malherbe

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Author name code: malherbe
ADS astronomy entries on 2022-09-14
author:"Malherbe, Jean-Marie"

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Title: The SLED project and the dynamics of coronal flux ropes
Authors: Malherbe, Jean-Marie; Mein, Pierre; Sayède, Frédéric;
Rudawy, Pawel; Phillips, Kenneth; Keenan, Francis; Rybák, Jan
2022AdSpR..70.1562M Altcode:
Investigations of the dynamics of the hot coronal plasma are crucial
for understanding various space weather phenomena and making in-depth
analyzes of the global heating of the solar corona. We present here
numerical simulations of observations of siphon flows along loops
(simple semi-circular flux ropes) to demonstrate the capabilities of
the Solar Line Emission Dopplerometer (SLED), a new instrument under
construction for imaging spectroscopy. It is based on the Multi-channel
Subtractive Double Pass (MSDP) technique, which combines the advantages
of filters and slit spectrographs. SLED will observe coronal structures
in the forbidden lines of FeX 6374 Å and FeXIV 5303 Å, and will
measure Doppler shifts up to 150 km s-1 at high precision
(50 m s-1) and cadence (1 Hz). It is optimized for studies
of the dynamics of fast evolving events such as flares or Coronal
Mass Ejections (CMEs), as well as for the detection of high-frequency
waves. Observations will be performed with the coronagraph at Lomnický
Štít Observatory (LSO), and will also occur during total solar
eclipses as SLED is a portable instrument.

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Title: Jules Janssen, the birth of solar physics, the foundation of
Meudon Observatory, and the Mont Blanc adventure (1875-1895)
Authors: Malherbe, J. -M.
2022JAHH...25..187M Altcode:
Jules Janssen is a well known astronomer. In 1868 he introduced
the spectroscopic technique to observe solar prominences. He also
invented innovative methods in imagery and photography. This paper
focuses on the period from the foundation of Meudon Observatory,
associated with the birth of astrophysics and solar physics in France,
to the Mont Blanc saga, with the creation of the observatory and the
three scientific ascents by Janssen to the top of the mountain. As
most documents are written in French, this fantastic and unbelievable
adventure at the end of the nineteenth century, deserves to be told in
English, and it reveals the long-term vision of Janssen's astronomy. It
involved specialized instruments, located in well-chosen places where
atmospheric interference was minimized. High altitude observations,
from Mont Blanc (or from balloons, also experienced by Janssen),
prefigure space astronomy which developed

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Title: Monitoring fast solar chromospheric activity: the MeteoSpace
project
Authors: Malherbe, Jean-Marie; Corbard, Thierry; Barbary, Gaële;
Morand, Frédéric; Collin, Claude; Crussaire, Daniel; Guitton,
Florence
2022ExA....53.1127M Altcode: 2022ExA...tmp...33M
We present in this reference paper an instrumental project dedicated to
the monitoring of solar activity during solar cycle 25. It concerns the
survey of fast evolving chromospheric events implied in Space Weather,
such as flares, coronal mass ejections, filament instabilities and
Moreton waves. Coronal waves are produced by large flares around
the solar maximum and propagate with chromospheric counterparts;
they are rare, faint, difficult to observe, and for that reason,
challenging. They require systematic observations with automatic, fast
and multi-channel optical instruments. MeteoSpace is a high cadence
telescope assembly specially designed for that purpose. The large amount
of data will be freely available to the solar community. We describe
in details the optical design, the qualification tests and capabilities
of the telescopes, and show how waves can be detected. MeteoSpace will
be installed at Calern observatory (Côte d'Azur, 1270 m) and will be
in full operation in 2023.

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Title: The Solar Line Emission Dopplerometer project
Authors: Malherbe, Jean-Marie; Mein, Pierre; Sayède, Frédéric;
Rudawy, Pawel; Phillips, Kenneth; Keenan, Francis; Rybák, Jan
2022ExA....53...83M Altcode: 2021ExA...tmp..125M; 2021arXiv211001645M
Observations of the dynamics of solar coronal structures are necessary
to investigate space weather phenomena and global heating of the
corona. The profiles of high temperature lines emitted by the hot plasma
are usually integrated by narrow band filters or recorded by classical
spectroscopy. We present in this paper details of a new transportable
instrument (under construction) for imaging spectroscopy: the Solar Line
Emission Dopplerometer (SLED). It uses the Multi-channel Subtractive
Double Pass (MSDP) technique, which combines the advantages of both
filters and narrow slit spectrographs, i.e. high temporal, spatial and
spectral resolutions. The SLED will measure at high cadence (1 Hz)
the line-of-sight velocities (Doppler shifts) of hot coronal loops,
in the forbidden lines of FeX 6374 Å and FeXIV 5303 Å. It will
follow the dynamics of fast evolving events of solar activity such
as flares or Coronal Mass Ejections (CMEs), and also study coronal
heating by short period waves. Observations will be performed with
the coronagraph at the Lomnický Štít Observatory (LSO, in Slovakia)
or during total eclipses. The SLED will also observe the dynamics of
solar prominences in Hα 6563 Å or He D3 5876 Å lines when mounted
on the Białków coronagraph (near Wrocław, Poland). It is fully
compatible with polarimetric measurements by various techniques.

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Title: Five decades of solar research at the Pic du Midi Turret-Dome
(1960-2010). Part 2: High spatial resolution imagery
Authors: Muller, R.; Roudier, Th.; Malherbe, J. -M.
2021JAHH...24..921M Altcode:
In the Part 2 of the series of two papers dedicated to the review on
fifty years of advances in solar instrumentation and solar physics
made at the Pic du Midi Turret-Dome (1960-2010) in various domains, we
pre-sent the main observations and results obtained in the field of high
resolution imagery, for which the instrument was originally designed.

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Title: Reconstructing solar irradiance from historical Ca II K
observations. I. Method and its validation
Authors: Chatzistergos, Theodosios; Krivova, Natalie A.; Ermolli,
Ilaria; Yeo, Kok Leng; Mandal, Sudip; Solanki, Sami K.; Kopp, Greg;
Malherbe, Jean-Marie
2021A&A...656A.104C Altcode: 2021arXiv210905844C
Context. Knowledge of solar irradiance variability is critical to
Earth's climate models and understanding the solar influence on Earth's
climate. Direct solar irradiance measurements have only been available
since 1978. Reconstructions of past variability typically rely on
sunspot data. However, sunspot records provide only indirect information
on the facular and network regions, which are decisive contributors to
irradiance variability on timescales of the solar cycle and longer. Aims: Our ultimate goal is to reconstruct past solar irradiance
variations using historical full-disc Ca II K observations to describe
the facular contribution independently of sunspot observations. Here,
we develop the method and test it extensively by using modern CCD-based
(charge-coupled device) Ca II K observations. We also carry out initial
tests on two photographic archives. Methods: We employ carefully
reduced and calibrated Ca II K images from 13 datasets, including some
of the most prominent series, such as those from the Meudon, Mt Wilson,
and Rome observatories. We convert them to unsigned magnetic field
maps and then use them as input to the adapted Spectral and Total
Irradiance Reconstruction (SATIRE) model to reconstruct total solar
irradiance (TSI) variations over the period 1978-2019, for which
direct irradiance measurements are available. Results: The
reconstructed irradiance from the analysed Ca II K archives agrees well
with direct irradiance measurements and existing reconstructions. The
model also returns good results on data taken with different bandpasses
and images with low spatial resolution. Historical Ca II K archives
suffer from numerous inconsistencies, but we show that these archives
can still be used to reconstruct TSI with reasonable accuracy provided
the observations are accurately processed and the effects of changes
in instrumentation and instrumental parameters are identified and
accounted for. The reconstructions are relatively insensitive to the
TSI reference record used to fix the single free parameter of the
model. Furthermore, even employment of a series, itself reconstructed
from Ca II K data, as a reference for further reconstructions returns
nearly equally accurate results. This will enable the Ca II K archives
without an overlap with direct irradiance measurements to be used to
reconstruct past irradiance. Conclusions: By using the unsigned
magnetic maps of the Sun reconstructed from modern high-quality Ca
II K observations as input into the SATIRE model, we can reconstruct
solar irradiance variations nearly as accurately as from directly
recorded magnetograms. Historical Ca II K observations can also be
used for past irradiance reconstructions but need additional care,
for example identifying and accounting for discontinuities and changes
in the quality of the data with time.

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Title: Five decades of solar research at the Mic du Midi Turret-Dome
(1960-2010). Part 1: Overview of instrumentation and observations
Authors: Roudier, Th.; Malherbe, J. -M.; Rozelot, J. -P.; Mein, P.;
Muller, R.
2021JAHH...24..585R Altcode:
The Pic du Midi Turret-Dome, known as 'Lunette Jean Rösch'or LJR
('lunette' for refractor in French), was scientifically active
during five decades between 1960 and 2010. It was dedicated to high
spatial resolution observations in solar astronomy. We review fifty
years of advances in solar instrumentation and solar physics made
by this instrument in various domains, which took advantage of the
good seeing at Pic du Midi. First, we summarize some of the LJR
results in broad-band and wide-field imagery of the photosphere;
as this topic was the initial goal and has been the most important
contribution of the refractor, details will be provided in Part
2. Then, we present spectro-polarimetric instrumentation and
observations with narrow slit and imaging spectroscopy of the
photosphere and the chromosphere. The Turret-Dome also housed an
original spectro-coronagraph, and observations of the high temperature
coronal plasma are highlighted. Finally, we describe progress in the
determination of the solar shape with the heliometer. The LJR remained
active until the launch of the Hinode and Solar Dynamics Observatory
satellites (in 2006 and 2010, respectively).

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Title: Changes in granulation scales over the solar cycle seen with
SDO/HMI and Hinode/SOT
Authors: Ballot, J.; Roudier, T.; Malherbe, J. M.; Frank, Z.
2021A&A...652A.103B Altcode: 2021arXiv210603556B
Context. The Sun is the only star where the superficial turbulent
convection can be observed at very high spatial resolution. The
Solar Dynamics Observatory (SDO) has continuously observed the full
Sun from space with multi-wavelength filters since July 2010. In
particular, the Helioseismic and Magnetic Imager (HMI) instrument
takes high-cadence frames (45 s) of continuum intensity in which
solar granulation is visible. Aims: We aimed to follow the
evolution of the solar granules over an activity cycle and look for
changes in their spatial properties. Methods: We investigated
the density of granules and their mean area derived directly from
the segmentation of deconvolved images from SDO/HMI. To perform the
segmentation, we define granules as convex elements of images. Results: We measured an approximately 2% variation in the density
and the mean area of granules over the cycle, the density of granules
being greater at solar maximum with a smaller granule mean area. The
maximum density appears to be delayed by about one year compared
to classical activity indicators, such as the sunspot number. We
complemented this study with high-spatial-resolution observations
obtained with Hinode/SOTBFI (Solar Optical Telescope Broadband Filter
Imager), which are consistent with our results. Conclusions:
The observed variations in solar granulation at the disc centre reveal
a direct insight into the change in the physical properties that occur
in the upper convective zone during a solar cycle. These variations
can be due to interactions between convection and magnetic fields,
either at the global scale or, locally, at the granulation scale.

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Title: Photospheric downflows observed with SDO/HMI, HINODE, and an
MHD simulation
Authors: Roudier, T.; Švanda, M.; Malherbe, J. M.; Ballot, J.; Korda,
D.; Frank, Z.
2021A&A...647A.178R Altcode: 2021arXiv210303077R
Downflows on the solar surface are suspected to play a major role in
the dynamics of the convection zone, at least in its outer part. We
investigate the existence of the long-lasting downflows whose effects
influence the interior of the Sun but also the outer layers. We study
the sets of Dopplergrams and magnetograms observed with Solar Dynamics
Observatory and Hinode spacecrafts and an magnetohydrodynamic (MHD)
simulation. All of the aligned sequences, which were corrected from
the satellite motions and tracked with the differential rotation,
were used to detect the long-lasting downflows in the quiet-Sun at
the disc centre. To learn about the structure of the flows below the
solar surface, the time-distance local helioseismology was used. The
inspection of the 3D data cube (x, y, t) of the 24 h Doppler sequence
allowed us to detect 13 persistent downflows. Their lifetimes lie in
the range between 3.5 and 20 h with a sizes between 2″ and 3″ and
speeds between −0.25 and −0.72 km s−1. These persistent
downflows are always filled with the magnetic field with an amplitude of
up to 600 Gauss. The helioseismic inversion allows us to describe the
persistent downflows and compare them to the other (non-persistent)
downflows in the field of view. The persistent downflows seem to
penetrate much deeper and, in the case of a well-formed vortex, the
vorticity keeps its integrity to the depth of about 5 Mm. In the MHD
simulation, only sub-arcsecond downflows are detected with no evidence
of a vortex comparable in size to observations at the surface of the
Sun. The long temporal sequences from the space-borne allows us to show
the existence of long-persistent downflows together with the magnetic
field. They penetrate inside the Sun but are also connected with the
anchoring of coronal loops in the photosphere, indicating a link between
downflows and the coronal activity. A links suggests that EUV cyclones
over the quiet Sun could be an effective way to heat the corona.

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Title: Four Decades of Advances from MSDP to S4I and SLED Imaging
Spectrometers
Authors: Mein, P.; Malherbe, J. -M.; Sayède, F.; Rudawy, P.; Phillips,
K. J. H.; Keenan, F. P.
2021SoPh..296...30M Altcode: 2021arXiv210103918M
The Multichannel Subtractive Double Pass (MSDP) is an imaging
spectroscopy technique, which allows observations of spectral line
profiles over a 2D field of view with high spatial and temporal
resolution. It has been intensively used since 1977 on various
spectrographs (Meudon, Pic du Midi, the German Vacuum Tower Telescope,
THEMIS, Wrocław). We summarize previous developments and describe
the capabilities of a new design that has been developed at Meudon
and that has higher spectral resolution and increased channel number:
Spectral Sampling with Slicer for Solar Instrumentation (S4I), which
can be combined with a new and fast polarimetry analysis. This new
generation MSDP technique is well adapted to large telescopes. Also
presented are the goals of a derived compact version of the instrument,
the Solar Line Emission Dopplerometer (SLED), dedicated to dynamic
studies of coronal loops observed in the forbidden iron lines,
and prominences. It is designed for observing total solar eclipses,
and for deployment on the Wrocław and Lomnicky peak coronagraphs
respectively for prominence and coronal observations.

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Title: Evolution of exploding granules from coordinated observations
by THEMIS, IRIS, SDO/HMI, and HINODE, and a simulation
Authors: Roudier, T.; Malherbe, J. M.; Gelly, B.; Douet, R.; Frank,
Z.; Dalmasse, K.
2020A&A...641A..50R Altcode: 2020arXiv200712438R
Exploding granules constitute the strongest horizontal flows on the
quiet Sun and contribute to the structure of the surface horizontal
velocity fields which build the large-scale organization of the discrete
magnetic field. In this work we explore exploding granule expansion
through the observations of the ground-based THEMIS telescope, IRIS,
SDO, and the Hinode space-borne instruments, and finally with the
magnetohydrodynamics simulation. We evaluate the detection and the
expansion of exploding granules at several wavelengths and at various
spatial and temporal resolutions. To analyze the different temporal
sequences, two methods of image segmentation are applied to select
the granules. The first allows us to follow individually the exploding
granules observed simultaneously by THEMIS, IRIS, and SDO. The second
uses long time independent sequences from THEMIS, IRIS, SDO, Hinode,
and a simulation. In the first method (called manual) the segmentation
isolates the cell of the granules (bright granules and intergranular
parts), while in the second method (called statistical) only the
bright part of the granules are isolated. The results obtained with
simultaneous or distinct temporal observations using the two methods
of segmentation are in good agreement. The granule area evolves
linearly with an expansion velocity that decreases with the radius. A
rapid decrease in the velocity expansion in the first two minutes is
observed. The detection and measurement of the dynamics of the explosive
granules can be performed from ground- and space-based instruments. Our
work reveals the usefulness of SDO data, with low spatial resolution, to
study the dynamics of the exploding granules all over the solar surface.

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Title: Major Volcanic Eruptions and Their Impacts on Southern
Hemisphere Temperatures During the Late 19th and 20th Centuries,
as Simulated by CMIP5 Models
Authors: Harvey, P. J.; Grab, S. W.; Malherbe, J.
2020GeoRL..4787792H Altcode:
While much is known about the impacts of volcanic forcing on Northern
Hemisphere (NH) climates, knowledge about Southern Hemisphere (SH)
responses is still in its infancy. We examine volcanic impacts on SH
temperatures following eight major late 19th and 20th century eruptions
(Agung, 1963; Colima, 1913; El Chichón, 1982; Pinatubo, 1991; Krakatau,
1883; Quizapu, 1932; Santa Maria, 1902; Tarawera, 1886). Coupled Model
Intercomparison Project, Phase 5 (CMIP5) historical simulations are used
to analyze near-surface land temperatures. We demonstrate that four of
the eight major eruptions (Krakatau, Santa Maria, Agung, and Pinatubo)
significantly lowered mean SH temperatures; these tropical eruptions
emitted at least 20 Tg of SO2 into the stratosphere. SH
responses typically lagged NH temperature cooling responses by 1-2
months, excluding Pinatubo. Responses differ spatially and temporally
with each eruption, highlighting the importance of investigating events
individually. Overall, we observe relatively strong (between -0.19°C
and -0.36°C) austral autumn/winter SH cooling.

