explanation blue bibcodes open ADS page with paths to full text
Author name code: mein
ADS astronomy entries on 2022-09-14
author:"Mein, Pierre" OR author:"Mein, Nicole"
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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<SUP>-1</SUP> at high precision
(50 m s<SUP>-1</SUP>) 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: Non-LTE Inversion of Prominence Spectroscopic Observations
in Hα and Mg II h&k lines
Authors: Jejčič, Sonja; Heinzel, Petr; Schmieder, Brigitte; Gunár,
Stanislav; Mein, Pierre; Mein, Nicole; Ruan, Guiping
2022ApJ...932....3J Altcode:
We continued our investigation of the plasma characteristics of a
quiescent prominence that occurred on 2017 March 30. The prominence
was observed simultaneously by several instruments, including the
Interface Region Imaging Spectrograph (IRIS) and the Multichannel
Subtractive Double Pass (MSDP) spectrograph operating at the Meudon
solar tower. We focused on IRIS Mg II h&k and MSDP Hα spectra,
selecting 55 well-coaligned points within the prominence. We computed
an extensive grid of 63,000 isothermal and isobaric 1D-slab prominence
models with a non-LTE (i.e., departures from the local thermodynamic
equilibrium) radiative transfer code. We then performed a 1.5D
spectral inversion searching for an optimal model that best fits
five parameters of the observed profiles (observables), namely,
the integrated intensity of the Hα and Mg II k lines, the FWHM of
both lines, and the ratio of intensities of the Mg II k and Mg II h
lines. The latter is sensitive to temperature. Our results show that
the prominence is a low-temperature structure, mostly below 10,000
K, with some excursions to higher values (up to 18,000 K) but also
rather low temperatures (around 5000 K). The microturbulent velocity is
typically low, peaking around 8 km s<SUP>-1</SUP>, and electron density
values are of the order of 10<SUP>10</SUP> cm<SUP>-3</SUP>. The peak
effective thickness is 500 km, although the values range up to 5000
km. The studied prominence is rather optically thin in the Hα line
and optically thick in the Mg II h&k lines.
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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 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: Spectro-imagery of an active tornado-like prominence: Formation
and evolution
Authors: Barczynski, Krzysztof; Schmieder, Brigitte; Peat, Aaron W.;
Labrosse, Nicolas; Mein, Pierre; Mein, Nicole
2021A&A...653A..94B Altcode: 2021arXiv210604259B
Context. The dynamical nature of fine structures in prominences remains
an open issue, including rotating flows in tornado prominences. While
the Atmospheric Imaging Assembly imager aboard the Solar Dynamics
Observatory allowed us to follow the global structure of a tornado-like
prominence for five hours, the Interface Region Imaging Spectrograph,
and the Multichannel Subtractive Double Pass spectrograph permitted
to obtain plasma diagnostics of its fine structures. <BR /> Aims: We
aim to address two questions. Firstly, is the observed plasma rotation
conceptually acceptable in a flux rope magnetic support configuration
with dips? Secondly, how is the plasma density distributed in the
tornado-like prominence? <BR /> Methods: We calculated line-of-sight
velocities and non-thermal line widths using Gaussian fitting for Mg II
lines and the bisector method for Hα line. We determined the electron
density from Mg II line integrated intensities and profile fitting
methods using 1D non-LTE radiative transfer theory models. <BR />
Results: The global structure of the prominence observed in Hα, and
Mg II h, and k line fits with a magnetic field structure configuration
with dips. Coherent Doppler shifts in redshifted and blueshifted areas
observed in both lines were detected along rapidly-changing vertical
and horizontal structures. However, the tornado at the top of the
prominence consists of multiple fine threads with opposite flows,
suggesting counter-streaming flows rather than rotation. Surprisingly
we found that the electron density at the top of the prominence could
be larger (10<SUP>11</SUP> cm<SUP>−3</SUP>) than in the inner part
of the prominence. <BR /> Conclusions: We suggest that the tornado
is in a formation state with cooling of hot plasma in a first phase,
and following that, a phase of leakage of the formed blobs with large
transverse flows of material along long loops extended away from the
UV prominence top. The existence of such long magnetic field lines on
both sides of the prominence would stop the tornado-like prominence
from really turning around its axis. <P />Movies are available at <A
href="https://www.aanda.org/10.1051/0004-6361/202140976/olm">https://www.aanda.org</A>
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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: Spectral inversion of H-alpha and MgII lines in quiescent
prominences
Authors: Heinzel, Petr; Schmieder, Brigitte; Ruan, Guiping; Mein,
Pierre; Gunár, Stanislav; Jejcic, Sonja; Mein, Nicole
2021cosp...43E1764H Altcode:
Recent spectral analysis of simultaneous H-alpha (MSDP) and MgII
lines (IRIS) (Guiping et al. 2019) has revealed certain bifurcation
in resulting models. Two solutions were found from the line inversions
using the non-LTE modeling: relatively high kinetic temperature and low
non-thermal motions or temperatures mostly compatible with standard ones
plus non-thermal motions of the order of 16 km/sec. Here we will present
an improved spectral line inversion technique which clearly prefers
the latter solution. Strong non-thermal motions are then interpreted
as a mixture of microturbulence and the line-of-sight dynamics of
prominence fine-structure threads. A detailed multithread modeling with
the 2D non-LTE code and stochastic distributions of threads (position,
dynamics) is now in progress and we will show our preliminary results.
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Title: Active tornado in a prominence observed in H-alpha with MSDP
and Mg II with IRIS
Authors: Barczynski, Krzysztof; Schmieder, Brigitte; Mein, Pierre;
Labrosse, Nicolas; Mein, Nicole; Peat, Aaron
2021cosp...43E.973B Altcode:
Large prominences with highly dynamic plasma features expand outwards in
the solar atmosphere, often in loop or arch-shape or as a tornado. The
origin of the rotating flow in prominence tornadoes is not fully
understood yet. We aim to find an answer to two long-standing questions:
what is the nature of the plasma flow and rotation in the prominence,
and the role of the magnetic field configuration in the prominence
dynamics? To this aim, we use observations from the Atmospheric Imaging
Assembly (AIA) imager aboard the Solar Dynamics Observatory (SDO) to
follow the plasma dynamics related to magnetic field. Simultaneous
observations from the Interface Region Imaging Spectrograph (IRIS)
and the Multi subtractive Double pass spectrograph (MSDP) allow
us to study the plasma properties (intensity, Doppler velocity,
non-thermal line broadening) of a tornado-like structure. We calculate
line-of-sight velocities and non-thermal line width using Gaussian
fitting for Mg II lines (IRIS) and a bisector method for H$\alpha$
line (MSDP). We determine the electron density and temperature from
Mg II line integrated intensities using radiative transfer theory. We
find that the red and blue Doppler-shifted areas present a coherent
position in H$\alpha$ and Mg II h\&k lines along the fast-evolving
prominence features. The EUV observations suggest long magnetic field
lines on the sides of the prominence. The tornado-like at the top of
the prominence consists of multiplefine threads with opposite flows, all
of them being supported in dips of long magnetic field lines. From time
to time, condensed blobs escape along these field lines. We conjecture
that micro or macro turbulence exists at the top of the prominence
and could form the small threads giving the impression of rotation.
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Title: Raymond Michard and his solar physics group at Paris-Meudon
Observatory
Authors: Mein, Pierre; Mein, Nicole
2020JAHH...23..582M Altcode:
During the second half of the twentieth century, an important Solar
Research Department was developed in the Paris-Meudon Observatory
thanks to Raymond Michard. After several years devoted to theoretical
studies about stellar atmospheres at the Institut d'Astrophysique de
Paris Michard joined the Paris-Meudon Observatory in 1954. He replaced
Lucien d'Azambuja as Director of the Solar Section, and succeeded
to attract new young scientists, while building new high-performance
instruments in good sites such as Pic du Midi. He became Director of
the Solar and Planetary Department in 1968. All topics of solar physics
were investigated, providing many results about coronal physics, solar
activity and flares, but also fine structures of the quiet Sun. Michard
knew that the best research involved successful collaborations. Eclipse
missions, international cooperation and access to space instruments
were developed. Participation to the European JOSO association prepared
the future THEMIS telescope. In 1971 Michard left the Solar Department
to be successively the President of Paris Observatory and then Nice
Observatory. But his Solar Physics group in Meudon went on working
with topics and means that he had successfully initiated.
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Title: Diagnostics of the Prominence Plasma from Hα and Mg II
Spectral Observations
Authors: Ruan, Guiping; Jejčič, Sonja; Schmieder, Brigitte; Mein,
Pierre; Mein, Nicole; Heinzel, Petr; Gunár, Stanislav; Chen, Yao
2019ApJ...886..134R Altcode:
The goal of this paper is to derive the physical conditions of the
prominence observed on 2017 March 30. To do so, we use a unique set
of data in Mg II lines obtained with the space-borne Interface Region
Imaging Spectrograph (IRIS) and in Hα line with the ground-based
Multi-Channel Subtractive Double Pass spectrograph operating at the
Meudon solar tower. Here, we analyze the prominence spectra of Mg
II h and k lines, and the Hα line in the part of the prominence
which is visible in both sets of lines. We compute a grid of 1D
NLTE (i.e., departures from the local thermodynamical equilibrium)
models providing synthetic spectra of Mg II k and h, and Hα lines
in a large space of model input parameters (temperature, density,
pressure, and microturbulent velocity). We compare Mg II and Hα
line profiles observed in 75 positions of the prominence with the
synthetic profiles from the grid of models. These models allow us
to compute the relationships between the integrated intensities
and between the optical thickness in Hα and Mg II k lines. The
optical thickness τ <SUB>Hα </SUB> is between 0.05 and 2, and
{τ }<SUB>Mg</SUB>{{II}}{{k}}} is between 3 and 200. We show that
the relationship of the observed integrated intensities agrees well
with the synthetic integrated intensities for models with a higher
microturbulence (16 km s<SUP>-1</SUP>) and T around 8000 K, ne =
1.5 × 10<SUP>10</SUP> cm<SUP>-3</SUP>, p = 0.05 dyne. In this case,
large microturbulence values could be a way to take into account the
large mixed velocities existing in the observed prominence.
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Title: Bidirectional Reconnection Outflows in an Active Region
Authors: Ruan, Guiping; Schmieder, Brigitte; Masson, Sophie; Mein,
Pierre; Mein, Nicole; Aulanier, Guillaume; Chen, Yao
2019ApJ...883...52R Altcode:
We report on bidirectional coronal reconnection outflows reaching
±200 km s<SUP>-1</SUP> as observed in an active region with the Si
IV and C II spectra of the Interface Region Imaging Spectrograph
(IRIS). The evolution of the active region with an emerging flux,
a failed filament eruption, and a jet is followed in Solar Dynamical
Observatory (SDO)/Atmospheric Imaging Assembly (AIA) filters from
304 to 94 Å, IRIS slit jaw images, and SDO/Helioseismic and Magnetic
Imager movies. The bidirectional outflow reconnection is located at
a bright point visible in multiwavelength AIA filters above an arch
filament system. This suggests that the reconnection occurs between
rising loops above the emergence of magnetic bipoles and the longer,
twisted magnetic field lines remnant of the failed filament eruption
one hour before. The reconnection occurs continuously in the corona
between quasi-parallel magnetic field lines, which is possible in a
3D configuration. The reconnection also triggers a jet with transverse
velocities around 60 km s<SUP>-1</SUP>. Blueshifts and redshifts along
its axis confirm the existence of a twist along the jet, which could
have been transferred from the filament flux rope. The jet finally
blows up the material of the filament before coming back during the
second phase. In the Hα Dopplergrams provided by the MSDP spectrograph,
we see more redshift than blueshift, indicating the return of the jet
and filament plasma.
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Title: Exploration of long-period oscillations in an Hα prominence
Authors: Zapiór, M.; Schmieder, B.; Mein, P.; Mein, N.; Labrosse,
N.; Luna, M.
2019A&A...623A.144Z Altcode: 2019arXiv190300230Z
Context. In previous work, we studied a prominence which appeared like
a tornado in a movie made from 193 Å filtergrams obtained with the
Atmospheric Imaging Assembly (AIA) imager aboard the Solar Dynamics
Observatory (SDO). The observations in Hα obtained simultaneously
during two consecutive sequences of one hour with the Multi-channel
Subtractive Double Pass Spectrograph (MSDP) operating at the solar
tower in Meudon showed that the cool plasma inside the tornado was
not rotating around its vertical axis. Furthermore, the evolution
of the Dopplershift pattern suggested the existence of oscillations
of periods close to the time-span of each sequence. <BR /> Aims:
The aim of the present work is to assemble the two sequences of
Hα observations as a full data set lasting two hours to confirm the
existence of oscillations, and determine their nature. <BR /> Methods:
After having coaligned the Doppler maps of the two sequences, we use a
Scargle periodogram analysis and cosine fitting to compute the periods
and the phase of the oscillations in the full data set. <BR /> Results:
Our analysis confirms the existence of oscillations with periods between
40 and 80 min. In the Dopplershift maps, we identify large areas with
strong spectral power. In two of them, the oscillations of individual
pixels are in phase. However, in the top area of the prominence,
the phase is varying slowly, suggesting wave propagation. <BR />
Conclusions: We conclude that the prominence does not oscillate as a
whole structure but exhibits different areas with their own oscillation
periods and characteristics: standing or propagating waves. We discuss
the nature of the standing oscillations and the propagating waves. These
can be interpreted in terms of gravito-acoustic modes and magnetosonic
waves, respectively. <P />Movie attached to Fig. 2 is available at <A
href="https://www.aanda.org/10.1051/0004-6361/201833614/olm">https://www.aanda.org</A>
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Title: On the Dynamic Nature of a Quiescent Prominence Observed by
IRIS and MSDP Spectrographs
Authors: Ruan, Guiping; Schmieder, Brigitte; Mein, Pierre; Mein,
Nicole; Labrosse, Nicolas; Gunár, Stanislav; Chen, Yao
2018ApJ...865..123R Altcode:
Quiescent solar prominences are generally considered to have a stable
large-scale structure. However, they consist of multiple small-scale
structures that are often significantly dynamic. To understand
the nature of prominence plasma dynamics we use the high spatial,
temporal, and spectral resolution observations obtained by Interface
Region Imaging Spectrograph (IRIS) during a coordinated campaign
with the Multichannel Subtractive Double Pass spectrograph at the
Meudon Solar Tower. Detailed analysis of the IRIS observations of
Mg II lines, including the analysis of Dopplershift and line width
obtained with two different methods (quantile method and Gaussian-fit
method) are discussed in the frame of the dynamic nature of the
structures. Large-scale coherent blueshift and redshift features are
observed in Mg II lines and Hα exhibiting a slow evolution during 1:40
hr of observations. We explain the presence of several significantly
asymmetric peaks in the observed Mg II line profiles by the presence
of several prominence fine structures moving with different velocities
located along the line of sight (LOS). In such a case, the decrease
of the intensity of individual components of the observed spectra
with the distance from the central wavelength can be explained by the
Doppler dimming effect. We show that C II line profiles may be used
to confirm the existence of multi-components along the LOS.
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Title: Dynamics in quiescent prominences observed by the IRIS and
MSDP spectrographs
Authors: Gunár, Stanislav; Schmieder, Brigitte; Ruan, Guiping; Mein,
Pierre; Heinzel, Petr
2018cosp...42E1314G Altcode:
Quiescent solar prominences are generally considered to
be stable. However, these prominences consist of a multitude of
small-scale structures or threads that are often significantly
dynamic. To understand the nature of the plasma dynamics we use the
high spatial, temporal and spectral resolution observations obtained
by IRIS during coordinated campaign with the MSDP spectrograph
at the Meudon Solar Tower. Mg II h and k lines observed by IRIS
represent a good diagnostic tool for investigation of the prominence
fine structure dynamics, as they are optically thick under the
prominence conditions. We will present detailed IRIS observations of
Mg II lines. We explain significant asymmetries in the observed Mg II
spectra by the presence of several threads located along the line of
sight with different velocities. In such a case, the decrease of the
intensity of individual components of the observed spectra with the
distance from the central wavelength can be explained by the Doppler
dimming effect. To interpret the observed Mg II profiles in terms
of dynamics we use 1D or 2D radiative transfer models including a
prominence-corona transition region. We also show that the H-alpha
line which is optically thinner than the Mg II doublet is an important
constrain for the radiative transfer radiation modelling.
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Title: Prominence/Tornado plasma parameters
Authors: Schmieder, Brigitte; Mein, Pierre; Zapior, Maciej; Labrosse,
Nicolas; Lopez Ariste, Arturo
2018cosp...42E3025S Altcode:
We present a comparison of the plasma physical parameters in prominences
and tornadoes using IRIS data and ground based polarimetry measurements
obtained with THEMIS. Mg II lines give a good diagnostics of the
temperature and optical thickness of the structures. The Stokes
parameters from the He D3 line allow to distinguish the behaviour
of the magnetic field in typical prominences and atypical prominences
(e.g. bubbles, eruptive prominence). We concentrate on the Dopplershifts
in a tornado observed in transition region lines and in Halpha. Our
results support the existence of oscillations in tornadoes but not
rotation.A reconstruction of the 3D geometry of a helical prominence
obtained by following the trajectory of kernels yields surprising
results. The loops are shown to be quasi-horizontal structures with
no curvature.We conclude that it is important to take into account the
3D structure of the prominence to study the dynamics of the prominence
plasma.
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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: Prominence and tornado dynamics observed with IRIS and THEMIS
Authors: Schmieder, Brigitte; Levens, Peter; Labrosse, Nicolas; Mein,
Pierre; Lopez Ariste, Arturo; Zapior, Maciek
2017SPD....4820104S Altcode:
Several prominences were observed during campaigns in September 2013 and
July 2014 with the IRIS spectrometer and the vector magnetograph THEMIS
(Tenerife). SDO/AIA and IRIS provided images and spectra of prominences
and tornadoes corresponding to different physical conditions of the
transition region between the cool plasma and the corona. The vector
magnetic field was derived from THEMIS observations by using the He
D3 depolarisation due to the magnetic field. The inversion code (PCA)
takes into account the Hanle and Zeeman effects and allows us to compute
the strength and the inclination of the magnetic field which is shown
to be mostly horizontal in prominences as well as in tornadoes. Movies
from SDO/AIA in 304 A and Hinode/SOT in Ca II show the highly dynamic
nature of the fine structures. From spectra in Mg II and Si IV lines
provided by IRIS and H-alpha observed by the Multi-channel Subtractive
Double Pass (MSDP) spectrograph in the Meudon Solar Tower we derived
the Doppler shifts of the fine structures and reconstructed the 3D
structure of tornadoes. We conclude that the apparent rotation of AIA
tornadoes is due to large-scale quasi-periodic oscillations of the
plasma along more or less horizontal magnetic structures.
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Title: Hα Doppler shifts in a tornado in the solar corona
Authors: Schmieder, B.; Mein, P.; Mein, N.; Levens, P. J.; Labrosse,
N.; Ofman, L.
2017A&A...597A.109S Altcode: 2016arXiv161202232S
Context. High resolution movies in 193 Å from the Atmospheric
Imaging Assembly (AIA) on the Solar Dynamic Observatory (SDO)
show apparent rotation in the leg of a prominence observed during
a coordinated campaign. Such structures are commonly referred to as
tornadoes. Time-distance intensity diagrams of the AIA data show the
existence of oscillations suggesting that the structure is rotating. <BR
/> Aims: The aim of this paper is to understand if the cool plasma
at chromospheric temperatures inside the tornado is rotating around
its central axis. <BR /> Methods: The tornado was also observed in Hα
with a cadence of 30 s by the MSDP spectrograph, operating at the Solar
Tower in Meudon. The MSDP provides sequences of simultaneous spectra
in a 2D field of view from which a cube of Doppler velocity maps is
retrieved. <BR /> Results: The Hα Doppler maps show a pattern with
alternatively blueshifted and redshifted areas of 5 to 10” wide. Over
time the blueshifted areas become redshifted and vice versa, with
a quasi-periodicity of 40 to 60 min. Weaker amplitude oscillations
with periods of 4 to 6 min are superimposed onto these large period
oscillations. <BR /> Conclusions: The Doppler pattern observed in
Hα cannot be interpreted as rotation of the cool plasma inside the
tornado. The Hα velocity observations give strong constraints on the
possible interpretations of the AIA tornado.
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Title: Height formation of bright points observed by IRIS in Mg II
line wings during flux emergence
Authors: Grubecka, M.; Schmieder, B.; Berlicki, A.; Heinzel, P.;
Dalmasse, K.; Mein, P.
2016A&A...593A..32G Altcode:
Context. A flux emergence in the active region AR 111850 was observed
on September 24, 2013 with the Interface Region Imaging Spectrograph
(IRIS). Many bright points are associated with the new emerging flux
and show enhancement brightening in the UV spectra. <BR /> Aims:
The aim of this work is to compute the altitude formation of the
compact bright points (CBs) observed in Mg II lines in the context
of searching Ellerman bombs (EBs). <BR /> Methods: IRIS provided two
large dense rasters of spectra in Mg II h and k lines, Mg II triplet,
C II and Si IV lines covering all the active region and slit jaws in
the two bandpasses (1400 Å and 2796 Å) starting at 11:44 UT and
15:39 UT, and lasting 20 min each. Synthetic profiles of Mg II and
Hα lines are computed with non-local thermodynamic equlibrium (NLTE)
radiative transfer treatment in 1D solar atmosphere model including
a hotspot region defined by three parameters: temperature, altitude,
and width. <BR /> Results: Within the two IRIS rasters, 74 CBs are
detected in the far wings of the Mg II lines (at +/-1 Å and 3.5
Å). Around 10% of CBs have a signature in Si IV and CII. NLTE models
with a hotspot located in the low atmosphere were found to fit a sample
of Mg II profiles in CBs. The Hα profiles computed with these Mg II
CB models are consistent with typical EB profiles observed from ground
based telescopes e.g. THEMIS. A 2D NLTE modelling of fibrils (canopy)
demonstrates that the Mg II line centres can be significantly affected
but not the peaks and the wings of Mg II lines. <BR /> Conclusions:
We conclude that the bright points observed in Mg II lines can be
formed in an extended domain of altitudes in the photosphere and/or
the chromosphere (400 to 750 km). Our results are consistent with the
theory of heating by Joule dissipation in the atmosphere produced by
magnetic field reconnection during flux emergence.
---------------------------------------------------------
Title: Fast inversion of Zeeman line profiles using central
moments. II. Stokes V moments and determination of vector magnetic
fields
Authors: Mein, P.; Uitenbroek, H.; Mein, N.; Bommier, V.; Faurobert, M.
2016A&A...591A..64M Altcode:
Context. In the case of unresolved solar structures or stray light
contamination, inversion techniques using four Stokes parameters
of Zeeman profiles cannot disentangle the combined contributions of
magnetic and nonmagnetic areas to the observed Stokes I. <BR /> Aims:
In the framework of a two-component model atmosphere with filling factor
f, we propose an inversion method restricting input data to Q , U, and
V profiles, thus overcoming ambiguities from stray light and spatial
mixing. <BR /> Methods: The V-moments inversion (VMI) method uses
shifts S<SUB>V</SUB> derived from moments of V-profiles and integrals
of Q<SUP>2</SUP>, U<SUP>2</SUP>, and V<SUP>2</SUP> to determine the
strength B and inclination ψ of a magnetic field vector through
least-squares polynomial fits and with very few iterations. Moment
calculations are optimized to reduce data noise effects. To specify the
model atmosphere of the magnetic component, an additional parameter
δ, deduced from the shape of V-profiles, is used to interpolate
between expansions corresponding to two basic models. <BR /> Results:
We perform inversions of HINODE SOT/SP data for inclination ranges 0
<ψ< 60° and 120 <ψ< 180° for the 630.2 nm Fe I line. A
damping coefficient is fitted to take instrumental line broadening into
account. We estimate errors from data noise. Magnetic field strengths
and inclinations deduced from VMI inversion are compared with results
from the inversion codes UNNOFIT and MERLIN. <BR /> Conclusions:
The VMI inversion method is insensitive to the dependence of Stokes I
profiles on the thermodynamic structure in nonmagnetic areas. In the
range of Bf products larger than 200 G, mean field strengths exceed
1000 G and there is not a very significant departure from the UNNOFIT
results because of differences between magnetic and nonmagnetic model
atmospheres. Further improvements might include additional parameters
deduced from the shape of Stokes V profiles and from large sets of
3D-MHD simulations, especially for unresolved magnetic flux tubes.
---------------------------------------------------------
Title: Magnetic Field and Plasma Diagnostics from Coordinated
Prominence Observations
Authors: Schmieder, B.; Levens, P.; Dalmasse, K.; Mein, N.; Mein,
P.; Lopez-Ariste, A.; Labrosse, N.; Heinzel, P.
2016ASPC..504..119S Altcode:
We study the magnetic field in prominences from a statistical point of
view, by using THEMIS in the MTR mode, performing spectropolarimetry
of the He I D<SUB>3</SUB> line. Combining these measurements with
spectroscopic data from IRIS, Hinode/EIS as well as ground-based
telescopes, such as the Meudon Solar Tower, we infer the temperature,
density, and flow velocities of the plasma. There are a number of
open questions that we aim to answer: - What is the general direction
of the magnetic field in prominences? Is the model using a single
orientation of magnetic field always valid for atypical prominences? %-
Does this depend on the location of the filament on the disk (visible
in Hα, in He II 304 Å) over an inversion line between weak or strong
network ? - Are prominences in a weak environment field dominated by
gas pressure? - Measuring the Doppler shifts in Mg II lines (with IRIS)
and in Hα can tell us if there are substantial velocities to maintain
vertical rotating structures, as has been suggested for tornado-like
prominences. We present here some results obtained with different
ground-based and space-based instruments in this framework.
