Author name code: souffrin ADS astronomy entries on 2022-09-14 author:Souffrin, Pierre ------------------------------------------------------------------------ Title: On the theory of shock-heated atmospheres. III - Discussion of the formalism and application to stellar coronae Authors: Souffrin, P. Bibcode: 1982A&A...109..205S Altcode: Thermally sustained coronas and stellar winds are investigated using a two-zone corona model describing a lower zone at constant pressure in which the mechanical dissipation and wind effects are neglected, and an upper zone characterized by an extended isothermal region. The interface between the two zones is treated as a dissipative layer of neglectable vertical extent, so that jumps of the physical quantities are consistently fixed by the conservation equations. The physical meaning of transition zone and coronal temperature is discussed, and the lower zone, shock formalism, and dissipation layer are analyzed, as are the upper bounds for the coronal temperature, base pressure, and mechanical flux. A detailed study of the model's special loss function is presented, including the minimum shock strength, conduction dominated case, pressure-mechanical flux relation, and base-temperature relation. Title: On the theory of thermally sustained stellar winds Authors: Souffrin, P. Bibcode: 1982A&A...106...14S Altcode: A reconsideration of the influence of boundary layer structure on a stellar wind is presented, in which Couturier et al's (1979) discussion of the role of the conductive flux boundary layer is extended to include the role of the temperature boundary layer. It is shown that the constraint between the wind parameters is insensitive to the temperature at the lower level, so that the structure of the wind, including the transition zone, is dependent on the mechanical flux entering the transition zone only. Although the structure of the wind is determined by the heating mechanism, the conclusion given is independent of mechanism. Title: Stellar mass flux and coronal heating by shock waves Authors: Couturier, P.; Mangeney, A.; Souffrin, P. Bibcode: 1980IAUS...91..127C Altcode: A self-consistent oversimplified model is proposed which maintains the global balance of energy sources and sinks from the chromospheric level to the interplanetary medium. The heating mechanism chosen is the shock wave dissipation. The model includes self-consistently the different couplings between convective energy flux, conductive flux, radiation losses in optically thin atmospheres, shock wave pressure, and dissipation terms. The input parameters are the base pressure, the base temperature, and the mechanical flux introduced at the chromospheric level in the form of shock waves. For one set of input parameters, some characteristic quantities are presented for four levels: the chromospheric level, the temperature maximum, the critical point, and the earth orbit. Title: On the two-parameter models for stellar coronae. Authors: Mangeney, A.; Souffrin, P. Bibcode: 1979A&A....78...36M Altcode: The two-parameter model developed by Hearn (1975) is reconsidered. A constraint required within the framework of such models is found which is not consistent, in general, with the minimum-flux condition conjectured by Hearn and which provides an alternative reduction of the models to one parameter. The corresponding relations are given explicitly for the special case of heating by weak shock waves when heat conduction back to the chromosphere dominates the energy losses by the corona. Title: On the theory of shock-heated atmospheres. II. The influence of the chromospheric boundary layer structure on the solar wind. Authors: Couturier, P.; Mangeney, A.; Souffrin, P. Bibcode: 1979A&A....74....9C Altcode: Summary. We show that the complex boundary-layer structure of the solar upper chromosphere discussed in a previous paper implies a new constraint between the parameters of the coronal plasma flow. In the simple model of a one fluid symmetric solar wind with the mechanical heating due to acoustic wave dissipation, it results that the mechanical energy generated in the waves determines both the mass flux in the solar wind and the gas pressure in the inner transition zone. Key words: heating mechanisms - stellar winds Title: The sun, a variable star. Authors: Fossat, E.; Souffrin, P. Bibcode: 1978Rech....9..526F Altcode: The paper describes supergranules in the solar surface and a local oscillation with a 5-minute frequency in the