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Title: Analysis of full-disc Ca II K spectroheliograms. III. Plage
area composite series covering 1892-2019
Authors: Chatzistergos, Theodosios; Ermolli, Ilaria; Krivova,
Natalie A.; Solanki, Sami K.; Banerjee, Dipankar; Barata, Teresa;
Belik, Marcel; Gafeira, Ricardo; Garcia, Adriana; Hanaoka, Yoichiro;
Hegde, Manjunath; Klimeš, Jan; Korokhin, Viktor V.; Lourenço, Ana;
Malherbe, Jean-Marie; Marchenko, Gennady P.; Peixinho, Nuno; Sakurai,
Takashi; Tlatov, Andrey G.
2020A&A...639A..88C Altcode: 2020arXiv200501435C
Context. Studies of long-term solar activity and variability require
knowledge of the past evolution of the solar surface magnetism. The
archives of full-disc Ca II K observations that have been performed
more or less regularly at various sites since 1892 can serve as an
important source of such information. Aims: We derive the plage
area evolution over the last 12 solar cycles by employing data from all
Ca II K archives that are publicly available in digital form, including
several as-yet-unexplored Ca II K archives. Methods: We analysed
more than 290 000 full-disc Ca II K observations from 43 datasets
spanning the period between 1892-2019. All images were consistently
processed with an automatic procedure that performs the photometric
calibration (if needed) and the limb-darkening compensation. The
processing also accounts for artefacts affecting many of the images,
including some very specific artefacts, such as bright arcs found
in Kyoto and Yerkes data. Our employed methods have previously been
tested and evaluated on synthetic data and found to be more accurate
than other methods used in the literature to treat a subset of the data
analysed here. Results: We produced a plage area time-series
from each analysed dataset. We found that the differences between the
plage areas derived from individual archives are mainly due to the
differences in the central wavelength and the bandpass used to acquire
the data at the various sites. We empirically cross-calibrated and
combined the results obtained from each dataset to produce a composite
series of plage areas. The 'backbone' approach was used to bridge
the series together. We have also shown that the selection of the
backbone series has little effect on the final composite of the plage
area. We quantified the uncertainty of determining the plage areas
with our processing due to shifts in the central wavelength and found
it to be less than 0.01 in fraction of the solar disc for the average
conditions found on historical data. We also found the variable seeing
conditions during the observations to slightly increase the plage
areas during the activity maxima. Conclusions: We provide the
most complete so far time series of plage areas based on corrected
and calibrated historical and modern Ca II K images. Consistent
plage areas are now available on 88% of all days from 1892 onwards
and on 98% from 1907 onwards. The whole series described in
the paper 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/cat/J/A+A/639/A88">http://cdsarc.u-strasbg.fr/viz-bin/cat/J/A+A/639/A88</A>

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Title: Optical instrumentation for chromospheric monitoring during
solar cycle 25 at Paris and Côte d'Azur observatories
Authors: Malherbe, Jean-Marie; Corbard, Thierry; Dalmasse, Kevin
2020JSWSC..10...31M Altcode:
We present the observing program proposed by Paris and Côte
d'Azur Observatories for monitoring solar activity during the
upcoming cycle 25 and providing near real time images and movies of
the chromosphere for space-weather research and applications. Two
optical instruments are fully dedicated to this task and we summarize
their capabilities. Short-term and fast-cadence observations of the
chromosphere will be performed automatically at Calern observatory
(Côte d'Azur), where dynamic events, as flare development, Moreton
waves, filament instabilities and Coronal Mass Ejections onset, will
be tracked. This new set of telescopes will operate in 2021 with
narrow bandpass filters selecting Hα and CaII K lines. We present
the instrumental design and a simulation of future images. At Meudon,
the Spectroheliograph is well adapted to the long-term and low-cadence
survey of chromospheric activity by recently improved and optimized
spectroscopic means. Surface scans deliver daily (x, y, λ) datacubes
of Hα, CaII K and CaII H line profiles. We describe the nature of
available data and emphasize the new calibration method of spectra.

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Title: VizieR Online Data Catalog: Plage area composite series
(Chatzistergos+, 2020)
Authors: Chatzistergos, T.; Ermolli, I.; Krivova, N. A.; Solanki,
S. K.; Banerjee, D.; Barata, T.; Belik, M.; Gafeira, R.; Garcia,
A.; Hanaoka, Y.; Hegde, M.; Klimes, J.; Korokhin, V. V.; Lourenco,
A.; Malherbe, J. -M.; Marchenko, G. P.; Peixinho, N.; Sakurai, T.;
Tlatov, A. G.
2020yCat..36390088C Altcode:
Annual, monthly, and daily values of the plage area composite series. The archives included are those from the Arcetri (Ar), Baikal (Ba),
Brussels (Br), Calern (CL), Catania (CT), Coimbra (Co), Kanzelhoehe
(Ka), Kenwood (Ke), Kharkiv (Kh), Kislovodsk (Ki), Kodaikanal taken with
the spectroheliograph (Ko), Kodaikanal taken with the Twin telescope
(KT), Kodaikanal taken with the White-Light Active Region Monitor (WARM)
telescope (KW), Kyoto (Ky), Manila (Ma), Mauna Loa (ML) taken with the
Precision Solar Photometric Telescope (PSPT), McMath-Hulbert (MM), Mees
(MS), Meudon taken with the spectroheliograph (MD1), Meudon taken with
an interference filter (MD2), Mitaka taken with the spectroheliograph
(Mi1), Mitaka taken with the Solar Flare Telescope with an interference
filter (Mi2), Mt Wilson (MW), Pic du Midi (PM), SOlar Diameter Imager
and Surface Mapper (SODISM) telescope on board the PICARD spacecraft
(PS), Rome taken with the equatorial bar at Monte Mario (Ro), Rome taken
with the PSPT (RP1), Rome taken with the PSPT with narrow bandwidth
(RP2), Sacramento Peak (SP), San Fernando taken with the Cartesian
Full-Disk Telescope (CFDT) 1 (SF1), San Fernando taken with the CFDT2
(SF2), Schauinsland (Sc), Teide (Te) taken with the Chromospheric
Telescope (ChroTel), Upice (UP), Valasske Mezirici (VM), Wendelstein
(WS), and Yerkes (YR) sites (3 data files).

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Title: Meteospace, a New Instrument for Solar Survey at the Calern
Observatory
Authors: Malherbe, J. -M.; Corbard, Th; Dalmasse, K.; The Meteospace
team
2020arXiv200102162M Altcode:
High cadence observations of solar activity (active regions, flares,
filaments) in the H$\alpha$ line were performed at Meudon and
Haute Provence Observatories from 1956 to 2004. More than 7 million
images were recorded, mainly on 35 mm films. After a review of the
scientific interest of solar surveys at high temporal resolution
and the historical background, we describe the new instrument which
will operate automatically in 2020 at the Calern station of the Côte
d'Azur observatory (1270 m). It will replace the former heliographs
with improved cadence, seeing and time coverage. We summarize
the capabilities of the optical design and present new scientific
perspectives in terms of flare onset and Moreton wave detection.

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Title: Meteospace, a New Instrument for Solar Survey at the Calern
Observatory
Authors: Malherbe, J. -M.; Corbard, Th.; Dalmasse, K.; Meteospace Team
2019SoPh..294..177M Altcode:
High-cadence observations of solar activity (active regions,
flares, filaments) in the Hα line were performed at Meudon and
Haute Provence Observatories from 1956 to 2004. More than 7 million
images were recorded, mainly on 35 mm films. After a review of the
scientific interest of solar surveys at high temporal resolution
and the historical background, we describe the new instrument which
will operate automatically in 2020 at the Calern station of the Côte
d'Azur observatory (1270 m). It will replace the former heliographs
with improved cadence, seeing and time coverage. We summarize
the capabilities of the optical design and present new scientific
perspectives in terms of flare onset and Moreton wave detection.

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Title: The New 2018 Version of the Meudon Spectroheliograph
Authors: Malherbe, J. -M.; Dalmasse, K.
2019SoPh..294...52M Altcode: 2020arXiv200102638M
Daily full-disk observations of the solar photosphere and chromosphere
started at the Meudon Observatory in 1908. After a review of the
scientific context and the historical background, we describe the
instrumental characteristics and capabilities of the new version
operating since 2018. The major change is the systematic recording
of full line profiles over the entire solar disk providing 3D data
cubes. Spectral and spatial sampling are both improved. Classical 2D
images of the Sun at fixed wavelength are still delivered. We summarize
the different processing levels of on-line data and briefly review
the new scientific perspectives.

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Title: Link between trees of fragmenting granules and deep downflows
in MHD simulation
Authors: Roudier, T.; Malherbe, J. M.; Stein, R. F.; Frank, Z.
2019A&A...622A.112R Altcode: 2019arXiv190103255R
Context. Trees of fragmenting granules (TFG) and associated flows
are suspected to play a major role in the formation of the network in
the quiet Sun. We investigate the counterparts, in terms of dynamics,
of surface structures detectable by high resolution observations in
deeper layers up to 15 Mm, which are only available from numerical
simulations. Aims: The first aim is to demonstrate that TFG
can be evidenced either from surface intensitites, vertical (Vz),
or Doppler (Vdop) velocities. The second is to show that horizontal
flows, which are derived from intensities or Vz/Vdop flows, are in good
agreement, and that this is the case for observations and numerical
simulations. The third objective is to apply this new Vz-based method
to a 3D simulation to probe relationships between horizontal surface
flows, TFG, and deep vertical motions. Methods: The TFG were
detected after oscillation filtering of intensities or Vz/Vdop flows,
using a segmentation and labelling technique. Surface horizontal
flows were derived from local correlation tracking (LCT) and from
intensities or Vz/Vdop flows. These methods were applied to Hinode
observations, 2D surface results of a first simulation, and 3D Vz
data of a second simulation. Results: We find that TFG and
horizontal surface flows (provided by the LCT) can be detected either
from intensities or Vz/Vdop component, for high resolution observations
and numerical simulations. We apply this method to a 3D run providing
the Vz component in depth. This reveals a close relationship between
surface TFG (5 Mm mesoscale) and vertical downflows 5 Mm below the
surface. We suggest that the dynamics of TFG form larger scales
(the 15-20 Mm supergranulation) associated with 15 Mm downflowing
cells below the surface. Conclusions: The TFG and associated
surface flows seem to be essential to understanding the formation
and evolution of the network at the meso and supergranular scale. Movies associated to Figs. 3, 11, 12, and 14 are availabe at <A
href="https://www.aanda.org/10.1051/0004-6361/201834283/olm">https://www.aanda.org</A>

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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: Prototype of S4EI (spectral sampling with slicer for
stellar and extragalactical instrumentation): a new generation 3D
Spectro-imager
Authors: Sayède, F.; Puech, M.; Mein, P.; Galicher, R.; Malherbe,
J. -M.; Amans, J. -P.
2018SPIE10702E..54S Altcode:
S4EI (Spectral Sampling with Slicer for Stellar and Extragalactical
Instrumentation) is a new concept for extending Multichannel
Subtractive Double Pass (ie S4I - Spectral Sampling with Slicer for
Solar Instrumentation) to night-time astronomy. The Multichannel
Subtractive Double Pass (MSDP) spectrographs have been widely
used in solar spectroscopy because of their ability to provide
an excellent compromise between field of view and the spatial and
spectral resolutions. Compared with other spectrographs, MSDP can
deliver simultaneous monochromatic images without any time-scanning
requirements (as the standard Fabry-Perot), with limited loss of
flux. Spatial resolution is the same as for an Imager given by
the telescope: it can be very high. It is based on new generation
reflecting plane image slicers working with large apertures specific
to night-time telescopes. The resulting design could be potentially
very attractive and innovative for different domains of astronomy,
e.g., the simultaneous spatial mapping of accurately flux-calibrated
emission lines between OH sky lines in extragalactic astronomy or the
simultaneous imaging of stars, exoplanets and interstellar medium. The
determination of physical and chemical properties of galaxies needs to
observe several emission lines at different wavelengths. The combination
of these lines gives access to the distribution in dust, star formation
rate, metallicity, the kinematics or even to the electron density of the
gas in the galaxies. The spatial resolution of MSDP allows, like the 3D
or integral field spectrographs the construction of spatial distribution
maps. The advantage of S4EI is that by measuring simultaneously the
different lines, the relative errors of the flux calibration between
the different wavelengths of the lines are potentially limited by
the uncertainty of the calibration source used, which is expected
to significantly reduce the associated errors and thus increase the
precision and accuracy of estimates.

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Title: Large-scale photospheric motions determined from granule
tracking and helioseismology from SDO/HMI data
Authors: Roudier, Th.; Švanda, M.; Ballot, J.; Malherbe, J. M.;
Rieutord, M.
2018A&A...611A..92R Altcode: 2017arXiv171205255R
Context. Large-scale flows in the Sun play an important role in the
dynamo process linked to the solar cycle. The important large-scale
flows are the differential rotation and the meridional circulation
with an amplitude of km s-1 and few m s-1,
respectively. These flows also have a cycle-related components,
namely the torsional oscillations. Aim. Our attempt is to determine
large-scale plasma flows on the solar surface by deriving horizontal
flow velocities using the techniques of solar granule tracking,
dopplergrams, and time-distance helioseismology. Methods:
Coherent structure tracking (CST) and time-distance helioseismology
were used to investigate the solar differential rotation and meridional
circulation at the solar surface on a 30-day HMI/SDO sequence. The
influence of a large sunspot on these large-scale flows with a specific
7-day HMI/SDO sequence has been also studied. Results: The
large-scale flows measured by the CST on the solar surface and the
same flow determined from the same data with the helioseismology in
the first 1 Mm below the surface are in good agreement in amplitude
and direction. The torsional waves are also located at the same
latitudes with amplitude of the same order. We are able to measure
the meridional circulation correctly using the CST method with only
3 days of data and after averaging between ± 15° in longitude. Conclusions: We conclude that the combination of CST and Doppler
velocities allows us to detect properly the differential solar rotation
and also smaller amplitude flows such as the meridional circulation
and torsional waves. The results of our methods are in good agreement
with helioseismic measurements.

---------------------------------------------------------
Title: Dynamics of Trees of Fragmenting Granules in the Quiet Sun:
Hinode/SOT Observations Compared to Numerical Simulation
Authors: Malherbe, J. -M.; Roudier, T.; Stein, R.; Frank, Z.
2018SoPh..293....4M Altcode: 2018arXiv180401870M
We compare horizontal velocities, vertical magnetic fields, and the
evolution of trees of fragmenting granules (TFG, also named families of
granules) derived in the quiet Sun at disk center from observations
at solar minimum and maximum of the Solar Optical Telescope (SOT
on board Hinode) and results of a recent 3D numerical simulation
of the magneto-convection. We used 24-hour sequences of a 2D field
of view (FOV) with high spatial and temporal resolution recorded by
the SOT Broad band Filter Imager (BFI) and Narrow band Filter Imager
(NFI). TFG were evidenced by segmentation and labeling of continuum
intensities. Horizontal velocities were obtained from local correlation
tracking (LCT) of proper motions of granules. Stokes V provided a
proxy of the line-of-sight magnetic field (BLOS). The MHD simulation
(performed independently) produced granulation intensities, velocity,
and magnetic field vectors. We discovered that TFG also form in the
simulation and show that it is able to reproduce the main properties
of solar TFG: lifetime and size, associated horizontal motions, corks,
and diffusive index are close to observations. The largest (but not
numerous) families are related in both cases to the strongest flows
and could play a major role in supergranule and magnetic network
formation. We found that observations do not reveal any significant
variation in TFG between solar minimum and maximum.

---------------------------------------------------------
Title: Dynamics of the photosphere along the solar cycle from SDO/HMI
Authors: Roudier, Th.; Malherbe, J. M.; Mirouh, G. M.
2017A&A...598A..99R Altcode: 2016arXiv161102152R
Context. As the global magnetic field of the Sun has an activity cycle,
one expects to observe some variation of the dynamical properties of
the flows visible in the photosphere. Aims: We investigate the
flow field during the solar cycle by analysing SDO/HMI observations
of continuum intensity, Doppler velocity and longitudinal magnetic
field. Methods: We first picked data at disk center during 6
yr along the solar cycle with a 48-h time step in order to study the
overall evolution of the continuum intensity and magnetic field. Then
we focused on thirty 6-h sequences of quiet regions without any remnant
of magnetic activity separated by 6 months, in summer and winter, when
disk center latitude B0 is close to zero. The horizontal
velocity was derived from the local correlation tracking technique over
a field of view of 216.4 Mm × 216.4 Mm located at disk center. Results: Our measurements at disk center show the stability of
the flow properties between meso- and supergranular scales along the
solar cycle. Conclusions: The network magnetic field, produced
locally at disk center independently from large scale dynamo, together
with continuum contrast, vertical and horizontal flows, seem to remain
constant during the solar cycle.

