo CME while the M 1.1 flare has no corresponding CME. The
magnetic topology analysis of the active regions is processed with a
linear-force-free field configuration.

---------------------------------------------------------
Title: Multi-Wavelength Observations of an M1.0 Flare on 22 October
2002
Authors: Berlicki, A.; Schmieder, B.; Vilmer, N.; Mein, P.; Mein,
N.; Heinzel, P.; Staiger, J.; Deluca, E. E.
2004IAUS..219..669B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Emerging Flux and the Heating of Coronal Loops
Authors: Schmieder, B.; Démoulin, P.; Rust, D. M.; Georgoulis, M. K.;
Bernasconi, P. N.
2004IAUS..219..483S Altcode: 2003IAUS..219E..18S
We suggest that coronal loop heating is caused by dissipation of
magnetic energy as new magnetic flux emerges from the photosphere. Based
on data from a multi wavelength campaign of observations during the
flight of the Flare Genesis Experiment we describe how emergence
of flux from the photosphere appears directly to heat the corona
to 2-3 MK. Following intense heating the loops cool and become
visible through the filters of the TRACE (Transition Region and
Coronal Explorer)instrument at one million degrees. We determine the
relaxation time of the cooling and compare it withtheoretical heating
functions. The proposed mechanism is well accepted in flare loops but
we suggest that the mechanism is generally valid and helps to explain
the visibility of active region loops in transition region lines.

---------------------------------------------------------
Title: H-alpha spectral observations of the X17+ solar flare on 28
october 2003
Authors: Radziszewski, K.; Rudawy, P.; Schmieder, B.; Berlicki, A.
2004cosp...35.1248R Altcode: 2004cosp.meet.1248R
In this paper we present the results of H-alpha observations of the
giant X17+ GOES class solar flare on 28 October 2003. The observational
data were collected with the Large Coronagraph and MSDP spectrograph of
the Astronomical Observatory of Wroclaw University (Poland). During
the nearly 3.5 hours of observations we have collected 176 scans
covering the whole flaring region (200 000 x 240 000 km2). After
the standard data reduction we have obtained quasi-monochromatic 2D
images of the flare as well as H-alpha line profiles (+/-0.12 nm)
for all pixels of the images. The temporal resolution of our data
is equal to about 50 second; the spatial resolution is of the order
of 1 second of arc. In this paper we present the main properties of
the H-alpha flare: translations of the flare kernels, motion of the
matter along the arcade of the H-alpha loops, comparison of the H-alpha
structures with ones observed in UV by TRACE and SOHO as well as with
magnetograms and numerical models of the magnetic fields and emission
of the flaring kernels.

---------------------------------------------------------
Title: Emergence of undulatory magnetic flux tubes by small scale
reconnections
Authors: Pariat, E.; Aulanier, G.; Schmieder, B.; Georgoulis, M. K.;
Rust, D. M.; Bernasconi, P. N.
2004cosp...35.1482P Altcode: 2004cosp.meet.1482P
With Flare Genesis Experiment (FGE), a balloon borne observatory
launched in Antarctica on January 2000, series of high spatial
resolution vector magnetograms, Dopplergrams, and Hα filtergrams
have been obtained in an emerging active region (AR 8844). Previous
analyses of this data revealed the occurence of many short-lived and
small-scale Hα brightenings called 'Ellerman bombs' (EBs) within the
AR. We performed an extrapolation of the field above the photosphere
using the linear force-free field approximation. The analysis of the
magnetic topology reveals a close connexion between the loci of EBs
and the existence of “Bald patches” regions (BPs are regions where
the vector magnetic field is tangential to the photosphere). Among
47 identified EBs, we found that 23 are co-spatial with a BP, while
19 are located at the footpoint of very flat separatrix field lines
passing throught a distant BP. We reveal for the first time that
some of these EBs/BPs are magneticaly connected by low-lying lines,
presenting a 'sea-serpent' shape. This results leads us to conjecture
that arch filament systems and active regions coronal loops do not
result from the smooth emergence of large scale Ω loops, but rather
from the rise of flat undulatory flux tubes which get released from
their photospheric anchorage by reconnection at BPs, whose observational
signature is Ellerman bombs.

---------------------------------------------------------
Title: Flare evolution and magnetic configuration study
Authors: Berlicki, A.; Schmieder, B.; Aulanier, G.; Vilmer, N.; Yan,
Y. H.
2004cosp...35.2200B Altcode: 2004cosp.meet.2200B
We will present the analysis of M1.0 confined flare emission and
evolution in the context of the topology of the coronal magnetic
field. This flare was observed in NOAA 0162 on 22 October 2002. The
multiwavelength data were taken during a coordinated observational
campaign between ground based instruments and space observatories. The
photospheric line-of-sight magnetic field observations were obtained
with THEMIS and SOHO/MDI. We used these data to perform linear
force-free field extrapolation of magnetic field into the corona. Our
extrapolation provides an explanation of the appearance of H-alpha
flare ribbons. An elongated shape of X-ray emission observed by Reuven
Ramaty High Energy Solar Spectroscopic Imager (RHESSI) also follow
the predicted shape of extrapolated field lines. Moreover, the X-ray
emission observed by RHESSI permit to see thermal emission of coronal
loops heated probably by non-thermal electrons, accelerated during the
reconnection processes. The presence of non-thermal particles can be
deduced from RHESSI X-ray spectra reconstructed during the gradual phase
of the flare. On Huairou vector magnetograms of the AR we see that there
was strong shear between one of main negative spot and the north small
positive spot. The extrapolation with non-constant alpha force-free
field model did not obtain any loop to connect these two spots.

---------------------------------------------------------
Title: Climate and weather of the Sun-Earth system: CAWSES
Authors: Schmieder, B.; Vincent, B.; Baumjohann, W.; Ono, T.; Basu,
S.; Lean, J.
2004AdSpR..34..443S Altcode:
SCOSTEP's mission is to implement research programs in solar-terrestrial
physics that can benefit from international participation and involve
at least two of its participating ICSU bodies. Some past SCOSTEP
programs have been comprehensive in nature such that virtually all
of SCOSTEP's energy was dedicated to the implementation of one large
program. Examples of these were SCOSTEP's STEP program in 1990-1995,
the MAP program in 1982-1985, and the IMS in 1976-1979. This document
sets forth the case for a major future SCOSTEP program called CAWSES
(Climate and Weather of the Sun-Earth System), to be implemented in
the period 2004-2008.

---------------------------------------------------------
Title: Magnetic configuration reorganisation before the X 17 flare
of October28 2003
Authors: Schmieder, B.; Mandrini, C.; Demoulin, P.; Mein, P.
2004cosp...35.1528S Altcode: 2004cosp.meet.1528S
The active region NOAA 0486 was observed during a multi-wavelength
campaign with ground based and space instruments. We analyse the
magnetic configuration of the region during a pre-event, which
reorganizes the magnetic connectivities of the field lines before the
occurence of a X17 flare of October 28 2003. The magnetic field was
observed with THEMIS and MDI, the chromosphere with the MSDP operating
on on THEMIS and with the Meudon heliograph, the EUV images with
SOHO/CDS and TRACE. The X17 flare gave a halo CME while the M1.9 flare
has no corresponding CME. The magnetic field analysis of the active
regions is performed by using a linear-force-free field code. The
pre-flare event before the X17 flare change the connectivities in a
first phase and allows the stressed field to relax in a second phase
producing the X17 flare.

---------------------------------------------------------
Title: Multiwavelength determination of the density and total mass
of the EUV filament observed by SoHO/CDS, SoHO/SUMER and MSDP/VTT
Authors: Schwartz, P.; Schmieder, B.; Heinzel, P.; Anzer, U.
2004IAUS..223..219S Altcode: 2005IAUS..223..219S
It was found that filaments observed in EUV could be much more extended
than in Halpha. These extended dark structures visible in EUV are named
EUV filaments. Their parts seen only in EUV (not observable in Halpha
because of low opacity at the Halpha wavelength) are called EUV-filament
extensions (or simply EUV extensions). For the EUV filament observed
by SoHO on 15 October 1999 as northern polar crown filament, only
a few small dark structures were seen in Halpha. This suggests that
the mass of the EUV extension is larger than, or at least comparable
with, the mass of the parts of the filament observed in Halpha. In
our previous work we determined the 3D structure of the EUV extension
of this EUV filament. In this paper we present the determinations of
mass and average density of this EUV extension. For better density
estimates we interpret the hydrogen Lyman lines observed by SUMER
using non-LTE radiative transfer code. From the best fitting of Lyman
lines we obtained a reasonable model of the EUV extension with low gas
pressure, temperatures from 2times10^4 K to 10^5 K and with extended
prominence-corona transition regions.

---------------------------------------------------------
Title: Climate and weather of the Sun Earth system: CAWSES
Authors: Schmieder, B.; Basu, S.
2003ESASP.535..701S Altcode: 2003iscs.symp..701S
During 2004-2008, CAWSES (Climate and Weather of the Sun-Earth System),
SCOSTEP's new international scientific program, will link the world's
scientists in a cooperative effort to study the entire interactive
Sun-Earth system. This new program seeks to mobilize the international
solar-terrestrial science community to fully utilize past, present and
future data; to produce improvements in space weather forcasting, design
of space- and Earth-based technological systems, and understanding
the role of solar-terrestrial influence on Global Change. The CAWSES
Science Steering Group with its 7 members (chairman: S. Basu) has
organized around four themes: Solar Influence on Climate (chairman:
M. Lockwood) Space Weather: Science and applications (chairmen:
J. Kozyra, T. Shibata) Atmospheric Coupling Processes (chairman:
F. J. Luebken) Space Climatology (chairman: C. Frohlich). A forum
is open on the web site for all comments and discussions about the
different projects of CAWSES.

---------------------------------------------------------
Title: A Spectroscopic Model of euv Filaments
Authors: Heinzel, P.; Anzer, U.; Schmieder, B.
2003SoPh..216..159H Altcode:
We propose a new spectroscopic model for extended dark structures
around Hα filaments observed in EUV lines. As in previous papers,
we call these structures EUV filaments. Our model uses at least three
observed EUV lines (located shortward the hydrogen Lyman-continuum
limit) to compute iteratively the altitudes at which the EUV filament
extensions are located. A transition-region line (O v in the present
case) can be used to derive the opacity of the Lyman continuum and the
other two coronal lines (e.g., Mg x and Si xii) then give two heights:
the bottom and top of the EUV filament. The method takes into account
self-consistently the absorption of EUV-line radiation by the Lyman
continuum, as well as the volume-blocking effect potentially important
for coronal lines. As an example we compute the heights of the EUV
filament at one particular position, using CDS data for the 5 May 2000
filament. At this position, the EUV filament extension lies between
altitudes 28 700 and 39 000 km, so that the geometrical thickness of the
structure is 10300 km (we discuss also the sensitivity of our models
to variations of the line intensities). These heights are consistent
with the concept of twisted magnetic flux tubes, but there could be
also some influence on our results due to additional low lying cool
structures from parasitic polarities.

---------------------------------------------------------
Title: Determination of the 3D-topology of an EUV-filament observed
by SoHO/CDS SoHO/SUMER and VTT/MSDP
Authors: Schwartz, P.; Heinzel, P.; Schmieder, B.; Anzer, U.
2003ESASP.535..495S Altcode: 2003iscs.symp..495S
We have constructed a spatial model of an extended EUV-filament
observed on 15 October 1999 (polar crown N 38 deg) by SoHO/CDS. The
narrow Hα counterparts were observed by VTT/MSDP. As found in 2001,
EUV-filaments are much more extended than those parts visible in Hα. We
have computed the bottom and top heights of this EUV-filament for the
whole CDS raster for different values of the Lyman-continuum optical
thickness using CDS measurements of two coronal lines (Mg X 624.94
Å and Si XII 520.60 Å) and the model of Heinzel et al., 2003. For
the scale height of the MgX line we used the value from Fludra et
al. 1999, assuming that this line is not solar cycle and activity
dependent. We created a new method for τ912 determination
from O VI and O V line intensities. Because of the inhomogeneity in
the O V 629.37 Å line intensity distribution in the vicinitiy of
the EUV-filament it was not possible to estimate this intensity under
the filament. So we used observations made by SoHO/SUMER of the O VI
1031.91 Å line not absorbed by EUV-filament cold plasma. The knowledge
of the heights of the bottom and top boundaries of an EUV-filament
gives us the EUV-filament geometrical thickness. From this the mass
of the EUV-filament was computed.

---------------------------------------------------------
Title: Foreword (Solar variability as an input to the Earth's
environment)
Authors: Wu, T.; Obridko, V.; Schmieder, B.; Sykora, J.
2003ESASP.535D..17W Altcode: 2003iscs.sympD..17W
No abstract at ADS

---------------------------------------------------------
Title: EUV-filaments and their mass loading
Authors: Heinzel, P.; Anzer, U.; Schmieder, B.; Schwartz, P.
2003ESASP.535..447H Altcode: 2003iscs.symp..447H
It was found recently (Heinzel et al., 2001; Schmieder et al., 2003)
that solar filaments observed in EUV lines by SOHO/CDS are much more
extended than their Hα counterparts. This was explained by a large
difference between the hydrogen Lyman-continuum and Hα opacities. Two
different MHD models were suggested to explain the EUV-filament
extensions: the model based on parasitic polarities (Aulanier &amp;
Schmieder, 2002) and the model with twisted flux tubes (Anzer &amp;
Heinzel, 2003). The latter model can explain our recent findings
that at least some parts of the EUV-filament extensions are located
relatively high in the corona. These heights can be computed using a
new spectroscopic model of EUV-filaments. The mass which is loaded into
the EUV-filament extensions is then estimated on the basis of non-LTE
transfer calculation. The total filament mass is larger than that
derived for the Hα filament itself and this may have consequences
for the structure and mass loading of CMEs whenever they form from
such filaments - this may answer the question how the extended CME
structures can form from rather narrow Hα filaments. We summarize
the basic properties of EUV-filaments, present their spectroscopic
analysis and give some estimates for mass loading. We then discuss
possible relations between EUV-filaments and CMEs, in particular the
problems of their masses.

---------------------------------------------------------
Title: Spectroscopic diagnostics of an Hα and EUV filament observed
with THEMIS and SOHO
Authors: Schmieder, B.; Tziotziou, K.; Heinzel, P.
2003A&A...401..361S Altcode:
A long filament has been observed with THEMIS/MSDP and SOHO/CDS -
SUMER, during a coordinated campaign (JOPs 131/95) on May 5, 2000. The
data were (a) 2-D Hα spectra, observed using THEMIS, (b) Lyman series
spectra and Lyman continuum, observed using SOHO/SUMER, and (c) EUV
spectra (in O V 629 Å, Mg X 624 Å, Si Xii 520 Å, Ca X 557 Å and
He I 584 Å) observed using SOHO/CDS. A large depression of the line
emissions in CDS images represents the EUV filament. A computed model
shows that the EUV filament consists of an extended in height cloud of
low gas pressure at an altitude lower than the top of the Hα filament,
volume-blocking and absorbing coronal emission and absorbing transition
region line emission. The optical thickness of the Lyman continuum is
estimated by using the ratio of O V intensity inside and outside the
EUV filament, while the optical thickness of Hα is computed from the
Hα line profile by using an inversion technique. Using simultaneous
Hα , Lyman lines and Lyman continuum spectroscopic data, we performed
detailed, non-LTE radiative transfer diagnostics of the filament plasma
conditions. The optical thickness of the Lyman continuum is larger than
that of the Hα line by one to two orders of magnitude. This could be
of a great importance for filament formation modeling, if we consider
that more cool material exists in filament channels but is optically
too thin to be visible in Hα images.

---------------------------------------------------------
Title: What can we learn from lfff magnetic extrapolations
Authors: Schmieder, B.; Aulanier, G.
2003AdSpR..32.1875S Altcode:
Observations of the Sun is done, up to now, in 2D and magnetic field is
measured mainly in the photosphere. Magnetic extrapolation techniques
allow us nevertheless to have a 3D view of the magnetic field. Different
methods are available today. We present in this paper interesting
and exploitable results obtained with linear force-free-field methods
(lfff). The α parameter is assumed to be constant in the whole volume
of computations. The results concern the global potential field in the
corona (e.g. example of transequatorial loops), the magnetic topology
of flaring active regions (e.g. flares and bald patch regions), twisted
magnetic fields in filaments, and magnetic reconnection in emerging
active region (e.g. Ellerman Bombs). We discuss on the limits of the
validity of the methods.

---------------------------------------------------------
Title: Flare Genesis Experiment: magnetic topology of Ellerman bombs
Authors: Schmieder, B.; Pariat, E.; Aulanier, G.; Georgoulis, M. K.;
Rust, D. M.; Bernasconi, P. N.
2002ESASP.506..911S Altcode: 2002svco.conf..911S; 2002ESPM...10..911S
Flare Genesis Experiment (FGE), a balloon borne Observatory was launched
in Antarctica on January 10, 2000 and flew during 17 days. FGE consists
of an 80 cm Cassegrain telescope with an F/1.5 ultra-low-expansion
glass primary mirror and a crystalline silicon secondary mirror. A
helium-filled balloon carried the FGE to an altitude of 37 km
(Bernasconi et al. 2000, 2001). We select among all the observations a
set of high spatial and temporal resolution observations of an emerging
active region with numerous Ellerman bombs (EBs). Statistical and
morphology analysis have been performed. We demonstrate that Ellerman
bombs are the result of magnetic reconnection in the low chromosphere
by a magnetic topology analysis. The loci of EBs coincide with "bald
patches" (BPs). BPs are regions where the vector field is tangential to
the boundary (photosphere) along an inversion line. We conclude that
emerging flux through the photosphere is achieved through resistive
emergence of U loops connecting small Ω loops before rising in the
chromosphere and forming Arch Filament System (AFS).

---------------------------------------------------------
Title: Spectral diagnostics of the magnetic field orientation in a
round-shaped filament
Authors: Schmieder, B.; Mein, N.; Heinzel, P.; Anzer, U.
2002ESASP.506..469S Altcode: 2002ESPM...10..469S; 2002svco.conf..469S
During several campaigns focused on prominences we have obtained
coordinated spectral observations from the ground and from space. The
SOHO/SUMER spectrometer allows us to observe, among others, the whole
Lyman series of hydrogen, while the Hα line was observed by the MSDP
spectrograph at the VTT. For Lyman lines, the non-LTE radiative-transfer
computations have shown the importance of the prominence-corona
transition region (PCTR) and its relation to the magnetic field
orientation for the explanation of the observed line profiles (Schmieder
et al. 1998, Heinzel et al. 2001). Moreover, Heinzel and Anzer (2001)
developed new 2D models which demonstrate how the shapes of Lyman
lines vary depending on the orientation of the magnetic field with
respect to the line of sight. To confirm this result observationally,
we focus here on a round-shaped filament observed during three days
as it was crossing the limb. The Lyman profiles observed on the limb
are different from day to day and we interpret these differences by
the change of orientation of the prominence axis (and therefore the
magnetic field direction) with respect to the line-of-sight.

---------------------------------------------------------
Title: Statistics, morphology, and energetics of Ellerman bombs
Authors: Georgoulis, Manolis K.; Rust, David M.; Bernasconi, Pietro
N.; Schmieder, Brigitte
2002ESASP.505..125G Altcode: 2002IAUCo.188..125G; 2002solm.conf..125G
We have performed a detailed analysis of several hundreds Hα Ellerman
bombs in the low chromosphere, above an emerging flux region. We
find that Ellerman bombs may be small-scale, low-altitude, magnetic
reconnection events that heat the low chromosphere in the active
region. Their energy content varies between 1027 erg and
1028 erg, typical of sub-flaring activity.

---------------------------------------------------------
Title: Magnetic cancellation and small-scale activity in an AR
filament
Authors: Schmieder, B.; Engvold, O.; Yong, Lin; Deng, Y. Y.; Mein, N.
2002ESASP.505..223S Altcode: 2002solm.conf..223S; 2002IAUCo.188..223S
A long set of observations obtained with the VTT/MSDP spectrograph
in September 1998 (8 to 11) allows us to follow the formation of a
complex filament in and around a nest of active regions during its
disk passage. Continuous shear of magnetic field in this region can
explain the formation and the relative stability of the filament
structure before the occurrence of a flare which leads to important
changes in the magnetic configuration. The corona overlying the region
and the flare, as well, is observed by TRACE. The studied filament
is stable on long term time scale. However, high spatial and temporal
observations obtained in La Palma (SVST) show high Doppler shifts and
strong transverse motions of absorbing blobs along the filament. These
velocities are directly related to magnetic activity as observed with
the SVST. A small scale magnetic analysis shows emergence of MMFs
(Moving Magnetic Features) around a decaying sunspot and canceling flux
with the neighbor network. Magnetic reconnection could occur and explain
the ejection of blobs along the new magnetic field lines. Formation
of the transient blobs is discussed.

---------------------------------------------------------
Title: Vector magnetic field observations of flux tube emergence
Authors: Schmieder, B.; Aulanier, G.; Pariat, E.; Georgoulis, M. K.;
Rust, D. M.; Bernasconi, P. N.
2002ESASP.505..575S Altcode: 2002IAUCo.188..575S; 2002solm.conf..575S
With Flare Genesis Experiment (FGE), a balloon borne Observatory high
spatial and temporal resolution vector magnetograms have been obtained
in an emerging active region. The comparison of the observations
(FGE and TRACE) with a linear force-free field analysis of the region
shows where the region is non-force-free. An analysis of the magnetic
topology furnishes insights into the existence of "bald patches"
regions (BPs are regions where the vector field is tangential to the
boundary (photosphere) along an inversion line). Magnetic reconnection
is possible and local heating of the chromopshere is predicted near the
BPs. Ellerman bombs (EBs) were found to coincide with few BPs computed
from a linear force-free extrapolation of the observed longitudinal
field. But when the actual observations of transverse fields were used
to identify BPs, then the correspondence with EB positions improved
significantly. We conclude that linear force-free extrapolations must
be done with the true observed vertical fields, which require the
measurement of the three components of the magnetic field.

---------------------------------------------------------
Title: Filament activation and magnetic reconnection
Authors: Deng, Yuanyong; Lin, Yong; Schmieder, Brigitte; Engvold,
OddbjØrn
2002SoPh..209..153D Altcode:
A curved filament in a decaying active region (AR 8329) was observed
on 9 September 1998 with a combination of several instruments. The
main data base is a 4-hour long time series of 1 min cadence using the
Lockheed tunable filter mounted in the Swedish Vacuum Solar Tower in
La Palma (SVST). Filtergrams obtained at several wavelength positions
in Hα images are used to derive Doppler images. Interleaved images
in the magnetic sensitive Fe i 6302.5 Å line yield corresponding
magnetograms. Supplementing observations are collected from TRACE and
the French Multi-Channel Double Pass spectrograph (MSDP) mounted in
the German VTT in Tenerife. The filament, which consists of several
discrete fragments with nearly horizontal fine structures, undergoes
activity and counter-streaming bulk flow, but without erupting. The
magnetic field inversion line of this active region is complex and
strongly influenced by intrusion of a positive polarity area in a
following negative polarity of the region. The positive polarity
area contains a small sunspot surrounded by moving magnetic features
(MMFs). The MMFs interact directly with the parasitic polarities in
the filament channel, and thereby gives rise to merging and canceling
magnetic flux. When the interaction occurs at the location of the feet
(`barbs') of the filament notable activations are observed (ejection of
`blobs'). The ejections of `blobs' are preceded by twist of filament
threads and the `blobs' move along downward bending field lines towards
the photosphere close to the sound speed.

---------------------------------------------------------
Title: The Structure and Evolution of a Sigmoidal Active Region
Authors: Gibson, S. E.; Fletcher, L.; Del Zanna, G.; Pike, C. D.;
Mason, H. E.; Mandrini, C. H.; Démoulin, P.; Gilbert, H.; Burkepile,
J.; Holzer, T.; Alexander, D.; Liu, Y.; Nitta, N.; Qiu, J.; Schmieder,
B.; Thompson, B. J.
2002ApJ...574.1021G Altcode:
Solar coronal sigmoidal active regions have been shown to be precursors
to some coronal mass ejections. Sigmoids, or S-shaped structures,
may be indicators of twisted or helical magnetic structures, having
an increased likelihood of eruption. We present here an analysis of a
sigmoidal region's three-dimensional structure and how it evolves in
relation to its eruptive dynamics. We use data taken during a recent
study of a sigmoidal active region passing across the solar disk
(an element of the third Whole Sun Month campaign). While S-shaped
structures are generally observed in soft X-ray (SXR) emission, the
observations that we present demonstrate their visibility at a range of
wavelengths including those showing an associated sigmoidal filament. We
examine the relationship between the S-shaped structures seen in SXR
and those seen in cooler lines in order to probe the sigmoidal region's
three-dimensional density and temperature structure. We also consider
magnetic field observations and extrapolations in relation to these
coronal structures. We present an interpretation of the disk passage
of the sigmoidal region, in terms of a twisted magnetic flux rope
that emerges into and equilibrates with overlying coronal magnetic
field structures, which explains many of the key observed aspects of
the region's structure and evolution. In particular, the evolving flux
rope interpretation provides insight into why and how the region moves
between active and quiescent phases, how the region's sigmoidicity is
maintained during its evolution, and under what circumstances sigmoidal
structures are apparent at a range of wavelengths.

---------------------------------------------------------
Title: The role of magnetic bald patches in surges and arch filament
systems
Authors: Mandrini, C. H.; Démoulin, P.; Schmieder, B.; Deng, Y. Y.;
Rudawy, P.
2002A&A...391..317M Altcode:
The short-lived active region (AR) NOAA 7968 was thoroughly observed
all along its disk transit (June 3 to 10, 1996) from space and from
the ground. During the early stage of its evolution, flux emerged in
between the two main polarities and arch filament systems (AFS) were
observed to be linked to this emergence. New bipoles and a related surge
were observed on June 9. We have modeled the magnetic configuration
of AR 7968 using a magnetohydrostatic approach and we have analyzed
its topology on June 6 and June 9 in detail. We have found that some
of the AFS and the surge were associated with field lines having dips
tangent to the photosphere (the so called “bald patches”, BPs). Two
interacting BP separatrices, defining a separator, have been identified
in the configuration where these very different events occurred. The
observed evolution of the AFS and the surge is consistent with the
expected results of magnetic reconnection occuring in this magnetic
topology, which is specific to 3D configurations. Previously BPs have
been found to be related to filament feet, small flares and transition
region brightenings. Our results are evidence of the importance of
BPs in a much wider range of phenomena, and show that current layers
can be formed and efficiently dissipated in the chromosphere.

---------------------------------------------------------
Title: Statistics, Morphology, and Energetics of Ellerman Bombs
Authors: Georgoulis, Manolis K.; Rust, David M.; Bernasconi, Pietro
N.; Schmieder, Brigitte
2002ApJ...575..506G Altcode:
We investigate the statistical properties of Ellerman bombs in the
dynamic emerging flux region NOAA Active Region 8844, underneath
an expanding arch filament system. High-resolution chromospheric
Hα filtergrams (spatial resolution 0.8"), as well as photospheric
vector magnetograms (spatial resolution 0.5") and Dopplergrams, have
been acquired by the balloon-borne Flare Genesis Experiment. Hα
observations reveal the first “seeing-free” data set on Ellerman
bombs and one of the largest samples of these events. We find that
Ellerman bombs occur and recur in preferential locations in the low
chromosphere, either above or in the absence of photospheric neutral
magnetic lines. Ellerman bombs are associated with photospheric
downflows, and their loci follow the transverse mass flows on the
photosphere. They are small-scale events, with typical size 1.8"×1.1"
, but this size depends on the instrumental resolution. A large number
of Ellerman bombs are probably undetected, owing to limited spatial
resolution. Ellerman bombs occur in clusters that exhibit fractal
properties. The fractal dimension, with an average value ~1.4, does
not change significantly in the course of time. Typical parameters
of Ellerman bombs are interrelated and obey power-law distribution
functions, as in the case of flaring and subflaring activity. We find
that Ellerman bombs may occur on separatrix, or quasi-separatrix,
layers, in the low chromosphere. A plausible triggering mechanism
of Ellerman bombs is stochastic magnetic reconnection caused by the
turbulent evolution of the low-lying magnetic fields and the continuous
reshaping of separatrix layers. The total energies of Ellerman bombs
are estimated in the range (1027, 1028) ergs, the
temperature enhancement in the radiating volume is ~2×103
K, and the timescale of radiative cooling is short, of the order of
a few seconds. The distribution function of the energies of Ellerman
bombs exhibits a power-law shape with an index ~-2.1. This suggests
that Ellerman bombs may contribute significantly to the heating of
the low chromosphere in emerging flux regions.

---------------------------------------------------------
Title: Photospheric Vertical Current Density and Overlying Atmospheric
Activity in an Emerging Flux Region
Authors: Georgoulis, M. K.; Rust, D. M.; Bernasconi, P. N.;
Schmieder, B.
2002AAS...200.2004G Altcode: 2002BAAS...34..673G
Using high-resolution vector magnetograms obtained by the balloon-borne
Flare Genesis Experiment (FGE), we construct maps of the vertical
current density in the emerging flux region NOAA 8844. The vertical
current density has been decomposed into components that are
field-aligned and perpendicular to the magnetic field, thus allowing
a straightforward identification of force-free areas, as well as of
areas where the force-free approximation breaks down. Small-scale
chromospheric activity, such as H α Ellerman bombs and Ultraviolet
bright points in 1600 Åshow a remarkable correlation with areas of
strong current density. Simultaneous data of overlying coronal loops,
observed by TRACE in the Extreme Ultraviolet (171 Åand 195 Å), have
been carefully co-aligned with the FGE photospheric maps. We find
that the footpoints of the TRACE loops always coincide with strong
vertical currents and enhancements of the current helicity density. We
also investigate whether the force-free approximation is valid on the
photosphere during various evolutionary stages of the active region.

---------------------------------------------------------
Title: The magnetic nature of wide EUV filament channels and their
role in the mass loading of CMEs
Authors: Aulanier, G.; Schmieder, B.
2002A&A...386.1106A Altcode:
Previous works have shown that dark and wide EUV filament channels
observed at lambda &lt; 912 Å, are due to absorption of EUV lines in
cool plasma condensations that are not observed in Hα . We extend this
interpretation and we address the issue of the possible injection of
their mass into CMEs, through the magneto-hydrostatic modeling in 3D
of one filament observed both in Hα and in EUV. The model parameters
are fixed so as to match the Hα observations only. Further comparison
of the model with the EUV observations reveal the magnetic nature of
the absorbing plasma condensations. They are formed in magnetic dips,
as for the filament itself. Opacity ratios and the hydrostatic condition
imply that the dips must be filled by cool material up to 1700 km, which
increases the filament mass by 50% as compared to Hα estimations. Far
from the filament, the absorbing condensations are located below 4 Mm
in altitude above the photosphere, on the edge of weak photospheric
parasitic polarities, within the lower parts of long field lines
overlaying the filament. By physical analogy with Hα filament feet,
we redefined these extended regions as EUV feet. The broadening of the
EUV filament channel is dominated by EUV feet, while the larger filling
of dips plays a non-negligible but minor role. Further implications
from this work are discussed, on the visibility and the geometry of
the condensations, on the existence of EUV filament channels in the
absence of filaments, on the loading of cool material into filament feet
through bald patch reconnection and on the complex geometry of the upper
prominence-corona transition region. The magnetic topology implies that
during the filament eruption, the mass of its wide EUV feet will not
contribute to the CME, whereas the extra mass provided by the large
filling of dips in the filament flux tube will be loaded into the CME.

---------------------------------------------------------
Title: Foreword (SOLSPA 2001)
Authors: Schmieder, Brigitte; Smaldone, Luigi
2002ESASP.477D..15S Altcode: 2002scsw.confD..15S
No abstract at ADS

---------------------------------------------------------
Title: Climate and weather of the Sun-Earth system: CAWSES, SCOSTEP's
program for 2003-2008
Authors: Schmieder, B.; Vincent, B.; Baumjohann, W.; Ono, T.; Basu,
S.; Lean, L.
2002ESASP.477...59S Altcode: 2002scsw.conf...59S
SCOSTEP's mission is to implement research programs in solar-terrestrial
physics that can benefit from international participation and involve
at least two of its participating and involve at least two of its
participating ICSU bodies. Some past SCOSTEP programs have been
comprehensive in nature such that virtually all of SCOSTEP's energy
was dedicated to the implementation of one large program. Examples
of these were SCOSTEP's STEP program in 1990-95, the MAP program in
1982-85, and the IMS in 1976-79. This document sets forth the case for
a major future SCOSTEP program called CAWSES (Climate and Weather of
the Sun-Earth System), to be implemented in the period 2003-2008.

---------------------------------------------------------
Title: Magnetic build-up and precursors of CMEs
Authors: van Driel-Gesztelyi, Lidia; Schmieder, Brigitte; Poedts,
Stefaan
2002ESASP.477...47V Altcode: 2002scsw.conf...47V
CMEs are fundamentally magnetic phenomena, thus to improve CME forecast
we have to find out more about the characteristics of the small and
large-scale magnetic field in and around their source region prior
to CME occurrence. In this paper we show examples of the magnetic
evolution of CME-prolific active regions using SOHO/MDI data. It
appears that CMEs are preceded by magnetic evolution during which
the helicity of the source region is increasing due to twisted flux
emergence, shearing motions between opposite polarity footpoints
of subsequently emerging bipoles and, in a smaller extend, by the
differential rotation acting on the emerged flux. Furthermore, we find
short-term magnetic precursors of CME events, typically a combination of
major flux emergence, cancellation and fast shearing motions in active
regions with strong concentrated magnetic fields prior to flare-related
CMEs and small-scale cancellation events along the magnetic inversion
line in decayed active regions with low magnetic flux density prior to
filament eruption-related CMEs. We make an overview of recent studies
on magnetic helicity and suggest that such analyses will be able to
provide a key to unlock the secrets of CME buildup and initiation.

