explanation blue bibcodes open ADS page with paths to full text
Author name code: gouttebroze
ADS astronomy entries on 2022-09-14
author:"Gouttebroze, Pierre"
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Title: PROM7: 1D modeler of solar filaments or prominences
Authors: Gouttebroze, P.
2018ascl.soft05023G Altcode:
PROM7 is an update of PROM4 (ascl:1306.004) and computes simple models
of solar prominences and filaments using Partial Radiative Distribution
(PRD). The models consist of plane-parallel slabs standing vertically
above the solar surface. Each model is defined by 5 parameters:
temperature, density, geometrical thickness, microturbulent velocity
and height above the solar surface. It solves the equations of radiative
transfer, statistical equilibrium, ionization and pressure equilibria,
and computes electron and hydrogen level population and hydrogen line
profiles. Moreover, the code treats calcium atom which is reduced to 3
ionization states (Ca I, Ca II, CA III). Ca II ion has 5 levels which
are useful for computing 2 resonance lines (H and K) and infrared
triplet (to 8500 A).
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Title: PROM4: 1D isothermal and isobaric modeler for solar prominences
Authors: Gouttebroze, P.; Labrosse, N.
2013ascl.soft06004G Altcode:
PROM4 computes simple models of solar prominences which consist of
plane-parallel slabs standing vertically above the solar surface. Each
model is defined by 5 parameters: temperature, density, geometrical
thickness, microturbulent velocity and height above the solar
surface. PROM4 solves the equations of radiative transfer, statistical
equilibrium, ionization and pressure equilibria, and computes electron
and hydrogen level populations and hydrogen line profiles. Written in
Fortran 90 and with two versions available (one with text in English,
one with text in French), the code needs 64-bit arithmetic for real
numbers. <P />PROM7 (ascl:1805.023) is a more recent version of
this code.
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Title: Radiative transfer in cylindrical threads with incident
radiation. VI. A hydrogen plus helium system
Authors: Gouttebroze, P.; Labrosse, N.
2009A&A...503..663G Altcode: 2009arXiv0905.3466G
Context: Spectral lines of helium are commonly observed on
the Sun. These observations contain important information about
physical conditions and He/H abundance variations within solar outer
structures. <BR />Aims: The modeling of chromospheric and coronal
loop-like structures visible in hydrogen and helium lines requires
the use of appropriate diagnostic tools based on NLTE radiative
tranfer in cylindrical geometry. <BR />Methods: We use iterative
numerical methods to solve the equations of NLTE radiative transfer and
statistical equilibrium of atomic level populations. These equations are
solved alternatively for hydrogen and helium atoms, using cylindrical
coordinates and prescribed solar incident radiation. Electron density is
determined by the ionization equilibria of both atoms. Two-dimensional
effects are included. <BR />Results: The mechanisms of formation of the
principal helium lines are analyzed and the sources of emission inside
the cylinder are located. The variations of spectral line intensities
with temperature, pressure, and helium abundance, are studied. <BR
/>Conclusions: The simultaneous computation of hydrogen and helium
lines, performed by the new numerical code, allows the construction
of loop models including an extended range of temperatures.
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Title: Formation of Helium Lines in Solar Prominences
Authors: Labrosse, Nicolas; Gouttebroze, Pierre
2009AIPC.1171..361L Altcode:
We summarize the results on the formation of the helium spectrum in
solar prominences obtained over recent years. The radiative transfer
problem under non-LTE conditions is solved to compute the profiles of
the lines of He I and He II. The structure of the prominence-to-corona
transition region (PCTR) has a major influence on the resulting spectrum
of the resonance lines since they are formed mostly in this part of
the prominence. However, subordinate lines are also affected by the
structure of the PCTR. We pay particular attention to the formation
of the He II 304 A˚ resonance line which is routinely observed from
space, but yet not fully understood. Future steps in the modelling
will be addressed.
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Title: Helioseismic Spectral Diagnostics - An Update
Authors: Leibacher, John W.; Baudin, F.; Belkacem, K.; Dupret, M.;
Goupil, M.; Gouttebroze, P.; Samadi, R.
2009SPD....40.0716L Altcode:
In order to test models of the excitation of p modes and their behavior
in the visible atmosphere, we calculate time sequences of Fraunhofer
absorption line profiles of the Ni, Fe, K, Na, and Ca lines used in
helioseismology, focusing on Sun-as-a-star observations in this initial
work. The atmospheric models, which give rise to the line profiles, are
based on the VAL-C, perturbed by realistic p-mode eigenfunctions. The
time sequences of line profiles are analyzed as for various instruments,
to compare predicted and observed mode amplitudes as a function of
temporal frequency
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Title: Diagnostics of active and eruptive prominences through hydrogen
and helium lines modelling
Authors: Labrosse, N.; Vial, J. -C.; Gouttebroze, P.
2008AnGeo..26.2961L Altcode: 2008arXiv0804.4625L
In this study we show how hydrogen and helium lines modelling can be
used to make a diagnostic of active and eruptive prominences. One
motivation for this work is to identify the physical conditions
during prominence activation and eruption. Hydrogen and helium
lines are key in probing different parts of the prominence structure
and inferring the plasma parameters. However, the interpretation of
observations, being either spectroscopic or obtained with imaging, is
not straightforward. Their resonance lines are optically thick, and
the prominence plasma is out of local thermodynamic equilibrium due
to the strong incident radiation coming from the solar disk. In view
of the shift of the incident radiation occuring when the prominence
plasma flows radially, it is essential to take into account velocity
fields in the prominence diagnostic. Therefore we need to investigate
the effects of the radial motion of the prominence plasma on hydrogen
and helium lines. The method that we use is the resolution of the
radiative transfer problem in the hydrogen and helium lines out of
local thermodynamic equilibrium. We study the variation of the computed
integrated intensities in H and He lines with the radial velocity of
the prominence plasma. We can confirm that there exist suitable lines
which can be used to make a diagnostic of the plasma in active and
eruptive prominences in the presence of velocity fields.
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Title: Radiative transfer in cylindrical threads with incident
radiation. V. 2D transfer with 3D velocity fields
Authors: Gouttebroze, P.
2008A&A...487..805G Altcode:
Context: Time-resolved observations of loops embedded in the solar
corona show the existence of motions of matter inside these structures,
as well as the global motions of these objects themselves. <BR />Aims:
We have developed a modeling tool for cylindrical objects inside the
solar corona, including 2-dimensional (azimuth-dependent) radiative
transfer effects and 3-dimensional velocity fields. <BR />Methods:
We used numerical methods to simultaneously solve the equations
of NLTE radiative transfer, statistical equilibrium of hydrogen
level populations, and electric neutrality. The radiative transfer
equations were solved using cylindrical coordinates and prescribed
solar incident radiation. In addition to the effects of anisotropic
incident radiation, treated in previous papers, we took into account
the Doppler shifts produced by a 3-dimension velocity field. <BR
/>Results: The effects of different types of velocity fields on
hydrogen line profiles and intensities are described. Motions include
loop oscillations, rotation, and longitudinal flows, which produce
different deformations of profiles. Doppler brightening and dimming
effects are also observed. <BR />Conclusions: This is a new step in
the diagnostic of physical conditions in coronal loops, allowing the
study of dynamical phenomena.
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Title: The Quiet Sun Network at Subarcsecond Resolution: VAULT
Observations and Radiative Transfer Modeling of Cool Loops
Authors: Patsourakos, S.; Gouttebroze, P.; Vourlidas, A.
2007ApJ...664.1214P Altcode:
One of the most enigmatic regions of the solar atmosphere is the
transition region (TR), corresponding to plasmas with temperatures
intermediate of the cool, few thousand K, chromosphere and the hot,
few million K, corona. The traditional view is that the TR emission
originates from a thin thermal interface in hot coronal structures,
connecting their chromosphere with their corona. This paradigm fails
badly for cool plasmas (~T<10<SUP>5</SUP> K), since it predicts
emission orders of magnitude less than what it is observed. It was
therefore proposed that the “missing” TR emission could originate from
tiny, isolated from the hot corona, cool loops at TR temperatures. A
major problem in investigating this proposal is the very small sizes
of the hypothesized cool loops. Here, we report the first spatially
resolved observations of subarcsecond-scale looplike structures seen
in the Lyα line made by the Very High Angular Resolution Ultraviolet
Telescope (VAULT). The subarcsecond (~0.3") resolution of VAULT allows
us to directly view and resolve looplike structures in the quiet Sun
network. We compare the observed intensities of these structures with
simplified radiative transfer models of cool loops. The reasonable
agreement between the models and the observations indicates that an
explanation of the observed fine structure in terms of cool loops
is plausible.
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Title: Spectral Diagnostics of Active Prominences
Authors: Labrosse, N.; Gouttebroze, P.; Vial, J. -C.
2007ASPC..368..337L Altcode: 2006astro.ph.11488L
Active prominences exhibit plasma motions, resulting in difficulties
with the interpretation of spectroscopic observations. These solar
features being strongly influenced by the radiation coming from
the solar disk, Doppler dimming or brightening effects may arise,
depending on which lines are observed and on the velocity of the
plasma. Interlocking between the different atomic energy levels and
non local thermodynamic equilibrium lead to non-trivial spectral line
profiles, and this calls for complex numerical modeling of the radiative
transfer in order to understand the observations. We present such a
tool, which solves the radiative transfer and statistical equilibrium
for H, He I, He II, and Ca II in moving prominences where radial plasma
motions are taking place. It is found that for isothermal, isobaric
prominence models, the He II resonance lines are very sensitive to the
Doppler effect and thus show a strong Doppler dimming. The Ca II lines
Doppler effect for the prominence models considered here. We illustrate
how the code makes it possible to retrieve the plasma thermodynamic
parameters by comparing computed and observed line profiles of
hydrogen and helium resonance lines in a quiescent prominence. This
new non-LTE radiative transfer code including velocities allows us
to better understand the formation of several lines of importance in
prominences, and in conjunction with observations, infer the prominence
plasma thermodynamic properties and full velocity vector.
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Title: Radiative transfer in cylindrical threads with incident
radiation. IV. Time-dependent and thermal equilibrium models
Authors: Gouttebroze, P.
2007A&A...465.1041G Altcode:
Context: Relatively cool and dense structures embedded in the solar
corona (filaments, prominences, spicules, etc.) may be observed in
hydrogen lines. Sometimes they last during several solar rotations. <BR
/>Aims: Our goal is to evaluate the lifetime of cool structures
of the solar corona, determine their evolution from given physical
conditions, and compute models in thermal equilibrium. <BR />Methods:
We use numerical methods to simultaneously solve the equations of
NLTE radiative transfer, statistical equilibrium of hydrogen level
populations, and electric neutrality. Radiative transfer equations are
solved using cylindrical coordinates and prescribed solar incident
radiations. The computation of internal energy and radiative losses
and gains yields the rates of temperature evolution. <BR />Results:
For isothermal-isobaric cylinders with prescribed physical conditions,
we determine the lifetimes and evolution rates for different positions
along the radius. For models with prescribed diameter and pressure,
we determine the run of temperature vs. radius corresponding to
thermal equilibrium. This equilibrium is found to be stable for the
whole range of parameters under investigation. <BR />Conclusions: .The
cores of large and high-pressure cylinders are found to evolve very
slowly. This opens the possibility of observing these cool structures at
temperatures somewhat different from that corresponding to theoretical
radiative equilibrium.