---------------------------------------------------------
Title: Investigation of the solar centre-to-limb variation of oxygen
and lithium spectral features
Authors: Caffau, E.; Malherbe, J. -M.; Steffen, M.; Ludwig, H. -G.;
Mott, A.
2017MmSAI..88...45C Altcode:
We compare intensity spectra of the Sun observed at different limb
angles in the wavelength range covering the forbidden oxygen lines and
the lithium resonance feature with line formation computations performed
on a CO5BOLD 3D hydrodynamical simulation of the solar atmosphere. Among
the prime oxygen abundance indicators, the forbidden line at 630 nm
is contaminated with a significant Ni I blend. The availability of
observations at different positions on the solar disc allows us to
disentangle the contributions of oxygen and nickel and to derive their
individual abundances. We derived in the past, from the [OI] line,
A(O)=8.73± 0.05 with a nickel abundance of A(Ni)=6.1± 0.04. From
the observations here presented, we obtain A(O)=8.71 and A(Ni)=6.09,
in excellent agreement with the previous result. For lithium, we
investigated the Li doublet at 670.7 nm and compared synthetic spectra
of the Li spectra range based on different line-lists available in the
literature to the observed data. With these observations, we are still
unable to conclude on which is the best line-list to be used for the
blending lines.

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Title: METEOSPACE, solar monitoring and space weather at Calern
observatory
Authors: Corbard, T.; Malherbe, J. -M.; Crussaire, D.; Morand, F.;
Ruty, F.; Biree, L.; Aboudarham, J.; Fuller, N.; Renaud, C.; Meftah, M.
2016sf2a.conf..293C Altcode:
METEOSPACE is a new partnership project between the Paris Observatory
(OP), the Observatoire de la Côte d'Azur (OCA), the French Air
Force and a service company (LUNA technology) for the development
and operation of a set of small telescopes Hα / Ca II K / Ca II H /
G band to be installed at on the Calern plateau (OCA). The objective
is to monitor solar activity for both research and its applications
in space weather through continuous optical observations of the
dynamic phenomena that are visible in the chromosphere: eruptions,
destabilization of the filaments triggering coronal mass ejections
and associated Moreton waves.

---------------------------------------------------------
Title: Investigation of the lithium 670.7 nm wavelength range in
the solar spectrum
Authors: Caffau, Elisabetta; Mott, Alessandro; Harutyunyan, Gohar;
Malherbe, Jean-Marie; Steffen, Matthias
2016cosp...41E.281C Altcode:
Lithium is a key chemical element, with a chemical evolution that is
different from that of most other elements. It is also very fragile,
as it is destroyed by nuclear reactions with protons at temperatures
higher than about 2.5 million K. According to standard Big Bang
nucleosynthesis, only the isotope 7Li is produced in significant
amounts, while the primordial abundance of the lighter isotope 6Li
is negligible. Lithium is not produced by nucleosynthesis in normal
stars, except in peculiar phases of stellar evolution (e.g. in AGB
stars and Novae). Lithium may also be formed as a result of flares in
the atmospheres of young, active stars. To investigate the history
of Li production and depletion in the Galaxy, it is necessary to
analyse stars of all ages, including those at solar metallicity. In
this case, the spectroscopic determination of the Li abundance is
complicated by the presence of other spectral lines overlapping
with the Li doublet at 670.7 nm. The correct identification and
knowledge of the atomic parameters of these blend lines is critical,
especially if the 6LI/7Li isotopic ratio is to be derived. In this
investigation, we consider several line lists of the blending components
available in the literature and use them to compute synthetic spectra,
performing the line formation computations both for the classical 1D
Holweger-Mueller model and a CO5BOLD 3D hydrodynamical simulation of the
solar atmosphere. The synthetic spectra are then compared to the solar
spectrum observed at different limb angles. This allows us to check the
quality of existing line lists, to find potentially misidentified blend
lines, and to construct an optimized line list for solar-type stars.

---------------------------------------------------------
Title: Relation between trees of fragmenting granules and
supergranulation evolution
Authors: Roudier, Th.; Malherbe, J. M.; Rieutord, M.; Frank, Z.
2016A&A...590A.121R Altcode: 2016arXiv160404118R
Context. The determination of the underlying mechanisms of the
magnetic elements diffusion over the solar surface is still a
challenge. Understanding the formation and evolution of the solar
network (NE) is a challenge, because it provides a magnetic flux over
the solar surface comparable to the flux of active regions at solar
maximum. Aims: We investigate the structure and evolution of
interior cells of solar supergranulation. From Hinode observations,
we explore the motions on solar surface at high spatial and temporal
resolution. We derive the main organization of the flows inside
supergranules and their effect on the magnetic elements. 
Methods: To probe the superganule interior cell, we used the trees of
fragmenting granules (TFG) evolution and their relations to horizontal
flows. Results: Evolution of TFG and their mutual interactions
result in cumulative effects able to build horizontal coherent flows
with longer lifetime than granulation (1 to 2 h) over a scale up to
12”. These flows clearly act on the diffusion of the intranetwork
(IN) magnetic elements and also on the location and shape of the
network. Conclusions: From our analysis during 24 h, TFG appear
as one of the major elements of the supergranules which diffuse
and advect the magnetic field on the Sun's surface. The strongest
supergranules contribute the most to magnetic flux diffusion in the
solar photosphere. Movies are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201628111/olm">http://www.aanda.org</A>

---------------------------------------------------------
Title: The photospheric solar oxygen project. III. Investigation of
the centre-to-limb variation of the 630 nm [O I]-Ni I blend
Authors: Caffau, E.; Ludwig, H. -G.; Steffen, M.; Livingston, W.;
Bonifacio, P.; Malherbe, J. -M.; Doerr, H. -P.; Schmidt, W.
2015A&A...579A..88C Altcode: 2015arXiv150600931C
Context. The solar photospheric abundance of oxygen is still a matter
of debate. For about ten years some determinations have favoured a
low oxygen abundance which is at variance with the value inferred by
helioseismology. Among the oxygen abundance indicators, the forbidden
line at 630 nm has often been considered the most reliable even
though it is blended with a Ni i line. In Papers I and II of this
series we reported a discrepancy in the oxygen abundance derived
from the 630 nm and the subordinate [O I] line at 636 nm in dwarf
stars, including the Sun. Aims: Here we analyse several,
in part new, solar observations of the centre-to-limb variation
of the spectral region including the blend at 630 nm in order to
separate the individual contributions of oxygen and nickel. 
Methods: We analyse intensity spectra observed at different limb
angles in comparison with line formation computations performed on a
CO5BOLD 3D hydrodynamical simulation of the solar atmosphere. 
Results: The oxygen abundances obtained from the forbidden line at
different limb angles are inconsistent if the commonly adopted nickel
abundance of 6.25 is assumed in our local thermodynamic equilibrium
computations. With a slightly lower nickel abundance, A(Ni) ≈ 6.1,
we obtain consistent fits indicating an oxygen abundance of A(O) = 8.73
± 0.05. At this value the discrepancy with the subordinate oxygen
line remains. Conclusions: The derived value of the oxygen
abundance supports the notion of a rather low oxygen abundance in the
solar photosphere. However, it is disconcerting that the forbidden
oxygen lines at 630 and 636 nm give noticeably different results,
and that the nickel abundance derived here from the 630 nm blend is
lower than expected from other nickel lines.

---------------------------------------------------------
Title: Families of Granules, Flows, and Acoustic Events in the Solar
Atmosphere from Hinode Observations
Authors: Malherbe, J. -M.; Roudier, T.; Frank, Z.; Rieutord, M.
2015SoPh..290..321M Altcode: 2014SoPh..tmp..189M
We investigate the relationship between trees of fragmenting granules
(TFG), horizontal and vertical flows, and acoustic events (AE) in the
photospheric network. AE are spatially concentrated and short-duration
locations of acoustic energy flux. We performed observations at disk
center of a 2D field of view (FOV) with high spatial and temporal
resolutions provided by the Solar Optical Telescope onboard Hinode. Line
profiles of Fe I 557.6 nm were recorded by the Narrow-band Filter
Imager on an 80″×36″ FOV during five hours with a cadence of
22 seconds and 0.08″ pixel size. Vertical velocities were derived
at two atmospheric levels allowing the determination of the energy
flux at the acoustic frequency of 3.3 mHz. Families of granules and
horizontal velocities were obtained from local correlation tracking
(LCT) after segmentation and labeling of either continuum intensities
or granular Doppler shifts. AE exhibit durations in the range 0.25
to 1 hour compatible with the lifetime of families (80 % do not last
more than two hours). High-energy AE have the shortest lifetimes. We
found that most AE occur in intergranular lanes located in or close
to the boundaries between different families (called inter families)
in regions with predominantly downward vertical motions and horizontal
converging flows. In contrast, diverging flows are observed inside
families, with a few AE in the intergranules. At the beginning of the
sequence, when families are not yet detected, the distribution of AE
is not uniform and is already organized at spatial lengths related to
the mesogranular scale, with maximum contribution in the range 5″
to 10″, fully compatible with the scale of the maximum contribution
of families in the TFG space. Although all sizes and durations seem
to exist for families, their number decreases with increasing size
and lifetime.

---------------------------------------------------------
Title: Time Evolution of Force-Free Parameter and Free Magnetic
Energy in Active Region NOAA 10365
Authors: Valori, G.; Romano, P.; Malanushenko, A.; Ermolli, I.;
Giorgi, F.; Steed, K.; van Driel-Gesztelyi, L.; Zuccarello, F.;
Malherbe, J. -M.
2015SoPh..290..491V Altcode:
We describe the variation of the accumulated coronal helicity derived
from the magnetic helicity flux through the photosphere in active region
(AR) NOAA 10365, where several large flares and coronal mass ejections
(CMEs) occurred. We used SOHO/MDI full-disk line-of-sight magnetograms
to measure the helicity flux, and the integral of GOES X-ray flux as a
proxy of the coronal energy variations due to flares or CMEs. Using the
linear force-free field model, we transformed the accumulated helicity
flux into a time sequence of the force-free parameter α accounting for
flares or CMEs via the proxy derived from GOES observations. This method
can be used to derive the value of α at different times during the
AR evolution, and is a partial alternative to the commonly used match
of field lines with EUV loops. By combining the accumulated helicity
obtained from the observations with the linear force-free theory, we
describe the main phases of the emergence process of the AR, and relate
them temporally with the occurrence of flares or CMEs. Additionally,
a comparison with the loop-matching method of fixing alpha at each time
independently shows that the proposed method may be helpful in avoiding
unrealistic or undetermined values of alpha that may originate from
an insufficient quality of the image used to identify coronal loops
at a given time. For the relative intensity of the considered events,
the linear force-free field theory implies that there is a direct
correlation between the released energy on the one hand and the product
of the coronal helicity with the variation of α due to the event on
the other. Therefore, the higher the value of the accumulated coronal
helicity, the smaller the force-free parameter variation required to
produce the same decrease in the free energy during the CMEs.

---------------------------------------------------------
Title: Optical characterization of the breadboard narrowband
prefilters for Solar Orbiter PHI
Authors: Dominguez-Tagle, Carlos; Appourchaux, Thierry; Ruiz
de Galarreta, Claudia; Fourmond, Jean-Jacques; Philippon, Anne;
Le Clec'h, Jean-Christophe; Bouzit, Mehdi; Bommier, Véronique;
Le Cocguen, Regis; Crussaire, Daniel; Malherbe, Jean-Marie
2014SPIE.9143E..5GD Altcode:
The Polarimetric and Helioseismic Imager (PHI) on board of Solar
Orbiter will observe the Sun to measure the photospheric vector
magnetic field and the line-of-sight velocity. It will employ
a narrowband filtergraph (FG) to scan the FeI 6173 Å absorption
line. At different spectral positions, the polarization state of the
incoming light will be analyzed. The FG will provide a tuning range
to scan the line, the continuum, and to compensate for the spacecraft
radial velocity, as it will approach to the Sun down to 0.28 AU. The
FG includes a Fabry-Perot etalon and two narrowband prefilters. The
bandpass of the narrowest one has a nominal Full Width at Half Maximum
(FWHM) of 2.7 Å. The measurement of the prefilters characteristics is
essential for the instrument calibration. Here we present the results
of the breadboard prefilters characterization, which is an important
milestone in the development of the instrument.

---------------------------------------------------------
Title: The S4I prototype, a beam-slicer dedicated to the new
generation Multichannel Subtractive Double Pass for EST imaging
spectropolarimetry
Authors: Sayède, Frédéric; Mein, Pierre; Malherbe, Jean-Marie;
Amans, Jean-Philippe; Crussaire, Daniel; Lecocguen, Regis
2014SPIE.9147E..6FS Altcode:
For the future European Solar Telescope (EST) the Observatoire de Paris
proposes a new generation of MSDP, an imaging spectro-polarimetry
instrument. To validate this new generation, we develop a plane
micro-mirrors beam slicer prototype that is tested and validated on
an optical bench and on existing telescopes. The prototype called S4I
(Spectral Sampling with Slicer for Solar Instrumentation) is built and
tested at the Observatoire de Paris. It validates the opto-mechanical
feasibility of the new beam slicer. After a complete description of the
system, we present the first images. We evaluate the performances of
the prototype and compare them to the requirements for the beam-slicer
dedicated to the future EST.

---------------------------------------------------------
Title: S4EI (Spectral Sampling with Slicer for Stellar and
Extragalactical Instrumentation), a new-generation of 3D
spectro-imager dedicated to night astronomy
Authors: Sayède, Frédéric; Puech, Mathieu; Mein, Pierre;
Bonifacio, Piercarlo; Malherbe, Jean-Marie; Galicher, Raphaël.;
Amans, Jean-Philippe; Fasola, Gilles
2014SPIE.9147E..3OS Altcode:
Multichannel Subtractive Double Pass (MSDP) spectrographs have
been widely used in solar spectroscopy because of their ability to
provide an excellent compromise between field of view and spatial
and spectral resolutions. Compared with other types of spectrographs,
MSDP can deliver simultaneous monochromatic images at higher spatial
and spectral resolutions without any time-scanning requirement (as
with Fabry-Perot spectrographs), and with limited loss of flux. These
performances are obtained thanks to a double pass through the dispersive
element. Recent advances with VPH (Volume phase holographic) Grisms
as well as with image slicers now make MSDP potentially sensitive to
much smaller fluxes. We present S4EI (Spectral Sampling with Slicer for
Stellar and Extragalactical Instrumentation), which is a new concept for
extending MSDP to night-time astronomy. It is based on new generation
reflecting plane image slicers working with large apertures specific
to night-time telescopes. The resulting design could be potentially
very attractive and innovative for different domains of astronomy,
e.g., the simultaneous spatial mapping of accurately flux-calibrated
emission lines between OH sky lines in extragalactic astronomy or the
simultaneous imaging of stars, exoplanets and interstellar medium. We
present different possible MSDP/S4EI configurations for these science
cases and expected performances on telescopes such as the VLT.

---------------------------------------------------------
Title: Structure and evolution of solar supergranulation using
SDO/HMI data
Authors: Roudier, Th.; Švanda, M.; Rieutord, , M.; Malherbe, J. M.;
Burston, R.; Gizon, L.
2014A&A...567A.138R Altcode: 2014arXiv1407.0196R
Context. Studying the motions on the solar surface is fundamental
for understanding how turbulent convection transports energy and how
magnetic fields are distributed across the solar surface. Aims:
From horizontal velocity measurements all over the visible disc of the
Sun and using data from the Solar Dynamics Observatory/Helioseismic and
Magnetic Imager (SDO/HMI), we investigate the structure and evolution
of solar supergranulation. Methods: Horizontal velocity fields
were measured by following the proper motions of solar granules
using a newly developed version of the coherent structure tracking
code. With this tool, maps of horizontal divergence were computed. We
then segmented and identified supergranular cells and followed their
histories by using spatio-temporal labelling. With this data set we
derived the fundamental properties of supergranulation, including their
motion. Results: We find values of the fundamental parameters
of supergranulation similar to previous studies: a mean lifetime of
1.5 days and a mean diameter of 25 Mm. The tracking of individual
supergranular cells reveals the solar differential rotation and a
poleward circulation trend of the meridional flow. The shape of the
derived differential rotation and meridional flow does not depend on
the cell size. If there is a background magnetic field, the diverging
flows in supergranules are weaker. Conclusions: This study
confirms that supergranules are suitable tracers that may be used to
investigate the large-scale flows of the solar convection as long as
they are detectable enough on the surface.