---------------------------------------------------------
Title: Understanding the Mg II and Hα Spectra in a Highly Dynamical
Solar Prominence
Authors: Heinzel, P.; Schmieder, B.; Mein, N.; Gunár, S.
2015ApJ...800L..13H Altcode:
Mg ii h and k and Hα spectra in a dynamical prominence have been
obtained along the slit of the Interface Region Imaging Spectrograph
(IRIS) and with the Meudon Multi-channel Subtractive Double Pass
spectrograph on 2013 September 24, respectively. Single Mg ii line
profiles are not much reversed, while at some positions along
the IRIS slit the profiles show several discrete peaks that are
Doppler-shifted. The intensity of these peaks is generally decreasing
with their increasing Doppler shift. We interpret this unusual behavior
as being due to the Doppler dimming effect. We discuss the possibility
to interpret the unreversed single profiles by using a two-dimensional
(2D) model of the entire prominence body with specific radiative
boundary conditions. We have performed new 2D isothermal-isobaric
modeling of both Hα and Mg ii lines and show the ability of such models
to account for the line profile variations as observed. However, the Mg
ii line-center intensities require the model with a temperature increase
toward the prominence boundary. We show that even simple one-dimensional
(1D) models with a prominence-to-corona transition region (PCTR) fit the
observed Mg ii and Hα lines quite well, while the isothermal-isobaric
models (1D or 2D) are inconsistent with simultaneous observations in
the Mg ii h and k and Hα lines, meaning that the Hα line provides a
strong additional constraint on the modeling. IRIS far-UV detection of
the C ii lines in this prominence seems to provide a direct constraint
on the PCTR part of the model.
---------------------------------------------------------
Title: Open questions on prominences from coordinated observations
by IRIS, Hinode, SDO/AIA, THEMIS, and the Meudon/MSDP
Authors: Schmieder, B.; Tian, H.; Kucera, T.; López Ariste, A.;
Mein, N.; Mein, P.; Dalmasse, K.; Golub, L.
2014A&A...569A..85S Altcode: 2014arXiv1407.3171S
Context. A large prominence was observed by multiple instruments on the
ground and in space during an international campaign on September 24,
2013, for three hours (12:12 UT -15:12 UT). Instruments used in the
campaign included the newly launched (June 2013) Interface Region
Imaging Spectrograph (IRIS), THEMIS (Tenerife), the Hinode Solar
Optical Telescope (SOT), the Solar Dynamic Observatory's Atmospheric
Imaging Assembly (SDO/AIA), and the Multichannel Subtractive Double
Pass spectrograph (MSDP) in the Meudon Solar Tower. The movies obtained
in 304 Å with the EUV imager SDO/AIA, and in Ca II line by SOT show
the dynamic nature of the prominence. <BR /> Aims: The aim of this
work is to study the dynamics of the prominence fine structures in
multiple wavelengths to understand their formation. <BR /> Methods:
The spectrographs IRIS and MSDP provided line profiles with a high
cadence in Mg II h (2803.5 Å) and k (2796.4 Å) lines along four
slit positions (IRIS), and in Hα in a 2D field of view (MSDP). The
spectropolarimetry of THEMIS (Tenerife) allowed us to derive the
magnetic field of the prominence using the He D<SUB>3</SUB> line
depolarization (Hanle effect combined with the Zeeman effect). <BR />
Results: The magnetic field is found to be globally horizontal with
a relatively weak field strength (8-15 Gauss). On the other hand,
the Ca II movie reveals turbulent-like motion that is not organized in
specific parts of the prominence. We tested the addition of a turbulent
magnetic component. This model is compatible with the polarimetric
observations at those places where the plasma turbulence peaks. On the
other hand, the Mg II line profiles show multiple peaks well separated
in wavelength. This is interpreted by the existence of small threads
along the line of sight with a large dispersion of discrete values of
Doppler shifts, from 5 km s<SUP>-1</SUP> (a quasi-steady component) to
60-80 km s<SUP>-1</SUP>. Each peak corresponds to a Gaussian profile,
and not to a reversed profile as was expected by the present non-LTE
radiative transfer modeling. This is a very surprising behavior for
the Mg II line observed in prominences. <BR /> Conclusions: Turbulent
fields on top of the macroscopic horizontal component of the magnetic
field supporting the prominence give rise to the complex dynamics of
the plasma. The plasma with the high velocities (70 km s<SUP>-1</SUP> to
100 km s<SUP>-1</SUP> if we take into account the transverse velocities)
may correspond to condensation of plasma along more or less horizontal
threads of the arch-shape structure visible in 304 Å. The steady
flows (5 km s<SUP>-1</SUP>) would correspond to a more quiescent plasma
(cool and prominence-corona transition region) of the prominence packed
into dips in horizontal magnetic field lines. The very weak secondary
peaks in the Mg II profiles may reflect the turbulent nature of parts
of the prominence. <P />Movies are available in electronic form at <A
href="http://www.aanda.org/10.1051/0004-6361/201423922/olm">http://www.aanda.org</A>
---------------------------------------------------------
Title: 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: 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. <BR /> 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. <BR
/> 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. <BR /> 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<SUP>-1</SUP>, but with a mean
velocity of 0.35 km s<SUP>-1</SUP>. In some locations, horizontal
flows crossing the channel are detected, indicating eventually large
scale vorticity. <BR /> 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<SUP>-1</SUP> 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. <P />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 of a prominence observed in Mg II lines by IRIS
Authors: Schmieder, Brigitte; Mein, Pierre; Dalmasse, Kévin; Tian,
Hui; Kucera, Therese; Lopez-Ariste, Arturo
2014cosp...40E2927S Altcode:
In September 2013 several prominences were observed with the IRIS
spectrograph during a 60 day-long international program. We will present
one set of observations obtained using multiple instruments on September
24. SDO/AIA and IRIS slit jaws provided images of the prominence
corresponding to different physical conditions of the transition
region between the cool plasma and the corona. The vector magnetic
field was derived from THEMIS (Tenerife) observations using the He D3
depolarisation due to the magnetic field. The inversion code (CPA) takes
into account the Hanle and the Zeeman effects. Movies from SDO/AIA in
304 A and Hinode/SOT in Ca II show the dynamics of the fine structures
in the plane of the sky. From Mg II and Si IV line spectra observed by
IRIS and H-alpha observed by the Multi-channel subtractive spectrograph
(MSDP) in the Meudon solar tower we derived the Dopplershifts of the
fine structures. The profiles of the Mg II lines are narrow (FHWM =0.15
A) and not reversed, contrary to the predictions of the theoretical
models (Paletou et al 1993). We could resolve the velocity of several
structures along the LOS with Dopplershifts as high as 60 km/s.
---------------------------------------------------------
Title: Dynamics in the filament of september 17 2010 and in its
channel
Authors: Mein, Nicole; Mein, Pierre; Schmieder, Brigitte; Malherbe,
Jean-Marie; Roudier, Thierry
2014IAUS..300..451M Altcode:
Dynamics of a filament is investigated in Hα. Counterstreaming flows
are observed along the filament. Photospheric horizontal motions have
been computed by using a Coherent Structure Tracking algorithm in the
filament environment.
---------------------------------------------------------
Title: Proper horizontal photospheric flows below an eruptive filament
Authors: Schmieder, Brigitte; Mein, Pierre; Mein, Nicole; Roudier,
Thierry; Chandra, Ramseh
2014cosp...40E2926S Altcode:
An analysis of the proper motions using SDO/HMI continuum images with
the new version of the coherent structure tracking (CST) algorithm
developed to track the granules as well as the large scale photospheric
flows, was perfomed during three hours in a region containing a large
filament channel on September 17, 2010. Supergranules were idenfied
in the filament channel. Diverging flows inside the supergranules are
similar in and out the filament channel. Using corks, we derived the
passive scalar points and produced maps of cork distribution. The
anchorage structures with the photosphere (feet) of the filament
are located in the areas of converging flows with accumulations of
corks. Averaging the velocity vectors for each latitude we defined a
profile of the differential rotation. We conclude that the coupling
between the convection and magnetic field in the photosphere is
relatively strong. The filament experienced the convection motions
through its feet. On a large scale point-of-view the differential
rotation induced a shear of 0.1 km/s in the filament. On a small scale
point-of-view convection motions favored the interaction/cancellation of
the parasitic polarities at the base of the feet with the surrounding
network explaining the brightenings,/jets and the eruption that were
observed in the EUV filament.
---------------------------------------------------------
Title: Multi-purpose grating spectrograph for the 4-meter European
Solar Telescope
Authors: Calcines, A.; Collados, M.; Feller, A.; Gelly, B.; Grauf, B.;
Hirzberger, J.; López Ariste, A.; Lopez, R. L.; Mein, P.; Sayéde, F.
2012SPIE.8446E..6TC Altcode:
This communication presents a family of spectrographs designed for
the European Solar Telescope. They can operate in four different
configurations: a long slit standard spectrograph (LsSS), two devices
based on subtractive double pass (TUNIS and MSDP) and one based on
an integral field, multi-slit, multi-wavelength configuration. The
combination of them composes the multi-purpose grating spectrograph of
EST, focused on supporting the different science cases of the solar
photosphere and chromosphere in the spectral range from 3900 Å to
23000 Å. The different alternatives are made compatible by using
the same base spectrographs and different selectable optical elements
corresponding to specific subsystems of each configuration.
---------------------------------------------------------
Title: The S4I prototype: a beam-slicer system dedicated to the
new generation multichannel subtractive double pass for EST imaging
spectropolarimetry
Authors: Sayède, Frédéric; Mein, Pierre; Amans, Jean-Philippe;
Moity, Jacques
2012SPIE.8446E..6ZS 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 beam slicer
prototype that will be tested and validated on an optical bench and
on existing telescopes. The prototype called S4I (Spectral Sampling
with Slicer for Solar Instrumentation) is under construction and
tested at the Observatoire de Paris. It validates the opto-mechanical
feasibility of the new beam slicer. The manufacture is now complete:
we give a description of the whole system. We give also some results
of the first tests.
---------------------------------------------------------
Title: Velocity Vector, Ionization Degree, and Temperature of
Prominence Fine Structures Observed by Hinode/SOT
Authors: Schmieder, B.; Mein, P.; Chandra, R.; Molodij, G.; Heinzel,
P.; Berlicki, A.; Schwartz, P.; Fárník, F.; Labrosse, N.; Anzer,
U.; Watanabe, T.
2012ASPC..454..107S Altcode:
Prominences have been successfully observed by Hinode in April 2007
exhibiting a strong dynamics of their fine structures. The dynamics
of a prominence is a challenge to understand the formation of cool
prominence plasma embedded in the hot corona. Combining simultaneous
observations obtained in Hα with Hinode/SOT and the MSDP spectrograph
operating at the Meudon solar tower, velocity vectors have been
derived. The Doppler-shifts of bright threads are of the same order
as the velocities measured perpendicular to the line of sight. This
suggests that the vertical structures of the prominence could be a pile
up of dips in magnetic field lines viewed in 3D. Using Hα, Hinode/XRT
and TRACE data, the hydrogen ionization degree has been determined to
be 0.5-0.8, and the optical thickness in Hα between 0.2 and 1.3. The
Extreme Ultraviolet Imaging Spectrometer (EIS) on Hinode produced images
of the prominence in 11 selected lines with formation temperatures
between log(T) = 4.7 and log(T) = 6.1. We comment on the absorption,
emissivity blocking and emission involved for interpreting the different
structures of the prominence in terms of the temperature and density.
---------------------------------------------------------
Title: Prominence fine-structure dynamics as inferred from 2D
non-LTE models
Authors: Gunar, Stanislav; Schmieder, Brigitte; Mein, Pierre;
Heinzel, Petr
2012cosp...39..683G Altcode: 2012cosp.meet..683G
2D multi-thread prominence fine structure models are able to
produce synthetic Lyman spectra in very good agreement with spectral
observations by SOHO/SUMER including the spectral line asymmetries. The
synthetic differential emission measure curves derived from these
models are also in a good agreement with observations. Now we show that
these models are also able to produce synthetic H-alpha line profiles
in very good agreement with observations which allows us to analyze
not only the physical parameters of the prominence fine-structure
plasma but also some aspects of its dynamical behaviour. We compare
the synthetic H-alpha spectra with the observed spectra of the
April 26, 2007 prominence using three statistical parameters: the
line integrated intensity, the line full-width at the half-maximum
(FWHM), and the Doppler velocity derived from shifts of the line
profiles. This statistical analysis allows us to conclude that the
overall statistical distribution of the LOS velocities in the April 26,
2007 prominence at the time of the observations was below +/-15 km/s
and in the prominence core was close to +/-10 km/s. In combination
with the analysis of the Lyman spectra we determine several physical
parameters of the observed prominence fine structures which show that
the April 26, 2007 prominence was relatively less massive. We are also
able to put some constrains on the prominence core temperature that
might be relatively low, reaching values below 6000 K.
---------------------------------------------------------
Title: Dynamics of quiescent prominence fine structures analyzed by
2D non-LTE modelling of the Hα line
Authors: Gunár, S.; Mein, P.; Schmieder, B.; Heinzel, P.; Mein, N.
2012A&A...543A..93G Altcode:
<BR /> Aims: We analyze the dynamics of the prominence fine
structures of a quiescent prominence observed on April 26, 2007
during a coordinated campaign of several spaceborne and ground-based
instruments. We use Lyman spectra observed by SOHO/SUMER and the
Hα line spectra obtained by MSDP spectrograph working at the
Meudon Solar Tower. <BR /> Methods: We employ the 2D multi-thread
prominence fine-structure modelling that includes randomly distributed
line-of-sight (LOS) velocities of individual threads to derive models
producing synthetic Lyman lines in good agreement with the SOHO/SUMER
observations. We then use these models to produce synthetic Hα
line spectra that we compare with the observed spectra using three
statistical parameters: the line integrated intensity, the line
full-width at half-maximum (FWHM), and the Doppler velocity derived
from shifts of the line profiles. <BR /> Results: We demonstrate that
the 2D multi-thread models that produce synthetic Lyman spectra in
agreement with observations also generate synthetic Hα spectra in
good agreement with the observed ones. The statistical analysis of the
FWHM and Doppler velocities of the synthetic Hα line profiles show
that the overall LOS velocities in the April 26, 2007 prominence at
the time of the observations were below 15 km s<SUP>-1</SUP> and in
the prominence core were close to 10 km s<SUP>-1</SUP>. In combination
with the analysis of the Lyman spectra, we determine several physical
parameters of the observed prominence fine-structures that show
that the April 26, 2007 prominence had a relatively low-mass weakly
magnetized structure. We are also able to impose some constraints
on the prominence core temperature, which may be relatively low,
with values below 6000 K. <BR /> Conclusions: The combination of
2D non-LTE prominence fine-structure modelling with the statistical
analysis of the observed and synthetic Lyman and Hα spectra allows us
to analyze the influence of the model input parameters and the velocity
fields on the synthetic Hα line profiles, thus determine the overall
dynamics of the observed prominence as well as the physical parameters
of its plasma. <P />Appendix A is available in electronic form at <A
href="http://www.aanda.org">http://www.aanda.org</A>
---------------------------------------------------------
Title: Inversion of Zeeman Line Profiles Using Central Moments
Authors: Mein, P.; Uitenbroek, H.; Mein, N.; Bommier, V.; Faurobert, M.
2012EAS....55...83M Altcode:
A new inversion method derived from central moments of Zeeman line
profiles (ICM), is used to determine magnetic field vectors (Mein et
al. 2011). Two quantities A<SUB>1</SUB> and A<SUB>2</SUB> combining
moments of profiles I ± S (S = Q,U,V) are nearly linear functions
of the longitudinal and transverse components and lead to the field
components through very fast iterations. Optimized exponents reduce
noise effects. The ICM inversion does not require Milne Eddington
approximation and can be used in a wide range of solar models.
---------------------------------------------------------
Title: New generation Multichannel Subtractive Double Pass for
imaging spectropolarimetry - The S4I prototype
Authors: Sayede, F.; Mein, P.; Amans, J. -P.; Moity, J.
2012EAS....55..385S Altcode:
Imaging spectropolarimetry is a powerful tool in solar
physics. Multichannel Subtractive Double Pass (MSDP) spectrographs
can produce simultaneous 2D images in a number of wavelengths
covering several line profiles with the following advantages: -
Contrary to long slit spectroscopy, the spatial resolution can reach
the diffraction limit. - Contrary to narrow band filters, full line
profiles are recorded at the same time without any image motion and
differential seeing effect. MSDP spectrographs use an entrance window
instead of the usual long slit. A new generation MSDP using slicers
made of mirrors instead of prisms is proposed for the future 4 m class
European Solar Telescope. We describe the beam slicer prototype S4I
(Spectral Sampling with Slicer for Solar Instrumentation) that will
be tested soon at the 14 m spectrograph of the Meudon Solar Tower.
---------------------------------------------------------
Title: Magnetic Field Structures in a Facular Region Derived from
THEMIS and Hinode Vector Magnetic Field
Authors: Guo, Y.; Schmieder, B.; Bommier, V.; Mein, P.
2012ASPC..456...55G Altcode:
In order to compare vector magnetic fields obtained by two spectral
polarimeters (THEMIS/MTR and Hinode SOT/SP) and two inversion codes
(UNNOFIT and MELANIE), we observed a facular region in the active region
NOAA 10996 on 2008 May 23. We found that they give consistent results
concerning the distributions of field strengths, azimuth and inclination
angles. SOT/SP could resolve small magnetic polarities with sizes of
1” to 2”, and detect convergence and divergence of the horizontal
components of magnetic fields in the facular cells. These findings
support the models suggesting the existence of flux tube bundles
in faculae. With this model and multi spectral line observations,
we could infer the relative formation heights of those spectral lines.
---------------------------------------------------------
Title: Fast inversion of Zeeman line profiles using central moments
Authors: Mein, P.; Uitenbroek, H.; Mein, N.; Bommier, V.; Faurobert, M.
2011A&A...535A..45M Altcode:
Context. Many inversion techniques derive vector magnetic fields and
other parameters of the solar atmosphere from Stokes profiles with an
iterative process. <BR /> Aims: We propose a new inversion method, using
functions derived from central moments (ICM), to determine magnetic
field vectors with very few iterations. <BR /> Methods: Two quantities
A<SUB>1</SUB> and A<SUB>2</SUB> that combine moments of profiles I ±
S (S = Q,U,V) are proposed. They are nearly linear functions of the
longitudinal and transverse components of the magnetic field, and lead
to estimates of the field components through a least-squares polynomial
fit. A third quantity A<SUB>D</SUB> can be used to interpolate between
expansions that correspond to two basic models. Exponents β<SUB>1</SUB>
and β<SUB>2</SUB> in the moment expressions are adjusted to minimize
the sensitivity to data noise. <BR /> Results: Inversion coefficients
are computed for magnetic fields up to 3000 G in the case of the 630.2
Fe i line by forward modeling in two selected 1D model atmospheres
(FALC and MALTM). After inversion of synthetic profiles computed with
four models at disk center (FALA, FALC, FALF, MALTM), the mean standard
deviations with respect to the input fields do not exceed 5 G for both
components over the full range 0-3000 G. A comparison of ICM results
with inversion by the UNNOFIT code of profiles observed with THEMIS/MTR
shows good agreement. The typical computing time for a solar map of 100
000 points is less than 30 s. <BR /> Conclusions: The ICM inversions
are almost insensitive to thermodynamic properties and solve for vector
magnetic fields in a wide range of solar conditions, ranging from plage
to spot, with very little computational effort. They are, therefore,
extremely suitable for large data sets. Further improvements should
take into account instrumental profiles and effects of limited spatial
resolution by using filling factors. Extensions using more parameters
and models with large departures from the Milne Eddington approximation
could also be considered.
---------------------------------------------------------
Title: The Shape of the Solar Limb: Models and Observations
Authors: Thuillier, G.; Claudel, J.; Djafer, D.; Haberreiter, M.; Mein,
N.; Melo, S. M. L.; Schmutz, W.; Shapiro, A.; Short, C. I.; Sofia, S.
2011SoPh..268..125T Altcode: 2010SoPh..tmp..202T; 2010SoPh..tmp..226T
In this paper we compare observed, empirical, and modelled solar limb
profiles and discuss their potential use to derive physical properties
of the solar atmosphere. The PHOENIX, SolMod3D, and COSI radiative
transfer codes as well as VAL-C models are used to calculate the
solar limb shape under different assumptions. The main properties
of each model are shown. The predicted limb shape as a function of
wavelength for different features on the solar disk, such as quiet Sun,
sunspots, and faculae, is investigated. These models provide overall
consistent limb shapes with some discrepancies that are discussed
here in terms of differences in solar atmosphere models, opacities,
and the algorithms used to derive the solar limb profile. Our analysis
confirms that the most common property of all models is limb shapes that
are much steeper than what is observed, or predicted by the available
empirical models. Furthermore, we have investigated the role of the
Fraunhofer lines within the spectral domain used for the solar limb
measurements. Our results show that the presence of the Fraunhofer
lines significantly displaces the limb inflection point from its
position estimated assuming only the photospheric continuum. The PICARD
satellite, launched on 15 June 2010, will provide measurements of the
limb shape at several wavelengths. This work shows that the precision of
these measurements allows for discrimination among the available models.
---------------------------------------------------------
Title: New generation multichannel subtractive double pass for EST
imaging spectropolarimetry
Authors: Sayède, Frédéric; Mein, Pierre; Amans, Jean-Philippe;
Moity, Jacques
2010SPIE.7735E..7NS Altcode: 2010SPIE.7735E.248S
Any future solar telescope project should incorporate an imaging
spectrometer. For the future EST (European Solar Telescope) the
Observatoire de Paris offers an imaging spectro-porarimetry instrument:
a new generation of MSDP. To validate this new generation, we develop
a beam slicer prototype that will be tested and validated on optical
bench and on existing telescopes. The study assesses the performance
gain of such an instrument on a solar 4m class telescope. We present
opto-mechanical solutions of a new beam splitter and its implementation
in EST.
---------------------------------------------------------
Title: Spectrograph capabilities of the European Solar Telescope
Authors: Calcines, A.; Collados, M.; Feller, A.; Grauf, B.;
Grivel-Gelly, C.; Hirzberger, J.; López Ariste, A.; López López,
R.; Mein, P.; Sayède, F.
2010SPIE.7735E..20C Altcode: 2010SPIE.7735E..68C
EST is a project for a 4-meter class telescope to be located in the
Canary Islands. EST will be optimized for studies of the magnetic
coupling between the photosphere and the chromosphere. This requires
high spatial and temporal resolution diagnostics tools of properties of
the plasma, by using multiple wavelength spectropolarimetry. To achieve
these goals, visible and near-IR multi-purpose spectrographs are being
designed to be compatible with different modes of use: LsSS (Long-slit
Standard Spectrograph), multi-slit multi-wavelength spectrograph with
an integral field unit, TUNIS (Tunable Universal Narrow-band Imaging
Spectrograph), and new generation MSDP (Multi-channel Subtractive
Double-pass Spectrograph). In this contribution, these different
instrumental configurations are described.
---------------------------------------------------------
Title: Velocity vectors of a quiescent prominence observed by
Hinode/SOT and the MSDP (Meudon)
Authors: Schmieder, B.; Chandra, R.; Berlicki, A.; Mein, P.
2010A&A...514A..68S Altcode: 2009arXiv0911.5091S
Context. The dynamics of prominence fine structures present a
challenge to our understanding of the formation of cool plasma
prominence embedded in the hot corona. <BR /> Aims: Observations
performed by the high resolution Hinode/SOT telescope allow us to
compute velocities perpendicular to the line-of-sight or transverse
velocities. Combining simultaneous observations obtained in Hα with
Hinode/SOT and the MSDP spectrograph operating in the Meudon solar
tower, we derive the velocity vectors of a quiescent prominence. <BR
/> Methods: The velocities perpendicular to the line-of-sight are
measured using a time-slice technique and the Doppler shifts velocity
using the bisector method. <BR /> Results: The Doppler shifts of
bright threads derived from the MSDP show counterstreaming of the
order of 5 km s<SUP>-1</SUP> in the prominence and reaching 15 km
s<SUP>-1</SUP> at the edges of the prominence. Even though they are
minimum values because of seeing effects, they are of the same order
as the transverse velocities. <BR /> Conclusions: These measurements
are very important because they suggest that the vertical structures
detected by SOT may not be true vertical magnetic structures in the sky
plane. The vertical structures could be a pile up of dips in more or
less horizontal magnetic field lines in a 3D perspective, as proposed
by many MHD modelers. In our analysis, we also calibrate the Hinode
Hα data using MSDP observations obtained simultaneously. <P />A movie
is available in electronic form at http://www.aanda.org
---------------------------------------------------------
Title: Counterstreaming in quiescent prominences observed by
Hinode/SOT and Meudon/MSDP
Authors: Schmieder, Brigitte; Chandra, Ramesh; Berlicki, Arkadiusz;
Mein, Pierre
2010cosp...38.2943S Altcode: 2010cosp.meet.2943S
Prominences have been successfully observed by Hinode in April 2007
exhibiting a strong dy-namics of their fine structures. The dynamics
of a prominence is a challenge to understand the formation of cool
prominence plasma embedded in the hot corona. Combining simultaneous
observations obtained in Hα with Hinode/SOT and the MSDP spectrograph
operating at the Meudon solar tower, velocity vectors have been
derived. The Doppler-shifts of bright threads are of the same order
as the transverse velocities measured perpendicularly to the line of
sight. Counterstreamings are detected at the top of the prominence. The
vertical structures of the prominence could be a pile up of dips in
magnetic field lines viewed in 3D
---------------------------------------------------------
Title: Model studies of the solar limb shape variation with wavelenght
within the PICARD project.