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Title: Effect of motions in prominences on the helium resonance
lines in the extreme ultraviolet
Authors: Labrosse, N.; Gouttebroze, P.; Vial, J. -C.
2007A&A...463.1171L Altcode: 2006astro.ph..8221L
Context: Extreme ultraviolet resonance lines of neutral and ionised
helium observed in prominences are difficult to interpret as the
prominence plasma is optically thick at these wavelengths. If mass
motions are taking place, as is the case in active and eruptive
prominences, the diagnostic is even more complex. <BR />Aims: We aim
at studying the effect of radial motions on the spectrum emitted by
moving prominences in the helium resonance lines and at facilitating the
interpretation of observations, in order to improve our understanding
of these dynamic structures. <BR />Methods: We develop our non-local
thermodynamic equilibrium radiative transfer code formerly used
for the study of quiescent prominences. The new numerical code is
now able to solve the statistical equilibrium and radiative transfer
equations in the non-static case by using velocity-dependent boundary
conditions for the solution of the radiative transfer problem. This
first study investigates the effects of different physical conditions
(temperature, pressure, geometrical thickness) on the emergent helium
radiation. <BR />Results: The motion of the prominence plasma induces
a Doppler dimming effect on the resonance lines of He I and He II. The
velocity effects are particularly important for the He II λ 304 Å line
as it is mostly formed by resonant diffusion of incident radiation under
prominence conditions. The He I resonance lines at 584 and 537 Å also
show some sensitivity to the motion of the plasma, all the more when
thermal emission is not too important in these lines. We also show
that it is necessary to consider partial redistribution in frequency
for the scattering of the incident radiation. <BR />Conclusions: .This
set of helium lines offers strong diagnostic possibilities that can be
exploited with the SOHO spectrometers and with the EIS spectrometer on
board the Hinode satellite. The addition of other helium lines and of
lines from other elements (in particular hydrogen) in the diagnostics
will further enhance the strength of the method. <P />Figures [see
full text], [see full text] and [see full text] are only available in
electronic form at http://www.aanda.org
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Title: The Helium Spectrum in Erupting Solar Prominences
Authors: Labrosse, N.; Vial, J. C.; Gouttebroze, P.
2006IAUJD...3E..47L Altcode: 2006astro.ph..9511L
Even quiescent solar prominences may become active and sometimes
erupt. These events are occasionally linked to coronal mass
ejections. However we know very little about the plasma properties
during the activation and eruption processes. We present the first
computations of the helium line profiles emitted by an eruptive
prominence. We follow the approach of Gontikakis et al. (1997) who
computed the hydrogen spectrum in moving prominences. The prominence
is modelled as a plane-parallel slab standing vertically above the
solar surface and moving upward as a solid body. The helium spectrum is
computed with a non local thermodynamic equilibrium radiative transfer
code. The effect of Doppler dimming / brightening is investigated in
the resonance lines of He I and He II formed in the EUV, as well as on
the He I 10830 Å and He I 5876 Å lines. We focus on the line profile
properties and the resulting integrated intensities. We also study the
effect of frequency redistribution in the formation mechanisms of the
resonance lines. It is shown that the helium lines are very sensitive
to Doppler dimming effects. Together with the hydrogen lines they offer
the possibility of a powerful diagnostic of the active and eruptive
prominence plasma. We discuss the results in view of observations
provided by SOHO, and by the upcoming EUS spectrometer on SOLAR-B.
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Title: The Helium Spectrum in Moving Solar Prominences
Authors: Labrosse, N.; Gouttebroze, P.; Vial, J. -C.
2006ESASP.617E.134L Altcode: 2006soho...17E.134L
No abstract at ADS
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Title: Plasma diagnostic of a solar prominence from hydrogen and
helium resonance lines
Authors: Labrosse, N.; Vial, J. -C.; Gouttebroze, P.
2006sf2a.conf..549L Altcode: 2006astro.ph..9643L
We present the first comparison of profiles of H et He resonance lines
observed by SUMER with theoretical profiles computed with our non-LTE
radiative transfer code. We use the HI Lyman β, HI Lyman ɛ, and He
I λ 584 Å lines. Our code allows us to obtain the plasma parameters
in prominences in conjunction with a multi-line, multi-element set
of observations. The plasma temperature in the prominence core is ∼
8600 K and the pressure is 0.03 dyn cm<SUP>-2</SUP>. The Lyβ line is
formed in a higher temperature region (more than 11,000 K).
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Title: Radiative transfer in cylindrical threads with incident
radiation. III. Hydrogen spectrum
Authors: Gouttebroze, P.
2006A&A...448..367G Altcode:
A numerical code is proposed for the solution of NLTE radiative
transfer equations in long cylinders, including multilevel atoms
and anisotropic incident radiation (which implies a 2-dimension
treatment of the radiation field). It is applied to the modelling
of the hydrogen spectrum emitted by magnetic loops imbedded in the
solar corona. The model hydrogen atom includes 10 levels and one
continuum. The intensities emitted by loops in the most important
hydrogen lines and in the Lyman continuum are discussed using a set
of isothermal and isobaric models. The case of loops with a radial
temperature gradient is also investigated.
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Title: Transfer in cylindrical fluxtubes, with 1 or 2 dimensions
Authors: Gouttebroze, P.
2006EAS....18...49G Altcode:
This is a review of methods for the solution of non-LTE radiative
transfer equations in long cylinders. The principal goal of these
methods is the modelling of elongated structures imbedded in the solar
corona, such as loops or prominence threads. These objects are submitted
to the solar radiation, which determines the boundary conditions of
the problem. Different cases are examined. Concerning the geometry,
one-dimension and two-dimension cases are treated. The two-dimension
case itself is subdivided into (radius, altitude) and (radius, azimuth)
problems, which are treated by quite different methods. Another
distinction concerns the method of resolution: semi-analytical,
Monte-Carlo and finite-difference methods are examined. Some methods are
restricted to a two-level atom, others allow the treatment of realistic
multilevel cases. Some recent results, obtained with finite-difference,
accelerated Λ-iteration methods, are presented.
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Title: Radiative transfer in cylindrical threads with incident
radiation. II. 2D azimuth-dependent case
Authors: Gouttebroze, P.
2005A&A...434.1165G Altcode:
A method is proposed for the solution of NLTE radiative transfer
equations in long cylinders with an external incident radiation that
varies with direction. This method is designed principally for the
modelling of elongated structures imbedded in the solar corona (loops,
prominence threads). The radiative transfer problem under consideration
is a 2D one, since the source functions and absorption coefficients
vary with both distance to axis and azimuth. The method is based on the
general principles of finite-differences and accelerated Λ-iteration. A
Fourier series is used for interpolation in azimuth. The method is
applied to a line emitted by a two-level atom with complete frequency
redistribution. Convergence properties of the method and influence of
the inclination angle on the source function are discussed.
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Title: Inferred acoustic rates of solar p modes from several
helioseismic instruments
Authors: Baudin, F.; Samadi, R.; Goupil, M. -J.; Appourchaux, T.;
Barban, C.; Boumier, P.; Chaplin, W. J.; Gouttebroze, P.
2005A&A...433..349B Altcode:
Acoustic rates of excitation of solar p modes can be estimated from
observations in order to place constraints on the modelling of the
excitation process and the layers where it occurs in the star. For
several reasons (including a poor signal to noise ratio and mode
overlap), this estimation is difficult. In this work, we use three
completely independent datasets to obtain robust estimates in the
solar case for ℓ=1 modes. We also show that the height in the solar
atmosphere where the modes are observed must be taken into account. Our
three sets of results are shown to be consistent, particularly in
the lower part of the p-mode spectrum (from 1.8 mHz to 2.8 mHz). At
higher frequencies, the agreement is not as good, because of a larger
dispersion of the measurements and also because of some systematic
differences which might be due to observation height estimation or to
a systematic influence of the noise.
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Title: Non-LTE Radiative Transfer in Model Prominences. I. Integrated
Intensities of He I Triplet Lines
Authors: Labrosse, N.; Gouttebroze, P.
2004ApJ...617..614L Altcode:
In this work we use new results of radiative transfer calculations
out of local thermodynamical equilibrium to study the triplet lines
emitted by neutral helium in solar quiescent prominences. We compare two
types of prominence atmospheres: isothermal and isobaric models versus
nonisothermal and nonisobaric ones. We can thus investigate the effect
of the presence of a prominence-to-corona transition region (PCTR) on
the emergent intensities in detail. It is found that the presence of
the PCTR affects the emitted intensities of the triplet lines, even
though they are formed in the central parts of the prominence. We
show that the inclusion of a transition region reduces the impact
of collisional excitation at high temperatures in comparison with
the isothermal and isobaric case. A simple study of helium energy
level populations shows how statistical equilibrium is changed when a
transition region is present. This points to the necessity of including
an interface between the prominence body and the corona to predict
all emergent intensities, whatever the region of formation of the
radiation. We have found a correlation between most of the He I triplet
line ratios and the altitude of the model prominence. Comparisons of
our predicted intensity ratios with observations yield generally good
agreement. Remaining discrepancies may be resolved by extrapolating
our predicted results to higher altitudes.
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Title: Flare observation of the Sun as a star by SUMER/SOHO in the
hydrogen Lyman continuum
Authors: Lemaire, P.; Gouttebroze, P.; Vial, J. -C.; Curdt, W.;
Schühle, U.; Wilhelm, K.
2004A&A...418..737L Altcode:
During the execution of the programme “Sun as a star”, while the
SUMER (Solar Ultraviolet Emission of Emitted Radiation)/SOHO (SOlar and
Heliospheric Observatory) slit was collecting the scattered radiation
from the telescope mirror far away from the solar disk image, a class
X5.3/3b flare erupted on the solar disk, on 25 August 2001. During
the first phase of the flare a relative increase of a few percent was
detected at the head of the hydrogen Lyman continuum. After correction
from the instrumental parameters, the relative signal increase is 70%
at the head of the Lyman continuum (910 Å), and 190% in the C II 904
Å multiplet. Accounting for the area of the flare region, the local
increase of the radiance of the Lyman continuum and of the C II lines
is estimated to be a factor of several thousands. We compare this
result with other solar observations and models. <P />Appendix A is
only available in electronic form at http://www.edpsciences.org
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Title: Radiative transfer in cylindrical threads with incident
radiation
Authors: Gouttebroze, P.
2004A&A...413..733G Altcode:
Methods for the solution of non-LTE radiative transfer equations in
a cylinder, with external incident radiation, have been developed
in the framework of accelerated Λ-iteration methods. This paper
is restricted to the so-called one-dimension problem. The first
method under investigation treats a two-level atom in the Eddington
approximation: the comparison of results with a semi-analytical method
(restricted to homogeneous cylinders) is used to study the effects
of radius discretization. The second method removes the Eddington
approximation and uses detailed (multiray) angular integration of
intensities. Finally, the method is extended to a multilevel atom with
a treatment of radiative transfer in both lines and continua. It is
applied to a model hydrogen atom with 20 levels and one continuum,
with correction of the electron density. Convergence properties and
results are discussed.