solar atmosphere. The supergranules can be approximately 30 times the size of the granules and are more stable than the granules, the supergranules persisting more than 10 hours, that is, more than 100 times the lifetime of a granule. While the existence of two systems - granules and supergranules - can not yet be explained by convection theory, the horizontal movements in the supergranules do explain the reticular structure of the solar magnetic field, as the movement from the center to the edge of the supergranule drags the magnetic field to the border. The local oscillations extend a distance of a few thousand meters and persist approximately 20 minutes. The implications of supergranules and local oscillation for an understanding of the external layers of stars are discussed. Title: On the theory of shock-heated atmospheres. I. A methodological discussion with special reference to the solar case. Authors: Gonczi, G.; Mangeney, A.; Souffrin, P. Bibcode: 1977A&A....54..689G Altcode: The paper reconsiders the physics and the mathematical formulation of the theory of shock-heated atmospheres. A complex boundary-layer structure is found which accounts for the gross features of the vertical stratification of the solar chromosphere. The existence of two different regimes for shock propagation is discussed, and the formalism is extended to include both regimes and the transition from one to the other. The validity of the description of the dynamics is shown to be restricted to small shock strength. Although high velocities are shown to be necessary in the low chromosphere, they are confined in a dynamical boundary layer, so that the formalism described is relevant for the study of the outer layers of the sun. Title: Sur la dynamique de l'atmosphère solaire. Authors: Souffrin, P. Bibcode: 1977rese.proc...95S Altcode: No abstract at ADS Title: On the mechanical heating of the external layers of the sun - A methodological discussion Authors: Souffrin, P. Bibcode: 1976MmSAI..47..365S Altcode: Theoretical treatments of the mechanical heating of the external layers of stars are reviewed; the problem is posed as one of stationary nonhomogeneous turbulence (that is, the Rayleigh-Benard problem) with the essential difficulty lying in the solution of a hierarchy of equations of motion, mass and energy through a chosen closure hypothesis. In particular, the closure relation proposed by Schwarzschild (1948), which makes reference to acoustic waves, and the closure hypothesis of Schatzman (1949), a more general treatment based on linear acoustics, are analyzed. It is suggested that a description of the propagation of an isolated unsustained shock in a homogeneous compressible fluid at rest, developed by Brinkley and Kirkwood (1947), may be quite effectively applied to the problem of the heating of the solar atmosphere. Title: Introduction à la 'instabilities Hydrodynamiques a L'origine des Mouvements dans les Atmospheres Stellaires' Authors: Souffrin, P. Bibcode: 1976pmas.conf...17S Altcode: No abstract at ADS Title: Ray Trapping in Stellar Envelopes, Pulsational Instabilities and Heating of External Layers Authors: Souffrin, P. Bibcode: 1974IAUS...56..293S Altcode: No abstract at ADS Title: Sur la Dynamique de l'Atmosphère Solaire Authors: Souffrin, P. Bibcode: 1973JPhys..34....2S Altcode: No abstract at ADS Title: Note on the Growth Rate of Convective Modes in a Self Gravitating Gas Sphere Authors: Grisvard, P.; Souffrin, P.; Zerner, M. Bibcode: 1972A&A....17..309G Altcode: It is shown that within Cowling's approximation the growth rate of the eigen modes in a convectively unstable self gravitating gas sphere is a bounded monotonically increasing function of the degree of the harmonic. Key words: convection - stellar structure. Title: Radiative Relaxation of Sound Waves in an Optically Thin Isothermal Atmosphere Authors: Souffrin, P. Bibcode: 1972A&A....17..458S Altcode: The radiative damping of oscillatory modes in an optically thin isothermal atmosphere is investigated within the approximation of Newton's law of cooling (Sections I-Il). Special attention is paid to vertical modes sustained by harmonic boundary conditions (III) and to the discussion of the validity of the adiabatic and isothermal limiting cases. The influence of relaxation on the response of an infinite model to an applied body-force is studied in the one-dimensional case (W). Application to the solar conditions indicates that the dissipation in the chromosphere has