---------------------------------------------------------
Title: The characteristics of microwave burst source and energy
budget in disappering filament
Authors: Tang, Y. H.; Schmieder, B.; Fang, C.
2002AdSpR..29.1461T Altcode:
On 7 May, 1992 a complex event with the disappearence of a filament
and a two ribbon flare was well observed in Hα filtergrams, Yorkoh
soft X-ray data, and radio data. This event is studied by using the
flare-filament current model. The momentum equation and the energy
equation of the filament current have been solved. By using the measured
time variation of the filament height, the corresponding evolution of
the current intensity and the total energy of the current filament
were computed. The magnetic field strength and the energy flux of
energetic electrons in the source region of microwave bursts have also
been estimated by using the microwave spectrum. During the main phase,
the mean magnetic strength and the energy flux of energetic electrons
are about 300-400G and 1 × 10 11 erg cm -2s
-1, respectively. By using these physical parameters, the
energy budget has been made. These results show that the flare of 7
May, 1992 may be the result of reconnection of current sheet beneath
the disappearing filament and the flare energy is provided by current
filament.

---------------------------------------------------------
Title: Energetics of the 18 May 1994 brightening event
Authors: Tang, Y. H.; Li, Y. N.; Fang, C.; Schmieder, B.; Aulanier,
G.; Demoulin, P.
2002AdSpR..30..557T Altcode:
By using YOHKOH soft X-ray images, vector magnetograms and Hα
filtergrams, the energetics of the brightening event of May 18, 1994 has
been studied. It occurred in a nearly potential magnetic configuration
as shown by the comparison between the magnetic extrapolation(linear
force free field) and the large scale soft X-ray loops. This event
is related to the emergence of a new magnetic flux. The brightening
points of Hα and soft X-ray are located at computed separatrices
associated with field lines which are tangent to the photosphere. This
brightening may be a signature of reconnection taking place between the
pre-existing non-potential loops and the new emerging small loops. The
magnetic energy provided by reconnection is likely to be stored in
the non-potential loops and shearing emerging flux. A phenomenological
model is offered.

---------------------------------------------------------
Title: Climate and Weather of the Sun Earth system:SCOSTEP s program
for 2004- 2008
Authors: Schmieder, B.; Vincent, B.; Baumjohann, W.; Ono, T.; Basu,
S.; Lean, L.
2002cosp...34E.139S Altcode: 2002cosp.meetE.139S
Research in the past decade has produced significant improvements
in understanding the physical processes within each of the Sun-Earth
domains, and enabled crossdisciplinary progress in understanding the
domain as a whole.SCOSTEP's mission is to implement research programs
in solar-terrestrial physics that can benefit from international
participation and involve at least two of its participating ICSU
bodies. Some past SCOSTEP programs have been comprehensive in nature
such that virtually all of SCOSTEP's energy was dedicated to the
implementation of one large program. Examples of these were SCOSTEP's
STEP program in 1990-95, the MAP program in 1982-85, and the IMS in
1976-79. This document sets forth the case for a major future SCOSTEP
program called CAWSES (Climate and Weather of the Sun-Earth System),
to be implemented in the period 2004-2008. Climate implies long-term
studies

---------------------------------------------------------
Title: Surges y Arch Filament Systems: Una topología inusual
Authors: Mandrini, C. H.; Démoulin, P.; Schmieder, B.; Deng, Y. Y.;
Rudawy, P.
2002BAAA...45...17M Altcode:
Active region (AR) NOAA 7968 was observed during its solar disk transit
by several instruments on ground and on board satellites (Yohkoh and
SOHO). During its emergence Arch Filament Systems (AFS) linking the
polarities of the main bipole were observed. During its decay a surge
(a chromospheric confined mass ejection) occurred to the South of the
positive polarity of this bipole. We model the AR magnetic field in the
magnetohydrostatic approach and compute its topology. We find that the
evolution of both events, AFS and surge, agrees with magnetic field
reconnection occurring in field lines that are tangentially touching
the photosphere. These lines define the so called “bald patches”
(BPs). In previous studies these topological structures have been found
to be related to small flares and transition region brightenings. Our
results point out the importance of BPs in a wider phenomenological
context and show that current sheets can develop and efficiently
dissipate in the chromosphere.

---------------------------------------------------------
Title: What can we learn from magnetic extrapolation above active
region and filament?
Authors: Schmieder, B.; Aulanier, G.
2002cosp...34E.458S Altcode: 2002cosp.meetE.458S
Observations of the Sun is done up to now in 2D. Magnetic
extrapolation technique allows us to have a 3D view of the magnetic
field lines. Global 3D structures can be visualized by using
such computations. Assuming linear force-free-field configuration
we have analyzed different active regions and filaments. In the
lfff approximation thevalue is constant for all the field lines
and is chosen in order to give the best global or local fit to the
structures projected on the solar surface observed in H, in UV lines
(EIT, TRACE) or in X rays (Yohkoh/SXT). With some examples we will
show some important results that we have obtained: 1. the existence
of a vertical gradient of the magnetic shear above active region
with filament (Schmieder et al 1996). 2. the existence of the same
value offitting the sheared filament and the spiral structure around
a sunspot, the existence of dips in the magnetic field strength at the
location of the filament channel in an AR (Schmieder et al 1991). 3. the
validity of chirality laws with dextral/sinistral filaments and negative
/positiveparameter according to the hemisphere (Aulanier et al 1999,
2000, Aulanier and Schmieder 2002)

---------------------------------------------------------
Title: Minutes of the 33rd JOSO Board Meeting - 2001
Authors: Cauzzi, G.; Kucera, A.; Schmieder, B.
2002joso.book...15C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Climate and Weather of The Sun Earth System
Authors: Schmieder, B.; Vincent, B.; Baumjohann, W.; Ono, T.; Basu,
S.; Lean, J.
2002EGSGA..27..250S Altcode:
SCOSTEP's mission is to implement research programs in solar-terrestrial
physics that can benefit from international participation and involve
at least two of its par- ticipating ICSU bodies. Some past SCOSTEP
programs have been comprehensive in nature such that virtually all of
SCOSTEP's energy was dedicated to the implemen- tation of one large
program. Examples of these were SCOSTEP's STEP program in 1990-95,
the MAP program in 1982-85, and the IMS in 1976-79. This document
sets forth the case for a major future SCOSTEP program called CAWSES
(Climate and Weather of the Sun-Earth System), to be implemented in
the period 2003-2008.

---------------------------------------------------------
Title: Minutes of the 32nd JOSO Board Meeting - 2000
Authors: Cauzzi, G.; Kucera, A.; Schmieder, B.
2002joso.book...10C Altcode:
No abstract at ADS

---------------------------------------------------------
Title: JOSO national report 2000-2001 - France
Authors: Schmieder, B.; Mein, P.; Lemaire, P.; Pick, M.; Vilmer, N.
2002joso.book...56S Altcode:
We report on the scientific advances in solar physics in France. The
French Solar community is large split in different laboratories and
observatories. We report on specific groups (THEMIS, SOHO, Nançay).

---------------------------------------------------------
Title: Evolution of the source region of the interplanetary magnetic
cloud of 18-20 Oct. 1995
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Baranyi, T.
2002AdSpR..29.1489V Altcode:
We follow the evolution and activity of the reversed polarity AR
7912 using multi-wavelength observations. We find that the presence
of high shear increased by flux emergence led to the occurrence
of a long-duration eruptive flare on 14 October 1995, which was
manifested in the SXR corona by an arcade of expanding sigmoidal
loops. A twisted magnetic cloud was observed at 1 AU between October
18-20. We propose that it was ejected from this reversed polarity AR,
and it was associated with the expanding sigmoids.

---------------------------------------------------------
Title: Relationships between CME's and prominences
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Aulanier, G.;
Démoulin, P.; Thompson, B.; De Forest, C.; Wiik, J. E.; Saint Cyr,
C.; Vial, J. C.
2002AdSpR..29.1451S Altcode:
We have studied the erupting prominences which were associated with
coronal mass ejections during a series of campaigns involving both
spacecraft and ground-based observatories. The evolution of the
physical conditions within the prominences was established from Hα
and magnetic field observations. Particular attention ahs been paid
to the presence of mixed amgnetic polarity in the filament channel,
the evolution of the shear of the large-scale magnetic field, and
the existence of multiple magnetic inversion lines. We conclude that
reconnection of large-scale coronal magnetic fields is responsible
for both the CME and filament eruption.

---------------------------------------------------------
Title: A Relationship Between Transition Region Brightenings,
Abundances, and Magnetic Topology
Authors: Fletcher, Lyndsay; López Fuentes, Marcelo C.; Mandrini,
Cristina H.; Schmieder, Brigitte; Démoulin, Pascal; Mason, Helen E.;
Young, Peter R.; Nitta, Nariaki
2001SoPh..203..255F Altcode:
We present multi-instrument observations of active region (AR) 8048,
made between 3 June and 5 June 1997, as part of the SOHO Joint Observing
Program 33. This AR has a sigmoid-like global shape and undergoes
transient brightenings in both soft X-rays and transition region
(TR) lines. We compute a magneto-hydrostatic model of the AR magnetic
field, using as boundary condition the photospheric observations of
SOHO/MDI. The computed large-scale magnetic field lines show that the
large-scale sigmoid is formed by two sets of coronal loops. Shorter
loops, associated with the core of the SXT emission, coincide with
the loops observed in the hotter CDS lines. These loops reveal a
gradient of temperature, from 2 MK at the top to 1 MK at the ends. The
field lines most closely matching these hot loops extend along the
quasi-separatrix layers (QSLs) of the computed coronal field. The TR
brightenings observed with SOHO/CDS can also be associated with the
magnetic field topology, both QSL intersections with the photosphere,
and places where separatrices issuing from bald patches (sites where
field lines coming from the corona are tangent to the photosphere)
intersect the photosphere. There are, furthermore, suggestions that
the element abundances measured in the TR may depend on the type
of topological structure present. Typically, the TR brightenings
associated with QSLs have coronal abundances, while those associated
with BP separatrices have abundances closer to photospheric values. We
suggest that this difference is due to the location and manner in which
magnetic reconnection occurs in two different topological structures.

---------------------------------------------------------
Title: Why Are Solar Filaments More Extended in Extreme-Ultraviolet
Lines than in Hα?
Authors: Heinzel, P.; Schmieder, B.; Tziotziou, K.
2001ApJ...561L.223H Altcode:
A long solar filament was observed simultaneously in the Hα line
by THEMIS/MSDP and in selected EUV lines by the Coronal Diagnostic
Spectrometer on SOHO. Co-alignment of optical and EUV images reveals
that the dark EUV filament is much more extended than the Hα
filament. Assuming that the EUV filament represents Lyman continuum
absorption of the background EUV-line radiation, a straightforward
explanation of this effect is suggested. Based on non-LTE filament
models, we demonstrate that the ratio of the Lyman continuum to Hα
opacity can reach a factor of 50-100, and thus the EUV filament is
still well visible while the Hα line contrast diminishes below the
detection limit. This kind of interpretation leads to an important
conclusion that the cool filament material in which the Lyman continuum
absorption takes place is more abundant than one would expect from
Hα disk observations. This then may have significant consequences
on the filament structure and on formation models, as well as on mass
considerations related to coronal mass ejections.

---------------------------------------------------------
Title: A Study of Hydrogen Density in Emerging Flux Loops from
a Coordinated Transition Region and Coronal Explorer and Canary
Islands Observation Campaign
Authors: Mein, N.; Schmieder, B.; DeLuca, E. E.; Heinzel, P.; Mein,
P.; Malherbe, J. M.; Staiger, J.
2001ApJ...556..438M Altcode:
During an international ground-based campaign in the Canary Islands
coordinated with space instruments (i.e., Transition Region and Coronal
Explorer [TRACE]), we observed an active region on 1998 September
10 with high spatial and temporal resolution. New emerging flux in
the central part of the active region was observed in magnetograms
of the Swedish Vacuum Solar Telescope, La Palma. Emerging loops
(arch-filament systems [AFSs]) are well developed in Hα and Ca II
according to the observations made at the Vacuum Tower Telescope (VTT)
and THEMIS telescope in Tenerife with the Multichannel Subtractive
Double Pass (MSDP) spectrographs. The TRACE images obtained at 171
and 195 Å show low-emission regions that are easily identified as
the individual AFS. They are due to absorption by hydrogen and helium
continua in the cool filament plasma. We compare two techniques of
measuring the hydrogen density in the cool dense fibrils of AFSs. The
first method based on TRACE observations derived the neutral hydrogen
column density of the plasma absorbing coronal lines. The second one
using Hα line profiles provided by the MSDP spectrographs is based on
the cloud model. The results are consistent. We derive also electron
density values using Hα lines that are in good agreement with those
derived from the 8542 Å Ca II line observed with THEMIS (Mein et
al.). The three types of observations (TRACE, VTT, THEMIS) are well
complementary: absorption of coronal lines giving a good approximation
for the maximum value of the neutral hydrogen column density, the Hα
line giving a good determination of ne, and the 8542 Å Ca
II line a good determination of the electronic temperature.

---------------------------------------------------------
Title: Sunspot Formation from Emerging Flux Ropes - Observations
from Flare Genesis
Authors: Rust, D. M.; Bernasconi, P. N.; Georgoulis, M. K.; LaBonte,
B. J.; Schmieder, B.
2001AGUSM..SP42A09R Altcode:
From January 10 to 27, 2000, the Flare Genesis payload observed
the Sun while suspended from a balloon in the stratosphere above
Antarctica. The goal of the mission was to acquire a long time series of
high-resolution images and vector magnetograms of the solar photosphere
and chromosphere. We obtained images, magnetograms and Dopplergrams
in the magnetically sensitive Ca I line at 6122 Angstroms. Additional
simultaneous images were obtained in the wing of H-alpha. On January
25, 2000, we observed in NOAA region 8844 at N05 W30. The rapid
development of a sunspot group that apparently included a delta spot
(two polarities within one umbra). We considered a variety of models
for interpreting these observations, including a twisted flux tube,
a bipole that annihilates, a bipole that submerges, and a field
distorted by mass loading. From the vector magnetograms and Doppler
measurements, we conclude that nearly horizontal flux ropes are swept
into the developing spot where they tilt upward to contribute to the
familiar nearly vertical sunspot fields. The largest flux rope exhibited
a twisted structure, and its angle with respect to the vertical was so
great that it could be mistaken for a positive magnetic field merging
into a negative sunspot. Flare Genesis was supported by NASA grant
NAG5-8331 and by NSF grant OPP-9909167.

---------------------------------------------------------
Title: Peculiar Moving Magnetic Features Observed With the Flare
Genesis Experiment
Authors: Bernasconi, P. N.; Rust, D. M.; Georgoulis, M. K.; LaBonte,
B. J.; Schmieder, B.
2001AGUSM..SP51A02B Altcode:
With the Flare Genesis Experiment (FGE), a balloon-borne 80-cm solar
telescope, we observed the active region NOAA 8844 on January 25,
2000 for several hours. FGE was equipped with a vector polarimeter
and a lithium-niobate Fabry-Perot narrow-band filter. It recorded
time series of filtergrams, vector magnetograms, and dopplergrams
at the CaI 6122.2 Angstroms line, as well as Hα filtergrams, with a
cadence between 2.5 and 7.5 minutes. At the time of the observations
NOAA 8844 was located at approximately 5 deg N, 30 deg W. It was a new
flux emergence that first appeared on the solar disk two days before
and was still showing a very dynamic behavior. Its two main polarity
parts were rapidly moving away from each other and new magnetic flux
was constantly emerging from its center. Here we describe the structure
and behavior of peculiar small moving magnetic dipoles (called moving
magnetic features MMF's) that we observed near the trailing negative
polarity sunspot of NOAA 8844. Presentations by D. M. Rust, and by
M. K. Georgoulis at this meeting will focus on other aspects of the
same active region. The MMF's took the form of small dipoles that first
emerged into the photosphere near the center of a supergranular cell
located next to the main trailing flux concentration. They rapidly
migrated towards the spot, following the supergranular flow. The two
polarities of the little dipoles did not separate; they moved together
with same speed and in the same direction. The dipoles were oriented
parallel to their motion toward the negative spot, with the positive
polarity always leading. MMF's usually move away from sunspots, and
their orientation is the reverse of what we see here. In addition,
we noted that the dipole structure was not symmetric. The field lines
of the trailing part of the MMF's (negative polarity) were always
much more perpendicular to the local horizontal than the ones of the
leading part. The trailing part looked more compact and circular, while
the leading part was more elongated in the direction of the motion. We
conclude that we observed a new type of MMF's with a totally different
magnetic structure than previously seen. We present a possible model
that could explain their unusual structure and behavior. This work
was supported by NASA grant NAG5-8331 and NSF grant OPP-9909167.

---------------------------------------------------------
Title: SOHO/SUMER observations and analysis of the hydrogen Lyman
spectrum in solar prominences
Authors: Heinzel, P.; Schmieder, B.; Vial, J. -C.; Kotrč, P.
2001A&A...370..281H Altcode:
The complete hydrogen Lyman spectrum in several prominences has been
observed with the UV spectrometer SUMER on-board the SOHO, during
the Joint Observing Programme 107, together with other space and
ground-based observatories. Based on these observations, we are able to
demonstrate, for the first time, that there exists a large variety of
intensities and shapes of Lyman lines in different prominences and in
various parts thereof. Therefore, no “canonical” Lyman spectrum can
be considered for modelling purposes. However, we have identified at
least two representative properties of the observed spectra: in one case
(May 28, 1999 prominence) we detected high integrated intensities and
no reversals in lines higher than Lalpha . Another prominence (June 2,
1999) exhibited quite similar integrated intensities, but all lines have
rather strongly reversed profiles. This behaviour cannot be explained in
terms of standard isothermal-isobaric models and we thus consider more
general models which are in pressure equilibrium with the magnetic field
and which have significant prominence-corona transition region (PCTR)
temperature gradients. This type of model, recently suggested by Anzer
&amp; Heinzel (\cite{anhe99}), is capable of explaining strong emission
profiles without reversal. Based on extended non-LTE computations,
we suggest that quite different Lyman spectra mentioned above may
correspond to two types of PCTRs, one seen along the magnetic-field
lines (unreversed profiles) and the other one seen across the field
lines (reversed profiles). Finally, we again confirm the importance
of partial-redistribution (PRD) scattering processes for Lyman lines
in prominences. However, our analysis of new SUMER data also points
to a critical role of the PCTR in radiative transport in these lines.

---------------------------------------------------------
Title: CDS UV Brightenings Explained by Quasi-separatrices and Bald
Patches in an S-shape active region
Authors: Schmieder, B.; Démoulin, P.; Fletcher, L.; López Fuentes,
M. C.; Mandrini, C. H.; Mason, H. E.; Young, P. R.; Nitta, N.
2001IAUS..203..314S Altcode:
We present multi-instrument observations of AR 8048, made between
June 3 and June5 1997 as part of SoHO JOP033. This active region
has a sigmoid-like global shape and undergoes transient erupting
phenomena which releases the stored energy. Using a force free
field approach, we defined coronal magnetic field lines which fit
with the observations. The large-scale magnetic field lines confirms
the sigmoid characteristics of the active region. The study in 3D of
the configuration explained where and how the energy is released at
different places. The Ne VI brightenings correspond to the location
of tangent to the photosphere field lines, named "bald patch", they
are localized in the low transition region and represent feet of field
lines. The Si XII brightenings at coronal temperature are at the top
of coronal loops joining quasi-separatrices.

---------------------------------------------------------
Title: The Relationship between CMEs and Prominence Eruptions
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Delannée, C.;
Simnett, G. M.; Wiik, J. E.
2001IAUS..203..310S Altcode:
From multi-wavelength studies of eruptions of prominences observed by
Yohkoh, SoHO and ground-based observatories, we find a good correlation
between prominence eruptions and CMEs (i.e. May 1 1996, Sept 25 1996,
May 31 1997). Focusing our interest on their temporal relationship,
we observe that it is not clear that filament eruption is prior to
the CME. Nevertheless they are both signatures of destabilization of
the global coronal magnetic field. The magnetic configuration in the
corona should involve the initial presence of a twisted flux tube. The
eruption could be driven by a fast increase of the poloidal field in
the flux tube or by photospheric shearing motions of the flux tube.

---------------------------------------------------------
Title: Chromosphere
Authors: Schmieder, B.
2000eaa..bookE1993S Altcode:
The chromosphere (Greek χρωμα, color) is a gaseous shell atmosphere
surrounding the Sun, and more generally stars, with a typical thickness
of 2000 km, lying above the SOLAR PHOTOSPHERE and containing mainly
hydrogen and helium gas....

---------------------------------------------------------
Title: Initiation of CMEs: the role of magnetic twist
Authors: van Driel-Gesztelyi, L.; Manoharan, P. K.; Démoulin, P.;
Aulanier, G.; Mandrini, C. H.; Lopez-Fuentes, M.; Schmieder, B.;
Orlando, S.; Thompson, B.; Plunkett, S.
2000JASTP..62.1437V Altcode: 2000JATP...62.1437V
Recent multiwavelength observations, modelling results and
theoretical developments indicate the importance of twisted magnetic
configurations in solar active regions (ARs) in the initiation of
coronal mass ejections (CMEs). Through multiwavelength analysis of a
few representative events we make an attempt to provide constraints
for CME models. The two events presented here in detail start with
the expansion of sigmoids (S- or inverse S-shaped loops) observed in
soft X-rays. Both events (on 25 October /1994 and 14 October /1995)
occurred before the launch of the SOHO spacecraft, but indirect
evidences (i.e. signatures of an outward propagation traced up to /~20
solar radii and an associated magnetic cloud) suggest that both of them
were related to CMEs. We show evidence that sigmoids are the coronal
manifestations of twisted magnetic flux tubes, which start expanding
presumably due to a loss of equilibrium. It is noteworthy that the
analysed CMEs occurred in a complex (not simply bipolar) magnetic
environment and in all cases we found evidences of the interaction
(magnetic reconnection) with the surrounding fields. We propose a
scenario for sigmoid expansion related CME events and suggest that
twisted magnetic configurations are good candidates for being source
regions of CMEs.

---------------------------------------------------------
Title: Coronal mass ejections (CMEs) initiation: models and
observations
Authors: Wu, S. T.; Guo, W. P.; Plunkett, S. P.; Schmieder, B.;
Simnett, G. M.
2000JASTP..62.1489W Altcode: 2000JATP...62.1489W
We use three observed coronal mass ejection (CME) events and numerical
magnetohydrodynamic simulation models to illustrate three distinct CME
initiation processes: (1) streamer destabilization due to increase
of currents, via increase of axial fields, of the flux-rope, (2)
photospheric shear and (3) plasma flow induced CME. The 3 January 1998
event is used to illustrate the streamer destabilization process to
initiate a CME because the observed height-time curve indicates that
the prominence eruption proceeds the CME initiation. We interpret this
CME as being initiated because of destabilization of the streamer due
to the upward motion of the flux-rope by the additional Lorentz /(J×B)
force. On the other hand, the 22 June /1998 event shows that the CME
was launched prior to the prominence eruption. This case is modeled by
shear-induced loss-of-equilibrium. The last case is entirely different
from the previous two. The morphology of the 5 October /1996 event
does not show any relation with the filament//flux-rope. We modeled
this event by introducing a plasma flow. Using the observations and
MHD models, we conclude that the first two categories are flux-rope
driven, because the energy source, which propels the CME, is stored in
the flux-rope, and the third category is driven by an assumed plasma
flow with the effects of fast solar wind, because this CME appears at
the boundary region of a streamer and coronal hole.

---------------------------------------------------------
Title: Emergence of sheared magnetic flux tubes in an active region
observed with the SVST and TRACE
Authors: Deng, Y. Y.; Schmieder, B.; Engvold, O.; DeLuca, E.; Golub, L.
2000SoPh..195..347D Altcode:
The active region NOAA AR 8331 was a target of an international
ground-based observational campaign in the Canaries and coordinated
with space instruments (TRACE and Yohkoh). We focus our study on
observations obtained with the SVST at LaPalma, and with TRACE. On 10
September 1998, arch-filament systems were observed with high spatial
and temporal resolution, from the lower to the upper atmosphere of
the Sun, during five hours. Flux tubes emerged with increasing shear,
which apparently led to energy release and heating in the overlying
corona. A model for filament formation by the emergence of U-shaped
loops from the subphotosphere, as proposed by Rust and Kumar (1994),
is supported by the present observations. The coronal response to these
events is visualized by rising, medium-scale loop brightenings. The
low-lying X-ray loops show short-lived, bright knots which are thought
to result from interaction between different loop systems.

---------------------------------------------------------
Title: Multi-wavelength study of the slow “disparition brusque"
of a filament observed with SOHO
Authors: Schmieder, B.; Delannée, C.; Yong, Deng Yuan; Vial, J. C.;
Madjarska, M.
2000A&A...358..728S Altcode:
A mid-latitude filament was observed before and after its eruption with
SOHO (EIT, SUMER, CDS and LASCO) and with ground based observatories
(Meudon and Pic du Midi) in the context of a coordinated MEDOC
campaign in Orsay. The eruption was followed by a large Coronal
Mass Ejection well observed by LASCO. Few hours before its eruption,
the filament is partially heated (as seen in 195 Ä with EIT). The
physical conditions of the filament before its eruption have been
investigated by spectroscopic analysis of SUMER (the Lyman series L4 to
L9) and of CDS combined with the Multi-channel Subtractive Double Pass
Spectrograph (MSDP) spectra of Hα . Five hours before the eruption,
large broadenings of chromospheric and transition region lines (CDS)
were observed in the main body of the filament suggesting strong
turbulence as well as opposite Dopplershifts on each side of the
filament (Hα and He I) which could be interpreted as twist motions. The
optical thickness of the filament is rather large. During the eruption
the twist is largely developed as observed in 304 Ä. The Doppler
shifts of the filament estimated from Lyman lines are in good agreement
with the velocity of the front edge of the CME bright loop. We notice
that both, the filament and the bright loop, are deviated towards the
equator. This implies that they belong to the same global expansion
event constrained to remain in the equatorial streamer. An X-ray bright
point observed close to a filament footpoint could be the signature of
reconnection process linked to the destabilization of the filament. It
is interpreted in the framework of new MHD modeling of lateral filament
footpoints (Aulanier &amp; Démoulin 1998).

---------------------------------------------------------
Title: Hα and Soft X-Ray Brightening Events Caused by Emerging Flux
Authors: Tang, Y. H.; Li, Y. N.; Fang, C.; Aulanier, G.; Schmieder,
B.; Demoulin, P.; Sakurai, T.
2000ApJ...534..482T Altcode:
By using Yohkoh soft X-ray images, vector magnetograms, and Hα
filtergrams, the brightening event that occurred on 1994 May 18 has
been studied in detail. It occurred in a nearly potential large-scale
magnetic configuration as shown by the comparison between the magnetic
extrapolation (linear force-free field) and the large-scale soft
X-ray loops. This event is related to the emergence of a new magnetic
flux of about 3×1020 Mx. The impulsive enhancement of
the emerging flux occurs about 20 minutes before the peaks of the
Hα and soft X-ray brightening and lasts for about 10 minutes. This
brightening may be a signature of reconnection taking place between the
preexisting nonpotential loops and the new emerging small loops. The
magnetic energy provided by reconnection is likely to be stored in
the nonpotential loops and the emerging flux as implied by the vector
magnetograms. By using the electron temperature and the electron density
of the brightening event derived from the analysis of the Yohkoh data,
an energy budget has been estimated. The result indicates that the
energy needed can be reasonably provided by magnetic reconnection.

---------------------------------------------------------
Title: New Results from the Flare Genesis Experiment
Authors: Rust, D. M.; Bernasconi, P. N.; Eaton, H. A.; Keller, C.;
Murphy, G. A.; Schmieder, B.
2000SPD....31.0302R Altcode: 2000BAAS...32..834R
From January 10 to 27, 2000, the Flare Genesis solar telescope
observed the Sun while suspended from a balloon in the stratosphere
above Antarctica. The goal of the mission was to acquire long time
series of high-resolution images and vector magnetograms of the
solar photosphere and chromosphere. Images were obtained in the
magnetically sensitive Ca I line at 6122 Angstroms and at H-alpha
(6563 Angstroms). The FGE data were obtained in the context of Max
Millennium Observing Campaign #004, the objective of which was to study
the “Genesis of Solar Flares and Active Filaments/Sigmoids." Flare
Genesis obtained about 26,000 usable images on the 8 targeted active
regions. A preliminary examination reveals a good sequence on an
emerging flux region and data on the M1 flare on January 22, as well
as a number of sequences on active filaments. We will present the
results of our first analysis efforts. Flare Genesis was supported
by NASA grants NAG5-4955, NAG5-5139, and NAG5-8331 and by NSF grant
OPP-9615073. The Air Force Office of Scientific Research and the
Ballistic Missile Defense Organization supported early development of
the Flare Genesis Experiment.

---------------------------------------------------------
Title: Foreword
Authors: Vázquez, M.; Schmieder, B.
2000ESASP.463D..13V Altcode: 2000sctc.procD..13V
No abstract at ADS

---------------------------------------------------------
Title: Solar filaments - comparing multi-wavelength observations
with magnetic modelling
Authors: Schmieder, B.
2000ssls.work...57S Altcode:
Multi-wavelength observations of a filament/prominence obtained during
campaigns with the space missions (SOHO, Yohkoh, TRACE) open a new
research field. Physical conditions of filaments and their environment
(i.e. temperature, dynamcis, electron density) provides important
constraints on theories of formation, stability or instability. The
fine structures of filament are discussed in the framework of magnetic
configurations: Is the prominence field a sheared arcade or a twisted
flux rope? What is the magnetic structure of the footpoints of
prominences called also "barbs"? Are the field lines dipped or are
they vertical? We present some new developments of 3-D models of a
bipolar magnetic field and twisted flux tube which explain the fine
structures in prominences as well as the feet. The new models bring
valuable information on the global solar magnetic field with direct
implications for dynamo theories and on the helicity of the heliosphere.

---------------------------------------------------------
Title: Brightening Event in Hα and Soft X-Ray on May 18, 1994
Authors: Tang, Y. H.; Li, Y. N.; Schmieder, B.; Aulanier, G.; Demoulin,
P.; Fang, C.; Sakurai, T.
2000AdSpR..25.1829T Altcode:
By using Yohkoh soft X-ray images, vector magnetograms and Hα
filtergrams, a brightening event that occurred on May 18, 1994 has
been studied in detail. It occurred in a nearly potential large-scale
magnetic configuration as shown by the comparisons between the magnetic
extrapolations (linear force-free field) and the large-scale soft
X-ray loops. This brightening event observed in Hα line and soft
X-ray seems to be related to new emerging magnetic flux with an
amount of photospheric magnetic flux of about 3× 1020
Mx. The emerging flux increases obviously about 20 minutes before the
Hα and soft X-ray brightening, and lasts for about 103
s. This brightening may be a signature of reconnection taking place
between the pre-existing loop and the new emerging small loops

---------------------------------------------------------
Title: N-S Variation of the X-ray Flare Number during the Solar
Cycle 22
Authors: Schmieder, B.; Li, K. J.; Li, Q. S.
2000ESASP.463..423S Altcode: 2000sctc.proc..423S
No abstract at ADS

---------------------------------------------------------
Title: 3-D Magnetic Configurations for Filaments and Flares: The
Role of “Magnetic Dips” and “Bald Patches”
Authors: Aulanier, G.; Schmieder, B.; van Driel-Gesztelyi, L.; Kucera,
T.; Démoulin, P.; Fang, C.; Mein, N.; Vial, J. -C.; Mein, P.; Tang,
Y. H.; Deforest, C.
2000AdSpR..26..485A Altcode:
The 3-D magnetic configuration of a filament and of a low energy
flare is reconstructed, using linear mag- netohydrostatic (lmhs)
extrapolations. In both cases, we find observational signatures
of energy release at the locations of computed “bald patches”
separatrices, characterised by field lines which are tangent to
the photosphere.The filament was observed on Sept. 25, 1996, in Hα
with the MSDP on the German VTT, Tenerife, as well as in Si IV with
SOHO/SUMER. It is modeled as a twisted flux-tube deformed by the
magnetic polarities observed with SOHO/MDI. The shape and location of
the computed dipped field lines are in good agreement with the shape of
the filament and its feet observed in Hα. Some “bald patches” (BPs)
are present where the distribution of dips reaches the photosphere. We
show that some of the large scale field lines rooted in BPs can be
related to bright fine structures in Si IV. We propose that the plasma
there is heated by ohmic dissipation from the currents expected to be
present along the BP separatrices.The flare was observed on May 18,
1994, in soft X-rays with Yohkoh/SXT, and in Hα at Mitaka (Japan). The
magnetic field is directly extrapolated from a photospheric magnetogram
from Kitt Peak Observatory. The intersections with the photosphere of
the computed separatrices match well the bright Hα ribbons. The later
are associated to three BPs, with overlaying dipped field lines. We
show that enhanced densities are present in these dips, which can be
correlated with dark Hα fibrils.Both cases show the importance of
dipped field lines and BPs in the solar atmosphere. Energy release
via ohmic dissipation as well as reconnection along BP separatrices
is proposed to provide heating observed as UV brightenings in filament
channels and even as small flares

---------------------------------------------------------
Title: Dynamics in Restructuring Active Regions Observed During
Soho/Yohkoh/Gbo Campaigns
Authors: Schmieder, B.; Deng, Y.; Mandrini, C. H.; Rudawy, P.; Nitta,
N.; Mason, H.; Fletcher, L.; Martens, P.; Brynildsen, N.
2000AdSpR..25.1879S Altcode:
JOP17 and JOP 33 are SOHO Joint Observing Programs in collaboration
with Yohkoh/SXT and ground based observatories (GBO's), dedicated to
observe dynamical events through the atmosphere. During runs of these
programs we observed in restructuring active regions (ARs), surges,
subflares, bright knots, but not large flares and jets. From these
observations we have been able to derive some of the responses of the
coronal and chromospheric plasma to the evolution of the photospheric
magnetic field. Emerging flux in an AR led to the formation of Arch
Filament Systems in the chromosphere, hot loops and knots in the
transition region, and X-ray loops. Frequent surges have been observed
in relation to parasitic or mixed polarities, but coronal jets have not
yet been found. We discuss the possible mechanisms acting during the
restructuring of the active regions (reconnection or “sea-serpent”
geometries)

---------------------------------------------------------
Title: Solar Prominences Observed by Soho (SUMER, CDS, EIT) and
Ground-Based Observatories (GBO)
Authors: Heinzel, P.; Schmieder, B.; Vial, J. C.; Rudawy, P.
2000AdSpR..25.1777H Altcode:
We present two sets of prominence observations in higher lines
of the hydrogen Lyman series (from Lδ to L-9), together with
some other UV lines. These data have been obtained by the Solar
Ultraviolet Measurements of Emitted Radiation (SUMER) onboard the
SOHO satellite in June 1997. Coordinated observations were also taken
by other SOHO instruments: Coronal Diagnostic Spectrometer (CDS) and
Extreme-Ultraviolet Imaging Telescope(EIT) and with the coronagraph
of the Wroclaw University Observatory at Bialkóv, the spectrograph
of the Ondřejov Observatory. We demonstrate the basic characteristics
of the calibrated line profiles and compare them with the theoretical
profiles computed from isothermal-isobaric models

---------------------------------------------------------
Title: The Total Eclipse Experience in Hungary
Authors: van Driel-Gesztelyi, L.; Jankovics, I.; Kovács, J.;
Schmieder, B.; Vincze, I. J.
1999ESASP.448.1297V Altcode: 1999ESPM....9.1297V; 1999mfsp.conf.1297V
No abstract at ADS

---------------------------------------------------------
Title: Diagnostics Constraints on Prominence Parameters from SOHO
and Ground-based Observations
Authors: Schmieder, B.; Kotrč, P.; Heinzel, P.; Kucera, T.;
Andretta, V.
1999ESASP.448..439S Altcode: 1999ESPM....9..439S; 1999mfsp.conf..439S
No abstract at ADS

---------------------------------------------------------
Title: Interpretation of the Activity due to Flux Emergence in an AR
Authors: Mandrini, C. H.; Démoulin, P.; Schmieder, B.; Deng, Y. Y.;
Rudawy, P.
1999ESASP.448..617M Altcode: 1999ESPM....9..617M; 1999mfsp.conf..617M
No abstract at ADS

---------------------------------------------------------
Title: Bright Rims of Solar Prominences
Authors: Hansen, I.; Engvold, O.; Schmieder, B.; Mein, N.; Mein, P.
1999ESASP.448..491H Altcode: 1999mfsp.conf..491H; 1999ESPM....9..491H
No abstract at ADS

---------------------------------------------------------
Title: A Study of Hydrogen Density in Emerging Flux Loops from a
Coordinated TRACE and Canary Islands Observation Campaign
Authors: Schmieder, B.; Deluca, E.; Mein, N.; Mein, P.; Malherbe,
J. M.; Wilken, V.; Staiger, J.; Engvold, O.; Hanssen, I.
1999ESASP.448..653S Altcode: 1999mfsp.conf..653S; 1999ESPM....9..653S
No abstract at ADS

---------------------------------------------------------
Title: Fine-Structures and Dynamics of a Filament in EUV lines:
SOHO/CDS and SUMER, TRACE
Authors: Schmieder, B.; Engvold, O.; Wiik, J. E.; Deluca, E.
1999ESASP.446..599S Altcode: 1999soho....8..599S
No abstract at ADS

---------------------------------------------------------
Title: Hydrogen Lyman Lines and Continuum Emission in a Polar-Crown
Prominence Observed with SUMER/SOHO
Authors: Schmieder, B.; Kucera, T.; Heinzel, P.; Vial, J. -C.
1999ESASP.446..605S Altcode: 1999soho....8..605S
We present, for the first time, a quasi-simultaneous spectroscopic
observation of the whole Lyman series of HI and continuum in a
quiescent prominence. Namely we have extended our previous study of
higher Lyman lines to lower members of the series, particularly
L-alpha and L-beta. For the latter two lines, we compare our
calibrated profiles (free of geocoronal absorption) with previous
data from OSO-8 LPSP spectrometer and (for L-alpha) from UVSP/SMM. We
demonstrate the importance of Lyman lines for studies of the base of
the prominence-corona transition region.