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Title: Line profiles and intensity ratios in prominence models with
a prominence to corona interface
Authors: Labrosse, N.; Gouttebroze, P.; Heinzel, P.; Vial, J. -C.
2002ESASP.506..451L Altcode: 2002svco.conf..451L; 2002ESPM...10..451L
In this work we study the hydrogen, helium and calcium spectra
emitted by a one-dimensional prominence model in magneto-hydrostatic
equilibrium. The prominence slab consists of two parts: a cool
core where the plasma is optically thick for some lines, and a
prominence-to-corona transition region (PCTR) with a strong temperature
gradient. The models are defined by 5 parameters: temperature, pressure,
slab thickness, microturbulent velocity and altitude. We solve the NLTE
radiative transfer equations for all optically thick transitions. We
present line ratios between infrared, optical and EUV lines, as well
as line profiles. We show that the presence of a PCTR, where both
collisional and radiative excitations are important, affects H, He,
and Ca populations and emergent lines in different manners.
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Title: Radiative transfer effects on hydrogen (and helium) in the
solar atmosphere
Authors: Labrosse, N.; Li, X.; Habbal, S. R.; Gouttebroze, P.;
Mountford, C. J.
2002ESASP.506...13L Altcode: 2002svco.conf...13L; 2002ESPM...10...13L
In this work we present Non-Local Thermodynamic Equilibrium (non-LTE)
computations for hydrogen for a VAL-C model of the Sun's atmosphere. The
solar atmosphere is represented by a one-dimensional plane-parallel
horizontal slab. The purpose of this study is to investigate the effects
of the transfer of radiation in the chromosphere and the transition
region. In particular, we aim at understanding how the radiative
losses in the energy balance for electrons are affected by the non-LTE
radiative transfer, which has to be considered in the regions where
the temperature is less than 25000K. The numerical code used here
allows us to study the properties of, and the spectrum emitted by,
the hydrogen particles. The non-LTE radiative transfer equations (RT)
are solved for all optically thick resonance lines. The solutions of
the RT in the optically thick lines affect all population densities of
atoms and ions through the statistical equilibrium equations (SE). For
the VAL-C atmosphere model there is a peak around 6×10<SUP>3</SUP>K
in the net radiative cooling rates due to several lines and continua
from hydrogen. To our knowledge this peak has never been considered
when evaluating the radiative losses in the chromosphere in the frame
of solar wind modelling. We mention some consequences for solar wind
models in the description of the chromosphere and the transition
region which is often made under the assumption of full ionization
and optically thin plasma.
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Title: Prediction of line intensity ratios in solar prominences
Authors: Gouttebroze, P.; Labrosse, N.; Heinzel, P.; Vial, J. -C.
2002ESASP.505..421G Altcode: 2002solm.conf..421G; 2002IAUCo.188..421G
Solar prominences are made of relatively cool and dense plasma
embedded in the solar corona, supported and structured by the magnetic
field. Since this plasma is definitely out of LTE, the diagnosis
of physical conditions in prominences needs the use of specific
radiative transfer (RT) codes to predict the spectrum emitted by
models and compare it to observations. For optically thin lines, the
solution of RT equations in the transition itself is not required,
but the emitted intensities depend, via the statistical equilibrium
equations, on RT in other transitions which are optically thick. We
use two different sets of models. The first one contains monolithic
models defined by 5 parameters: temperature, pressure, thickness,
microturbulent velocity and altitude above the solar surface. For
each parameter, we assume a range of variation. For each model, the
values of the 5 parameters are randomly chosen within the corresponding
range of variation. The second set contains composite models made of
multiple layers, in order to simulate the penetration of radiation into
inhomogeneous prominences. We use NLTE radiative transfer codes to
compute the intensities of the lines of hydrogen, helium and calcium
emitted by each model. So, for any couple of lines, we may obtained
their intensity ratio as a function of the 5 parameters. We discuss
the behaviour of some of these intensity ratios as a function of the
principal parameters and construct distribution diagrams, which are
compared to different published observations.
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Title: Calcium to hydrogen line ratios in solar prominences
Authors: Gouttebroze, P.; Heinzel, P.
2002A&A...385..273G Altcode:
The ratio of Ca II 8542 Å to Hβ line intensities has been used for a
long time to diagnose the gas pressure in solar prominences. In this
paper we reconsider the theoretical dependence of E(8542)/E(Hβ ) on
the gas pressure, as originally computed by Heasley & Milkey (1978),
and extend this theoretical correlation to higher pressures. Firstly, we
revise the formation of calcium lines in prominences, using in parallel
two independently developed NLTE radiative transfer codes. Computations
consist of two subsequent steps: (i) the formation of hydrogen spectrum
(treated in a similar way as in Gouttebroze et al. 1993), and (ii)
the formation of calcium lines, using the electron-density structure
obtained in step (i). The influence of hydrogen Lyman lines on Ca II to
Ca III ionization is found to be very important for the determination
of calcium-to-hydrogen line ratios. In particular, the intensities
obtained for calcium lines at low pressures are significantly lower than
those obtained by Heasley & Milkey (1978), which is the result
of a greater Ca III/Ca II ratio. Our numerical results have been
further checked against an approximate analytical model. Secondly,
we have performed an extended computation using a large grid of
models covering different temperatures, gas pressures, geometrical
thicknesses, microturbulent velocities and prominence altitudes. For
temperatures lower than 10 000 K and pressures lower than 0.1 dyn
cm<SUP>-2</SUP>, the line ratio E(8542)/E(Hβ ) undergoes only small
variations, remaining between 0.2 and 0.3. At higher pressures (0.1
to 1 dyn cm<SUP>-2</SUP>), the behaviour of this ratio appears to be
strongly dependent on temperature: rapidly increasing below 6000 K,
moderately increasing between 6000 and 8000 K, and generally decreasing
at higher temperatures. A comparison of the present models with recent
observations of Stellmacher & Wiehr (2000) suggests the existence
of cool prominence structures with temperatures around 6000 K and gas
pressures higher than 0.1 dyn cm<SUP>-2</SUP>.
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Title: Challenges to Understand Stellar Chromospheres and Stellar
Activity: The Limit Case of Late-A and Early-F Stars
Authors: Freire Ferrero, R.; Gouttebroze, P.
2002EAS.....5...79F Altcode:
The onset of chromospheric activity appears at late-A and early-F
stars where theories predict atmospheres in radiative equilibrium
and shallow or non-existent convective zones. The detection of
Ly-α emission cores in several A and F stars, first with the IUE
satellite and then with the HST, gives evidence for the presence of
chromospheric layers in these stars up to B - V = 0. ^m19 (Catalano
et al. [CITE]). Semiempirical chromospheric models for Altair allowed
us (Freire et al. [CITE]) to explain the observed emission profiles
taking into account normal HI IS absorption. However, due to the very
high rotational velocity we analyzed alternative hypotheses like
the formation of Ly-α emissions into a corotating expanding wind,
but we ruled out this alternative because we obtained inconsistent
results. In addition, X-ray emission (originated surely in a corona)
strengthen the presence of a chromosphere. Here we place the problem
of chromospheric activity of late-A and early-F stars in the general
context of the formation of over-photospheric stellar layers, comparing
them with late-type star and solar cases.
---------------------------------------------------------
Title: Formation of helium spectrum in solar quiescent prominences
Authors: Labrosse, N.; Gouttebroze, P.
2001A&A...380..323L Altcode:
We present new non-LTE modelling of the helium spectrum emitted by
quiescent solar prominences. The calculations are made in the frame
of a one-dimensional plane-parallel slab. The physical parameters
of our models are the electron temperature, the gas pressure, the
slab width, the microturbulent velocity and the height above the
solar surface. In this paper, we present isothermal isobaric models
for a large range of temperature and pressure values. This work
brings considerable improvements over the calculations of Heasley
and co-workers \citep{hmp,hm2,hm3,hm4} with the inclusion in our
calculations of partial redistribution effects in the formation of the H
I Lyα, Lyβ, He I λ 584 Å and He Ii λ 304 Å lines. In addition we
consider detailed incident profiles for the principal transitions. The
statistical equilibrium equations are solved for a 33 bound levels
(He I and He Ii) plus continuum atom, and the radiative transfer
equations are solved by the Feautrier method with variable Eddington
factors. In this way we obtain the helium level populations and the
emergent line profiles. We discuss the influence of the physical
parameters on the helium level populations and on the main helium
spectral lines. The effect of helium abundance in the prominence plasma
is also studied. Some relations between singlet and triplet lines are
given, as well as between optically thin or thick lines, He I and He
Ii lines, and between the He I λ 5876 Å and H I λ 4863 Å lines. In
a future work this numerical code will be used for the diagnostic of
the prominence plasma by comparing the results with SUMER observations.
---------------------------------------------------------
Title: A ready-made code for the computation of prominence NLTE models
Authors: Gouttebroze, P.; Labrosse, N.
2000SoPh..196..349G Altcode:
A computer code is proposed for the computation of simple NLTE models
of solar prominences. These models consist of plane-parallel slabs,
with constant pressure and temperature, standing vertically above the
solar surface. Each model is defined by five parameters: temperature,
density, geometrical thickness, microturbulent velocity and height
above the solar surface. The code computes the electron density,
hydrogen level populations inside the slab, and determines the line
profiles and continua emitted by the slab. An example of application
of this code is given.
---------------------------------------------------------
Title: Modelling of Helium Spectrum in Solar Prominences
Authors: Labrosse, N.; Gouttebroze, P.; Vial, J. -C.
1999ESASP.448..503L Altcode: 1999mfsp.conf..503L; 1999ESPM....9..503L
No abstract at ADS
---------------------------------------------------------
Title: Modelling Of Helium Spectrum In Solar Prominences
Authors: Labrosse, N.; Gouttebroze, P.
1999ESASP.446..399L Altcode: 1999soho....8..399L
We present NLTE calculations for the neutral and ionized Helium
spectrum in quiescent solar prominences. The Hydrogen and Helium
atoms are multi-level model atoms, including for Helium the three
stages of ionization. Departures from LTE are allowed for each
level. We investigate the formation of lines and continuum within
the frame of one-dimensional, isothermal and isobaric static slab
models. The numerical code used for these calculations allows also
the study of Partial Redistribution effects for several lines. The
computation results are compared first with former works to see the
improvements in the numerical and theoretical treatment, and then with
SOHO observations of quiescent prominences at helium wavelengths. A
study of the prominence plasma parameters thus can be made.
---------------------------------------------------------
Title: Chromospheric models for late A-type stars
Authors: Gouttebroze, P.; Ferrero, R. Freire; Marilli, E.; Catalano, S.
