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Excitation stochastique des oscillations stellaires.
Application à la mission spatiale COROT.

Abstract : The observed solar p-mode oscillations are damped due to several damping mechanisms and in the other hand they are believed to be excited stochastically by turbulent convection.
Turbulent motions, which occur in the convection zone, generate acoustic power which in turn is injected into the p-mode oscillations and thus ensures the modes excitation. Solar-like oscillations are therefore meant as stochastically excited oscillations and concern low massive stars with an outer convective zone.
Providing that accurate measurements of the oscillation amplitudes and
damping rates are available it is possible to evaluate the power
injected into the modes and thus- by comparison
with the observations- to constrain current theories.
In the present work we review the basic theory : inconsistencies are identified and removed and controversy between previous authors are solved. As a result I propose a new formulation which generalizes previous ones. This formulation enable investigations of various possible stellar turbulent models. The entropy contribution to excitation is found to originate from the advection of the Eulerian entropy fluctuations by the turbulent velocity field and dominates the contribution of the Reynolds stress.
Numerical computations performed in the solar case and in the case of Procyon reveal the sensitivity to the free parameters - involved in the theory- and to the model of stellar turbulence. Application to several low intermediate stars (1 Mo < M < 2 Mo) located in the main-sequence shows that hotter stars are more sensitive to the turbulent features and thus can yield more information.
The forthcoming space mission COROT will provide high-quality data of solar oscillations. In order to optimize the scientific return of the mission we have developed a numerical simulation of the whole photometric chain. This simulation allows use to assess the instrument response which has been convoluted with the oscillations power. We conclude that the high performances of COROT will provide accurate constraints for the theory of the stochastic excitation developed in the present work.
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https://tel.archives-ouvertes.fr/tel-00067734
Contributor : Réza Samadi <>
Submitted on : Friday, August 15, 2008 - 3:22:41 PM
Last modification on : Monday, December 14, 2020 - 9:45:51 AM
Long-term archiving on: : Tuesday, September 21, 2010 - 5:39:32 PM

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  • HAL Id : tel-00067734, version 2

Citation

Réza Samadi. Excitation stochastique des oscillations stellaires.
Application à la mission spatiale COROT.. Astrophysique [astro-ph]. Université Pierre et Marie Curie - Paris VI, 2000. Français. ⟨tel-00067734v2⟩

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