Authors: Melo, Stella M. L.; Thuillier, Gerard; Claudel, Jennyfer;
Haberreiter, Margit; Mein, Nicole; Schmutz, Werner; Shapiro, Alexander;
Sofia, Sabatino; Short, Christopher I.
2010cosp...38.1756M Altcode: 2010cosp.meet.1756M
Solar images in the visible wavelength range show that the disk centre
is brighter than the limb region. This phenomenon, which is both known
as "centre to limb variation (CLV)", or "limb darkening function", is
know to depend on wavelength. Since the CLV is determined by the density
and temperature stratification, as well as the chemical composition
of the so-lar photosphere, its measurement is important to validate
theoretical assumption made when building numerical models of the
solar atmosphere. The definition of the solar diameter is nor-mally
adopted as the separation between two inflection points at opposite
ends of a line passing through the center of the solar disk. Therefore,
in order to understand long term variability on the solar diameter, it
is important to understand what drives the dependence of the position
of the inflection point on wavelength. In this paper we use different
available solar atmosphere models to study this dependence. The results
presented here refer to quiet Sun conditions and encompass the visible
and near infra-red spectral regions, which are the regions of interest
for the PICARD Satellite Mission. In a first step we utilize the solar
atmosphere parameters with a radiative transfer code. This allows for
the study of the impact of different factors such as opacities, electron
density and temperature from different models on the results. Then, we
compare results obtained using each solar atmosphere model. Our results
are compared with existent ground based measurements performed by the
Pic du Midi telescope, the balloon board measurements with the Solar
Disk Sextant experiment, and with the measurements by the Michelson
Doppler Imager on board SoHO satellite. The model simulations show that
the position of the inflection point is sensitive to the different
parameters and model assumptions. Furthermore, our study shows, for
the first time, that the position of the inflection point changes
dramatically with and outside of Fraunhofer lines.
---------------------------------------------------------
Title: Fast imaging spectroscopy with MSDP spectrometers. Vector
magnetic maps with THEMIS/MSDP
Authors: Mein, P.; Mein, N.; Bommier, V.
2009A&A...507..531M Altcode:
Context: Multichannel subtractive double pass (MSDP) spectrometers
produce 3D data cubes (x, y, λ) simultaneously across several line
profiles. They do not suffer from image convolution by any slit width,
and synchronous observations across all wavelengths avoid differential
seeing effects. They are very suitable for fast 2D spectroscopy. <BR
/>Aims: (1) We review specifications and capabilities of some existing
MSDP spectrometers with respect to high-cadence observations. (2)
THEMIS/MSDP is designed for the spectropolarimetry of strong lines. We
propose new data reductions also suitable for the spectropolarimetry of
photospheric lines. <BR />Methods: An off-line algorithm is described
as a way to increase the spectral resolution. Taking the opportunity
of 3D data, spatial interpolations are used around each solar point by
only assuming that intensity gradients partial I(x, y, λ)/partial x
are constant in the range (x± ɛ_x,λ ± ɛ_λ). The UNNOFIT inversion
is used to compare vector magnetic maps deduced from THEMIS/MSDP and
slit-spectropolarimetry THEMIS/MTR data. <BR />Results: Both results
are in good agreement. In active regions, the rms of the MSDP noise,
calculated over 1 arcsec^2, is less than 24 G for the LOS magnetic
field and less than 52 G for B<SUB>x</SUB> and 32 G for B_y. The MSDP
scanning speed is 10 times the speed of slit-spectropolarimetry. <BR
/>Conclusions: THEMIS/MSDP can provide vector magnetic maps with typical
temporal resolutions that are less than 1 min for small fields-of-view
and 10 min for active regions. This allows addressing a number of fast
events. In the future, MSDP instruments should efficiently complement
single-slit spectroscopy and tunable filters. Their main capabilities
should be the multiline aspect and the high temporal and spatial
resolutions. New optical devices, such as image slicers, should
substantially increase the signal-to-noise ratio. For polarimetric
measurements, various compromises are possible between speed, spatial
resolution, and SNR. A-posteriori image restorations, either using wide
band proxies or bursts of multi-wavelength short exposures, should help
improving signal-to-noise ratio and spatial resolution. <P />Based on
observations made with the French-Italian telescope THEMIS operated by
the CNRS and CNR on the island of Tenerife in the Spanish Observatorio
del Teide of the Instituto de Astrofísica de Canarias.
---------------------------------------------------------
Title: Spectro-imagery at the solar tower of meudon.
Authors: Mein, P.
2008LAstr.122f..16M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectrophotometric analysis of Ellerman bombs in the Ca II,
Hα, and UV range
Authors: Pariat, E.; Schmieder, B.; Berlicki, A.; Deng, Y.; Mein,
N.; López Ariste, A.; Wang, S.
2007A&A...473..279P Altcode:
Context: Even if Ellerman bombs have been observed in the Hα line
within emerging magnetic flux regions since the early 20th century,
their origin and the mechanisms that lead to their formation have been
strongly debated. Recently, new arguments in favor of chromospheric
magnetic reconnection have been advanced. Ellerman bombs seem to be
the signature of reconnections that take place during the emergence
of the magnetic field. <BR />Aims: We have observed an active region
presenting emergence of magnetic flux. We detected and studied
Ellerman bombs in two chromospheric lines: Ca ii 8542 Å and Hα. We
investigated the link between Ellerman bombs and other structures and
phenomena appearing in an emerging active region: UV bright points,
arch filament systems, and magnetic topology. <BR />Methods: On August
3, 2004, we performed multi-wavelength observations of the active
region NOAA 10655. This active region was the target of SoHO Joint
Observation Program 157. Both SoHO/MDI and TRACE (195 Å and 1600 Å)
were used. Simultaneously, we observed in the Ca ii and Na D1 lines
with the spectro-imager MSDP mode of THEMIS. Alternately to the MSDP,
we used the MTR spectropolarimeter on THEMIS to observe in Hα and
in the Fe i doublet at 6302 Å. We derived the magnetic field vectors
around some Ellerman bombs. <BR />Results: We present the first images
of EBs in the Ca ii line and confirm that Ellerman bombs can indeed
be observed in the Ca ii line, presenting the same “moustache”
geometry profiles as in the Hα line, but with a narrower central
absorption in the Ca ii line, in which the peaks of emission are
around ±0.35 Å. We noticed that the Ellerman bombs observed in the
wings of Ca ii line have an elongated shape - the length about 50%
greater than the width. We derived mean semi-axis lengths of 1.4”
× 2.0”. In the UV time profiles of the Ellerman bombs, we noticed
successive enhanced emissions. The distribution of lifetimes of these
individual impulses presents a strong mode around 210 s. Study of the
magnetic topology shows that 9 out of the 13 EBs are located on the
inversion line of the longitudinal field and that some typical examples
might be associated with a bald patch topology. <BR />Conclusions: We
provide new arguments in favor of the reconnection origin of Ellerman
bombs. The different individual impulses observed in UV may be related
to a bursty mode of reconnection. We also show that this Ca ii 8542
Å chromospheric line is a good indicator of Ellerman bombs and can
bring new information about these phenomena.
---------------------------------------------------------
Title: Fast vector magnetographs: THEMIS/MSDP and EST project
Authors: Mein, P.; Bommier, V.; Mein, N.
2007sf2a.conf..601M Altcode:
Imaging spectro-polarimetry with Multichannel Subtractive Double
Pass (MSDP) is able to provide vector magnetic fields with high
temporal resolution. We present some results obtained with THEMIS and
reduced with the UNNOFIT code, as well as a new method to achieve
off-line the required spectral resolution. Performances of slit-
and imaging-spectroscopy are briefly compared, together with the high
capabilities expected from the EST project.
---------------------------------------------------------
Title: Dual-line spectral and phase analysis of sunspot oscillations
Authors: Tziotziou, K.; Tsiropoula, G.; Mein, N.; Mein, P.
2007A&A...463.1153T Altcode:
Context: Sunspots exhibit a wide range of oscillatory phenomena within
their umbrae and penumbrae. <BR />Aims: We investigate the behavior
of intensity and Doppler velocity oscillations in the umbra and the
penumbra to study sunspot oscillations and their associations. <BR
/>Methods: Simultaneous, high-cadence (8 s), two-dimensional, Ca
II 8542 Å and Hα 6563 Å observations are used. Doppler velocity
and intensity variations are studied with a wavelet spectral, phase
difference and coherence analysis, both at distinct positions and
within the whole umbra and the penumbra. <BR />Results: The analysis
reveals the presence of several umbral flashes (UFs) that seem to
fill the whole umbra. The spectral analysis indicates oscillating
elements of size 2.5” to 5” within the umbra with periods around
the 3-min band and oscillation periods around the 5-min band within
the penumbra. Two remarkable jumps of the oscillation period and the
intensity-velocity phase difference are present at both umbra-penumbra
and penumbra-superpenumbra boundaries reflecting a drastic change in
physical and/or magnetic conditions. The intensity-velocity phase
analysis shows a delay of the intensity response to the velocity
variations in accordance with the physics of the observed sawtooth
velocity behavior. Most of the UFs oscillate incoherently, while the
calmest umbral area seems to be associated with velocity spreading
from neighboring UFs. The derived incoherency among UFs in conjunction
with the existence of coherently oscillating elements within the umbra
suggests the presence of umbral areas with slightly different physical
and/or magnetic field conditions. <BR />Conclusions: .The presented
analysis provides further important constraints for realistic models
and theoretical interpretations describing sunspot oscillations.
---------------------------------------------------------
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. <BR
/>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. <BR />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. <BR />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: Fast vector magnetic maps with imaging spectroscopy
Authors: Mein, P.; Mein, N.; Bommier, V.
2007MmSAI..78..160M Altcode:
We present a new observing mode of THEMIS / MSDP which can provide fast
vector magnetic maps of the solar photosphere in the 610.27 Ca line.
---------------------------------------------------------
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: <P />-
magnetic and non-magnetic bright features can be discriminated by simple
criteria of intensities and dopplershifts. <P />- 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. <P />- Best qualitative
agreements are obtained with clusters of magnetic flux tubes.
---------------------------------------------------------
Title: Dual-line analysis of sunspot oscillations
Authors: Tziotziou, K.; Tsiropoula, G.; Mein, N.; Mein, P.
2007MmSAI..78...98T Altcode:
Umbral oscillations and running penumbral (RP) waves are studied
with simultaneous, two-dimensional, high cadence (8 sec), dual-line
sunspot observations in Ca II 8542 Å and Halpha , obtained with the
MSDP spectrograph on the German VTT in Tenerife. Doppler velocity and
intensity images are used to investigate the physical characteristics
of umbral flashes (UFs) and RP waves while a wavelet spectral and phase
analysis shows their temporal behaviour and permits us to elaborate
on their nature and possible association.
---------------------------------------------------------
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: Evolving Photospheric Flux Concentrations and Filament
Dynamic Changes
Authors: Schmieder, B.; Aulanier, G.; Mein, P.; Ariste, A. López
2006SoPh..238..245S Altcode: 2006SoPh..tmp...64S
We analyze the role of weak photospheric flux concentrations that
evolve in a filament channel, in the triggering of dynamic changes in
the shape of a filament. The high polarimetric sensitivity of THEMIS
allowed us to detect weak flux concentrations (few Gauss) associated
with the filament development. The synoptic instruments (MDI, SOLIS)
even if their sensitivity is much less than THEMIS were useful to
follow any subsequent strengthening of these flux concentrations after
their identification in the THEMIS magnetograms. We found that (1)
the northern part of the filament develops an Hα barb at the same
time that weak minority polarity elements develop near a plage; (2)
a section in the southern part of the Hα filament gradually disappears
and later reforms at the same time that several mixed-polarity magnetic
elements appear, then subsequently cancel or spread away from each
other. These changes correspond to increases in EUV emission, as
observed by TRACE, EIT, and CDS. This suggests that the plasma is
temporarily heated along the filament spine. An idealized sequence of
force-free models of this filament channel, based on plasma-supporting
magnetic dips occurring in the windings of a very weakly twisted flux
tube, naturally explains the evolution of its southern part as being
due to changes in the topology of the coronal magnetic field as the
photospheric flux concentrations evolve.
---------------------------------------------------------
Title: Long-period astronomical forcing of mammal turnover
Authors: van Dam, Jan A.; Abdul Aziz, Hayfaa; Ángeles Álvarez Sierra,
M.; Hilgen, Frederik J.; van den Hoek Ostende, Lars W.; Lourens, Lucas
J.; Mein, Pierre; van der Meulen, Albert J.; Pelaez-Campomanes, Pablo
2006Natur.443..687V Altcode:
Mammals are among the fastest-radiating groups, being characterized
by a mean species lifespan of the order of 2.5millionyears (Myr). The
basis for this characteristic timescale of origination, extinction
and turnover is not well understood. Various studies have invoked
climate change to explain mammalian species turnover, but other studies
have either challenged or only partly confirmed the climate-turnover
hypothesis. Here we use an exceptionally long (24.5-2.5Myr ago), dense,
and well-dated terrestrial record of rodent lineages from central
Spain, and show the existence of turnover cycles with periods of
2.4-2.5 and 1.0Myr. We link these cycles to low-frequency modulations
of Milankovitch oscillations, and show that pulses of turnover occur
at minima of the 2.37-Myr eccentricity cycle and nodes of the 1.2-Myr
obliquity cycle. Because obliquity nodes and eccentricity minima are
associated with ice sheet expansion and cooling and affect regional
precipitation, we infer that long-period astronomical climate forcing
is a major determinant of species turnover in small mammals and probably
other groups as well.
---------------------------------------------------------
Title: Observational characteristics and association of umbral
oscillations and running penumbral waves
Authors: Tziotziou, K.; Tsiropoula, G.; Mein, N.; Mein, P.
2006A&A...456..689T Altcode:
Context: .Umbral flashes (UFs) and running penumbral (RP) waves are
believed to be closely related oscillatory phenomena of sunspots.<BR />
Aims: .We investigate the association of UFs and RP waves to see whether
the latter are a visual pattern created by a common source with UFs
or a trans-sunspot wave driven by UFs.<BR /> Methods: .Simultaneous,
two-dimensional, dual-line observations in Ca II 8542 Å and Hα
6563 Å, obtained with the Multichannel Subtractive Double Pass (MSDP)
spectrograph mounted on the German VTT at Teide Observatory on Tenerife,
are used for this study. High-cadence 8 s Doppler velocity images,
spectrograms, and spectral-analysis results are used to study the
characteristics and the relationship of UFs and RP waves.<BR /> Results:
.Several UFs were observed that seem to fill the whole umbra. Doppler
velocity variations with time indicate a shock behaviour for UFs, as
well as for umbral and RP waves and a smooth continuous propagation
of the latter from the umbra through the umbra-penumbra boundary
out to the edge of the penumbra. Furthermore, the spectral analysis
shows a decreasing oscillatory frequency as we move from the umbra
outwards and a jump at the umbra-penumbra boundary that could possibly
reflect, apart from a change in physical conditions, a drastic change
of the magnetic field inclination with respect to the vertical.<BR />
Conclusions: .The results do not permit us to convincingly support one
scenario over the other (i.e. visual pattern vs. trans-sunspot wave)
for RP waves; however, they do provide important constraints for future
models of sunspot oscillations and RP waves.
---------------------------------------------------------
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.<BR /> 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.<BR /> 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.<BR /> 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.<BR />
---------------------------------------------------------
Title: THEMIS/MSDP magnetic field measurements
Authors: Berlicki, A.; Mein, P.; Schmieder, B.
2006A&A...445.1127B Altcode:
We present an analysis of longitudinal magnetic field measurements
using the spectral data obtained with the French - Italian
polarisation free telescope THEMIS working in Multichannel Subtractive
Double Pass (MSDP) mode. We also used SOHO/MDI data to extend our
analysis. THEMIS observations in the MSDP mode allows us to perform
imaging spectropolarimetry characterized by high spatial and time
resolution. In our analysis we used the observations of solar active
region NOAA 10484 performed on October 20, 2003. From THEMIS 2D
spectral images recorded in Na D<SUB>1</SUB> 5896 Å line we obtained
the longitudinal magnetic field in the active region. The value of
the magnetic field was calculated at different distances from the
Na D<SUB>1</SUB> line centre. We determine the LOS magnetic field at
different heights in the solar atmosphere. SOHO/MDI observations provide
the longitudinal magnetic field in Ni I (6768 Å) line. THEMIS/MSDP
measurements at Δλ= 0.30 Å are similar to SOHO/MDI results. Gradients
of longitudinal magnetic fields derived from MSDP measurements at Δλ=
0.08 and Δλ=0.24 Å exhibit different behaviours according to solar
targets. A decrease with height is seen in spot umbrae and penumbrae,
while the gradient in facular and network areas suggests a slight
increase of the longitudinal magnetic field, which might be explained
by the 3D-structure of canopies.
---------------------------------------------------------
Title: Active Region Magnetic Field Observed with Themis/msdp and
Soho/mdi Instruments
Authors: Berlicki, A.; Mein, P.; Schmieder, B.
2005ESASP.600E..57B Altcode: 2005ESPM...11...57B; 2005dysu.confE..57B
No abstract at ADS
---------------------------------------------------------
Title: Sunspot Umbral Oscillations and Running Waves
Authors: Tziotziou, K.; Tsiropoula, G.; Mein, N.; Mein, P.
2005ESASP.600E..15T Altcode: 2005dysu.confE..15T; 2005ESPM...11...15T
No abstract at ADS
---------------------------------------------------------
Title: Non-LTE diagnostics of velocity fields during the gradual
phase of a solar flare
Authors: Berlicki, A.; Heinzel, P.; Schmieder, B.; Mein, P.; Mein, N.
2005A&A...430..679B Altcode:
We perform an analysis of the velocity field within the Hα ribbons
during the gradual phase of an M 1.0 solar flare observed on October 22,
2002. We use spectroscopic observations performed with the German VTT
(Vacuum Tower Telescope) working in the MSDP (Multichannel Subtractive
Double Pass spectrograph) observing mode. From these observations
the Hα line profiles in chosen areas of the flare ribbons were
reconstructed and these observational profiles were compared with
a grid of synthetic Hα line profiles calculated by the non-LTE
radiative-transfer code. This code allows us to calculate different
models of the chromosphere with a prescribed velocity field. By
optimising the best fit between the observed and synthetic profiles
we find the most appropriate models of the chromosphere and vertical
structure of the velocity field in the analysed areas of the flare
ribbons. By means of the non-LTE radiative-transfer calculations
we show that in most analysed areas of the Hα flare ribbons the
chromospheric plasma exhibited upward motion with a mean velocity of
a few km;s<SUP>-1</SUP>. These results are consistent with previous
estimates and support the scenario of a gentle evaporation during the
gradual phase.
---------------------------------------------------------
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: On the nature of the chromospheric fine
structure. II. Intensity and velocity oscillations of dark mottles
and grains
Authors: Tziotziou, K.; Tsiropoula, G.; Mein, P.
2004A&A...423.1133T Altcode:
We study periodicities of dark mottles and grains observed in
high spatial and temporal resolution Hα 2-D intensity and velocity
images, obtained with the Multichannel Subtractive Double Pass (MSDP)
spectrograph at THEMIS in Tenerife, Canary Islands. Intensity and
velocity variations of individual mottles and grains, as well as of
large regions containing a substantial number of these structures
are examined with a wavelet analysis which provides the temporal
distribution of periods and with a randomization method that gives
the respective probabilities associated with them. The wavelet
analysis, which shows that velocity variations are the dominant
ones, results in a wide range of periods, from 100 to 500 s, with
variable probabilities. However, it strongly indicates the presence
of a predominant period of ∼5 min seen in both dark mottle and grain
oscillations. We suggest that differences in periods found in individual
mottles as well as in averages of regions containing these structures
are due to the topology of the local magnetic field which can affect
oscillatory processes. We report for the first time oscillations of
dark grains which are more likely vertical structures “anchored"
in the photosphere. The analysis supports further the suggestion that
dark mottles and grains are the same structures, the only difference
between them being their respective inclinations to the line-of-sight.
---------------------------------------------------------
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<SUP>−1</SUP>,
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: Multi-wavelength flare study and magnetic configuration
Authors: Schmieder, Brigitte; Berlicki, A.; Vilmer, N.; Aulanier,
G.; Démoulin, P.; Mein, P.; Mandrini, C.; Deluca, E.
2004IAUS..223..397S Altcode: 2005IAUS..223..397S
Recent results of two observation campaigns (October 2002 and October
2003) are presented with the objective of understanding the onset
of flares and CMEs. The magnetic field was observed with THEMIS and
MDI, the chromosphere with the MSDP operating on the German telescope
VTT and on THEMIS, the EUV images with SOHO/CDS and TRACE, the X-ray
with RHESSI. We show how important is the magnetic configuration of
the active region to produce CMEs using two examples: the October 28
2003 X 17 flare and the October 22 2002 M 1.1 flare. The X 17 flare
gave a halo CME while the M 1.1 flare has no corresponding CME. The
magnetic topology analysis of the active regions is processed with a
linear-force-free field configuration.
---------------------------------------------------------
Title: On the Nature of Chromospheric Umbral Flashes And Running
Penumbral Waves (Abstract)
Authors: Tziotziou, K.; Tsiropoula, G.; Mein, N.; Mein, P.
2004hell.conf...50T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Multi-Wavelength Observations of an M1.0 Flare on 22 October
2002
Authors: Berlicki, A.; Schmieder, B.; Vilmer, N.; Mein, P.; Mein,
N.; Heinzel, P.; Staiger, J.; Deluca, E. E.
2004IAUS..219..669B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Magnetic configuration reorganisation before the X 17 flare
of October28 2003
Authors: Schmieder, B.; Mandrini, C.; Demoulin, P.; Mein, P.
2004cosp...35.1528S Altcode: 2004cosp.meet.1528S
The active region NOAA 0486 was observed during a multi-wavelength
campaign with ground based and space instruments. We analyse the
magnetic configuration of the region during a pre-event, which
reorganizes the magnetic connectivities of the field lines before the
occurence of a X17 flare of October 28 2003. The magnetic field was
observed with THEMIS and MDI, the chromosphere with the MSDP operating
on on THEMIS and with the Meudon heliograph, the EUV images with
SOHO/CDS and TRACE. The X17 flare gave a halo CME while the M1.9 flare
has no corresponding CME. The magnetic field analysis of the active
regions is performed by using a linear-force-free field code. The
pre-flare event before the X17 flare change the connectivities in a
first phase and allows the stressed field to relax in a second phase
producing the X17 flare.
---------------------------------------------------------
Title: Spectro-polarimetric observation of the fine structure of a
quiescent filament
Authors: Zong, W. G.; Tang, Y. H.; Fang, C.; Mein, P.; Mein, N.; Xu,
A. A.
2003A&A...412..267Z Altcode:
This paper presents the spectro-polarimetric measurements of a big
quiescent filament observed by the MSDP mode of the THEMIS on August
24, 2000. The Hα , CaII 8542 and NaI D2 line profiles of a segment of
the filament were obtained. By use of the Hα images with high spatial
resolution, the two barb endpoints were identified. The parameters at
the barbs' endpoints, including intensity, velocity and longitudinal
magnetic field were measured. Using the data with high spatial
resolution (0.16” per pixel), we have found the following results. 1)
There was mass motion at the barb endpoints in the chromosphere, the
values and the directions of the mass motion at the barb endpoints
change in several minutes. 2) The two barb endpoints are located
between the majority polarities and the minority polarities.
---------------------------------------------------------
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: On the nature of the chromospheric fine structure. I. Dynamics
of dark mottles and grains
Authors: Tziotziou, K.; Tsiropoula, G.; Mein, P.
2003A&A...402..361T Altcode:
We analyze a time series of forty high spatial and temporal resolution
two-dimensional intensity and Doppler velocity images at different
wavelengths within the Hα line. The observations were obtained with the
Multichannel Subtractive Double Pass (MSDP) spectrograph at THEMIS. We
study the morphology of dark mottles and grains as seen in different
wavelengths and examine their relation to the MDI magnetic field
topology. We determine some physical properties of dark mottles with
an inversion technique based on an iterative cloud model method with
constant source function, giving the optical thickness tau<SUB>0</SUB>,
the Doppler width Delta lambda<SUB>D</SUB> , the velocity v and the
source function S distribution along a structure. The obtained global
properties of mottles as well as the spatial and temporal evolution of
several physical parameters along the axes of individual mottles are
discussed. The derived velocities in mottles as a function of space
and time (time slice images) exhibit a quasi-periodic, bi-directional
pattern. It is suggested that magnetic reconnection is the mechanism
responsible for their formation and dynamics. Furthermore, a similar
quasi-periodic behaviour of the Doppler velocity variations in dark
grains and their morphological characteristics both suggest the
similarity of dark mottles and grains.
---------------------------------------------------------
Title: Na I D<SUB>1</SUB> 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: Osiris, HD 209458b, une exoplanete a l'allure de comete.