---------------------------------------------------------
Title: Coronal Magnetic Reconnection Driven by CME Expansion—the
2011 June 7 Event
Authors: van Driel-Gesztelyi, L.; Baker, D.; Török, T.; Pariat, E.;
Green, L. M.; Williams, D. R.; Carlyle, J.; Valori, G.; Démoulin,
P.; Kliem, B.; Long, D. M.; Matthews, S. A.; Malherbe, J. -M.
2014ApJ...788...85V Altcode: 2014arXiv1406.3153V
Coronal mass ejections (CMEs) erupt and expand in a magnetically
structured solar corona. Various indirect observational pieces of
evidence have shown that the magnetic field of CMEs reconnects with
surrounding magnetic fields, forming, e.g., dimming regions distant
from the CME source regions. Analyzing Solar Dynamics Observatory
(SDO) observations of the eruption from AR 11226 on 2011 June 7, we
present the first direct evidence of coronal magnetic reconnection
between the fields of two adjacent active regions during a CME. The
observations are presented jointly with a data-constrained numerical
simulation, demonstrating the formation/intensification of current
sheets along a hyperbolic flux tube at the interface between the CME
and the neighboring AR 11227. Reconnection resulted in the formation of
new magnetic connections between the erupting magnetic structure from
AR 11226 and the neighboring active region AR 11227 about 200 Mm from
the eruption site. The onset of reconnection first becomes apparent
in the SDO/AIA images when filament plasma, originally contained
within the erupting flux rope, is redirected toward remote areas in
AR 11227, tracing the change of large-scale magnetic connectivity. The
location of the coronal reconnection region becomes bright and directly
observable at SDO/AIA wavelengths, owing to the presence of down-flowing
cool, dense (1010 cm-3) filament plasma in its
vicinity. The high-density plasma around the reconnection region is
heated to coronal temperatures, presumably by slow-mode shocks and
Coulomb collisions. These results provide the first direct observational
evidence that CMEs reconnect with surrounding magnetic structures,
leading to a large-scale reconfiguration of the coronal magnetic field.

---------------------------------------------------------
Title: 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: 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: 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: Magnetic reconnection driven by filament eruption in the 7
June 2011 event
Authors: van Driel-Gesztelyi, L.; Baker, D.; Török, T.; Pariat, E.;
Green, L. M.; Williams, D. R.; Carlyle, J.; Valori, G.; Démoulin,
P.; Matthews, S. A.; Kliem, B.; Malherbe, J. -M.
2014IAUS..300..502V Altcode:
During an unusually massive filament eruption on 7 June 2011,
SDO/AIA imaged for the first time significant EUV emission around a
magnetic reconnection region in the solar corona. The reconnection
occurred between magnetic fields of the laterally expanding CME
and a neighbouring active region. A pre-existing quasi-separatrix
layer was activated in the process. This scenario is supported by
data-constrained numerical simulations of the eruption. Observations
show that dense cool filament plasma was re-directed and heated in
situ, producing coronal-temperature emission around the reconnection
region. These results provide the first direct observational evidence,
supported by MHD simulations and magnetic modelling, that a large-scale
re-configuration of the coronal magnetic field takes place during
solar eruptions via the process of magnetic reconnection.

---------------------------------------------------------
Title: The photospheric solar oxygen project. II. Non-concordance
of the oxygen abundance derived from two forbidden lines
Authors: Caffau, E.; Ludwig, H. -G.; Malherbe, J. -M.; Bonifacio,
P.; Steffen, M.; Monaco, L.
2013A&A...554A.126C Altcode: 2013arXiv1305.1763C
Context. In the Sun, the two forbidden [O i] lines at 630 and 636 nm
were previously found to provide discrepant oxygen abundances. Aims: We investigate whether this discrepancy is peculiar to the
Sun or whether it is also observed in other stars. Methods:
We make use of high-resolution, high signal-to-noise ratio spectra of
four dwarf to turn-off stars, five giant stars, and one sub-giant star
observed with THEMIS, HARPS, and UVES to investigate the coherence of
the two lines. Results: The two lines provide oxygen abundances
that are consistent, within observational errors, in all the giant
stars examined by us. On the other hand, for the two dwarf stars for
which a measurement was possible, for Procyon, and for the sub-giant
star Capella, the 636 nm line provides systematically higher oxygen
abundances, as already seen for the Sun. Conclusions: The
only two possible reasons for the discrepancy are a serious error
in the oscillator strength of the Ni i line blending the 630 nm line
or the presence of an unknown blend in the 636 nm line, which makes
the feature stronger. The CN lines blending the 636 nm line cannot
be responsible for the discrepancy. The Ca i autoionisation line, on
the red wing of which the 636 nm line is formed, is not well modelled
by our synthetic spectra. However, a better reproduction of this line
would result in even higher abundances from the 636 nm, thus increasing
the discrepancy. Based on observations collected at ESO Paranal
Observatory, Programme 182.D-5053(A).

---------------------------------------------------------
Title: Comparison of solar horizontal velocity fields from SDO/HMI
and Hinode data
Authors: Roudier, Th.; Rieutord, M.; Prat, V.; Malherbe, J. M.; Renon,
N.; Frank, Z.; Švanda, M.; Berger, T.; Burston, R.; Gizon, L.
2013A&A...552A.113R Altcode: 2013arXiv1303.4271R
Context. The measurement of the Sun's surface motions with a high
spatial and temporal resolution is still a challenge. Aims:
We wish to validate horizontal velocity measurements all over the
visible disk of the Sun from Solar Dynamics Observatory/ Helioseismic
and Magnetic Imager (SDO/HMI) data. Methods: Horizontal velocity
fields are measured by following the proper motions of solar granules
using a newly developed version of the coherent structure tracking
(CST) code. The comparison of the surface flows measured at high
spatial resolution (Hinode, 0.1 arcsec) and low resolution (SDO/HMI,
0.5 arcsec) allows us to determine corrections to be applied to
the horizontal velocity measured from HMI white light data. 
Results: We derive horizontal velocity maps with spatial and temporal
resolutions of respectively 2.5 Mm and 30 min. From the two components
of the horizontal velocity vx and vy measured
in the sky plane and the simultaneous line of sight component from
SDO/HMI dopplergrams vD, we derive the spherical velocity
components (vr, vθ, vϕ). The
azimuthal component vϕ gives the solar differential rotation
with a high precision (± 0.037 km s-1) from a temporal
sequence of only three hours. Conclusions: By following the
proper motions of the solar granules, we can revisit the dynamics of
the solar surface at high spatial and temporal resolutions from hours
to months and years with the SDO data.

---------------------------------------------------------
Title: The Power Spectrum of the Solar Surface Flows from Hinode
Data and First Observations with MOF/CALAS Pic-du-Midi
Authors: Roudier, T.; Rieutord, M.; Rincon, F.; Malherbe, J. -M.;
Brito, D.; Berger, T.; Frank, Z.; Parés, L.; Bourrec, E.; Beigbeder,
F.
2012ASPC..454...47R Altcode:
Many features of solar surface turbulence, like the supergranulation,
are still poorly understood.We use long time series of images taken by
the Solar Optical Telescope on board the Hinode satellite to determine
the velocity fields. The dynamics in the subgranulation range can
be investigated with unprecedented precision thanks to the absence
of seeing effects and the use of the MTF of SOT for correcting the
spectra. The first MOF/CALAS/Pic-du-Midi results are also shown.

---------------------------------------------------------
Title: Acoustic Events in the Solar Atmosphere from Hinode/SOT
NFI Observations
Authors: Malherbe, J. -M.; Roudier, T.; Rieutord, M.; Berger, T.;
Franck, Z.
2012SoPh..278..241M Altcode: 2012arXiv1207.1170M
We investigate the properties of acoustic events (AEs), defined as
spatially concentrated and short duration energy flux, in the quiet
Sun, using observations of a 2D field of view (FOV) with high spatial
and temporal resolution provided by the Solar Optical Telescope (SOT)
onboard Hinode. Line profiles of Fe I 557.6 nm were recorded by the
Narrow-band Filter Imager (NFI) on a 82″×82″ FOV during 75 min with
a time step of 28.75 s and 0.08″ pixel size. Vertical velocities were
computed at three atmospheric levels (80, 130, and 180 km) using the
bisector technique, allowing the determination of energy flux to be
made in the range 3 - 10 mHz using two complementary methods (Hilbert
transform and Fourier power spectrum). Horizontal velocities were
computed using local correlation tracking (LCT) of continuum intensities
providing divergences. We found that the net energy flux is upward. In
the range 3 - 10 mHz, a full FOV space and time averaged flux of 2700 W
m−2 (lower layer 80 - 130 km) and 2000 W m−2
(upper layer 130 - 180 km) is concentrated in less than 1 % of the
solar surface in the form of narrow (0.3″) AE. Their total duration
(including rise and decay) is of the order of 103 s. Inside
each AE, the mean flux is 1.6×105 W m−2
(lower layer) and 1.2×105 W m−2 (upper). Each
event carries an average energy (flux integrated over space and time)
of 2.5×1019 J (lower layer) to 1.9×1019 J
(upper). More than 106 events could exist permanently on
the Sun, with a birth and decay rate of 3500 s−1. Most
events occur in intergranular lanes, downward velocity regions, and
areas of converging motions.

---------------------------------------------------------
Title: Some Dynamic Analysis of the Photosphere from Hinode/SOT and
SDO/HMI Observations
Authors: Roudier, T.; Malherbe, J.; Rieutord, M.; Berger, T.; Frank,
Z.; Prat, V.; Renon, N.; Gizon, L.; Svanda, M.
2012ASPC..456...65R Altcode:
We first present the important role played by the families of granule
(or Tree of Fragmenting granules) in the formation of the photospheric
network. Then, we describe the occurence and characteristics of
acoustic events (AE), defined as spatially concentrated energy flux,
in the quiet Sun. Finally, we present how horizontal velocities obtained
from SDO/HMI data are calibrated by using Hinode/SOT observations.

---------------------------------------------------------
Title: Quasi full-disk maps of solar horizontal velocities using
SDO/HMI data
Authors: Roudier, Th.; Rieutord, M.; Malherbe, J. M.; Renon, N.;
Berger, T.; Frank, Z.; Prat, V.; Gizon, L.; Švanda, M.
2012A&A...540A..88R Altcode: 2012arXiv1203.0514R
 Aims: For the first time, the motion of granules (solar plasma
on the surface on scales larger than 2.5 Mm) has been followed over
the entire visible surface of the Sun, using SDO/HMI white-light
data. Methods: Horizontal velocity fields are derived from image
correlation tracking using a new version of the coherent structure
tracking algorithm. The spatial and temporal resolutions of the
horizontal velocity map are 2.5 Mm and 30 min, respectively. Results: From this reconstruction, using the multi-resolution
analysis, one can obtain to the velocity field at different scales
with its derivatives such as the horizontal divergence or the vertical
component of the vorticity. The intrinsic error on the velocity is
~0.25 km s-1 for a time sequence of 30 min and a mesh size
of 2.5 Mm. This is acceptable compared to the granule velocities, which
range between 0.3 km s-1 and 1.8 km s-1. A high
correlation between velocities computed from Hinode and SDO/HMI has
been found (85%). From the data we derive the power spectrum of the
supergranulation horizontal velocity field, the solar differential
rotation, and the meridional velocity.

---------------------------------------------------------
Title: On the power spectrum of solar surface flows
Authors: Rieutord, M.; Roudier, T.; Rincon, F.; Malherbe, J. -M.;
Meunier, N.; Berger, T.; Frank, Z.
2010A&A...512A...4R Altcode: 2009arXiv0911.3319R
Context. The surface of the Sun provides us with a unique and
very detailed view of turbulent stellar convection. Studying its
dynamics can therefore help us make significant progress in stellar
convection modelling. Many features of solar surface turbulence like
the supergranulation are still poorly understood. Aims: The aim
of this work is to give new observational constraints on these flows
by determining the horizontal scale dependence of the velocity and
intensity fields, as represented by their power spectra, and to offer
some theoretical guidelines to interpret these spectra. Methods:
We use long time-series of images taken by the Solar Optical Telescope
(SOT) on board the Hinode satellite; we reconstruct both horizontal
(by granule tracking) and vertical (by Doppler effect) velocity
fields in a field-of-view of ~ 75 × 75 Mm2. The dynamics
in the subgranulation range can be investigated with unprecedented
precision thanks to the absence of seeing effects and the use of the
modulation transfer function of SOT for correcting the spectra. 
Results: At small subgranulation scales down to 0.4 Mm the spectral
density of kinetic energy associated with vertical motions exhibits
a k-10/3-like power law, while the intensity fluctuation
spectrum follows either a k-17/3 or a k-3-like
power law at the two continuum levels investigated (525 and 450
nm respectively). We discuss the possible physical origin of these
scalings and interpret the combined presence of k-17/3 and
k-10/3 power laws for the intensity and vertical velocity
as a signature of buoyancy-driven turbulent dynamics in a strongly
thermally diffusive regime. In the mesogranulation range and up to a
scale of 25 Mm, we find that the amplitude of the vertical velocity
field decreases like λ-3/2 with the horizontal scale
λ. This behaviour corresponds to a k2 spectral power
law. Still in the 2.5-10 Mm mesoscale range, we find that intensity
fluctuations in the blue continuum also follow a k2
power law. In passing we show that granule tracking cannot sample
scales below 2.5 Mm. We finally further confirm the presence of a
significant supergranulation energy peak at 30 Mm in the horizontal
velocity power spectrum and show that the emergence of a pore erases
this spectral peak. We tentatively estimate the scale height of the
vertical velocity field in the supergranulation range and find 1 Mm;
this value suggests that supergranulation flows are shallow.

---------------------------------------------------------
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: Supergranulation, Network Formation, and TFGs Evolution from
Hinode Observations
Authors: Roudier, T.; Rincon, F.; Rieutord, M.; Brito, D.; Beigbeder,
F.; Parès, L.; Malherbe, J. -M.; Meunier, N.; Berger, T.; Frank, Z.
2009ASPC..415..203R Altcode:
In this paper, we analyse a a 48h high-resolution time sequence of the
quiet Sun photosphere obtained with the Solar Optical Telescope onboard
Hinode. Using floating corks advected by velocity fields inferred from
photometry measurements, we show that long-living Trees of Fragmenting
Granules play a crucial role in the advection of small-scale magnetic
fields and in the build-up of the magnetic network.

---------------------------------------------------------
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: Mesoscale dynamics on the Sun's surface from HINODE
observations
Authors: Roudier, Th.; Rieutord, M.; Brito, D.; Rincon, F.; Malherbe,
J. M.; Meunier, N.; Berger, T.; Frank, Z.
2009A&A...495..945R Altcode: 2009arXiv0902.2299R
Context: Aims: The interactions of velocity scales on the Sun's
surface, from granulation to supergranulation are still not understood,
nor are their interaction with magnetic fields. We thus aim at giving
a better description of dynamics in the mesoscale range which lies
between the two scales mentioned above. Methods: We analyse a
48 h high-resolution time sequence of the quiet Sun photosphere at
the disk center obtained with the Solar Optical Telescope onboard
Hinode. The observations, which have a field of view of 100´´ ×
100´´, typically contain four supergranules. We monitor in detail the
motion and evolution of granules as well as those of the radial magnetic
field. Results: This analysis allows us to better characterize
Trees of Fragmenting Granules issued from repeated fragmentation of
granules, especially their lifetime statistics. Using floating corks
advected by measured velocity fields, we show their crucial role
in the advection of the magnetic field and in the build up of the
network. Finally, thanks to the long duration of the time series, we
estimate that the turbulent diffusion coefficient induced by horizontal
motion is approximately 430 km2 s-1. Conclusions: These results demonstrate that the long living families
contribute to the formation of the magnetic network and suggest that
supergranulation could be an emergent length scale building up as small
magnetic elements are advected and concentrated by TFG flows. Our
estimate for the magnetic diffusion associated with this horizontal
motion might provide a useful input for mean-field dynamo models.

---------------------------------------------------------
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: 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: Turbulent fields in the quiet sun from Hanle and Zeeman
effects with THEMIS
Authors: López Ariste, A.; Malherbe, J. M.; Manso Sainz, R.; Asensio
Ramos, A.; Ramírez Vélez, J. C.; Martínez González, M.
2007sf2a.conf..596L Altcode:
The measurement of the Sr I line with full polarimetry and spatial
resolution with THEMIS has provided the unexpected result of an apparent
correlation between the Hanle effect signals and the Zeeman effect
signals on this line. Traditionnally, Hanle effect signals in linear
polarisation have been interpreted as the signature of unorganized,
turbulent fields, while Zeeman effect signals -mostly in circular
polarisation- were interpreted as structured fields. The correlation
between both observed by THEMIS requires a change of mind respect to the
picture of the quiet sun, with fewer structured fields and a turbulent
field visible also in deep magnetograms. This picture is supported also
by recent results with Mn lines with strong coupling with its hyperfine
structure and of center-to-limb histograms of Zeeman amplitudes.