---------------------------------------------------------
Title: Analysis of evolution of NOAA 7912 active region on 19
October 1995
Authors: Rudawy, P.; van Driel-Gesztelyi, L.; Cader-Sroka, B.; Mein,
P.; Mein, N.; Schmieder, B.; Malherbe, J. -M.; Rompolt, B.
1999A&AS..139...89R Altcode:
An analysis of a minor (B3.2) flare related to an X-ray jet in the
reversed polarity NOAA 7912 active region is presented, focusing
on various kinds of activity observed in the Hα line with the MSDP
instrument. Using complementary Yohkoh soft X-ray observations and a
Kitt Peak magnetic field map we study the influence of a rather low
and graduate energy release on filaments, fibrils and chromospheric
brightenings and their relevant coronal features. We find that this
small flare affected the entire AR and was associated with strong up-
and downflows along remote fibrils and filaments, which appear to be
connected by large-scale loops. It is shown that at least one of the
observed brightenings was caused by downflow of the matter, thus, by
the kinematic heating of the material. The filament in the vicinity
of the flare footpoints changed the most: it broke into two parts,
temporarily rose to higher altitudes inside the AR and even erupted
outside of the AR, re-forming only three hours later. We show that
even a minor flare can lead to important morphological and dynamical
changes in an active region.

---------------------------------------------------------
Title: SOHO/SUMER observations and analysis of hydrogen Lyman lines
in a quiescent prominence
Authors: Schmieder, B.; Heinzel, P.; Vial, J. C.; Rudawy, P.
1999SoPh..189..109S Altcode:
A quiescent prominence was observed in June 1997 by instruments
onboard the SOHO spacecraft: the Solar Ultraviolet Measurements of
Emitted Radiation (SUMER), Coronal Diagnostic Spectrometer (CDS)
and Extreme-Ultraviolet Imaging Telescope (EIT), along with the
coronagraph of the Wrocław University Observatory at Bialków and
the spectrograph of the Ondřejov Observatory. We present prominence
observations in higher lines of the hydrogen Lyman series (from Lδ
to L-9), together with some other UV lines obtained by SUMER. We
extract the basic characteristics of the calibrated line profiles
of these Lyman lines and compare them with the theoretical profiles
computed from three kinds of NLTE models which also include prominence
filamentation. Our principal result is that the current NLTE models are
in principle capable of explaining the SUMER calibrated intensities
in the observed Lyman lines. We also find that in order to fit all
these lines, one has to consider a prominence-corona transition region
(PCTR) with a temperature gradient. At low pressures, higher Lyman
lines are still rather sensitive to the incident radiation which must
be carefully taken into account in the modeling. From PCTR models,
which also take into account the effect of ambipolar diffusion on the
heating, we have derived the formation depths for the Lyman series
lines. High Lyman lines seem to be formed just at the base of the PCTR.

---------------------------------------------------------
Title: The Role of "Magnetic Dips" and "Bald Patches" for a Filament
Observed by SOHO and GBO
Authors: Aulanier, G.; Schmieder, B.; Kucera, T.; van Driel-Gesztelyi,
L.; Démoulin, P.; Mein, N.; Vial, J. -C.; Mein, P.
1999ASPC..184..291A Altcode:
The studied filament was observed on Sept. 25, 1996, in Hα with
the MSDP on the German VTT, Tenerife, as well as in Si IV with
SOHO/SUMER. The 3-D magnetic configuration of the filament channel is
reconstructed, using linear magnetohydrostatic (lmhs) extrapolations
from a SOHO/MDI magnetogram, which is modified by a background magnetic
component constraining a twisted flux-tube. This flux-tube is deformed
by the magnetic polarities observed with SOHO/MDI. The shape and
location of the computed "dipped field lines" are in good agreement
with the shape of the filament and its feet observed in Hα. Some "bald
patches" (BPs) are present where the distribution of dips reaches the
photosphere. We find observational signatures in Si IV brightenings of
energy release at the locations of computed "bald patch separatrices",
defined by field lines which are tangent to the photosphere. We propose
that the plasma is there heated by ohmic dissipation from the expected
currents in the BP separatrices. The results show the importance of
"dipped field lines" and "bald patches" in filament channels.

---------------------------------------------------------
Title: Magnetic Field Evolution and Topology of an AR
Authors: Mandrini, C. H.; Deng, Y. Y.; Schmieder, B.; Démoulin, P.;
Rudawy, P.; Nitta, N.; Newmark, J.; de Forest, C.
1999ASPC..184..276M Altcode:
Active region 7968 was observed during runs of a coordinated SOHO,
Yohkoh and ground-based observatory program (Joint Observing Program,
JOP, 17). The region appeared and decayed in a seven day period (June 3
to 10, 1996). In this time, mainly during June 6, it presented a very
dynamical behaviour. Flux emerged in between the two main polarities
and Arch Filament Systems (AFS) were observed to be linked to this
emergence. We analyze the evolution of some over dark arches observed
during flux emergence, forming two systems of AFS. Modelling the
magnetic field, we find that these systems were associated to field
lines having dips tangent to the photosphere (the so called "bald
patches", BPs). We discuss their evolution in terms of emergence of
the dipped portion of the lines or of magnetic field reconnection.

---------------------------------------------------------
Title: Coordinated Prominence Observations by SOHO and Ground-Based
Observatories
Authors: Schmieder, B.; Heinzel, P.; Vial, J. -C.; Malherbe, J. M.;
Mein, P.; Rudawy, P.; Ceppatelli, G.
1999ASPC..184..296S Altcode:
Coordinated observations obtained during the JOP12 (Joint Observing
Programme between SOHO and ground-based instruments) allow us to
analyse the physical conditions in a prominence of 5 June 1997 and
its environment in the solar corona. The arch-shaped prominence shows
either vertical or horizontal structures according to the observed
lines (Hα with the coronagraph of the Wroclaw University Observatory
at Bialków and lines in a broad temperature range by the Coronal
Diagnostic Spectrometer CDS). The less dynamic behaviour of this
prominence was shown by the persistence of bubbles in the prominence
and confirmed by the Dopplershifts measured in CDS lines and in Hα
by the Italian Panoramic Monochromator (IPM) filter on the THEMIS
telescope in Tenerife. We explain the complex morphology of this
prominence by recent 3D MHD models. Finally, we present prominence
spectra in higher lines of the hydrogen Lyman series (from Lδ to L-9),
together with some other UV lines. These data have been obtained by
the Solar Ultraviolet Measurements of Emitted Radiation (SUMER). We
demonstrate the basic characteristics of the calibrated line profiles
of Lyman lines and compare them with the theoretical profiles computed
from isothermal-isobaric models. This leads to some constraints on
the environment of the prominence.

---------------------------------------------------------
Title: Long-Term Magnetic Evolution of an AR and its CME Activity
Authors: van Driel-Gesztelyi, L.; Mandrini, C. H.; Thompson, B.;
Plunkett, S.; Aulanier, G.; Démoulin, P.; Schmieder, B.; de Forest, C.
1999ASPC..184..302V Altcode:
Using SOHO/MDI full-disc magnetic maps, we follow the magnetic
evolution of a solar active region for several months in the period of
July-November 1996. We extrapolate the photospheric magnetic fields in
the linear force-free approximation and match the modelled field lines
with the soft X-ray loops observed with the Yohkoh/SXT in order to
diagnose the coronal magnetic shear. We find that while the turbulent
motions diffuse the flux, the differential rotation, and possibly
twisted flux emergence, increase the magnetic shear. Flares are observed
during the first three rotations, while CME events (observed by SOHO/EIT
and LASCO) originate from this AR from its emergence throughout its
decay. Several early CMEs, while none of the late CMEs, are related to
flare events above the GOES B1 level. We find that the late CMEs occur
when the magnetic shear, after accumulating for four rotations, reaches
a high level and saturates. We propose that CME activity serves as a
valve through which the AR could get rid of excess shear and helicity.

---------------------------------------------------------
Title: The evolution from birth to decay of a short-lived active
region
Authors: Deng, Yuan Yong; Schmieder, Brigitte; Mandrini, Cristina H.;
Khan, Josef I.; Démoulin, Pascal; Rudawy, Pawel
1999A&A...349..927D Altcode:
In the following paper we present results of the analysis of NOAA active
region 7968, which was the target of a coordinated observing campaign
involving the instruments aboard the Solar and Heliospheric Observatory
(SOHO), Yohkoh, and ground-based observatories (Bialków, Pic du Midi,
and Huairou). This active region was relatively short-lived, and thus
provides a rare example of a region observed continuously from its birth
to its decay phase. We have extrapolated the SOHO Michelson Doppler
Imager (MDI) longitudinal magnetograms, and have compared the results of
the modeled field with loops observed over a wide range of temperatures
( ~ 10(5) -3x10(6) K). We find that, throughout the interval of disk
passage, the global magnetic structure of the active region corresponds
to a nearly potential-field configuration. Magnetic field shear is
only seen in isolated patches along the polarity inversion line and is
associated with the emergence of parasitic polarity regions. Several
small GOES (B-class) X-ray flares and surge-like ejections were
observed during the lifetime of the active region. We interpret both
the heating of the active region loops and the flaring in terms of
magnetic reconnection. In our scenario, the flares are assumed to be
due to reconnection between the pre-existing field and newly emerging
twisted flux tubes (as indicated by observed changes in the transverse
field and inferred twisting motions of the plasma); while the heating of
the plasma in quasi-static active region loops is assumed to be due to
a relaxation process of the magnetic configuration. These loops appear
anchored at places where the photospheric field is highly fragmented,
creating a very complex connectivity pattern. This fact, together with
the continual photospheric motions, provides the favorable conditions
for current sheet formation and release of magnetic energy.

---------------------------------------------------------
Title: Some Advances in 3D-Magnetic Field Topology: an Observed Case
of a "Bald Patch" Flare
Authors: Démoulin, P.; Aulanier, G.; Schmieder, B.
1999ASPC..184...65D Altcode:
The aim of this work is to bring observational evidences of the
possible role of the "bald patch" topology in flaring events. A bald
patch (or BP) is present along the photospheric inversion line where
the field lines are curved-up, so when magnetic dips are present. The
set of field lines associated to the BP define a separatrix where a
current sheet may form. We find such configuration in AR 7722 where,
on May 18, 1994, a sub-flare was observed in X-rays by Yohkoh/SXT and
in Hα at NAOJ. Using the magnetohydrostatic equations derived by Low
(1992), we model the magnetic field configuration by extrapolation
of the Kitt Peak photospheric field, taking into account the effects
of pressure and gravity. Hα flare kernels are shown to be located at
the lower parts of the computed separatrices associated to bald patches
(BPs). This is an evidence that BPs can be involved in flares, and that
current sheets can be dissipated in low levels of the solar atmosphere.

---------------------------------------------------------
Title: Multiple-Thread Model of a Prominence Observed by SUMER and
EIT on SOHO
Authors: Wiik, J. E.; Dammasch, I. E.; Schmieder, B.; Wilhelm, K.
1999SoPh..187..405W Altcode:
A quiescent polar crown prominence was observed at Meudon in Hα and
Ca ii lines, and by EIT and SUMER on board SOHO in UV lines from 9
to 10 March 1996. SUMER observed the prominence continuously in a
scanning mode between 21:40 UT on 9 March, and 18:13 UT on 10 March,
in the nitrogen line N v (λ1238) with a 1 arc sec2
resolution. Altogether 190 prominence images (121×108 pixels)
were obtained. These are presented in a movie. The prominence is
highly dynamic. Large-scale features, such as mixed loop systems and
dark cavities are changing on time scales of a few hours. Filamentary
structure is evident and is changing within a few frames of the movie. A
lifetime of 20-25 min for the fine structure has been found by the
autocorrelation method. We have statistically analysed the three
moments of the N v line in the prominence: line intensity, Doppler
shift and linewidth, in the context of a multiple-thread model. We
find that the data are consistent with a model where the prominence is
assumed to be an ensemble of small threads. In the brightest parts of
the prominence it is possible that there are many unresolved threads
(15-20) along the line of sight with diameters smaller than a few
hundred kilometers. The filling factor is probably very small and in
that case the structures occupy only a fraction of the volume.

---------------------------------------------------------
Title: Derivation of physical parameters of chromospheric structures
assuming a constant and a varying source function
Authors: Tsiropoula, G.; Madi, C.; Schmieder, B.
1999SoPh..187...11T Altcode:
Hα profiles of a rosette region consisting of several bright and dark
mottles were obtained with the Multichannel Subtractive Double Pass
(MSDP) spectrograph mounted on the 50 cm 'Tourelle' refractor of the
Pic du Midi Observatory. These profiles have been analysed in terms
of the classical cloud model which assumes a constant source function
and holds only for optically thin structures. A new technique is also
described which enables the determination of various physical parameters
of chromospheric features taking into account the variation of the
source function with the optical depth. This method can be applied, in
contrast to the classical cloud model, to all lines whether optically
thin or optically thick and gives a good fit to the entire profile
from the core to the wings. A comparison of the results given by the
two different methods is also performed.

---------------------------------------------------------
Title: A new emerging flux and brightening event.
Authors: Li, Yining; Tang, Yuhua; Aulanier, G.; Schmieder, B.;
Demoulin, P.; Fang, Cheng
1999PPMtO..18..131L Altcode:
By using Yohkoh soft X-ray images, vector magnetograms and Hα
filtergrams, a brightening event of Hα and soft X-ray of 18 May, 1994
has been studied in detail. It is shown that the event is obviously
caused by new emerging flux. The brightening points of Hα and soft
X-ray are located at computed separatrices associated to field lines
which are tangent to the photosphere. This brightening event may be a
signature of reconnection taking place between the pre-existing loops
and the new emerging small loops in the lower solar atmosphere.

---------------------------------------------------------
Title: Filament channel structures in a SI IV line related to a 3d
magnetic model
Authors: Kucera, T. A.; Aulanier, G.; Schmieder, B.; Mein, N.; Vial,
J. -C.
1999SoPh..186..259K Altcode:
A recent 3D magnetic model of filament support (Aulanier and Démoulin,
1998) has shown that specific morphologies derived from the model, based
on SOHO/MDI magnetograms, match quite well with the observations of a
filament observed in Hα and Ca ii lines with the German telescope VTT
in Tenerife on 25 September 1996 (Aulanier et al., 1998, 1999a). Some
predictions of this model concern the filament channel. To continue the
comparison of model and data, we have investigated the same filament
region observed in ultraviolet by the SOHO spectrometers SUMER and
CDS. The elongated EUV fine structures in the filament channel observed
in the Si iv 1393.76 Å line by SUMER have similar orientations
and locations to features predicted by the model of Aulanier et
al. (1999a). These regions are near the bases of field lines which
tangentially join to the photosphere in so called 'bald patches' and
are parts of large arcades above the filament channel. In addition,
we consider the Si iv Doppler shifts in these structures and compare
them to what might be expected from the model field structure. Our
study also suggests that the filament has a very low opacity in Si iv,
lower than that of the O v line observed by CDS.

---------------------------------------------------------
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: Analysis Of The Disappearing Filament And Flare Of 7 May 1992
Authors: Tang, Y. H.; Mouradian, Z.; Schmieder, B.; Fang, C.;
Sakurai, T.
1999SoPh..185..143T Altcode:
By using Yohkoh soft X-ray data, Hα filtergrams, and radio data, the
activation of the disappearing filament and the flare eruption on 7
May 1992 have been studied. Main conclusions are as follows: (1) the
emergence of new magnetic flux tends to affect the pre-existing X-ray
loops, which usually appear in arcades spanning Hα filament, changing
the magnetic environment of the filament, and then enhance the current
in the filament. Therefore newly emerging flux plays a fundamental
role in the destabilization of this filament. (2) According to the Hα
data and the rising motion of the filament, the corresponding current
variation in the filament has been calculated. It seems that the current
interruption may be a possible trigger mechanism for this filament
disappearance. (3) The magnetic field strength and the energy flux
of energetic electrons in the source region of microwave bursts have
been estimated by using the microwave spectrum. During the main phase,
the mean magnetic strength and the energy flux of energetic electrons
are about 300-400 G and 1×1011 erg cm−2 s −1, respectively. (4)
The energy provided by reconnection of the current sheet and the total
energy of the current filament are estimated and we show that there
is enough energy stored in the filament to feed the 7 May, 1992 flare.

---------------------------------------------------------
Title: 3-D magnetic configurations supporting
prominences. III. Evolution of fine structures observed in a filament
channel
Authors: Aulanier, G.; Démoulin, P.; Mein, N.; van Driel-Gesztelyi,
L.; Mein, P.; Schmieder, B.
1999A&A...342..867A Altcode:
On September 25() th 1996, a quiescent filament located near the
center disc (S2, E5) was observed on the German VTT (Tenerife)
with the MSDP instrument, in the Hα line center and wings. SOHO/MDI
line-of-sight magnetograms were co-aligned with the MSDP images, showing
the position and evolution of the lateral feet of the filament in the
vicinity of the parasitic magnetic polarities observed in the filament
channel. Using the assumptions developed in the previous papers of this
series related to the reconstruction of the 3-D magnetic configuration
of filaments, we perform “linear magnetohydrostatic” extrapolations
(taking into account the effects of plasma pressure and gravity) on the
SOHO/MDI magnetograms. The main hypothesis is the presence of a twisted
flux-tube located above the photospheric inversion line. Assuming that
the parameters of the model do not need to be significantly modified
during the evolution of the configuration for a duration of 1 day,
we have shown that the 3-D distribution of dipped field lines is well
correlated with Hα dark absorbing features in the filament channel:
the filament itself, its lateral feet and some of the surrounding dark
fibrils. In this way we confirm what was suggested in our earlier
papers, i.e. that the feet are composed of the dipped portions of
some field lines, which form a continuous pattern from the corona
to the photosphere. We propose the same explanation for the magnetic
configuration of some of the dark Hα fibrils in the channel. We show
that the plasma effects are not responsible for the existence of most
of the magnetic dips, however their inclusion helps to get a better
correspondence between the model and the observations. We find that the
average Hα Doppler velocities associated with the filament and with
the chromospheric fibrils is of the order of a few hundred m s(-1)
(though it can go locally up to 3 km s(-1) in the filament). These
upward velocities are consistent with a quasi-static evolution of
the magnetic configuration and with the support of dense plasma in
magnetic dips.

---------------------------------------------------------
Title: Third Advances in Solar Physics Euroconference: Magnetic
Fields and Oscillations
Authors: Schmieder, B.; Hofmann, A.; Staude, J.
1999ASPC..184.....S Altcode:
The third Advances in Solar Physics Euroconference (ASPE) "Magnetic
Fields and Oscillations"concluded a series of three Euroconferences
sponsored by the European Union. The meeting took place in Caputh
near Potsdam, Germany, on September 22-25, 1998, followed by the JOSO
(Joint Organization for Solar Observations) 30th Annual Board Meeting
on September 26, 1998. The ASPE formula is attractive and compares well
with other meetings with "show-and-tell" character. This meeting had
122 participants coming from 26 countries; 36 participants came from
countries formerly behind the Iron Curtain; a "politically incorrect"
estimate says that 48 participants were below 35 years of age,
with an unusually large female-to-male ratio. This characteristic of
youngness is the more striking since solar physics is a perhaps overly
established field exhibiting an overly senior age profile. It was a
good opportunity to train this young generation in Solar Physics. The
conference topic "Magnetic Fields and Oscillations" obviously was
wide enough to cater to many an interest. These proceedings are
organized according to the structure of the meeting. They include
the topics 'High resolution spectropolarimetry and magnetometry',
'Flux-tube dynamics', 'Modelling of the 3-D magnetic field structure',
'Mass motions and magnetic fields in sunspot penumbral structures',
'Sunspot oscillations', 'Oscillations in active regions - diagnostics
and seismology', 'Network and intranetwork structure and dynamics',
and 'Waves in magnetic structures'. These topics covered the first
2.5 days of the conference. The reviews, oral contributions, and
poster presentations were by no means all of the meeting. The ASPE
formula also adds extensive plenary sessions of JOSO Working groups
on topics that involve planning of Europe-wide collaboration. At this
meeting these concerned solar observing techniques, solar data bases,
coordination between SOHO and ground-based observing, and preparations
for August 11, 1999 when more Europeans will be eclipsed than ever
before. The contributions to these sessions have been included into
the present volume as well. The participants of the EU-TMR Research
Network 'Solar Magnetometry Network' came together to discuss in a
special working group session questions of their future collaboration.

---------------------------------------------------------
Title: Bright Points and Subflares in Ultraviolet Lines and X-Rays
Authors: Rovira, M.; Schmieder, B.; Démoulin, P.; Simnett, G. M.;
Hagyard, M. J.; Reichmann, E.; Tandberg-Hanssen, E.
1999ApJ...510..474R Altcode:
We have analyzed an active region which was observed in Hα
(Multichannel Subtractive Double Pass Spectrograph), in UV lines
(SMM/UVSP), and in X-rays (SMM/HXIS). In this active region there
were only a few subflares and many small bright points visible in UV
and in X-rays. Using an extrapolation based on the Fourier transform,
we have computed magnetic field lines connecting different photospheric
magnetic polarities from ground-based magnetograms. Along the magnetic
inversion lines we find two different zones: (1) a high-shear region
(&gt;70°) where subflares occur, and (2) a low-shear region along
the magnetic inversion line where UV bright points are observed. In
these latter regions the magnetic topology is complex with a mixture
of polarities. According to the velocity field observed in the Si IV
λ1402 line and the extrapolation of the magnetic field, we notice that
each UV bright point is consistent with emission from low-rising loops
with downflows at both ends. We notice some hard X-ray emissions above
the bright-point regions with temperatures up to 8 × 106 K,
which suggests some induced reconnection due to continuous emergence of
new flux. This reconnection is also enhanced by neighboring subflares.

---------------------------------------------------------
Title: Calentamiento de arcos coronales en una región activa por
reconfiguración topológica del campo magnético.
Authors: López Fuentes, M.; Mandrini, C. H.; Démoulin, P.; Schmieder,
B.; Fletcher, L.; Mason, H.
1999BAAA...43...24L Altcode:
We study the active region (AR) 8048 observed on June 1997 in several
wavelenghts. The combined observations obtained using CDS (SOHO)
and SXT (Yohkoh) show the heating of the coronal magnetic loops at
different atmospheric altitudes. Extrapolating the magnetic field in the
corona from longitudinal magnetograms from MDI (SOHO), we determine the
location of Bald Patches in the surroundings of the leading spot. This
magnetic feature, the emergence of parasitic magnetic polarities and
the observed photospheric motions provide the conditions to explain
the observed heating.

---------------------------------------------------------
Title: Eruptive filament of May 31, 1997, observed by SOHO.
Authors: Schmieder, B.; Heinzel, P.; Vial, J. -C.; Delaboudinière,
J. -P.; Delannée, C.
1999joso.proc..147S Altcode:
In the frame of the SUMER/CDS Joint Programme (JOP 17) the authors
have detected the four Lyman lines in an erupting filament. The
strong self-absorption in these lines, already reported for quiescent
filaments, is still present in this highly dynamical event, but the
authors observe a significant red asymmetry in the intensities of the
two peaks. They ascribe it to an upward bulk motion of the filament,
which they can actually see on a series of EIT images taken in the
Fe XII line. Both sets of observations can lead to a determination
of the velocity vector. The Doppler velocities are also derived from
other lines detected by SUMER/CDS and can be correlated with the
observations of the Pic-du-Midi MSDP obtained for this event. The
filament eruption was also well observed by other GBO instruments in
the Hα line (Meudon and Ondřejov).

---------------------------------------------------------
Title: Magnetic fields and oscillations. 3rd Euroconference ASPE98
(Advances in Solar Physics Euroconference 1998), Potsdam/Caputh
(Germany), 22 - 25 Sep 1998. Poster contributions.
Authors: Schmieder, B.; Staude, J.
1999joso.proc...74S Altcode:
All of the oral presentations of ASPE98 will be published in a separate
volume of the ASP Conference Series, while this volume contains the
poster presentations.

---------------------------------------------------------
Title: Active Regions
Authors: Holman, G. D.; Cheng, C. -C.; Gurman, J. B.; Haisch, B. M.;
Poland, A. I.; Porter, J. G.; Saba, J. L. R.; Schmieder, B.; Strong,
K. T.
1999mfs..conf...41H Altcode:
Magnetic Field Strength and Strucutre Results Prior to SMM First Results
with SMM Subsequent Results: 1983-1987 The Coronal Magnetic Structures
Observing Campaign Coronal Magnetic Field Studies after SMM Dynamics
and Heating of the Solar Corona FCS Line-Broadening Measurements
Large Nonthermal Velocities Spatial Variations Correlation Studies FCS
Line-Broadening Data Interpreting the FCS Line Broadening Constraints
on Mass Motions Link to Heating Discussion Coronal Heating, Magnetic
Fields, and Flares UVSP Obervations of Active Regions Transition Region
Brightenings: UV Microflares Sunspots Magnetic Field and Height of the
Transition Region Sunspot Plumes Sunspot Flows Horizontal Flows Vertical
Flows Nonthermal Line Broadening Umbral Oscillations A Look Backward,
a Look Forward Prominences and Filaments Prominence Environment and
Structure Steady Flows in Prominence Material Activity in Prominences
Postflare Loops and Surges Conclusion

---------------------------------------------------------
Title: Analysis of H profiles. Physical parameters of chromospheric
mottles: A case study
Authors: Tsiropoula, G.; Madi, C.; Schmieder, B.; Preka-Papadema, P.
1999A&AT...18..455T Altcode:
Observations of a well-defined rosette region which consisted of
several bright and dark mottles and located almost at the solar disc
centre (N5, W5) were made with the Multichannel Double Pass (MSDP)
spectrograph mounted on the 50 cm "Tourelle" refractor of the Pic
Du Midi Observatory, on June 17, 1986. This instrument records a
two-dimensional field on the solar surface and having 11 channels
provides at every pixel of the field of view the profile of the H
line. We have used these profiles to derive several physical parameters
of the chromospheric mottles. The basic assumption of the method we used
is that the source function is not constant inside the structures, but
has a parabolic variation with the optical depth. By using an iterative
least square procedure for non-linear functions, five parameters of
chromospheric mottles were computed: the optical depth, the Doppler
width, the line-of-sight velocity, the source function at the middle
of the structure, and the source function's variation factor.

---------------------------------------------------------
Title: New Perspectives on Solar Prominences
Authors: Schmieder, B.
1999ASPC..158..133S Altcode: 1999ssa..conf..133S
No abstract at ADS

---------------------------------------------------------
Title: Multiple-thread model of a prominence observed by SUMER and
EIT on SOHO and by GBO's.
Authors: Wiik, J. E.; Dammasch, I. E.; Schmieder, B.; Wilhelm, K.
1999joso.proc..184W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Physical properties of the quiescent prominence of 5June 1996,
from Hα observations
Authors: Li, Kejun; Schmieder, B.; Malherbe, J. -M.; Roudier, Th.;
Wiik, J. -E.
1998SoPh..183..323L Altcode:
The Multichannel Subtractive Double Pass spectrograph (MSDP) is designed
to observe line profiles in a 2D field of view with a good spatial and
temporal resolution. In order to deal with this unique opportunity,
we introduce a new method for fitting the hydrogen Hα line formed in
prominences and deriving various plasma parameters from line profile
observations. A quiescent prominence was observed on 5June 1996, at
the Pic du Midi during an international campaign between 09:30UT and
11:00UT with the MSDP spectrograph operating in Hα at the Turret
Dome. Using the new fitting method, we show that the temperature,
column density of hydrogen atoms and microturbulent velocity of the
prominence are respectively about 8500K, 1.4x1012cm-2, and 10 to
20kms-1. The electron density of the prominence is about 1.8x1010cm-3.

---------------------------------------------------------
Title: Magnetohydrostatic Model of a Bald-Patch Flare
Authors: Aulanier, G.; Démoulin, P.; Schmieder, B.; Fang, C.; Tang,
Y. H.
1998SoPh..183..369A Altcode:
On 18 May, 1994, a subflare was observed in AR 7722 in X-rays by
Yohkoh/SXT and in Hα at National Astronomical Observatory of Japan. The
associated brightenings are due to small-scale magnetic energy release,
triggered by parasitic fluxes emerging and moving at the edge of leading
sunspots. Using the magnetohydrostatic equations derived by Low (1992),
we model the magnetic field configuration by extrapolation of the Kitt
Peak photospheric field, taking into account the effects of pressure
and gravity. Hα flare kernels are shown to be located at computed
separatrices associated with field lines which are tangent to the
photosphere, namely 'bald patches' (BPs). This is evidence that BPs
can be involved in flares, and that current sheets can be dissipated
in low levels of the solar atmosphere. The presence of dense plasma
which is supported against gravity in the magnetic dips above BPs is
correlated to dark elongated features observed in Hα. Mass flows in
these flat fibrils are discussed in the context of energy release in
the BP separatrices. The effect of the plasma on the computed magnetic
configuration is shown to be of secondary importance with respect to
the topology of the field.

---------------------------------------------------------
Title: Spectral Analysis of a Thermal Flare on 27 October 1993
Authors: Schmieder, B.; Fang, C.; Harra-Murnion, L. K.
1998SoPh..182..447S Altcode:
A thermal subflare occurring on 27 October 1993 was observed during
a multi-wavelength campaign with the Yohkoh spacecraft and the
Multi-channel Subtractive Double-Pass spectrograph (MSDP) at Pic du
Midi. The various instruments provided us with 2-D Hα spectra, X-ray
spectra and X-ray images. A non-LTE computation (including chromospheric
condensation) was carried out to determine the dynamic parameters of
the flaring chromosphere. By combining these results with the Yohkoh
data, we illustrate that momentum is balanced between the upflowing
plasma and the downflowing cool plasma during the flare. This result
is consistent with the evaporation model.