Authors: Ferlet, R.; Vidal-Madjar, A.; Lecavelier Des Etangs, A.;
Desert, J. -M.; Hebrard, G.; Mein, N.
2003LAstr.117..194F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectral diagnostics of the magnetic field orientation in a
round-shaped filament
Authors: Schmieder, B.; Mein, N.; Heinzel, P.; Anzer, U.
2002ESASP.506..469S Altcode: 2002ESPM...10..469S; 2002svco.conf..469S
During several campaigns focused on prominences we have obtained
coordinated spectral observations from the ground and from space. The
SOHO/SUMER spectrometer allows us to observe, among others, the whole
Lyman series of hydrogen, while the Hα line was observed by the MSDP
spectrograph at the VTT. For Lyman lines, the non-LTE radiative-transfer
computations have shown the importance of the prominence-corona
transition region (PCTR) and its relation to the magnetic field
orientation for the explanation of the observed line profiles (Schmieder
et al. 1998, Heinzel et al. 2001). Moreover, Heinzel and Anzer (2001)
developed new 2D models which demonstrate how the shapes of Lyman
lines vary depending on the orientation of the magnetic field with
respect to the line of sight. To confirm this result observationally,
we focus here on a round-shaped filament observed during three days
as it was crossing the limb. The Lyman profiles observed on the limb
are different from day to day and we interpret these differences by
the change of orientation of the prominence axis (and therefore the
magnetic field direction) with respect to the line-of-sight.
---------------------------------------------------------
Title: MHD waves in active region filament from SOHO-THEMIS joint
observations
Authors: Régnier, S.; Solomon, J.; Vial, J. C.; Mein, P.
2002ESASP.505..647R Altcode: 2002IAUCo.188..647R; 2002solm.conf..647R
The stability of solar filaments and their implications for eruptive
events can be revealed by the existence of magnetohydrodynamic
(MHD) waves. During the MEDOC campaign on May 2000, we performed
joint observations involving SOHO and THEMIS instruments (CDS and
MSDP respectively). We analyse the modes of oscillations for several
spectral lines (Hα at 6563 Å, He I at 584 Å and Mg X at 609 Å):
intermediate (6-40 min) and short (< 5 min) periods are found and
are discusssed in terms of MHD waves. The Hα time series (MSDP) in
both line center intensity and line-of-sight Doppler shifts provide
constraints on models of filament oscillations.
---------------------------------------------------------
Title: Magnetic cancellation and small-scale activity in an AR
filament
Authors: Schmieder, B.; Engvold, O.; Yong, Lin; Deng, Y. Y.; Mein, N.
2002ESASP.505..223S Altcode: 2002solm.conf..223S; 2002IAUCo.188..223S
A long set of observations obtained with the VTT/MSDP spectrograph
in September 1998 (8 to 11) allows us to follow the formation of a
complex filament in and around a nest of active regions during its
disk passage. Continuous shear of magnetic field in this region can
explain the formation and the relative stability of the filament
structure before the occurrence of a flare which leads to important
changes in the magnetic configuration. The corona overlying the region
and the flare, as well, is observed by TRACE. The studied filament
is stable on long term time scale. However, high spatial and temporal
observations obtained in La Palma (SVST) show high Doppler shifts and
strong transverse motions of absorbing blobs along the filament. These
velocities are directly related to magnetic activity as observed with
the SVST. A small scale magnetic analysis shows emergence of MMFs
(Moving Magnetic Features) around a decaying sunspot and canceling flux
with the neighbor network. Magnetic reconnection could occur and explain
the ejection of blobs along the new magnetic field lines. Formation
of the transient blobs is discussed.
---------------------------------------------------------
Title: Chromospheric fine structure dynamics
Authors: Tziotziou, K.; Tsiropoula, G.; Mein, P.
2002ESASP.505..163T Altcode: 2002solm.conf..163T; 2002IAUCo.188..163T
We investigate the dynamics of chromospheric mottles observed with
THEMIS. We study a half an hour time series of 2-D intensity and
Doppler velocity images at different wavelengths within the Hα
line, obtained with the Multichannel Subtractive Double Pass (MSDP)
spectrograph with a cadence of 40.5 sec. We determine the physical
parameters in dark mottles with an inversion technique which is based
on an iterative cloud model method with constant source function. With
this method we calculate the optical thickness τ<SUB>max</SUB>,
the Doppler width Δλ<SUB>D</SUB>, the velocity v and the source
function S describing the structure. We discuss the results of the
inversion technique and show the spatial and temporal evolution of
several physical parameters along the axes of individual mottles. The
pattern of the derived velocities as a function of space and time
(time slice images) suggests the presence of magnetic reconnection as
the driving mechanism of their formation.
---------------------------------------------------------
Title: Theoretical hydrogen population relations for horizontal
cloud-like solar structures
Authors: Tziotziou, K.; Mein, N.; Mein, P.; Heinzel, P.
2002ESASP.477..183T Altcode: 2002scsw.conf..183T
A large set of parameterized NLTE models has been computed for a 1D
horizontal cloud-like structure standing above the solar surface. The
used input model parameters are temperature, velocity, microturbulence,
electronic density and geometrical thickness of the structure. From
the output of our computations which is the hydrogen level populations
as a function of the line center optical depth, we calculate several
relations between the hydrogen population levels and the considered
electron density. These relations are important for the study of
prominence-like structures from observations.
---------------------------------------------------------
Title: The 3D Spectroscopy for Adaptive Optics (Invited Talk)
Authors: Le Coarer, E.; Mein, P.
2002ASPC..282..447L Altcode: 2002gtd..conf..447L
According to our experience of GRAF, GRIF we try to survey the art
in matter of 3D Spectrocopy behind Adaptive Optic systems for large
telescopes. The Fabry Perot Interferometer can continue to play a role
in future but some important factors as instrument must be taken into
account in order to offers the best service. We also examine other
optical mounts with slicers.
---------------------------------------------------------
Title: The MSDP of THEMIS: Capabilities, first results and prospects
Authors: Mein, P.
2002A&A...381..271M Altcode:
We present some capabilities and results of the Multi Channel
Subtractive Double Pass instrument of THEMIS. More details
and references can be found at http://www.themis.iac.es. MSDP
imaging spectropolarimetry is characterized by high space and time
resolution. The spatial resolution is close to seeing limitations,
and large areas of the Sun can be scanned within short time
intervals. In the case of THEMIS, polarization measurements are
possible. 2 Stokes parameters and 16 wavelengths of a line profile
can be observed simultaneously in a 2D field of view. The scattered
light is reduced by the use of the long predisperser as a first-pass
spectrograph. Some results are presented for fine structures of the
chromosphere and stratification of magnetic fields. The MSDP of THEMIS
is very efficient to observe fast extended events, such as eruptive
phenomena and mass ejections, in particular during coordinated campaigns
with space instruments. General outlines of the data-processing are
given. All codes are available at http://BASS2000.bagn.obs-mip.fr. In
conclusion, we mention future prospects with respect to spatial and
spectral resolution, large field-of-view, multi-line observations,
and compatibility with other THEMIS observing modes.
---------------------------------------------------------
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 D<SUB>1</SUB>
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: Ca II 8542 Å sunspot oscillations observed with THEMIS
Authors: Tziotziou, K.; Tsiropoula, G.; Mein, P.
2002A&A...381..279T Altcode:
Oscillations in the umbra and the penumbra of an isolated sunspot
located near the solar disk centre were investigated. The observations
were obtained with the Multichannel Subtractive Double Pass (MSDP)
spectrograph operating in the Ca Ii 8542 Å line and installed at
the focus of THEMIS (Tenerife). From the MSDP data, two-dimensional
intensity and Doppler shift images were computed at different
wavelengths within the line. Intensity and Doppler shift oscillations
in the umbra and the penumbra of the sunspot showing up as umbral
flashes and penumbral waves were analyzed using a 23 min time series
with a cadence of 46 s. The Ca Ii umbral flash intensity profile shows
an emission core in its blue wing. We investigate the relation between
umbral flashes and running penumbral waves by a power spectrum analysis
which shows a 6 mHz frequency for the standing umbral oscillations
(flashes) which are observed only on the upper half part of the
umbra. The running penumbral waves propagate with an average phase
velocity of 16 km s<SUP>-1</SUP> and their frequency is constant in the
penumbra and equal to 3 mHz. Although the time slice images suggest
that umbral flashes and running penumbral waves are probably due to
the same resonator, the power analysis shows no direct relationship
between the two phenomena. Based on observations made with the THEMIS
telescope operated on the island of Tenerife by CNRS-CNR in the Spanish
Observatorio del Teide of the Instituto de Astrof{ísica de Canarias.
---------------------------------------------------------
Title: Recent results from THEMIS/MSDP campaigns
Authors: Tziotziou, K.; Mein, P.
2002joso.book..129T Altcode:
We present recent results based on observations of the 2000 campaign
with the Multichannel Subtractive Double Pass (MSDP) spectrograph of the
solar telescope THEMIS. The MSDP spectrograph permits the simultaneous
recording of line profiles at every pixel of a two-dimensional solar
image. We show results based on inversion methods developed for the
study of THEMIS observations, either with the use of a non-LTE grid of
line profiles or with the use of response functions. We also discuss
results concerning sunspot observations and in particular a study
of magnetic field gradients in the umbra of sunspots and a study of
oscillatory phenomena like umbral flashes and running penumbral waves.
---------------------------------------------------------
Title: JOSO national report 2000-2001 - France
Authors: Schmieder, B.; Mein, P.; Lemaire, P.; Pick, M.; Vilmer, N.
2002joso.book...56S Altcode:
We report on the scientific advances in solar physics in France. The
French Solar community is large split in different laboratories and
observatories. We report on specific groups (THEMIS, SOHO, Nançay).
---------------------------------------------------------
Title: 2D spectroscopy and science with THEMIS
Authors: Tziotziou, K.; Mein, P.; Tsiropoula, G.; Eibe, T.
2001hell.confE..25T Altcode:
No abstract at ADS
---------------------------------------------------------
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 n<SUB>e</SUB>, and the 8542 Å Ca
II line a good determination of the electronic temperature.
---------------------------------------------------------
Title: Investigation of temperature and velocity fluctuations through
the solar photosphere with the Na I D lines
Authors: Eibe, M. T.; Mein, P.; Roudier, Th.; Faurobert, M.
2001A&A...371.1128E Altcode:
In this work we explore the diagnostic properties of the Na I D
resonance lines by calculating the response functions of their line
profiles to temperature and velocity perturbations in the atmosphere. We
propose a method to transform spectral line intensity fluctuations
measured at several wavelengths into temperature and velocity
disturbances at different height levels. Results from tests done with
several theoretical models of perturbations are discussed. Perturbations
that vary as linear functions of depth are efficiently reproduced. The
method also provides good estimations for exponential models. As an
example we present an application to solar granulation data obtained
with Multichannel Subtractive Double Pass (MSDP) spectroscopy.
---------------------------------------------------------
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: Non-LTE inversion of chromospheric {\Ca Ii} cloud-like features
Authors: Tziotziou, K.; Heinzel, P.; Mein, P.; Mein, N.
2001A&A...366..686T Altcode:
A chromospheric cloud-like feature observed in the 8542 Å {{Ca Ii}
line is studied by a two step inversion procedure which provides
estimates of its temperature, electronic density, microturbulence,
geometrical thickness and bulk velocity. The first step involves the
computation of a large grid of models by a multi-level non-LTE transfer
code which gives the {{Ca Ii} line depth-dependent mean intensity
inside an isolated, isothermal cloud lying above the chromosphere. The
second step involves the inversion of the observed profiles with the
grid of computed synthetic {{Ca Ii} profiles. A searching and matching
chi <SUP>2</SUP> algorithm is implemented followed by an interpolation
algorithm which permits a more accurate determination of the parameters
on which the profiles depend. The five grid parameters are reduced to
four by defining the emission measure from the geometrical thickness
and electronic density. We show that this inversion procedure gives
accurate results for some of our inversion parameters when dealing
with solar filaments and is complementary to a previous study of the
same object in the {{Hα }} line. The main advantages, problems and
future extension of the inversion approach are also discussed.
---------------------------------------------------------
Title: First hominid from the Miocene (Lukeino Formation, Kenya)
Authors: Senut, Brigitte; Pickford, Martin; Gommery, Dominique; Mein,
Pierre; Cheboi, Kiptalam; Coppens, Yves
2001CRASE.332..137S Altcode:
Remains of an early hominid have been recovered from four localities
in the Lukeino Formation, Tugen Hills, Kenya, in sediments aged ca 6
Ma. 13 fossils are known, belonging to at least five individuals. The
femora indicate that the Lukeino hominid was a biped when on the ground,
whilst its humerus and manual phalanx show that it possessed some
arboreal adaptations. The upper central incisor is large and robust,
the upper canine is large for a hominid and retains a narrow and
shallow anterior groove, the lower fourth premolar is ape-like, with
offset roots and oblique crown, and the molars are relatively small,
with thick enamel. A new genus and species is erected for the remains.
---------------------------------------------------------
Title: Using the Na I D resonance lines to probe the solar photosphere
Authors: Eibe, M. T.; Mein, P.; Faurobert, M.; Roudier, Th.
2001ESASP.464..199E Altcode: 2001soho...10..199E
Observational techniques in helioseismology are often based on
measurements made in the Na I D resonance lines. A good knowledge of
their spectral profiles is crucial for the purposes of calibration and
interpretation of data. Here we explore their diagnostic properties by
calculating response functions of the D<SUB>1</SUB> and D<SUB>2</SUB>
line profiles to temperature and velocity perturbations in the
atmosphere. We propose a method to transform spectral line intensity
fluctuations measured at several wavelenths into temperature and
velocity disturbances at different height levels. The possibilities
of such a procedure to trace the vertical structure of the photosphere
are discussed.
---------------------------------------------------------
Title: Solar arch filaments observed with THEMIS
Authors: Mein, P.; Briand, C.; Heinzel, P.; Mein, N.
2000A&A...355.1146M Altcode:
Arch Filaments (AF) have been observed in the Ca Ii 8542 Å line with
the THEMIS telescope in September 1998. We present a preliminary
analysis of MSDP spectro-imaging data. A cloud-model fit provides
line-of-sight velocities and a set of plausible values for the model
parameters. The high sensitivity of the filament opacity to temperature,
coupled with the rough linearity versus electronic density, shows that
this Ca Ii line should be very efficient to complement usual Hα data
for a more rigorous diagnostics. Based on observations made with the
THEMIS telescope operated on the island of Tenerife by CNRS-CNR in
the spanish Observatorio del Teide of the Instituto de Astrofisica
de Canarias
---------------------------------------------------------
Title: Association of chromospheric sunspot umbral oscillations and
running penumbral waves. I. Morphological study
Authors: Tsiropoula, G.; Alissandrakis, C. E.; Mein, P.
2000A&A...355..375T Altcode:
Observations of a sunspot region located near the center of the solar
disk were obtained on October 3, 1994, with the Multichannel Subtractive
Double Pass Spectrograph (MSDP). This instrument, operating in Hα ,
was installed at the focus of the VTT at Tenerife (Canary Islands)
and provided Hα intensity profiles at every pixel of the field of
view. Reconstruction of the Hα profile allowed the computation of
two dimensional intensity and Doppler velocity images at different
wavelengths within the line. We analyse a time series of 1 hour and
8 min, obtained with a cadence of 36 sec and investigate the relation
between umbral oscillations and running penumbral waves. The Doppler
velocity as a function of time, along radial cuts through the center of
the spot, shows several clear cases where waves that originate inside
the umbra continue to propagate in the penumbra. In one case we were
able to follow the evolution of an oscillating element for 216 sec,
from the inner part of the umbra to the penumbra and we describe the
propagation characteristics. We confirm the close association between
sunspot oscillations and running penumbral waves and suggest that they
are probably due to the same resonator.
---------------------------------------------------------
Title: Study of Chromospheric Ca II Cloud-like Structures
Authors: Tziotziou, K.; Heinzel, P.; Mein, P.; Mein, N.
2000ESASP.463..443T Altcode: 2000sctc.proc..443T
No abstract at ADS
---------------------------------------------------------
Title: Investigating the Vertical Structure of the Solar Granulation
with the Sodium D<SUB>2</SUB> Line
Authors: Eibe, M. T.; Roudier, Th.; Mein, P.; Faurobert, M.
2000ESASP.463..309E Altcode: 2000sctc.proc..309E
No abstract at ADS
---------------------------------------------------------
Title: Inversion of line profiles and solar fine structures
Authors: Mein, P.
2000ASIC..558..221M Altcode: 2000asre.conf..221M
We present some methods to analyse data cubes produced by large solar
telescopes. Applications to fine structures observed at the disc or
at the limb are briefly reviewed.
---------------------------------------------------------
Title: 3-D Magnetic Configurations for Filaments and Flares: The
Role of “Magnetic Dips” and “Bald Patches”
Authors: Aulanier, G.; Schmieder, B.; van Driel-Gesztelyi, L.; Kucera,
T.; Démoulin, P.; Fang, C.; Mein, N.; Vial, J. -C.; Mein, P.; Tang,
Y. H.; Deforest, C.
2000AdSpR..26..485A Altcode:
The 3-D magnetic configuration of a filament and of a low energy
flare is reconstructed, using linear mag- netohydrostatic (lmhs)
extrapolations. In both cases, we find observational signatures
of energy release at the locations of computed “bald patches”
separatrices, characterised by field lines which are tangent to
the photosphere.The filament was observed on Sept. 25, 1996, in Hα
with the MSDP on the German VTT, Tenerife, as well as in Si IV with
SOHO/SUMER. It is modeled as a twisted flux-tube deformed by the
magnetic polarities observed with SOHO/MDI. The shape and location of
the computed dipped field lines are in good agreement with the shape of
the filament and its feet observed in Hα. Some “bald patches” (BPs)
are present where the distribution of dips reaches the photosphere. We
show that some of the large scale field lines rooted in BPs can be
related to bright fine structures in Si IV. We propose that the plasma
there is heated by ohmic dissipation from the currents expected to be
present along the BP separatrices.The flare was observed on May 18,
1994, in soft X-rays with Yohkoh/SXT, and in Hα at Mitaka (Japan). The
magnetic field is directly extrapolated from a photospheric magnetogram
from Kitt Peak Observatory. The intersections with the photosphere of
the computed separatrices match well the bright Hα ribbons. The later
are associated to three BPs, with overlaying dipped field lines. We
show that enhanced densities are present in these dips, which can be
correlated with dark Hα fibrils.Both cases show the importance of
dipped field lines and BPs in the solar atmosphere. Energy release
via ohmic dissipation as well as reconnection along BP separatrices
is proposed to provide heating observed as UV brightenings in filament
channels and even as small flares
---------------------------------------------------------
Title: Bright Rims of Solar Prominences
Authors: Hansen, I.; Engvold, O.; Schmieder, B.; Mein, N.; Mein, P.
1999ESASP.448..491H Altcode: 1999mfsp.conf..491H; 1999ESPM....9..491H
No abstract at ADS
---------------------------------------------------------
Title: Association between Umbral Oscillations and Running Penumbral
Waves
Authors: Alissandrakis, C. E.; Tsiropoula, G.; Mein, P.
1999ESASP.448..217A Altcode: 1999ESPM....9..217A; 1999mfsp.conf..217A
No abstract at ADS
---------------------------------------------------------
Title: A Study of Hydrogen Density in Emerging Flux Loops from a
Coordinated TRACE and Canary Islands Observation Campaign
Authors: Schmieder, B.; Deluca, E.; Mein, N.; Mein, P.; Malherbe,
J. M.; Wilken, V.; Staiger, J.; Engvold, O.; Hanssen, I.
1999ESASP.448..653S Altcode: 1999mfsp.conf..653S; 1999ESPM....9..653S
No abstract at ADS
---------------------------------------------------------
Title: 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: The Role of "Magnetic Dips" and "Bald Patches" for a Filament
Observed by SOHO and GBO
Authors: Aulanier, G.; Schmieder, B.; Kucera, T.; van Driel-Gesztelyi,
L.; Démoulin, P.; Mein, N.; Vial, J. -C.; Mein, P.
1999ASPC..184..291A Altcode:
The studied filament was observed on Sept. 25, 1996, in Hα with
the MSDP on the German VTT, Tenerife, as well as in Si IV with
SOHO/SUMER. The 3-D magnetic configuration of the filament channel is
reconstructed, using linear magnetohydrostatic (lmhs) extrapolations
from a SOHO/MDI magnetogram, which is modified by a background magnetic
component constraining a twisted flux-tube. This flux-tube is deformed
by the magnetic polarities observed with SOHO/MDI. The shape and
location of the computed "dipped field lines" are in good agreement
with the shape of the filament and its feet observed in Hα. Some "bald
patches" (BPs) are present where the distribution of dips reaches the
photosphere. We find observational signatures in Si IV brightenings of
energy release at the locations of computed "bald patch separatrices",
defined by field lines which are tangent to the photosphere. We propose
that the plasma is there heated by ohmic dissipation from the expected
currents in the BP separatrices. The results show the importance of
"dipped field lines" and "bald patches" in filament channels.
---------------------------------------------------------
Title: 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: Cloud model with variable source function for solar Hα
structures. II. Dynamical models
Authors: Heinzel, P.; Mein, N.; Mein, P.
1999A&A...346..322H Altcode:
It was demonstrated in the previous paper (Paper I)that the cloud
model technique can be largely improved if one considers realistic
boundary conditions in evaluating the true form of the line source
function. For structures seen against the solar disk, the Hα line
source function is decreasing from bottom towards the top. In the
present paper we investigate the effect of Doppler brightening on Hα
source function. In frame of 1D non-LTE models it is demonstrated how
the Hα line source function is increased depending on the velocity
of the moving cloud and direction of the motion. For the same set of
cloud models as used in Paper I, we have reevaluated the variations of
the source function with optical depth including the effect of cloud
motion. The resulting curves have been approximated by a second-degree
polynomial and the respective coefficients have been subsequently
used in a modified iterative method in order to derive the cloud
model parameters. As expected, dynamical models lead to more precise
specification of these parameters, namely the optical thickness, as
compared to the static case investigated in Paper I. We have applied
this new method to MSDP observations of a dark chromospheric feature
(loop) with considerable flows.
---------------------------------------------------------
Title: Filament channel structures in a SI IV line related to a 3d
magnetic model
Authors: Kucera, T. A.; Aulanier, G.; Schmieder, B.; Mein, N.; Vial,
J. -C.
1999SoPh..186..259K Altcode:
A recent 3D magnetic model of filament support (Aulanier and Démoulin,
1998) has shown that specific morphologies derived from the model, based
on SOHO/MDI magnetograms, match quite well with the observations of a
filament observed in Hα and Ca ii lines with the German telescope VTT
in Tenerife on 25 September 1996 (Aulanier et al., 1998, 1999a). Some
predictions of this model concern the filament channel. To continue the
comparison of model and data, we have investigated the same filament
region observed in ultraviolet by the SOHO spectrometers SUMER and
CDS. The elongated EUV fine structures in the filament channel observed
in the Si iv 1393.76 Å line by SUMER have similar orientations
and locations to features predicted by the model of Aulanier et
al. (1999a). These regions are near the bases of field lines which
tangentially join to the photosphere in so called 'bald patches' and
are parts of large arcades above the filament channel. In addition,
we consider the Si iv Doppler shifts in these structures and compare
them to what might be expected from the model field structure. Our
study also suggests that the filament has a very low opacity in Si iv,
lower than that of the O v line observed by CDS.
---------------------------------------------------------
Title: A non-LTE inversion procedure for chromospheric cloud-like
features
Authors: Molowny-Horas, R.; Heinzel, P.; Mein, P.; Mein, N.
1999A&A...345..618M Altcode:
A fast inversion procedure which provides estimates of the temperature,
electronic density, microturbulence, geometrical thickness and bulk
velocity of chromospheric features, so-called “clouds”, has been
implemented. The procedure has been divided into two steps: 1) the
construction of a large grid of models by means of a multi-level non-LTE
transfer code, which solves in a fast and reliable way the radiative
transfer problem of the formation of the Hα line inside an isolated,
isothermal cloud laying above the photosphere, and 2) the implementation
of searching, matching and interpolating algorithms which yield an
inversion of the observed line profile in terms of the grid's computed
profiles. The aforementioned 5 parameters, on which the profiles depend,
can be reduced to 4 if one defines the so-called emission measure from
the geometrical thickness and electronic density parameters. We show
that this strategy yields excellent results when dealing with solar
filaments. The main advantages of this approach are also discussed.
---------------------------------------------------------
Title: 3-D magnetic configurations supporting
prominences. III. Evolution of fine structures observed in a filament
channel
Authors: Aulanier, G.; Démoulin, P.; Mein, N.; van Driel-Gesztelyi,
L.; Mein, P.; Schmieder, B.