---------------------------------------------------------
Title: Resonance polarization of the solar 455.4 nm BaII line:
diagnostics of chromospheric magnetic fields
Authors: Michel, C.; Faurobert, M.; Arnaud, J.; Malherbe, J. M.
2007sf2a.conf..607M Altcode:
The BaII resonance line at 455.4 nm is formed in the low solar
chromopshere. It is significantly linearly polarized outside active
regions and close to the solar limb. This so-called resonance
polarization is sensitive to the Hanle effect of weak magnetic
fields. We report on numerical simulations of the intensity and
resonance polarization profiles in the line and in the adjacent
continuum, in the quiet solar atmosphere and we compare them to
observations performed at the Jean Rosch refractor at the Pic du Midi
Observatory. In the simulations we take into account non-LTE multilevel
coupling, multiple scattering and partial frequency redistribution, and
we neglect the hyperfine structure of the odd isotopes. This allows to
model the central part of the line core and the wings quite well. Then
we investigate the diagnostic potential of the line core polarization
for weak unresolved magnetic fields in the low chromosphere. We find
that the observed polarization rates are in good agreement with the
simulations if we take into account the Hanle effect of weak magnetic
fields on the order of 60 to 75 Gauss.

---------------------------------------------------------
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: Magnetic flux tubes observed with THEMIS/MSDP
Authors: Mein, P.; Mein, N.; Faurobert, M.; Aulanier, G.; Malherbe,
J. -M.
2007A&A...463..727M Altcode:
Aims:We use spectro-polarimetric THEMIS/MSDP data to investigate the 3D
structure of solar magnetic-flux tubes across the upper photosphere. Methods: Profiles of the sodium D1 line 589.6 nm are analysed by
the bisector method at different wavelengths from the core to the
wings, for several bright features. They are compared to synthetic
profiles derived from 2D magnetic models of flux tubes and from the
MULTI code for NLTE line profiles. Three different magnetic models of
flux tubes are investigated. Model (I) consists of a single flux tube
that compensates for the horizontal Lorentz forces exactly, while model
(II) uses a compromise between horizontal and vertical components. Model
(III), a conglomerate of thinner flux tubes, leads to the best agreement
with observations. Results: (1) The combination of seeing effects
(small filling factor) with slopes of line profiles, which are different
in the flux tubes and the neighbouring quiet sun, account for the
decrease in observed magnetic field from line core to line wings in
central parts of magnetic features, as well as the decrease in magnetic
fluxes integrated over the whole magnetic features. (2) The expansion
with height of single magnetic flux tubes (models I and II) accounts for
the increase in the size of magnetic features from line wings to line
core. (3) Pure thermodynamical criteria characterising Dopplershifts
and line-intensity fluctuations of magnetic and non-magnetic features
have been proven by observations. Conclusions: . We could account
for differential Zeeman effects along the D1 line profile by combining
expansion of flux tubes with height, low gas pressure inside flux tubes,
and small filling factor due to seeing effects. Better agreement with
observations, in particular with respect to magnetic field amplitudes,
will probably need 3D models that take velocity fields and horizontal
gradients of temperature into account.

---------------------------------------------------------
Title: First observations of the second solar spectrum with spatial
resolution at the Lunette Jean Rösch
Authors: Malherbe, J. -M.; Moity, J.; Arnaud, J.; Roudier, Th.
2007A&A...462..753M Altcode:
Context: A new polarimeter has been installed at the focus of the 50
cm refractor of the Lunette Jean Rösch (LJR), previously known as
Turret Dome, Pic du Midi, France, for spectroscopic observations of
weak solar magnetic fields. Fields can be derived through the Hanle
effect from the depolarization of the second solar spectrum (i.e. the
linearly polarized spectrum at the limb). Aims: We present the
first observations with spatial resolution based on the new device
performed with the large 8 m Echelle spectrograph, or recorded in
imagery mode through narrow band filters. The observations started
in April 2004, especially in the blue part of the spectrum where our
instrumentation has a particularly good efficiency. The capabilities
and the characteristics of the new instrument are briefly described. We
observed several lines of the second solar spectrum with the slit
of the spectrograph orthogonal to the limb to study the polarization
as a function of limb distance (which is related to altitude in the
atmosphere), and several spectral windows in imagery to determine
the average continuum polarization. Methods: The polarimeter
uses Nematic Liquid Crystal (NLC) technology at the primary focus
of the refractor, in spectroscopic or imagery mode. Results:
A continuous polarization profile through the limb is presented for
the photospheric SrI 460.7 nm line, the low chromospheric BaII 455.4 nm
line, and the CaI 422.7 nm line within a distance of 120´´, together
with measurements of the mean continuum polarization obtained in
imagery mode. Preliminary results of the polarization of the SrI 460.7
nm line are also shown at 40´´ from the limb, as a function of the
brightness of structures visible in the continuum (granulation). They
reveal a tendency for the polarization to be weaker in dark features
(intergranules) than in bright ones (granules), suggesting a stronger
magnetic field in intergranular lanes. As example the enigmatic and
weak polarization signal in the core of the NaD1 589.6 nm line is
presented. Conclusions: .Some aspects of the spatial variation
of the polarization with respect to the granulation pattern require
further investigation at higher spatial resolution. Appendices
A-C are only available in elctronic form at http://www.aanda.org

---------------------------------------------------------
Title: Magnetic flux tubes observed with THEMIS/MSDP .
Authors: Mein, P.; Mein, N.; Faurobert, M.; Aulanier, G.; Malherbe,
J. -M.
2007MmSAI..78...92M Altcode:
We use 2D spectro-polarimetric data of the NaD1 line to investigate
magnetic flux tubes at several levels of the solar photosphere: -
magnetic and non-magnetic bright features can be discriminated by simple
criteria of intensities and dopplershifts. - 2D magnetic models
and NLTE line profiles are compared to observations : combination of
seeing effects and departures between slopes of line profiles in flux
tubes and neighbouring photosphere account for vertical gradients of
line-of-sight (LOS) magnetic field measurements. - Best qualitative
agreements are obtained with clusters of magnetic flux tubes.

---------------------------------------------------------
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: Spectro polarimetry with liquid crystals .
Authors: Malherbe, J. -M.; Roudier, Th.; Moity, J.; Mein, P.; Arnaud,
J.; Muller, R.
2007MmSAI..78..203M Altcode:
We report spectro polarimetric observations made with the spectrograph
of the Lunette Jean Rösch at Pic du Midi, France. We have tested
Ferroelectric (FLC) and Nematic (NLC) Liquid Crystals. The instrument
setup is briefly decribed, together with first observations of
magnetic fields obtained with the Multichannel Subtractive Double Pass
(MSDP). Polarization analysis of various spectral lines performed with
the single pass (SP) spectrograph in active regions or at the limb is
also presented.

---------------------------------------------------------
Title: Interpretation of the Second Solar Spectrum of the Sr I 4607
Å Line Observed at THEMIS and Pic-du-Midi
Authors: Derouich, M.; Bommier, V.; Malherbe, J. -M.; Landi
Degl'Innocenti, E.; Molodij, G.; Sahal-Bréchot, S.
2006ASPC..358..120D Altcode:
The Hanle effect is the only tool available for measuring turbulent
(i.e., spatially unresolved) magnetic fields at the surface of the quiet
Sun. The Hanle-effect diagnostics relies on the discrepancy between
the linear polarization calculated in the absence of a magnetic field
and the observed polarization. We interpreted the linear polarization
of the Sr I 4607 Å line, observed at THEMIS (December 7-9, 2002) and
Pic-du-Midi (May 14, 2004), in terms of the Hanle effect. We present
here the main results of this study. In particular, we stress the
importance of a proper adjustment of the theoretical intensity profile
to the observed one, through the application of a zero-field model, the
magnetic field being determined in a second step from the line-center
polarization degree. With the spatial resolution and coverage of
the Pic-du-Midi data (1 arcsec resolution, 132 distances from the limb),
we can also attain depth probing of the turbulent magnetic strength,
and we discuss whether this can vary within the range of heights of
formation for the line center.

---------------------------------------------------------
Title: Second solar spectrum of the Sr I 4607 Å line: depth probing
of the turbulent magnetic field strength in a quiet region
Authors: Derouich, M.; Bommier, V.; Malherbe, J. M.; Landi
Degl'Innocenti, E.
2006A&A...457.1047D Altcode:
Aims.This paper is devoted to an interpretation of Quiet-Sun,
spatially-resolved spectropolarimetric observations of the Hanle effect
in terms of turbulent weak magnetic field determination. Methods:
. Observations: the slit was positioned perpendicular to the limb,
and the spatial resolution along the slit was 1 arcsec, leading to a
depth probing along 132 different limb distances. The new polarimeter
of the Pic-du-Midi Turret Dome was used on May 14, 2004 to observe a
quiet region at the East limb equator in the resonance line of neutral
Strontium at 4607 Å. Results: . For each limb distance, we
properly adjusted the theoretical intensity profile obtained by applying
a zero-field model to the observed one. Micro- and macroturbulent
velocities were thus derived (average values v{micro}=1.77
km s-1 and v{macro}=1.95 km s-1). The
magnetic field was determined in a second step by interpreting the Hanle
effect on the line center linear polarization degree. The depolarizing
collisions with neutral hydrogen were taken fully into account through
a semi-classical calculation of their rates. An average value of B=38
Gauss was thus derived. Finally, error bars on the magnetic field values
were evaluated from a) the polarimetric inaccuracy, b) the limb distance
determination inaccuracy, and c) the uncertainty on our theoretical
collisional depolarizing rates that we evaluated. This combination leads
to 10-20% as total relative error on the magnetic field determination
by the Hanle effect method. Since the inaccuracy due to the model
itself was hard to properly evaluate, it was ignored. An uncertainty
of ±60 km on the line formation depth was, however, derived from the
contribution functions. The magnetic field is found to increase slowly
with height in the height range 220-300 km above τ5000=1
and then decrease in the height range 300-370 km.

---------------------------------------------------------
Title: Sub arcsec evolution of solar magnetic fields
Authors: Roudier, Th.; Malherbe, J. M.; Moity, J.; Rondi, S.; Mein,
P.; Coutard, Ch.
2006A&A...455.1091R Altcode:
Context: .The evolution of the concentrated magnetic field in
flux tubes is one challenge of the nowadays Solar physics which
requires time sequence with high spatial resolution. Aims: .Our
objective is to follow the properties of the magnetic concentrations
during their life, in intensity (continuum and line core), magnetic
field and Doppler velocity. Methods: .We have observed solar
region NOAA 0644 on 2004 July 15 at Pic du Midi observatory with
the Multichannel Subtractive Double Pass (MSDP) operating mode and
analysed the circular polarization of the Na D1 589.6 nm spectral
line in terms of longitudinal magnetic field in 2D field of view (5.6
arcsec× 80 arcsec), during 41 mn at two altitudes 327 km and 170 km
in the photosphere. Results: .Our data analysis reveals that
all the concentrated magnetic features are associated with downward
motions and the magnetic field remains very stable during the 41 mn. At
different height 327 and 170 km, a clear depth effect is visible on
Doppler velocity but not in the magnetic field strength.

---------------------------------------------------------
Title: The Lyman Alpha Imaging-Monitor Experiment (LAIME) for
TESIS/CORONAS-PHOTON
Authors: Damé, L.; Koutchmy, S.; Kuzin, S.; Lamy, P.; Malherbe,
J. -M.; Noëns, J. -C.
2006cosp...36.3524D Altcode: 2006cosp.meet.3524D
LAIME the Lyman Alpha Imaging-Monitor Experiment is a remarkably
simple no mechanisms and compact 100x100x400 mm full Sun imager to be
flown with TESIS on the CORONAS-PHOTON mission launch expected before
mid-2008 As such it will be the only true chromospheric imager to be
flown in the next years supporting TESIS EUV-XUV imaging SDO and the
Belgian LYRA Lyman Alpha flux monitor on the ESA PROBA-2 microsatellite
launch expected in September 2007 We will give a short description
of this unique O60 mm aperture imaging telescope dedicated to the
investigating of the magnetic sources of solar variability in the UV and
chromospheric and coronal disruptive events rapid waves Moreton waves
disparitions brusques of prominences filaments eruptions and CMEs onset
The resolution pixel is 2 7 arcsec the field of view 1 4 solar radius
and the acquisition cadence could be as high as 1 image minute The back
thinned E2V CCD in the focal plane is using frame transfer to avoid
shutter and mechanisms Further more the double Lyman Alpha filtering
allows a 40 AA FWHM bandwidth and excellent rejection yet providing
a vacuum seal design of the telescope MgF2 entrance window Structural
stability of the telescope focal length 1 m is preserved by a 4-INVAR
bars design with Aluminium compensation in a large pm 10 o around 20 o

---------------------------------------------------------
Title: On the Disk Hα and Radio Observations of the 2003 October
28 Flare and Coronal Mass Ejection Event
Authors: Pick, Monique; Malherbe, Jean-Marie; Kerdraon, Alain; Maia,
Dalmiro Jorge Filipe
2005ApJ...631L..97P Altcode:
We present the evolution of the Hα and radio emissions seen by
the Meudon Hα telescope and the Nançay radioheliograph, which are
associated with the X17.2 flare and halo CME of 2003 October 28. The
remarkable characteristic of this event is its spatial extent that
it reached in a few minutes. At 164 MHz, radio images show that the
emission covers the whole disk of the Sun and extends as far as 1.8
Rsolar from the Sun's center. The radio emissions, the
Moreton wave seen in Hα, and the CME all show a similar temporal
and spatial development, and the three phenomena are likely to be
related. We show that multifrequency radio imaging observations obtained
at high cadence can accurately visualize the initial on-the-disk
development of fast halo CMEs and also provide physical parameters
such as their speed and angular expansion.

---------------------------------------------------------
Title: Research on a complex CME event including Hα, LASCO, radio
and MDI observations
Authors: Wang, S. J.; Maia, D.; Pick, M.; Aulanier, G.; Malherbe,
J. -M.; Delaboudinière, J. -P.
2005AdSpR..36.2273W Altcode:
We present our research on a fast and decelerating partial halo
coronal mass ejection (CME) event detected in multi-wavelengths
in the chromosphere and the corona on 14 October, 1999. The event
involved a whole complex active area which spanned more than 40°
of heliolongitude. It included a strong solar flare (XI/1N) and a
complex eruptive filament within an active region of the entire
complex. Especially, several radio sources were detected in the
decimetric range prior to the CME by the Nançay Radioheliograph
(NRH). A linear force-free field extrapolation of the Michelson Doppler
Imager (MDI) magnetogram was performed to calculate the magnetic
topology of the complex prior to the triggering of the event. The
presence of a coronal null point combined with the occurrence of two
distant and nearly simultaneous radio sources put strong arguments
in favor of the generalized breakout model for the triggering of the
eruption. The analysis of the subsequent development of the event
suggests that large interconnecting loops were ejected together with
the CME.

---------------------------------------------------------
Title: Second solar spectrum observed at the Pic-du-Midi: depth
probing of the turbulent magnetic field intensity in a quiet region.
Authors: Derouich, M.; Malherbe, J. M.; Bommier, V.; Landi
Degl'Innocenti, E.; Sahal-Bréchot, S.
2004sf2a.conf..113D Altcode: 2004sf2a.confE.346D
The installation of a new polarimeter at the Turret Dome of the
Pic-du-Midi has permitted new observations of the "second solar
spectrum" (which is the spectrum of the linear polarization observed
near the solar limb), having a spatial resolution. On 2003 October
25, we have observed a quiet region located at the East limb equator,
in the resonance line of neutral strontium at 4607 Å. The slit was
positioned perpendicular to the limb: recording various limb distances
provides a depth probing of the solar atmosphere. The intensity of
the turbulent magnetic field has been derived from the Hanle effect
interpretation, which is actually the only method for vectorial weak
field determination. The theoretical profiles to be compared to the
observed ones have been obtained by applying the atomic density matrix
formalism (Landi Degl'Innocenti E., Bommier V., &amp; Sahal-Bréchot
S., 1990). The various collisional coefficients have been computed by
applying semi-classical methods that are accurate to 20% or better:
the one from Seaton (1962) and Sahal-Bréchot (1969a, 1969b) for the
collisions with electrons, responsible for the inelastic transitions,
and the one developed by Anstee &amp; O'Mara (1991, 1995) for line
broadening computations, generalized to the collisional depolarization
by Derouich et al. (2003; see also Derouich, 2004), for the elastic
collisions with neutral hydrogen atoms. The results have been found in
full agreement with those previously obtained with THEMIS without any
spatial resolution (at 9 limb distances). With the spatial resolution
that we have now at the Pic-du-Midi (1 arcsec, 138 limb distances),
it appears that the turbulent magnetic field intensity does not vary
with depth, in the line formation region that ranges from ~200 to ~300
km above the tau5000=1 level.

