Analyse des structures magnetiques solaires observees par SOHO. Modelisation magnetohydrodynamique a trois dimensions

Abstract : In the solar atmosphere magnetic structures such as active region loops, filaments-prominences, or sigmoids are observed. These structures are characterized by thermodynamic parameters (temperature, density, pressure) and by the geometry and the topology of the magnetic field structuring the filament. We focus our study on the filaments which are magnetic structures denser and cooler than their coronal environment. Two analysis and diagnostic methods of filaments have been developed : the reconstruction of the 3D coronal magnetic field and the study of magnetohydrodynamic (MHD) waves propagating in the filament.

Using the vector magnetic field measured at the photospheric level, the reconstruction of the coronal magnetic field allows to determine the geometry and the topology of the flux tubes characterizing an active region. Computing the non-linear force-free field, the calculated flux tubes are in good agreement with the system of loops observed in EUV by EIT/SOHO and with the sigmoid observed in soft X-rays by SXT/Yohkoh. We investigate the structure of the filament by studing the possible magnetic dips in the flux tubes supporting the dense filament.

The SUMER/SOHO spectrometer has obtained filament observations which allow us to study the Doppler shift time evolution using the neutral helium line at 58.4 nm. The Fourier analysis of the time series exhibits characteristic frequencies which can be identified to the oscillation modes of Alfvén and magnetoacoustic waves: magnetic and thermodynamic parameters of the filament are derived from an identification method. During MEDOC campaign 5, we performed new observations using the THEMIS telescope capabilities to develop the study of the MHD waves and of the dynamic of an active region filament.
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https://tel.archives-ouvertes.fr/tel-00098267
Contributor : Stephane Regnier <>
Submitted on : Monday, September 25, 2006 - 1:00:58 PM
Last modification on : Friday, April 5, 2019 - 8:11:55 PM
Long-term archiving on : Thursday, September 20, 2012 - 10:51:48 AM

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Stephane Regnier. Analyse des structures magnetiques solaires observees par SOHO. Modelisation magnetohydrodynamique a trois dimensions. Astrophysique [astro-ph]. Université Paris Sud - Paris XI, 2001. Français. ⟨tel-00098267⟩

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