1999A&A...342..867A Altcode:
On September 25() th 1996, a quiescent filament located near the
center disc (S2, E5) was observed on the German VTT (Tenerife)
with the MSDP instrument, in the Hα line center and wings. SOHO/MDI
line-of-sight magnetograms were co-aligned with the MSDP images, showing
the position and evolution of the lateral feet of the filament in the
vicinity of the parasitic magnetic polarities observed in the filament
channel. Using the assumptions developed in the previous papers of this
series related to the reconstruction of the 3-D magnetic configuration
of filaments, we perform “linear magnetohydrostatic” extrapolations
(taking into account the effects of plasma pressure and gravity) on the
SOHO/MDI magnetograms. The main hypothesis is the presence of a twisted
flux-tube located above the photospheric inversion line. Assuming that
the parameters of the model do not need to be significantly modified
during the evolution of the configuration for a duration of 1 day,
we have shown that the 3-D distribution of dipped field lines is well
correlated with Hα dark absorbing features in the filament channel:
the filament itself, its lateral feet and some of the surrounding dark
fibrils. In this way we confirm what was suggested in our earlier
papers, i.e. that the feet are composed of the dipped portions of
some field lines, which form a continuous pattern from the corona
to the photosphere. We propose the same explanation for the magnetic
configuration of some of the dark Hα fibrils in the channel. We show
that the plasma effects are not responsible for the existence of most
of the magnetic dips, however their inclusion helps to get a better
correspondence between the model and the observations. We find that the
average Hα Doppler velocities associated with the filament and with
the chromospheric fibrils is of the order of a few hundred m s(-1)
(though it can go locally up to 3 km s(-1) in the filament). These
upward velocities are consistent with a quasi-static evolution of
the magnetic configuration and with the support of dense plasma in
magnetic dips.
---------------------------------------------------------
Title: Gradient of the line-of-sight velocities in the dark
superpenumbral fibrils.
Authors: Tsiropoula, G.; Alissandrakis, C. E.; Mein, P.; Mein, N.
1999joso.proc..116T Altcode:
An isolated sunspot located near the centre of the solar disk was
observed on October 3, 1994. The present high resolution observations
were obtained with the Multichannel Subtractive Double Pass Spectrograph
(MSDP) operating in Hα. Two dimensional intensity and Doppler velocity
maps at several depths in the Hα line were computed. The monochromatic
intensities at two wavelengths on either side of the line are used in
terms of the photographic subtraction method expressing the "Doppler
signal" to give, under some assumptions, the velocities at different
depths in the Hα line. The values of the velocities obtained by
this method are compared to those given by the bisector method while
comparison of the velocities at different depths can give a picture
of the gradient of the velocity in the dark superpenumbral fibrils.
---------------------------------------------------------
Title: Non-LTE inversions of solar filament in Hα profiles.
Authors: Molowny-Horas, R.; Mein, P.; Mein, N.; Heinzel, P.
1999joso.proc..209M Altcode:
Results are shown of a new grid-based, non-LTE inversion procedure
which can carry out fast and accurate spectral inversions of Hα line
profiles. The code has been applied to a set of observed MSDP Hα line
profiles of a solar filament. The results of this inversion are shown
as 2-D maps of temperature, microturbulence and emission measure.
---------------------------------------------------------
Title: 3-D magnetic configurations supporting prominences. II. The
lateral feet as a perturbation of a twisted flux-tube
Authors: Aulanier, G.; Demoulin, P.; van Driel-Gesztelyi, L.; Mein,
P.; Deforest, C.
1998A&A...335..309A Altcode:
In a previous paper we have shown that a twisted flux-tube is the
most probable magnetic configuration supporting prominences. The
model interprets many observations in a natural way (in particular
the magnetic measurements in prominences and the chirality
properties). Moreover, prominence feet appear as a direct consequence
of the parasitic polarities present in the filament channel. Here we
investigate further the link between feet and parasitic polarities
by modelling explicitly these polarities. We show that the prominence
lateral feet appear naturally, above secondary photospheric inversion
lines and we describe the morphological change of feet as parasitic
polarities evolve. This approach is applied to an observed filament
in Hα with the MSDP on the German VTT (Tenerife) where SOHO/MDI
magnetograms are available. We show that the shape of the prominence
is defined by the distribution of the dips in the computed magnetic
configuration. Then we analyse the topology of the magnetic field using
the quasi-separatrix layers (QSLs) method. We describe the basic changes
in the topology as the parasitic polarities evolve, in particular
how the configuration pass from an OX to an OF topology. We find a
correspondance between the computed QSLs and some of the chromospheric
brightenings, observed around the feet of filaments in the y line (Ca
II, 8542 Angstroms). It confirms the deduced magnetic configuration
and shows that energy release is present at a low level in the complex
topology of the filament configuration.
---------------------------------------------------------
Title: 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<SUP>-1</SUP>
---------------------------------------------------------
Title: First Observations with THEMIS
Authors: Rayrole, J.; Mein, P.; Schmieder, B.
1998ASPC..155..260R Altcode: 1998sasp.conf..260R
No abstract at ADS
---------------------------------------------------------
Title: The Solar Telescope THEMIS
Authors: Arnaud, J.; Mein, P.; Rayrole, J.
1998ESASP.417..213A Altcode: 1998cesh.conf..213A
No abstract at ADS
---------------------------------------------------------
Title: Evolution of the Magnetic Field and Chromospheric Fine
Structure in a Filament Channel
Authors: van Driel-Gesztelyi, L.; Mein, P.; Mein, N.; Schmieder,
B.; Malherbe, J. -M.; Aulanier, G.; Démoulin, P.; Deforest, C.;
Staiger, J.
1998ASPC..155..321V Altcode: 1998sasp.conf..321V
No abstract at ADS
---------------------------------------------------------
Title: Umbral and Penumbral Waves in a Chromospheric Sunspot
Authors: Alissandrakis, C. E.; Tsiropoula, G.; Mein, P.
1998ASPC..155...49A Altcode: 1998sasp.conf...49A
No abstract at ADS
---------------------------------------------------------
Title: 3-D Modelling of a Filament Observed in Hα and with SOHO
Authors: Aulanier, G.; Schmieder, B.; Démoulin, P.; Mein, N.; van
Driel-Gesztelyi, L.; Mein, P.; Vial, J. C.; Deforest, C.
1998ESASP.417..217A Altcode: 1998cesh.conf..217A
No abstract at ADS
---------------------------------------------------------
Title: X-ray jets in a reversed polarity region and interplanetary
effects
Authors: Schmieder, B.; van Driel, L.; Mein, N.; Mein, P.; Willson,
R.; Raoult, A.
1998ESASP.421..157S Altcode: 1998sjcp.conf..157S
No abstract at ADS
---------------------------------------------------------
Title: 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: 3-D Modelling of a Filament Observed in Hα and with SOHO/MDI
Authors: Aulanier, G.; Démoulin, P.; van Driel-Gesztelyi, L.; Mein,
P.; Deforest, C.
1998ASPC..155..326A Altcode: 1998sasp.conf..326A
No abstract at ADS
---------------------------------------------------------
Title: Evolution of a reversed polarity active region NOAA 7912 in
the photosphere, the chromosphere and the corona.
Authors: van Driel-Gesztelyi, L.; Baranyi, T.; Mein, N.; Cader-Sroka,
B.; Rudawy, P.; Mein, P.; Rompolt, B.; Schmieder, B.; Malherbe,
J. -M.; Willson, R.; Kile, J. N.; Raoult, A.
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: Nouvelles découvertes de Vertébrés miocènes dans le
synclinal de Dera Bugti (Balouchistan, Pakistan)
Authors: Welcomme, Jean-Loup; Antoine, Pierre-Olivier; Duranthon,
Francis; Mein, Pierre; Ginsburg, Léonard
1997CRASE.325..531W Altcode:
Since Forster-Cooper in 1910, no paleontologist bas visited the
area of Dera Bugti in Baluchistan (Pakistan). In 1995 and 1996, two
small French expeditions prospected the syncline of Dera Bugti. They
established stratigraphical sections ana discovered many fossils,
mainly reptiles, and mammals. On top of the Eocene marine limestone
of the Kirthar there lies a Burdigalian marine falun. Above, about
250 m of continental marls, sands and sandstones are deposited. The
first 100 m have yielded five fossiliferous levels of MN3 b in age,
and one of MN4, surrounded by a more sandy series. The top of the
series has yielded Hipparion of the Upper Miocene.
---------------------------------------------------------
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: Evolution in Space and Time of Superpenumbral Chromospheric
Fibrils
Authors: Tsiropoula, G.; Dialetis, D.; Alissandrakis, C. E.; Mein,
P.; Mein, N.
1997SoPh..172..139T Altcode: 1997ESPM....8..139T
We have studied the spatial structure and temporal evolution of the
intensity and Doppler velocity of dark fibrils forming the superpenumbra
of an isolated regular sunspot. The observations were obtained with the
Multichannel Subtractive Double Pass (MSDP) spectrograph which operates
in Hα and is installed at the focus of the Vacuum Tower Telescope (VTT)
at Tenerife (Canary Islands). The fibril pattern shows a remarkable
stability during the period of our observations (64 min). Moreover,
almost all individual fibrils are identifiable in all frames, but they
undergo continual changes in contrast, shape and size. Investigating the
temporal evolution of intensity and velocity of individual fibrils,
fluctuations were found which have a quasi periodic behavior. As
mechanisms for these changes we may suggest (a) change of the Doppler
shift due to a wave, (b) periodic changes of the density of the Hα
absorbing material, (c) disappearance and reappearance of fibrils,
in more or less the same magnetic flux tube, at regular intervals.
---------------------------------------------------------
Title: THEMIS: Latest News
Authors: Mein, P.; Rayrole, J.
1997ASPC..118..334M Altcode: 1997fasp.conf..334M
No abstract at ADS
---------------------------------------------------------
Title: Comparison of line-of-sight velocities of chromospheric
structures derived by three different methods
Authors: Tsiropoula, G.; Christopoulou, E.; Madi, C.; Dialetis, D.;
Mein, P.; Mein, N.
1997jena.confE..61T Altcode:
We have used three different methods to derive line-of-sight velocities
in dark fibrils forming the superpenumbra of an isolated regular sunspot
located near the centre of the solar disk (NOOA/AR 7783). The present
observations were obtained on October 3, 1994. They were performed
with the Multichannel Subtractive Double Pass (MSDP) spectrograph which
operates in H-alpha and it is installed at the focus of the Vacuum Tower
Telescope (VTT) at Tenerife (Canary Islands). This instrument records
a two dimensional field of view on the solar surface with good spatial
and temporal resolution. The observations were made simultaneously in 9
wavelengts, 0.3AA apart in the H-alpha profile. At every pixel of the
2D field of view the line profile can be restored from the measured
values of the intensity in the 9 channels and a third degree spline
interpolation. These profiles were used for the computation of the
line-of-sight velocity by three different methods: (a) the Doppler
shift method, (b) the photographic subtraction method expressing the
“Doppler signal” and (c) the classical Beckers' cloud model. 2D
maps of the velocity are computed, comparison of the values derived
by the 3 different methods is performed and the conditions governing
the validity of the 3 methods are stated.
---------------------------------------------------------
Title: New Ground-Based Solar Instrumentation
Authors: Mein, P.
1997LNP...489..241M Altcode: 1997shpp.conf..241M
Solar physics requires more and more multiwavelength observations,
not only with high spatial and time resolution, but also with wide
coverage in space and time. We review briefly instruments dedicated to
the solar interior, visible layers and the corona. In addition to the
accuracy of spectroscopy and polarization measurements, we emphasize
the coverage of data sets in the k - ω diagram. New image restoration
methods are reviewed, in the context of the best compromise between
spatial resolution and isoplanetic field of view. Ambitious projects do
exist, as well as new generation telescopes under construction. Progress
in the establishment of data bases and easier data exchange between
observatories using complementary facilities look very promising for
the future.
---------------------------------------------------------
Title: THEMIS: Expected Capabilities for Coordinated Observations
Authors: Mein, P.
1997ASPC..118..320M Altcode: 1997fasp.conf..320M
Several spectroscopic modes will be available in THEMIS for coordinated
observations. They should provide high accuracy vector magnetic fields
(Multi-line Spectroscopy), fast imaging spectro-polarimetry (MSDP)
and fast magnetograms (Full Disc).
---------------------------------------------------------
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: Periodic and Non-Periodic Phenomena in a Sunspot Region
Authors: Tsiropoula, G.; Alissandrakis, C. E.; Dialetis, D.; Mein, P.
1996SoPh..167...79T Altcode:
We have studied running penumbral waves, the homogeneous Evershed
effect, and the spatial relation between intensity and Doppler velocity
penumbral features of a chromospheric sunspot. The observations were
obtained with the multichannel subtractive double-pass spectrograph
(MSDP) operating in Hα at the Vacuum Tower Telescope (VTT) installed
at Tenerife (Canary Islands). We derived intensity and Doppler velocity
maps at Hα ± 0.3 Å over a two-dimensional field of view. We have
computed the components of the velocity vector (radial, azimuthal,
vertical) as a function of distance from the center of the spot under
the assumption of axial symmetry. The results show the well-known,
from previous observations, general large-scale characteristics of the
chromospheric Evershed flow. Our measurements show that the axes along
the discrete structures, where the Evershed flow is confined, are not
spatially related to the axes along Hα ± 0.3 Å intensity features,
and we suggest that either the flow is confined in flow channels or that
it takes place along sheared magnetic field lines. We also detected,
for the first time in velocity images, running penumbral waves, which
started in the outer 0.3 of the umbral radius and propagated through
the penumbra with propagation velocities 13-24 km s<SUP>−1</SUP>. The
propagation velocity, as well as the velocity amplitude, is greater
for the waves closer to the center of the spot and diminishes as one
moves outward.
---------------------------------------------------------
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 H<SUB>alpha</SUB>_ 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: Chromospheric ejections and their signatures in X-ray observed
by YOHKOH
Authors: Schmieder, B.; Mein, N.; Shibata, K.; van Driel-Gesztelyi,
L.; Kurokawa, H.
1996AdSpR..17d.193S Altcode: 1996AdSpR..17..193S
Surges, or condensations of chromospheric material, are commonly
observed in active regions when new emerging magnetic flux (EMF)
occurs. In order to study EMF-related phenomena in the corona, observing
campaigns were organized with the Yohkoh X-ray satellite and ground
based observatories. EMFs could be detected in magnetograms made in
Potsdam and Hawaii, surge and arch filament system (AFS) events (on
Oct 7 1991, May 1 1993, respectively) with the Multichannel Subtractive
Double Pass instruments operating at Meudon and on the Canary Islands
and with the Hida telescope at Kyoto University. Bright X-ray loops
coincident with chromospheric surge activity were detected in the high
resolution Yohkoh SXT images. We also found coincident brightness
variations between an X-ray bright point (XBP) and the underlying
chromospheric plage related to EMF. We interpret the appearance of
AFS as condensation of material among magnetic field lines, the X-ray
bright points as the result of a magnetic reconnection process, and
surges as ejection of cold plasma bubbles squeezed between field lines
as a result of reconnection.
---------------------------------------------------------
Title: X-Ray Bright Point Flares Due to Magnetic Reconnection
Authors: Van Driel-Gesztelyi, L.; Schmieder, B.; Cauzzi, G.; Mein,
N.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein, P.; Staiger, J.
1996SoPh..163..145V Altcode:
Ground-based optical observations coordinated with Yohkoh/SXT X-ray
observations of an old, disintegrating bipolar active region AR NOAA
7493 (May 1, 1993) provided a multiwavelength data base to study
a flaring `active region' X-ray bright point (XBP) of about 16 hr
lifetime, and the activity related to it in different layers of the
solar atmosphere. The XBP appeared to be related to a new minor bipole
of about 10<SUP>20</SUP> Mx. Superposed on a global evolution of soft
X-ray brightness, the XBP displayed changes of brightness, lasting for
1-10 min. During the brightenings the XBP apparently had a spatial
structure, which was (tiny) loop-like rather than point-like. The
X-ray brightenings were correlated with chromospheric activity: (i)
brightenings of underlying chromospheric faculae, and (ii) appearance
of strong turbulent velocities in the arch filament system. We propose
that the XBP brightenings were due to reconnection of the magnetic
field lines (sketched in 3D) between the new bipole and a pre-existing
plage field induced by the motion of one of the new pores (v = 0.2
km s<SUP>−1</SUP>) towards the plage, and that the XBP itself was
a reconnected hot loop between them.
---------------------------------------------------------
Title: Dynamics of solar magnetic arches in the photosphere and
the chromosphere.
Authors: Mein, P.; Demoulin, P.; Mein, N.; Engvold, O.; Molowny-Horas,
R.; Heinzel, P.; Gontikakis, C.
1996A&A...305..343M Altcode:
Mass motions in chromospheric arch filaments have been observed
with imaging spectroscopy (MSDP) at the VTT telescope of the Teide
Observatory. Coordinated observations of time sequences of continuum
images were carried out at the SVST telescope of the Observatorio
del Roque de los Muchachos, which provided transverse velocities of
photospheric tracers, by "local correlation tracking." Hα profiles
along 3 arch filaments are analysed in terms of "differential
cloud MODel", to discuss the Doppler velocities of chromospheric
material. Models of ascending arches with downflows in both legs
are investigated. The gas pressure is neglected, but the free-fall
equations are integrated versus time (non-stationary case). We first
assume circular lines of force with constant radius. We can account
for chromospheric velocities, but we cannot fit the slow motion of
footpoints derived from photospheric tracers. A better agreement is
obtained by assuming lines of force with fixed footpoints and variable
radius. Typical values are: half distance between footpoints of 10 to
15Mm, upward velocity at the top of loops of 4km/s after an integration
time of 800s. The obtained values are consistent with the sizes and
the lifetime of arch filaments.
---------------------------------------------------------
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 ≡10<SUP>28</SUP>ergs cm<SUP>-3</SUP>, 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: Running Penumbral Waves in a chromospheric Sunspot
Authors: Tsiropoula, G.; Dialetis, D.; Alissandrakis, C. E.; Mein, P.
1996hell.conf...37T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Emerging Flux, Reconnection, and XBP
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Demoulin, P.;
Mandrini, C.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.; Mein,
N.; Mein, P.
1996mpsa.conf..459V Altcode: 1996IAUCo.153..459V
No abstract at ADS
---------------------------------------------------------
Title: The fine scale Structure of the velocity Field in the
chromospheric Penumbra of a solar Sunspot
Authors: Tsiropoula, G.; Alissandrakis, C. E.; Dialetis, D.; Mein, P.
1996hell.conf...32T Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Emerging flux seen by Yohkoh.
Authors: van Driel-Gesztelyi, L.; Schmieder, B.; Mandrini, C.;
Démoulin, P.; Cauzzi, G.; Hofmann, A.; Nitta, N.; Kurokawa, H.;
Mein, N.; Mein, P.
1996joso.proc..124V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Penetration of the solar granulation into the photosphere:
height dependence of intensity and velocity fluctuations.
Authors: Espagnet, O.; Muller, R.; Roudier, T.; Mein, N.; Mein, P.
1995A&AS..109...79E Altcode:
A 16-min time series of two-dimensional "Multichanel Subtractive Double
Pass" spectrograms, recorded in the NaD_2_ 5690 line, has been used to
study the vertical structure of the photosphere and, in particular,
the penetration of granules. A statistical and a morphological
investigations have been made. The 5-min oscillations have been
carefully filtered in the k-ω space. Intensity fluctuations associated
to granules disappear in a very short distance, about 60 to 90km above
the continuum level. The intensity features in the upper photosphere
are not related to the granules. The velocity fluctuations associated
to the granulation, cross the whole thickness of the photosphere. The
photosphere can thus be separated into two distinct layers, but only
for the intensity features, not for the velocity features which are
the same from the bottom to the top of the stable atmosphere. In the
lower photosphere, below 90km, only granules are detected. In the upper
photosphere, our observations suggest that the weak pattern visible
there, is turbulent in origin. In addition to this weak pattern,
bright sinking plumes have been discovered; they are associated with
strong downflows, often adjacent to strong upflows. The size of most
plumes is 1" to 2"; however the most outstanding of them may be as
large as 4". Their origin, which may be photospheric or chromospheric,
is still unknown.
---------------------------------------------------------
Title: Solar Imaging Spectroscopy: Multichannel Subtractive Double
Pass Instruments
Authors: Mein, P.
1995ASPC...71..350M Altcode: 1995IAUCo.149..350M; 1995tosm.conf..350M
No abstract at ADS
---------------------------------------------------------
Title: THEMIS IR Capabilities
Authors: Roudier, T.; Mein, P.; Rayrole, J.
1995itsa.conf..195R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: THEMIS: its capabilities and key programs
Authors: Schmieder, B.; Mein, P.
1994ESASP.373..393S Altcode: 1994soho....3..393S
No abstract at ADS
---------------------------------------------------------
Title: Dynamical Fine Structure of a Quiescent Filament
Authors: Mein, N.; Mein, P.; Wiik, J. E.
1994SoPh..151...75M Altcode:
A quiescent filament was observed near the center of the disk
(N5, W5) with the MSDP spectrograph of the 50 cm refractor of the
Pic-du-Midi Observatory on June 17, 1986. We focus our study on
the statistical moments of the Dopplershift,V<SUB>1</SUB>, and the
intensity,I<SUB>1</SUB>, at the center of a chord of the Hα profile
(±0.256 å), versus the minimum intensityI<SUB>0</SUB>. We use a
statistical model simulating a numbern<SUB>max</SUB> of threads (of
optical thicknessτ<SUB>0</SUB> and source functionS<SUB>0</SUB>), seen
over the chromosphere. The threadsj along the same line-of-sighti
are identical except for the velocityv<SUB>j</SUB> (gaussian
distributionv<SUB>0</SUB>,σ<SUB>v</SUB>). We search for the best
fit between the observed and simulated quantities:V<SUB>1</SUB>,σ
(V<SUB>1</SUB>),I<SUB>1</SUB>,σ(I<SUB>1</SUB>), and the histogram
of theI<SUB>0</SUB> values over the field of view. A good fit
is obtained with: (a) threads characterized byτ<SUB>0</SUB> =
0.2,S<SUB>0</SUB> = 0.06 (unit of the continuum at disk center), mean
upward velocityv<SUB>0</SUB> = 1.7 km s<SUP>−1</SUP> and gaussian-type
velocity distributionσ<SUB>v</SUB> = 3.5 km s<SUP>−1</SUP>. Other
possible values ofτ<SUB>0</SUB> andσ<SUB>v</SUB> are discussed; (b)
underlying chromosphere deduced from observed quiet Sun (outside the
filament) by modifying the chromospheric velocities: additional mean
upward velocity 0.7 km s<SUP>−1</SUP>, standard deviation reduced by
a factorF<SUB>c</SUB> ∼ 0.7. The results are discussed in connection
with the values deduced from prominence observations.
---------------------------------------------------------
Title: Fine Structure of Prominences and Filaments (Invited)
Authors: Mein, P.
1994scs..conf..289M Altcode: 1994IAUCo.144..289M
The author concentrates on quiescent prominences, and reviews some
recent results about resolved structures, statistical properties of
"threads", and detailed analysis of average line profiles. He mentions
magnetic field measurements and thermal problems. New magnetostatic
models are very promising. The author discusses briefly the problem
of the scale of fine structures, and suggests some directions for
further works.
---------------------------------------------------------
Title: Imaging spectro-polarimetry with THEMIS.
Authors: Mein, P.; Rayrole, J.
1994imfm.conf..116M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High resolution solar observations: Spectropolarimetry
with THEMIS
Authors: Landi Degl'Innocenti, E.; Rayrole, J.; Mein, P.
1994LNP...432..315L Altcode: 1994LNPM...11..315L
Solar observations now require many capabilities: high resolution to
detect fine flux tubes, polarization-free optics to measure the vector
magnetic field, spectral range including many lines to disentangle
thermodynamic from magnetic signatures. The site of Canary Islands,
the active optics, the Cassegrain telescope, the long spectrographs
and the universal filter of THEMIS fulfill many conditions for major
advances in the near future of solar physics.
---------------------------------------------------------
Title: The THEMIS telescope
Authors: Rayrole, J.; Mein, P.; Cavallini, F.
1994ASIC..433..507R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Dynamical Fine Structure of a Quiescent Filament
Authors: Mein, N.; Mein, P.; Wiik, J. E.
1994scs..conf..385M Altcode: 1994IAUCo.144..385M
A quiescent filament was observed in Hα by the MSDP spectrograph of
the Pic-du-Midi Observatory. The fitting by a numerical simulation
provides the velocity distribution of the "threads", and the dynamical
characteristics of the underlying chromospheric fine structures.
---------------------------------------------------------
Title: Dynamics of solar magnetic arches in photosphere and
chromosphere
Authors: Mein, P.; Mein, N.; Démoulin, P.; Gontikakis, C.; Engvold,
O.; Molowby, R.
1994smf..conf..366M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar dynamics over solar cycle 21 using sunspots as
tracers. I. Sunspot rotation.
Authors: Nesme-Ribes, E.; Ferreira, E. N.; Mein, P.
1993A&A...274..563N Altcode:
Sunspots observed on spectroheliograms have been used as tracers to
derive the rotation of the convective layers. Image-processing and
pattern recognition technique were developed to infer the position
of the tracer, thereby its motions, with a good accuracy. Some new
properties of sunspot rotation have been detected, concerning the
amplitude of the differential rotation and its variability through the
solar cycle. Comparison is made with similar studies which do not offer
the same accuracy. The results presented here give a hint of the depth
where the magnetic field of sunspots is anchored. This is of importance
for a better understanding of the origin of the differential rotation
and of the solar dynamo.
---------------------------------------------------------
Title: Turbulent power spectra of solar granulation.
Authors: Espagnet, O.; Muller, R.; Roudier, T.; Mein, N.