1999A&A...348..198G Altcode:
The chromospheres of alpha Aql (Altair) and alpha Cep (Alderamin)
are investigated. Different semi-empirical model atmospheres are
constructed, and the predicted spectra are compared to the observations
of the hydrogen Lyman-alpha line (IUE) and carbon (both neutral and
ionized) multiplets (GHRS-HST). It is found that chromospheric models
at low temperature ( ~ 10000 K) which fit the Lalpha line, produce
C ii lines in absorption, contrary to observations. Among the models
investigated, only those with a mean temperature of ~ 20000 K are able
to fit simultaneously the Lalpha and C ii lines. Provisional reference
models are proposed for alpha Aql. The lower emission of alpha Cep
with respect to alpha Aql is better explained by a difference of
column mass than by a difference of temperature. The chromospheric
column mass ratio (alpha Cep / alpha Aql) is estimated to about
0.8. For both stars, the relatively narrow dips of the C ii emission
feature cannot be of stellar origin, owing to the fast rotation,
but of interstellar absorption nature. Based on observations by the
IUE satellite collected at Villafranca ESA IUE Observatory and at
the GSFC NASA IUE Observatory. Also based on observations made with
the NASA/ESA Hubble Space Telescope, obtained from the data archive,
at the Space Telescope Science Institute, which is operated by the
Association of Universities for Research in Astronomy, Inc., under
contract NAS 5-26555.
---------------------------------------------------------
Title: Oscillations of the upper chromosphere
Authors: Gouttebroze, P.; Vial, J. -C.; Bocchialini, K.; Lemaire,
P.; Leibacher, J. W.
1999SoPh..184..253G Altcode:
Variations of intensity and wavelength in several UV lines have been
observed with the SUMER spectroheliometer onboard SOHO, and they have
been analysed to obtain oscillation spectra and phase differences
between lines of different ions. Lines intensities of neutral or
singly ionized atoms (with temperature of formation ≤ 30 000 K)
exhibit an increase of oscillatory power between 2.5 and 7 mHz, which
may be considered as the signature of p modes. Lines of highly ionized
elements (with a temperature of formation ≥ 50 000 K) yield power
spectra which are continuously decreasing with frequency. Brightness
variations of the continuum at different wavelengths between 1000
and 1400 Å present oscillations in the same frequency range. Thus,
p modes seem to be efficiently stopped by the transition region. No
clear evidence is found for the existence of a chromospheric oscillation
mode. Phase comparisons between lines formed at different altitudes
(in particular Si i and Si ii) indicate that these lines oscillate in
phase, within the precision of the measurements.
---------------------------------------------------------
Title: Emission of hydrogen lines by moving solar prominences.
Authors: Gontikakis, C.; Vial, J. -C.; Gouttebroze, P.
1997A&A...325..803G Altcode:
We study the radiative transfer processes occurring in a plane-parallel
slab standing vertically above the chromosphere and moving upward
as a solid body. This structure simulates a prominence in the phase
of eruption or a quiescent prominence where the plasma presents bulk
velocities. We use partial redistribution for the description of the
resonance scattering in the hydrogen Lα and Lβ lines. We compute
the Lα, Lβ and Hα emergent line profiles of hydrogen for different
velocities. We derive the variation of the emitted intensities as a
function of the velocity for various temperatures and thicknesses. We
discuss our results in view of the diagnostic of erupting prominences
in Lyman lines that SOHO observations can provide.
---------------------------------------------------------
Title: Spectral diagnostics for eruptive prominences
Authors: Gontikakis, C.; Vial, J. -C.; Gouttebroze, P.
1997SoPh..172..189G Altcode: 1997ESPM....8..189G
The diagnostic of eruptive prominences needs the development of
new tools. Here we propose the Lyman and Balmer lines of hydrogen,
which are important in the radiative budget. In the NLTE radiative
transfer calculations, we include the effect of the outward motion
of the structure associated with the eruption of the prominence. The
treatment of the resonance scattering of Lα and Lβ with partial
redistribution gives higher intensities, and a higher ionization than
the complete redistribution, but the two approaches converge to the same
solution as the velocity increases. As a first step in the diagnostic,
we present new results concerning the variation of the integrated
intensities of hydrogen lines with respect to the radial velocity.
---------------------------------------------------------
Title: Formation of CA II Lines in Solar Prominences
Authors: Gouttebroze, P.; Vial, J. -C.; Heinzel, P.
1997SoPh..172..125G Altcode: 1997ESPM....8..125G
We compute the profiles of the resonance lines and infrared
triplet of ionized calcium emitted by some representative models of
prominences. These models consist of plane-parallel slabs of different
temperatures, pressures and thicknesses, standing vertically above
the solar surface. These slabs are assumed to be observed at the limb,
and to be perpendicular to the line of sight. They are irradiated by
the Sun on both sides, and the incoming intensities, at every relevant
wavelength, are taken from observations. The model atom includes 3
stages of ionization (Cai, Caii and Caiii) with 5 discrete levels for
Caii. We study the relations between emitted intensities and physical
properties of the slabs, and compare the intensities emitted in Caii and
hydrogen lines for the same set of models. As a result of ionization,
the intensity decreases more rapidly with temperature in Caii lines than
in Hi lines, so that the ratio of Caii to Hi line intensities may be
used as a temperature indicator. The intensity ratio between resonance
and infrared lines of Caii depends principally on the optical thickness
of the structure. At high pressure and low temperature, the ratio
Caii 8542Å/Hβ is found to increase with pressure. This behaviour,
which is due to the saturation of Hβ, is opposite to that found by
Heasley and Milkey (1978) for low pressures (optically thin structures).
---------------------------------------------------------
Title: Searching for chromospheric Lyman-α emission in A-F stars
from IUE high resolution spectra.
Authors: Marilli, E.; Catalano, S.; Freire Ferrero, R.; Gouttebroze,
P.; Bruhweiler, F.; Talavera, A.
1997A&A...317..521M Altcode:
With the aim of locating the boundary for the onset of chromospheric
emission in the H-R diagram we have undertaken a spectroscopic study
of the hydrogen Ly-α, using the IUE short wavelength spectrograph
in the high resolution mode. We report here on the analysis of IUE
spectra of 11 A-F type stars. We have detected Ly-α emission in
stars as early as A7 (B-V=0.19), establishing a new limit for the
presence of chromospheres. The constant or the slowly decreasing
trend of the Ly-α flux for B-V<0.5 is related to the decreasing
trend of X-ray emission in the same spectral type region. From the
interstellar absorption feature affecting the stellar Ly-α emission,
the Hi column density is estimated.
---------------------------------------------------------
Title: New Insights on Late-A and Early-F Star Activity
Authors: Freire Ferrero, R.; Catalano, S.; Marilli, E.; Gouttebroze,
P.; Talavera, A.; Bruhweiler, F.
1997A&AT...14...41F Altcode:
The onset of chromospheric activity in late-A and early-F stars is
here discussed. The detection of Ly- emission core in several A and
F atars with the IUE satellite, gives evidence for the presence of
chromospheric layers in these stars up to B - V = 0m.19 (Marilli et al.,
1996). Semiempirical chromospheric models for Altair allowed us (Freire
Ferrero et al., 1995) to explain the observed emission profiles taking
into account normal H I interstellar (IS) absorption. However, due to
the very high rotational velocity, we analysed alternative hypotheses
to explain the observed emissions: (1) circumstellar or shell matter;
(2) co-rotating expanding optically thin wind. We ruled out these
hypotheses because their effects are negligible and as a consequence,
this result reinforces the chromospheric origin of the observed Ly-
core in Altair. The stars of our sample, having observed Ly- profilies
similar to Altair's and similar stellar and IS properties, should
reproduce similar chromospheric behaviour. Here we discuss several
important questions that are raised by these results.
---------------------------------------------------------
Title: Diagnostic and observations of quiescent and
Authors: Vial, J. -C.; Gontikakis, C.; Bocchialini, K.; Gouttebroze, P.
1997IAUJD..19E..55V Altcode:
We present a new diagnostic tool for investigating the plasma conditions
in a moving structure in the solar corona, such as an eruptive filament
or prominence. It relies on NLTE radiative transfer calculations and
the signatures of outward directed velocities on Lyman and Balmer lines
profiles. Preliminary observations with SUMER on SOHO are discussed.
---------------------------------------------------------
Title: Solar chromospheric structures as observed simultaneously in
strong UV lines. II. Network and cell modelling.
Authors: Bocchialini, K.; Gouttebroze, P.
1996A&A...313..949B Altcode:
Mean line profiles of the quiet Sun spectrum, recorded simultaneously
in Lα, Lβ, Ca II H and K, and Mg II h and k lines with the OSO-8/LPSP
spectrometer were derived for structures such as supergranulation cell
and network. We compare these observed profiles with theoretical ones
computed by Vernazza et al. (1981, VAL81) and by Fontenla et al. (1993,
FAL93). We also present our own theoretical profiles : with our non-LTE
radiative transfer codes, we compute the line profiles corresponding
to different atmospheric models, derived from the reference VAL and FAL
models. Finally, we propose two new semi-empirical models, NET and CEL,
which are in better agreement with the network and cell line profiles
observed by OSO-8.
---------------------------------------------------------
Title: Prominence Thread Models Including Ambipolar Diffusion
Authors: Fontenla, J. M.; Rovira, M.; Vial, J. -C.; Gouttebroze, P.
1996ApJ...466..496F Altcode:
We present a study of the modeling of prominence slabs. Our models
consider a collection of threads in energy balance with the surrounding
corona and submitted to illumination from the underlying chromospheric
layers. The models are isobaric, but temperature variations within
the slab occur as a result of the energy balance constraint. We
compute the non-LTE radiative transfer for a hydrogen model atom
with five bound levels. The ionization is treated consistently with
non-LTE radiative transfer and ambipolar diffusion (AD). The AD
also affects the energy balance because of the transport of hydrogen
ionization energy. We compute the emitted Lyman and Balmer spectra of
our models and compare them with the observations. We find that the
consideration of ambipolar diffusion increases the emission in Lyβ
(and higher members of the Lyman series) as compared with the other
lines. This contrasts with isothermal models that yield Lyβ emission
that is too low. However, the AD models give excessive Lyβ emission,
viz., too small a Lyα/Lyβ ratio compared with observations. We also
compute models that include a cold core in which mechanical energy is
dissipated. These models increase the Hα/Lβ ratio to values similar to
the observed values for a moderate number of threads along the line of
sight. However, these models still give too low a Lyα/Lyβ ratio. We
conclude that the prominence observations in Lyβ show intensities
that are not compatible with a steady state, field-aligned interface
between the cold prominence and the hot coronal material. Also, the
observations are not consistent with an isothermal slab isolated from
the corona. Consequently, we suggest that at the prominence-corona
interface, there is a substantial angle between the temperature gradient
and the field, although this angle is significantly smaller than 90°.
---------------------------------------------------------
Title: VizieR Online Data Catalog: Solar chromospheric
structures. II. (Bocchialini+, 1996)
Authors: Bocchialini, K.; Gouttebroze, P.