---------------------------------------------------------
Title: High resolution solar magnetometry with the spectrograph of
the Pic du Midi Turret Dome
Authors: Malherbe, J. -M.; Roudier, Th.; Mein, P.; Moity, J.;
Muller, R.
2004A&A...427..745M Altcode: 2000astro.ph..3094R
We present the first results obtained with a new Ferroelectric Liquid
Crystal (FLC) polarimeter operating with the spectrograph of the Pic
du Midi Turret Dome, since September 2003. We observed the solar
granulation around active region NOAA 0459 with the Multichannel
Subtractive Double Pass (MSDP) operating mode and analysed the
circular polarization of the Na D1 589.6 nm spectral line in terms
of longitudinal magnetic fields in a 2D field of view (16× 142
arcsec). Image quality was fairly good and limited to 0.4 arcsec due to
the pixel sampling. This observation reveals the presence of magnetic
concentrations of several hundred Gauss which are mainly located in the
intergranular lanes. Data analysis performed at two different optical
depths (line core and line wings) also suggests that magnetic lines
are curved and diverge with increasing altitude.

---------------------------------------------------------
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: SOLARNET: the solution to the high resolution needs of
solar physics
Authors: Dame, L.; Clade, S.; Malherbe, J. M.
2004cosp...35.3583D Altcode: 2004cosp.meet.3583D
Encounter missions like the Solar Orbiter have high resolution
imaging goals in addition to the plasma measurements. If context,
arcsec imaging, might be possible and useful to interpret the plasma
observation, we will demonstrate that the thermal conditions near the
Sun will prevent to achieve any of the higher resolution goals even
by taking the most state-of-the-art solar telescope (carbon-carbon
structure, SiC mirrors, etc.). A far better solution to fulfill the
high resolution needs is the SOLARNET mission. SOLARNET is a medium
size high resolution solar physics mission proposed to CNES for a new
start in 2006 and a possible launch in 2010. Partnerships with Germany,
Belgium, China and India are under discussion. At the center of the
SOLARNET mission is a 3-telescopes interferometer of 1 meter baseline
capable to provide 50 times the best ever spatial resolution achieved
in Space with previous, current or even planned solar missions: 20
mas - 20 km on the Sun in the FUV. The interferometer is associated
to an on-axis subtractive double monochromator (imaging spectrograph)
capable of high spectral (0.01 nm) and high temporal resolutions (50
ms) on a field of view of 40 arcsec and over the FUV and UV spectral
domains (from 117.5 to 400 nm). This will allow to access process
scales of magnetic reconnection, dissipation, emerging flux and much
more, from the high chromosphere to the low corona with emphasis on
the transition zone where the magnetic confinement is expected to be
maximum. A whole new chapter of the physics of solar magnetic field
structuring and evolution will be opened. Launched by an Eurockot on a
high altitude sun-synchronous non-eclipsing orbit, SOLARNET will also
provide continuous observations at a sustained rate for Helioseismology
and solar cycle studies. We review the scientific program of SOLARNET
and its advantages (and complementarities) with an encounter type
mission (probe or orbiter), describe the interferometer concept and
design, present the first imaging results of the SOLARNET breadboard
obtained at Meudon Observatory this spring and give a short overview
of the mission aspects.

---------------------------------------------------------
Title: SOLARNET: a high resolution mission to complement the ILWS
programme
Authors: Dame, L.; Clade, S.; Malherbe, J. M.
2004cosp...35.3579D Altcode: 2004cosp.meet.3579D
SOLARNET is a medium size high resolution solar physics mission
proposed to CNES for a new start in 2006 and a possible launch in
2010. Partnerships with Germany, Belgium, China and India are under
discussion. At the center of the SOLARNET mission is a 3-telescopes
interferometer of 1 meter baseline capable to provide 50 times
the best ever spatial resolution achieved in Space with previous,
current or even planned solar missions: 20 mas - 20 km on the Sun in
the FUV. The interferometer is associated to an on-axis subtractive
double monochromator (imaging spectrograph) capable of high spectral
(0.01 nm) and high temporal resolutions (50 ms) on a field of view of
40 arcsec and over the FUV and UV spectral domains (from 117.5 to 400
nm). This will allow to access process scales of magnetic reconnection,
dissipation, emerging flux and much more, from the high chromosphere
to the low corona with emphasis on the transition zone where the
magnetic confinement is expected to be maximum. A whole new chapter
of the physics of solar magnetic field structuring and evolution
will be opened. The interferometer is complemented by several other
instruments providing larger field of view and higher temperature
(EUV-XUV coronal imaging) to define the context and extension of
the solar phenomena. Helioseismology, a strong asset of SOHO, is
also intended with both velocity and diameter measures, allowed by
a non-eclipsing Sun synchronous orbit. The SOLARNET interferometer
design results of an extensive laboratory demonstration program of
interferometric imaging of extended objects. It started 10 years ago
and culminates this year with the first interferometric observations
(images) of the Sun at Meudon Observatory at the "Grand Siderostat
de Foucault" with a complete 3 telescopes cophased interferometer
representative of SOLARNET. We will review the scientific program of
SOLARNET, describe the interferometer concept and design, present the
first solar imaging results of the breadboard and give a short overview
of the mission aspects.

---------------------------------------------------------
Title: Families of fragmenting granules and their relation to meso-
and supergranular flow fields
Authors: Roudier, Th.; Lignières, F.; Rieutord, M.; Brandt, P. N.;
Malherbe, J. M.
2003A&A...409..299R Altcode:
3D analysis (x,y,t) of the granular intensity field (11-hour time
sequence from the Swedish Vacuum Solar Telescope on La Palma, Canary
Islands), demonstrates that a significant fraction of the granules in
the photosphere are organized in the form of “Trees of Fragmenting
Granules" (TFGs). A TFG consists of a family of repeatedly splitting
granules, originating from a single granule at its beginning. A striking
result is that TFGs can live much longer (up to 8 h) than individual
granules (10 min). We find that 62% of the area covered by granules
belongs to TFGs of a lifetime &gt;1.5 h. When averaged in time, such
long-lived TFGs correspond to coherent diverging flows which may be
identified as mesogranules. We also find a correlation between the
network and the spatial distribution of TFGs.

---------------------------------------------------------
Title: High spatial resolution capabilities of Doppler measurements
with the Pic du Midi MSDP spectrograph
Authors: Roudier, Th.; Malherbe, J. M.; Mein, P.; Muller, R.; Coutard,
C.; Lafon, M.; Grimaud, F.
2003A&A...409..793R Altcode:
We analyse observations in the NaD1 line (lambda 5896 Å) obtained
with the MSDP spectrograph of the Turret Dome of the Pic du Midi
Observatory. Individual images reveal high spatial resolution and
the data reduction shows the high capabilities of the spectrograph
to get doppler measurements up to the limit of the resolution of the
refractor (0\farcs3). Dopplershifts are obtained in the middle and
high photosphere. The smallest granules 0\farcs4 show upward motions
in the middle photosphere.

---------------------------------------------------------
Title: Interpretation of a complex CME event: Coupling of scales in
multiple flux systems
Authors: Maia, D.; Aulanier, G.; Wang, S. J.; Pick, M.; Malherbe,
J. -M.; Delaboudinière, J. -P.
2003A&A...405..313M Altcode:
Using multi-wavelength observations, in particular in imagery, recorded
by SOHO/LASCO-MDI, Yohkoh/SXT, the Meudon spectroheliograph and the
Nançay radioheliograph, and performing a linear force-free field
extrapolation, we analyzed the triggering and the development of a
complex eruptive event in the chromosphere and in the corona. This
event included an X1 class flare and an eruptive filament within an
active region, but it also involved a whole active complex spanning over
40 degrees of heliolongitude. It resulted in a fast and decelerating
partial halo CME, associated with a Moreton wave and a complex series
of metric, decimetric and microwave radio bursts. The presence of a
coronal null point combined with the occurrence of two distant and
nearly simultaneous radio sources give strong arguments in favor of
the generalized breakout model for the triggering of the eruption. The
observations are consistent with the occurrence of magnetic reconnection
at the null point three minutes before the start of the eruption,
which is consistent with other observed CME precursors. The analysis
of the subsequent development of the event suggests that large
interconnecting loops were ejected together with the CME, and that
secondary reconnections at low altitude probably occurred remotely in
the active complex. Our results show that the triggering and evolution
of this complex CME involved multiple magnetic flux systems over a
large coronal volume surrounding the flare site, and that it resulted
from the coupling of scales from narrow reconnection current sheets
to very large inter active region magnetic connections.

---------------------------------------------------------
Title: Na I D1 Stokes V Asymmetries and Velocity Structure
Around Sunspots
Authors: Eibe, M. T.; Sánchez Almeida, J.; Mein, P.; Aulanier, G.;
Malherbe, J. M.
2003ASPC..307..374E Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Recurrence of fragmenting granules and their relation to meso-
and supergranular flow fields
Authors: Roudier, Th.; Lignières, F.; Rieutord, M.; Brandt, P. N.;
Malherbe, J. -M.
2003EAS.....9..371R Altcode:
The 3D analysis (x, y, t) of the granulation intensity field (11-hour
time sequence from Swedish Vacuum Solar Telescope on La Palma, Canary
Islands), demonstrated that the granules in the phostosphere are
organized in “Trees of Fragmenting Granules" (TFGs). A TFG consists of
a family of repeatedly splitting granules, issued from one granule at
its beginning. A striking result is that TFGs can live much longer (up
to 8h10) than individual granules (10 mn). When averaged in time, such
long-lived TFGs can be identified to the mesogranules. We also found
a correlation between the network and the spatial distribution of TFGs.

---------------------------------------------------------
Title: Photometry of rapidly evolving chromospheric bright points
in NOAA 9661 as observed by Themis and the Ondřejov multichannel
flare spectrograph
Authors: Kotrč, P.; Kupryakov, Yu. A.; Havlíčková, E.; Chambe,
G.; Malherbe, J. -M.
2002ESASP.506..669K Altcode: 2002svco.conf..669K; 2002ESPM...10..669K
Active region NOAA 9661 was observed on 13 October 2001 via narrow
band Hα filters at THEMIS and at the Ondřejov Multichannel Flare
Spectrograph both at a cadence of 25 images per second. Rapidly
evolving bright points located at various places close to the
sunspot were noticed several times during the day from 6 UT until 13
UT. Quite often their sudden appearance and disappearance seemed to
be strongly correlated. We expect these small areas to be magnetically
interconnected and possibly heated by injections of the same population
of electrons moving along the magnetic field lines. Light curves of
Hα emission integrated over individual bright areas were derived to
search for short-timescale variations and to analyze them, especially
concerning their correlations between different pairs of these areas. A
similar analysis was performed for sites in all the active region
for comparison and calibration purposes. Changes in correlations
are discussed.

---------------------------------------------------------
Title: Vertical structure of sunspots from THEMIS observations
Authors: Eibe, M. T.; Aulanier, G.; Faurobert, M.; Mein, P.; Malherbe,
J. M.
2002A&A...381..290E Altcode:
We have analysed two-dimensional spectro-polarimetric data taken
with the MSDP observing mode of THEMIS in the Na I D1
line to investigate the height variation of the magnetic field
in sunspot umbrae. From the Zeeman-induced circular polarization
measured at individual MSDP channels within the line profile, maps of
the longitudinal magnetic field have been computed. A method based
on Response Functions has been developed to estimate the depth in
the atmosphere at which the Zeeman measurements are originated,
thus providing the line-of-sight field at different altitudes
in the photosphere. The magnetogram corresponding to the deepest
level has served as a boundary condition to perform the potential
field extrapolation into the corona. We have found that the spatial
distribution of vertical field gradient contours predicted from
extrapolation is in qualitatively good agreement with that inferred from
observations. Quantitatively, however, the longitudinal field gradients
obtained with both methods differ about one order of magnitude, being
larger for observations. The origin of this discrepancy has been
discussed with respect to possible observation biases, as well as to
idealizations used for field extrapolation. This is a crucial problem
to be addressed in future work, and may have important implications
for the physics of how the magnetic field evolves through sunspots
and how the flux is distributed in the corona.

---------------------------------------------------------
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: Temporal height properties of the exploding granules
Authors: Roudier, Th.; Eibe, M. T.; Malherbe, J. M.; Rieutord, M.;
Mein, P.; Mein, N.; Faurobert, M.
2001A&A...368..652R Altcode:
Based on time series of 2D MSDP spectrograms, taken at the Turret Dome
in Pic du Midi, we present the temporal evolution of exploding granules
in intensity and Doppler velocity through the solar photosphere. We
describe the penetration of exploding granules in the solar photosphere
during their lifes and the related phenomena like the “Bright Plumes”
located in the downflowing plasma just on the edge of the granule. We
suggest a possible scenario of the exploding granule evolution in the
solar photosphere.

---------------------------------------------------------
Title: Emergence of a U-loop - sub-photospheric link between solar
active regions
Authors: van Driel-Gesztelyi, L.; Malherbe, J. -M.; Démoulin, P.
2000A&A...364..845V Altcode:
Using SOHO/MDI magnetic maps we present the first direct observational
evidence for the emergence of a U-loop in the solar photosphere. We
show that two active regions (ARs), i.e. two adjacent Omega -loops,
which were emerging at the same time at the same solar latitude,
about 150000 km distance in longitude from each other, emerged from
at least partially the same toroidal flux strand, and we bring five
independent arguments to prove this assertion. The opposite polarity
legs of the two Omega -loops were connected below the photosphere by a
U-shaped loop. Following the emergence of the Omega -loops, the U-loop
started emerging, manifested by the fast proper motion of the leading
spots of the eastern (smaller) active region, which, after forming an
elongated channel, collided with the following spots of the westerly
AR and started cancelling with them. The full cancellation could not be
followed because the ARs rotated out of sight. The total magnetic flux
of the two ARs was unequal, the flux in the smaller AR was a quarter of
that of the larger one. We propose scenarios for the formation of such
a U-loop and discuss the implications of the confirmed existence of
U-loops for the solution of such puzzles as the in-situ disappearance
of magnetic flux from active regions, active nests and the formation
of inter-AR filaments.

---------------------------------------------------------
Title: On mesogranulation, network formation and supergranulation
Authors: Rieutord, M.; Roudier, T.; Malherbe, J. M.; Rincon, F.
2000A&A...357.1063R Altcode:
We present arguments which show that in all likelihood mesogranulation
is not a true scale of solar convection but the combination of
the effects of both highly energetic granules, which give birth to
strong positive divergences (SPDs) among which we find exploders, and
averaging effects of data processing. The important role played by SPDs
in horizontal velocity fields appears in the spectra of these fields
where the scale ~ 4 Mm is most energetic; we illustrate the effect
of averaging with a one-dimensional toy model which shows how two
independent non-moving (but evolving) structures can be transformed
into a single moving structure when time and space resolution are
degraded. The role of SPDs in the formation of the photospheric network
is shown by computing the advection of floating corks by the granular
flow. The coincidence of the network bright points distribution and
that of the corks is remarkable. We conclude with the possibility that
supergranulation is not a proper scale of convection but the result
of a large-scale instability of the granular flow, which manifests
itself through a correlation of the flows generated by SPDs.

---------------------------------------------------------
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: 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: Determination of horizontal velocity fields at the sun's
surface with high spatial and temporal resolution
Authors: Roudier, Th.; Rieutord, M.; Malherbe, J. M.; Vigneau, J.
1999A&A...349..301R Altcode:
We analyse the two algorithms which have been used in the past few years
to determine the horizontal flow fields at the Sun's surface, namely
the Local Correlation Tracking (LCT) of L. November and the Feature
Tracking of L. Strous. Analysing the systematic errors introduced by
LCT, we show that these errors come from the averaging processes. More
precisely, they arise from the interpolating step of the algorithm:
granules' motions determine the flow on an irregular grid which is
then interpolated to derive quantities such as horizontal divergence
or vertical vorticity. Interpolation is therefore a crucial step since
mesoscale structures have mainly been studied through divergences and
vorticities. We conclude that a reliable algorithm should be based
on the tracking of coherent structures, like granules, since they are
representative of the fluid motion, and should contain an interpolator
which keeps track of the errors introduced either by location of the
data (the shape of the irregular grid) or by the noise in the data.

---------------------------------------------------------
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: Internal intermittency on the Sun surface?
Authors: Roudier, T.; Rieutord, M.; Malherbe, J. M.; Vigneau, J.
1999joso.proc..197R Altcode:
An improved version of LCT and FT is presented and used to determine
high spatial and temporal resolution horizontal flow fields at the
Sun's surface. The granule diplacements and group evolution can be
followed. The horizontal flow fields calculated by these methods show
a structured flow at mean scale (4 to 8 arcsec) by a group of granules
which is probably related to the local intermittency.