---------------------------------------------------------
Title: Multi-wavelength observations of POST flare loops in two long
duration solar flares
Authors: Harra-Murnion, L. K.; Schmieder, B.; van Driel-Gesztelyi,
L.; Sato, J.; Plunkett, S. P.; Rudawy, P.; Rompolt, B.; Akioka, M.;
Sakao, T.; Ichimoto, K.
1998A&A...337..911H Altcode:
We have analysed two Long Duration solar Events (LDEs) which produced
large systems of Post Flare Loops (PFLs) and which have been observed by
Yohkoh and ground-based observatories. Using the Maximum Entropy Method
(MEM) image synthesis technique with new modulation patterns we were
able to make hard X-ray (HXR) images of the post flare loops recorded
in the L Channel (13.9-22.7 keV) of the Yohkoh Hard X-ray Telescope. We
obtained co-aligned 2-D maps in Hα (10(4) K), in soft X-rays (5x 10(6)
K) and in hard X-rays (20x 10(6) K). We conclude that the soft X-ray
(SXR) loops lie higher than the Hα loops and the former are overlaid
by HXR emission. This is suggestive of the magnetic reconnection
process. However some details are not consistent with the standard
models. Firstly the separation between the HXR source and the SXR
loop increases with time, with the HXR source being approximately
a factor of five larger than the equivalent source in impulsive
flares. Secondly the cooling times deduced from observations are longer
than the theoretically expected ones and the discrepancy increases
with time. We review the current models in view of these results.

---------------------------------------------------------
Title: Filament Observations with SOHO Sumer/cds: The Behaviour of
Hydrogen Lyman Lines
Authors: Schmieder, B.; Heinzel, P.; Kucera, T.; Vial, J. -C.
1998SoPh..181..309S Altcode:
On 21 September 1996, a filament close to an area of enhanced network
was observed with the Solar Ultraviolet Measurements of Emitted
Radiation (SUMER) spectrometer and Coronal Diagnostic Spectrometer
(CDS). CDS provided intensity, Doppler shift and linewidth maps of the
region in six lines whose temperature range covers 104 to
106 K. SUMER observations consisted of maps of the region
in four hydrogen Lyman lines (Lδ, L∈, L-6, L-7) and a Svi line
(944 Å). In all the Lyman lines we detect a central absorption
and an asymmetry in the intensity of the two peaks. First NLTE
computations indicate that such reversed Lyman profiles and their
absolute intensities can be reproduced with the existing filament models
provided that we take into account a prominence-corona transition region
(PCTR). We discuss the Lyman lines' asymmetry in terms of macroscopic
flows by comparison with the Hei line Doppler shifts observed with CDS.

---------------------------------------------------------
Title: Statistical analysis of the X-ray flares (M &gt;= 1) during
the maximum period of solar cycle 22
Authors: Li, K. -J.; Schmieder, B.; Li, Q. -Sh.
1998A&AS..131...99L Altcode:
The data of the X-ray flare events of class M&gt;= 1 during the
interval of 1987 to 1992 corresponding to the maximum period of the
22nd solar cycle have been investigated to study the North-South (N-S)
and West-East (W-E) asymmetries. During that period it has been shown
the existence of a real N-S asymmetry. That confirms recent studies
done by using other indicators, such as sunspot areas \cite[(Oliver
&amp; Ballester 1994)]{oliv94}. The E-W asymmetry during that period
is not significant but a non uniform flare distribution in longitude
has been evidenced. That result is also in good agreement with the
work made by \cite[Joshi (1995)]{josh95} using Hα flares for the
same time period. We have shown that the behaviour of the reverse
tendency of Solar Cycle 21 to exhibit a predominance of the southern
hemisphere in the N-S asymmetry compared to the previous Solar Cycles
(19 and 20) is maintained for Solar Cycle 22. A long period cycle of
the N-S asymmetry could be suspected.

---------------------------------------------------------
Title: Arch Filament Systems Associated with X-Ray Loops
Authors: Malherbe, J. M.; Schmieder, B.; Mein, P.; Mein, N.; Van
Drielgesztelyi, L.; Von Uexküll, M.
1998SoPh..180..265M Altcode:
Using multi-wavelength observations obtained with the Tenerife
telescopes (VTT and GCT) and with the Yohkoh satellite, we observed
new emerging flux with an associated arch filament system (AFS) in
the chromosphere and bright X-ray loops in the corona. We observed the
change of connectivity of the X-ray loop footpoints which may be at the
origin of the occurrence of a subflare. Densities, gas and magnetic
pressures of cold AFS and hot loops were derived and discussed. The
extrapolation of the photospheric magnetic field observed with the GCT
in a linear force-free field assumption (constant α) shows that this
region, in spite of having roughly a global potential configuration,
consists of two systems of arch filaments. We found these two systems
best fitted with two sheared magnetic topologies of opposite α values
of ± 0.1 Mm-1

---------------------------------------------------------
Title: A possible interpretation of the inhomogeneity and material
motion within the post-flare loop of June 26, 1992.
Authors: You, Dan; Tang, Yuhua; Fang, Cheng; Schmieder, B.
1998AcASn..39..165Y Altcode:
Using the theory of linear current instability, the authors discussed
the possibility of inhomogeneous "knot" structures within the post-flare
loop of June 25 - 26, 1992. Besides, by simultaneously considering
the gravity of the Sun, magnetic stress within the loop and primary
velocity at the top, the authors theoretically calculated the motion
of matter within the post-flare loop. The theoretical results are in
accord with observations.

---------------------------------------------------------
Title: The Postflare Loops and the Nearby Active Chromosphere of
1992 June 26: Addendum
Authors: Malherbe, J. -M.; Tarbell, T.; Wiik, J. E.; Schmieder, B.;
Frank, Z.; Shine, R. A.; van Driel-Gesztelyi, L.
1998ApJ...495..502M Altcode:
Video segments are presented that were processed from a quantitative
study of the dynamics of the evolution of Hα postflare loops developed
after a large solar flare. The high spatial resolution of the Swedish
Vacuum Solar Telescope (SVST) at La Palma provided a unique set of
data for such an event.

---------------------------------------------------------
Title: First Observations with THEMIS
Authors: Rayrole, J.; Mein, P.; Schmieder, B.
1998ASPC..155..260R Altcode: 1998sasp.conf..260R
No abstract at ADS

---------------------------------------------------------
Title: SUMER/SOHO Filament Observations in Selected Lyman Lines
Authors: Schmieder, B.; Kucera, T.; Heinzel, P.; Vial, J. -C.
1998ASPC..150..205S Altcode: 1998IAUCo.167..205S; 1998npsp.conf..205S
No abstract at ADS

---------------------------------------------------------
Title: Evolution of the Magnetic Field and Chromospheric Fine
Structure in a Filament Channel
Authors: van Driel-Gesztelyi, L.; Mein, P.; Mein, N.; Schmieder,
B.; Malherbe, J. -M.; Aulanier, G.; Démoulin, P.; Deforest, C.;
Staiger, J.
1998ASPC..155..321V Altcode: 1998sasp.conf..321V
No abstract at ADS

---------------------------------------------------------
Title: Microflares and active filaments
Authors: Schmieder, B.; Fontenla, J.; Tandberg-Hanssen, E.
1998PAICz..88...63S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Second Advances in Solar Physics Euroconference:
Three-Dimensional Structure of Solar Active Regions
Authors: Alissandrakis, Costas E.; Schmieder, Brigitte
1998ASPC..155.....A Altcode: 1998sasp.conf.....A
No abstract at ADS

---------------------------------------------------------
Title: Non potentiality of coronal loops above active regions
Authors: Aulanier, G.; Schmieder, B.; Démoulin, P.; van
Driel-Gesztelyi, L.; Deforest, C.
1998ASPC..155..105A Altcode: 1998sasp.conf..105A
No abstract at ADS

---------------------------------------------------------
Title: A method for determining physical parameters in chromospheric
mottles
Authors: Tsiropoula, G.; Madi, C.; Schmieder, B.
1998ESASP.421..341T Altcode: 1998sjcp.conf..341T
No abstract at ADS

---------------------------------------------------------
Title: Filament Disparition Brusque and CME - September 25-26,
1996 Event
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Aulanier, G.;
Demoulin, P.; Martens, P. C. H.; Zarro, D.; Deforest, C.; Thompson,
B.; St. Cyr, C.; Kucera, T.; Burkepile, J. T.; White, O. R.; Hanaoka,
Y.; Nitta, N.
1998ASPC..150..366V Altcode: 1998IAUCo.167..366V; 1998npsp.conf..366V
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: New Perspectives on Solar Prominences
Authors: Webb, David F.; Schmieder, Brigitte; Rust, David M.
1998ASPC..150.....W Altcode: 1998npsp.conf.....W; 1998IAUCo.167.....W
No abstract at ADS

---------------------------------------------------------
Title: Helical Structure in an Eruptive Prominence Related to a CME
(SUMER, CDS, LASCO)
Authors: Kucera, T. A.; Poland, A. I.; Wiik, J. E.; Schmieder, B.;
Simnett, G.
1998ASPC..150..318K Altcode: 1998IAUCo.167..318K; 1998npsp.conf..318K
SOHO (SUMER/CDS) observed an eruptive prominence on May 1,1996,
associated with a CME observed by LASCO. We investigate the
physical conditions of this prominence in order to quantify velocity,
temperature, and density. SUMER spectra in Si IV and O IV lines are used
to obtain Doppler-shift images of the prominence. The prominence shows
large-scale red and blueshifted regions, revealing a large helical
structure with a global twist. In addition, fine structure analysis
shows multiple components in the line profile, suggesting integration
of many threads along the line-of-sight with a large dispersion of
velocities (∼150 km s-1).

---------------------------------------------------------
Title: Dynamics and Fine Structures in Quiescent Prominences (MSDP/Pic
du Midi, SOHO/SUMER and CDS)
Authors: Li, K.; Malherbe, J. -M.; Wiik, J. E.; Schmieder, B.; Roudier,
Th.; Kucera, T.; Poland, A.
1998ASPC..150...32L Altcode: 1998IAUCo.167...32L; 1998npsp.conf...32L
No abstract at ADS

---------------------------------------------------------
Title: Bright Points and Subflares in UV Lines and in X-Rays
Authors: Rovira, M.; Schmieder, B.; Demoulin, P.; Simnett, G. M.;
Hagyard, M. J.; Reichmann, E.; Tandberg-Hanssen, E.
1998msfc.rept.....R Altcode:
We have analysed an active region which was observed in Hα (MSDP),
UV lines (SMM/UVSP), and in X rays (SMM/HXIS). In this active region
there were only a few subflares and many small bright points visible in
UV and in X rays. Using an extrapolation based on the Fourier transform
we have computed magnetic field lines connecting different photospheric
magnetic polarities from ground-based magnetograms. Along the magnetic
inversion lines we find 2 different zones: 1. a high shear region
(less than 70 degrees) where subflares occur 2. a low shear region
along the magnetic inversion line where UV bright points are observed.

---------------------------------------------------------
Title: From one JOSO to another
Authors: Schmieder, Brigitte
1998ASSL..222...84S Altcode: 1998ream.conf...84S
No abstract at ADS

---------------------------------------------------------
Title: 3-D Modelling of a Filament Observed in Hα and with SOHO
Authors: Aulanier, G.; Schmieder, B.; Démoulin, P.; Mein, N.; van
Driel-Gesztelyi, L.; Mein, P.; Vial, J. C.; Deforest, C.
1998ESASP.417..217A Altcode: 1998cesh.conf..217A
No abstract at ADS

---------------------------------------------------------
Title: X-ray jets in a reversed polarity region and interplanetary
effects
Authors: Schmieder, B.; van Driel, L.; Mein, N.; Mein, P.; Willson,
R.; Raoult, A.
1998ESASP.421..157S Altcode: 1998sjcp.conf..157S
No abstract at ADS

---------------------------------------------------------
Title: A study of activity in interacting sunspot groups
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Hénoux, J. -C.
1998PAICz..88...13S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Velocity Fields of a Filament Region Observed with Ground-Based
Telescopes and from SOHO
Authors: Mein, P.; Schmieder, B.; Malherbe, J. -M.; Wiik, J. E.;
Engvold, O.; Brekke, P.; Zirker, J. B.; Poland, A. I.; Delaboudiniere,
J. -P.; Staiger, J.
1998ASPC..150..135M Altcode: 1998npsp.conf..135M; 1998IAUCo.167..135M
No abstract at ADS

---------------------------------------------------------
Title: Evolution of a reversed polarity active region NOAA 7912 in
the photosphere, the chromosphere and the corona.
Authors: van Driel-Gesztelyi, L.; Baranyi, T.; Mein, N.; Cader-Sroka,
B.; Rudawy, P.; Mein, P.; Rompolt, B.; Schmieder, B.; Malherbe,
J. -M.; Willson, R.; Kile, J. N.; Raoult, A.
1998joso.proc..103V Altcode:
The authors follow the evolution and activity of NOAA 7912, a reversed
polarity region, in the photosphere (Kitt Peak magnetograms and Debrecen
white-light photoheliograms), chromosphere (MSDP instrument mounted
on the German VTT at Tenerife), and the corona (Yohkoh/SXT, Nançay
radioheliograph and the VLA) between October 12-20, 1995. They find
that in spite of the high shear and creation of several mixed-polarity
regions through flux emergence, the flares in the group did not
exceed the M-class level. This might be due to the fact that the
highly inclined bipolar fields emerging in the following part of the
primary reversed dipole were relatively small and quickly "consumed"
by cancellation enhanced by sunspot motions. On the other hand, the
presence of high shear and minor fast-moving parasitic polarities in
NOAA 7912 was sufficient to produce eruptive events like X-ray jets
with important coronal and interplanetary effects.

---------------------------------------------------------
Title: Three-dimensional structure of solar active regions. 2nd
Euroconference ASPE97 (Advances in Solar Physics Euroconference 1997),
Preveza (Greece), 7 - 11 Oct 1997. Poster contributions.
Authors: Schmieder, B.; Alissandrakis, C.
1998joso.proc...78S Altcode:
All of the oral presentations of ASPE97 will be published in a separate
volume of the ASP Conference Series, while this volume contains the
poster presentations.

---------------------------------------------------------
Title: Filament observations with SOHO SUMER/CDS.
Authors: Schmieder, B.; Kučera, T.; Heinzel, P.; Vial, J. -C.
1998joso.proc..136S Altcode:
During a coordinated campaign between SOHO and ground-based instruments
a filament located close to the central meridian has been the target
of SUMER and CDS spectrometers on September 21, 1996.

---------------------------------------------------------
Title: X-Ray Jets and Their Radio Signatures at Metric and Centimeter
Wavelenths
Authors: van Driel-Gesztelyi, L.; Willson, R. F.; Kile, J. N.; Raoult,
A.; Klein, L.; Mein, N.; Rudawy, P.; Cader, B.; Rompolt, B.; Schmieder,
B.; Mein, P.; Malherbe, J. M.
1998ASPC..154..707V Altcode: 1998csss...10..707V
On October 19, 1995 at 10:30 UT and 17:00 UT, two semi-homologous X-ray
jets were observed with the Yohkoh/SXT from AR 7912, a region having a
reversed polarity group with vortex-like Hα fibril pattern and X-ray
loops. The jets appeared over a mixed magnetic polarity region in
the vicinity of the leading spot. The first event was also observed
with the Nancay radio heliograph at 167, 236, and 327 MHz. Type III
activity, indicating the presence of electron beams, superimposed on
a noise-storm was clearly visible. Type III activity first appeared
at 10:25 UT, coincident with the onset of the X-ray jet, at 164 MHz
and 236 MHz close to the storm position, and in the direction of the
X-ray jet. At 10:28:40 UT a new group of sources appeared eastward
of the former activity, which may correspond to another jet branch
along a more easterly path seen in the ohkoh} images. The second X-ray
jet event was also observed with the Very Large Array (VLA) at 6.2,
20.7, and 91.6 cm. For this event, VLA snapshot maps at 6.2 and 20.7
cm reveal low-brightness temperature changes in source structure at
the site of the X-ray jet during the preburst, impulsive, and decay
phases. The VLA 91.6 cm observations also show noise storm emission
above the active region but there is no clear temporal correlation
between this later X-ray jet and the impulsive decimetric bursts that
were observed during this period. Although the X-ray observations
show that the two jets had similar temperatures, emission measures,
speeds and trajectories they appear to have had dissimilar metric
responses to these events. This surprising result may question our
understanding of the process of electron beam acceleration in jets.

---------------------------------------------------------
Title: 3-D Magnetic Field Configuration Late in a Large Two-Ribbon
Flare
Authors: Moore, R. L.; Schmieder, B.; Hathaway, D. H.; Tarbell, T. D.
1997SoPh..176..153M Altcode:
We present Hα and coronal X-ray images of the large two-ribbon flare
of 25-26 June, 1992 during its long-lasting gradual decay phase. From
these observations we deduce that the 3-D magnetic field configuration
late in this flare was similar to that at and before the onset of
such large eruptive bipolar flares: the sheared core field running
under and out of the flare arcade was S-shaped, and at least one
elbow of the S looped into the low corona. From previous observations
of filament-eruption flares, we infer that such core-field coronal
elbows, though rarely observed, are probably a common feature of the
3-D magnetic field configuration late in large two-ribbon flares. The
rare circumstance that apparently resulted in a coronal elbow of the
core field being visible in Hα in our flare was the occurrence of a
series of subflares low in the core field under the late-phase arcade
of the large flare; these subflares probably produced flaring arches
in the northern coronal elbow, thereby rendering this elbow visible
in Hα. The observed late-phase 3-D field configuration presented
here, together with the recent sheared-core bipolar magnetic field
model of Antiochos, Dahlburg, and Klimchuk (1994) and recent Yohkoh
SXT observations of the coronal magnetic field configuration at
and before the onset of large eruptive bipolar flares, supports the
seminal 3-D model for eruptive two-ribbon flares proposed by Hirayama
(1974), with three modifications: (1) the preflare magnetic field is
closed over the filament-holding core field; (2) the preflare core
field has the shape of an S (or backward S) with coronal elbows; (3)
a lower part of the core field does not erupt and open, but remains
closed throughout flare, and can have prominent coronal elbows. In
this picture, the rest of the core field, the upper part, does erupt
and open along with the preflare arcade envelope field in which it
rides; the flare arcade is formed by reconnection that begins in the
middle of the core field at the start of the eruption and progresses
from reconnecting closed core field early in the flare to reconnecting
`opened' envelope field late in the flare.

---------------------------------------------------------
Title: Eruptive prominence and associated CME observed with SUMER,
CDS and LASCO (SOHO)
Authors: Wiik, J. E.; Schmieder, B.; Kucera, T.; Poland, A.; Brekke,
P.; Simnett, G.
1997SoPh..175..411W Altcode:
Observations of an eruptive prominence were obtained on 1 May 1996,
with the SUMER and CDS instruments aboard SOHO during the preparatory
phase of the Joint Observing Programme JOP12. A coronal mass ejection
observed with LASCO is associated temporally and spatially with this
prominence. The main objective of JOP12 is to study the dynamics of
prominences and the prominence-corona interface. By analysing the
spectra of Oiv and Siiv lines observed with SUMER and the spectra of
15 lines with CDS, Doppler shifts, temperatures and electron densities
(ratio of Oiv 1401 to 1399Å) were derived in different structures of
the prominence. The eruptive part of the prominence consists of a bubble
(plasmoid) of material already at transition region temperatures with
red shifts up to 100 km s-1 and an electron density of the
order of 1010cm-3. The whole prominence was very
active. It developed both a large helical loop and several smaller loops
consisting of twisted threads or multiple ropes. These may be studied
in the SUMER movie (movie 2). The profiles of the SUMER lines show a
large dispersion of velocities (±50 km s-1) and the ratio
of the Oiv lines indicates a large dispersion in electron density (3 x
109cm-3 to 3x 1011cm-3). The
CME observed by LASCO left the corona some tens of minutes before the
prominence erupted. This is evidence that the prominence eruptions are
probably the result of the removal of the restraining coronal magnetic
fields which are in part responsible for the original stability of
the prominence.

---------------------------------------------------------
Title: Magnetic reconnection driven by emergence of sheared magnetic
field.
Authors: Schmieder, B.; Aulanier, G.; Demoulin, P.; van
Driel-Gesztelyi, L.; Roudier, T.; Nitta, N.; Cauzzi, G.
1997A&A...325.1213S Altcode:
Recurrent subflares (Class C) were observed in the NOAA 7608 active
region on 27 October 1993. From multi-wavelength observations
(white-light, magnetic field, H-alpha, X-ray), obtained during a
coordinated campaign between Pic du Midi and Yohkoh, it appears that
these flares were double ribbon flares caused by new flux emergence. As
the flare begins, the X-ray emission observed with Yohkoh/SXT is
loop-shaped with the axis almost parallel to the magnetic inversion
line, while during the flare development, X-ray loops appear at the
location of the emerging flux. The extrapolation of the photospheric
magnetic field in a linear force-free field configuration allows
identification of the magnetic configuration given by the flares. The
Hα flare ribbons are located at the intersections of the computed
quasi-separatrice layers (QSLs) with the chromosphere. We show that
the initial loop-shaped X-ray emission region is in fact formed by
several smaller loops directed in a nearly orthogonal direction with
their feet anchored close to or in the Hα ribbons. During the flare
development there are X-ray loops which represent only one foot of
open or largescale magnetic loops. For the studied flares the puzzling
soft X-rays observations could only be understood with the help of Hα
and magnetic data combined with a modeling of the coronal magnetic
field. Further, from the deduced magnetic field topology, the width
of the QSLs and our present knowledge of 3-D magnetic reconnection,
we conclude that the flare was due to magnetic reconnection driven
by emergence of sheared magnetic field impacting in the pre-existing
coronal field.

---------------------------------------------------------
Title: Evidence of Magnetic Reconnection from Hα, Soft X-Ray and
Photospheric Magnetic Field Observations
Authors: Mandrini, C. H.; DÉmoulin, P.; BagalÁ, L. G.; Van
Driel-Gesztelyi, L.; HÉnoux, J. C.; Schmieder, B.; Rovira, M. G.
1997SoPh..174..229M Altcode:
A conventional view of magnetic reconnection is mainly based on
the 2-D picture of an X-type neutral point, or on the extension of
it to 3-D, and it is thought to be accompanied by flux transport
across separatrices (places where the field-line mapping is
discontinuous). This view is too restrictive when we realize the variety
of configurations that are seen flaring. We designed an algorithm,
called Source Method (SM), to determine the magnetic topology of
active regions (ARs). The observed photospheric field was extrapolated
to the corona using subphotospheric sources and the topology was
defined by the link between these sources. Hα flare brightenings
were found to be located at the intersection with the chromosphere
of the separatrices so defined. These results and the knowledge we
gained on the properties of magnetic field-line linkage, led us to
generalize the concept of separatrices to `quasi-separatrix layers'
(QSLs) and to design a new method (`quasi-separatrix layers method',
QSLM) to determine the magnetic topology of ARs. QSLs are regions where
the magnetic field-line linkage changes drastically (discontinuously
when they behave like separatrices) and the QSLM can be applied to ARs
where the photospheric field has been extrapolated using any kind of
technique. In this paper we apply the QSLM to observed flaring regions
presenting very different configurations and also to a decaying AR where
a minor phenomenon, like an X-ray bright point (XBP), is observed. We
find that the locations of flare and XBP brightenings are related to the
properties of the field-line linkage of the underlying magnetic region,
as expected from recent developments of 3-D magnetic reconnection. The
extrapolated coronal field lines representing the structures involved
in the analyzed events have their photospheric footpoints located
at both sides of QSLs. Our results strongly support the hypothesis
that magnetic reconnection is at work in various coronal phenomena,
ranging from the less energetic ones to large-scale eruptions.

---------------------------------------------------------
Title: Post-flare loops of May 16, 1981. Spectral analysis.
Authors: Gu, X. -M.; Ding, Y. -J.; Luo, Z.; Schmieder, B.
1997A&A...324..289G Altcode:
We present the analysis of Hα spectra obtained during a two-ribbon
flare observed on the solar disk on May 16, 1981 at Yunnan Observatory
with the Spectra-Spectroheliograph (SSHG). The complicated asymmetric
profiles produced by the post-flare loops overlying flare ribbons are
analysed with a fast method based on the cloud model method. This
method takes into account the bright background of the loops and
allows computation of the physical quantities of loops crossed by the
slit: velocity field, optical thickness, source function and Doppler
width. Using the scanning spectra of the region, we obtain 2-D maps
of these parameters. The validity of the method used is compared
with other methods and the sensitivity of parameters to solution
is discussed in details. The results obtained with this method are
compared with those given by Heinzel et al. (1992SPh...139...81H)
using a fully non-LTE approach.

---------------------------------------------------------
Title: Determination of physical parameters in dark mottles.
Authors: Tsiropoula, G.; Schmieder, B.
1997A&A...324.1183T Altcode:
The application of the cloud model to measurements of the contrast as
a function of wavelength in the Hα line has recently enabled us to
derive numerical values for various parameters (such as velocity, source
function, Doppler width and optical depth) of dark mottles observed near
the center of the solar disk. The values of these parameters are used
together with the calculations of Poland et al. (1971SPh....18..391P)
and Yakovkin and Zel'dina (1975SPh....45..319Y) in order to determine
the physical conditions in these structures. Thus population densities
at levels 1, 2, 3 (N_1_, N_2_, N_3_), total particle density of hydrogen
N_H_, electron density N_e_, electron temperature T_e_, gas pressure,
total column mass, mass density and degree of hydrogen ionization
can be determined. The values obtained are comparable with estimates
obtained for spicules and mottles by different authors in the past and,
furthermore, offer the prospect of putting observational constraints
on non-LTE two-dimensional modelling of dark mottles observed in the
Hα line which is currently in progress.

---------------------------------------------------------
Title: Post-Flare Loops of 26 June 1992 - IV. Formation and Expansion
of Hot and Cool Loops
Authors: Van Driel-Gesztelyi, L.; Wiik, J. E.; Schmieder, B.; Tarbell,
T.; Kitai, R.; Funakoshi, Y.; Anwar, B.
1997SoPh..174..151V Altcode:
Observations of the post-flare loops after the X3.9 flare which occurred
on 25 June, 1992 at 20:11 UT by the Yohkoh/SXT in X-rays, as well as
in Hα obtained at 5 different observatories, have provided a unique,
longest ever, set of data for a study of the relationship between the
hot and cool post-flare loops as they evolve. At any given time, the
altitude difference between the hot X-ray loops of 6-7× 106
K and the cool Hα loops of 1.5× 104 K is related to the
expansion rate of the loop systems and their cooling time. Therefore,
measurements of the expansion rate and relative height of hot and
cool loops can provide direct observational values for their cooling
times. We measured the altitude of hot and cool loops for 15 and 19
hours, respectively, and found that the cooling time increased as the
density of the loops decreased. We found a reasonably good agreement
between the observed cooling times and those obtained from model
calculations, although the observed values were always somewhat longer
than the theoretical ones. Taking into account evolutionary effects,
we also found similar shapes and configurations of hot and cool loops
during the entire observing period and confirmed that, at any time,
hot loops are at higher altitude than cool loops, suggesting that cool
loops indeed evolve from hot loops. These results were used to check
the validity of the reconnection model.

---------------------------------------------------------
Title: The Postflare Loops and the Nearby Active Chromosphere of
1992 June 26
Authors: Malherbe, J. -M.; Tarbell, T.; Wiik, J. E.; Schmieder, B.;
Frank, Z.; Shine, R. A.; van Driel-Gesztelyi, L.
1997ApJ...482..535M Altcode:
The main objective of this paper is to present a quantitative study
of the dynamics of the evolution of Hα postflare loops developed
after a large solar flare and the processed videos produced from the
observations. The high spatial resolution of the Swedish Vacuum Solar
Telescope (SVST) at La Palma has provided a unique set of data for such
an event. A Gaussian fitting method is proposed to derive intensities
and Doppler shifts from observations taken at three wavelengths (Hα
center and Hα +/- 0.07 nm). Moving condensations or “blobs” of cold
material provide transverse velocities, which, together with the radial
component, enable us to derive their velocity vector magnitude. Plasma
velocities are around free-fall velocities near the top of the loops
but are significantly smaller close to their footpoints, suggesting
a deceleration mechanism. The loops are anchored in the chromosphere,
which shows tremendous activity in the active region and in the nearby
“quiet Sun.” Spicules and ejection of plasmoids are also observed
at the limb.

---------------------------------------------------------
Title: Evolution of a Delta Group in the Photosphere and Corona
Authors: Van Driel-Gesztelti, L.; Csepura, G.; Schmieder, B.; Malherbe,
J. -M.; Metcalf, T.
1997SoPh..172..151V Altcode: 1997ESPM....8..151V
We present a study of the evolution of NOAA AR 7205 in the photosphere
and corona, including an analysis of sunspot motions, and show the
evolutionary aspects of flare activity using full-disc white-light
observations from Debrecen, vector magnetograms from Mees Observatory,
Hawaii, and Yohkoh soft X-ray observations. NOAA AR 7205 was born on
the disc on 18 June, 1992. During the first 3 days it consisted of
intermittent minor spots. A vigorous evolution started on 21 June when,
through the emergence and merging (v ≈ 100-150 m s-1) of
several bipoles, a major bipolar sunspot group was formed. Transverse
magnetic fields and currents indicated the presence of shear (clockwise
twist) already on 21 June (with α ≈ 0.015 Mm-1). On 23
June, new flux emerged in the trailing part of the region with the
new negative polarity spot situated very close to the big positive
polarity trailing spot of the main bipole. The secondary bipole seemed
to emerge with high non-potentality (currents). From that time the AR
became the site of recurrent flare activity. We find that all 14 flares
observed with the Yohkoh satellite occurred between the highly sheared
new bipole and the double-headed principal bipole. Currents observed
in the active region became stronger and more extended with time. We
propose that the currents have been (i) induced by sunspot motions and
(ii) increased by non-potential flux emergence leading to the occurrence
of energetic flares (X1.8 and X3.9). This observation underlines the
importance of flare analysis in the context of active region evolution.

---------------------------------------------------------
Title: Optical and Radio Spectral Analysis of a Recurrent Surge
Authors: Kotrč, Pavel; Schmieder, Brigitte; Karlický, Marian;
Heinzel, Petr
1997SoPh..172..199K Altcode: 1997ESPM....8..199K
Coordinated observations obtained at Meudon (MSDP) and at Ondřejov
provide surge spectra in optical range (Hα, Hβ, Hγ, Hµ, Ca H and
K lines) and in radio range. The MSDP data allowed us to follow the
time evolution of the surge. The spectra of Balmer lines were used to
derive the electron density of the expelled cool material. The radio
bursts indicate that the acceleration of electrons took place in the
low and dense atmosphere, giving a good argument for a reconnection
near the transition region.

---------------------------------------------------------
Title: 3-D Magnetic Field Configuration Late in a Large Two-Ribbon
Flare
Authors: Moore, R. L.; Schmieder, B.; Hathaway, D. H.; Tarbell, T. D.
1997SPD....28.0157M Altcode: 1997BAAS...29R.889M
We present H-alpha and coronal X-ray images of the large two-ribbon
flare of 25/26 June 1992 during its long-lasting gradual decay
phase. From these observations we deduce that the 3-D magnetic field
configuration late in this flare was similar to that at and before the
onset of such large eruptive bipolar flares: the sheared core field
running under and out of the flare arcade was S-shaped, and at least one
elbow of the S looped into the low corona. From previous observations
of filament-eruption flares, we infer that such core-field coronal
elbows, though rarely observed, are probably a common feature of the
3-D magnetic field configuration late in large two-ribbon flares. The
rare circumstance that apparently resulted in a coronal elbow of the
core field being visible in H-alpha in our flare was the occurrence
of a series of subflares low in the core field under the late-phase
arcade of the large flare; these subflares probably produced flaring
arches in the northern coronal elbow, thereby rendering this elbow
visible in H-alpha. The observed late-phase 3-D field configuration
presented here, together with the recent sheared-core bipolar magnetic
field model of Antiochos, Dahlburg, and Klimchuk (1994) and recent
Yohkoh SXT observations of the coronal magnetic field configuration
at and before the onset of large eruptive bipolar flares, supports the
seminal 3-D model for eruptive two-ribbon flares proposed by Hirayama
(1974), with three modifications: (1) the preflare magnetic field is
closed over the filament-holding core field; (2) the preflare core
field has the shape of an S (or backward S) with coronal elbows; (3)
a lower part of the core field does not erupt and open, but remains
closed throughout flare, and can have prominent coronal elbows. In
this picture, the rest of the core field, the upper part, does erupt
and open along with the preflare arcade envelope field in which it
rides; the flare arcade is formed by reconnection that begins in the
middle of the core field at the start of the eruption and progresses
from reconnecting closed core field early in the flare to reconnecting
"opened" envelope field late in the flare.

---------------------------------------------------------
Title: NLTE Analysis of SUMER Filament Observations on SOHO
Authors: Heinzel, P.; Schmieder, B.; Vial, J. -C.
1997ESASP.404..427H Altcode: 1997cswn.conf..427H
No abstract at ADS

---------------------------------------------------------
Title: Solar Magnetic Field Events related to CMEs observed with SOHO
(MDI, EIT, SUMER, LASCO)
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Wiik, J. E.; Thompson,
B.; de Forest, C.; Saint Cyr, C.; Vial, J. -C.; Nitta, N.; Simnett, G.
1997IAUJD..19E..42S Altcode:
We shall present two CMEs observed by LASCO during the minimum of
activity of the Sun. These are associated with filament disparitions
brusques (DB). CME and DB definitively seem to be consequences of global
magnetic field instability, which causes reconnection of pre-existing
field lines in the corona. We shall demonstrate how cancelling flux
and converging magnetic field in photosphere may destabilize coronal
streamers overlying one or two filament channels.