1996yCat..33130949B Altcode:
Mean line profiles of the quiet Sun spectrum, recorded simultaneously
in Lα, Lβ, Ca II H and K, and Mg II h and k lines with the OSO-8/LPSP
spectrometer were derived for structures such as supergranulation cell
and network. We compare these observed profiles with theoretical ones
computed by Vernazza et al. (1981, VAL81) and by Fontenla et al. (1993,
FAL93). We also present our own theoretical profiles : with our non-LTE
radiative transfer codes, we compute the line profiles corresponding
to different atmospheric models, derived from the reference VAL and FAL
models. Finally, we propose two new semi-empirical models, NET and CEL,
which are in better agreement with the network and cell line profiles
observed by OSO-8. (2 data files).
---------------------------------------------------------
Title: The chromospheric limit at late-A stars
Authors: Catalano, S.; Freire Ferrero, R.; Marilli, E.; Gouttebroze,
P.; Talavera, A.; Bruhweiler, F.
1996ASPC..109..591C Altcode: 1996csss....9..591C
No abstract at ADS
---------------------------------------------------------
Title: Nonadiabatic Computations of Solar P-Modes
Authors: Gouttebroze, P.; Provost, J.; Berthomieu, G.; Toutain, T.;
Morel, P.
1995ESASP.376b..53G Altcode: 1995soho....2...53G; 1995help.confP..53G
A set of p-mode eigenfrequencies and eigenfunctions is computed
both in adiabatic and nonadiabatic case, using different solar
models. Concerning the treatment of radiation for the p-mode
computations, the effects diffusion and Eddington approximations
are compared. Convection effects are neglected, but the different
formulations of the "frozen" convection approximation (e.g. Unno
et al. 1989) are investigated. From the eigenfunctions so computed,
the authors deduce the phase difference between intensity and Doppler
shift variations integrated on the solar disk. The ratio of intensity
to velocity amplitudes is also determined. Eigenfrequencies, phase
differences and amplitude ratios are compared to available observations.
---------------------------------------------------------
Title: Chromospheric Models for ALTAIR (A7 IV--V)
Authors: Ferrero, R. Freire; Gouttebroze, P.; Catalano, S.; Marilli,
E.; Bruhweiler, F.; Kondo, Y.; van der Hucht, K.; Talavera, A.
1995ApJ...439.1011F Altcode:
The star, Altair (A7 IV-V), is clearly shown to have Lyman-alpha
emission of chromospheric origin, while no evidence is found for the Mg
II emission reported in previous investigations. We present non-Local
Thermodymanic Equilibrium (non-LTE) semiempirical models incorporating
partial redistribution of the chromosphere of Altair that reproduce the
observed Lyman-alpha emission and the Mg II resonance absorption at 2800
A. We unambiguously establihed that chromospheres exist at spectral
types as early as A7 on the main sequence, and we also demonstrate
that it very unlikely that the observed emission originates in a
corotating expanding wind. This result represents a new challenge for
chromospheric heating theories. It may indicate that both differential
rotation and convection layers, at least near the equator, exist in
this fast rotating (v sin i = 220 km/s) star.
---------------------------------------------------------
Title: Theoretical correlations between prominence plasma parameters
and the emitted radiation.
Authors: Heinzel, P.; Gouttebroze, P.; Vial, J. -C.
1994A&A...292..656H Altcode:
Recently a set of 140 prominence NLTE models has been computed using
the best available numerical techniques (Gouttebroze et al. 1993,
hereafter GHV). Models are represented by one-dimensional (1D) slabs
vertically standing on the solar surface and irradiated by photospheric
and chromospheric radiation. They are parametrized by the gas pressure
and temperature (uniform), the geometrical thickness of the 1D slab,
the microturbulent velocity and the height above the solar surface. As
outputs we obtained several physical quantities and optical parameters
like the electron density, the total hydrogen density, the optical
thickness in hydrogen lines and continua, spectral line intensities
etc. (see GHV). In order to establish mutual correlations between
various plasma parameters and the basic characteristics of the
synthesized hydrogen spectrum, we construct some basic correlation
curves. A very important relation already mentioned in GHV concerns the
plasma emission measure found to be closely related to the integrated
intensity of the Balmer Hα line. We present several other correlations
which can be divided into four categories: (i) relations between
radiation properties themselves; (ii) radiation properties versus
plasma parameters; (iii) the Hα source function behaviour; and (iv)
correlations between plasma parameters. Together with the 24 presented
figures, we discuss the physical interpretation of these correlations
and we give some hints for their application to the observed data. When
appropriate, we also compare our results with existing observations.
---------------------------------------------------------
Title: An Eulerian approach for the computation of oscillation
mode visibility.
Authors: Gouttebroze, P.; Toutain, T.
1994A&A...287..535G Altcode:
We propose a method to compute the visibility of nonradial oscillation
modes for a star observed in the continuum. This method, based on the
use of Eulerian coordinates, remains valid whenever the geometrical
thickness of the emitting layer cannot be neglected. Some numerical
tests are performed for comparison with the previous formulation of
Dziembowski (1977), based on the use of Lagrangean coordinates.
---------------------------------------------------------
Title: Theoretical Correlations Between Various Prominence Parameters
Authors: Heinzel, P.; Gouttebroze, P.; Vial, J. -C.
1994scs..conf..439H Altcode: 1994IAUCo.144..439H
The authors present some examples of important correlations between the
prominence plasma parameters and radiation properties. For example,
the plasma emission measure was found to be closely related to the
integrated Hα line intensity which provides a new diagnostic tool
for determination of plasma densities.
---------------------------------------------------------
Title: Observed Chromospheric Profiles Compared with Theoretical Ones
Authors: Bocchialini, K.; Gouttebroze, P.; Vial, J. -C.
1994emsp.conf...49B Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Effects of Ambipolar Diffusion on Prominence Thread Models
Authors: Rovira, M. G.; Fontenla, J. M.; Vial, J. -C.; Gouttebroze, P.
1994scs..conf..315R Altcode: 1994IAUCo.144..315R
The authors have improved previous model calculations of the
prominence-corona transition region including the effect of the
ambipolar diffusion in the statistical equilibrium and energy balance
equations. They show its influence on the different parameters that
characterize the resulting prominence theoretical structure. They
take into account the effect of the partial frequency redistribution
in the line profiles and total intensities calculations.
---------------------------------------------------------
Title: The hydrogen spectrum of model prominences.
Authors: Gouttebroze, P.; Heinzel, P.; Vial, J. C.
1993A&AS...99..513G Altcode:
The emission of hydrogen lines and continua from solar prominences is
investigated using a set of 140 simple models, covering the range of
physical conditions usually assumed for these objects. These models
are plane-parallel, isobaric and isothermal. The computations have been
carried out using a 20 level plus continuum hydrogen atom, and taking
into account the effects of partial frequency redistribution in the
Lyman-alpha and beta lines. The aim of these computations is twofold:
firstly, to describe the variations of hydrogen lines and continua
emitted by prominences when physical conditions vary. Secondly, to
provide observers with some diagnostic tool to interpret data such as
intensity ratios, line widths, etc... The results of computations are
given as mixed table-figure panels, each of them corresponding to a
given model and summarizing the associated physical parameters and
the principal features of the emitted hydrogen spectrum. Finally,
for some specific parameters (or couple of parameters), we present
figures illustrating the variations of these quantities across the
whole set of models.
---------------------------------------------------------
Title: Visibility of solar p-modes
Authors: Toutain, T.; Gouttebroze, P.
1993A&A...268..309T Altcode:
Visibility functions of low-degree nonradial oscillations are
derived here for solar irradiance measurements in the visible
continuum. Corrections due to opacity variations in the photosphere
are taken into account and this both in adiabatic and nonadiabatic
cases. The computations show that opacity effects are not negligible
and substantially attenuate the emergent intensity. Likewise the
nonadiabatic effects have a large influence on the flux perturbations
and should be allowed for. Using the observed fluxes from the IPHIR
experiment the theoretical visibility functions provide the p-mode
energies. The best agreement with observations is obtained in two
different cases: isothermal oscillation corresponding to very short
relaxation times in the photosphere, or blackbody approximation
(i.e. negligible opacity variations).
---------------------------------------------------------
Title: Visibility Functions for Solar Irradiance Measurements
Authors: Toutain, T.; Gouttebroze, P.
1993ASPC...42..131T Altcode: 1993gong.conf..131T
No abstract at ADS
---------------------------------------------------------
Title: Possible detection of Lyman alpha emission in the A7 III star
gamma Bootis
Authors: Marilli, E.; Catalano, S.; Freire Ferrero, R.; Gouttebroze, P.
1992A&A...265..643M Altcode:
We analyze the archive high dispersion IUE spectrum SWP 10885 of Gamma
Boo (A7 III) in the Ly-alpha region, using our own software. A faint
stellar emission overlayed by a saturated interstellar absorption is
detected. This result and the previous detection of Ly-alpha emission
in Altair and Alpha Cep do suggest that the presence of chromospheric
emission is a common characteristic of main sequence and giant stars
of spectral type A7.
---------------------------------------------------------
Title: Chromospheric Lyman Alpha Emission in A-F Stars
Authors: Marilli, E.; Catalano, S.; Ferrero, R. F.; Gouttebroze, P.;
Bruhweiler, F. C.; Talavera, A.
1992ASPC...26..178M Altcode: 1992csss....7..178M
No abstract at ADS
---------------------------------------------------------
Title: The onset of chromospheres in A-type stars
Authors: Freire Ferrero, R.; Catalano, S.; Marilli, E.; Gouttebroze, P.
1992sccw.conf...95F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The chromospheric Lyman-alpha emission of ALTAIR (A7 IV-V).
Authors: Catalano, S.; Marilli, E.; Ferrero, R. F.; Gouttebroze, P.
1991A&A...250..573C Altcode:
The definition of the spectral type along the main sequence where
chromospheres appear is of crucial importance for the study of the
stellar structure and the chromospheric heating mechanism. Due to the
bright UV continuum and the fast rotation typical of early type stars,
the Ly-alpha emission core remains the only good chromospheric indicator
in late A-type stars. Altair (A7IV - V) lays just in the spectral
type range where the most common chromospheric and transition region
indicators are not generally observed. The detection of the Ly-alpha
emission core and coronal X-ray emission makes Altair a key star in
this respect. Different methods which make it possible to eliminate the
geocoronal Ly-alpha emission from high dispersion IUE spectra obtained
with the large aperture are examined. Using four long exposure images,
a well defined Ly-alpha emission profile of chromospheric origin
showing a wide central IS absorption is obtained for Altair.
---------------------------------------------------------
Title: The Onset of Chromospheres in A-Type Stars - the ALTAIR Affair
Authors: Catalano, S.; Gouttebroze, P.; Marilli, E.; Freire Ferrero, R.
1991LNP...380..466C Altcode: 1991IAUCo.130..466C; 1991sacs.coll..466C
Here we present preliminary results on the study of the chromosphere of
Altair from L high dispersion profiles. We report also the detection
of L chromospheric emission from Cep (A7 V) and TrA (F0 V) with the
ME. We show that chromosphere may exist up to B - V = 0.22. The possible
heating mechanism, magnetic or nonmagnetic, for the chromosphere of
these stars is also discussed.
---------------------------------------------------------
Title: L'héliosismologie ou l'exploration des profondeurs solaires.