1993A&A...271..589E Altcode:
High resolution "Multichannel Subtractive Double Pass" spectrograms
and white light photographs have been used to compute power spectra
of the solar granulation. The 5 min oscillations have been carefully
filtered, and the influence of the variation of the mean size of
granules at the mesogranulation scale has been taken into account. <P
/>It results that both the power spectra of velocity and intensity
fluctuations, displayed in a log P - log k scale, are characteristic
of a turbulent atmosphere: they present a discontinuity at 3" =
2000 km (which corresponds to the size of a large granules) and an
energy which decreases according to the Kolmogorov -5/3 power law
in the granulation range; another discontinuity, at 1".4 = 1000 km
(which corresponds approximately to a Peclet number Pe = 1, for which
thermal diffusion and advection are of equal importance) is present in
the intensity power spectrum, which decreases with a -17/3 power law,
in the range of sizes smaller than 1".4. <P />These results indicate
that granules are turbulent eddies. They have some convective characters
(like the correlation between velocities and brightness) because they
are formed in a strongly superadiabatic atmosphere.
---------------------------------------------------------
Title: Imaging Spectroscopy of Flows in Active Regions
Authors: Mein, P.; Mein, N.
1993ASPC...46..542M Altcode: 1993mvfs.conf..542M; 1993IAUCo.141..542M
No abstract at ADS
---------------------------------------------------------
Title: THIEMIS Telescope: Prospects in High Resolution Magnetic
Field Observations
Authors: Rayrole, J.; Mein, P.
1993ASPC...46..170R Altcode: 1993IAUCo.141..170R; 1993mvfs.conf..170R
No abstract at ADS
---------------------------------------------------------
Title: Dynamical Fine Structure of Filaments and Prominences
Authors: Mein, N.; Mein, P.; Wiik, J. E.
1993ASPC...46..391M Altcode: 1993IAUCo.141..391M; 1993mvfs.conf..391M
No abstract at ADS
---------------------------------------------------------
Title: Active Region Evolution Through Coordinated Observations
Authors: Mein, N.; Mein, P.; Schmieder, B.; Engvold, O.; Molowny,
R.; Ai, G. X.
1993ASPC...46...63M Altcode: 1993mvfs.conf...63M; 1993IAUCo.141...63M
No abstract at ADS
---------------------------------------------------------
Title: Underneath coronal loops: MSDP observations coordinated with
SERTS 4 and NIXT flights.
Authors: Schmieder, B.; Mein, N.; Golub, L.; Davila, J. M.; Thomas,
R.; Brosius, J.
1992ESASP.348..257S Altcode: 1992cscl.work..257S
Ground-based coordinated observations with the multichannel subtractive
double pass spectrograph (MSDP) allowed to portray the chromospheric
intensity and velocity fields below coronal structures during recent
launchs of sounding rockets. During SERTS 4 observations (May 7,
1991), two different active regions presenting flare and filament have
been coaligned with UV structures. In July 11, 1991 (eclipse day)
large Hα ejection material in AR 6713 was detected during the NIXT
flight. Preliminary results are displayed.
---------------------------------------------------------
Title: Dynamique de la photosphère solaire: granulation,
mésogranulation, oscillations.
Authors: Espagnet, O.; Muller, R.; Roudier, T.; Mein, N.; Mein, P.
1992JAF....43...36E Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Time evolution of arch filaments
Authors: Tsiropoula, G.; Georgakilas, A. A.; Alissandrakis, C. E.;
Mein, P.
1992A&A...262..587T Altcode:
We have studied the spatial structure and the temporal evolution of the
velocity in active region arch filaments. The observations were obtained
with the Multichannel Double Pass Spectrograph operating in H-alpha
at the Pic du Midi Observatory. Line profiles were reconstructed and
monochromatic images and Doppler shift velocities were derived over a 2D
FOV. Using Beckers' (1964) cloud model we derived physical parameters,
in particular the line of sight velocity. The arches showed the
'classical' type of motion, with material moving towards the observer
near the apex and away from the observer near the footpoints. Assuming
a symmetric loop, we reconstructed the velocity vector along the arch
filaments. The results are consistent with the picture where material is
draining out of the filament, while the whole structure is ascending. In
one case we observed changes in the geometry and the velocity vector;
however, other arch filaments did not change appreciably in a time
period of about 13.5 min.
---------------------------------------------------------
Title: MSDP imaging spectroscopy for high resolution solar physics.
Authors: Mein, P.
1992ESASP.344..153M Altcode: 1992spai.rept..153M
Three facilities using Multichannel Subtractive Double Pass
spectrographs are presently operated at Meudon, Pic du Midi, Tenerife
(VTT telescope). A fourth one is expected at Tenerife (THEMIS
telescope). The imaging spectroscopy with MSDP spectrographs allows
very high spatial resolution and fast time sequences over 2D solar
targets. The author recalls some capabilities, showing that the MSDP
are very suitable for coordinated experiments between ground-based
and space observations.
---------------------------------------------------------
Title: Structure and Dynamics of Cool Flare Loops
Authors: Heinzel, P.; Schmieder, B.; Mein, P.
1992SoPh..139...81H Altcode:
MSDP observations of the 16 May, 1981 two-ribbon flare are used to
study the physical structure and the dynamical behaviour of cool flare
loops. The loops have been detected in the Hα line just after the
flare maximum and they appeared in absorption against the disk. Using
the first-order differential cloud model (DCM1) technique, we derive
empirically some basic plasma parameters at 15 points along one loop
leg. The flow velocities and the true heights have been reconstructed
with respect to a geometrical projection. Subsequently, detailed
non-LTE models of cool loops have been constructed in order to fit Hα
source function values previously derived from DCM1 analysis. It is
demonstrated that this source function is rather sensitive to the radial
component of the flow velocity (the so-called Doppler brightening)
and to enhanced irradiation of the loops from the underlying flare
ribbons. In this way, we have been able to estimate quantitatively
all plasma parameters which determine the physical structure of cool
loops (i.e., the temperature, pressure, density), as well as the
momentum-balance condition within the loops. For these dark loops we
have arrived at relatively low gas pressures of the order of 0.1-0.5
dyne cm<SUP>-2</SUP> with corresponding electron densities around
10<SUP>11</SUP> cm<SUP>-3</SUP>. Pressure-gradient forces have been
found to be of small importance in the momentum-balance equation, and
thus they cannot explain departures from a free-fall motion found in our
MSDP data analysis. We propose three possible solutions to this problem.
---------------------------------------------------------
Title: Dynamics of the solar atmosphere.
Authors: Mein, Pierre
1992soti.book..179M Altcode:
Contents: (1) Introduction. (2) Outline of the solar structure: internal
sun; solar atmosphere; solar activity. (3) One-dimension non-magnetic
model atmosphere continuum and spectral line formation: model
atmosphere; spectral intensity and source function; formation of the
continuous spectrum; formation of spectral lines. (4) Diagnostic methods
for velocity measurements: in situ measurements; indirect measurements;
intensity measurements (continuum and lines); Dopplershifts of line
profiles; averaging effects in line Doppler-shifts; instrumental
aspects: velocity measurements. (5) Rotation and convection: solar
rotation from Doppler measurements; solar rotation from tracers;
large-scale meridional circulation; convection (intermediate and small
scales). (6) Waves in the non-magnetic atmosphere: the five minutes
oscillations; the k-ω diagram; power spectrum in the k-ω diagram;
phase-lags between two lines or between intensity and Dopplershift;
mechanical energy flux; coronal heating. (7) Motions in magnetic flux
tubes and spots. (8) Velocity fields in prominences and filaments:
classification, structure; velocity measurements; steady flows;
oscillations; instabilities ("disparitions brusques", eruptions). (9)
Mass ejections - instabilities.
---------------------------------------------------------
Title: Plasma Parameters Derived from MSDP Observations of Cool
Flare Loops
Authors: Heinzel, P.; Schmieder, B.; Mein, P.
1992LNP...399..134H Altcode: 1992IAUCo.133..134H; 1992esf..coll..134H
MSDP observations of 16 May 1981 two-ribbon flare are used to study the
physical structure and dynamical behaviour of cool flare loops. The
loops have been detected in the H line just after the flare maximum
and they appeared in absorption against the disk. Using the first-order
differential cloud model (DCM1) technique, we derive empirically some
basic plasma parameters at 15 points along one loop leg. The flow
velocities and true heights have been reconstructed with respect to
a geometrical projection. Subsequently, detailed non-LTE models of
cool loops have been constructed in order to fit H source-function
values previously derived from DCM1 analysis. It is demonstrated that
this source function is rather sensitive to the radial component
of the flow velocity (the so-called Doppler brightening) and to
the enhanced irradiation of the loops from the underlying flare
ribbons. In this way, we have been able to estimate quantitatively
all plasma parameters which determine the physical structure of
cool loops (i. e. the temperature, pressure, density, etc.), as well
as the momentum-balance condition within the loops. For these dark
loops we have arrived at relatively low gas pressures of the order
of 0.1 - 0.5 dyn cm-2 , with corresponding electron densities around
1011 cm-3. Pressure-gradient forces have been found to be of small
importance in the momentum-balance equation. However, the classical
momentum equation is not capable of explaining significant departures
from a free-fall motion under the gravity force, found from our MSDP
data. We propose three possible explanations to this problem.
---------------------------------------------------------
Title: Dynamical Fine Structure of a Quiescent Prominence
Authors: Mein, P.; Mein, N.
1991SoPh..136..317M Altcode:
A quiescent prominence has been observed with the MSDP spectrograph at
the Pic du Midi Observatory. Hα profiles are obtained simultaneously in
a 2D field, allowing a statistical analysis. The standard deviations
of Doppler shifts and line widths are investigated as functions of
the line intensity. The observations are compared with numerical
simulations assuming that the prominence is made of identical
`threads', the velocity of which is distributed according to
gaussian functions. The processing of simulations is very close to
the processing of observations. The mixing by seeing effects and the
transfer of radiation across several threads along the line of sight
are considered. The results are consistent with the values derived by
Engvold et al. (1989) and Zirker and Koutchmy (1989, 1990, 1991).
---------------------------------------------------------
Title: Solar 2D spectroscopy - A new MSDP instrument
Authors: Mein, P.
1991A&A...248..669M Altcode:
The present study describes a new instrument that uses the multichannel
subtractive double pass (MSDP) technique. Its main capabilities are:
simultaneous spectro-imaging in two line profiles (medium and strong
lines), high spatial resolution in all the 2D fields, no differential
seeing effects at all wavelengths, best compromises between exposure
time and spectral resolution for lines, fast change of wavelength,
and the possibility of spectro-imaging with high spectral resolution
by successive exposures (weak lines). Either 9 or 11 channels are
recorded simultaneously in each line profile. The field size is
typically 120 x 1000 or 60 x 1000 diffraction widths of the telescope
image. The spectral resolving power is 100,000 in one exposure. The
optical design and the codes for data processing are reviewed. The
performances of the MSDP and the other 2D spectroscopy techniques are
briefly compared and possible improvements with regard to the spectral
resolution are discussed.
---------------------------------------------------------
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: Projet THEMIS.
Authors: Mein, P.; Rayrole, J.
1991sed..conf..291M Altcode:
Contents: (1) Introduciton. (2) Performances atendues: (2.1) Le
télescope sans polariseur et son analyseur. (2.2) La haute résolution
spatiale. (2.3) Spectrographe échelle et long prédisperseur. (2.4)
Caméras CCD et informatique. (3) Programmes et groupes de travail. (4)
Etat du projet.
---------------------------------------------------------
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. <P />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: Oscillations detected in C IV and Hα lines in magnetic
structures
Authors: Schmieder, B.; Thompson, W. T.; Mein, P.
1991AdSpR..11d.195S Altcode: 1991AdSpR..11..195S
Different processes involving the magnetic field and its fine
structures in the atmosphere have been proposed to explain the heating
of the corona. To help explore phenomena related to these different
processes, we will report some new observations of oscillations in fine
chromospheric structures using the MSDP spectrograph operating at Meudon
and the UVSP spectrograph aboard SMM. The temporal analysis of radial
velocities measured in the C IV line shows that no oscillations are
detectable in the transition zone. It is in good agreement with the wave
reflection model generally admitted. In the Hα line the 2 D analysis
points out that the energy observed in an unresolved frequency range
around 250 s in the chromospheric power spectrum is in fact concentrated
in structures parallel to chromospheric fibrils along which the phase
extends coherently. The oscillations appear to be transverse and might
be interpreted either by Alfvén waves generated in the chromosphere
and propagating through magnetic filamentary structures or by eigenmodes
of filamentary structures excited by chromospheric p-modes.
---------------------------------------------------------
Title: Solar Rotation Over SOLAR-CYCLE-21
Authors: Ribes, Elisabeth; Vince, Istvan; Mein, Pierre; Neto Ferreira,
Eduardo
1991LNP...380..241R Altcode: 1991sacs.coll..241R; 1991IAUCo.130..241R
Having measured the rotation rate of sunspots through solar cycle 21,
from 1977 to 1983, we have found that the mean differential rotation
averaged over this seven year record is similar to the grand average
differential rotation determined by Howard et al. (1984) over the
period 1921-1982. However, the rotation rate does change from year to
year. These changes are evidenced by a steepening or a flattening of
the mean differential rotation profile, as well as significant changes
in the equatorial rate. The presence of a time-dependent pattern of
azimuthal roils inferred from the meridional circulation pattern of
the sunspots offers a qualitative explanation of the observed rotation
rates. The amplitude of the changes is almost one order of magnitude
larger than that of the torsional oscillations found by Howard and
LaBonte (1981).
---------------------------------------------------------
Title: Dynamique de l'atmosphère solaire.
Authors: Mein, P.
1991sed..conf..263M Altcode:
Contents: (1) Introduction. (2) Conditions physiques dans l'atmosphère
solaire. (3) Diagnostic des vitesses de matière. (4) Mouvements
hydrodynamiques: rotation et convection, ondes: (4.1) Rotation
différentielle. (4.2) Circulation méridienne. (4.3) Supergranulation,
Mésogranulation, Granulation. (4.4) Ondes en l'absence de champ
magnétique. (5) Mouvements et champ magnétique: (5.1) Dynamique
des tubes de flux photosphériques. (5.2) Dynamique des taches. (5.3)
Protubérances et filaments. (5.4) Ejections de matière.
---------------------------------------------------------
Title: Chromospheric structures and prominences: dynamics and
magnetic support.
Authors: Mein, P.
1991joso.proc.....M Altcode:
The author reports on some examples of investigations concerning
chromospheric structures and prominences. Two examples refer to flows
in the vicinity of sunspots. Two other ones concern prominences,
from theoretical and observational points of view. Some instrumental
capabilities, presently available at the Canary Island Observatory,
and well suitable for the study of such objects are mentioned.
---------------------------------------------------------
Title: Current and planned facilities, Canary Islands-France
Authors: Mein, P.; Rayrole, J.
1991AdSpR..11e.151M Altcode: 1991AdSpR..11..151M
In the field of high resolution solar physics, the french telescope
THEMIS is designed to be operated at the Teide Observatory. It is a
90cm polarization-free telescope, with two 7.5m spectrographs, devoted
to magnetic field measurements, in a number of simultaneous spectral
line profiles. The instrument is under construction. The time schedule
aims at operation during the SOHO observations. <P />In addition to
this great project, a french spectro-imaging instrument is presently
working at the german VTT telescope. Using a Multichannel Subtractive
Double Pass (MSDP), it provides simultaneous images in many wavelengths
(typically 20), covering two line profiles. The 2D-character is very
valuable for coordinated observations with space probes.
---------------------------------------------------------
Title: Physical parameters of solar H-alpha absorption features
derived with the cloud model
Authors: Alissandrakis, C. E.; Tsiropoula, G.; Mein, P.
1990A&A...230..200A Altcode:
Observations of a fibril region and of an arch filament region
obtained by the Multichannel Subtractive Double Pass Spectrograph
(MSDP) operating in H-alpha at the Pic du Midi Observatory are
presented. Intensity fluctuations and Doppler shift velocities were
derived over two dimensional fields of view. The observed contrast
profiles have been matched with theoretical contrast profiles based on
the cloud model which has four parameters: the line-of-sight velocity,
the source function, the optical depth, and the Doppler width. Contour
maps and histograms of the 4 parameters were made for these regions,
and a comparison of the velocities given by 3 different methods (cloud
model, Doppler shift, and the '3-optical depths' method of Mein and
Mein, 1988) is made.
---------------------------------------------------------
Title: Oscillations detected in Hα filaments.
Authors: Schmieder, B.; Thompson, W. T.; Mein, P.
1990PDHO....7..296S Altcode:
The authors report some new observations of oscillations in filaments
observed at different positions on the disk using the MSDP spectrograph
operating at Meudon. The velocity power spectra made over whole filament
regions show a smooth maximum around 200 s period. Oscillations
are detected principally in discrete areas in the filaments and in
chromospheric fibrils, with well defined periods around 250 s and 150
s. The oscillations could be interpreted by Alfvén waves generated
in the chromosphere and propagating through magnetic filamentary
structures or by eigenmodes of filamentary structures excited by
chromospheric p-modes.
---------------------------------------------------------
Title: Spectroheliograms and motions of magnetic tracers
Authors: Mein, P.; Ribes, E.
1990A&A...227..577M Altcode:
The series of spectroheliograms of the Paris-Meudon Observatory,
starting in 1919, is a powerful tool for studies of the solar cycle
and the solar dynamo. This paper describes a method of data processing
which corrects most of the predictable distortions by the use of
Fourier expansions of the shape of the limb. The drifts of magnetic
tracers (spots and faculae in the case of K1v spectroheliograms) are
computed automatically. The accuracy is checked by some comparisons
with results published by the Debrecen Observatory. In most cases,
the departures are 0.1 or 0.2 heliographic degree, and comparable to
the spatial resolution of the spectroheliograms.
---------------------------------------------------------
Title: Dynamical Structure of a Quiescent Prominence
Authors: Mein, P.; Mein, N.; Schmieder, B.; Noëns, J. C.
1990LNP...363..252M Altcode: 1990doqp.coll..252M; 1990IAUCo.117..252M
A statistic analysis of H profiles in a quiescent prominence is
consistent with the superposition of individual velocity structures
(typically 10), with standard deviation ~ 15 km s-1.
---------------------------------------------------------
Title: Hα diagnostics of 16 May 1981 flare loops.
Authors: Heinzel, P.; Mein, P.; Schmieder, B.
1990PDHO....7..272H Altcode:
MSDP observations (Meudon) of 16 May 1981 post-flare loops are used
to derive the hydrogen plasma parameters in flare loops. The authors
compare two recently developed methods: a differential cloud model
and a probabilistic transfer technique.
---------------------------------------------------------
Title: Evolution of Fine Structures in a Filament
Authors: Schmieder, B.; Mein, P.
1990LNP...363..235S Altcode: 1990doqp.coll..235S; 1990IAUCo.117..235S
A quiescent filament observed in June 1986 underwent a slow Disparition
Brusque which lasted 4 days. Here, we focus our study on the dynamical
behaviour of the fine structures ( Full-Width Half-Max ~ 350 km) in
this filament which were observed at Pic du Midi with the Multi-Channel
Subtractive Double Pass (MSDP) spectrograph during a period of 30
minutes. We observed no changes in intensity during this period, but
we did observe changes in the velocity field with no correlation from
one minute to the next. High velocities were detected at the footpoints
where the filament is anchored in the photosphere , of the same order
than those observed at the boundaries of the supergranules (between
±10 km s-1). To explain these observations we suggest a spicule-like
model which supplies material to the prominence.
---------------------------------------------------------
Title: 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: Prospects of MSDP observations: high spatial resolution and
adaptive optics
Authors: Mein, P.
1989hsrs.conf..195M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: High resolution observations with THEMIS: prospects in magnetic
field observations
Authors: Mein, P.
1989hsrs.conf...12M 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: Evolution of Fine Structures in a Filament
Authors: Schmieder, B.; Mein, P.
1989HvaOB..13...31S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Echelle grating spectrograph for LEST. Constraints and
tentative scheme.
Authors: Mein, P.
1989egsl.book.....M Altcode:
The large aperture of LEST combined with adaptive optics should
lead to a great number of new results in solar physics. The author
reviews briefly the requirements in the case of the echelle grating
spectrometer. Then he analyses the capabilities and limitations of
some special designs and observing modes, proposes a tentative optics
and lists some available operating modes.
---------------------------------------------------------
Title: A surge in the chromosphere and the transition region:
velocities and microturbulence.
Authors: Mein, P.; Schmieder, B.; Tandberg-Hanssen, E.
1989sasf.confP.223M Altcode: 1989IAUCo.104P.223M; 1988sasf.conf..223M
Simultaneous observations of a surge in Hα and C IV are analysed in
terms of Doppler velocities and "microturbulence". The behaviour of both
quantities suggests strong velocity shears with small spatial scales.
---------------------------------------------------------
Title: Chromospheric eruptions, Jan - Dec 1989.
Authors: Cailloce, E.; Mein, N.; Lantos, P.
1989QBSA...31....1C Altcode:
This report shows, in a chronological order, a list of all reported
flare events whatever their importance.
---------------------------------------------------------
Title: Dynamical Structure of a Quiescent Prominence
Authors: Mein, P.; Mein, N.; Schmieder, B.; Noens, J. C.
1989HvaOB..13..113M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Chromospheric ejections associated with type III radio-bursts.
Authors: Mein, N.; Mein, P.
1989sasf.confP.181M Altcode: 1988sasf.conf..181M; 1989IAUCo.104P.181M
The authors study the dynamics of an Hα absorbing structure associated
with a type III radioburst. They use a "Differential Cloud Model"
to analyse the observed line profiles, in order to determine radial
velocity and microturbulence (or shear) as functions of time. The
authors assume that the material is flowing inside magnetic flux tubes,
with a given velocity distribution. They analyse the motions in a
phase-diagram (position x, velocity V). The evolution of velocity and
microturbulence is compared to the observations. The model accounts
qualitatively for the evolution of velocity, and qualitatively for
the decrease of microturbulence.
---------------------------------------------------------
Title: Differential cloud models for solar velocity field measurements
Authors: Mein, P.; Mein, N.
1988A&A...203..162M Altcode:
The analysis of velocity fields in solar ejecta is an important
step in understanding mechanisms of acceleration and energy
transfer. Unfortunately, Beckers' cloud model is not quite valid
in the case of fast mass flows observed on the disk, because of
the fluctuations of the chromospheric background in active regions,
and because of strong velocity gradients along the line of sight. The
authors propose two kinds of differential cloud models (first order and
second order) to determine some parameters characterizing the velocity
field, in spite of these difficulties. They discuss an example of a
solar ejection observed at Meudon observatory.
---------------------------------------------------------
Title: An example of the association of X-ray and UV emission with
H-alpha surges
Authors: Schmieder, B.; Mein, P.; Simnett, G. M.; Tandberg-Hanssen, E.
1988A&A...201..327S Altcode:
From H-alpha UV, and X-ray data, the nature of a well-observed
surge on November 12, 1980 has been studied to try to understand the
relationships between the mechanical motions and the high-temperature
emissions. The cool (H-alpha) and the hot (O v) parts of the surge
plasma both show velocities in the range of 100-120 km/s. The kinetic
and potential energies of the surge are two orders of magnitude
higher than the radiative energy. The observations suggest that the
surge occurs in open structures parallel to one leg of a large scale
coronal magnetic loop. The energy is released principally in the open
structure (surge) and only a small amount heats the coronal loop (X-ray
signature). This energy division should probably not be treated as a
general characteristic of surge events. Different events are expected
to exhibit a different energy balance, and this can account for the
lack of a consensus in the previous literature regarding surge/X-ray
associations.
---------------------------------------------------------
Title: The Evershed flow in the solar photosphere, chromosphere and
chromosphere-corona transition region
Authors: Alissandrakis, C. E.; Dialetis, D.; Mein, P.; Schmieder,
B.; Simon, G.
1988A&A...201..339A Altcode:
The authors have studied the height dependence of the characteristics
of the Evershed flow in the photosphere, chromosphere and
chromosphere-corona transition region. The Multichannel Subtractive
Double Pass Spectrograph was used to obtain line of sight velocity maps
in Hα, the Meudon magnetograph for mapping the photospheric velocity
and magnetic field and the Ultraviolet Spectrometer and Polarimeter on
the Solar Maximum Mission spacecraft for line-of-sight velocities in C
IV, in sunspot regions. The observations are practically simultaneous in
the three atmospheric levels and cover three consecutive days (Sep 28,
29 and 30, 1980). The emphasis was on the large scale, quasi-stationary
characteristics of the flow.
---------------------------------------------------------
Title: Photospheric-induced destabilization and ejection of prominence
material
Authors: Raadu, M. A.; Schmieder, B.; Mein, N.; Gesztelyi, L.
1988A&A...197..289R Altcode:
The sequence of events leading up to prominence activation in two
different cases is studied. In one case, observed on September 3, 1980,
strong velocity shears were produced indicating filament twisting. In
the other case, observed on June 22, 1980, activation results in the
ejection of prominence material. The paper presents new evidence for a
common initial triggering mechanism, the birth or motion of pores at one
end of the activated filament sections. This is taken as an indication
of emerging magnetic flux and current induction in the filaments. The
difference in the final results is partly due to the different ambient
magnetic field structures. In particular in the case leading to material
ejection there is a subsequent associated flare occurred indicating
the storage of magnetic energy in the region. Models are proposed for
the two sequences of events, clarifying the underlying similarities
and interpreting the distinct features of the two sets of observations.
---------------------------------------------------------
Title: Two-dimensional spectroscopy of the Sun in Hα.
Authors: von Uexküll, M.; Kneer, F.; Mein, P.
