Author name code: gouttebroze ADS astronomy entries on 2022-09-14 author:"Gouttebroze, Pierre" ------------------------------------------------------------------------ Title: PROM7: 1D modeler of solar filaments or prominences Authors: Gouttebroze, P. Bibcode: 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). Title: PROM4: 1D isothermal and isobaric modeler for solar prominences Authors: Gouttebroze, P.; Labrosse, N. Bibcode: 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.

PROM7 (ascl:1805.023) is a more recent version of this code. Title: Radiative transfer in cylindrical threads with incident radiation. VI. A hydrogen plus helium system Authors: Gouttebroze, P.; Labrosse, N. Bibcode: 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.
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.
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.
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.
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. Title: Formation of Helium Lines in Solar Prominences Authors: Labrosse, Nicolas; Gouttebroze, Pierre Bibcode: 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. Title: Helioseismic Spectral Diagnostics - An Update Authors: Leibacher, John W.; Baudin, F.; Belkacem, K.; Dupret, M.; Goupil, M.; Gouttebroze, P.; Samadi, R. Bibcode: 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 Title: Diagnostics of active and eruptive prominences through hydrogen and helium lines modelling Authors: Labrosse, N.; Vial, J. -C.; Gouttebroze, P. Bibcode: 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. Title: Radiative transfer in cylindrical threads with incident radiation. V. 2D transfer with 3D velocity fields Authors: Gouttebroze, P. Bibcode: 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.
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.
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.
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.
Conclusions: This is a new step in the diagnostic of physical conditions in coronal loops, allowing the study of dynamical phenomena. Title: The Quiet Sun Network at Subarcsecond Resolution: VAULT Observations and Radiative Transfer Modeling of Cool Loops Authors: Patsourakos, S.; Gouttebroze, P.; Vourlidas, A. Bibcode: 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<105 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. Title: Spectral Diagnostics of Active Prominences Authors: Labrosse, N.; Gouttebroze, P.; Vial, J. -C. Bibcode: 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. Title: Radiative transfer in cylindrical threads with incident radiation. IV. Time-dependent and thermal equilibrium models Authors: Gouttebroze, P. Bibcode: 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.
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.
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.
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.
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. Title: Effect of motions in prominences on the helium resonance lines in the extreme ultraviolet Authors: Labrosse, N.; Gouttebroze, P.; Vial, J. -C. Bibcode: 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.
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.
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.
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.
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.

Figures [see full text], [see full text] and [see full text] are only available in electronic form at http://www.aanda.org Title: The Helium Spectrum in Erupting Solar Prominences Authors: Labrosse, N.; Vial, J. C.; Gouttebroze, P. Bibcode: 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. Title: The Helium Spectrum in Moving Solar Prominences Authors: Labrosse, N.; Gouttebroze, P.; Vial, J. -C. Bibcode: 2006ESASP.617E.134L Altcode: 2006soho...17E.134L No abstract at ADS Title: Plasma diagnostic of a solar prominence from hydrogen and helium resonance lines Authors: Labrosse, N.; Vial, J. -C.; Gouttebroze, P. Bibcode: 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-2. The Lyβ line is formed in a higher temperature region (more than 11,000 K). Title: Radiative transfer in cylindrical threads with incident radiation. III. Hydrogen spectrum Authors: Gouttebroze, P. Bibcode: 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. Title: Transfer in cylindrical fluxtubes, with 1 or 2 dimensions Authors: Gouttebroze, P. Bibcode: 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. Title: Radiative transfer in cylindrical threads with incident radiation. II. 2D azimuth-dependent case Authors: Gouttebroze, P. Bibcode: 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. 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. Bibcode: 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. Title: Non-LTE Radiative Transfer in Model Prominences. I. Integrated Intensities of He I Triplet Lines Authors: Labrosse, N.; Gouttebroze, P. Bibcode: 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. 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. Bibcode: 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.

Appendix A is only available in electronic form at http://www.edpsciences.org Title: Radiative transfer in cylindrical threads with incident radiation Authors: Gouttebroze, P. Bibcode: 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. 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. Bibcode: 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. 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. Bibcode: 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 6×103K 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. Title: Prediction of line intensity ratios in solar prominences Authors: Gouttebroze, P.; Labrosse, N.; Heinzel, P.; Vial, J. -C. Bibcode: 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. Title: Calcium to hydrogen line ratios in solar prominences Authors: Gouttebroze, P.; Heinzel, P. Bibcode: 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-2, 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-2), 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-2. 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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 Bibcode: 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 Bibcode: 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. Bibcode: 1989HvaOB..13..347V Altcode: No abstract at ADS Title: Radiative Transfer in Cylindrical Prominence Threads Authors: Gouttebroze, P. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1987JAF....29...15F Altcode: No abstract at ADS Title: Non-Lte Modelling of Prominences Authors: Heinzel, P.; Gouttebroze, P.; Vial, J. C. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1986A&A...160..195G Altcode: Approximations are proposed for the computation of the RII-A 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 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. Bibcode: 1978BAAS...10..441S Altcode: No abstract at ADS Title: Velocity gradients in the solar chromosphere and Mg II line profiles. Authors: Gouttebroze, P. Bibcode: 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 Title: A center-to-limb analysis of solar Mg II lines. Authors: Gouttebroze, P.; Lemaire, P. Bibcode: 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. Title: Analyse de l'effet centre-bord observé dans les raies de Mg II solaires Title: Analyse de l'effet centre-bord observé dans les raies de Mg II solaires Authors: Gouttebroze, Pierre Marcel Alain Bibcode: 1973PhDT.......100G Altcode: No abstract at ADS