Authors: Gouttebroze, Pierre
1990LAstr.104..406G Altcode:
It is pointed out that helioseismology has made it possible to refine
the existing model of the solar internal structure. It has also been
used to study interior movements of the sun, which are important for
understanding the solar cycle. By making it possible to test models
of the solar interior, helioseismology also contributes to solving
various problems of basic physics, including the question of the state
of matter at high temperature and pressure, the nature of neutrinos,
and the existence of hypothetical massive particles which may be of
considerable cosmological significance.
---------------------------------------------------------
Title: The chromospheric Lyman alpha core emission of Altair
Authors: Freire Ferrero, R.; Cataloano, S.; Gouttebroze, P.;
Marilli, E.
1990ESASP.310..315F Altcode: 1990eaia.conf..315F
No abstract at ADS
---------------------------------------------------------
Title: Radiative transfer in cylindrical objects by the discrete
ordinate method
Authors: Gouttebroze, P.
1990A&A...228..295G Altcode:
The discrete ordinate method of Wick-Chandrasekhar may be extended to
the case of radiative transfer in infinitely long cylinders, in the
Eddington approximation. The only important modification consists in
replacing the exponentials by modified Bessel functions. As in the
cases of planar or spherical geometries, the method is restricted
to homogeneous media. The method may be used to obtain a rapid
insight in radiative transfer phenomena arising for instance in
solar prominences or coronal loops, or to check the precision of more
complicated numerical methods. It may be easily extended to partial
redistribution problems.
---------------------------------------------------------
Title: Multi-Thread Structure as a Possible Solution for the L-Beta
Problem in Solar Prominences
Authors: Vial, J. -C.; Rovira, M.; Fontenla, J.; Gouttebroze, P.
1990LNP...363..282V Altcode: 1990IAUCo.117..282V; 1990doqp.coll..282V
Following the pioneering works of Heasley, Mihalas, Milkey and Poland
(see e.g. Heasley and Milkey, 1983) who built non LTE onedimensional
models of solar prominence, much attention has been paid to the
spectral signatures of the Lyman lines as observed with OSO 8 (Vial,
1982a). In spite of a better treatment of the frequency redistribution
and boundary conditions, one-dimensional low-pressure models lead to
Lyman intensities much lower than observed ones (Heinzel, Gouttebroze
and Vial, 1987). Different atomic processes of formation of hydrogen
lines (Cooper, Ballagh and Hubeny, 1988) or the inclusion of a
Prominence Corona Transition Region or PCTR (Heinzel, Gouttebroze and
Vial, 1988) have been proposed to explain this discrepancy. We present
here a different approach where the filamentary nature of prominences
which provides the hydrogen lines with different opacities, offers
their photons different escaping possibilities. The thread models
we use derive from an energy equation where radiative losses are
balanced by conductive flux (Foutenla and Rovira, 1983, 1985). We
show that no superposition of threads gives good values of Lyman a,
and H a intensities for too high and too low pressures. Solutions are
found for pressure around 0.05-0.1 dyn/cm2 and a number of threads
between 100 and 400. Two improvements have been performed: first, the
inclusion of Partial Redistribution leads to a decrease of L (and L)
intensity and models now require a higher number of threads; second,
the inclusion of the ambipolar diffusion along the steep temperature
gradient which changes the hydrogen ionization in the lower regions
(Foutenla, Avrett and Loeser, 1990). The new run of temperature and
density implies more material at low temperatures and hydrogen lines
intensities increase. A solution for the L problem can be found for
a pressure of about 0.1 dyn cm-t2. However the H intensity appears to
be rather high. Moreover, the number of threads required (about 200)
is far larger than the number derived by Zirker and Koutchmy (this
issue) and Mein (this issue) from observed H profiles. Our neglect
of the radiative interaction between threads may explain our results
(Heinzel, this issue). To conclude, these computations of non-lte
radiative transfer in realistic geometrical and physical models, appear
to be a promising path for the investigation of solar prominences.
---------------------------------------------------------
Title: Radiative Transfer in Cylindrical Prominence Threads
Authors: Gouttebroze, Pierre
1990LNP...363..278G Altcode: 1990IAUCo.117..278G; 1990doqp.coll..278G
Whereas radiative transfer in Astrophysics generally deals with
plane-parallel or spherical objects, the use of other geometries is
desirable in some particular cases. We propose to treat infinitely
long cylinders, a geometry which is relevant to, e. g., prominence
threads or coronal loops. We study two different situations : the first
one corresponds to an incident radiation field which is symmetrical
by rotation around the axis of the cylinder, and may be reduced to a
1-dimension formalism. This problem is usually treated in an approximate
way, replacing the cylinder by an equivalent slab, but a real solution
in cylindrical coordinates can give a better precision. The other
case is that of anisotropic incident radiation, which results in a
2-dimension problem. We review the different available techniques
to solve these two kinds of problems, and discuss their range of
applicability and their utility with respect to the diagnostic of
prominence threads. Prospects for new methods that could be developed
are also examined.
---------------------------------------------------------
Title: Solar Atmospheric Dynamics. III. The Effect of Acoustic Waves
on the MG II K Line Profile
Authors: Gouttebroze, Pierre
1989ApJ...337..536G Altcode:
The use of acoustic waves to obtain realistic profiles for the solar
Mg II resonance lines without using ad hoc parameters such as micro-
and macroturbulence is studied. One-dimensional models are used
which treat the waves nonlinearly. Line profiles are calculated with
radiative transfer equations which are expressed in the observer's
frame, accounting for the effects of partial redistribution in
frequency and direction. It is found that the model can reproduce the
observed k3 reversal and the global intensity. It is suggested that
two-dimensional computations are necessary to reproduce the observed
peak-to-peak distance.
---------------------------------------------------------
Title: Multithread Structure as a Possible Solution for the L-beta
Problem in Solar Prominences
Authors: Vial, J. C.; Rovira, M.; Fontela, J.; Gouttebroze, P.
1989HvaOB..13..347V Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Radiative Transfer in Cylindrical Prominence Threads
Authors: Gouttebroze, P.
1989HvaOB..13..305G Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The diagnostic and modelling of the solar atmosphere through
non-LTE radiative transfer: some results and prospects.
Authors: Gouttebroze, Pierre; Vial, Jean-Claude; Lemaire, P.
1989mse..proc..245G Altcode:
The authors describe new results from non-LTE radiative transfer
calculations for solar UV continua and line profiles. The new non-LTE
codes include partial frequency redistribution in the lines, moving
atmospheres with differential velocities, and can treat finite objects
with external irradiation (loops, prominences). Selected examples are
given for: (1) a static atmosphere (plage); (2) a moving atmosphere
(waves); and (3) free standing slabs (prominences).
---------------------------------------------------------
Title: Visibility of nonradial pulsation modes in solar continuum
intensity measurements.
Authors: Toutain, T.; Gouttebroze, P.
1988ESASP.286..241T Altcode: 1988ssls.rept..241T
A calculation of the continuum emission integrated over the solar disk,
and of its perturbations arising from different nonradial pulsation
modes, is presented. In addition to geometrical effects (variations
of the emitting areas) and Planck function variations studied in
previous similar calculations, the authors examine the influence of
opacity changes in H- (the principal absorber at the wavelengths under
consideration). The computations are carried out numerically for 500
and 826 nanometers, which correspond to different channels of the
IPHIR/PHOBOS experiment. The relative importance of these different
processes of flux modulation is discussed as a function of oscillation
period and modal type.
---------------------------------------------------------
Title: A Method for Calibrating, in Absolute Flux Units, CA II H
Profiles of Late Type Stars Observed at ESO
Authors: Castelli, F.; Gouttebroze, P.; Beckman, J.; Crivellari, L.;
Foing, B.
1988IAUS..132..153C Altcode:
The authors have applied to the Sun a method for calibrating, in
absolute flux units, Ca II H profiles of late-type stars. After
comparing, in the region 3948 - 3882 Å, an LTE synthetic spectrum
with the data of the solar flux atlas by Kurucz et al. (1984), they
have defined the wavelength ranges where observations agree with
computations, based on specific radiative equilibrium models and
collisional broadening parameters. By fitting in these regions the
spectrum of the moon observed at ESO with the corresponding synthetic
spectrum, the authors derived a calibration factor that enables them
to calibrate, in absolute flux units, the whole observed range.
---------------------------------------------------------
Title: Non LTE modelling of prominences.
Authors: Heinzel, P.; Gouttebroze, P.; Vial, J. -C.
1988dssp.conf...71H Altcode:
The authors present the results on non-LTE computations performed in
the major lines and continua of the hydrogen atom. The prominence is
represented by a slab illuminated by the neighbouring chromosphere and
corona. Classical models are recomputed and it appears that the low
pressure model represent well the observed Lα profiles. However the
Lβ-computed value is much lower than the observed one. Preliminary
computations where a transition region to the corona is included that
the Lβ line may be improved.
---------------------------------------------------------
Title: Chromospheric Seismology
Authors: Gouttebroze, P.
1988IAUS..123..421G Altcode:
The aim of the present study is to examine whether seismologic
diagnostic techniques may be used to improve the models of the solar
chromosphere. The author is mainly concerned with oscillations observed
in the cores of strong lines such as the resonance lines of Ca II or
Mg II.
---------------------------------------------------------
Title: Formation of the hydrogen spectrum in quiescent prominences -
One-dimensional models with standard partial redistribution
Authors: Heinzel, P.; Gouttebroze, P.; Vial, J. -C.
1987A&A...183..351H Altcode:
One-dimensional isothermal-isobaric static slab models are used to study
departures from complete frequency redistribution (CRD) in hydrogen
lines for quiescent solar prominences. Partial redistribution (PRD)
effects on the hydrogen L-alpha line are shown to be significant
in the near wings in addition to the far wings of L-alpha. It is
suggested that strong symmetrical peaks found in the theoretical
PRD L-alpha profiles are due to partially coherent penetration of
the incidence double-peaked solar L-alpha. The present results are
found to be consistent with OSO-8/LPSP observations and with UVSP/SMM
data. The possible interplay between the effects of lateral transport
or radiation, level-interlocking, and PRD is considered.
---------------------------------------------------------
Title: Analysis of the MG II resonance lines in the spectrum of
Sirius.
Authors: Freire Ferrero, R.; Gouttebroze, P.; Talavera, A.
1987A&A...173..315F Altcode:
The atmospheric layers above the photosphere of Sirius A (Alpha CMa,
AlV) are analyzed using high-resolution spectra of the Mg II resonance
lines obtained with the Copernicus and IUE satellites. The line
cores are formed at optical depths so small that an extension of the
existing photospheric models for Sirius is necessary. Two tentative
sets of atmospheric models based on the Bell and Dreiling (1981 and
1982) photospheric model are investigated: (1) the photospheric model
prolonged toward the exterior, with different temperature plateaux
(6000, 7000, and 7500 K); and (2) a chromospherelike temperature rise
operating about m = 0.0001 g/sq cm. Both kinds of atmospheric models may
be invoked at present as alternative models for the external atmospheric
layers in Sirius. The observations are compared with computed NLTE
line profiles with complete or partial redistribution. An abundance
ratio of Mg/H = 0.000035 is deduced. The contribution of the Mg II
interstellar absorption is also discussed.