---------------------------------------------------------
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: 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: Surveillance et prévision de l'activité solaire à
l'Observatoire de Paris.
Authors: Malherbe, J. -M.
1998JAF....56....5M Altcode:
No abstract at ADS

---------------------------------------------------------
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: Solar mesogranule lifetime measurements
Authors: Roudier, Th.; Malherbe, J. M.; Vigneau, J.; Pfeiffer, B.
1998A&A...330.1136R Altcode:
{ We present a study in which the solar lifetime of mesocells (4-10
arcsec) was determined from a long time sequence (6h 40min) obtained
at the Pic du Midi Observatory. The mesocell detection was performed
by local correlation tracking, using various spatial and temporal
windows. The histograms derived from the visual measurements reveal
that mesoscale lifetime is between 10min and 160min, with peaked
distributions around 30-40min. The indirect method for lifetime
estimation using a correlation coefficient, gives a mesocale lifetime
from 16 to 185min depending on the temporal window and the methods
used. The proper motions of the long-living mesocells are found to be
random with respect to the superganule flows, with the peak distribution
of horizontal velocities at 0.5km/s. The results of this mesocell
lifetime determination method are smaller by a factor of 2 to 5 with
respect to the previous results. This difference could be attributed
to the mesocell definition, the method of measurement or the different
location of the mesocell field of view in the supergranular network. }

---------------------------------------------------------
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: 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: 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: 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: 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: Flare Multi-Line 2D-SPECTROSCOPY
Authors: Mein, P.; Mein, N.; Malherbe, J. -M.; Heinzel, P.; Kneer,
F.; von Uexkull, M.; Staiger, J.
1997SoPh..172..161M Altcode: 1997ESPM....8..161M
A small flare was observed at the Teide Observatory on October 5,
1994. Simultaneous data were obtained at the German Vacuum Tower
Telescope (VTT) with the MSDP spectrograph providing high-resolution
imaging spectroscopy in two chromospheric lines, and the Gregory Coudé
Telescope (GCT) providing information about the magnetic field. Basic
flare characteristics are:

---------------------------------------------------------
Title: Intergranular plumes and formation of network bright points.
Authors: Roudier, T.; Malherbe, J. M.; November, L.; Vigneau, J.;
Coupinot, G.; Lafon, M.; Muller, R.
1997A&A...320..605R Altcode:
We discuss the temporal evolution of the photospheric intergranular
lanes using a 1 hour time sequence of white-light images of solar
granulation. The time series was obtained with the 50 cm refractor at
the turret dome of the Pic du Midi Observatory. Analysis reveals the
existence of singularities in the intergranular lanes that we call
“intergranular holes”. Intergranular holes, which have diameters
between 0.24arcsec and 0.45arcsec, are continuously visible for more
than 45 minutes. The holes appear to be systematically distributed at
the periphery of mesogranular and supergranular cells. Our study reveals
the formation of bright points (BPs) in 4 out of 14 cases studied very
close to the intergranular holes, suggesting that intergranular holes
may be the locations where magnetic flux tubes are formed.

---------------------------------------------------------
Title: 3-D reconnection related to new emerging flux
Authors: Schmeider, B.; Démoulin, P.; Aulanier, G.; Malherbe, J. M.;
van Driel-Gesztelyi, L.; Mandrini, C. H.; Roudier, T.; Nitta, N.;
Harra-Murnion, L. K.
1997AdSpR..19.1871S Altcode:
We present evidences that emergence of new flux in the lower
atmosphere leads to magnetic reconnection of field lines. In a
first phase the phenomenon is observed in the chromosphere by the
formation of dark filaments (arch filament system) which are overlaid
by bright loops visible in soft X-rays. Different types of event appear
according to the magnetic field configuration and the amount of energy
involved. 3-D modelling of the photospheric magnetic field provides a
new tool for understanding reconnection in real configurations. The
observed chromospheric and coronal loops are good diagnostics for
the modelling. We document our statement by examples obtained during
coordinated campaigns with the Hα Multichannel Subtractive Double
Pass spectrographs-MSDP (Pic du Midi and Tenerife) and the Yohkoh
instruments.

---------------------------------------------------------
Title: BASS 2000 THEMIS Archive
Authors: Roudier, Th.; Malherbe, J. M.
1997ASPC..118..377R Altcode: 1997fasp.conf..377R
No abstract at ADS

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

---------------------------------------------------------
Title: Spatial relation between the 5-minute oscillations and
granulation patterns.
Authors: Espagnet, O.; Muller, R.; Roudier, T.; Mein, P.; Mein, N.;
Malherbe, J. M.
1996A&A...313..297E Altcode:
A white light, high resolution movie of the quiet photosphere has been
used to study the spatial relation between the solar granulation and
the 5-min oscillations of high degree mode (small spatial scale). The
granular and oscillatory brightness components have been separated with
the help of a specific filter, in the k-ω diagram. The surface of the
Sun appears to be covered with adjacent oscillating cells of apparent
size 2" (1500km) to 3" (2000km). Some cells are noticeable by their
amplitude which is much larger than average. These strong oscillations
usually appear in expanding intergranular spaces. Our observations
suggest that the 5-min oscillations are stochastically generated by
turbulent convection. However, the most energetic oscillations occur
in downflows only, well separated of each other in time and space.

---------------------------------------------------------
Title: Cloud model with variable source function for solar Hα
structures.
Authors: Mein, N.; Mein, P.; Heinzel, P.; Vial, J. -C.; Malherbe,
J. M.; Staiger, J.
1996A&A...309..275M Altcode:
The "cloud model" used to derive the physical parameters of solar
chromospheric features is extended to the cases of non-constant
source function and of velocity gradients. This model assumes a given
relationship between the source function and the opacity of the cloud
which is derived from non-LTE modelling. An algorithm using 4 points
of the Halpha_ profile is proposed to derive the optical
thickness, the line-of-sight velocity and the dopplerwidth. The
results are compared with a 5-points inversion which does not use the
given relationship between source function and opacity. Effects of the
uncertainty about the radiation coming from the underlying chromosphere,
as well as effects of data noise, are discussed. The inversion method
is illustrated by some examples of observed profiles obtained with
the MSDP spectrograph of the VTT telescope (Teide Observatory).

---------------------------------------------------------
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: High resolution flare observations with multi-line imaging
spectroscopy.
Authors: Mein, P.; Heinzel, P.; Malherbe, J. -M.; Staiger, J.
1996joso.proc...68M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Server of the Observatoire de Paris-Meudon-Nançay
Authors: Arenou, F.; Chevalier, J. M.; Dubost, K.; Huille, S.;
Laurent, C.; Letourneur, L.; Malherbe, J. M.; Schneider, J.; Spite,
F.; Spite, M.
1995VA.....39...97A Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The Sun.
Authors: Martres, M. J.; Boyer, R.; Costard, F.; Malherbe, J. M.;
Olivieri, G.
1994oga..book....1M Altcode:
Contents: 1. Introduction. 2. The changing appearance of the Sun. 3. How
to observe the Sun. 4. Amateur observing programmes. 5. Monochromatic
observation of the Sun. 6. Conclusion.

---------------------------------------------------------
Title: Janssen et l'Observatoire astronomique du mont Blanc.
Authors: Malherbe, J. -M.
1993LAstr.107..278M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Linear force-free magnetic field around quiescent solar
prominences computed from observable boundary conditions
Authors: Demoulin, P.; Raadu, M. A.; Malherbe, J. M.
1992A&A...257..278D Altcode:
The magnetic support of solar prominences in two-dimensional linear
force-free fields is analyzed. The prominence was modeled as a
vertical current sheet with mass in equilibrium between gravity and
magnetic forces. A finite difference numerical technique was used
which incorporates both vertical photospheric and horizontal prominence
magnetic field observations as boundary conditions. The mixed-boundary
value problem is described and the current singularity generally present
is eliminated by a modification of the initial boundary condition. Using
the linear force-free hypothesis the bipolar and quadripolar regions
were found to be associated with normal and inverse prominence polarity
respectively. An increase of magnetic shear decreases the mass supported
for a given vertical dependence of the field component orthogonal to
the prominence.

---------------------------------------------------------
Title: La fondation de l'observatoire et les débuts de l'astronomie
au Pic du Midi (1852 - 1947). Dernière partie: Le règne de la
coupole Baillaud.
Authors: Malherbe, J. -M.; Coutard, C.; Roudier, T.
1991LAstr.105R...1M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: La fondation de l'observatoire et les débuts de l'astronomie
au Pic du Midi (1852 - 1947). Deuxième partie: L'introduction
de l'astronomie.
Authors: Malherbe, J. -M.; Coutard, C.; Roudier, T.
1991LAstr.105Q...1M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: A numerical simulation of magnetic reconnection and radiative
cooling in line-tied current sheets
Authors: Forbes, T. G.; Malherbe, J. M.
1991SoPh..135..361F Altcode:
We have used the radiative MHD equations for an optically thin
plasma to carry out a numerical experiment related to the formation of
`post'-flare loops. The numerical experiment starts with a current sheet
that is in mechanical and thermal equilibrium, but which is unstable
to both tearing-mode and thermal-condensation instabilities. The
current sheet is line-tied at one end to a photospheric-like boundary
and evolves asymmetrically. The effects of thermal conduction,
resistivity variation, and gravity are ignored. In general, we find that
reconnection in the nonlinear stage of the tearing-mode instability can
strongly affect the onset of condensations unless the radiative cooling
time scale is much smaller than the tearing-mode time scale. When the
ambient plasma β is less than 0.2, the reconnection enters a regime
where the outflow from the reconnection region is supermagnetosonic with
respect to the fast-mode wave speed. In the supermagnetosonic regime
the most rapidly condensing regions occur downstream of a fast-mode
shock that forms where the outflow impinges on closed loops attached
to the photospheric-like boundary. A similar shock-induced condensation
might occur during the formation of `post'-flare loops.

---------------------------------------------------------
Title: La fondation de l'observatoire et les débuts de l'astronomie
au Pic du Midi (1852 - 1947). Introduction. Première partie: La
fondation de l'observatoire.
Authors: Malherbe, J. -M.; Coutard, C.; Roudier, T.
1991LAstr.105....6M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Dynamics of the solar granulation. II - Statistical analysis:
Power spectra, coherence, phase
Authors: Roudier, T.; Vigneau, J.; Espagnet, O.; Muller, R.; Mein,
P.; Malherbe, J. M.
1991A&A...248..245R Altcode:
The solar granulation is analyzed statistically by the computation
of coherence, phase, and power spectra using data provided by the
Multichannel Subtractive Double Pass spectrograph of the Pic du Midi
Observatory. The main result of the analysis is that the velocity
power spectrum of the granulation changes in shape at 3 arcsec: the raw
spectrum features a slope discontinuity; the corrected spectra have a
power maximum at 3 arcsec. Between 3 arcsec and the resolution limit
(0.8 arcsec), the power decreases almost linearly, with a slope close
to -5/3, consistent with the Kolmogorov power law for a turbulent
energy cascade.

---------------------------------------------------------
Title: Dynamics of solar granulation. I - Processing of MSDP spectra
Authors: Roudier, T.; Vigneau, J.; Mein, P.; Malherbe, J. M.; Coutard,
C.; Hellier, R.; Muller, R.
1991A&A...248..237R Altcode:
High resolution (about 0.5 arcsec) 2D spectra have been obtained
with the Multichannel Subtractive Double Pass spectrograph of the Pic
du Midi Observatory in a quiet region at the solar disk center. The
adapted image processing which provides 2D intensity and velocity maps
of the solar granulation, at two intensity levels of the line NaD2,
is described. A quantitative evaluation of the spatial resolution is
determined both for the intensity and velocity granulation fields.

---------------------------------------------------------
Title: Results from high resolution solar images and spectra obtained
at the Pic du Midi Observatory (1986-1990)
Authors: Roudier, Th.; Muller, R.; Vigneau, J.; Auffret, H.; Espagnet,
O.; Simon, G. W.; Title, A. M.; Frank, Z.; Shine, R. A.; Tarbell,
T. D.; Mein, P.; Malherbe, J. M.
1991AdSpR..11e.205R Altcode: 1991AdSpR..11..205R
We present an overview of our recent results about solar granulation and
mesogranulation, obtained with Pic du Midi observations. These results
were obtained during 1986-1990 using image and spectrographic analysis
of high spatial resolution data. The study of the solar granulation,
with 2 Dim. “Multichannel Subtractive Double Pass” (M.S.D.P.) spectra,
shows a clear change of the dynamical regime at 3” (⋍ 2200 km)
of the photospheric velocity field when oscillatory components are
filtered out. A three hour movie obtained on film at Pic du Midi
Observatory and analyzed at the Lockheed Research Laboratory and the
National Solar Observatory (Sacramento Peak) was used to calculate
the horizontal flow pattern. The mean lifetime of the diverging areas
related to mesogranulation is estimated at 3 hours; these diverging
areas are swept by the supergranulation flow towards the supergranule
boundary with a mean speed of 0.4 km/s.

---------------------------------------------------------
Title: L'Observatoire des Rayons Cosmiques à l'Aiguille du Midi.
Authors: Malherbe, J. -M.
1990LAstr.104..243M Altcode:
No abstract at ADS

---------------------------------------------------------
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: The Formation of Flare Loops by Magnetic Reconnection and
Chromospheric Ablation
Authors: Forbes, T. G.; Malherbe, J. M.; Priest, E. R.
1989SoPh..120..285F Altcode:
Slow-mode shocks produced by reconnection in the corona can provide the
thermal energy necessary to sustain flare loops for many hours. These
slow shocks have a complex structure because strong thermal conduction
along field lines dissociates the shocks into conduction fronts and
isothermal subshocks. Heat conducted along field lines mapping from
the subshocks to the chromosphere ablates chromospheric plasma and
thereby creates the hot flare loops and associated flare ribbons. Here
we combine a non-coplanar compressible reconnection theory with simple
scaling arguments for ablation and radiative cooling, and predict
average properties of hot and cool flare loops as a function of the
coronal vector magnetic field. For a coronal field strength of 100 G the
temperature of the hot flare loops decreases from 1.2 × 107
K to 4.0 × 106 K as the component of the coronal magnetic
field perpendicular to the plane of the loops increases from 0% to 86%
of the total field. When the perpendicular component exceeds 86% of
the total field or when the altitude of the reconnection site exceeds
106km, flare loops no longer occur. Shock enhanced radiative
cooling triggers the formation of cool Hα flare loops with predicted
densities of ≈ 1013 cm−3, and a small gap
of ≈ 103 km is predicted to exist between the footpoints
of the cool flare loops and the inner edges of the flare ribbons.

---------------------------------------------------------
Title: Granulation velocity field: latest results from Pic-du-Midi -
processing of MSDP data
Authors: Mein, P.; Roudier, Th.; Vigneau, J.; Muller, R.; Malherbe,
J. M.; Contard, C.; Hellier, R.
1989hsrs.conf..521M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: The magnetic field around quiescent solar prominences computed
from observational boundary conditions
Authors: Demoulin, P.; Malherbe, J. M.; Priest, E. R.
1989A&A...211..428D Altcode:
A generalization of Anzer's model (1972) for quiescent prominence
support is presented. The coronal field is assumed to be current-free
except inside the prominence where currents support dense material
against gravity. The prominence is taken to be an infinitely thin
current sheet of finite extent along the vertical axis. The hypothesis
of two-dimensional fields allows the use of complex functions to
solve the mixed boundary problem which is defined by the observed
vertical field in the photosphere and the horizontal magnetic field
in the prominence. These boundary conditions are not sufficient to
determine a unique solution for the magnetic field. The indeterminacy
is decreased by physical considerations, and some models for Normal
(N) and Inverse (I) configurations are presented. In both cases it
is possible to find field configurations which can support the fintie
prominence against gravity.

---------------------------------------------------------
Title: Protuberanzen und Beobachtungsprogramme.
Authors: Malherbe, J. -M.; Martres, M. -J.; Vial, J. -C.
1989Sonne..13....8M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Oscillations of the sun's chromosphere. V - Importance of
network dynamics for chromospheric heating
Authors: von Uexkuell, M.; Kneer, F.; Malherbe, J. M.; Mein, P.
1989A&A...208..290V Altcode:
A 64-min time sequence of disk center H-alpha spectrograms taken
with the MSDP spectrograph at the Observatoire du Pic du Midi
is analyzed. This type of spectrograph allows spectroscopy of a
two-dimensional field of view. From the H-alpha line profiles at each
pixel, line-shift and minimum intensity fluctuation are determined as
functions of spatial and temporal coordinates. A frequency analysis
with standard Fourier techniques is performed. It is confirmed that
in the interior of the chromospheric network cells the oscillatory
behavior dominates, whereas at the boundaries one generally finds random
motions on scales of 2-10 arcsec. The random behavior of the H-alpha
structures outlines the permanent rearrangement of the magnetic field
lines pushed around by the subphotospheric granular flow.

---------------------------------------------------------
Title: The formation of solar prominences
Authors: Malherbe, J. -M.
1989ASSL..150..115M Altcode: 1988dsqs.work..115M; 1989dsqs.work..115M
Recent progress in the understanding of the formation of quiescent
solar prominences is summarized, from both an observational and
theoretical point of view. It is now well known that the mass of a
quiescent prominence (seen in emission at the solar limb) or a filament
(generally seen in absorption above the disk) is an appreciable part
of the mass of the entire corona (roughly one tenth or more), which
makes it difficult to form these structures by coronal condensation
alone. Hence possible mechanisms proposed recently to account for
their formation are divided into two categories, namely, injection
(of the chromospheric material into the corona by siphon flows) and
condensation (of the coronal plasma itself).

