Le mardi 19 novembre 2024, Grégory VANDEN BROECK présentera l'examen en vue de l’obtention du grade académique de Docteur en Sciences (Collège de doctorat en SCiences spatiales) sous la direction de Gregor RAUW et Sabrina BECHET.

Cette épreuve consistera en la défense publique d’une dissertation intitulée :

“ Evolution of chromospheric structures observed with USET and implications for the Sun seen as a star ”

Abstract

The physical mechanisms governing the magnetic activity of stars, as well as the variations in their activity cycles, are crucial research topics with direct implications on the understanding of stellar evolution and interactions with their surroundings. Although these mechanisms remain largely unknown, they are currently at the focus of intensive research in astrophysics. Whilst most stars typically appear as unresolved points in the sky due to their considerable distance, the Sun provides a unique opportunity to analyse more closely the phenomena of magnetic activity and the spatial distribution of active regions on its surface. By studying the Sun, we not only learn about this star that sustains our existence but also explore similar mechanisms acting in other stars. The Sun's atmosphere is composed of distinct layers displaying magnetic phenomena in different ways. This research focuses on the intermediate layer of the solar atmosphere, the chromosphere. Since July 2012, a specialized telescope at the Royal Observatory of Belgium in Uccle has been dedicated to observing this layer through the Ca II K line, capturing essential data for studying the evolution of the chromospheric magnetic structures.

Le Jury sera composé de :

M. M.-A. DUPRET (Président), Mmes et MM. S. BECHET (Observatoire Royal de Belgique) (Co-promotrice), T. CHATZISTERGOS (Max Planck Institute for Solar System Research), F. CLETTE (Observatoire Royal de Belgique), I. ERMOLLI (Osservatorio Astronomico di Roma), Y. NAZE (Secrétaire), G. RAUW (Promoteur).