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Caractérisation et Modélisation du flux solaire EUV

Abstract : he study of solar-terrestrial connections is a challenging science, because of the physical problems it implies and because of its growing impact on our societies, this last point being illustrated by the expansion of the study of space weather. In this context, this work aims to improve the knowledge and the modelling of the solar extreme ultraviolet flux which is the major cause for the existence of the planetary (and in particular terrestrial) ionosphere. An original processing of the measurements of the SUMER spectrometer onboard SOHO allows the retrieval of an important statistic of the solar emission lines intensities emitted in the quiet regions and the coronal holes of the solar atmosphere, during a significant part of the solar cycle. The amount of collected data permits the study of the transition region network and its variation during the solar cycle; no major changes of the cells and network elements structure is found with the activity. Using these results, we compute synthetic spectra through diffential emission measures (DEM) for the 2 regions of the solar atmosphere cited above. The comparison between TIMED/SEE data and a computation based on these 2 synthetic spectra and the one from an active region shows good agreement. Finally, we extend the DEM concept to the whole sun, and compute the solar EUV irradiance spectrum from the measurements of 5 solar lines, for a 100 day period. Comparisons at other wavelengths with the TIMED/SEE data reveal close similarities.
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https://tel.archives-ouvertes.fr/tel-00005279
Contributor : Matthieu Kretzschmar <>
Submitted on : Wednesday, March 10, 2004 - 2:03:21 PM
Last modification on : Friday, November 6, 2020 - 4:04:46 AM
Long-term archiving on: : Friday, April 2, 2010 - 8:12:35 PM

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  • HAL Id : tel-00005279, version 1

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Citation

Matthieu Kretzschmar. Caractérisation et Modélisation du flux solaire EUV. Astrophysique [astro-ph]. Université Joseph-Fourier - Grenoble I, 2002. Français. ⟨tel-00005279⟩

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