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Modélisation des Champs Magnétiques de Grandes Echelles dans les Intérieurs Stellaires Application aux étoiles de type solaire et aux étoiles Ap

Abstract : Stellar astrophysics needs today new models of large-scale magnetic fields, which are observed through spectropolarimetry at the surface of Ap/Bp stars, and thought to be an explanation for the uniform rotation of the solar radiation zone, deduced from helioseismic inversions. During my PhD, I focused on describing the possible magnetic equilibria in stellar interiors. The found configurations are mixed poloidal-toroidal, and minimize the energy for a given helicity, in analogy with Taylor states encountered in spheromaks. Taking into account the self-gravity leads us to the “non force-free” equilibria family, that will thus influence the stellar structure. I derived all the physical quantities associated with the magnetic field ; then I evaluated the perturbations they induce on gravity, thermodynamic quantities as well as energetic ones, for a solar model and an Ap star. 3D MHD simulations allowed me to show that these equilibria form a first stable states family, the generalization of such states remaining an open question. It has been shown that a large-scale magnetic field confined in the solar radiation zone can induce an oblateness comparable to a high core rotation law. I also studied the secular interaction between the magnetic field, the differential rotation and the meridional circulation in the aim of implementing their effects in a next generation stellar evolution code. The influence of the magnetism on convection has also been studied. Finally, hydrodynamic processes responsible for the mixing have been compared with diffusion and a change of convection's efficiency in the case of a CoRoT star target.
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https://pastel.archives-ouvertes.fr/tel-00498360
Contributor : Vincent Duez <>
Submitted on : Wednesday, July 7, 2010 - 12:11:16 PM
Last modification on : Monday, February 10, 2020 - 6:13:09 PM
Long-term archiving on: : Tuesday, October 23, 2012 - 10:05:45 AM

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  • HAL Id : tel-00498360, version 1

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Vincent Duez. Modélisation des Champs Magnétiques de Grandes Echelles dans les Intérieurs Stellaires Application aux étoiles de type solaire et aux étoiles Ap. Astrophysique [astro-ph]. Ecole Polytechnique X, 2009. Français. ⟨tel-00498360⟩

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