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Theses

Etude des émissions gazeuses UV/X et des phénomènes d'échange de charge dans l'Héliosphère : application à des systèmes astrophysiques analogues.

Abstract : Charge-exchange is a very efficient phenomenon whenever an ionized gas interacts with a neutral gas. My thesis included a thorough analysis of the occurence of this phenomenon and its effects in the heliosphere and other astrophysical systems.

At first, I used interstellar (IS) H distributions in order to model the backscattered Lyman-α emission observed with the SOHO/SWANinstrument and finally constrain the IS hydrogen parameters. This study allowed to demonstrate the deflection of the IS hydrogen flow with respect to the IS helium flow. This deflection is due to the coupling of IS hydrogen atoms to IS protons in the heliospheric interface and the creation of a secondary population of hydrogen, which is heated, decelerated and deviated with respect to primary IS atoms. The deflection of this secondary population with respect to the primary flow is the direct proof that the structure of the heliosphere is not axisymetric, but tilted under the pressure of an inclined local IS magnetic field.

In a second part, I modeled the EUV and soft X-ray emissions in the heliosphere due to charge-exchange between heavy solar wind ions and IS hydrogen and helium. I have built the first time-dependent model of heliospheric X-ray emission in response to solar wind composition and flux temporal variations, taking into account the solar rotation and the solar wind radial propagation. I applied the model to X-ray data obtained with XMM, Chandra and Suzaku telescopes. I have demonstrated that in the 0.3-1 keV range the heliospheric X-ray emission is responsible for all the diffuse emission previously attributed to hot gas in the so-called Local Interstellar Bubble (100 parsecs wide). A preliminary analysis of the lower energy emission (0.1-0.3 keV) during the last months of my thesis shows that the heliospheric contribution may very well explain most of the supposed Local Bubble emission at these energy ranges too.

Finally, I have used a hybrid model of theMartian plasma environment to model the charge-exchange induced soft X-ray emission from the Martian exosphere. I have used input exosphere parameters from Lyman-α measurements of Mars Express/SPICAM instrument and compared my results with recent Xray observations of Mars with XMM and Chandra satellites.
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https://tel.archives-ouvertes.fr/tel-00260160
Contributor : Dimitra Koutroumpa <>
Submitted on : Monday, March 3, 2008 - 1:56:20 PM
Last modification on : Thursday, December 10, 2020 - 12:34:51 PM
Long-term archiving on: : Thursday, May 20, 2010 - 7:26:14 PM

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  • HAL Id : tel-00260160, version 1

Citation

Dimitra Koutroumpa. Etude des émissions gazeuses UV/X et des phénomènes d'échange de charge dans l'Héliosphère : application à des systèmes astrophysiques analogues.. Astrophysique [astro-ph]. Université Pierre et Marie Curie - Paris VI, 2007. Français. ⟨tel-00260160⟩

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