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La couronne neutre suprathermique de Mars :
Modélisation et étude d'une instrumentation pour sa mesure In Situ

Abstract : The martian exosphere is the very depleted part of the martian atmosphere above roughly 200km in altitude. As a boundary medium between the solar wind and the upper atmosphere, it is crucial to the loss of material from the planet. The present work concerns a modelling study of the hot exospheric particles, first, and second, an experimental and modelling study of an instrument useful to their characterization. The exospheric particles are created through dissociative recombination reaction of O2+ and CO+ ions, and through sputtering of the atmosphere by O+ pick-up ions. Their creation and ballistical transport occur in a spherically symetrical amtosphere, modelled by using a test-particule Monte Carlo approach. Coupled to this approach a Molecular Dynamic model is used to describe collisions and molecular dissociations. The simulation results offer an insight into the coronnal structure (densities and energy distributions) involving hot heavy species as CO2 and CO, and allow to derive specifications for a mass spectrometer dedicated to their in situ measurement. To this aim, new high brightness (electron impact) ion sources are required. In the second part of this work, the electrons emitted by cold cathodes based on either molybdenum microtips or carbon nanotubes are characterized by using a hemispherical retarding potential energy analyzer. The measured parameters of the electron sources are then used to derive the required ion source sensitivity. A first numerical model of the ion source and energy analysis part of the mass spectrometer is also presented.
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https://tel.archives-ouvertes.fr/tel-00141140
Contributor : Fabrice Cipriani <>
Submitted on : Tuesday, May 1, 2007 - 3:22:30 PM
Last modification on : Monday, October 19, 2020 - 10:53:28 AM
Long-term archiving on: : Tuesday, September 21, 2010 - 1:05:57 PM

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  • HAL Id : tel-00141140, version 2

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Citation

Fabrice Cipriani. La couronne neutre suprathermique de Mars :
Modélisation et étude d'une instrumentation pour sa mesure In Situ. Astrophysique [astro-ph]. Université de Versailles-Saint Quentin en Yvelines, 2006. Français. ⟨tel-00141140v2⟩

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