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TZID:Europe/Paris
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UID:122@atst.osups.universite-paris-saclay.fr
DTSTART;TZID=Europe/Paris:20251204T140000
DTEND;TZID=Europe/Paris:20251204T170000
DTSTAMP:20251201T222124Z
URL:https://atst.osups.universite-paris-saclay.fr/calendrier/phd-david-pai
 pa/
SUMMARY:PhD defense: David Paipa
DESCRIPTION:I am pleased to invite you to the defense of my PhD thesis. It 
 will be held on Thursday\, December 4\, 2025\, at 2:00 PM\, at the Meudon 
 Observatory (Building 18\, Evry Schatzman Amphitheatre). The event will al
 so be streamed live via the LIRA YouTube channel.\n\nJury composition:\n\n
 \n 	 Christophe LEPONCIN-LAFITTE Président du jury\, LTE\, Observatoire 
 de Paris\n 	 Astrid VERONIG Rapporteur\, Institute of Physics\, Universit
 y of Graz\n 	 Jasmina MAGDALENIC Rapporteur\, Plasma-Astrophysics\, KU Le
 uven\n 	 Alexander WARMUTH Examinateur\, AIP\, Leibniz Institute for Astr
 ophysics Postdam\n 	Hamish REID Examinateur\, MSSL\, University College Lo
 ndon\n 	 Sophie MASSON Examinateur\, LPP\, Observatoire de Paris\n 	 Nic
 ole VILMER Directeur de thèse\, LIRA\, Observatoire de Paris\n 	 Milan M
 AKSIMOVIC Co-directeur de thèse\, LIRA\, Observatoire de Paris\n\nTitle:\
 n"Energetic Particles in Solar Flares: Diagnostics with X-ray and Radio Ob
 servations from Solar Orbiter"\n\nAbstract:\nThe Sun is a powerful particl
 e accelerator. During solar flares a large amount of  energy stored in th
 e sun’s magnetic fields is released. An important fraction of this energ
 y  goes into accelerated particles\, which can reach relativistic velocit
 ies. The electrons that propagate sunward produce Hard X-ray (HXR) bremsst
 rahlung emission. Electrons that propagate outwards though open field line
 s produce type III radio bursts into the Corona and interplanetary (IP) sp
 ace. Despite the sometimes close relation observed between the two emissio
 ns suggest a common accelerator for associated events\, the relationship b
 etween HXR flares and IP type III bursts is not well established.  The tw
 o statistical studies presented in this PhD work use the STIX (HXR)  and 
 RPW (radio) instruments on Solar Orbiter to investigate this link.\n\nIn t
 he first study\, we analyzed the first available period of simultaneous HX
 R and radio observation. The analysis of 15 IP type III bursts with tempor
 ally associated HXR flares revealed that the onset of radio bursts\, which
  is often not associated with the main HXR during the flare\,  is consist
 ently preceded by a reconfiguration of the HXR source morphology. This sug
 gests complex scenarios for reconnection where the evolution of the magnet
 ic morphology of the flare lead to late episodes of  reconnection with op
 en field lines enabling electron escape. The second study describes a more
  quantitative relation of these emissions where 38 HXR/radio events were a
 nalyzed.  Type III bursts with higher peak flux or that show higher excit
 er velocities are  to higher non-thermal electron power and harder electr
 on spectra (lower spectral index) derived from HXR spectroscopy. These res
 ults support a common accelerator and show that the peak flux and the  ve
 locity derived from type III emission reflect the energy content of the  
 radio-emitting electrons\, as predicted by numerical simulations.\n\n(Tran
 smis par David Paipa)
CATEGORIES:Séminaires et soutenances de thèse/HDR
LOCATION:Observatoire de Paris\, Meudon\, 2 place Jules Janssen\, Meudon\, 
 France
X-APPLE-STRUCTURED-LOCATION;VALUE=URI;X-ADDRESS=2 place Jules Janssen\, Meu
 don\, France;X-APPLE-RADIUS=100;X-TITLE=Observatoire de Paris\, Meudon:geo
 :0,0
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DTSTART:20251026T020000
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