---------------------------------------------------------
Title: Prominence Activity Related to CME Observed by SOHO, YOHKOH
and Ground-Based Observatories
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Wiik, J. E.; Kucera,
T.; Thompson, B.; de Forest, C.; Saint Cyr, C.; Simnett, G. M.
1997ESASP.404..663S Altcode: 1997cswn.conf..663S
No abstract at ADS

---------------------------------------------------------
Title: Two dimensional distribution of physical parameters in dark
mottles assuming constant and non-constant source function
Authors: Tsiropoula, G.; Madi, G.; Christopoulou, E.; Alissandrakis,
G.; Schmieder, B.; Preka-Papadema, P.
1997jena.confE..60T Altcode:
Observations of a rosette region consisting of several dark mottles
located almost at the solar disk centre (N5, W5) were made with the
Multichannel Double Pass (MSDP) spectrograph mounted on the 50 cm
“Tourelle” refractor of the Pic du Midi Observatory, on June 17,
1986. The MSDP having 11 channels provides at every point of the field
of view the profile of the H-alpha line, which is reconstructed from
11 values. The observed contrast profiles of the dark features as a
function of the wavelength are used in terms of Beckers' cloud model
(e.g. assuming that the source function is constant throughout the
feature) in order to derive 4 parameters: the line-of-sight velocity,
the optical depth at line centre, the Doppler width and the source
function. The computation of the four parameters was carried out by an
iterative least square procedure for non linear functions. Allowing
the source function to have a parabolic variation with the optical
depth and using the same iteration procedure the source function at
the centre of the feature and the source function variation factor
are determined. Comparison of the values of the physical parameters
derived under these two different assumptions concerning the source
function is performed. These values are also compared with the values
obtained from multilevel non-LTE models.

---------------------------------------------------------
Title: Coordinated Observations of Prominences with SUMER/CDS and
Ground Observatories
Authors: Wiik, J. E.; Schmieder, B.; Kucera, T.; Poland, A.
1997ASPC..118..278W Altcode: 1997fasp.conf..278W
An international campaign for the observation of prominences
and filaments was successfully accomplished between June 3 and
9 1996. Several ground observatories took part in the campaign
which included the space observatories SOHO and Yohkoh. The main
objective of this campaign was to study the dynamics of prominences
and the prominence-corona interface, the formation of filaments and
the fine structures at different temperatures. We will reported on
two Joint Observing Programmes of SUMER and CDS aboard SOHO (JOP 12
and JOP 17), which have been achieved. Finally we will present as an
exemple a prominence observed on May 1, 1996 during the tests of the
programme JOP 12. This prominence was associated with a CME (observed
with LASCO). Very active parts with Dopplershifs up to +/- 36kms(-1)
were measured in the SUMER spectra of the prominence, indicating the
presence of twisted ropes during the eruption. Mean electron densities
have spatial and temporal dispersion of one order of magnitude (10(9)
- 10(10) cm(-3) ).

---------------------------------------------------------
Title: Magnetic reconnection driven by an emerging flux.
Authors: Aulanier, G.; Démoulin, P.; Schmieder, B.; Malherbe, J. M.;
van Driel-Gesztelyi, L.; Roudier, T.
1997joso.proc...51A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Analysis of long duration flares
Authors: Harra-Murnion, L. K.; Plunkett, S. P.; Helsdon, S. F.;
Phillips, K. J. H.; van Driel-Gesztelyi, L.; Schmieder, B.; Rompolt,
B.; Akioka, M.
1997AdSpR..20.2333H Altcode:
Yohkoh has observed many long duration events permitting a statistical
study of the properties of these interesting events. We have selected
ten flares for analysis which have durations between 5 and 20 hours, and
size ranging from C to X GOES class. Employing the Soft X-ray Telescope,
the Bragg Crystal Spectrometer, GOES spacecraft, and ground-based
H_alpha data, we examine the morphology, temperature, emission measure,
location of the hard X-ray source, non-thermal velocities and upflows
of the plasma at different stages in the flare development. Our results
are used to address the question of the energy source that maintains the
hot plasma at temperatures of several million degrees for many hours.

---------------------------------------------------------
Title: 1st Advances in Solar Physics Euroconference: Advances in
the Physics of Sunspots
Authors: Schmieder, B.; del Toro Iniesta, J. C.; Vazquez, M.
1997ASPC..118.....S Altcode: 1997fasp.conf.....S
No abstract at ADS

---------------------------------------------------------
Title: Dynamics and evolution of the post-flare loops of June 1992
Authors: Wiik, J. E.; van Driel-Gesztely, L.; Schmieder, B.;
Heinzel, P.
1997AdSpR..20.2345W Altcode:
Observations in X-rays (Yohkoh/SXT) and in Hα of a system of post-flare
loops which developed after a flare on 25 June 1992 provide a unique
set of data for a study of the relationship between the hot and cool
post-flare loops as they evolve. Through a study of the magnetic
configuration in which the flare occurred, we are able to reconstruct
the true, 3D geometry of the loops. We derive the bulk-flow velocities
along the loop as a function of height using Doppler velocities and
the results from the loop reconstruction. We also provide a set of
relative altitude data. These results are used to check the validity
of the reconnection model in the frame of the cooling time needed to
cool X-ray loops to Hα temperature.

---------------------------------------------------------
Title: Advances in the physics of sunspots. Poster contributions. 1st
ASPE Meeting, Puerto de la Cruz, Tenerife (Spain), 2 - 6 Oct 1996.
Authors: Schmieder, B.
1997joso.proc...47S Altcode:
The invited reviews and contributed papers are published in the
Astronomical Society of the Pacific Conference Series, Vol. 118.

---------------------------------------------------------
Title: Post-flare loops in the chromosphere and corona.
Authors: van Driel-Gesztelyi, L.; Wiik, J. E.; Schmieder, B.
1997ASIC..494...85V Altcode: 1997topr.conf...85V
Post-flare loops, which may last for several hours during the gradual
phase of powerful flares, can provide spectacular limb events during
solar eclipses. According to models, on-going magnetic reconnection
keeps creating new loops at an ever-increasing altitude. The newly
formed hot loops can cool down to chromospheric temperatures quickly,
in a few minutes, or slowly, over a few hours, depending on their
density. A good test of the model is to measure the altitude difference
between loops observed at different wavelengths which show the loops
at different stages of the cooling process.

---------------------------------------------------------
Title: "Prominences, filaments and chromospheric activity" June 1996
campaign with SOHO, YOHKOH and Wrocław.
Authors: Wiik, J. E.; Rudawy, P.; Schmieder, B.; Kucera, T.; Rompolt,
B.; Poland, A.
1997joso.proc...93W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Flows Through the Magnetically Structured Solar Atmosphere
Authors: Schmieder, B.
1997LNP...489..139S Altcode: 1997shpp.conf..139S
The upper solar atmosphere until three solar radii is controlled by the
magnetic field. The plasma β (P kin/P magn)
is decreasing with increasing altitude in the low corona but is
already less than unity in the middle chromosphere. The dynamics of the
chromosphere and the transition region are driven by magnetic effects,
even in the "quiet" Sun. We will review some promising research
programs concerning steady flows and oscillatory phenomena in the
small scale structures, mainly based on new two-dimensional spectral
diagnostics. The filamentary behaviour of the solar atmosphere may
be the key to understanding basic problems like coronal heating. The
importance of the chromospheric network, plages and penumbra is
emphasized by the fact that they represent footpoints of coronal
loops. Largescale coronal structures (streamers, jets, post-flare loops,
arcades) are linked to photospheric and chromospheric events and give
a three-dimensional view of the atmosphere.

---------------------------------------------------------
Title: 3D Magnetic Reconnection at an X-Ray Bright Point
Authors: Mandrini, C. H.; Démoulin, P.; Van Driel-Gesztelyi, L.;
Schmieder, B.; Cauzzi, G.; Hofmann, A.
1996SoPh..168..115M Altcode:
On May 1, 1993, a flaring X-ray bright point (XBP) was observed for
about 16 hours in the old, disintegrating, bipolar active region (AR)
NOAA 7493. During this period, a minor magnetic bipole (1020
Mx) emerged in the region. We have found observational evidence showing
that the XBP brightenings were due to magnetic reconnection between
the new bipole and pre-existing plage fields. The aim of the present
work is to substantiate with magnetic modelling what has been shown
by the observations. For this purpose we extrapolate the observed
photospheric magnetic fields in the linear force-free approximation
and follow its evolution during the lifetime of the XBP. From the
computed coronal field lines we determine the location of regions of
drastic change in field-line linkage, called `quasi-separatrix layers'
or QSLs. QSLs are open layers that behave physically like separatrices:
the break down of ideal magnetohydrodynamics and the release of free
magnetic energy may occur at these locations when their thickness
is small enough. The extrapolated field lines, with photospheric
footpoints on both sides of QSLs, match the observed chromospheric and
coronal structures (arch filament system, XBP and faint X-ray loops
(FXL)). We study also the evolution of the width of the QSL located
over the new negative polarity pore: the calculated QSL is very thin
(typically less than 100 m) during the lifetime of the XBP, but becomes
much thicker (≥ 104 m) after the XBP has faded. Furthermore
we show that peaks in X-ray brightness propagate along the FXL with a
velocity of ≈ 670 km s-1, starting from the XBP location,
implying that the energy is released where the emerging bipole impacts
against pre-existing coronal loops. We discuss the possible mechanism
of energy transport and conclude that the energy is conducted to the
remote footpoints of the FXL by a thermal front. These results strongly
support the supposition that the XBP brightness and flaring are due
to the interaction of different flux systems, through 3D magnetic
reconnection, at QSLs.

---------------------------------------------------------
Title: Differential Magnetic Field Shear in an Active Region
Authors: Schmieder, B.; Demoulin, P.; Aulanier, G.; Golub, L.
1996ApJ...467..881S Altcode:
The three-dimensional extrapolation of magnetic field lines from a
magneto gram obtained at Kitt Peak allows us to understand the global
structure of the NOAA active region 6718, as observed in X-rays with the
Normal Incidence X-ray Telescope (NIXT) and in Hα with the Multichannel
Subtractive Double Pass spectrograph (MSDP) in Meudon on 1991 July
11. This active region was in a quiet stage. Bright X-ray loops connect
plages having field strengths of ∼300 G, while Hα fibriles connect
penumbrae having strong spot fields to the surrounding network. Small,
intense X-ray features in the moat region around a large spot, which
could be called X-ray-bright points, are due mainly to the emergence of
magnetic flux and merging of these fields with surrounding ones. A set
of large-scale, sheared X-ray loops is observed in the central part
of the active region. Based on the fit between the observed coronal
structure and the field configurations (and assuming a linear force-free
field), we propose a differential magnetic field shear model for this
active region. The decreasing shear in outer portions of the active
region may indicate a continual relaxation of the magnetic field to
a lower energy state in the progressively older portions of the AR.

---------------------------------------------------------
Title: Post-Flare Loops of 26 June 1992, III
Authors: Wiik, J. E.; Schmieder, B.; Heinzel, P.; Roudier, T.
1996SoPh..166...89W Altcode:
Post-flare loops were observed on June 26, 1992 in the Hα line
with the Multichannel Subtractive Double-Pass spectrograph (MSDP)
on Pic-du-Midi and with the Swedish telescope on La Palma. The highly
dynamic loops are inhomogeneous (blobs). The cool loops were observed
10-12 hours after the X 3.9 class flare which had a maximum on June
25 at 20∶11 UT. From 2D images obtained with the MSDP on June 26 we
derive Hα intensities and Doppler velocities of the loop plasma. Using
a geometrical reconstruction technique we show that these loops are
mainly perpendicular to the solar surface and have the shape of a
dipole magnetic configuration. We derive the bulk-flow velocities along
the loop as a function of height using the Doppler velocities and the
results from the loop reconstruction. Where the Doppler velocities are
too small, we derive the bulk-flow velocities from the displacements
of the falling blobs. We discuss existing deviations from free-fall
velocity in the lower parts of the loops.

---------------------------------------------------------
Title: Post-Flare Loops of 26 June 1992, II
Authors: Schmieder, B.; Heinzel, P.; Van Driel-Gesztelyi, L.; Lemen,
J. R.
1996SoPh..165..303S Altcode:
We observed the large post-flare loop system, which developed after the
X 3.9 flare of 25 June 1992 at 20∶11 UT, in Hα with the Multichannel
Subtractive Double Pass Spectrograph at Pic-du-Midi and in X-rays with
the it Yohkoh/SXT instrument. Following the long-term development of
cool and hot plasmas, we have determined the emission measure of the
cool plasma and, for the first time, the temporal evolution of the
hot-loop emission measure and temperature during the entire gradual
phase. Thus, it was possible to infer the temporal variation of electron
densities, leading to estimates of cooling times. A gradual decrease of
the hot-loop emission measure was observed, from 4 × 1030
cm−5 at 23∶00 UT on 25 June 1992 to 3 × 1028
cm−5 at 13∶10 UT on 26 June 1992. During the same period,
the temperature decreased only slowly from 7.2 to 6.0 × 106
K. Using recent results of NLTE modeling of prominence-like plasmas,
we also derive the emission measure of cool Hα loops and discuss
their temperature and ionisation degree. During two hours of Hα
observations (11-13 hours after the flare) the averaged emission
measure does not show any significant change, though the amount
of visible cool material decreases and the volume of the loops
increases. The emission measure in Hα, after correction for the
Doppler-brightening effect, is slightly lower than in soft X-rays. Since
the hot plasma seems to be more spatially extended, we arrive at
electron densities in the range ninfesupho≤
ninfesupcool∼ 2 × 1010
cm−3 at the time of the Hα observations.

---------------------------------------------------------
Title: Subflares and surges in AR 2744 during the Solar Maximum
Mission.
Authors: Schmieder, B.; Rovira, M.; Simnett, G. M.; Fontenla, J. M.;
Tandberg-Hanssen, E.
1996A&A...308..957S Altcode:
Active region NOAA 2744, which was at S25, had its central meridian
passage on Oct 23 1980 and was relatively quiet according to Hα, UV
and X-ray observations made by the Solar Maximum Mission (SMM). The
region was also observed by the Marshall Space Flight Center (MSFC)
vector magnetograph. During its disk passage only subflares and surges
were detected. Their locations appeared to be governed by the magnetic
topology. On October 21 a miniflare occurred close to the separator
between the two main sunspots. On October 22 the emergence of a small
region of parasitic polarity in the existing magnetic field appeared
to be responsible for three subflares and subsequent surges. We discuss
the energy budget for plasmas at temperatures in the 10^4^K, 10^5^K and
10^6^K ranges in the context of surge-trigger mechanisms. On October
21 the energy deposition driving the surges did not produce a high
temperature plasma. By October 22 the active region had evolved and the
surges were now associated with some high temperature plasma. However,
the energy radiated at transition region temperatures would be larger
than that estimated in X-rays depending on the dilution factor. This
would imply a continuous influx of energy in order to sustain the
long duration surge (30min) rather than a simple, impulsive energy
input. If the electron density in the 10^4^-10^5^K plasma is taken
as ~10^12^cm^-3^ the diameter of individual surge loops should only
be ~40km. The relevance of our results to (a) reconnection and (b)
gradient pressure driven models for surges is discussed.

---------------------------------------------------------
Title: Chromospheric ejections and their signatures in X-ray observed
by YOHKOH
Authors: Schmieder, B.; Mein, N.; Shibata, K.; van Driel-Gesztelyi,
L.; Kurokawa, H.
1996AdSpR..17d.193S Altcode: 1996AdSpR..17..193S
Surges, or condensations of chromospheric material, are commonly
observed in active regions when new emerging magnetic flux (EMF)
occurs. In order to study EMF-related phenomena in the corona, observing
campaigns were organized with the Yohkoh X-ray satellite and ground
based observatories. EMFs could be detected in magnetograms made in
Potsdam and Hawaii, surge and arch filament system (AFS) events (on
Oct 7 1991, May 1 1993, respectively) with the Multichannel Subtractive
Double Pass instruments operating at Meudon and on the Canary Islands
and with the Hida telescope at Kyoto University. Bright X-ray loops
coincident with chromospheric surge activity were detected in the high
resolution Yohkoh SXT images. We also found coincident brightness
variations between an X-ray bright point (XBP) and the underlying
chromospheric plage related to EMF. We interpret the appearance of
AFS as condensation of material among magnetic field lines, the X-ray
bright points as the result of a magnetic reconnection process, and
surges as ejection of cold plasma bubbles squeezed between field lines
as a result of reconnection.

---------------------------------------------------------
Title: Coordinated SPDE rocket, YOHKOH and ground observations of
an emerging flux region and a filament
Authors: Damé, L.; Martic, M.; Brown, W. A.; Bruner, M. E.; Strong,
K.; Suematsu, Y.; Tsuneta, S.; Schmieder, B.
1996AdSpR..17d.189D Altcode: 1996AdSpR..17..189D
During the first flight of the Solar Plasma Diagnostic Experiment
(SPDE), May 12, 1992, we obtained UV filtergrams at high resolution
(full Sun 0.82” spatial resolution in the 160 nm continuum, the
CIV lines and Lyman alpha) with the Ultraviolet Filtergrap Camera
(UVFC). Closely coordinated observations were obtained with the Soft
X-ray Telescope (SXT) of the Yohkoh satellite and from dedicated ground
programs in particular at Sacramento Peak, La Palma and Pic-du-Midi
observatories. With this unique set of data we cover the solar
atmosphere as a whole, from the temperature minimum to the high corona
with essential steps in the chromosphere and transition region. After
the necessary calibrations of the data set, we present the first results
of the multitemperature development of an emerging flux region and of
a filament that rapidly changed right during the rocket short lifetime.

---------------------------------------------------------
Title: Structure and evolution of post-flare loops: analysis of
YOHKOH and MSDP observations
Authors: Schmieder, B.; Heinzel, P.; Wiik, J. E.; Lemen, J.; Hiei, E.
1996AdSpR..17d.111S Altcode: 1996AdSpR..17..111S
Using coordinated observations of the June 26 1992 post-flare loops
(Yohkoh-SXT and MSDP at Pic-du-Midi), we have analyzed the physical
conditions in both hot and cool loops and studied their spatial
structure and temporal evolution. Coalignment of high-resolution images
from SXT and MSDP indicates that the cool Hα loops are located just
below the hot ones and that the whole loop system grows in time with
a velocity 1.4 km s^-1. The temperature of hot loops as derived from
SXT data amounts to 5 x 10^6 K, while the cool loops have temperatures
around 10^4 K. The electron density of hot loops was estimated from
SXT emission-measure analysis to 7 x 10^9 cm^-3, while Hα integrated
intensity gives an electron density in cool loops of 2.2 x 10^10
cm^-3. With these plasma parameters we have solved the energy equation
in order to estimate the cooling time. The basic result of this work
is that the cooling time is comparable to the characteristic growing
time of the loop system (~ 1500 - 2000 sec), which is in agreement
with the scenario of the post-flare loop system development.

---------------------------------------------------------
Title: High resolution Lyalpha images obtained with the transition
region camera (TRC): a comparison with Hα observations
Authors: Wiik, J. E.; Foing, B. H.; Martens, P.; Fleck, B.;
Schmieder, B.
1996AdSpR..17d.105W Altcode: 1996AdSpR..17..105W
Comparing high spatial resolution (~ 1”) images observed in Lyalpha
with the Transition Region Camera (TRC) and in Hα at Sacramento Peak
and Meudon Observatories, we notice that some structures are well
correlated in the two lines (plages), while others are less correlated
(chromospheric network, filaments). This is an indication of the
inhomogeneous distribution of physical parameters in these structures.

---------------------------------------------------------
Title: Observations and Analysis of Surges in Chromosphere and
Lower Corona
Authors: Kotrc, P.; Schmieder, B.; Karlický, M.; Heinzel, P.
1996RoAJ....6...69K Altcode:
No abstract at ADS

---------------------------------------------------------
Title: X-Ray Bright Point Flares Due to Magnetic Reconnection
Authors: Van Driel-Gesztelyi, L.; Schmieder, B.; Cauzzi, G.; Mein,
N.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, P.; Staiger, J.
1996SoPh..163..145V Altcode:
Ground-based optical observations coordinated with Yohkoh/SXT X-ray
observations of an old, disintegrating bipolar active region AR NOAA
7493 (May 1, 1993) provided a multiwavelength data base to study
a flaring `active region' X-ray bright point (XBP) of about 16 hr
lifetime, and the activity related to it in different layers of the
solar atmosphere. The XBP appeared to be related to a new minor bipole
of about 1020 Mx. Superposed on a global evolution of soft
X-ray brightness, the XBP displayed changes of brightness, lasting for
1-10 min. During the brightenings the XBP apparently had a spatial
structure, which was (tiny) loop-like rather than point-like. The
X-ray brightenings were correlated with chromospheric activity: (i)
brightenings of underlying chromospheric faculae, and (ii) appearance
of strong turbulent velocities in the arch filament system. We propose
that the XBP brightenings were due to reconnection of the magnetic
field lines (sketched in 3D) between the new bipole and a pre-existing
plage field induced by the motion of one of the new pores (v = 0.2
km s−1) towards the plage, and that the XBP itself was
a reconnected hot loop between them.

---------------------------------------------------------
Title: Hot and Cool Post-Flare Loops: Formation and Dynamics
Authors: Schmieder, B.; Heinzel, P.; van Driel-Gesztelyi, L.; Wiik,
J. E.; Lemen, J.
1996mpsa.conf..211S Altcode: 1996IAUCo.153..211S
No abstract at ADS

---------------------------------------------------------
Title: Reconexión magnética en una región activa en decaimiento
Authors: Mandrini, C. H.; Démoulin, P.; van Driel-Gesztelyi, L.;
Schmieder, B.; Bagalá, L. G.; Rovira, M. G.
1996BAAA...40....5M Altcode:
Se han obtenido observaciones desde Tierra (Hα y magnetogramas)
coordinadas con el Soft X-ray Telescope (SXT), a bordo del satélite
japonés Yohkoh, de una región activa bipolar en decaimiento. Estos
datos constituyen la base para el estudio de un punto brillante en rayos
X (PBX) y de la actividad relacionada con el mismo en distintas capas
de la atmósfera solar. Las observaciones muestran que el PBX está
relacionado con la aparición de un bipolo menor (~ 1020 Mx)
y que su abrillantamiento continuo, así como sus aumentos de brillo
esporádicos (“fulguraciones"), son el resultado de la reconexión
entre el pequeño arco emergente (visto en Hα como un sistema de
filamentos arqueados, SFA) y arcos mayores asociados al campo facular
preexistente. Se ha extrapolado el campo magnético observado en la
aproximación libre de fuerzas lineal y se ha seguido su evolución
a lo largo de la vida del PBX. Se ha calculado la posición de las
cuasiseparatrices (CSs) a partir del campo modelado. Las líneas de
campo extrapoladas, cuyas bases fotosféricas se encuentran a ambos
lados de las CSs, están de acuerdo con las estructuras cromosféricas
y coronales observadas. Se ha calculado el espesor de la CD ubicada
a lo largo de la polaridad negativa emergente, encontrándose que su
variación está de acuerdo con la evolución de la intensidad del PBX;
la CS es muy delgada durante la vida del PBX (~ 100 m), mientras que
su espesor aumenta considerablemente (&gt;= 10^4 m) cuando el PBX
desaparece de las imágenes del SXT. Estos resultados señalan que
el abrillantamiento y las “fulguraciones" de este PBX se deben al
proceso de reconexión en 3D que tiene lugar en las CSs.

---------------------------------------------------------
Title: Relative Altitude of Hot and Cool Post-Flare Loops
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Wiik, J. E.; Tarbell,
T.; Heinzel, P.; Kitai, R.; Funakoshi, Y.; Anwar, B.
1996ASPC..111..359V Altcode: 1997ASPC..111..359V
The authors collected a unique set of data obtained simultaneously at
4 different ground based observatories and with the Yohkoh satellite
to study the relationship between hot X-ray and cool Hα post-flare
loops as they evolved during the long gradual phase of the X3.9 flare
which occurred on 25 June 1992. They found reasonably good agreement
between the computed 'theoretical' cooling times and the 'observed'
cooling times derived from the relative altitudes of hot and cool
loops. Taking into account evolutionary effects, the authors also found
similar shape and configuration of hot and cool loops during the entire
observing period and confirmed that at any time hot loops are at higher
altitude than cool loops, suggesting that cool loops indeed descend
from hot loops. The results provide support for the reconnection model.

---------------------------------------------------------
Title: Signatures of New Emerging Flux in the Solar Atmosphere
Authors: Schmieder, B.; Malherbe, J. M.; Mein, P.; Mein, N.; van
Driel-Gesztelyi, L.; Roudier, T.; Nitta, N.; Harra-Murnion, L. K.
1996ASPC..111...43S Altcode: 1997ASPC..111...43S
The emergence of new flux in the low atmosphere leads to magnetic
reconnection of field lines. In a stable phase the phenomenon is
observed in the chromosphere by the formation of dark filaments (arch
filament system, AFS). The authors show how bright loops visible in soft
X-rays are co-aligned with the AFS. Different types of events appear
as the released energy increases. With less energetic phenomena than
flares one observes surges, jets or X-ray bright points, according
to the configuration of the field lines (open/closed). A low-level
reconnection process is detectable as an X-ray bright point. If
the energy is ≡1028ergs cm-3, one observes
subflares. The authors document their statement by showing examples
observed in coordinated observations obtained with the MSDP (Pic du
Midi and Tenerife) and Yohkoh/SXT and BCS for the events occurring on
Oct 5, 1994, Oct 27, 1993, and May 1, 1993.

---------------------------------------------------------
Title: 3D Magnetic Reconnection: Example of an X-Ray Bright Point
Authors: Demoulin, P.; Mandrini, C. H.; van Driel-Gesztelyi, L.;
Priest, E. R.; Henoux, J. C.; Schmieder, B.
1996ASPC..111...49D Altcode: 1997ASPC..111...49D
In the classical view magnetic reconnection occurs at neutral points
and implies transport of magnetic field-lines across separatrices. The
authors show that reconnection may also occur in the absence of neutral
points at so-called "quasi-separatrix layers" (QSLs), where there is a
steep gradient in field-line linkage at the boundaries. Reconnection
occurs in QSLs where the field-line velocity becomes larger than the
allowed maximal plasma velocity or where the electric-current density
becomes too great. The authors describe both a theoretical and an
observed configuration. In the case of a simple sheared X-field they
show that even a smooth continuous shear flow, imposed at the boundary,
gives strong plasma jetting inside and parallel to the QSLs. Applying
the QSL method to an X-ray bright point observed by Yohkoh, they find
field lines in the extrapolated field which are on both sides of QSLs
and which are in good agreement with loops observed in Hα and X-rays
related to emerging flux. The evolution of the QSL width may explain
the brightness evolution of the XBP.

---------------------------------------------------------
Title: Emerging Flux, Reconnection, and XBP
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Demoulin, P.;
Mandrini, C.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein,
N.; Mein, P.
1996mpsa.conf..459V Altcode: 1996IAUCo.153..459V
No abstract at ADS

---------------------------------------------------------
Title: Emerging flux seen by Yohkoh.
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Mandrini, C.;
Démoulin, P.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.;
Mein, N.; Mein, P.
1996joso.proc..124V Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Ultraviolet Observations of the Structure and Dynamics of an
Active Region at the Limb
Authors: Korendyke, C. M.; Dere, K. P.; Socker, D. G.; Brueckner,
G. E.; Schmieder, B.
1995ApJ...443..869K Altcode:
The structure and dynamics of active region NOAA 7260 at the limb have
been studied using ultraviolet spectra and spectroheliograms obtained
during the eighth rocket flight of the Naval Research Laboratory's
High Resolution Telescope an Spectrograph (HRTS). The instrument
configuration included a narrow-bandpass spectroheliograph to observe
the Sun in the lines of C IV lambda 550 and a tandem-Wadsworth mount
spectrograph to record the profiles of chromospheric transition
region and coronal lines in the 1850-2670 A region. The combination
of high spatial resolution and high spectral purity C IV slit jaw
images with ultraviolet emission-line spectra corresponding allows
examination of a variety of active region phenomena. A time series
of spectroheliograms shows large-scale loop systems composed of
fine-scale threads with some extending up to 100 Mm above the
limb. The proper motion of several supersonic features, including
a surge were measured. The accelerated plasmas appear in several
different geometries and environments. Spectrograph exposures were
taken with the slit positioned at a range of altitudes above the limb
and provide a direct comparison between coronal, transition region
and chromospheric emission line profiles. The spectral profiles of
chromospheric and transition region emission lines show line-of-sight
velocities up to 70 km/s. These lower temperature, emission-line spectra
show small-scale spatial and velocity variations which are correlated
with the threadlike structures seen in C IV. Coronal lines of Fe XII
show much lower velocities and no fine structure.

---------------------------------------------------------
Title: Hα surges and associated Soft X-ray loops
Authors: Schmieder, B.; Shibata, K.; van Driel-Gesztelyi, L.;
Freeland, S.
1995SoPh..156..245S Altcode:
A recurrent Hα surge was observed on 7 October, 1991 on the western
solar limb with the Meudon MSDP spectrograph. The GOES satellite
recorded X-ray subflares coincident with all three events. During
two of the surges high-resolutionYohkoh Soft X-ray Telescope (SXT)
images have been taken. Low X-ray loops overlying the active region
where the surges occurred were continuously restructuring. A flare
loop appeared at the onset of each surge event and somewhat separated
from the footpoint of the surge. The loops are interpreted as causally
related to the surges. It is suggested that surges are due to magnetic
reconnection between a twisted cool loop and open field lines. Cold
plasma bubbles or jets squeezed among untwisting magnetic field
lines could correspond to the surge material. No detection was made
of either X-ray emission along the path of the surges or X-ray jets,
possibly because of the finite detection threshold of theYohkoh SXT.

---------------------------------------------------------
Title: Relation between Cool and Hot Post-Flare Loops of 26 June
1992 Derived from Optical and X-Ray (SXT-YOHKOH) Observations
Authors: Schmieder, B.; Heinzel, P.; Wiik, J. E.; Lemen, J.; Anwar,
B.; Kotrc, P.; Hiei, E.
1995SoPh..156..337S Altcode:
We have analyzed the physical conditions of the plasma in post-flare
loops with special emphasis on dynamics and energy transport using
SXT-data (hot plasma) and optical ground-based data from Pic du Midi,
Wrocław, and Ondřejov (cool plasma). By combining the Hα observations
with the SXT images we can understand the relationship between cool and
hot plasmas, the process of cooling post-flare loops and the mechanism
which maintains the long duration of these loops. Using recent results
of NLTE modeling of prominence-like plasmas, we derive the emission
measure of cool Hα loops and this gives us a realistic estimate of
the electron density (2.2 × 1010 cm−3). Then,
by comparing this emission measure with that of hot loops derived from
SXT data, we are able to estimate the ratio between electron densities
in hot and cool loops taking into account the effect of geometrical
filling factors. This leads to the electron density in hot loops 7 ×
109 cm−3. We also derive the temperature of
hot X-ray loops (≃ 5.5 × 106 K), which, together with
the electron density, provides the initial values for solving the
time-dependent energy balance equation. We obtain the cooling times
which are compared to a typical growth-time of the whole loop system
(∼ 2000 s). In the legs of cool Hα loops, we observe an excess
of the emission measure which we attribute to the effect of Doppler
brightening (due to large downflow velocities).

---------------------------------------------------------
Title: Preparing for SOHO: results from the transition region camera
Authors: Wiik, J. E.; Foing, B. H.; Schmieder, B.; Martens, P.;
Fleck, B.
1994ESASP.373..433W Altcode: 1994soho....3..433W
No abstract at ADS

---------------------------------------------------------
Title: THEMIS: its capabilities and key programs
Authors: Schmieder, B.; Mein, P.
1994ESASP.373..393S Altcode: 1994soho....3..393S
No abstract at ADS

---------------------------------------------------------
Title: Dynamics of post-flare loops observed on June 26, 1992
Authors: Wiik, J. E.; Schmieder, B.; Heinzel, P.; Roudier, T.
1994ESASP.373..207W Altcode: 1994soho....3..207W
No abstract at ADS

---------------------------------------------------------
Title: Dynamical fine structures of the chromosphere
Authors: Tsiropoula, G.; Schmieder, B.; Alissandrakis, C. E.
1994SSRv...70...65T Altcode:
We have studied the spatial structure and temporal evolution of a
chromospheric region with chains of mottles at the junction of three
supergranules. The observations were obtained with the Multichannel
Subtractive Double Pass spectrograph operating in Hα at the Pic du
Midi Observatory. From a statistical point of view the fine structures
were stable in intensity over the observation period (15 min), while the
line of sight velocity showed remarkable changes within a few minutes. A
detailed analysis shows that the predominant pattern of bulk motion in
the dark mottles is that of downflow at their footpoints and upflow at
their tops, which is followed by downflows along the whole structure and
that this process repeats itself several times during their lifetime.

---------------------------------------------------------
Title: Hierarchy of spatial scale sin UV prominences
Authors: Schmieder, B.; Wiik, J. E.; Dere, K. P.
1994SSRv...70..175S Altcode:
Ultraviolet spectra of a quiescent prominence observed with theHigh
Resolution Telescope and Spectrograph (HRTS) are analyzed. Different
techniques lead to greatly different spatial scales for the prominence
structures. The UV spectra show strong variations in intensity and
Doppler shift on scales larger than 1700 km. Spectroscopic diagnostics
employing line intensity ratios indicate the existence of scales
between 400 m to some hundred kilometers. We attempt to interpret
various aspects of the prominence intensities and velocities with a
multiple thread model.

---------------------------------------------------------
Title: Coordinated optical and YOHKOH observations of 26 June 1992
flare loops
Authors: Heinzel, P.; Kotrč, P.; Schmieder, B.; Hiei, E.; Anwar, B.
1994SSRv...70..181H Altcode:
Optical spectra of large flare loops were detected by the Ondřejov
Multichannel Flare Spectrograph (MFS) during coordinated observations
with MSDP at Pic du Midi (Hα) and the soft X-ray telescope (SXT)
on Yohkoh. The CCD video images taken by the MFS slit-jaw camera
document the time-development of the flare loops as seen through the
Hα filter. Preliminary analysis of the MSDP images shows the intensity
structure of the cool flare loops and their velocity fields. From the
spectra we can clearly see the intensity variations along the cool
loops. SXT images show the structure of hot X-ray loops similar to
that of cool loops. Special attention is devoted to the bright tops,
simultaneously observed in X-rays, Hα and other optical lines. Based
on a preliminary analysis of the optical spectra, we speculate about
possible mechanisms leading to an observed bright emission at the tops
of cool loops. We suggest that direct soft X-ray irradiation of cool
loops at their tops could be, at least partly, responsible for such
a strong brightening.

