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ONDES ET INSTABILITÉS BASSE-FRÉQUENCE DANS UN PLASMA GYROTROPE. APPLICATION À L'INSTABILITÉ D'INTERCHANGE DANS LES MAGNÉTOSPHERES DES PLANETES GÉANTES

Abstract : Fast rotating magnetospheres like those of Jupiter and Saturn contain numerous plasma sources deeply embedded within the magnetospheric system. The plasma created locally in the vicinity of these sources is observed in all regions of the magnetosphere, these observations implying the necessity of a radial transport throughout the system. The present thesis deals with the theoretical investigation of a mecanism responsible for this transport, the interchange instability, a Rayleigh-Taylor type instability in which the centrifugal force plays the role of gravity.
In order to take into account the physical nature of magnetospheric plasmas, collisionless, an exact linear formalism to study waves and instabilities in gyrotropic plasmas has been developped. This formalism enables us to consider both non-electromagnetic forces (gravitationnal, centrifugal and Coriolis forces), the stratification of the medium (gradients and curvature) and to include some kinetic effects (Landau resonance).
In a first step, this formalism is validated in the case of homogeneous plasmas, before to be applied to stratified plasmas. The quasi-interchange modes, the modes for which stratification and rotation have a significant impact, are identified in terms of Alfvén, slow and mirror modes, according to the classical terminology prevalent in homogeneous plasmas. The instability criteria of the different quasi-interchange modes are obtained analytically and tested in the case of the multi-species plasma torus of the jovian satellite Io by using the most recent available data sets describing this environment.
Deferring future applications to the spatial environment of Saturn for the arrival of the Cassini spacecraft at the planet, its Jupiter flyby in December 2000 - Janvier 2001 is briefly presented. The analysis of the magnetometer data obtained during this flyby identifies signatures of the mirror mode in the distant jovian magnetosheath, this mode having been previously identified in our theoretical formalism.
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https://tel.archives-ouvertes.fr/tel-00010486
Contributor : Nicolas André <>
Submitted on : Friday, October 7, 2005 - 7:35:18 PM
Last modification on : Thursday, October 15, 2020 - 4:07:23 AM
Long-term archiving on: : Friday, April 2, 2010 - 10:41:44 PM

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  • HAL Id : tel-00010486, version 1

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Nicolas André. ONDES ET INSTABILITÉS BASSE-FRÉQUENCE DANS UN PLASMA GYROTROPE. APPLICATION À L'INSTABILITÉ D'INTERCHANGE DANS LES MAGNÉTOSPHERES DES PLANETES GÉANTES. Astrophysique [astro-ph]. Université Paul Sabatier - Toulouse III, 2003. Français. ⟨tel-00010486⟩

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