---------------------------------------------------------
Title: Structures fines chromosphériques: nouveaux résultats de
la caméra de la région de transition.
Authors: Foing, B. H.; Dame, L.; Vial, J. C.; Gouttebroze, P.; Martic,
M.; Bonnet, R. M.
1987JAF....29...15F Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Non-Lte Modelling of Prominences
Authors: Heinzel, P.; Gouttebroze, P.; Vial, J. C.
1987dssp.work...71H Altcode: 1987ASSL..150...71H
No abstract at ADS
---------------------------------------------------------
Title: Partial redistribution effects in the formation of hydrogen
lines in quiescent prominences.
Authors: Heinzel, P.; Gouttebroze, P.; Vial, J. C.
1986NASCP2442..155H Altcode: 1986copp.nasa..155H
Departures from complete frequency redistribution (CRD) in hydrogen
lines are investigated for solar prominences. Partial redistribution
effects (PRD) are found both in the wings (their already known lowering)
and in the central part of the L alpha line; a new feature is evidenced
here: the partially coherent scattering in the near wings of the
line leads to a double-peaked profile mirroring the incident solar
radiation. With a low density model, we obtain a good agreement with
OSO 8 observed profiles. On the contrary, the PRD computed L beta
profile (lower density, no reversal) departs from the observed one,
a result which calls for more progress in terms of non-LTE transfer
and modelling.
---------------------------------------------------------
Title: Emission of Lyman-α radiation by solar coronal
loops. II. Filtergram analysis.
Authors: Tsiropoula, G.; Alissandrakis, C.; Bonnet, R. M.; Gouttebroze,
P.
1986A&A...167..351T Altcode:
The authors study active region loops, observed on Lα high resolution
filtergrams obtained with a rocket borne instrument. Some formulae or
diagrams are given for the computations of Lα and Hα intensities
emitted by homogeneous loop models. The dimensions and emitted
intensities of the observed loops being known, the authors determine
the variations of temperature, pressure and density inside these
objects under the assumption of constant temperature and hydrostatic
equilibrium. The influence of temperature gradient and mass flow
on the results is discussed, and an alternative model with radial
temperature increase is envisaged. The case of an isolated loop with
a larger diameter is also discussed.
---------------------------------------------------------
Title: Fast approximations for the R(II-A) redistribution function
Authors: Gouttebroze, P.
1986A&A...160..195G Altcode:
Approximations are proposed for the computation of the R<SUB>II-A</SUB>
redistribution function (which describes the redistribution of
frequencies for photons scattered coherently in the atom's frame). These
approximations are particularly efficient on vector computers. Precision
and timing properties of the method are examined for a typical line
formation problem (Lyα in the solar atmosphere).
---------------------------------------------------------
Title: Non-LTE models of solar prominences
Authors: Heinzel, P.; Vial, J. C.; Gouttebroze, P.; Rompolt, B.
1986CoSka..15..183H Altcode:
The authors briefly review some representative non-LTE models of solar
prominences, developed during the past decade. Particular attention is
devoted to recent interpretation of hydrogen Lyman α line profiles
in quiescent prominences and to the solution of the non-LTE problem
for moving active prominences. Finally, the authors outline some of
the most important prospects of prominence plasma diagnostics.
---------------------------------------------------------
Title: Emission of Lyman alpha radiation by solar coronal loops. I -
General synopsis
Authors: Gouttebroze, P.; Vial, J. C.; Tsiropoula, G.
1986A&A...154..154G Altcode:
The processes of emission of Lyman-alpha radiation by loop-like
structures embedded in the solar corona are investigated, for
a large range of physical conditions within these objects. The
coupled set of equations for radiative transfer, and hydrogen atom
level populations, ionization and pressure equilibria is solved
to obtain the emitted L-alpha intensities as functions of pressure,
temperature and size. Three different cases are treated: (1) optically
thin structures with arbitrary geometry. (2) plane-parallel slabs,
either horizontal or vertical, with arbitrary optical depth. (3)
cylindrical loops with horizontal axis, for moderate optical depths
(au is less than 1000). The importance of geometry, as well as that of
partial frequency redistribution and of the hydrogen atom's model, are
evaluated. Empirical formulae and diagrams of intensity as a function
of physical state parameters are given. The diagnostic possibilities of
Lyman-alpha filtergrams alone or in conjunction with other observations,
are discussed.
---------------------------------------------------------
Title: The effect of abundance values on partial redistribution
line computations.
Authors: Ferrero, R. F.; Gouttebroze, P.
1985ASIC..152..125F Altcode: 1985pssl.proc..125F
This paper discusses line formation theory for so-called chromospheric
indicators, in particular the cores of Ca II, Mg II, C II and Si II
resonance lines in the case of A dwarf stars. Some of these lines must
be interpreted as computed partial redistribution (PR) line profiles
and others as complete redistribution (CR) ones. The role of abundances
in this theoretical interpretation is analyzed.
---------------------------------------------------------
Title: Transfer of Lyman-α radiation in solar coronal loops.
Authors: Gouttebroze, P.; Vial, J. -C.; Tsiropoula, G.
1985ASIC..152..359G Altcode: 1985pssl.proc..359G
The emission and scattering of Lyman-α radiation within the loop-like
structures of the solar corona are investigated, for a large range
of physical conditions within these objects. Results from partial
and complete redistribution computations are compared. A series of
predictions, concerning line profiles, integrated intensities, and
directional diagrams are given for observation diagnosis.
---------------------------------------------------------
Title: The Mg II lines in A dwarf stars.
Authors: Freire-Ferrero, R.; Talavera, A.; Gouttebroze, P.
1984ESASP.218..211F Altcode: 1984iue..conf..211F
High resolution IUE spectra, in the spectral region of the Mg II
resonance lines of 16 A stars were obtained. To interpret these
observations, the formation of Mg II lines in an A type stellar
atmosphere for different values of Mg abundance and microturbulence
within the framework of the NLTE theory with complete and partial
redistribution of the Mg II line profiles were studied. Observed
and computed line profiles are compared and abundance values are
established. Theoretical stellar line profiles are used to determine the
interstellar contribution to the observed stellar Mg II line profiles.
---------------------------------------------------------
Title: Intensity oscillations in the calcium - K line
Authors: Gouttebroze, P.; Dame, L.; Malherbe, J. -M.
1984MmSAI..55..245G Altcode:
An analysis is undertaken of a time sequence of quiet sun filtergrams
taken in the core of the K line, in order to investigate the oscillatory
properties of the chromosphere. The physical significance of these
intensity variations and their diagnostic capabilities are discussed,
and an oscillatory power vs. frequency and mean intensity diagram
is noted to indicate the different behaviors of bright regions
dominated by low frequency waves and darker regions dominated by high
frequency waves. A diagnostic wavenumber-frequency diagram indicates
two oscillatory power concentrations which approximately correspond to
acoustic and gravity waves, in chromospheric conditions. A theoretical
diagnostic diagram computed on the basis of a solar atmosphere model
exhibits a 'g-1' chromospheric mode; this corresponds almost exactly
to the location of the observed ridge.
---------------------------------------------------------
Title: Observation and analysis of intensity oscillations in the
solar K-line
Authors: Dame, L.; Gouttebroze, P.; Malherbe, J. -M.
1984A&A...130..331D Altcode:
Chromospheric oscillations are investigated with a time sequence
of filtergrams of the sun taken in the core of the Ca II K-line at
the Sacramento Peak Observatory. The relations between oscillation
frequency and wavenumber are analyzed, as are those between frequency
and mean intensity. Intensity analysis reveals that low frequency waves
are associated mainly with bright (chromospheric network) regions,
while the '3-min' oscillation dominates in cell interiors. As the mean
brightness of the observed region increases, the high frequency limit
of oscillatory power decreases. This is interpreted as the decrease of
the resonance frequency of the chromospheric cavity with increasing
temperatures, which confirms the chromospheric origin of the 3-min
oscillations. Diagnostic diagrams suggest that both acoustic and
internal gravity waves occur in the chromosphere and appear to have
a modal structure.
---------------------------------------------------------
Title: Magnesium II line formation - The contribution of high atomic
levels to the resonance lines
Authors: Lemaire, P.; Gouttebroze, P.
1983A&A...125..241L Altcode:
An evaluation of the solar and stellar atmospheric modeling consequences
of the use of different Mg(+) ion atomic models in line profile
computations has determined that the h and k line cores appear to
be almost insensitive to the number of levels used in the profile
computations. A careful treatment of the blended resonance doublet wings
appears to be necessary, however, for atmospheric diagnostics using
the subordinate 279.1 and 179.9 lines. The cores and near wings of h
and k are strongly sensitive to the atmospheric model, from the higher
part of the photosphere to the upper part of the chromospheric plateau.
---------------------------------------------------------
Title: On the effect of temperature fluctuations on line intensities.
Authors: Gouttebroze, P.
1983JQSRT..30..193G Altcode:
The effects of temperature fluctuations in a stellar atmosphere on the
intensities of the lines emitted by a multilevel atom are investigated
by differentiating the coupled set of radiative transfer and statistical
equilibrium equations. A numerical method is proposed for the fast
computation of large sequences of line profiles when the atmospheric
temperatures are fluctuating about a mean curve T(z) (oscillations,
waves, turbulence, etc.) This method is applied to a three-level atom
simulating the formation of Ca(II) lines in the solar atmosphere and
the results are compared with those of direct computations. It is shown
how the variations of atomic level populations, line source functions,
and emergent intensities may be related to temperature variations by
a sum of several terms corresponding to each atomic transition and
arising from the variations of collisional excitation rates. Finally,
the possibility of extending the method to compute profile variations
when temperatures, densities and velocities are changing simultaneously
within the atmosphere is discussed.
---------------------------------------------------------
Title: The MG II H and K lines in Vega.
Authors: Ferrero, R. F.; Gouttebroze, P.; Kondo, Y.
1983A&A...121...59F Altcode:
High resolution h (2802.7 A) and k (2795.5 A) lines Mg II obtained
for the star Vega (Alpha Lyr, A0V) with Copernicus satellite and a
balloon-borne ultraviolet stellar spectrometer (BUSS) are interpreted by
means of theoretical NLTE line profiles in the frame work of complete
(CR) and partial (PR) redistribution hypothesis. The PR profiles
are remarkably coincident with the observed ones for a magnesium
abundance Mg/H = 0.00001 and a projected rotation velocity v sin i = 17
km/s. LTE and NLTE atmospheric models with a temperature plateau or with
temperature rises (depending on whether the atmosphere is in radiative
equilibrium or not) are used to account for the possible presence of
a chromosphere on Vega. The possible presence of an interstellar Mg
II absorption line superimposed on the stellar ones is also discussed.
---------------------------------------------------------
Title: Space-time Analysis of Oscillations Observed in the Solar Ca
II Resonance Lines
Authors: Dame, L.; Gouttebroze, P.