---------------------------------------------------------
Title: Time evolution of fine structures in the solar chromosphere.
Authors: Tsiropoula, G.; Alissandrakis, C. E.; Schmieder, B.
1994A&A...290..285T Altcode:
We have studied the temporal evolution of two quiet chromospheric
regions, one with a typical rosette and another with chains of
mottles at the junction of three supergranules. The observations
were obtained during 15 minutes with the Multichannel Subtractive
Double Pass spectrograph (MSDP) operating in Hα at the Pic du Midi
Observatory. We derived intensity maps and Doppler shift velocities at
different wavelengths along the Hα profile over a two dimensional
field of view. The observed contrast profiles were matched with
theoretical contrast profiles using Beckers' cloud model for a more
accurate determination of the line of sight velocity. A statistical
analysis with cross correlation functions showed that the fine
structures were stable in intensity over the observation period (15
min), but the line of sight velocity showed important changes within
a few minutes. A detailed analysis of the velocities along the axes
of dark mottles showed that the predominant pattern of bulk motion is
that of downflow at their footpoints and alternating phases of upflow
and downflow at their tops. This motion is consistent with Pikel'ner's
model for spicules, which attributes this pattern to the reconnection of
opposite magnetic filed lines. This picture is also consistent with the
velocity reversals with time observed in spicules and may be associated
to the systematic downflows observed in the transition region. Doppler
shift velocities in dark mottles are too low compared to those derived
with the cloud model; the latter are comparable to those reported for
spicules, strengthening the view that these structures are identical.

---------------------------------------------------------
Title: Energy Transport and Dynamics
Authors: Schmieder, B.; Peres, G.; Enome, S.; Falciani, R.; Heinzel,
P.; Hénoux, J. C.; Mariska, J.; Reale, F.; Rilee, M. L.; Rompolt, B.;
Shibasaki, K.; Stepanov, A. V.; Wülser, J. P.; Zarro, D.; Zharkova, V.
1994SoPh..153...55S Altcode:
We report findings concerning energy transport and dynamics in flares
during the impulsive and gradual phases based on new ground-based and
space observations (notably fromYohkoh). A preheating sometimes occurs
during the impulsive phase. CaXIX line shifts are confirmed to be
good tracers of bulk plasma motions, although strong blue shifts are
not as frequent as previously claimed. They often appear correlated
with hard X-rays but, forsome events, the concept that electron beams
provide the whole energy input to the thermal component seems not
to apply. Theory now yields: new diagnostics of low-energy proton
and electron beams; accurate hydrodynamical modeling of pulse beam
heating of the atmosphere; possible diagnostics of microflares (based
on X-ray line ratio or on loop variability); and simulated images of
chromospheric evaporation fronts. For the gradual phase, the continual
reorganization of magnetic field lines over active regions determines
where and when magnetic reconnection, the mechanism favoured for energy
release, will occur. Spatial and temporal fragmentation of the energy
release, observed at different wavelengths, is considered to be a
factor as well in energy transport and plasma dynamics.

---------------------------------------------------------
Title: Coronal Structures Observed in X-rays (NIXT) and H_alpha Surges
Authors: Schmieder, B.; Mouradian, Z.; Golub, L.; Antiochos, S.
1994kofu.symp..317S Altcode:
Ground-based coordinated observations with the Multichannel subtractive
double pass spectrograph (MSDP) and the heliograph in Meudon allowed
us to portray the chromospheric intensity and velocity fields below
coronal structures observed with the Normal Incidence X-ray Telescope
(NIXT). On July 11, 1991 (eclipse day) we have identified in AR 6713
(N38 W 42) the X-ray signatures of the network, subflares, filaments
and surges. The largest H_alpha surge has only weak emission in
X-ray, while a weak H_alpha feature corresponds to a very bright x-ray
subflare. We calculate the emission measures of these events and give
some constraints on the triggering mechanisms of surges.

---------------------------------------------------------
Title: Microflares and their Related Events
Authors: Schmieder, B.; Fontenla, J.; Tandberg-Hanssen, E.; Simnett,
G. M.
1994kofu.symp..339S Altcode:
We have studied in detail two series of events that occur in two
separate active regions on October 9 and June 15, 1980 during the
period of SMM observations. These events can be considered as typical
of a class of solar compact subflares. The events have been studied
using simultaneous UVSP (C IV) and Meudon (H_alpha) data, and for the
brighter event we also use X-ray data from HXIS. Characteristics of
microflares are derived. The simplest microflare may be composed of
a large number of small events, some of which appear to be triggered
by earlier events in the same series.

---------------------------------------------------------
Title: Evolution of Active Regions Leading to Flares
Authors: Schmieder, B.; Demoulin, P.; Henoux, J. -C.; Driel-Gesztelyi,
L. V.; Mandrini, C.; Rovira, M.
1994kofu.symp..297S Altcode:
We model observed longitudinal magnetic fields obtained in Potsdam,
Meudon, MSFC Hunstville by a series of magnetic sources located
below the photosphere. H_alpha flare kernels are found situated on
intersecting separatrices (surfaces delimiting regions of different
magnetic connectivities). We deduce that energy release occurs
mainly at the separator by magnetic reconnection. Evidence for both
neutralized and un-neutralized currents are observed in different
flaring regions. Moreover we have found two photospheric currents of
opposite sign, linked in the corona by field lines, at the border of
flare kernels.

---------------------------------------------------------
Title: Observational support of reconnection in solar flares
Authors: Démoulin, P.; Hénoux, J. C.; Schmieder, B.; Mandrini,
C. H.; Rovira, M. G.; Somov, B.
1994SSRv...68..129D Altcode:
We present a detailed analysis of the magnetic topology of flaring
active region. TheH α kernels are found to be located at the
intersection of the separatrices with the chromosphere when the shear,
deduced from the fibrils or/and transverse magnetic field direction,
is taken into account. We show that the kernels are magnetically
connected by field lines passing close to the separator. We confirm,
for other flares, previous studies which show that photospheric current
concentrations are located at the borders of flare ribbons. Moreover
we found two photospheric current concentrations of opposite sign,
linked in the corona by field lines which follow separatrices. These
give evidence that magnetic energy is released by reconnection processes
in solar flares.

---------------------------------------------------------
Title: Erratum: A study of surges and flares within an active region
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Gerlei, O.; Simnett,
G. M.
1994SoPh..151..399S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Comparison between Cool and Hot Plasma Behaviors of Surges
Authors: Schmieder, B.; Golub, L.; Antiochos, S. K.
1994ApJ...425..326S Altcode:
Ground-based coordinated observations with the Multichannel Subtractive
Double Pass spectrograph (MSDP) allowed us to obtain chromospheric
intensity and velocity field maps below coronal structures during the
launch of the NIXT payload on 1991 July 11 (eclipse day). A large
H-alpha ejection in AR 6713 (N38 W40) was detected during the NIXT
flight. However, only a low level of X-ray emission was associated
with this event. In contrast, bright X-ray emission associated with a
subflare was observed in a nearby active region, but with only a weak
associated ejection in H-alpha. A discussion of both of these events
gives strong constraints on the triggering mechanisms of surges.

---------------------------------------------------------
Title: Time Evolution of a Miniflare as Seen in H alpha , UV Lines,
and X-Rays
Authors: Fontenla, J.; Schmieder, B.; Simnett, G. M.; Tandberg-Hanssen,
E.
1994ApJ...424.1022F Altcode:
A miniflare that occurred in active region Hale 16896 on 1980 June 15
was observed in H-alpha, UV lines, and soft X-rays. These data allow us
to analyze the flare emission and derive the energetics and dynamics
of the chromospheric plasma involved. Our results indicate that the
energy released by the miniflare was about 1028 ergs, about
four orders of magnitude smaller than that of a large flare. However,
hard X-rays (5.5-8.0 keV) were observed which indicated a plasma with
temperature as high as 27 x 106 K. The H-alpha wings, C
IV, and X-rays all showed a short-lived and compact (3 sec x 3 sec)
brightening in a location near the leading sunspot. At this location,
small-scale changes in the magnetic field were observed from about 2 hr
before to about 6 hr after the miniflare. Only very small velocities
seem to have been associated with most of the event in H-alpha. The
data are consistent with short and dense loops at temperatures above
107 K which lost a large fraction of their energy via
downward conduction through regions at the footpoints. Several secondary
events appear to have been triggered by the miniflare along an arch
filament which itself was not greatly affected. A number of much less
energetic (1025-1026 erg) events preceded and
followed the mini-flare. One of these occurred 11 minutes after the
mini-flare and displayed a highly Doppler-shifted signature from the
foot-point of a C IV arch. This arch delineates the connection that
existed between the location of the mini-flare and the location of
secondary events triggered by the flare.

---------------------------------------------------------
Title: Relationship between magnetic field evolution and flaring
sites in AR 6659 in June 1991
Authors: Schmieder, B.; Hagyard, M. J.; Guoxiang, Ai; Hongqi, Zhang;
Kalman, B.; Gyori, L.; Rompolt, B.; Demoulin, P.; Machado, M. E.
1994SoPh..150..199S Altcode:
During the international campaign of June 1991, the active region AR
6659 produced six very large, long-duration flares (X10/12) during its
passage across the solar disk. We present the characteristics of four
of them (June 4, 6, 9, 15). Precise measurements of the spot motions
from Debrecen and Tokyo white-light pictures are used to understand the
fragmentation of the main sunspot group with time. This fragmentation
leads to a continuous restructuring of the magnetic field pattern
while rapid changes are evidenced due to fast new flux emergence
(magnetograms of MFSC, Huairou). The first process leads to a shearing
of the field lines along which there is energy storage; the second one
is the trigger which causes the release of energy by creating a complex
topology. We conjecture that these two processes with different time
scales are relevant to the production of flares.

---------------------------------------------------------
Title: Relationship between electric currents, photospheric motions,
chromospheric activity, and magnetic field topology
Authors: van Driel-Gesztelyi, L.; Hofmann, A.; Demoulin, P.; Schmieder,
B.; Csepura, G.
1994SoPh..149..309V Altcode:
Through coordinated observations made during the Max'91 campaign in June
1989 in Potsdam (magnetograms), Debrecen (white light and Hα), and
Meudon (MSDP), we follow the evolution of the sunspot group in active
region NOAA 5555 for 6 days. The topology of the coronal magnetic field
is investigated by using a method based on the concept of separatrices -
applied previously (Mandriniet al., 1991) to a magnetic region slightly
distorted by field-aligned currents. The present active region differs
by having significant magnetic shear. We find that the Hα flare
kernels and the main photospheric electric current cells are located
close to the intersection of the separatrices with the chromosphere,
in a linear force-free field configuration adapted to the observed
shear. Sunspot motions, strong currents, isolated polarities, or
intersecting separatrices are not in themselves sufficient to produce a
flare. A combination of them all is required. This supports the idea
that flares are due to magnetic reconnection, when flux tubes with
field-aligned currents move towards the separatrix locations.

---------------------------------------------------------
Title: Chromospheric fine structure: Black &amp; white mottles
Authors: Heinzel, P.; Schmieder, B.
1994A&A...282..939H Altcode:
H-alpha observations of the chromosphere have been obtained
on June 17, 1986 with a high spatial resolution using the MSDP
(Multichannel Subtractive Double Pass) spectrograph operating
at Pic du Midi observatory. Various fine structures are observed
in the chromosphere: bushes of fibrils around supergranules and
fibrils (mottles) in the rosettes. They are relatively stable, but
line-of-sight velocities +/- 5-10 km/s are observed at the boundaries
of supergranules (rosettes). Velocity images exhibit finer structures
than intensity ones, with no cospatial relationship between both of
them. Typical H-alpha line profiles of dark and bright (black &amp;
white) mottles, constructed from 11 MSDP channels, are used to derive
the physical conditions in these structures. Non-local thermodynamic
equilibrium (NLTE) models of dark and bright mottles are represented
by a grid of prominence-like models of Goutebroze et al. (1993). It is
demonstrated that higher-pressure models(pg approximately =
0.5-1 dyn/sq cm) with temperature around 104 K naturally
explain the profiles of both dark and bright structures. By introducing
a generalized two-cloud model with non-uniform source function, we
account schematically for a shear-type velocity field. However, the
velocities are found to be of a secondary importance when the broad
U-shaped profiles formation is considered. We conclude that dark
and bright mottles have a similar nature and that their brightness
difference is predominantly due to pressure variations of the plasma
injected into the rosette flux tubes. Finally, we discuss the ambiguity
of H-alpha contrast profiles and comment on applicability of the
classical cloud model.

---------------------------------------------------------
Title: Interpretation of Magnetic Field Structures of AR 6659 in
June 7-10; 1991
Authors: Wu, S. T.; Weng, F. S.; Hagyard, M. J.; Machado, M.;
Schmieder, B.
1994scs..conf..201W Altcode: 1994IAUCo.144..201W
The authors examine the magnetic structures in AR 6659 by using the
observation of vector magnetic fields obtained at MSFC/NASA. The
structure of coronal loops is revealed. The authors also computed the
total magnetic energy vs time of this region. It shows that there is
indeed enough energy to propel the numerous, energetic flares that
were observed in this region.

---------------------------------------------------------
Title: Fine structures of the solar chromosphere
Authors: Schmieder, B.; Heinzel, P.; Tsiropoula, G.; Alessandrakis,
C. E.
1994ASIC..433..151S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Coronal Cavities Observed Around Prominences
Authors: Wiik, J. E.; Schmieder, B.; Noëns, J. -C.
1994emsp.conf..167W Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Time Evolution of Chromospheric Fine Structures
Authors: Tsiropoula, G.; Alissandrakis, C. E.; Schmieder, B.
1994emsp.conf..111T Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Electron Densities in Solar Prominences
Authors: Wiik, J. E.; Heinzel, P.; Schmieder, B.
1994scs..conf..381W Altcode: 1994IAUCo.144..381W
The authors concentrate on the determination of electron densities,
using the MSDP spectrograph at Pic du Midi. They discuss a new approach
for diagnosing the electron densities by comparing the observed Hα
intensities with theoretically predicted variations of the line-center
intensity versus Ne.

---------------------------------------------------------
Title: Coronal Structures Observed in X-Rays (NIXT) and Hα Surges
Authors: Schmieder, B.; Mouradian, Z.; Golub, L.; Antiochos, S.
1994emsp.conf..159S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Black and White Mottles
Authors: Heinzel, P.; Schmieder, B.
1994emsp.conf...81H Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Coronal Environment of Quiescent Prominences
Authors: Wiik, J. E.; Schmieder, B.; Noens, J. C.
1994SoPh..149...51W Altcode:
With thespectro-coronagraph and themultichannel subtractive double
pass spectrograph (MSDP) at the Pic du Midi Observatory two quiescent
prominences were observed simultaneously. From the spectro-coronagraph
observations 2D maps of HeI λ 10830 å, FeXIII λ 10798 and 10747 å
line intensities were obtained. In addition, we obtained 2D maps of
the ratioR of the two iron lines. This ratio is used as a diagnostic
for determining the density of the hot coronal plasma surrounding
prominences. We found that the electron density is higher at the
location of the prominences than in the corona, whereas small regions
(∼40″) of lower electron density are unevenly distributed around
the prominences indicating that the surrounding corona is highly
inhomogeneous. The density of the cavity is reduced by a factor
1.5 compared to the density of the prominence environment (∼5 ×
108 cm−3). We discuss the existence of cavities
around these prominences according to the orientation of their axes
relative to the line of sight and according to the velocity field
inside the prominences. Constraints on models for prominence formation
are derived.

---------------------------------------------------------
Title: Poster Papers presented at the Seventh European Meeting on
Solar Physics
Authors: Belvedere, G.; Rodonó, M.; Schmieder, B.; Simnett, G. M.
1994emsp.conf.....B Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Twisted Flux Tubes and Sunspot Motions in AR 5555
Authors: van Driel-Gesztelyi, L.; Démoulin, P.; Schmieder, B.;
Hofmann, A.; Csepura, G.
1994emsp.conf..115V Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Sites of flares and filaments in solar active regions
Authors: Schmieder, B.; van-Driel, L.; Hofmann, A.; Démoulin, P.;
Hénoux, J. C.; Hagyard, M.
1993AdSpR..13i.119S Altcode: 1993AdSpR..13..119S
We applied a method developed to derive from magnetic field data the
location of energy release in solar active regions. This method has
been applied to two sets of data (June 13-15 1980 and June 23-25 1989)
using magnetograms (Meudon, MSFC, Potsdam) and Hα data (Debrecen,
MSDP Meudon). The Hα flares are located at intersections of the
separatrices with the chromosphere in places where high density currents
are observed. This supports the idea that the energy released in flares
is due to magnetic reconnection at the location of a separator and
subsequently transported to the chromosphere along field lines. It is
found that strong magnetic shear is a necessary condition for filament
formation. Magnetic shear merely determines the importance of the
flare and is certainly not a necessary condition for flare activity.

---------------------------------------------------------
Title: Relationship between magnetic field evolution and flaring
sites in AR 6659 on June 1991
Authors: Schmieder, B.; Démoulin, P.; Hagyard, M.; Machado, M. E.;
Guo, Xiang Ai; Zhang, Hongqi; Fu, Qijun; Zhi, Kai Li; Luan, Ti;
Kalman, B.; Györi, L.
1993AdSpR..13i.123S Altcode: 1993AdSpR..13..123S
During the international campaign of June 1991, the active region AR
6659 produced 6 very large long duration flares at the same location
during its passage across the solar disk. Vector magnetograms were
obtained at Marshall (Huntsville) and Huairou Station (Beijing) with
a time difference of 10 to 12 hours, thus giving a good survey of
the magnetic field evolution with time. The flare of June 6/01:08 UT
(X12 plus/4B) was observed in Shahe Station (Beijing) in white light,
in Hα and in radio centimetric wavelengths. The evolution of the flare
of June 9/01:43 UT (X10/3B) has been followed in Hα at the Yunnan
Observatory (Kunming). An other one was well observed on June 15 at
08:20 UT in Wroclaw and in Debrecen. Some subflares were observed at
Sac Peak on June 4, 5, 7 at Meudon on June 10, 14 and Debrecen on
June 12 and 13. In this short communication we concentrate on
the relationship between magnetic field shear and flare sites.

---------------------------------------------------------
Title: Correlation of He II lyman alpha with He I 10830 Å, and with
chromospheric and EUV coronal emission
Authors: Thompson, W. T.; Neupert, W. M.; Jordan, S. D.; Jones, H.;
Thomas, R. J.; Schmieder, B.
1993SoPh..147...29T Altcode:
This paper describes the results of comparing SERTS-3 images obtained
in the transition region line of HeII 304 å with chromospheric HeI
10830 å absorption, with strong coronal lines of MgIX 368 å, FeXV
284 å and 417 å, and FeXVI 335 å and 31 å, with Hα, with CaII
8542 å, and with magnetograms in FeI 8688Hα. All of the images are
illustrated, and the image reconstruction techniques used are described
and evaluated. The high correlation of the HeII 304 å and HeI 10830
å images, originally found by Harvey and Sheeley (1977), is confirmed
and is put on a quantitative basis. We find that the supergranulation
network has greater contrast, and that filaments appear darker, in
10830 å than in 304 å. In active regions, the 304 å line follows more
closely the behavior of Hα and CaII 8542 å than the 10830 å line.

---------------------------------------------------------
Title: A Study of Surges and Flares Within an Active Region
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Gerlei, O.; Simnett,
G. M.
1993SoPh..146..163S Altcode:
Active region 2684 was observed by the Solar Maximum Mission and
ground-based observatories simultaneously for over 12 hours on September
23, 1980. During these observations, recurrent surges were detected
above an area with complex parasitic magnetic polarity located at the
periphery of the active region. The time evolution of the Hα surges,
CIV brightenings and X-ray spikes leads to the conclusion that the
energy source is in the corona, from magnetic reconnection. The energy
is transported by energetic charged particles along the loops, thereby
heating the chromosphere as the particles lose their energy. The
divergent motion of the spots corresponding to small dipoles at
the base of the surge indicates that there is important magnetic
reorganisation. According to the magnetic field-line configuration
(large loop or open structures), X-rays can (or cannot) be associated
with surges.

---------------------------------------------------------
Title: UV prominences observed with the HRTS: structure and physical
properties
Authors: Wiik, J. E.; Dere, K.; Schmieder, B.
1993A&A...273..267W Altcode:
Ultraviolet spectra of two quiescent prominences (PL1, PL2) observed
with the High Resolution Telescope and Spectrograph (HRTS) are described
and analyzed. Meudon synoptic maps and spectroheliograms indicate that
prominence PL 1 was extremely active during the flight and that material
ejections were likely. PL2 appeared to be a more stable prominence. The
significant differences between the spectra of the two prominences
can perhaps be explained by their levels of activity. The spectrum of
the more active prominence PL1 is dominated by transition zone lines
formed near 105 K whereas the second prominence PL2 shows
considerable emission of cooler chromospheric lines formed near 2
× 1O4 K. PL 1 also exhibits larger bulk flow velocities
(up to ∼ 30 km s-1) and non-thermal velocities (∼20km
s-1). From line ratios (O IV, N V, N IV, Si IV) a relatively
large electron density (∼1011 cm-3) is derived
for the PL1 prominence transition region (PTR). In comparison, PL2 is
a relatively quiet prominence with bulk flow velocities generally less
than ∼3 km s-1. Different techniques yield greatly
different spatial scales for the prominence. The UV spectra show strong
variations in intensity and Doppler shift on scales of about 1700km. The
combined density and emission measures indicate path lengths of 400 m
or less. The optical depth in C IV requires path lengths of 40 km or
less. If, as suggested by these analyses, it is assumed that prominence
emission is due to a number of micro-structures with a Gaussian velocity
distribution, then spatial scales of the micro-structures of a few
hundred kilometers are found.

---------------------------------------------------------
Title: Common Evolution of Adjacent Sunspot Groups
Authors: van Driel-Gesztelyi, L.; Csepura, G.; Nagy, I.; Gerlei, O.;
Schmieder, B.; Rayrole, J.; Demoulin, P.
1993SoPh..145...77V Altcode:
The evolution of two adjacent bipolar sunspot groups is studied using
Debrecen full-disc, white-light photoheliograms and Hα filtergrams
as well as Meudon magnetograms. The proper motions of the principal
preceding spots of both groups show quite similar patterns; the
spots move along almost parallel tracks and change the direction
of their motion on the same day at almost the same heliographic
longitude. Also, three simultaneous emergences of magnetic flux were
observed in both groups. These observations support the idea that
these adjacent sunspot groups were magnetically linked below the
photosphere. Matching the extrapolated magnetic field lines with the
chromospheric fibril structure appears to be different in the two groups
since they indicate quite different model solutions for each group,
i.e., a near-potential magnetic field configuration in the older group
(1) and a twisted force-free field configuration in the younger group
(2). The latter configuration could be created by a considerable twist
of the main bunch of flux tubes in Group 2, which is reflected in the
relative sunspot motions. It is also showed how this twist contributed
to the formation of a filament between the two groups.

---------------------------------------------------------
Title: Evidence for magnetic reconnection in solar flares
Authors: Demoulin, P.; van Driel-Gesztelyi, L.; Schmieder, B.; Hemoux,
J. C.; Csepura, G.; Hagyard, M. J.
1993A&A...271..292D Altcode:
From a study of the magnetic field topology in an active region,
evidence is derived that solar flares are produced by magnetic
reconnection. We study a complex group with two active regions (AR
25 t 1 and AR 2512) for three consecutive days, June 13-15 1980. The
observed longitudinal magnetic field is used to model the coronal
magnetic field by the potential field created by a series of magnetic
charges. This computed field matches satisfactorily the Ho fibrils
and the observed transverse field direction. A set of flares occurs
principally in the northern group (AR 2511). During these three days,
two different magnetic configurations in succession are responsible
for the occurrence of these flares: first the intrusion of a new
opposite flux in the following polarity, secondly the emergence of new
flux between the main polarities. In this last case flares occurred,
although the emerging bipole is almost parallel to the main bipole. We
show that even in this bipolar configuration a separator is present
and that observed H flare ribbons are located near the intersection of
the computed separatrices with the photosphere. This provides strong
support to a model where reconnection releases the stored magnetic
energy. The induced evolution of the magnetic field forces reconnection
along others separators. They are connected by magnetic field lines
to fainter kernels.

---------------------------------------------------------
Title: The fine structure of a chromospheric rosette
Authors: Tsiropoula, G.; Alissandrakis, C. E.; Schmieder, B.
1993A&A...271..574T Altcode:
We have studied the spatial behaviour of the physical properties
of dark mottles forming a well-defined rosette. The observations
were obtained with the Multichannel Subtractive Double Pass (MSDP)
spectrograph, operating in Hα at the Pic du Midi Observatory. From
these observations, intensity fluctuations and Doppler shift velocities
at different wavelengths were derived over a two dimensional field of
view. The observed contrast profiles were matched with theoretical
contrast profiles using Beckers' cloud model and 4 parameters were
derived for the dark mottles: the source function, the line-of-sight
velocity, the Doppler width and the optical depth. From these parameters
a range for the temperature and electron density can be derived using
Vernazza's et al. (1981) model D. We detected strong downflows at
the roots of the mottles, while their upper part is ascending with
velocities sometimes greater than 10 km s-1. The values of
the cloud parameters are consistent with values given by other authors
for this kind of features. Consistency was also found between cloud
parameters and the values given for spicules, leading to the conclusion
for the identity of these structures.

---------------------------------------------------------
Title: Active Region Evolution Through Coordinated Observations
Authors: Mein, N.; Mein, P.; Schmieder, B.; Engvold, O.; Molowny,
R.; Ai, G. X.
1993ASPC...46...63M Altcode: 1993mvfs.conf...63M; 1993IAUCo.141...63M
No abstract at ADS

---------------------------------------------------------
Title: Underneath coronal loops: MSDP observations coordinated with
SERTS 4 and NIXT flights.
Authors: Schmieder, B.; Mein, N.; Golub, L.; Davila, J. M.; Thomas,
R.; Brosius, J.
1992ESASP.348..257S Altcode: 1992cscl.work..257S
Ground-based coordinated observations with the multichannel subtractive
double pass spectrograph (MSDP) allowed to portray the chromospheric
intensity and velocity fields below coronal structures during recent
launchs of sounding rockets. During SERTS 4 observations (May 7,
1991), two different active regions presenting flare and filament have
been coaligned with UV structures. In July 11, 1991 (eclipse day)
large Hα ejection material in AR 6713 was detected during the NIXT
flight. Preliminary results are displayed.

---------------------------------------------------------
Title: Intensity, velocity and turbulence in prominences observed
with the HRTS instrument.
Authors: Schmieder, B.; Wiik, J. E.; Dere, K. P.
1992JAF....43...36S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Structural Elements of Filaments
Authors: Schmieder, B.
1992SoPh..141..275S Altcode:
Filaments are cool structures (∼ 7000 K) embedded in the hot
corona. Observations in the optical wavelength range (Hα, Hβ, Ca II
K) show that filaments consist principally of a main body with the
footpoints tied in the photosphere, generally at the boundaries of
the supergranules. New instrumentation (Big Bear, Sacramento Peak,
Canary Islands) reveals that filaments are highly structured. The
dimension of the fine structures is limited by the spatial resolving
power of the instruments (∼ 350 km). These fine structures may be
caused by filamentation along the magnetic field or by a radiative
instability during the formation of the prominences. New attempts based
on radiative transfer calculations, density diagnostics, or dynamics are
being developed in order to estimate the number of threads integrated
along the line of sight, 2 to 200 according to various authors. Plasma
parameter values are derived from these studies. While the models
of prominences take into account the magnetic field observations,
the fine structures and the dynamics are ignored most of the time.

---------------------------------------------------------
Title: Determination of plasma parameters in a quiescent prominence
Authors: Wiik, J. E.; Heinzel, P.; Schmieder, B.
1992A&A...260..419W Altcode:
We present H-alpha observations and analysis of a quiescent, polar crown
prominence observed on June 11, 1988 with the MSDP spectrograph at the
Pic du Midi Observatory. Two-dimensional maps of H-alpha intensities and
line-of-sight velocities have been obtained. The large-scale velocity
pattern consisting of cells and elongated structures is stable on
a time scale of about 1 min, but evolves continuously and undergoes
large changes in shape and amplitude during one hour. This behavior
of the velocity field suggests the presence of twists in flux ropes
or shear motions. Further, comparing the absolute observed intensities
with values from non-LTE radiative computations we estimate the range
of electron densities, source functions and optical thicknesses in
different parts of the prominence. For upper parts of the prominence
we obtain electron densities in the range 1 - 5 x l0 exp 10/cu cm.

---------------------------------------------------------
Title: Time evolution of a two-ribbon flare - Characteristics of
post-flare loops
Authors: Gu, Xiao-Ma; Lin, Jun; Luan, Ti; Schmieder, B.
1992A&A...259..649G Altcode:
Observations of a two ribbon flare on 5 May, 1989 were performed at
Yunnan Observatory and at Meudon. Magnetograms have been obtained in
Huairou-Beijing Observatory. The topology of the flaring region and the
slow evolution of post-flare loops (cool flare loops) can be derived
from Yunnan filtergrams. The ribbons seem to be the footpoints of the
loops. The analysis of H-alpha line profiles in the loops, obtained
with the Multichannel Subtractive Double Pass (MSDP) spectrograph of
Meudon allows us to derive some physical parameters of the loops. The
importance of the reference background intensity is discussed. The cool
flare loops are low (hmax is approximately equal to 25,000
km) dense (ne is approximately equal to 10 exp 11/cu cm) and relatively
inhomogeneous. They are rising with a velocity of 5 to 10 km/s.

---------------------------------------------------------
Title: Intensity, velocity and turbulence in prominences observed
with the HRTS.
Authors: Wiik, J. E.; Dere, K.; Schmieder, B.
1992ESASP.344...65W Altcode: 1992spai.rept...65W
The moments of UV emission line profiles between 1206 and 1670 A
observed in two quiescent prominences with the High Resolution Telescope
and Spectrograph (HRTS) are analysed. Spectral lines in this region
of the solar spectrum provide information on plasmas in the 10000K
to 200000K range. In both prominences a good correlation is found
between the intensities of lines formed at different temperatures. A
good correlation is also found between the non-thermal velocities of
different lines.

---------------------------------------------------------
Title: Structure and Dynamics of Cool Flare Loops
Authors: Heinzel, P.; Schmieder, B.; Mein, P.
1992SoPh..139...81H Altcode:
MSDP observations of the 16 May, 1981 two-ribbon flare are used to
study the physical structure and the dynamical behaviour of cool flare
loops. The loops have been detected in the Hα line just after the
flare maximum and they appeared in absorption against the disk. Using
the first-order differential cloud model (DCM1) technique, we derive
empirically some basic plasma parameters at 15 points along one loop
leg. The flow velocities and the true heights have been reconstructed
with respect to a geometrical projection. Subsequently, detailed
non-LTE models of cool loops have been constructed in order to fit Hα
source function values previously derived from DCM1 analysis. It is
demonstrated that this source function is rather sensitive to the radial
component of the flow velocity (the so-called Doppler brightening)
and to enhanced irradiation of the loops from the underlying flare
ribbons. In this way, we have been able to estimate quantitatively
all plasma parameters which determine the physical structure of cool
loops (i.e., the temperature, pressure, density), as well as the
momentum-balance condition within the loops. For these dark loops we
have arrived at relatively low gas pressures of the order of 0.1-0.5
dyne cm-2 with corresponding electron densities around
1011 cm-3. Pressure-gradient forces have been
found to be of small importance in the momentum-balance equation, and
thus they cannot explain departures from a free-fall motion found in our
MSDP data analysis. We propose three possible solutions to this problem.

---------------------------------------------------------
Title: Chromospheric structure and dynamics.
Authors: Schmieder, B.
1992ESASP.344...35S Altcode: 1992spai.rept...35S
Chromospheric structures are observed up to the limiting spatial
resolving power of the instruments. The magnetic field controls the
chromospheric topology both at the large scale, such as canopies,
supergranulation, mesogranulation and at the small scale, such as
fibrils, mottles, spicules. Different properties of the chromosphere
structure may be deduced from a dynamics study. The author will
discuss on the role of magnetic and convective forces in oscillatory
and non-stationary flows observed in the structures. Spectroscopic
diagnostics are used to derive physical parameters in chromospheric
structures.

---------------------------------------------------------
Title: Post-Flare Loops
Authors: Schmieder, B.
1992LNP...399..124S Altcode: 1992IAUCo.133..124S; 1992esf..coll..124S
Post-flare loops or cool flare loops (CFL) when observed in the
H line are magnetic structures within an active region which are
clearly a fundamental part of the flare itself and not an external
phenomenon or a consequence of flares. After a two-ribbon flare the
field-line reconnection gives rise to flare loops of hot temperature
which shrink and become cool within few minutes to an hour. The Ha
flare loops appear generally as dark loops during the gradual phase
of the flare; viewed on the limb they may appear as loops in emission,
reaching 50000 km. They create a system of quasi-steady arches lasting
up to several hours. Large downflows are observed along the legs of
the loops with deccelaration by comparing to free-fall motions. As
derived from radiative transfer diagnostics, the gas pressure range
of the loops is between 0.2 and 5 dyn cm-2 and the electron density
is between 1010 and 1012 cm-3. The magnetic free energy needs to be
continuously replenished from low levels during the flare. Different
mechanisms may be considered, dynamical ones such as upward motion
from the convection zone pushing the coronal field and twisting of
the field lines, or thermal ones such as evaporation or ablation of
chromospheric material. We will discuss some observational evidence
supporting the Forbes and Malherbe (1986) reconnection model based on
the Kopp and Pneuman configuration.

---------------------------------------------------------
Title: Fine structure analysis of a prominence in H-alpha and
coronal lines
Authors: Wiik, J. E.; Schmieder, B.; Noens, J. C.; Heinzel, P.
1992sws..coll..131W Altcode:
Prominence observations made simultaneously with the MSDP spectrograph
and with the coronagraph at Pic du Midi are presented. The existence
of a coronal cavity is discussed. 2D maps of H-alpha intensities
and the line-of-sight velocities have been obtained. The behavior
of the velocity field suggests the presence of twists along flux
ropes or shear motions. Further, using a probabilistic approach to
the H-alpha-line formation, we estimate the range of temperatures,
electron densities and optical thicknesses in different parts of the
prominence by fitting the observed H-alpha intensity profiles.