1988AGAb....1...11V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Variations of the Solar Limb Brightness with the Oscillations
Authors: Schmieder, B.; Mein, P.
1988IAUS..123..429S Altcode:
The aim of this work is to compute the amplitude of the limb darkening
fluctuations due to oscillations in order to compare it with the
observations made with the heliometer at the Pic du Midi (Rösch
and Yerle 1983 - 1984). It is shown that 5 min oscillations lead to
variation in the brightness gradient of less than 2%.
---------------------------------------------------------
Title: Environment and dynamics of a prominence observed at Pic
du Midi.
Authors: Noëns, J. C.; Schmieder, B.; Mein, P.
1988dssp.conf..177N Altcode:
Simultaneous observations were made at Pic du Midi using the 20 cm
Coronograph and the Multichannel Subtractive Double Pass spectrograph
operating in the "Coupole Tourelle". The prominence observed on June
17, 1987 is composed of three principal vertical structures 50000 km
high with faint material connecting then. A coronal cavity is visible
above the prominence. The dynamics of this prominence in Hα is large,
horizontal circulation is observed. Images in Hα versus time show
a slow evolution in the general shape with an exchange of material
between the vertical structures.
---------------------------------------------------------
Title: Mass ejections in the low corona: microturbulence and type
III associations.
Authors: Mein, Pierre; Mein, Nicole
1988sscd.conf..514M Altcode:
Mass ejections visible in Hα have often been correlated with type III
radio bursts. Among the possible mechanisms which can account for the
radio emission, energy transfer from turbulence or velocity shears have
been suggested. The authors analyse velocity fields inside the ejecta
by using two "Differential Cloud Models" derived from the well-known
Beckers model. They apply these models to a sample of ejection observed
with the MSDP of the Meudon Solar Tower. They derive the time evolution
of radial velocities and microturbulence at the edges of the structure
as well as the range of radial velocities along the line of sight in
the middle part.
---------------------------------------------------------
Title: Velocity shear and microturbulence in solar filaments a
differential cloud model.
Authors: Mein, P.; Schmieder, B.
1988dssp.conf...17M Altcode:
The authors analyse the time sequence of an active region
filament observed at the MSDP of the Meudon Solar Tower. They use a
"differential cloud model" which is well suited to the interpretation
of H<SUB>α</SUB> profiles with an inhomogeneous chromospheric
background. A previous model (Schmieder et al. 1985) suggesting twisting
motions of magnetic ropes is confirmed.
---------------------------------------------------------
Title: Chromospheric eruptions, Jan - Dec 1988.
Authors: Cailloce, E.; Mein, N.; Lantos, P.
1988QBSA...30....1C Altcode:
This report shows, in a chronological order, a list of all reported
flare events whatever their importance.
---------------------------------------------------------
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. <P />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: 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: 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: The Evershed flow in the solar photosphere, chromosphere and
chromosphere-corona transition region.
Authors: Alissandrakis, C. E.; Dialetis, D.; Mein, P.; Schmieder,
B.; Simon, G.
1987PAICz..66..147A Altcode:
The authors have studied the height dependent characteristics of the
Evershed flow in the photosphere, chromosphere and chromosphere-corona
transition region.
---------------------------------------------------------
Title: Photospheric Induced Destabilization and Ejection of Prominence
Material
Authors: Raadu, M. A.; Schmieder, B.; Mein, N.; Gesztelyi, L.
1987HvaOB..11..105R Altcode:
The cause of the sudden activation of solar prominences is not
clear. The authors present observations of two cases which were preceded
by the emergence and motion of pores (new flux) in the near vicinity
of the filaments, which seem to be closely related to the process which
triggered the filament destabilization. These observations may be well
described by a theoretical model in which the new flux interacts with
the older "stable" magnetic field.
---------------------------------------------------------
Title: Dynamics of solar filaments. V - Oscillations in the H-alpha
and 1548 A C IV lines
Authors: Malherbe, J. M.; Schmieder, B.; Mein, P.; Tandberg-Hanssen, E.
1987A&A...172..316M Altcode:
Using the Multichannel Subtractive Double Pass Spectrograph operating in
the Meudon solar tower and the Ultraviolet Spectrometer and Polarimeter
aboard the Solar Maximum Mission satellite, the authors analyze by
Fourier transform technique time sequence observations of filaments in
both the Hα line and in the 1548 Å C IV line. The Hα data confirm
previous findings that there are no oscillations at the location of
the filament in the observed range 1 - 10 mHz. In the C IV line the
authors observe power in some parts of the filament where a steady
velocity gradient is present, e.g. in the footpoints. The energy is
probably due to convective motions rather than pressure oscillations.
---------------------------------------------------------
Title: Environment and Dynamics of a Prominence Observed at Pic-Du
Authors: Noens, J. C.; Schmieder, B.; Mein, P.
1987dssp.work..177N Altcode: 1987ASSL..150..177N
No abstract at ADS
---------------------------------------------------------
Title: Joint Discussion on Topics of Sessions 9 and 10
Authors: Mein, P.; Roberts, B.
1987rfsm.conf..292M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: La physique solaire et les performances de THÉMIS.
Authors: Mein, P.
1987JAF....29...14M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Chromospheric eruption, Jan - Dec 1987.
Authors: Cailloce, E.; Mein, N.; Lantos, P.
1987QBSA...29....1C Altcode:
This report shows, in a chronological order, a list of all reported
events whatever their importance.
---------------------------------------------------------
Title: On the onset of eruptive prominences and coronal transients.
Authors: Simon, G.; Mein, N.; Schmieder, B.; Tandberg-Hanssen, E.;
Wu, S. T.
1987PAICz..66..211S Altcode: 1987eram....1..211S
During the Maximum Year, preflare and preeruptive phenomena have
been observed which give a new idea on the association of eruptive
prominences and coronal transients.
---------------------------------------------------------
Title: Surges as tracers of magnetic lines.
Authors: Schmieder, B.; Mein, P.; Martres, M. J.; Simnett, G.;
Tandberg-Hanssen, E.
1987PAICz..66..109S Altcode: 1987eram....1..109S
The authors focus their study to chromospheric mass ejecta of
cool material visible in Hα and occurring, with or without any
flare. Associated with the events are either X ray emission or type
III bursts.
---------------------------------------------------------
Title: Velocity Shear and Microturbulence in Solar Filaments
Authors: Mein, P.; Schmieder, B.
1987dssp.work...17M Altcode: 1987ASSL..150...17M
No abstract at ADS
---------------------------------------------------------
Title: On the existence of oscillations in solar filaments observed
in H<SUB>&</SUB>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<SUB>&</SUB>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: Filament eruption connected to photospheric activity.
Authors: Simon, G.; Gesztelyi, L.; Schmieder, B.; Mein, N.
1986NASCP2442..229S Altcode: 1986copp.nasa..229S
Two cases of activation of filaments that occured in regions of
intense magnetic activity was studied. The simultaneous observations
from Debrecen Observatory (white light and H alpha filtergram), and
from Meudon Observatory (magnetogram, MSDP dopplergram and intensity
maps in H alpha) gave a complementary set of data from which can be
produced evidence of the influence of the photospheric magnetic field
on the destabilization process of the filaments. On June 22, 1980,
the eruption of the filament is associated with the motion of pores,
which are manifestations of emerging flux knots. On September 3, 1980,
the twisting motions in the filament are associated to the birth of
a pore in its neighborhood. These observations are discussed.
---------------------------------------------------------
Title: Material ejecta in a disturbed solar filament
Authors: Raadu, Michael A.; Malherbe, Jean-Marie; Schmieder, Brigitte;
Mein, Pierre
1986STIN...8722594R Altcode:
H alpha observations, using a multichannel subtractive double pass
spectrograph were made of an active region filament which undergoes
a sudden disappearance. The period of observation was from 10:45 UT
to 13:30 UT on 22 June, 1981. Velocity and intensity fluctuations
in H alpha were measured. The proper motions of ejecta were followed
allowing their trajectories and vector velocities to be determined. To
model the dynamics of ejecta, models using thermal or magnetic driving
forces are compared. The most promising model explains the motion as
the consequence of magnetic stresses acting on an isolated magnetized
plasmoid in a diverging flux tube.
---------------------------------------------------------
Title: The effect of solar oscillations on the brightness of the limb
Authors: Schmieder, B.; Mein, P.
1986A&A...161....7S Altcode:
Using the realistic atmosphere model VALC, and assuming a spherical
geometry, the intensity of the solar limb is calculated, and measured
amplitude fluctuations are compared with those expected due to
oscillations. In the model, the atmosphere is perturbed successively
by density and temperature fluctuations of amplitude smaller than the 6
percent limiting value, and the perturbations are defined by exponential
laws corresponding to propagating or evanscent waves. It is shown that
5-minute oscillations lead to variations in the brightness gradient of
less than 2 percent. Limb brightness fluctuation amplitudes observed
with the Pic du Midi heliometer (Yerle, 1981) show peaks of 10 percent
which have too high a value to be explained by solar wave theory.
---------------------------------------------------------
Title: Unstable Chromospheric Dark Features and Type-Iii Bursts
Association
Authors: Chiuderi-Drago, F.; Mein, N.; Pick, M.
1986SoPh..103..235C Altcode:
The temporal association between the kinematic parameters of
chromospheric dark features (DF) and the production of radio type-III
bursts is investigated during a period of five months. The Doppler
shifts inside six different DF are measured by means of the Meudon
Multichannel Subtracting Double Pass Spectrograph (MSDP) during periods
of some minutes around 24 type-III bursts. The position of the radio
bursts has been checked to be associated with the same active region
observed by MSDP, by using the Nançay Radioheliograph.
---------------------------------------------------------
Title: Chromospheric eruption, Jan - Dec 1986.
Authors: Cailloce, E.; Mein, N.; Lantos, P.
1986QBSA...28....1C Altcode:
This report shows, in a chronological order, a list of all reported
events whatever their importance.
---------------------------------------------------------
Title: First evidence of a large-scale circulation in the solar
convection zone
Authors: Ribes, E.; Mein, P.
1986ASIC..169..103R Altcode: 1986ssds.proc..103R
No abstract at ADS
---------------------------------------------------------
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: A large-scale meridional circulation in the convective zone
Authors: Ribes, E.; Mein, P.; Mangeney, A.
1985Natur.318..170R Altcode:
Many attempts have been made to detect, at the solar photospheric level,
large-scale motions related to the Sun's global convection and dynamo
(see ref. 1). Because these motions are likely to be influenced by solar
rotation, one might expect that they would take the form of `bananas'
aligned with the solar rotation axis<SUP>2</SUP>, as a result of the
Taylor-Proudman constraint. The Paris observatory has one of the longest
series of spectroheliograms, dating back to 1919. In view of the current
interest in the history of solar activity, we have started to digitize
the collection<SUP>3</SUP>. This allows us to measure rotational rate
and meridional drift for individual sunspots with an accuracy of a
few ni s<SUP>-1</SUP> for the best seeing conditions at Meudon. A new
phenomenon, which may lead us drastically to revise our ideas on the
large-scale convection of the Sun, can immediately be seen. Newly-born
sunspots trace a roughly axisymmetric meridional circulation, in the
form of four zonal bands, with relatively large velocity amplitude. If
these drifts are assumed to trace fluid motions at some level in the
solar envelope, the resulting circulation pattern cannot be associated
with the `banana' cells mentioned above. We report here results based
on two sets of data; one involves a detailed analysis of two periods,
each covering five solar rotations while the other is essentially
qualitative and results from eye-estimates of the spot meridional
drifts over much longer time sequences.
---------------------------------------------------------
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: The Evershed flow as a steady-state homogeneous phenomenon
Authors: Dialetis, D.; Mein, P.; Alissandrakis, C. E.
1985A&A...147...93D Altcode:
The present observations of photospheric and chromospheric line-of-sight
velocity, as well as the photospheric magnetic field, facilitate the
comprehensive study of the Evershed (1909) flow, with emphasis on large
scale, quasi-stationary characteristics of the flow and its association
with the topology of the magnetic field. A multichannel subtractive
double pass spectrograph was used to obtain line-of-sight velocity
maps in H-alpha, together with the Meudon magnetograph. Computations
are made for the components of the velocity vector as a function of
distance from the center of the spot, under the assumption of axial
symmetry. The radial component is the dominant one in both chromosphere
and magnetosphere. The present analysis of the magnetograms, using
current-free and force-free models, indicates that the velocity maximum
occurs in regions where the magnetic field is almost horizontal in both
layers; the results are judged to appear consistent with subsonic flow
in magnetic flux tubes.
---------------------------------------------------------
Title: Ejection of Chromospheric Material Associated with Injection
of Electrons in the Solar Corona
Authors: Mein, N.; Avignon, Y.
1985SoPh...95..331M Altcode:
Observations of a type III radio event and of concurrent Hα
absorbing features are related. They were obtained with the
Nançay Radioheliograph and the Multichannel Subtractive Double
Pass spectrograph operating in Hα at Meudon. We are looking for the
signature at chromosphere levels of the acceleration of the elctron
beams triggering the type III bursts. Some promising results are pointed
out: the relationship between velocities in Hα and the occurrence
of the type III bursts, the shape of Hα line which reveals turbulent
motions, the presence of parasitic magnetic polarity and the probable
existence of a shock wave. A schematic scenario of the phenomenon is
proposed, taking into account the observational constraints.
---------------------------------------------------------
Title: Mass motions in Hα absorbing structures of the solar
chromosphere.
Authors: Mein, P.; Malherbe, J. M.; Mein, N.; Mouradian, Z.;
Schmieder, B.
1985MPARp.212..316M Altcode:
Two examples of Hα absorbing structures have been observed with the
Multichannel Subtractive Double Pass spectrograph at the turret dome
(Pic du Midi) and at the solar tower (Meudon). In both cases, 9 points
of the line profile are measured simultaneously in a 2D-field of view.
---------------------------------------------------------
Title: 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.
---------------------------------------------------------
Title: Spectrographie des structures fines solaires. Un grand pas
réalisé au Pic-du-Midi.
Authors: Mein, P.
1985LAstr..99..167M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Search for Giant Convective Cells from the Analysis of Meudon
Spectroheliograms
Authors: Ribes, E.; Mein, P.
1985LNP...233..282R Altcode: 1985hrsp.proc..282R
The results of digitizing the K IV spectroheliograms (violet wing
of the Ca II line) of the Meudon Collection are discussed. Sunspots
are found to rotate faster than old facula by two percent, and it is
concluded that they can be tracers of angular momentum transport at
the very beginning of their emergence. Afterwards, they become detached
from the depth of anchorage and float with the photospheric plasma. A
complex meridional circulation, analogous to zonal belts observed
on the major planets, has been detected which changes throughout the
solar cycle. The existence of two active longitudes together with the
meridional circulation pattern suggests that the solar dynamo works
as a nonlinear oscillator.
---------------------------------------------------------
Title: Themis solar telescope
Authors: Mein, P.; Rayrole, J.
1985VA.....28..567M Altcode:
Thémis is a 90cm solar telescope expected to be constructed at the
Teide Observatory by 1990 for polarisation analysis simultaneously
over a broad spectral range.
---------------------------------------------------------
Title: Differential Rotation and Large Scale Convection
Authors: Ribes, E.; Mein, P.
1985spit.conf..212R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Chromospheric eruption, Jan - Dec 1985.
Authors: Cailloce, E.; Mein, N.; Lantos, P.
1985QBSA...27....1C Altcode:
This report shows, in a chronological order, a list of all reported
events whatever their importance.
---------------------------------------------------------
Title: New instrumentation for diagnostics of chromospheric fine
structure and dynamics: MSDP spectrographs; capabilities and latest
results.
Authors: Mein, P.
1985cdm..proc..297M Altcode:
High spatial resolution can be achieved in bidimensional spectroscopy by
"Multichannel Subtractive Double Pass" spectrographs. The capabilities
of such instruments are briefly reviewed, as well as the processing
of data, the latest results and the plans for the future.
---------------------------------------------------------
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.
---------------------------------------------------------
Title: Bright Points in H Wings and Mass Flows in the Solar
Chromosphere
Authors: Mein, P.; Malherbe, J. -M.; Mouradian, Z.; Mein, N.;
Schmieder, B.; Muller, R.
1985LNP...233..203M Altcode: 1985hrsp.proc..203M
Many mass flows in the chromosphere are physically connected with
bright photospheric points. Bidimensional spectroscopy with high
spatial resolution is very well suited for the study of both kinds
of structures. The authors give some preliminary results derived from
recent observations of the MSDP at the Pic-du-Midi.
---------------------------------------------------------
Title: Mass fluxes and magnetic structures in the chromosphere and
the transition region; canopies.
Authors: Mein, P.; Malherbe, J. -M.; Schmieder, B.; Simon, G.;
Tandberg-Hanssen, E.
1985cdm..proc..206M Altcode:
Preliminary results of applying a model of canopy-type magnetic
lines to account for observed mass fluxes in the chromosphere and
transiton region are presented. A set of center-to-limb data obtained in
H-alpha and C IV, and to which the model is applied, is reported. The
C IV line is assumed to form everywhere at the same height, and the
H-alpha formation height is derived by assuming that the absorption
coefficient is proportional to the local density. The density ratio
between H-alpha and C IV levels is taken to be 100. From the results,
it is concluded that the model accounts for the low ratio of radial
velocities C IV/H-alpha at r = 0, the increase of H-alpha velocity
near the limb, and the general center-to-limb behavior in both lines.
---------------------------------------------------------
Title: Recent Progress in the Physics of Solar Prominences
Authors: Ribes, E.; Mein, P.; Malherbe, J. M.; Schmieder, B.
1985spit.conf..467R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Dynamic evolution of recurrent mass ejections observed in
Hα and C iv lines
Authors: Schmieder, B.; Mein, P.; Martres, M. J.; Tandberg-Hanssen, E.
1984SoPh...94..133S Altcode:
During a coordinated SMY program, the consecutive formation of two new
active centers merging together within AR 2646 was observed from 28
August, to 5 September, 1980. The two preceding spots compressed an
inverse polarity spot on 1 September 1980, causing recurrent ejecta
of matter with time intervals around 10 min. The observations of the
MSDP spectrograph operating in Hα at the Meudon Solar tower and of
the UVSP spectrometer on SMM in the CIV 1548 Å line show that cold
and hot material had the same projection, although the upward CIV
velocity structure was more extended than the Hα one. We present
evidence that observed contrasts of the Hα absorbing structure
can be interpreted in terms of a dynamic `cloud model' overlying
the chromosphere. Hα matter follows a magnetic channel with upward
velocity around 20-30 km s<SUP>−1</SUP> in the first phase of the
event and with downward velocity (∼ - 40 km s<SUP>−1</SUP>) in the
second phase. The stored energy is not sufficient to trigger a flare,
nor even to propulse matter along the full length of an arch, because
of the periodic reorganisation of the magnetic field.
---------------------------------------------------------
Title: Dynamics of solar filaments. III - Analysis of steady flows
in H-alpha and C IV lines
Authors: Schmieder, B.; Malherbe, J. M.; Mein, P.; Tandberg-Hanssen, E.
1984A&A...136...81S Altcode:
A statistical analysis of intensities and radial velocities of
several solar plage filaments (i.e. prominences seen on the solar
disk) observed at disk center is presented. Intensity and radial (=
vertical) velocity maps were derived from simultaneous 2D measurements
of the H-alpha chromospheric line with the Multichannel Subtractive
Double Pass spectrograph operating on the Meudon solar tower, and also
obtained from 2D recordings of the C IV transition-zone line (1548 A)
with the UV Spectrometer and Polarimeter aboard the Solar Maximum
Mission satellite. A good correlation (around 0.5) is found between
intensities in both lines, as well as between velocities. Persistent
upflows are measured in both lines at the filament location. The mean
vertical velocities are respectively 0.5 km/s in H-alpha and 5.6 km/s
in C IV. The analysis of mass fluxes suggests that C IV upflows occur
in the transition region around prominences rather than below, in the
chromosphere-corona transition zone.
---------------------------------------------------------
Title: Preflare Activity of Solar Prominences
Authors: Simon, G.; Mein, N.; Mein, P.; Gesztelyi, L.
1984SoPh...93..325S Altcode:
The preflare activity of a plage filament is analysed from Hα
observations made with the Multichannel Subtractive Double Pass
Spectrograph (MSDP) of the Meudon Solar Tower. The June 22, 1980
event is studied and interpreted in terms of preflare heating of a
filament, connected to the rise of emerging flux, and the relative
approach of pores of different magnetic polarity, prior to the onset
of a two-ribbon flare.
---------------------------------------------------------
Title: Oscillations and stationary motions in filaments
Authors: Schmieder, B.; Malherbe, J. M.; Mein, P.; Tandberg-Hanssen, E.
1984MmSAI..55..325S Altcode:
Observation of oscillations in filaments, which are cold magnetic
structures suspended in the corona, are used to test theories of
coronal heating by acoustic waves high in the atmosphere. Long lived
stationary motions observed in filaments suggest exchanges of material
between them and the surrounding corona. A coupling between upflows in
filaments and subphotospheric convective motions, dragging the field
lines of the prominence magnetic support, is possible.
---------------------------------------------------------
Title: Dynamical behaviour of the corona in association with radio
emissions
Authors: Trottet, G.; Avignon, Y.; Kerdraon, A.; Mein, N.; Pick, M.
1984AdSpR...4g.271T Altcode: 1984AdSpR...4..271T
From a combined analysis of radioheliographic observations and white
light images of the Corona, it is shown that metric continua onsets or
enhancements are associated with a great variety of dynamical changes
of the Corona. It is found that if the most spectacular radio bursts
(type IV) are associated with mass ejection transients, the more common
noise storm onsets or enhancements are systematically associated
with coronal changes which are not necessarly mass ejections. <P
/>Simultaneous observations of Radio type III bursts and Hα mass
ejecta are related. We are looking to the signature at low levels
in the corona of the electron beam acceleration triggering type III
bursts. The results deal with the relationship between the type III
occurrence and optical features : the presence of velocities in Hα,
the shape of Hα line which reveals trubulent motions and the probable
existence of a shock wave.
---------------------------------------------------------
Title: Etude de la rotation des traceurs magnétiques observés sur
les spectroheliogrammes K IV (Collection de Meudon) - Résultats
préliminaires.
Authors: Ribes, E.; Mein, P.
1984cms..conf..369R Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Flare build-up study - Homologous flares group - Part I
Authors: Martres, M. -J.; Woodgate, B. E.; Mein, N.; Mouradian, Z.;
Rayrole, J.; Schmieder, B.; Simon, G.; Soru-Escaut, I.
1984AdSpR...4g...5M Altcode: 1984AdSpR...4....5M
According to the definition of the homology (optical) kept in reference,
the homologous flares (HFl) may be observed wherever flares occur. The
supposed supplementary preflaring conditions to have HFl may be either
that the preflaring conditions have not been destroyed by the first
flare (and then what mechanism has stopped the first and triggered the
second ?) or that the preflaring conditions have been destroyed and
rebuilt (and then, how ?). The analysis of data related to some selected
active regions AR by the members of the working group, and the earlier
works on HFl, may be used simultaneously to investigate the differences
between one set of HFl and the others, the location of their sites and
the evolution of HFl productive AR. This study brings the appearance of
new footpoints from one flare to the following, the behaviour of cool
arches (surging arches) leading to information on the changes of the
magnetic configuration, and to peculiar characteristics of HFl, oif
2nd, 3rd in the time order concerning the chromospheric transition
zone or coronal regions. The time delay between two consecutive
homologous flares appears very quickly as an essential parameter to
study homology. It was found that every set of flares (same type of
site) is able to produce “rafales” of homologous flares, i.e. two,
three, four, oir more flares with Δt in the range of one hour or
less. The observations show no great chantes in macroscopic photospheric
patterns (B, V) during this H flaring period. They lead to compare
their temporal variation curves of flare brightness. A quantitative
brightness parameter of homology relation has been defined. Some scale
changes have also been detected in the dynamic spectrum of the site, and
it is in good agreement with a very interesting theoretical suggestion
made by P. Sturrock to produce such “rafales”. It may be shown that
the closely consecutive time-homologous flares (CCHF) or “rafales”
represent a good tool to analyse the critical conditions related to
the origin and the amount of energy, mechanism of storage and release,
necessary and, perhaps, sufficient conditions. New statistical results,
applied to the different selected homologous flare active regions
are presented and show the existence in homologous flaring areas of
a “pivot” of previous filaments interpreted as a signature of an
anomaly in the Solar rotation.
---------------------------------------------------------
Title: Les traceurs du champ magnétique en physique solaire.
Authors: Mein, P.
1984cms..conf..341M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Activity in the homologous flare site
Authors: Mein, N.; Martres, M. -J.; Simon, G.; Mein, P.; Soru-Escaut,
I.
1984AdSpR...4g..33M Altcode: 1984AdSpR...4...33M
The evolution of a site where homologous flares occured on June 8,
1980 is analysed by using observations both in the photosphere and
in the chromosphere. The homology is discussed through space, energy
and dynamical aspects. The criteria are used in order to propose the
definition of a coefficient of homology.
---------------------------------------------------------
Title: Analysis of the Homology Criteria of Two Closely Consecutive
Flares
Authors: Martres, M. J.; Mein, N.; Mein, P.; Rayrole, J.; Simon, G.;
Soru-Escaut, I.