1982BAAS...14..922D Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Solar atmospheric dynamics. II - Nonlinear models of the
photospheric and chromospheric oscillations
Authors: Leibacher, J.; Gouttebroze, P.; Stein, R. F.
1982ApJ...258..393L Altcode:
The one-dimensional, nonlinear dynamics of the solar atmosphere is
investigated, and models of the observed photospheric (300 s) and
chromospheric (200 s) oscillations are described. These are resonances
of acoustic wave cavities formed by the variation of the temperature
and ionization between the subphotospheric, hydrogen convection zone
and the chromosphere-corona transition region. The dependence of
the oscillations upon the excitation and boundary conditions leads
to the conclusion that for the observed amplitudes, the modes are
independently excited and, as trapped modes, transport little if any
mechanical flux. In the upper photosphere and lower chromosphere,
where the two modes have comparable energy density, interference
between them leads to apparent vertical phase delays which might be
interpreted as evidence of an energy flux.
---------------------------------------------------------
Title: Physical properties of the solar chromosphere deduced from
optically thick lines. I - Observations, data reduction, and modelling
of an average plage
Authors: Lemaire, P.; Gouttebroze, P.; Vial, J. C.; Artzner, G. E.
1981A&A...103..160L Altcode:
Simultaneous Ca II H and K, Mg II h and k, and H I Lyman-alpha and
Lyman-beta profiles have been recorded by the OSO-8/LPSP spectrometer on
a quiet sun area and a part of plage, McMath 13738. After data reduction
and filtering, a full set of calibrated profiles is obtained. Using
a code developed at LPSP (Gouttebroze et al., 1978), profiles
computed from VAL III model C (Vernazza et al., 1981) are compared
to observations. A specific plage model has been computed to fit the
observed profiles. This model reproduces successfully Ca II H and K,
and H I Lyman-alpha and Lyman-beta, but partly fails with Mg II h and
k. Atmospheric inhomogeneities and dynamical effects may contribute to
this discrepancy, and it is proposed that the level number entering
in the Mg II computation be increased to take account of a likely
fluorescence induced by the H I Lyman-beta radiation field.
---------------------------------------------------------
Title: Solar H I LY alpha far wing measurement
Authors: Jouchoux, A.; Vial, J. C.; Artzner, G. E.; Gouttebroze, P.;
Lemaire, P.
1981A&A....93..415J Altcode:
High spectral resolution photoelectric observations of the solar H I
Ly alpha far wing are presented. Measurements above active regions and
quiet sun center are compared to photographic observations of Basri
et al. (1979).
---------------------------------------------------------
Title: On VI (λ = 1032 Å) profiles in and above an active region
prominence, compared to quiet Sun center and limb profiles
Authors: Vial, J. C.; Lemaire, P.; Artzner, G.; Gouttebroze, P.
1980SoPh...68..187V Altcode:
O VI (λ = 1032 Å) profiles have been measured in and above a filament
at the limb, previously analyzed in H I, Mg II, Ca II resonance lines
(Vial et al., 1979). They are compared to profiles measured at the
quiet Sun center and at the quiet Sun limb.
---------------------------------------------------------
Title: Solar atmospheric dynamics. I - Formation of optically thick
chromospheric lines
Authors: Gouttebroze, P.; Leibacher, J. W.
1980ApJ...238.1134G Altcode:
Two of the most representative chromospheric lines, Mg II k and Ca
II K are used to study the formation of optically thick lines in a
time-dependent, one-dimensional model of the solar atmosphere. Time
sequences of these line profiles are calculated for two kinds of
atmospheric motions: propagation of a pulse through the atmosphere,
and free oscillations. The mechanisms of formation (especially
the displacement of the emitting layers) are studied for different
parts of the profiles. Finally, the deformations of the profiles
are analyzed using methods also suitable for observations, and the
resulting parameters are compared to physical variables in order to
evaluate the diagnostic methods.
---------------------------------------------------------
Title: Some Effects of Strong Acoustic Waves on Strong Spectral Lines
Authors: Gouttebroze, P.; Leibacher, J.
1980LNP...114..212G Altcode: 1980IAUCo..51..212G; 1980sttu.coll..212G
No abstract at ADS
---------------------------------------------------------
Title: Profiles of H I (Lalpha ), Mg II (h and k), Ca II (H and K)
lines of an active filament at the limb, with the LPSP instrument
aboard the OSO-8 satellite.
Authors: Vial, J. C.; Gouttebroze, P.; Artzner, G.; Lemaire, P.
1979SoPh...61...39V Altcode:
We scanned the H I Lα, Mg II h and k, Ca II K and H lines
simultaneously with the LPSP instrument on OSO-8, to investigate the low
and moderate temperature regions of an `active region filament'. The
Lα line is not reversed except for the innermost position in the
prominence. Intensity (k/h), (K/H) ratios are respectively 2 and 1.1,
indicating that the Mg II lines are optically thin, and that Ca II
K is saturated, although not clearly reversed. The results obtained
during the second sequence of observations (K saturated before Lα
for example) indicate that within the size of the slit (1″ × 10″)
we are not observing the same emitting features in the different lines.
---------------------------------------------------------
Title: LY α and β of hi, H and K of MG ii, H and K of CA II Profiles
of a Quiescent Prominence Obtained with the LPSP Instrument of OSO-8.
Authors: Vial, J. C.; Lemaire, P.; Gouttebroze, P.
1979phsp.coll...52V Altcode: 1979IAUCo..44...52V
No abstract at ADS
---------------------------------------------------------
Title: Profiles of H i (Lyα), MG II (h and K), CA II (h and k)
Lines in an Active Filament at the Limb, Observed with the LPSP
Instrument Onboard the OSO-8 Satellite.
Authors: Vial, J. C.; Gouttebroze, P.; Artzner, G.; Lemaire, P.
1979phsp.coll..250V Altcode: 1979IAUCo..44..250V
No abstract at ADS
---------------------------------------------------------
Title: The solar hydrogen Lyman-beta and Lyman-alpha lines: disk
center observations from OSO 8 compared with theoretical profiles.
Authors: Gouttebroze, P.; Lemaire, P.; Vial, J. C.; Artzner, G.
1978ApJ...225..655G Altcode:
The solar La and Lfl lines of hydrogen have been measured at the center
of the disk with the LPSP spectrometer aboard OSO 8. These line profiles
are compared with theoretical profiles obtained with different solar
atmospheric models, assuming either complete or partial frequency
redistribution in scattering. The assumption of microturbulence for
the velocity fields appears insufficient to account for the profiles
of the line cores; better results are obtained with a blend of micro-
and macroturbulence, which shows the need of a generalized treatment of
the turbulent motions in the formation of these lines. If the effects
of partial redistribution are taken into account, a good fit of the
line wings requires higher temperatures, in the region under the
plateau, than in the reference atmospheric model of Vernazza, Avrett,
and Loeser. Subject headings: line formation - line profiles - Sun:
chromosphere - Sun: spectra - ultraviolet: spectra
---------------------------------------------------------
Title: A Dynamical Representation of the Solar Chromosphere
Authors: Leibacher, J. W.; Gouttebroze, P.
1978BAAS...10..671L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Simultaneous time-resolved observations of the H Lalpha ,
Mg k 2795 Å, and Ca K solar lines.
Authors: Artzner, G.; Leibacher, J.; Vial, J. C.; Lemaire, P.;
Gouttebroze, P.
1978ApJ...224L..83A Altcode:
No abstract at ADS
---------------------------------------------------------
Title: The LPSP instrument on OSO 8. II. In-flight performance and
preliminary results.
Authors: Bonnet, R. M.; Lemaire, P.; Vial, J. C.; Artzner, G.;
Gouttebroze, P.; Jouchoux, A.; Leibacher, J. W.; Skumanich, A.;
Vidal-Madjar, A.
1978ApJ...221.1032B Altcode:
The paper describes the in-flight performance for the first 18 months of
operation of the LPSP (Laboratoire de Physique Stellaire et Planetaire)
instrument incorporated in the OSO 8 launched June 1975. By means of
the instrument, an absolute pointing accuracy of nearly one second
was achieved in orbit during real-time operations. The instrument
uses a Cassegrain telescope and a spectrometer simultaneously
observing six wavelengths. In-flight performance is discussed with
attention to angular resolution, spectral resolution, dispersion
and grating mechanism (spectral scanner) stability, scattered light
background and dark current, photometric standardization, and absolute
calibration. Real-time operation and problems are considered with
reference to pointing system problems, target acquisition, and L-alpha
modulation. Preliminary results involving the observational program,
quiet sun and chromospheric studies, quiet chromospheric oscillation
and transients, sunspots and active regions, prominences, and aeronomy
investigations are reported.
---------------------------------------------------------
Title: Doppler Shifts measured in 0 VI line from OSO-B observations
above and in the vicinity of plage Mc Math 13738.
Authors: Lemaire, P.; Skumanich, A.; Artzner, G.; Gouttebroze, P.;
Vial, J. C.; Bonnet, R. M.; McWhirter, P.
1978BAAS...10Q.440L Altcode:
No abstract at ADS
---------------------------------------------------------
Title: OSO-8 Radio and X-ray observations of the 19 April 1977 flare.
Authors: Skumanich, A.; Jouchoux, A.; Castelli, J.; Lemaire, P.;
Artzner, G.; Gouttebroze, P.; Vial, J. C.; Bonnet, R. M.
1978BAAS...10..441S Altcode:
No abstract at ADS
---------------------------------------------------------
Title: Velocity gradients in the solar chromosphere and Mg II line
profiles.
Authors: Gouttebroze, P.
1977A&A....54..203G Altcode:
Summary The resonance lines of Mg ii, when observed with angular
resolution on the sun, exhibit dissymmetries varying from place
to place. We report here the results of some computations of these
line profiles in a solar- type atmosphere with differential motions,
and discuss different assumptions on the model atmosphere and the
treatment of the scattering process. We deduce from these computations
the relations between velocity gradients and dissymmetries corresponding
to the different assumptions and apply them to a sample of observed
profiles. Key words: solar chromosphere radiative transfer velocity
fields
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Title: A center-to-limb analysis of solar Mg II lines.
Authors: Gouttebroze, P.; Lemaire, P.
1974A&A....34..375G Altcode:
Center-to-limb variations of Mg II resonance line profiles, deduced
from balloon spectra of the sun, are studied. Limb-darkening in the line
wings agrees satisfactorily with frequency-indpendent source functions
and Voigt profiles for line absorption coefficients. Estimates of
Doppler widths from a line core analysis show a rapid increase of
turbulence velocities with height. The source functions of the two
lines are found to be unequal at the same geometrical depth, which
suggests that collisional coupling between fine-structure levels (3p)
is weak. Apparent source function variations with frequency are found
in the spectral interval from 0.2 to 0.5 A from line center. Several
possible explanations of this fact (partially conherent scattering,
geometrical and dynamical effects) are discussed.
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Title: Analyse de l'effet centre-bord observé dans les raies de Mg
II solaires
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Title: Analyse de l'effet centre-bord observé dans les
raies de Mg II solaires
Authors: Gouttebroze, Pierre Marcel Alain
1973PhDT.......100G Altcode:
No abstract at ADS