---------------------------------------------------------
Title: Plasma Parameters Derived from MSDP Observations of Cool
Flare Loops
Authors: Heinzel, P.; Schmieder, B.; Mein, P.
1992LNP...399..134H Altcode: 1992IAUCo.133..134H; 1992esf..coll..134H
MSDP observations of 16 May 1981 two-ribbon flare are used to study the
physical structure and dynamical behaviour of cool flare loops. The
loops have been detected in the H line just after the flare maximum
and they appeared in absorption against the disk. Using the first-order
differential cloud model (DCM1) technique, we derive empirically some
basic plasma parameters at 15 points along one loop leg. The flow
velocities and true heights have been reconstructed with respect to
a geometrical projection. Subsequently, detailed non-LTE models of
cool loops have been constructed in order to fit H source-function
values previously derived from DCM1 analysis. It is demonstrated that
this source function is rather sensitive to the radial component
of the flow velocity (the so-called Doppler brightening) and to
the enhanced irradiation of the loops from the underlying flare
ribbons. In this way, we have been able to estimate quantitatively
all plasma parameters which determine the physical structure of
cool loops (i. e. the temperature, pressure, density, etc.), as well
as the momentum-balance condition within the loops. For these dark
loops we have arrived at relatively low gas pressures of the order
of 0.1 - 0.5 dyn cm-2 , with corresponding electron densities around
1011 cm-3. Pressure-gradient forces have been found to be of small
importance in the momentum-balance equation. However, the classical
momentum equation is not capable of explaining significant departures
from a free-fall motion under the gravity force, found from our MSDP
data. We propose three possible explanations to this problem.

---------------------------------------------------------
Title: Dynamics in the Prominence - Corona Transition Region from
HRTS Spectra
Authors: Schmieder, B.; Dere, K. P.; Wiik, J. E.
1992LNP...399..333S Altcode: 1992esf..coll..333S; 1992IAUCo.133..333S
Line profiles of UV emission lines between 1206Å and 1670Å observed
in two prominences with the High Resolution Telescope and Spectrograph
(HRTS) are analysed. Spectral lines in this region of the solar spectrum
such as C I, Fe II, Si IV and C IV, provide information on plasmas in
the 10 000 K to 200 000 K range. In the active prominence observed
with HRTS-1 a good correlation is found between the intensities and
velocities of different lines formed over a range of temperatures. On
the contrary, poor cross correlation between the velocities observed
in plasmas of cold temperatures indicates the presence of different
structures in the SL2 prominence. Microturbulent velocities from 0 to
25km s-1 are found in both prominences.

---------------------------------------------------------
Title: Fine structure of solar filaments. II - Dynamics of threads
and footpoints
Authors: Schmieder, B.; Raadu, M. A.; Wiik, J. E.
1991A&A...252..353S Altcode:
The dynamical behavior of the fine structures observed at the Pic du
Midi through a multichannel subtractive double pass (MSDP) spectrograph
during a 15-min period has been studied. Widespread continual changes
in the velocity field were observed during this period, and, for the
whole region, there was virtually no correlation from one minute to the
next. High velocities (up to +/-15 km/s) were detected at locations
where the filament was anchored in the chromosphere using the first
order differential cloud model. It is argued that these footpoints are
essentially the same kind of structures as the chromospheric bushes
seen around supergranules, which show spiculelike activity modified
by the local magnetic field geomentry. Parallel to the filament axis
elongated Doppler structures with coherent motions were observed. These
structures may be interpreted as magnetic flux tubes identifiable
during their short rise time, or they may indicate that there are
coherent wave motions.

---------------------------------------------------------
Title: A microflare-related activation of a filament observed in
H-alpha and C IV lines
Authors: Schmieder, B.; Fontenla, J.; Tandberg-Hanssen, E.
1991A&A...252..343S Altcode:
A filament in active region AR 2717 was observed in two lines formed
at different temperatures (H-alpha at 10 exp 4 K and C IV at 10 exp
5 K) with the multichannel-double-pass (MSDP) spectrograph and the
ultraviolet spectrometer and polarimeter (UVSP). The partial disparition
brusque (DB) of the filament as observed in H-alpha was due to the
heating of a filament section in the vicinity of a bright point. A
propagating disturbance followed this event. A detailed analysis of C
IV rasters shows that this disturbance was not a passive perturbation,
but was itself triggering active phenomena at various locations along
its path, resulting in energy releases. It is suggested that this
propagation of brightness was due to fast successive reconnections
between fine looplike structures of the filament.

---------------------------------------------------------
Title: Conditions for flare and filament formation in interacting
solar active regions
Authors: Schmieder, B.; Henoux, J. -C.; van Driel-Gesztelyi, L.;
Simnett, G. M.
1991A&A...244..533S Altcode:
The evolution of two interacting sunspot groups of different ages is
traced over a period of three days. The photospheric velocity field is
obtained and compared with the general evolution of the region in an
attempt to better understand the conditions that lead to flare activity
and filament formation. It is shown that the observed photospheric
motions can generate dc electric currents, which, in effect, could
lead to energy storage.

---------------------------------------------------------
Title: Comparison of SERTS Spectroheliograms with Ground-Based
Observations
Authors: Thompson, W. T.; Neupert, W. M.; Brosius, J. W.; Jones,
H. P.; Schmieder, B.
1991BAAS...23R1061T Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Oscillations in Hα filaments: center-to-limb study.
Authors: Thompson, W. T.; Schmieder, B.
1991A&A...243..501T Altcode:
Center-to-limb observations of time sequences of the velocity field
in filaments have been made with the MSDP spectrograph operating on
the Meudon solar tower. The velocity power spectra made over whole
filament regions show a broad maximum around 200 s period. The power
in the filaments is reduced compared with the chromosphere power near
the disk center by a factor of 2-4, while at μ = 0.9 they are more
comparable. Nevertheless, the MSDP spectrograph allows a 2D analysis
and the authors find that high oscillation amplitudes (1-1.25 km
s-1) are detected in discrete areas, principally at the
edges of the filaments and in chromospheric fibrils close to the
filament, with well defined periods around 250 s, 200 s, and 150
s. The oscillations are transverse to the direction of the fine
structures. A wave propagation velocity along the fibrils has been
derived from the observations and could correspond to an Alfvén
velocity. The authors discuss mechanisms that may be responsible
for these waves. The oscillations could be interpreted by eigenmodes
of filamentary structures. A resonance phenomenon may occur between
surface waves generated at the boundary of the tubes and body waves
(i.e. Alfvén waves).

---------------------------------------------------------
Title: Flares and filament formation due to the interaction between
two active regions
Authors: Schmieder, B.; van Driel-Gesztelyi, L.; Hénoux, J. C.;
Simnett, G.
1991AdSpR..11e..95S Altcode: 1991AdSpR..11...95S
We follow the evolution (flare activity, filament formation) of two
interacting active regions of different ages over three days, through
observations at white-light, Hα, UV, and X-ray wavelengths. We show
that the observed photospheric motions could generate DC electric
currents and that they could lead to free energy storage. Flares
were observed more-or-less simultaneously in remote locations of the
sunspot group. This suggests that the same perturbation affected an
ensemble of lines of force. Filament formation took place due to DC
current generation by photospheric shearing motions with a velocity
up to 350 m s-1.

---------------------------------------------------------
Title: Coordinated observations with high resolution spectrographs
(HRTS, SERTS, MSDP)
Authors: Schmieder, B.; Thompson, W. T.; Neupert, W. M.; Thomas,
R. J.; Dere, K. P.
1991AdSpR..11e.255S Altcode: 1991AdSpR..11R.255S
Observations with the High Resolution Telescope Spectrograph
(HRTS) aboard Spacelab2 in 1985, and more recently with the Solar
Extreme-ultraviolet Rocket Telescope and Spectrometer (SERTS) during
the rocket flight of May 5, 1989 were well coordinated with the Meudon
instruments, principally with the Multichannel Subtractive Double Pass
(MSDP) spectrograph. These instruments allow the study of phenomena
in a large temperature range and the determination of the energy
budget. MSDP observations coordinated with the SERTS have permitted
the analysis of physical parameters of coronal plasma surrounding
dynamical chromospheric events, such as preflaring region and a
filament. By combining Hα spectrograms and HRTS data, C IV flow
(~50 km s-1) detected at the footpoints of a prominence
has been interpreted by horizontal velocities along the axis of the
arches of the prominence.

---------------------------------------------------------
Title: Oscillations detected in C IV and Hα lines in magnetic
structures
Authors: Schmieder, B.; Thompson, W. T.; Mein, P.
1991AdSpR..11d.195S Altcode: 1991AdSpR..11..195S
Different processes involving the magnetic field and its fine
structures in the atmosphere have been proposed to explain the heating
of the corona. To help explore phenomena related to these different
processes, we will report some new observations of oscillations in fine
chromospheric structures using the MSDP spectrograph operating at Meudon
and the UVSP spectrograph aboard SMM. The temporal analysis of radial
velocities measured in the C IV line shows that no oscillations are
detectable in the transition zone. It is in good agreement with the wave
reflection model generally admitted. In the Hα line the 2 D analysis
points out that the energy observed in an unresolved frequency range
around 250 s in the chromospheric power spectrum is in fact concentrated
in structures parallel to chromospheric fibrils along which the phase
extends coherently. The oscillations appear to be transverse and might
be interpreted either by Alfvén waves generated in the chromosphere
and propagating through magnetic filamentary structures or by eigenmodes
of filamentary structures excited by chromospheric p-modes.

---------------------------------------------------------
Title: Flow patterns in a sunspot region observed in the photosphere,
chromosphere and transition region
Authors: Dere, K. P.; Schmieder, B.; Alissandrakis, C. E.
1990A&A...233..207D Altcode:
The flow patterns around a sunspot at photospheric, chromospheric, and
transition zone temperatures is examined. The spiral fibril pattern
observed in H-alpha is consistent with a constant alpha force-free
field extrapolation of the photospheric magnetic field. Evidence
is found for the first time that C IV fibrils near spots follow the
field lines parallel to the chromospheric H-alpha fibrils. The observed
large-scale pattern of redshifts and blueshifts in the vicinity of the
sunspot is stable and conforms to the typical Evershed flow patterns
of radial outflow at the photospheric levels and radial inflows at
the chromospheric and transition region levels. The three-dimensional
velocity vectors associated with this flow are derived assuming an
axially symmetric Evershed flow.

---------------------------------------------------------
Title: Evaporation in the Transition Region during the Gradual Phase
of Flares
Authors: Schmieder, B.; Malherbe, J. M.; Simnett, G. M.; Forbes,
T. G.; Tandberg-Hanssen, E.
1990ApJ...356..720S Altcode:
Previous observations have revealed that small, but sustained,
H-alpha blueshifts occur in flare ribbons during the gradual, or late,
phase of flares. These blueshifts suggest that there is a gentle
evaporation of chromospheric material throughout the late phase of
flares, but ambiguities in the interpretation of H-alpha leave open
the possibility that these blueshifts are caused by downflowing,
rather than upflowing, material. Using both C IV and soft (3.5-8 keV)
X-ray data from SMM observations, evidence is found which supports the
interpretation of the H-alpha blueshifts as upflows in the range from
4-12 km/s. The blueshifts are interpreted in terms of the reconnection
model proposed by Carmichael (1964). The model produces a sustained
energy release through-out the late phase which accounts for the
prolonged soft X-ray emission after a flare. This energy release comes
from the reconnecting magnetic field above the flare site, and some of
the energy is transported along field lines mapping to the chromosphere
where it drives chromospheric evaporation.

---------------------------------------------------------
Title: Ultraviolet Spectra of a Prominence
Authors: Dere, K.; Lund, P.; Schmieder, B.
1990BAAS...22R.815D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Relationship between a spot and a filament observed during
spacelab 2 mission
Authors: Schmieder, B.; Dere, K. P.; Raadu, M. A.; Démoulin, P.;
Alissandrakis, C. E.
1990AdSpR..10i.195S Altcode: 1990AdSpR..10..195S
During the Spacelab 2 Mission, an active region including a sunspot,
plages, fibrils and a filament which disappears during the observation
period, was observed in Hα and in the C IV lines. The analysis of the
observations leads to several conclusions. Shear in the active region
filament is observed before its disappearance. Hα and C IV upflows
in the filament are well correlated spatially, but the transition
zone (C IV) velocities are an order of magnitude larger than the Hα
chromospheric ones. Over the sunspot, the reverse-Evershed effect is
observed in Hα and in C IV Dopplershift images while strong downflows
are also detected in the C IV profiles. Magnetograph data for
the whole region are used to calculate the linear force-free magnetic
field. A single value of the force-free parameter α is found to give a
good fit to both the sheared filament structure and the sunspot spiral
structures, indicating a causal relationship. We propose a model
based on the inductive coupling between current systems associated with
the filament and the sunspot. Relaxation phenomena due to resistive
effects in the filament could lead to irreversible conversion of
magnetic energy into kinetic energy and heating.

---------------------------------------------------------
Title: Oscillations detected in Hα filaments.
Authors: Schmieder, B.; Thompson, W. T.; Mein, P.
1990PDHO....7..296S Altcode:
The authors report some new observations of oscillations in filaments
observed at different positions on the disk using the MSDP spectrograph
operating at Meudon. The velocity power spectra made over whole filament
regions show a smooth maximum around 200 s period. Oscillations
are detected principally in discrete areas in the filaments and in
chromospheric fibrils, with well defined periods around 250 s and 150
s. The oscillations could be interpreted by Alfvén waves generated
in the chromosphere and propagating through magnetic filamentary
structures or by eigenmodes of filamentary structures excited by
chromospheric p-modes.

---------------------------------------------------------
Title: Dynamical Structure of a Quiescent Prominence
Authors: Mein, P.; Mein, N.; Schmieder, B.; Noëns, J. C.
1990LNP...363..252M Altcode: 1990doqp.coll..252M; 1990IAUCo.117..252M
A statistic analysis of H profiles in a quiescent prominence is
consistent with the superposition of individual velocity structures
(typically 10), with standard deviation ~ 15 km s-1.

---------------------------------------------------------
Title: Hα diagnostics of 16 May 1981 flare loops.
Authors: Heinzel, P.; Mein, P.; Schmieder, B.
1990PDHO....7..272H Altcode:
MSDP observations (Meudon) of 16 May 1981 post-flare loops are used
to derive the hydrogen plasma parameters in flare loops. The authors
compare two recently developed methods: a differential cloud model
and a probabilistic transfer technique.

---------------------------------------------------------
Title: Interaction between Bipolar Sunspot Groups
Authors: Csepura, G.; van Driel-Gesztelyi, L.; Nagy, I.; Gerlei, O.;
Schmieder, B.; Rayrole, J.
1990PDHO....7...88C Altcode: 1990ESPM....6...88C; 1990dysu.conf...88C
The authors find some evidence for the interaction of two close-by
developing sunspot groups.

---------------------------------------------------------
Title: Formation of a Filament around a Magnetic Region
Authors: Schmieder, B.; Démoulin, P.; Ferreira, J.; Alissandrakis,
C. E.
1990LNP...363..232S Altcode: 1990doqp.coll..232S; 1990IAUCo.117..232S
The evolution of the active region AR4682 observed in 1985 during six
rotations was dominated by three different phenomena: . the large
scale pattern activity: relationship between two active regions,
formation of a quiescent filament during the decay phase of the
active region, . the presence of two pivot points along the filament
surrounding the sunspot-with the long term one is associated the
existence of the filament, with the short term one the activity with
partial disappearance, . the magnetic shear during one rotation. The
magnetic field lines have been extrapolated from photospheric data
using Alissandrakis code (1981). The magnetic configuration with the
existence of a dip favors the formation of a filament. We note that
the shearing of the sunspot region and of the filament are both well
described by force-free magnetic fields with the same constant α. This
suggests that they are both a consequent of the same shear process.

---------------------------------------------------------
Title: High Resolution Spectrography in Ultraviolet
Authors: Schmieder, B.; Thompson, W. T.; Neupert, W. M.; Thomas,
R. J.; Dere, K. P.
1990PDHO....7..250S Altcode: 1990ESPM....6..250S; 1990dysu.conf..250S
The authors point out some of the advantages of coordinated observations
with ground-based and space instrumentation. Results obtained during
the rocket flight of the Solar Extreme-ultraviolet Rocket Telescope
and Spectrograph (SERTS) for a preflaring region are presented and the
complementarity of observations is pointed out with the High Resolution
Telescope and Spectrograph (HRTS) which permits the detection of
dynamical structures in hot plasma surrounding cool structures such
as prominences and sunspots seen in visible light.

---------------------------------------------------------
Title: Mass Motion in and around Prominences
Authors: Schmieder, B.
1990LNP...363...85S Altcode: 1990IAUCo.117...85S; 1990doqp.coll...85S
The mass of a quiescent prominence is equivalent to one-tenth of the
all coronal plasma. It is obvious that this crucial problem is resolved,
now if we consider the dynamical nature of prominences. Observations of
motions of filaments will be reviewed in regard to their time scales:
. solar cycle (slow migration of filaments, pivot points, convection)
. days or hours (stationary motions, oscillations) . hours or minutes
(appearance or disparition brusque, eruption) These motions will
be discussed in view of a better understanding of the formation of
filaments (chromospheric injection or coronal plasma condensation),
stability of the fine structures, existence of the feet, relationship
of the DB, and the coronal mass ejections.

---------------------------------------------------------
Title: Evolution of Fine Structures in a Filament
Authors: Schmieder, B.; Mein, P.
1990LNP...363..235S Altcode: 1990doqp.coll..235S; 1990IAUCo.117..235S
A quiescent filament observed in June 1986 underwent a slow Disparition
Brusque which lasted 4 days. Here, we focus our study on the dynamical
behaviour of the fine structures ( Full-Width Half-Max ~ 350 km) in
this filament which were observed at Pic du Midi with the Multi-Channel
Subtractive Double Pass (MSDP) spectrograph during a period of 30
minutes. We observed no changes in intensity during this period, but
we did observe changes in the velocity field with no correlation from
one minute to the next. High velocities were detected at the footpoints
where the filament is anchored in the photosphere , of the same order
than those observed at the boundaries of the supergranules (between
±10 km s-1). To explain these observations we suggest a spicule-like
model which supplies material to the prominence.

---------------------------------------------------------
Title: Overall properties and steady flows
Authors: Schmieder, B.
1989ASSL..150...15S Altcode: 1988dsqs.work...15S; 1989dsqs.work...15S
Since the publication of the book 'Solar Prominences' (Tandberg-Hanssen,
1974), prominences have been the subject of many theoretical and
observational studies, as discussed and summarized in several reviews
(Hirayama, 1985; Poland, 1986; Malherbe, 1987). The present paper
presents recent progress, mostly from an observational point of
view, in the understanding of the formation, structure, support, and
instabilities of solar prominences. Results of spectroscopic diagnostics
(velocity, temperature and density) are stressed.

---------------------------------------------------------
Title: Evolution of Fine Structures in a Filament
Authors: Schmieder, B.; Mein, P.
1989HvaOB..13...31S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Flare Dynamics
Authors: Zarro, D.; Alexander, D.; Fludra, A.; Emslie, G.; Gurman, J.;
Graeter, M.; Li, P.; Phillips, K.; Saba, J.; Schmieder, B.; Slater,
G.; Wulser, J. P.; Watanabe, T.; Dulk, G.; MacKinnon, A.; McClements,
K.; Spicer, D.
1989tnti.conf....2Z Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A surge in the chromosphere and the transition region:
velocities and microturbulence.
Authors: Mein, P.; Schmieder, B.; Tandberg-Hanssen, E.
1989sasf.confP.223M Altcode: 1989IAUCo.104P.223M; 1988sasf.conf..223M
Simultaneous observations of a surge in Hα and C IV are analysed in
terms of Doppler velocities and "microturbulence". The behaviour of both
quantities suggests strong velocity shears with small spatial scales.

---------------------------------------------------------
Title: Dynamical Structure of a Quiescent Prominence
Authors: Mein, P.; Mein, N.; Schmieder, B.; Noens, J. C.
1989HvaOB..13..113M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Formation of a Filament around a Magnetic Region
Authors: Schmieder, B.; Demoulin, P.; Ferreira, J.; Alissandrakis,
C. E.
1989HvaOB..13....1S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: An example of the association of X-ray and UV emission with
H-alpha surges
Authors: Schmieder, B.; Mein, P.; Simnett, G. M.; Tandberg-Hanssen, E.
1988A&A...201..327S Altcode:
From H-alpha UV, and X-ray data, the nature of a well-observed
surge on November 12, 1980 has been studied to try to understand the
relationships between the mechanical motions and the high-temperature
emissions. The cool (H-alpha) and the hot (O v) parts of the surge
plasma both show velocities in the range of 100-120 km/s. The kinetic
and potential energies of the surge are two orders of magnitude
higher than the radiative energy. The observations suggest that the
surge occurs in open structures parallel to one leg of a large scale
coronal magnetic loop. The energy is released principally in the open
structure (surge) and only a small amount heats the coronal loop (X-ray
signature). This energy division should probably not be treated as a
general characteristic of surge events. Different events are expected
to exhibit a different energy balance, and this can account for the
lack of a consensus in the previous literature regarding surge/X-ray
associations.

---------------------------------------------------------
Title: The Evershed flow in the solar photosphere, chromosphere and
chromosphere-corona transition region
Authors: Alissandrakis, C. E.; Dialetis, D.; Mein, P.; Schmieder,
B.; Simon, G.
1988A&A...201..339A Altcode:
The authors have studied the height dependence of the characteristics
of the Evershed flow in the photosphere, chromosphere and
chromosphere-corona transition region. The Multichannel Subtractive
Double Pass Spectrograph was used to obtain line of sight velocity maps
in Hα, the Meudon magnetograph for mapping the photospheric velocity
and magnetic field and the Ultraviolet Spectrometer and Polarimeter on
the Solar Maximum Mission spacecraft for line-of-sight velocities in C
IV, in sunspot regions. The observations are practically simultaneous in
the three atmospheric levels and cover three consecutive days (Sep 28,
29 and 30, 1980). The emphasis was on the large scale, quasi-stationary
characteristics of the flow.

---------------------------------------------------------
Title: Photospheric-induced destabilization and ejection of prominence
material
Authors: Raadu, M. A.; Schmieder, B.; Mein, N.; Gesztelyi, L.
1988A&A...197..289R Altcode:
The sequence of events leading up to prominence activation in two
different cases is studied. In one case, observed on September 3, 1980,
strong velocity shears were produced indicating filament twisting. In
the other case, observed on June 22, 1980, activation results in the
ejection of prominence material. The paper presents new evidence for a
common initial triggering mechanism, the birth or motion of pores at one
end of the activated filament sections. This is taken as an indication
of emerging magnetic flux and current induction in the filaments. The
difference in the final results is partly due to the different ambient
magnetic field structures. In particular in the case leading to material
ejection there is a subsequent associated flare occurred indicating
the storage of magnetic energy in the region. Models are proposed for
the two sequences of events, clarifying the underlying similarities
and interpreting the distinct features of the two sets of observations.

---------------------------------------------------------
Title: Some dynamical aspects of a quiescent filament
Authors: Schmieder, B.; Demoulin, P.; Poland, A.; Thompson, B.
1988A&A...197..281S Altcode:
A typical quiescent filament was observed on the disk in the Hα
and C IV lines during a period of approximately one hour. Vertical
velocities (&lt;2.5 km s-1) with a time scale of 5 min and
a spatial scale of a few tens of seconds of arc were detected in Hα,
and associated with microturbulence in both lines. The C IV observations
correlated well with those in Hα, and showed no indication of material
heating from Hα to C IV temperatures. Two mechanisms to explain these
observations are proposed: mass motion along twisted magnetic field
or instabilities triggering waves along the filament.

---------------------------------------------------------
Title: Variations of the Solar Limb Brightness with the Oscillations
Authors: Schmieder, B.; Mein, P.
1988IAUS..123..429S Altcode:
The aim of this work is to compute the amplitude of the limb darkening
fluctuations due to oscillations in order to compare it with the
observations made with the heliometer at the Pic du Midi (Rösch
and Yerle 1983 - 1984). It is shown that 5 min oscillations lead to
variation in the brightness gradient of less than 2%.

---------------------------------------------------------
Title: Environment and dynamics of a prominence observed at Pic
du Midi.
Authors: Noëns, J. C.; Schmieder, B.; Mein, P.
1988dssp.conf..177N Altcode:
Simultaneous observations were made at Pic du Midi using the 20 cm
Coronograph and the Multichannel Subtractive Double Pass spectrograph
operating in the "Coupole Tourelle". The prominence observed on June
17, 1987 is composed of three principal vertical structures 50000 km
high with faint material connecting then. A coronal cavity is visible
above the prominence. The dynamics of this prominence in Hα is large,
horizontal circulation is observed. Images in Hα versus time show
a slow evolution in the general shape with an exchange of material
between the vertical structures.

---------------------------------------------------------
Title: Velocity shear and microturbulence in solar filaments a
differential cloud model.
Authors: Mein, P.; Schmieder, B.
1988dssp.conf...17M Altcode:
The authors analyse the time sequence of an active region
filament observed at the MSDP of the Meudon Solar Tower. They use a
"differential cloud model" which is well suited to the interpretation
of Hα profiles with an inhomogeneous chromospheric
background. A previous model (Schmieder et al. 1985) suggesting twisting
motions of magnetic ropes is confirmed.

---------------------------------------------------------
Title: Overall properties and steady flows.
Authors: Schmieder, B.
1988dssp.conf....5S Altcode:
A description and a classification of some of the different types
of prominences observed is presented. The importance of filaments
as tracers of the general magnetic field is indicated. From the
spectroscopic diagnostics, density, temperature, microturbulence and
velocity are deduced under, in and around filmants using photospheric,
chromospheric and EUV lines. Activation of filaments is due to
instabilities. The causes and the consequences of these instabilities
are reviewed.

---------------------------------------------------------
Title: The Role of the Observatoire de Paris, Meudon in Providing
Astronomical Information
Authors: Floquet, M.; Schmieder, B.
1988scaa.conf..224F Altcode: 1988IAUCo..98..224F
No abstract at ADS

---------------------------------------------------------
Title: Post-flare loops: formation and velocity
Authors: Schmieder, B.; Mein, P.; Malherbe, J. -M.; Forbes, T. G.
1988AdSpR...8k.145S Altcode: 1988AdSpR...8..145S
Post-flare loops are generally observed between two ribbon flares. The
formation of post flare loops and active region or plage filaments
has been explained in a model based on magnetic reconnection and
chromospheric ablation /1,2/. This model uses a magnetic topology
which is relevant to solar flares /3/ : a large flare or an instability
opens the magnetic lines of a coronal arcade (or arch) and a vertical
current sheet forms. Then the reconnection of the magnetic field
follows according to the scenario of Kopp and Pneuman /4/. In this
magnetic configuration, we show that the formation of condensations
or dense loops is induced by reconnection shocks. We give in
this communication a new method of diagnostic to derive from Hα
profiles physical parameters, i.e. source function, optical depth and
velocity. This method called “differential cloud method” is very
promising for future observations.

---------------------------------------------------------
Title: Chromospheric and Transition Zone Flows in a Solar Active
Region
Authors: Dere, K. P.; Schmieder, B.
1987BAAS...19.1118D Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Closed Magnetic Structures in the Chromosphere and in the
Transition Region
Authors: Malherbe, J. M.; Schmieder, B.; Simon, G.; Mein, P.;
Tandberg-Hanssen, E.
1987SoPh..112..233M Altcode:
Using simultaneous observations of the same solar regions in the
lines Hα and CIV 1548 Å, we have derived schematic models of closed
magnetic lines from dynamical constraints. We conclude that the magnetic
loops are closed at higher levels above facular than above non-facular
regions. This result remains valid whatever are the assumed density
models and even if we take into account the 3 min oscillations. The
center-to-limb behaviour is well predicted by taking into account the
relative opacity in chromosphere and transition region.

---------------------------------------------------------
Title: Fine structures in solar filaments. I - Observations and
thermal stability
Authors: Demoulin, P.; Malherbe, J. M.; Schmieder, B.; Raadu, M. A.
1987A&A...183..142D Altcode:
Limb observations of quiescent prominences show very fine structures of
less than one arcsecond. Here H-alpha observations on the disk, made
with the Multichannel Subtractive Double Pass spectrograph operating
at the Observatoire du Pic du Midi are presented. They show long
fine structures in the body of the filament, both in intensity and
velocity maps. Many prominence models ignore such fine structures and
suppose that the quiescent filament is a uniform body such as is seen
in unresolved images. It has been suggested that in a current-sheet
model of a prominence, fine structures may be produced as a consequence
of the tearing mode coupled to thermal instability. Here the role of
parallel and orthogonal conduction on the stability of a periodic fine
structure is investigated. Equilibrium conditions are found and growth
rates determined for linear perturbations.

---------------------------------------------------------
Title: Evidence for Gentle Chromospheric Evaporation during the
Gradual Phase of Large Solar Flares
Authors: Schmieder, B.; Forbes, T. G.; Malherbe, J. M.; Machado, M. E.
1987ApJ...317..956S Altcode:
The Multichannel Subtractive Double Pass Spectrograph of the Meudon
solar tower is used to obtain high spatial resolution H-alpha line
profiles during the gradual phase of three solar flares. In all cases,
small blueshifts lasting for several hours are observed in the flare
ribbons. By contrast, the region between the two ribbons exhibits
large redshifts that are typical of H-alpha post flare loops. The
blueshifts in the ribbons is interpreted as upward chromospheric flows
of 0.5-10 km/s, and the possible ambiguities of the interpretation
are discussed. A preliminary analysis indicates that such upflows are
sufficient to supply the greater than 10 to the 16th g of mass needed
to maintain a dense H-alpha postflare loop system in the corona.

---------------------------------------------------------
Title: Material Ejecta in a Disturbed Solar Filament
Authors: Raadu, M. A.; Malherbe, J. M.; Schmieder, B.; Mein, P.
1987SoPh..109...59R Altcode:
Hα observations, using the Multichannel Subtractive Double Pass
(MSDP) spectrograph operating on the Meudon Solar Tower, have been
made of an active region filament which undergoes a `disparition
brusque'. The period of observation was from 10 ∶ 45 to 13 ∶ 30
UT on 22 June, 1981. Velocity and intensity fluctuations in Hα were
measured. The proper motions of ejecta were followed allowing their
trajectories and vector velocities to be determined. To model the
dynamics of ejecta several models using thermal or magnetic driving
forces are compared. The most promising model explains the motion as
the consequence of magnetic stresses acting on an isolated magnetized
plasmoïd in a diverging flux tube.

---------------------------------------------------------
Title: Photospheric Induced Destabilization and Ejection of Prominence
Material
Authors: Raadu, M. A.; Schmieder, B.; Mein, N.; Gesztelyi, L.
1987HvaOB..11..105R Altcode:
The cause of the sudden activation of solar prominences is not
clear. The authors present observations of two cases which were preceded
by the emergence and motion of pores (new flux) in the near vicinity
of the filaments, which seem to be closely related to the process which
triggered the filament destabilization. These observations may be well
described by a theoretical model in which the new flux interacts with
the older "stable" magnetic field.

---------------------------------------------------------
Title: Dynamics of solar filaments. V - Oscillations in the H-alpha
and 1548 A C IV lines
Authors: Malherbe, J. M.; Schmieder, B.; Mein, P.; Tandberg-Hanssen, E.
1987A&A...172..316M Altcode:
Using the Multichannel Subtractive Double Pass Spectrograph operating in
the Meudon solar tower and the Ultraviolet Spectrometer and Polarimeter
aboard the Solar Maximum Mission satellite, the authors analyze by
Fourier transform technique time sequence observations of filaments in
both the Hα line and in the 1548 Å C IV line. The Hα data confirm
previous findings that there are no oscillations at the location of
the filament in the observed range 1 - 10 mHz. In the C IV line the
authors observe power in some parts of the filament where a steady
velocity gradient is present, e.g. in the footpoints. The energy is
probably due to convective motions rather than pressure oscillations.

---------------------------------------------------------
Title: Environment and Dynamics of a Prominence Observed at Pic-Du
Authors: Noens, J. C.; Schmieder, B.; Mein, P.
1987dssp.work..177N Altcode: 1987ASSL..150..177N
No abstract at ADS

---------------------------------------------------------
Title: Overall Properties and Steady Flows
Authors: Schmieder, B.
1987dssp.work....5S Altcode: 1987ASSL..150....5S
No abstract at ADS

---------------------------------------------------------
Title: On the onset of eruptive prominences and coronal transients.
Authors: Simon, G.; Mein, N.; Schmieder, B.; Tandberg-Hanssen, E.;
Wu, S. T.
1987PAICz..66..211S Altcode: 1987eram....1..211S
During the Maximum Year, preflare and preeruptive phenomena have
been observed which give a new idea on the association of eruptive
prominences and coronal transients.

---------------------------------------------------------
Title: Surges as tracers of magnetic lines.
Authors: Schmieder, B.; Mein, P.; Martres, M. J.; Simnett, G.;
Tandberg-Hanssen, E.
1987PAICz..66..109S Altcode: 1987eram....1..109S
The authors focus their study to chromospheric mass ejecta of
cool material visible in Hα and occurring, with or without any
flare. Associated with the events are either X ray emission or type
III bursts.

---------------------------------------------------------
Title: Velocity Shear and Microturbulence in Solar Filaments
Authors: Mein, P.; Schmieder, B.
1987dssp.work...17M Altcode: 1987ASSL..150...17M
No abstract at ADS

---------------------------------------------------------
Title: On the existence of oscillations in solar filaments observed
in H&amp;alpha; and C IV lines.
Authors: Schmieder, B.; Malherbe, J. M.; Mein, P.; Tandberg-Hanssen, E.
1986NASCP2442..197S Altcode:
Time sequence observations of filaments in both the
H&amp;alpha; line and the 1548 Å C IV line were analyzed
with the Fourier transform technique in the frequency range (1 - 10
mHz). No oscillation is detected in filaments except at the footpoints
where a steady velocity gradient is large. The energy is probably due
to convective motions rather than pressure oscillations.