little effect on the dynamics of the chromospheric oscillation (V). Key words: stellar atmospheres - the sun Title: Convection Authors: Souffrin, P. Bibcode: 1971tdas.conf..238S Altcode: 1971SAAS....1..238S Introduction Basic Equations Thermal Instabilities of a Homogeneous Compressible Fluid Pressure-modes and entropy-mode Stability of the compressible homogeneous fluid when heat exchange - is taken into account Dynamics of a Stratified Compressible Atmosphere The local dispersion relation The condition for dynamic instability The stable case. Pressure and gravity modes The unstable case. Pressure modes and convective modes The "parcel method". Phenomenological discussion of dynamical - stability Thermal, Pulsational and Convective Instabilities, and the "Parcel - Approximation" of the Equations of Hydrodynamics The "parcel" model and the equations of hydrogynamics Convection and thermal instability Convection and dynamical instability A general phenomenological discussion of the relation between - convection and pulsational instability Mixing - Length Theory Convection and the structure of a star The mixing-length formalism A discussion of the mixing-length theory A Study of the Non-Radial Motions of a Self-Gravitating Gas Sphere - within Cowling's Approximation Initial values problem and boundary conditions Sufficient condition for stability The growth rates of unstable modes The oscillation properties of the unstable modes Title: Convection. Authors: Souffrin, P. Bibcode: 1971tsa..conf..238S Altcode: No abstract at ADS Title: Theorie des atmospheres stellaires Authors: Mihalas, D.; Pagel, B.; Souffrin, P. Bibcode: 1971tdas.conf.....M Altcode: 1971QB809.M52......; 1971tsat.book.....M; 1971SAAS....1.....M No abstract at ADS Title: Hydrodynamics of an Atmosphere Excited by an Underlying Turbulent Convective Zone. II. Response of an Atmosphere to an Applied Random Body-Force Authors: Souffrin, P. Bibcode: 1970A&A.....7..227S Altcode: The response of atmospheres to stationary random applied forces homogeneous over horizontal planes is formulated in a very general way (Part I and II). We discuss the occurrence of divergences at cut-off frequencies on the special case of an isothermal atmosphere. The analysis applies without modifications to a large class of models characterized by a propagation operator whose Green's function is singular when the group velocity vanishes. We ultimately relate these divergences to the lack of reflections in the medel and we show that the common energy argument is inadequate (Part II and III). Our view is supported by a detailed analysis of the response of two models: the semi-infinite isothermal atmosphere bounded by a rigid bottom (Part IV), and an infinite model with reflections at one level (Part V). The response is discussed in terms of the spatial extention and coherence of the momentum sources. It is shown that the response to a white-noise force can be enhanced at frequencies different from the local cut-off frequency of the region where the force acts. A prelinary discussion of the implications of this result to the situation prevailing in the solar upper layers strongly suggest the relevance of this study to the interpretation of the photospheric oscillation. (Part VI) Title: Book Review: The Solar Granulation. R. J. BRAY and R. E. LOUGHHEAD: Chapman and Hall, London; Barnes and Noble, New York, 1967. xiv + 150. 60s Authors: Souffrin, P. Bibcode: 1968P&SS...16..144S Altcode: No abstract at ADS Title: An overstability of gravity waves Authors: Souffrin, P.; Spiegel, E. A. Bibcode: 1967AnAp...30..985S Altcode: No abstract at ADS Title: Waves in the Solar Atmosphere Authors: Schatzman, E.; Souffrin, P. Bibcode: 1967ARA&A...5...67S Altcode: No abstract at ADS Title: Hydrodynamique d'une atmosphère perturbée par une zone convective turbulente sous-jacente Authors: Souffrin, P. Bibcode: 1966AnAp...29...55S Altcode: No abstract at ADS Title: Réponse d'une Atmosphère Excitée par une Source Acoustique Etendue Stationnaire. Application à l'Atmosphère Solaire Authors: Souffrin, P. Bibcode: 1965CRASB.260.2135S Altcode: No abstract at ADS Title: Réponse d'une Atmosphère Excitée par une Source Acoustique Etendue Stationnaire Authors: Souffrin, P. Bibcode: 1964CRASB.259.2355S Altcode: No abstract at ADS Title: Remarques sur les mouvements transitoires des systèmes instables. Application à un modèle de granulation solaire Authors: Souffrin, P. Bibcode: 1963AnAp...26..170S Altcode: No abstract at ADS