---------------------------------------------------------
Title: Particles and energy transport in the solar atmosphere during
solar flares.
Authors: Heristchi, D.; Raadu, M. A.; Vial, J. -C.; Malherbe, J. -M.
1989sasf.confP.321H Altcode: 1988sasf.conf..321H; 1989IAUCo.104P.321H
The proposed model of particle transport in the solar atmosphere
during flares consists in a low density plasmoid originating
deep in the atmosphere and rising under magnetic and buoyancy
forces. Confined particles are selectively released during the ascent
and their interaction with the solar atmosphere produces X and γ
bremsstrahlung. The characteristics of high energy particles released
in the interplanetary medium are found to agree with observations.

---------------------------------------------------------
Title: Quelques phénomènes de l'optique atmosphérique.
Authors: Malherbe, Jean-Marie
1988LAstr.102..351M Altcode:
Atmospheric optical effects resulting from the interaction between
extended light sources (the sun and moon) or point sources (planets
and bright stars) and the heterogeneous atmosphere are discussed. It
is noted that refraction is responsible for such phenomena as the
oblateness of the sun and moon when rising or setting, mirages (the
curving of light rays near the ground), nocturnal scintillation,
rainbows, and halos. The diffusion of light by particles in the
atmosphere is responsible for the blue color of the sky during the
day and the red color of the sky at sunrise and sunset. Diffractive
phenomena discussed include the colored ring surrounding the sun or
moon when viewed through fog and the iridescent Bishop's ring.

---------------------------------------------------------
Title: Two Solar Observation Programmes
Authors: Marthes, M. J.; Malherbe, J. M.; Vial, J.
1988scaa.conf..175M Altcode: 1988IAUCo..98..175M
No abstract at ADS

---------------------------------------------------------
Title: The formation of solar prominences.
Authors: Malherbe, J. M.
1988dssp.conf...77M Altcode:
Recent progress in the understanding of the formation of quiescent solar
prominences is summarized in this paper, from both an observational
and theoretical point of view. The first part as a review of recent
observations; the second one presents main instabilities involved in
prominence formation, and is a summary of first attempts to model this
complex phenomenon. The third part investigates filament formation by
chromospheric injection, while the fourth one describes recent models
of coronal condensation.

---------------------------------------------------------
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: 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: Contribution a l'etude magneto thermo dynamique des
protuberances solaires
Authors: Malherbe, Jean-Marie
1987PhDT.......217M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Inversion of line profile disturbances - A nonlinear method
applied to solar CaII lines
Authors: Mein, P.; Mein, N.; Malherbe, J. M.; Dame, L.
1987A&A...177..283M Altcode:
Thermodynamical disturbances in the solar atmosphere can be deduced from
observations of line profiles. The authors propose a non-linear method
based on Fourier analysis: each profile is converted into a "double
profile" for a fast convergence of Fourier expansions. Disturbances
of Fourier coefficients are connected theoretically with physical
disturbances by second order developments. Temperature and velocity
fluctuations are derived from a least square inversion of these
developments. The authors apply this method to a time sequence of
high resolution profiles of the Ca II 3968 Å line. The accuracy of
the results is discussed. The enhanced blue peaks occurring in the
asymmetric profiles are interpreted as downward velocity gradients,
associated with temperature excesses.

---------------------------------------------------------
Title: Protubérances solaires et programmes d'observation.
Authors: Malherbe, Jean-Marie; Martres, Marie-Josephe; Vial,
Jean-Claude
1987LAstr.101..321M Altcode:
The observed characteristics of solar prominences are reviewed, and
models for the formation of filaments and for the magnetic structure
of protuberances are discussed. Data suggest that coronal filaments
are formed either by the pumping of chromospheric matter or by
condensation of the coronal plasma itself by thermal instability. The
class of Kippenhahn-Schluter models involve magnetic rings which are
bent under the influence of gravity, and the class of Kuperus-Raadu
models place prominences above a certain neutral point. Observations
of filamentary velocity fields indicate that the magnetic support of
the condensation is in quasi-static evolution. Three proposed areas
of study of prominences, the connections and exchanges of matter at
great distances, eruptive prominences, and the sudden disappearance
of prominences, are discussed.

---------------------------------------------------------
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: Dynamics of the solar granulation.
Authors: Muller, R.; Roudier, Th.; Malherbe, J. M.; Mein, P.
1987PAICz..66..175M Altcode: 1987eram....1..175M
In order to understand the origin of the solar granulation, convective
or turbulent, in this paper the authors report results about the
intensity-velocity correlation and the energy power spectrum derived
from the Doppler shifts measurement on two-dimensional high resolution
spectrograms.

---------------------------------------------------------
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: The Formation of Solar Prominences
Authors: Malherbe, J. M.
1987dssp.work...77M Altcode: 1987ASSL..150...77M
No abstract at ADS

---------------------------------------------------------
Title: Les observatoires du Mont-Blanc en 1900.
Authors: Malherbe, J. -M.
1987LAstr.101..115M Altcode:
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: 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: On the thermal durability of solar prominences, or how to
evaporate aprominence?
Authors: Malherbe, J. M.; Forbes, T. G.
1986NASCP2442..225M Altcode: 1986copp.nasa..225M
The authors investigate the thermal disappearance of solar prominences
under strong perturbations due to wave heating, Ohmic heating, viscous
heating or conduction. Specifically, they calculate how large a thermal
perturbation is needed to destroy a stable thermal equilibrium,
and find that the prominence plasma appears to be thermally very
rugged. Its cold equilibrium may most likely be destroyed by either
strong magnetic heating or conduction in a range of parameters which
is relevant to flares.

---------------------------------------------------------
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: Can prominences form in current sheets?
Authors: Malherbe, J. M.; Forbes, T. G.
1986NASCP2442...33M Altcode: 1986copp.nasa...33M
Two-dimensional numerical simulations of the formation of cold
condensations in a vertical current sheet have been performed using the
radiative, resistive MHD equations with line-tied boundary conditions
at one end of the sheet. Prominence-like condensations are observed
to appear above and below an X-line produced by the onset of the
tearing-mode instability. Cooling in the sheet is initiated by Ohmic
decay, with the densest condensations occurring in the region downstream
of a fast-mode shock. This shock, which is due to the line-tied boundary
conditions, terminates one of the two supermagnetosonic reconnection
jets that develop when the tearing is fully developed. This paper
emphasizes the condensation properties of shock waves, which may trigger
or considerably enhance the conditions for thermal condensations.

---------------------------------------------------------
Title: Transition zone effects on thermal non-equilibrium and plasma
condensation in solar coronal loops
Authors: She, Z. S.; Malherbe, J. M.; Raadu, M. A.
1986A&A...164..364S Altcode:
The quasi-static thermal structure of arches or loops in the solar
corona is investigated analytically, integrating the classical HD
equations numerically along the magnetic-field lines and taking the
effect of the transition region joining the arches to the chromosphere
into account. Expressions for determining the mechanical heating rate
and summit temperature from the footpoint chromospheric density and
the loop length are obtained, and the implications of a solution with
a cold dense mass sheet at the arcade summit are explored.

---------------------------------------------------------
Title: A Shock Condensation Mechanism for Loop Prominences
Authors: Forbes, T. G.; Malherbe, J. M.
1986ApJ...302L..67F Altcode:
Self-consistent, numerical solutions of the resistive MHD equations
in two dimensions show that a quasi-stationary, fast-mode shock is a
characteristic feature of the reconnection dynamics of the Kopp-Pneuman
model of two-ribbon flares. A preliminary analysis of the effects of
radiative cooling and thermal conduction suggests that the fast shock
can help trigger a thermal condensation (i.e., a loop prominence)
if the reconnecting magnetic fields are sufficiently strong.

---------------------------------------------------------
Title: Numerical Image Processing Applied to the Solar Corona
Authors: Malherbe, J. M.; Noens, J. C.; Roudier, Th.
1986SoPh..103..393M Altcode:
Numerical data processing is applied to the high-resolution images-of
the solar corona obtained with the 20 cm coronagraph of the Pic du
Midi observatory. Two complementary methods are proposed to solve
some classical difficulties usually met in the morphological analysis
of the solar corona, namely the brightness gradient in the inner and
medium corona, the low contrast of numerous emissive regions and the
superimposition along the line of sight of different structures. The
methods which are described in this paper may help to resolve the
complex coronal active regions into fine structures which is now
necessary to interpret all observed corona data.

---------------------------------------------------------
Title: A reconnection mechanism for coronal condensations in
two-ribbon flares.
Authors: Forbes, T. G.; Malherbe, J. M.
1986lasf.conf..443F Altcode: 1986lasf.symp..443F
During the last few years the authors have used a series of
self-consistent two-dimensional, MHD calculations to explore the
reconnection dynamics implied by the two-ribbon flare model of Kopp
and Pneuman (1976). The calculations show, that in addition to the
standard slow-mode MHD shocks generated by reconnection, there also
exists a standing fast-mode MHD shock. Because of thermal conduction,
the slow shocks generate an evaporative upflow of chromospheric plasma
into the reconnection region. Analysis of the effects of radiative and
conductive cooling suggests that at least some of this evaporated plasma
will undergo thermal condensation when it passes through the fast shock.

---------------------------------------------------------
Title: THEMIS: un projet solaire national pour une recherche
internationale.
Authors: Rayrolle, J.; Mein, P.; Malherbe, J. -M.
1986JAF....28....6R Altcode:
No abstract at ADS

---------------------------------------------------------
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: Inversion of Chromospheric Line Profiles
Authors: Mein, P.; Mein, N.; Malherbe, J. M.
1985tphr.conf..303M Altcode:
No abstract at ADS

---------------------------------------------------------
Title: Mass Motions in Hα Absorbing Structures of the Solar
Chromosphere
Authors: Mein, P.; Malherbe, J. M.; Mein, N.; Mouradian, Z.;
Schmeider, B.
1985tphr.conf..316M Altcode:
No abstract at ADS

---------------------------------------------------------
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.

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Title: Inversion of chromospheric line profiles.
Authors: Mein, P.; Mein, N.; Malherbe, J. M.
1985MPARp.212..303M Altcode:
Because of the large amount of high resolution data which becomes
available now from solar observations, fast codes are urgently needed in
order to interpret disturbed line profiles. The authors present briefly
two kinds of algorithms usable in the case of chromospheric lines.

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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.

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Title: Atmospheric structure deduced from disturbed line profiles -
application to Ca II lines.
Authors: Mein, N.; Mein, P.; Malherbe, J. -M.; Dame, L.; Dumont, S.
1985cdm..proc..167M Altcode:
A new method is described in order to derive physical quantities
(temperature, pressure, radial velocities) from the observation of
disturbed line profiles. The authors suggest a method of Fourier
analysis with double profiles and a non linear expansion of the
coefficient of the Fourier terms. An application to a sequence of H -
Ca II line is attempted. The method seems a powerful tool allowing
the determination of at least 4 physical quantities simultaneously.

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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.

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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.

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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

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Title: Magnetic instabilities in solar filaments: models of twisting
motionsand ejecta.
Authors: Schmeider, B.; Malherbe, J. M.; Raadu, M.
1984ESASP.220..273S Altcode: 1984ESPM....4..273S
Time sequences of two destabilized solar filaments were derived using
a spectrograph operated in H alpha. The opposite directed velocities
observed in the first filament are interpreted in terms of a twisted
magnetic flux rope model. The sudden disappearance of the second
filament corresponds to high velocity plasmoids confined in magnetic
field lines and then ejected.

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Title: A numerical simulation of the formation of solar prominences.
Authors: Malherbe, J. M.; Forbes, T. G.; Priest, E. R.
1984ESASP.220..119M Altcode: 1984ESPM....4..119M
The radiative-resistive MHD equations are numerically solved in
two-dimensions for a magnetic field configuration that starts with
a vertical current sheet which is line-tied at its base and is in
mechanical, but not radiative, equilibrium. The aim of the present
study is to determine whether this initial configuration can achieve
a prominence-like equilibrium in the presence of magnetic reconnection
and tearing in the current-sheet.

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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.

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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.

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Title: Intensity oscillations in the calcium - K line
Authors: Gouttebroze, P.; Dame, L.; Malherbe, J. -M.
1984MmSAI..55..245G Altcode:
An analysis is undertaken of a time sequence of quiet sun filtergrams
taken in the core of the K line, in order to investigate the oscillatory
properties of the chromosphere. The physical significance of these
intensity variations and their diagnostic capabilities are discussed,
and an oscillatory power vs. frequency and mean intensity diagram
is noted to indicate the different behaviors of bright regions
dominated by low frequency waves and darker regions dominated by high
frequency waves. A diagnostic wavenumber-frequency diagram indicates
two oscillatory power concentrations which approximately correspond to
acoustic and gravity waves, in chromospheric conditions. A theoretical
diagnostic diagram computed on the basis of a solar atmosphere model
exhibits a 'g-1' chromospheric mode; this corresponds almost exactly
to the location of the observed ridge.

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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.

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Title: Méthodes aux différences finies pour la résolution
numérique des équations aux dérivées partielles de la dynamique
des fluides et de la magnétohydrodynamique dans le cadre de
problèmes à conditions aux limites et conditions initiales.
Authors: Malherbe, J. -M.
1984cms..conf..221M Altcode:
No abstract at ADS

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Title: Observation and analysis of intensity oscillations in the
solar K-line
Authors: Dame, L.; Gouttebroze, P.; Malherbe, J. -M.
1984A&A...130..331D Altcode:
Chromospheric oscillations are investigated with a time sequence
of filtergrams of the sun taken in the core of the Ca II K-line at
the Sacramento Peak Observatory. The relations between oscillation
frequency and wavenumber are analyzed, as are those between frequency
and mean intensity. Intensity analysis reveals that low frequency waves
are associated mainly with bright (chromospheric network) regions,
while the '3-min' oscillation dominates in cell interiors. As the mean
brightness of the observed region increases, the high frequency limit
of oscillatory power decreases. This is interpreted as the decrease of
the resonance frequency of the chromospheric cavity with increasing
temperatures, which confirms the chromospheric origin of the 3-min
oscillations. Diagnostic diagrams suggest that both acoustic and
internal gravity waves occur in the chromosphere and appear to have
a modal structure.

---------------------------------------------------------
Title: Equilibre MHD et instabilités dans les protubérances ou
filaments solaires.
Authors: Malherbe, J. -M.
1984cms..conf..383M Altcode:
No abstract at ADS

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Title: Current sheet models for solar prominences. II - Energetics
and condensation process
Authors: Malherbe, J. M.; Priest, E. R.; Forbes, T. G.; Heyvaerts, J.
1983A&A...127..153M Altcode:
A steady state dynamic model for solar prominences of the Kuperus and
Raadu type was previously proposed by Malherbe and Priest (1983), but
only the motion through series of quasi-static states was investigated
there. The mechanisms for formation, condensation and cooling of
plasma in this model are studied. As hot coronal material approaches
the filament sheet, it is expected to cool and condense. Cold material
is then carried up through the prominence by rising magnetic field
lines due to converging photospheric motions below the filament. Two
possible ways are suggested of triggering a thermal instability and so
producing such a stationary condensation process: a larger pressure in
the sheet, or a smaller wave heating in the reconnected field than in
the surrounding corona. This paper presents a simple model to simulate
the plasma condensation: the thermodynamics of the cooling process,
as well as the dynamics of new material entering the prominence sheet,
are described in detail.

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Title: Current sheet models for solar prominences. I
Magnetohydrostatics of support and evolution through quasi-static
models
Authors: Malherbe, J. M.; Priest, E. R.
1983A&A...123...80M Altcode:
Several 2D current sheet models for solar prominences, supported against
gravity by potential magnetic configurations, are presented. Simple
magnetostatic solutions, both of Kuperus-Raadu type (KR) and of
Kippenhahn-Schlüter type (KS) are built with the help of complex
functions and discussed. The authors suggest that, in the case of KS
models, slow (&lt;100 ms-1) diverging photospheric flows
below prominences could explain the upward motions reported by Malherbe
et al. (1983) in disk filaments; while, in the case of KR models, slow
converging flows could explain them. To account for such motions and
magnetic field observations by Leroy et al. (1983) it is proposed in
Raadu's spirit (1979), a quasi-static reconnection model, in which new
material entering the prominence condenses and is brought up through
it by the moving magnetic field. The resulting dynamics is studied in
a simple magnetic geometry of KR type.

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Title: Equilibre magnetohydrodynamique des protuberances solaires
Authors: Malherbe, Jean-Marie
1983MsT.........21M Altcode:
A study of the magneto hydrodynamic equilibrium of solar prominences,
PhD THESIS, University of PARIS 7

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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.

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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.

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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: 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: 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