---------------------------------------------------------
Title: Thermal stability analysis of the fine structure of solar
prominences.
Authors: Demoulin, Pascal; Malherbe, Jean-Marie; Schmieder, Brigitte;
Raadu, Mickael A.
1986NASCP2442..143D Altcode:
The authors analyse the linear thermal stability of a 2D periodic
structure (alternatively hot and cold) in a uniform magnetic
field. The energy equation includes wave heating (assumed proportional
to density), radiative cooling and both conduction parallel and
orthogonal to magnetic lines. The equilibrium is perturbed at constant
gas pressure. The results compared with observations show that the
computations suggest that the size of the unresolved threads could be
of the order of 10 km only.

---------------------------------------------------------
Title: Filament eruption connected to photospheric activity.
Authors: Simon, G.; Gesztelyi, L.; Schmieder, B.; Mein, N.
1986NASCP2442..229S Altcode: 1986copp.nasa..229S
Two cases of activation of filaments that occured in regions of
intense magnetic activity was studied. The simultaneous observations
from Debrecen Observatory (white light and H alpha filtergram), and
from Meudon Observatory (magnetogram, MSDP dopplergram and intensity
maps in H alpha) gave a complementary set of data from which can be
produced evidence of the influence of the photospheric magnetic field
on the destabilization process of the filaments. On June 22, 1980,
the eruption of the filament is associated with the motion of pores,
which are manifestations of emerging flux knots. On September 3, 1980,
the twisting motions in the filament are associated to the birth of
a pore in its neighborhood. These observations are discussed.

---------------------------------------------------------
Title: Material ejecta in a disturbed solar filament
Authors: Raadu, Michael A.; Malherbe, Jean-Marie; Schmieder, Brigitte;
Mein, Pierre
1986STIN...8722594R Altcode:
H alpha observations, using a multichannel subtractive double pass
spectrograph were made of an active region filament which undergoes
a sudden disappearance. The period of observation was from 10:45 UT
to 13:30 UT on 22 June, 1981. Velocity and intensity fluctuations
in H alpha were measured. The proper motions of ejecta were followed
allowing their trajectories and vector velocities to be determined. To
model the dynamics of ejecta, models using thermal or magnetic driving
forces are compared. The most promising model explains the motion as
the consequence of magnetic stresses acting on an isolated magnetized
plasmoid in a diverging flux tube.

---------------------------------------------------------
Title: Constraints on filament models deduced from dynamical analysis.
Authors: Simon, G.; Schmieder, B.; Demoulin, P.; Malherbe, J. M.;
Poland, A. I.
1986NASCP2442..177S Altcode: 1986copp.nasa..177S
The conclusions deduced from simultaneous observations with the
Ultra-Violet Spectrometer and Polarimeter (UVSP) on the Solar Maximum
Mission satellite, and the Multichannel Subtractive Double Pass (MSPD)
spectrographs at Meudon and Pic du Midi observatories are presented. The
observations were obtained in 1980 and 1984. All instruments have
almost the same field of view and provide intensity and velocity maps
at two temperatures. The resolution is approx. 0.5 to 1.5" for H alpha
line and 3" for C IV. The high resolution and simultaneity of the two
types of observations allows a more accurate description of the flows
in prominences as functions of temperature and position. The results
put some contraints on the models and show that dynamical aspects must
be taken into account.

---------------------------------------------------------
Title: Dynamics of solar filaments. VI - Center-to-limb study of
H-alpha and C IV velocities in a quiescent filament
Authors: Simon, G.; Schmieder, B.; Demoulin, P.; Poland, A. I.
1986A&A...166..319S Altcode:
The rotation of a stable quiescent filament from near disk center to
the limb has been observed. Observations of intensity and velocity
were made in H-alpha and C IV, and compared with magnetic field
measurements. From the H-alpha observations, it is concluded that the
filament is made up of many small scale magnetic features that are
not coherently aligned along the neutral line. They are especially
convoluted at the apparent 'footpoints'. The measured velocities are
of the order of a few kilometers per second in both lines. However,
the comparison of the standard deviations of the C IV velocities in
and out of the filament as it rotates toward the limb shows that the
vertical velocities in the filament are greater than the horizontal
velocities. Measurements of velocity do not make it possible to
distinguish between the Raadu-Kuperus (1973) or Kippenhahn-Schluter
(1957) models for prominences because neither theory is adequately
developed for this comparison. However, the observation of the many
fine loops brings into question the correctness of either model.

---------------------------------------------------------
Title: The effect of solar oscillations on the brightness of the limb
Authors: Schmieder, B.; Mein, P.
1986A&A...161....7S Altcode:
Using the realistic atmosphere model VALC, and assuming a spherical
geometry, the intensity of the solar limb is calculated, and measured
amplitude fluctuations are compared with those expected due to
oscillations. In the model, the atmosphere is perturbed successively
by density and temperature fluctuations of amplitude smaller than the 6
percent limiting value, and the perturbations are defined by exponential
laws corresponding to propagating or evanscent waves. It is shown that
5-minute oscillations lead to variations in the brightness gradient of
less than 2 percent. Limb brightness fluctuation amplitudes observed
with the Pic du Midi heliometer (Yerle, 1981) show peaks of 10 percent
which have too high a value to be explained by solar wave theory.

---------------------------------------------------------
Title: Preflare activity.
Authors: Priest, E. R.; Gaizauskas, V.; Hagyard, M. J.; Schmahl, E. J.;
Webb, D. F.; Cargill, P.; Forbes, T. G.; Hood, A. W.; Steinolfson,
R. S.; Chapman, G. A.; Deloach, A. C.; Gary, G. A.; Jones, H. P.;
Karpen, J. T.; Martres, M. -J.; Porter, J. G.; Schmieder, B.; Smith,
J. B., Jr.; Toomre, J.; Woodgate, B.; Waggett, P.; Bentley, R.;
Hurford, G.; Schadee, A.; Schrijver, J.; Harrison, R.; Martens, P.
1986NASCP2439....1P Altcode:
Contents: 1. Introduction: the preflare state - a review of previous
results. 2. Magnetohydrodynamic instability: magnetic reconnection,
nonlinear tearing, nonlinear reconnection experiments, emerging flux and
moving satellite sunspots, main phase reconnection in two-ribbon flares,
magnetic instability responsible for filament eruption in two-ribbon
flares. 3. Preflare magnetic and velocity fields: general morphology of
the preflare magnetic field, magnetic field shear, electric currents in
the preflare active region, characterization of the preflare velocity
field, emerging flux. 4. Coronal manifestations of preflare activity:
defining the preflare regime, specific illustrative events, comparison
of preflare X-rays and ultraviolet, preflare microwave intensity and
polarization changes, non-thermal precursors, precursors of coronal
mass ejections, short-lived and long-lived HXIS sources as possible
precursors.

---------------------------------------------------------
Title: Characteristics, location and origin of flare activity in a
complex active region
Authors: Mechado, M. E.; Gary, G. A.; Hagyard, M. J.; Hernandez,
A. M.; Rovira, M. G.; Schmieder, B.; Smith, J. B.
1986AdSpR...6f..33M Altcode: 1986AdSpR...6...33M
We summarize the observational characteristics of series of multiple
loop flares from a complex active region. The location of the
highest observed photospheric magnetic shear is found to be the
commonly observed site of flare onset, but not, in many cases, the
magnetic region where the largest time-integrated energy release is
observed. The observations thus reveal a consistent pattern of energy
release processes as related to the magnetic field topology.

---------------------------------------------------------
Title: Dynamics of solar filaments. IV - Structure and mass flow of
an active region filament
Authors: Schmieder, B.; Malherbe, J. M.; Simon, G.; Poland, A. I.
1985A&A...153...64S Altcode:
An active region filament near the center of the solar disk was observed
on September 29-30, 1980, with the Multichannel Subtractive Double Pass
Spectrograph of the Meudon solar tower and the UV Spectrograph and
Polarimeter aboard the SMM satellite. H-alpha and C IV measurements
are presently used to study brightness and material velocity in the
10,000 and 100,000 K temperature ranges, and photospheric magnetograms
are used to investigate the underlying magnetic field. Attention is
given to the constraints imposed on possible filament structures by
observations, as well as the expected MHD relationships.

---------------------------------------------------------
Title: Mass motions in Hα absorbing structures of the solar
chromosphere.
Authors: Mein, P.; Malherbe, J. M.; Mein, N.; Mouradian, Z.;
Schmieder, B.
1985MPARp.212..316M Altcode:
Two examples of Hα absorbing structures have been observed with the
Multichannel Subtractive Double Pass spectrograph at the turret dome
(Pic du Midi) and at the solar tower (Meudon). In both cases, 9 points
of the line profile are measured simultaneously in a 2D-field of view.

---------------------------------------------------------
Title: Twisting motions in a disturbed solar filament
Authors: Schmieder, B.; Malherbe, J. M.; Raadu, M. A.
1985A&A...142..249S Altcode:
Time sequences of the vertical velocity field in a disturbed solar
active region filament (AR 2646) have been derived using the MSDP
spectrograph operating in Hα at the Meudon Solar Tower. Following
a period of systematic upward velocities a pair of closely aligned
elongated regions of oppositely directed velocities develops and
persists over several minutes. These velocities are interpreted in
terms of a twisted magnetic flux rope model for the filament. The
initial upward motions indicate that the flux rope is rising. This
should lead to an expansion since the surrounding pressure is decreasing
with height. Conservation of the current and the magnetic flux along
the filament then requires twisting motions as the flux rope adjusts
to a new radial equilibrium when rising into the corona.

---------------------------------------------------------
Title: Bright Points in H Wings and Mass Flows in the Solar
Chromosphere
Authors: Mein, P.; Malherbe, J. -M.; Mouradian, Z.; Mein, N.;
Schmieder, B.; Muller, R.
1985LNP...233..203M Altcode: 1985hrsp.proc..203M
Many mass flows in the chromosphere are physically connected with
bright photospheric points. Bidimensional spectroscopy with high
spatial resolution is very well suited for the study of both kinds
of structures. The authors give some preliminary results derived from
recent observations of the MSDP at the Pic-du-Midi.

---------------------------------------------------------
Title: Mass fluxes and magnetic structures in the chromosphere and
the transition region; canopies.
Authors: Mein, P.; Malherbe, J. -M.; Schmieder, B.; Simon, G.;
Tandberg-Hanssen, E.
1985cdm..proc..206M Altcode:
Preliminary results of applying a model of canopy-type magnetic
lines to account for observed mass fluxes in the chromosphere and
transiton region are presented. A set of center-to-limb data obtained in
H-alpha and C IV, and to which the model is applied, is reported. The
C IV line is assumed to form everywhere at the same height, and the
H-alpha formation height is derived by assuming that the absorption
coefficient is proportional to the local density. The density ratio
between H-alpha and C IV levels is taken to be 100. From the results,
it is concluded that the model accounts for the low ratio of radial
velocities C IV/H-alpha at r = 0, the increase of H-alpha velocity
near the limb, and the general center-to-limb behavior in both lines.

---------------------------------------------------------
Title: Recent Progress in the Physics of Solar Prominences
Authors: Ribes, E.; Mein, P.; Malherbe, J. M.; Schmieder, B.
1985spit.conf..467R Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Dynamic evolution of recurrent mass ejections observed in
Hα and C iv lines
Authors: Schmieder, B.; Mein, P.; Martres, M. J.; Tandberg-Hanssen, E.
1984SoPh...94..133S Altcode:
During a coordinated SMY program, the consecutive formation of two new
active centers merging together within AR 2646 was observed from 28
August, to 5 September, 1980. The two preceding spots compressed an
inverse polarity spot on 1 September 1980, causing recurrent ejecta
of matter with time intervals around 10 min. The observations of the
MSDP spectrograph operating in Hα at the Meudon Solar tower and of
the UVSP spectrometer on SMM in the CIV 1548 Å line show that cold
and hot material had the same projection, although the upward CIV
velocity structure was more extended than the Hα one. We present
evidence that observed contrasts of the Hα absorbing structure
can be interpreted in terms of a dynamic `cloud model' overlying
the chromosphere. Hα matter follows a magnetic channel with upward
velocity around 20-30 km s−1 in the first phase of the
event and with downward velocity (∼ - 40 km s−1) in the
second phase. The stored energy is not sufficient to trigger a flare,
nor even to propulse matter along the full length of an arch, because
of the periodic reorganisation of the magnetic field.

---------------------------------------------------------
Title: Dynamics of solar filaments. III - Analysis of steady flows
in H-alpha and C IV lines
Authors: Schmieder, B.; Malherbe, J. M.; Mein, P.; Tandberg-Hanssen, E.
1984A&A...136...81S Altcode:
A statistical analysis of intensities and radial velocities of
several solar plage filaments (i.e. prominences seen on the solar
disk) observed at disk center is presented. Intensity and radial (=
vertical) velocity maps were derived from simultaneous 2D measurements
of the H-alpha chromospheric line with the Multichannel Subtractive
Double Pass spectrograph operating on the Meudon solar tower, and also
obtained from 2D recordings of the C IV transition-zone line (1548 A)
with the UV Spectrometer and Polarimeter aboard the Solar Maximum
Mission satellite. A good correlation (around 0.5) is found between
intensities in both lines, as well as between velocities. Persistent
upflows are measured in both lines at the filament location. The mean
vertical velocities are respectively 0.5 km/s in H-alpha and 5.6 km/s
in C IV. The analysis of mass fluxes suggests that C IV upflows occur
in the transition region around prominences rather than below, in the
chromosphere-corona transition zone.

---------------------------------------------------------
Title: Phase-spectra of solar oscillations
Authors: Staiger, J.; Mattig, W.; Schmieder, B.; Deubner, F. -L.
1984MmSAI..55..147S Altcode:
Diode array measurements of intensity- and velocity-oscillations
were made at the coude-telescope of Capri. From these observations
phase-spectra were calculated to identify different types of waves
within the solar atmosphere. The results indicate the existence of
atmospheric gravity modes in the frequency-range below 2.5 mHz. No
running acoustic waves were found in the photosphere for frequencies
beyond 7.5 mHz. Vertical propagation seems only to take place for
frequencies between 5 mHz and 7.5 mHz. No vertical propagation at
all was found in the upper chromosphere. This seems to be due to the
occurrence of wave reflection at the chromosphere-corona interface.

---------------------------------------------------------
Title: Study of giant cell motions and their possible relationship
with the dynamics of filaments
Authors: Schmieder, B.; Ribes, B.; Mein, E.; Malherbe, J. M.
1984MmSAI..55..319S Altcode:
The systematic upward motions observed in filaments are presently
considered in terms of a large scale convective flow, so that the
converging or diverging direction of the subphotospheric flow is
related to the magnetic pattern suggested by Kuperus and Raadu (1973)
and Kippenhahn and Schlueter (1957). This scheme is tested by means of
a method for the detection of the giant convection and its properties,
through a differential rotation analysis that uses sunspots, faculae
and filaments as outliners. The systematic latitudinal motions
obtained in the preliminary results indicate the presence of large
scale convection. The method may be used to establish a relationship
between the magnetic pattern and the global convection.

---------------------------------------------------------
Title: Oscillations and stationary motions in filaments
Authors: Schmieder, B.; Malherbe, J. M.; Mein, P.; Tandberg-Hanssen, E.
1984MmSAI..55..325S Altcode:
Observation of oscillations in filaments, which are cold magnetic
structures suspended in the corona, are used to test theories of
coronal heating by acoustic waves high in the atmosphere. Long lived
stationary motions observed in filaments suggest exchanges of material
between them and the surrounding corona. A coupling between upflows in
filaments and subphotospheric convective motions, dragging the field
lines of the prominence magnetic support, is possible.

---------------------------------------------------------
Title: Flare build-up study - Homologous flares group - Part I
Authors: Martres, M. -J.; Woodgate, B. E.; Mein, N.; Mouradian, Z.;
Rayrole, J.; Schmieder, B.; Simon, G.; Soru-Escaut, I.
1984AdSpR...4g...5M Altcode: 1984AdSpR...4....5M
According to the definition of the homology (optical) kept in reference,
the homologous flares (HFl) may be observed wherever flares occur. The
supposed supplementary preflaring conditions to have HFl may be either
that the preflaring conditions have not been destroyed by the first
flare (and then what mechanism has stopped the first and triggered the
second ?) or that the preflaring conditions have been destroyed and
rebuilt (and then, how ?). The analysis of data related to some selected
active regions AR by the members of the working group, and the earlier
works on HFl, may be used simultaneously to investigate the differences
between one set of HFl and the others, the location of their sites and
the evolution of HFl productive AR. This study brings the appearance of
new footpoints from one flare to the following, the behaviour of cool
arches (surging arches) leading to information on the changes of the
magnetic configuration, and to peculiar characteristics of HFl, oif
2nd, 3rd in the time order concerning the chromospheric transition
zone or coronal regions. The time delay between two consecutive
homologous flares appears very quickly as an essential parameter to
study homology. It was found that every set of flares (same type of
site) is able to produce “rafales” of homologous flares, i.e. two,
three, four, oir more flares with Δt in the range of one hour or
less. The observations show no great chantes in macroscopic photospheric
patterns (B, V) during this H flaring period. They lead to compare
their temporal variation curves of flare brightness. A quantitative
brightness parameter of homology relation has been defined. Some scale
changes have also been detected in the dynamic spectrum of the site, and
it is in good agreement with a very interesting theoretical suggestion
made by P. Sturrock to produce such “rafales”. It may be shown that
the closely consecutive time-homologous flares (CCHF) or “rafales”
represent a good tool to analyse the critical conditions related to
the origin and the amount of energy, mechanism of storage and release,
necessary and, perhaps, sufficient conditions. New statistical results,
applied to the different selected homologous flare active regions
are presented and show the existence in homologous flaring areas of
a “pivot” of previous filaments interpreted as a signature of an
anomaly in the Solar rotation.

---------------------------------------------------------
Title: Recurrent mass ejections observed in Hα and CIV
Authors: Schmieder, B.; Simon, G.; Martres, M. -J.; Mein, P.; Mein,
N.; Tandberg-Hanssen, E.
1984AdSpR...4g..27S Altcode: 1984AdSpR...4...27S
Time sequences of recurrent mass ejections have been observed during a
coordinated SMY program (1 Sept. 1980 - 23 Sept. 1980 - 2 Oct. 1980). Comparison of the temporal evolution of Hα and CIV
brightnesses shows a weak phase lag between H α and CIV maxima, in
the case of homologous flares, with CIV brightness maxima preceding H
α maxima. The analysis of the variation of the ejection velocities
is expected to lead to the determination of an energy balance. Such recurrent ejections could be due to periodic energy storage
and periodic reorganisation of magnetic field as envisaged to occur
for flares, but at lower energy levels.

---------------------------------------------------------
Title: Dynamics of a surge observed in the C IV and H alpha lines
Authors: Schmieder, B.; Mein, P.; Vial, J. -C.; Tandberg-Hanssen, E.
1983A&A...127..337S Altcode:
Time sequences of a surge have been obtained in Active Region 2701
during a coordinated SMY program, on October 2nd, 1980, while the MSDP
spectrograph operated in H-alpha at the Meudon Solar Tower and the UVSP
spectrometer on SMM observed in the 1548 A C IV resonance line. The cold
(H-alpha) and hot (C IV) material follow the same channel, and the event
lasts about 10 min in both lines. A good correlation is found between
H-alpha and C IV velocities; radial velocities along the surge are in
the range 40-60 km/s in both cases. The observations are consistent
with the hypothesis that a pressure gradient drives the surge. The
H-alpha data seem to indicate the presence of a shock wave in the
chromosphere, while the C IV quantities (velocities, accelerations)
vary on a very short time scale. Their maxima occur at some locations
which could be interpreted as 'pinched' zones.

---------------------------------------------------------
Title: Dynamics of solar filaments. II - Mass motions in an active
region filament from H-alpha center to limb observations
Authors: Malherbe, J. M.; Schmieder, B.; Ribes, E.; Mein, P.
1983A&A...119..197M Altcode:
The authors present the observations of a solar filament obtained at
Meudon with the Hα spectroheliograph over a period of 10 d. They show
a morphologically stable feature. The authors perform a statistical
analysis of the radial velocity field. Assuming long-lived (several
days) stationary motions, they compute a 3-dimensional velocity field
from center to limb observations of the radial component of velocity
in the stable feature. Different pictures of stationary material
circulations are suggested and compared with theoretical models of
filaments. On the contrary, in the case of short-lived (a few 10
min) flows of material, the authors interpret their data in terms
of velocity loops in the magnetic structure supporting the filament,
and they compare the results with the MHD model proposed by Ribes and
Unno (1980). Possible improvements to this model are pointed out in
the conclusion.

---------------------------------------------------------
Title: Dynamics of the eruptive prominence of 6 May 1980 and its
relationship to the coronal transient
Authors: Mein, N.; Schmieder, B.; Simon, G.; Tandberg-Hanssen, E.;
Wu, S. T.
1982A&A...114..192M Altcode:
The active prominence of the 6 May 1980 has been observed between 5.23
and 10.22 UT with the Ultraviolet Spectrometer and Polarimeter (UVSP)
on board the Solar Maximum Mission (SMM) satellite. Intensities of
1548 A line of CIV and dopplershifts have been derived. A motion of
the magnetic tube maintaining the prominence material is noted. This
motion is followed by a coronal transient observed with the Coronagraph
and Polarimeter (C/P) between 11 and 13 UT. It is suggested that the
event is related to a MHD wave induced by a flare occurring behind
the solar disk, and a MHD modeling of the perturbation is proposed.

---------------------------------------------------------
Title: Preflare heating of filaments
Authors: Malherbe, J. M.; Simon, G.; Mein, P.; Mein, N.; Schmieder,
B.; Vial, J. C.
1982AdSpR...2k..53M Altcode: 1982AdSpR...2...53M
Disappearances of preflare filaments have been observed on June 22,
1980 (S07,W13) (flare at 13.04 U.T.) and September 3, 1980 (flare
at 7.52 U.T.). The analysis of MSDP data (MEUDON) leads to the
followings conclusions : - Disappearances begin a few minutes before
the Hα impulsive phase. - The filaments can be seen again after the
flares. - Upwards motions occur in several points, without disturbing
significantly preëxisting downflows. Velocity maps suggest shears
or velocity loops. The filament disappearance seems to be due to
a heating mechanism beginning before the flare maximum.

---------------------------------------------------------
Title: A surge obsrved in Hα and CIV
Authors: Schmieder, B.; Mein, P.; Vial, J. C.; Tandberg-Hanssen, E.
1982AdSpR...2k.225S Altcode: 1982AdSpR...2..225S
Simultaneous Hα (MSDP at Meudon) and C IV (UVSP aboard SMM)
measurements of Active Region 2701 were made on October 2,
1980. Isodensity and velocity maps were derived for both lines
and superposed. A good correlation was found between Hα and C IV
velocities. A surge was observed for 10 minutes. The base was located
in a bright point in CIV and Hα, and escaping matter followed the same
channel (“absorbing” in Hα, “emitting” in C IV). The velocity
along the surge was about 80 kms.-1 in Hα and 100 km s-1 in C IV. A
loop appeared in C IV. We discuss the existing models and conclude
that the vertical pressure gradient was capable of driving the surge.

---------------------------------------------------------
Title: Mass motions in a quiescent filament
Authors: Malherbe, J. M.; Mein, P.; Schmieder, B.
1982AdSpR...2k..57M Altcode: 1982AdSpR...2R..57M
The “disparition brusque” (DB) of a filament (N20, E35) has been
observed above an active region with the Multichannel Subtractive
Double Pass (MSDP) spectrograph operating on the Meudon Solar Tower,
from 10h45 UT to 13h30 UT on June 22, 1981. Velocity fields and
intensity fluctuations are measured in the Hα line. The DB doesn't
take place simultaneously in all parts of the filament : thin threads
(thickness &lt;3 arc seconds) with upward radial velocities reaching
about 50 km/s are successively observed inside the prominence from S
to N regions. These motions correspond likely to the rise of material
along magnetic loops closely related to the prominence structure. The
dynamics inside such a magnetic loop is investigated : a high speed flow
(supersonic, likely superalfvénic) strongly accelerated is evidenced
and a deformation of the flux tube, probably due to the centrifugal
forces exerted by the flow on the magnetic lines, is suggested. These results are compared with some theoretical works on dynamics
inside magnetic loops, especially to siphon flow models. However,
as in the case of the prominence support problem, better theoretical
models are still needed.

---------------------------------------------------------
Title: About the onsets of closely-consecutive homologous flares
Authors: Martres, M. J.; Mein, N.; Mein, P.; Mouradian, Z.; Rayrole,
J.; Schmieder, B.; Simon, G.; Soru-Escaut, I.; Woodgate, B.; Strong, K.
1982AdSpR...2k.109M Altcode: 1982AdSpR...2R.109M
The onsets of closely consecutive homologous flares (CCHF), which
are separated by less than 6 hours and most often by about 1 hour,
are compared with that of isolated flares (no flare in the region half
a day before). Isolated flares appear to be formed of two components,
a surging arch and a flaring arch, while a set of CCHF may be composed
of consecutive elementary flares or of a series of complex ones. It
is shown that the onset of eruptive flare phenomena is not the same
for an isolated event and for a member of CCHF (excluding the first)
as found in H-alpha and EUV observations, and probably in X-ray
observations also. It is suggested that a CCHF set would become a
single flare with episodic enhancement of brightness by taking account
of the common H-alpha behavior of surging and flaring arches as well
as the EUV emission.

---------------------------------------------------------
Title: Dynamics in the filaments. I - Oscillations in a quiescent
filament
Authors: Malherbe, J. M.; Schmieder, B.; Mein, P.
1981A&A...102..124M Altcode:
A quiescent filament is observed by the 9 channel MSDP spectrograph
operating on the Meudon Observatory tower during 720 s with a 30 s
time step. The field view of 6 x 1 arcmin permits the study of the
dynamics of 50 oscillation cells which increases the freedom degree
comparatively to the one slit spectrograph techniques. A Fourier
analysis of the radial velocity measured in the H-alpha line shows
that the steady velocities are upward in the filament, while the
chromospheric oscillations are almost undetectable inside the filament.

---------------------------------------------------------
Title: Mechanical flux in the solar chromosphere. III - Variation
of the mechanical flux
Authors: Mein, N.; Schmieder, B.
1981A&A....97..310M Altcode:
The mechanical flux in the photosphere and the chromosphere is inferred
from observations of atmospheric oscillations made over a large range
of periods (60s-400s). Observations of Doppler shifts in Ca II and Mg
I lines are related to velocities by means of heights of formation and
modulation transfer functions deduced from weighting functions. The
flux is derived from estimates of the amplitude and phase of the
velocity at different heights in the atmosphere. The results imply
that the energy dissipated by waves in a plane-parallel atmospheric
model is insufficient to balance the radiative losses. The short-fall
can reach a factor 100 in the high chromosphere. Heating of the corona
by shock wave dissipation is inconsistent with our results.

---------------------------------------------------------
Title: Structure and Evolution of Velocities in Quiescent Filaments
Authors: Martres, M. -J.; Mein, P.; Schmieder, B.; Soru-Escaut, I.
1981SoPh...69..301M Altcode:
Simultaneous observations of radial velocities in a `quiescent'
prominence seen in Hα on the disk and in the underlaying photosphere
have been obtained in the Meudon Observatory: Doppler shifts in
photospheric lines are weaker than in the surrounding regions (&lt;0.3
km s-1); the scale of velocity structures is smaller
(&lt;104 km). The vertical component of velocities cannot
be neglected. Hα Doppler shifts show that: (a) Highest velocities
are often correlated with high brightness horizontal gradients,
which suggests that filament and surrounding bright regions belong
to the same geometrical and dynamical structure. (b) Fast motions
(7 km s-1) have short life-times (a few minutes). (c) Slow
motions in dark regions (&lt;3 km s-1) are associated with
blue shifts and may last several hours. This behaviour was confirmed
in many other cases by filament observations with the 3-wavelength Hα
patrol. This is consistent with EUV observations of the transition zone
around prominences, but disagrees with `downward motions' as seen at
the limb, unless these motions do not refer to material velocities.

---------------------------------------------------------
Title: Mechanical flux in the solar chromosphere. II - Determination
of the mechanical flux
Authors: Schmieder, B.; Mein, N.
1980A&A....84...99S Altcode:
The observations of two lines of Ca II (8542-8498) made with the
Sacramento Peak Tower and formation altitudes values Z(omega) for these
two lines determined by weighting functions are used to evaluate, for
each frequency omega, the mechanical flux F(omega) corresponding to
the altitude Z(omega). Corrections taking into account the weakening
of waves of wavelengths smaller than the line formation layer were
applied to the flux. The corrected flux does not show a significant
increase with the frequency (up to 10 mHz), which seems to indicate
that nonthermal microturbulence does not correspond necessarily to
progressive wave. The mechanical flux integrated over the frequency
range 0-10 mHz reaches at the most 2000 erg/sq cm s in the middle
chromosphere (1100 km). This is not sufficient to balance the energy
losses of the transition zone and the corona.

---------------------------------------------------------
Title: Motions and Oscillations in Filaments
Authors: Malherbe, J. M.; Martres, M. J.; Mein, P.; Schmieder, B.;
Soru-Escaut, I.
1980jfss.conf..166M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Observational Proof of the Inefficiency of the Chromospheric
Heating by Acoustic Waves
Authors: Mein, P.; Mein, N.; Schmieder, B.
1980jfss.conf...70M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Waves in the low solar chromosphere.
Authors: Schmieder, B.
1979A&A....74..273S Altcode:
Observations of the Mg I line at 5172.7 A made with the Sacramento
Peak Solar Tower have been analyzed statistically. The phase
shifts between dopplershifts and between intensity and dopplershift
fluctuations measured at different points in the Mg I line profile
have been interpreted by wave theory, after a discussion of the
formation altitudes of dopplershifts. Radiative dissipation seems to be
efficient up to an altitude of 600 km, in the evanescent wave range (3-5
mHz). Some energy can be transported, but in the acoustic wave range
(5-8 mHz), energy propagation is not detected. The observations in that
frequency range are explained by the simultaneous presence of upward
propagating waves and waves reflected in the high chromosphere. The
presence of pure downward propagating waves around the temperature
minimum can be anticipated.

---------------------------------------------------------
Title: Linear hydrodynamical equations coupled with radiative
transfer in a non-isothermal atmosphere. II: Application to solar
photospheric observations.
Authors: Schmieder, B.
1978SoPh...57..245S Altcode:
In a previous paper (Schmieder, 1977), we solved simultaneously the
hydrodynamical and radiative transfer equations, so we do not have to
assume any relaxation time of the atmosphere. In this paper, we use
that theory to interpret photospheric observations of the Mg I line
at 5172 Å.

---------------------------------------------------------
Title: Linear hydrodynamical equations coupled with radiative transfer
in a non-isothermal atmosphere. I. Method.
Authors: Schmieder, B.
1977SoPh...54..269S Altcode:
A method coupling the hydrodynamical equations and radiative transfer
in a realistic solar model atmosphere is described. The influence of
the temperature gradient of the model and the radiative dissipation
is pointed out.

---------------------------------------------------------
Title: Wave propagation in the photosphere.
Authors: Schmieder, B.
1976SoPh...47..435S Altcode:
Using a 32 minutes sequence of observation, brightness and velocity
fluctuations in the wings of the MgI line at 5172.7 Å and Fe II line
at 5197.578 Å are analysed. The analysis of phase shifts and amplitude
ratios leads to the following conclusions:

---------------------------------------------------------
Title: Interpretation of photospheric observations by wave theory
Authors: Schmieder, B.
1976pmas.conf..275S Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Fluctuations of Temperature and Density in the Photosphere
Authors: Schmieder, B.
1972A&A....16...44S Altcode:
The first part of this paper deals with the theoretical calculations
of the intensities of two lines of Fe 1 (5196.067 A and 5195.482 A),
as well as these of a point in the wing of the line b1 of Mg 1 and
of the neighbouring continuum in a perturbed atmosphere. We point
out that the intensities of the Fe 1 lines are very sensitive to
temperature fluctuations whereas the intensity of the continuum is
mainly sensitive to density fluctuations. In the second part, the
study of the fluctuations of the mesured relative intensities allows
us to determine the r.m.s. of the temperature and density fluctuations
at two altitudes. We try to evaluate the contribution of respectively
the oscfflatory phenomenon and the granulation. In the third part, we
introduce the fluctuations associated to the granulation in a solar
atmosphere modeL In this way, we obtain perturbed models which give
variations of the relative brightness fluctuations across the solar
disk. The average value of these variations is in good agreement
with the results of Edmonds (1962) for &gt; 0.5. Considering the
fluctuations associated with the oscfflatory phenomenon, we determine a
radiative minimum relaxation time of about 80s. Key words: photosphere
- fluctuations of temperature and of density in the solar photosphere
- fine structure - perturbed models in the photosphere - radiative
relaxation time in the photosphere La partie est consacree l'e'tude
des de deux rajes de Fe 1 (5196,067 A et 5195,482 A), de celle d'un
point dans l'aile de la raie b1 de Mg I et de celle du continu voisin
dans une atmosphire perturb . Nous montrons que lee des raies du
fer sont sensibles aux fluctuations de temp6rature et que par contre
celle du continu l'est surtout aux fluctuations de densi . Utilisant
ces resultats , nous avons fait des observations la Tour Solaire
de Meudon dans ce domaine de longueur d'onde. Dans une partie, I'
ude des fluctuations des intensite's relatives mesuree's nous permet
de les carts quadratiques moyens des fluctuations de la et de la
densit6 pour deux altitudes. Une tentative est faite pour connattre
la contribution relative du oscfflatoire et de la granulation dans
ces fluctuations. Dans la partie nous introduisons les fluctuations
associ6es a' la granulation dans un d' . Nous obtenons des perturbe's
qui donnent des variations centre-bord de fluctuations de brillance
relative. La moyenne de ces variations est en bon accord avec les
mesures d'Edmonds (1962) pour &gt; 0.5. En les fluctuations au 'ne
oscfflatoire, nous d6terminons un temps de relaxation minimum de
l'ordre de 80s.

---------------------------------------------------------
Title: Sur le Temps de Relaxation des Perturbations en Température
dans la Photosphère
Authors: Schmieder, B.
1969CRASB.269..935S Altcode:
No abstract at ADS