1984apoa.conf..261M Altcode:
The authors study the last two events of a series of closely consecutive
homologous flares ("rafale"). The main criteria of homology are present:
localization, evolution, brightness, magnetic structure. Although they
are among the best cases of homologous flares observed, some differences
may be detected which affect the dynamics of the region. This feature
must be taken into account to explain the annihilation of the homologous
mechanism.
---------------------------------------------------------
Title: Recurrent mass ejections observed in H<SUB>α</SUB> and CIV
Authors: Schmieder, B.; Simon, G.; Martres, M. -J.; Mein, P.; Mein,
N.; Tandberg-Hanssen, E.
1984AdSpR...4g..27S Altcode: 1984AdSpR...4...27S
Time sequences of recurrent mass ejections have been observed during a
coordinated SMY program (1 Sept. 1980 - 23 Sept. 1980 - 2 Oct. 1980). <P
/>Comparison of the temporal evolution of H<SUB>α</SUB> and CIV
brightnesses shows a weak phase lag between H α and CIV maxima, in
the case of homologous flares, with CIV brightness maxima preceding H
α maxima. The analysis of the variation of the ejection velocities
is expected to lead to the determination of an energy balance. <P
/>Such recurrent ejections could be due to periodic energy storage
and periodic reorganisation of magnetic field as envisaged to occur
for flares, but at lower energy levels.
---------------------------------------------------------
Title: Recommendations on post focus instrumentation for LEST.
Authors: Wöhl, H.; Huber, M. C. E.; Mein, P.; Smaldone, L.
1984LFTR....5.....W Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Chromospheric eruption, Jan - Dec 1984.
Authors: Cailloce, E.; Mein, N.; Lantos, P.
1984QBSA...26....1C Altcode:
This report shows, in a chronological order, a list of all reported
events whatever their importance.
---------------------------------------------------------
Title: Dynamics of a surge observed in the C IV and H alpha lines
Authors: Schmieder, B.; Mein, P.; Vial, J. -C.; Tandberg-Hanssen, E.
1983A&A...127..337S Altcode:
Time sequences of a surge have been obtained in Active Region 2701
during a coordinated SMY program, on October 2nd, 1980, while the MSDP
spectrograph operated in H-alpha at the Meudon Solar Tower and the UVSP
spectrometer on SMM observed in the 1548 A C IV resonance line. The cold
(H-alpha) and hot (C IV) material follow the same channel, and the event
lasts about 10 min in both lines. A good correlation is found between
H-alpha and C IV velocities; radial velocities along the surge are in
the range 40-60 km/s in both cases. The observations are consistent
with the hypothesis that a pressure gradient drives the surge. The
H-alpha data seem to indicate the presence of a shock wave in the
chromosphere, while the C IV quantities (velocities, accelerations)
vary on a very short time scale. Their maxima occur at some locations
which could be interpreted as 'pinched' zones.
---------------------------------------------------------
Title: Evidence of high chromospheric activity in Hyades dwarfs from
spectroscopic observations.
Authors: Cayrel, R.; de Strobel, G. Cayrel; Campbell, B.; Mein, N.;
Mein, P.; Dumont, S.
1983A&A...123...89C Altcode:
The Hα Balmer line and the infrared Ca II triplet have been observed
in two solar type dwarfs of the Hyades at the Coudé Spectrograph
of the Canada-France-Hawaii Telescope. Noticeable differences appear
in the cores of the lines between the stellar spectra and the solar
spectrum (moonlight). These differences are ascribed to a more active
chromosphere in the relatively young Hyades stars. Non-LTE computations
show that the average disk of one of the Hyades dwarf is similar to
a very bright element of the solar chromospheric network.
---------------------------------------------------------
Title: Dynamics of solar filaments. II - Mass motions in an active
region filament from H-alpha center to limb observations
Authors: Malherbe, J. M.; Schmieder, B.; Ribes, E.; Mein, P.
1983A&A...119..197M Altcode:
The authors present the observations of a solar filament obtained at
Meudon with the Hα spectroheliograph over a period of 10 d. They show
a morphologically stable feature. The authors perform a statistical
analysis of the radial velocity field. Assuming long-lived (several
days) stationary motions, they compute a 3-dimensional velocity field
from center to limb observations of the radial component of velocity
in the stable feature. Different pictures of stationary material
circulations are suggested and compared with theoretical models of
filaments. On the contrary, in the case of short-lived (a few 10
min) flows of material, the authors interpret their data in terms
of velocity loops in the magnetic structure supporting the filament,
and they compare the results with the MHD model proposed by Ribes and
Unno (1980). Possible improvements to this model are pointed out in
the conclusion.
---------------------------------------------------------
Title: Measurements of solar transition zone velocities and line
broadening using the ultraviolet spectrometer and polarimeter on
the Solar Maximum Mission
Authors: Simon, G.; Mein, P.; Vial, J. C.; Shine, R. A.; Woodgate,
B. E.
1982A&A...115..367S Altcode:
The UVSP instrument on SMM is able to observe solar regions at two
wavelengths in the same line with a band-pass of 0.3 A. Intensity and
Doppler velocity maps are derived. It is shown that the numerical
values are sensitive to the adopted Doppler width and the range of
velocities is limited to within 30 km/sec. A method called Double
Dopplergram Determination (DDD) is described for deriving both the
Doppler width and the velocity (up to 80 km/sec), and the main sources
of uncertainties are discussed. To illustrate the method, a set of C
IV 1548 A observations is analyzed according to this procedure. The
mean C IV Doppler width measured (0.15 A) is comparable to previous
determinations. A relation is found between bright regions and
down-flows. Large Doppler widths correspond to strong velocity
gradients.
---------------------------------------------------------
Title: Dynamics of the eruptive prominence of 6 May 1980 and its
relationship to the coronal transient
Authors: Mein, N.; Schmieder, B.; Simon, G.; Tandberg-Hanssen, E.;
Wu, S. T.
1982A&A...114..192M Altcode:
The active prominence of the 6 May 1980 has been observed between 5.23
and 10.22 UT with the Ultraviolet Spectrometer and Polarimeter (UVSP)
on board the Solar Maximum Mission (SMM) satellite. Intensities of
1548 A line of CIV and dopplershifts have been derived. A motion of
the magnetic tube maintaining the prominence material is noted. This
motion is followed by a coronal transient observed with the Coronagraph
and Polarimeter (C/P) between 11 and 13 UT. It is suggested that the
event is related to a MHD wave induced by a flare occurring behind
the solar disk, and a MHD modeling of the perturbation is proposed.
---------------------------------------------------------
Title: Dynamics of POST Flare Ejections and Magnetic Loop Geometry
Authors: Mein, P.; Mein, N.
1982SoPh...80..161M Altcode:
Flare-associated mass ejections have been observed at the solar limb
on June 29, 1980 in the Hα line, with the Multichannel Subtractive
Double Pass spectrograph of the Meudon solar tower. Radial velocities
were measured as a function of time in a two dimensional field, and
kinematics investigated in one selected fine structure. A simple
model of locally dipole-type magnetic field increasing with time
can be fitted to the data. It can be checked from extrapolation that
the model is consistent with an ejection starting roughly from the
same point at the same time. Height of the loops (∼ 135 000 km)
is consistent with other determinations. Magnetic field is found to
be increasing locally by a factor 1.14 within 10 min.
---------------------------------------------------------
Title: Mass motions in the solar chromosphere and transition zone
Authors: Mein, P.; Simon, G.; Vial, J. C.; Shine, R. A.
1982A&A...111..136M Altcode:
A comparison is made between H-alpha and C IV observations of Active
Region 2717 on October 9, 1980. On the basis of this comparison,
it is found that upward velocities are present above sunspots in the
chromosphere-corona transition zone (20 km/s). The downward velocities
are found to be well correlated in both lines. Doppler-shift ratios
between C IV and H-alpha levels (approximately 10) are seen to be much
smaller than expected from density ratio estimates. The comparison is
seen as suggesting that flow lines are probably far from vertical in
the transition zone. It is pointed out, however, that this depends
on model densities that may not be correct. A simple method for
comparing matter flows is presented. The best fit between H-alpha and
C IV levels is obtained when C IV Doppler shifts are multiplied by
the line intensity to the power 0.5 (approximately) in order to make
allowance for density fluctuations.
---------------------------------------------------------
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. <P />Velocity maps suggest shears
or velocity loops. <P />The filament disappearance seems to be due to
a heating mechanism beginning before the flare maximum.
---------------------------------------------------------
Title: A surge obsrved in Hα and CIV
Authors: Schmieder, B.; Mein, P.; Vial, J. C.; Tandberg-Hanssen, E.
1982AdSpR...2k.225S Altcode: 1982AdSpR...2..225S
Simultaneous Hα (MSDP at Meudon) and C IV (UVSP aboard SMM)
measurements of Active Region 2701 were made on October 2,
1980. Isodensity and velocity maps were derived for both lines
and superposed. A good correlation was found between Hα and C IV
velocities. A surge was observed for 10 minutes. The base was located
in a bright point in CIV and Hα, and escaping matter followed the same
channel (“absorbing” in Hα, “emitting” in C IV). The velocity
along the surge was about 80 kms.-1 in Hα and 100 km s-1 in C IV. A
loop appeared in C IV. We discuss the existing models and conclude
that the vertical pressure gradient was capable of driving the surge.
---------------------------------------------------------
Title: Mass motions in a quiescent filament
Authors: Malherbe, J. M.; Mein, P.; Schmieder, B.
1982AdSpR...2k..57M Altcode: 1982AdSpR...2R..57M
The “disparition brusque” (DB) of a filament (N20, E35) has been
observed above an active region with the Multichannel Subtractive
Double Pass (MSDP) spectrograph operating on the Meudon Solar Tower,
from 10h45 UT to 13h30 UT on June 22, 1981. <P />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 <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. <P
/>These results are compared with some theoretical works on dynamics
inside magnetic loops, especially to siphon flow models. However,
as in the case of the prominence support problem, better theoretical
models are still needed.
---------------------------------------------------------
Title: About the onsets of closely-consecutive homologous flares
Authors: Martres, M. J.; Mein, N.; Mein, P.; Mouradian, Z.; Rayrole,
J.; Schmieder, B.; Simon, G.; Soru-Escaut, I.; Woodgate, B.; Strong, K.
1982AdSpR...2k.109M Altcode: 1982AdSpR...2R.109M
The onsets of closely consecutive homologous flares (CCHF), which
are separated by less than 6 hours and most often by about 1 hour,
are compared with that of isolated flares (no flare in the region half
a day before). Isolated flares appear to be formed of two components,
a surging arch and a flaring arch, while a set of CCHF may be composed
of consecutive elementary flares or of a series of complex ones. It
is shown that the onset of eruptive flare phenomena is not the same
for an isolated event and for a member of CCHF (excluding the first)
as found in H-alpha and EUV observations, and probably in X-ray
observations also. It is suggested that a CCHF set would become a
single flare with episodic enhancement of brightness by taking account
of the common H-alpha behavior of surging and flaring arches as well
as the EUV emission.
---------------------------------------------------------
Title: Dynamics in the filaments. I - Oscillations in a quiescent
filament
Authors: Malherbe, J. M.; Schmieder, B.; Mein, P.
1981A&A...102..124M Altcode:
A quiescent filament is observed by the 9 channel MSDP spectrograph
operating on the Meudon Observatory tower during 720 s with a 30 s
time step. The field view of 6 x 1 arcmin permits the study of the
dynamics of 50 oscillation cells which increases the freedom degree
comparatively to the one slit spectrograph techniques. A Fourier
analysis of the radial velocity measured in the H-alpha line shows
that the steady velocities are upward in the filament, while the
chromospheric oscillations are almost undetectable inside the filament.
---------------------------------------------------------
Title: Mechanical flux in the solar chromosphere. III - Variation
of the mechanical flux
Authors: Mein, N.; Schmieder, B.
1981A&A....97..310M Altcode:
The mechanical flux in the photosphere and the chromosphere is inferred
from observations of atmospheric oscillations made over a large range
of periods (60s-400s). Observations of Doppler shifts in Ca II and Mg
I lines are related to velocities by means of heights of formation and
modulation transfer functions deduced from weighting functions. The
flux is derived from estimates of the amplitude and phase of the
velocity at different heights in the atmosphere. The results imply
that the energy dissipated by waves in a plane-parallel atmospheric
model is insufficient to balance the radiative losses. The short-fall
can reach a factor 100 in the high chromosphere. Heating of the corona
by shock wave dissipation is inconsistent with our results.
---------------------------------------------------------
Title: Structure and Evolution of Velocities in Quiescent Filaments
Authors: Martres, M. -J.; Mein, P.; Schmieder, B.; Soru-Escaut, I.
1981SoPh...69..301M Altcode:
Simultaneous observations of radial velocities in a `quiescent'
prominence seen in Hα on the disk and in the underlaying photosphere
have been obtained in the Meudon Observatory: Doppler shifts in
photospheric lines are weaker than in the surrounding regions (<0.3
km s<SUP>-1</SUP>); the scale of velocity structures is smaller
(<10<SUP>4</SUP> km). The vertical component of velocities cannot
be neglected. Hα Doppler shifts show that: (a) Highest velocities
are often correlated with high brightness horizontal gradients,
which suggests that filament and surrounding bright regions belong
to the same geometrical and dynamical structure. (b) Fast motions
(7 km s<SUP>-1</SUP>) have short life-times (a few minutes). (c) Slow
motions in dark regions (<3 km s<SUP>-1</SUP>) are associated with
blue shifts and may last several hours. This behaviour was confirmed
in many other cases by filament observations with the 3-wavelength Hα
patrol. This is consistent with EUV observations of the transition zone
around prominences, but disagrees with `downward motions' as seen at
the limb, unless these motions do not refer to material velocities.
---------------------------------------------------------
Title: Mechanical flux in the solar chromosphere.
Authors: Mein, P.
1981ASIC...68..265M Altcode: 1981spss.conf..265M
Energy transport by pressure waves in the solar atmosphere is studied
on the basis of observations of chromospheric line profiles. Mechanical
fluxes are deduced as a function of frequency from Doppler shifts in
the 3933 and 8542 Ca II lines; and integrated over the period range
800 to 30 sec to obtain a total flux of 6000 erg/sq cm per sec. Flux
values determined as a function of height from the Doppler shifts and
intensity fluctuations of one or more lines are also presented. It
is pointed out that the values of mechanical flux derived are almost
two orders of magnitude less than the 300,000 erg/sq cm per sec of
radiant energy lost from the transition region and corona, requiring an
additional mechanism to account for the heating of the upper atmosphere.
---------------------------------------------------------
Title: The sites of solar flares
Authors: Mein, P.
1981soac.rept.....M Altcode:
Observations of solar flares were studied. Results on the magnetic field
structure associated with an elementary flare are discussed. Conditions
which prelude the triggering of instabilities (homologous flares,
disappearance of filaments) are covered. The postflare relaxation phase
is also considered. Linear polarization of lines during flare events and
the variable geometry of magnetic field lines (mass ejection dynamics)
are treated. The importance of continuous observation over several
hours in interpreting these events is shown.
---------------------------------------------------------
Title: Mechanical flux in the solar chromosphere. I - Velocity and
temperature weighting functions for CA II lines
Authors: Mein, N.; Mein, P.
1980A&A....84...96M Altcode:
Weighting functions for velocity and temperature disturbances are
computed in the case of Ca II 3933, 8498, and 8542 with the HSRA
model atmosphere. Temperature W-functions are generally broader than
velocity W-functions, due to coupling between lines. Subsequently,
formation altitudes and transfer functions for doppler shifts and
intensity fluctuations are very different. Results are plotted against
frequency with a view to the derivation of wave mechanical flux from
line observations.
---------------------------------------------------------
Title: Mechanical flux in the solar chromosphere. II - Determination
of the mechanical flux
Authors: Schmieder, B.; Mein, N.
1980A&A....84...99S Altcode:
The observations of two lines of Ca II (8542-8498) made with the
Sacramento Peak Tower and formation altitudes values Z(omega) for these
two lines determined by weighting functions are used to evaluate, for
each frequency omega, the mechanical flux F(omega) corresponding to
the altitude Z(omega). Corrections taking into account the weakening
of waves of wavelengths smaller than the line formation layer were
applied to the flux. The corrected flux does not show a significant
increase with the frequency (up to 10 mHz), which seems to indicate
that nonthermal microturbulence does not correspond necessarily to
progressive wave. The mechanical flux integrated over the frequency
range 0-10 mHz reaches at the most 2000 erg/sq cm s in the middle
chromosphere (1100 km). This is not sufficient to balance the energy
losses of the transition zone and the corona.
---------------------------------------------------------
Title: Motions and Oscillations in Filaments
Authors: Malherbe, J. M.; Martres, M. J.; Mein, P.; Schmieder, B.;
Soru-Escaut, I.
1980jfss.conf..166M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Multi-Channel Subtractive Double Pass Spectrograph
Authors: Mein, P.
1980jfss.conf..285M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Observational Proof of the Inefficiency of the Chromospheric
Heating by Acoustic Waves
Authors: Mein, P.; Mein, N.; Schmieder, B.
1980jfss.conf...70M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Dynamics of a Quiescent Filament
Authors: Schieder, B.; Martres, M.; Mein, P.; Soru-Escaut, I.
1980IAUS...91..213S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Wave Reflections in the Solar Atmosphere
Authors: Provost, J.; Mein, N.
1979SoPh...64...43P Altcode:
The small phase-lag between velocities observed at different
chromospheric levels is interpreted as being due to acoustic waves
reflected by the very hot atmospheric layers of the chromosphere-corona
transition zone. We consider first an isothermal slab, then a
realistic solar atmospheric model and calculate weighting functions
for velocities in Ca II lines. It is shown that taking into account
these functions and integrating over horizontal wave numbers leads
to a good agreement with previous observations (Mein, 1977) in the
case of 8498 and 8542 Ca II lines. For the K line, the less good
agreement shows that magnetoacoustic waves become important in the
upper chromospheric layers.
---------------------------------------------------------
Title: Mechanical energy transport in the solar photosphere and
chromosphere.
Authors: Mein, P.
1979ssms.conf...15M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Relation between the mode of oscillation and the velocity
amplitude of chromospheric waves.
Authors: Mein, N.
1978SoPh...59....3M Altcode:
The distribution of oscillation-amplitude for Doppler shifts in
chromospheric lines is computed as a function of position on the disk
and time frequency. High amplitude regions are restricted to a small
part of the solar surface. Propagation modes are investigated with
respect to the oscillation amplitude in the K line. Waves seem to be
standing or evanescent for most of the points (small amplitude in K)
and progressive for some other ones, with perhaps upward and downward
motions (partial reflections). Mechanical energy could only escape
into corona from narrow chromospheric structures.
---------------------------------------------------------
Title: The Evolution of a transient Hα Feature probably associated
with a Type III Burst
Authors: Mein, P.; Martres, M. J.; Soru-Escaut, I.
1978pfsl.conf..233M Altcode: 1978ESPM....2..233M
No abstract at ADS
---------------------------------------------------------
Title: Multi-channel subtractive spectrograph and filament
observations.
Authors: Mein, P.
1977SoPh...54...45M Altcode:
A Multi-Channel Subtractive Double Pass spectrograph (MSDP) has
been achieved at the Meudon solar tower. Line profiles are obtained
simultaneously in a two dimensional field. Space and time resolutions
are very suitable for observation of fast chromospheric phenomena.
---------------------------------------------------------
Title: Wave propagation in the quiet solar chromosphere.
Authors: Mein, N.
1977SoPh...52..283M Altcode:
In order to precise previous results about wave propagation in the
quiet chromosphere (N. Mein and P. Mein, 1976), we study the behaviour
of Doppler shifts and intensity fluctuations in 3 lines of Ca II.
---------------------------------------------------------
Title: Velocity waves in the quiet solar chromosphere.
Authors: Mein, N.; Mein, P.
1976SoPh...49..231M Altcode:
Propagation of velocity waves are investigated in the solar
chromosphere, with a special view to high frequencies (periods
≥ 60 s). Four line profiles have been observed during 27 mn with
the Sacramento Peak vacuum telescope (Hα, 3933, 8498 and 8542 Ca
II). Three Fourier analysis are performed according to the location
in the cells of the chromospheric network. Phase-shifts and amplitude
ratios between the line Doppler shifts are computed as functions of
frequency. The "pollution" of high frequency results by energetic low
frequency oscillations is investigated.
---------------------------------------------------------
Title: Radiation and structure of the solar atmosphere (Radiation
et structure de l'atmosphère solaire).
Authors: Giovanelli, R. G.; Mein, P.; Bappu, M. K. V.; Jordan, C.;
MacQueen, R. M.
1976IAUTA..16b..55G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Propagation des ondes dans la chromosphère
Authors: Mein, N.; Mein, P.
1976pmas.conf..269M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The Photosphere
Authors: Mein, P.
1976IAUTA..16...55M Altcode: 1976IAUT...16A..55M
No abstract at ADS
---------------------------------------------------------
Title: The Hydrogen Balmer Lines and the Structure of the Quiet
Solar Chromosphere. I: Observations at the Limb
Authors: Mein, P.; Mein, N.
1975SoPh...40..317M Altcode:
Spectra of Hα, Hβ and Hδ have been taken under good seeing
conditions with the vacuum tower telescope of Sacramento Peak
Observatory. Intensity curves are given at various wavelengths in these
lines to permit further comparison with a theoretical model. Moreover,
considering in each case the range of height in which the lines are
almost optically thin and using a few approximations, the following
results are derived: between 2000 and 6000 km above the limb the
average thermal + turbulent velocity of the atoms is found to increase
from 20 km s<SUP>−1</SUP> to 30 km s<SUP>−1</SUP> and the mean
number of hydrogen atoms per cm<SUP>3</SUP> in level 2 is given by log
n<SUB>2</SUB> = 4.5 - 0.00056(z-2000) z being the altitude above the
limb in km. For line profile computations a new interpolation formula
is presented; it gives good profiles with a small number of scans,
saving microphotometer time.
---------------------------------------------------------
Title: A Substractive Double Pass Spectrograph for Solar Observations
Authors: Mein, P.; Blondel, M.
1972SoPh...27..489M Altcode:
Two-dimensional images in locally monochromatic light are obtained,
using a subtractive double pass spectrograph. The spatial resolution
is high and independent of the spectral bandwidth. The system is very
suitable for fine structure observations in strong lines.
---------------------------------------------------------
Title: Inhomogeneities in the Solar Atmosphere from the Ca II
Infra-Red Lines
Authors: Mein, Pierre
1971SoPh...20....3M Altcode:
From a time sequence of high dispersion spectra taken by Evans, the
solar fine structures are studied in the CaII infra-red triplet. The
Doppler shifts and the intensity fluctuations in different points
of the profiles are converted into fluctuations of the model
atmosphere. A weighting function method is worked out in that
purpose. The theoretical line profiles are computed in non LTE from a
program written by Dumont. The results are arranged in two parts: Low
temporal frequencies. A three-column model describes the steady field
of temperature, microturbulence and radial velocities fluctuations in
the photosphere-chromosphere transition zone.
---------------------------------------------------------
Title: Propagation of Magneto-Acoustic Waves along the Gravitational
Field in an Isothermal Atmosphere
Authors: Bel, N.; Mein, P.
1971A&A....11..234B Altcode:
We study the local dispersion equation obtained by MoLellan and
Winterberg (1968) for magneto-acoustic waves propagating in an
isothermal atmosphere. We restrict ourselves to wave propagation
vectors along the gravitational field, for an arbitrary direction of
the magnetic field. The propagation of the waves is shown to depend
on two parameters, namely the ratios of the Alfve'n velocity and of
the Alfv6n velocity for the vertical component of the magnetic field
to the speed of sound. For typical values of these two parameters,
we obtain representative curves for the phase and the amplitude of
the waves as functions of the frequency. We find two modes, which are
the counterparts of the usual fast and slow magneto-acoustic waves. A
comparison with the case of an isothermal and compressible atmosphere
without a magnetic field shows that the new mode is the slow one. We
find that the magnetic field decreases the hydrodynarnic cut-off
frequency and that, for large values of the magnetic field, the fast
and the slow modes can intersect. The theoretical curves thus obtained
make possible a direct comparison with observational data concerning
the solar atmosphere. Key wor : waves - magnetic field - gravity -
solar atmosphere
---------------------------------------------------------
Title: Observations du rapport H<SUB>α</SUB>/[N II] par une méthode
interférométrique. Application à la nébuleuse de la Rosette
Authors: Mein, N.
1968AnAp...31..579M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Étude spatio-temporelle de la granulation
solaire. Amélioration des images déformées par l'agitation
atmosphérique
Authors: Mein, P.
1968AnAp...31..115M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Champ macroscopique des vitesses dans l'atmosphère solaire
d'après les mesures de déplacements des raies de Fraunhofer
Authors: Mein, P.
1966AnAp...29..153M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Déformation du Profil des Raies Liées aux Ondes Sonores
dans le Cas Solaires
Authors: Mein, P.
1966IAUTB..12..563M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Propagation Horizontale des Oscillations de Vitesse Observées
sur le Disque Solaire
Authors: Mein, P.
1965CRASB.260.1867M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Etude d'une Raie Solaire Perturbée par des Ondes Acoustiques
Planes; Résultats Numériques
Authors: Mein, P.
1964CRASB.258..819M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Etude d'une Raie Solaire Perturbée par des Ondes Acoustiques
Planes; Exposé d'une Méthode
Authors: Mein, P.
1964CRASB.258..453M Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Spectre continu du Soleil
Authors: Mein, P.
1959LAstr..73....5M Altcode:
No abstract at ADS