University of Minnesota
School of Physics & Astronomy

Physics and Astronomy Calendar

Tuesday, January 31st 2017
12:20 pm:
Speaker: Sophie Musset, University of Minnesota
Subject: Energetic electrons acceleration and transport in the corona (via X-ray diagnostics): from RHESSI data analysis to the preparation of the STIX experiment on Solar Orbiter.

An important fraction of the magnetic energy released during solar flares is transmitted to ambient particles which can be accelerated to energies of several hundreds of keV to a few keV for electrons, and several tens to a few hundreds of MeV for ions. Yet, we only poorly know the details of the physical mechanisms responsible for fast and efficient particle acceleration, and for the transport of energetic particle between acceleration sites and interaction sites where they emit electromagnetic radiation. I will present the work conducted during my PhD preparation at the Observatoire de Paris, in the context of the study of solar energetic electron acceleration and transport in the solar corona through X-ray diagnostics.

In the first part of the seminar, I will present how I investigated the link between energetic electron X-ray emissions and electric current densities measured at the photospheric level during X-class solar flares. This work shows that energetic electron acceleration sites are located above the highest current densities for several X-class flares. A common evolution of X-ray emission and photospheric electric currents has also been shown during a flare (Musset et al 2015). In a second study, I examined the effect of transport in the corona on the energetic electron distribution during a flare. A fraction of energetic electrons are trapped in the coronal part of the flare loop, and it can be explained with a diffusive transport model. Combining X-ray and radio observations, the scattering mean free path was estimated at different electrons energies for the first time in the solar corona, and shown to be decreasing with increasing energy.

In the second part of the seminar, I will present the STIX instrument onboard Solar Orbiter, which will provide X-ray diagnostics of the sources of energetic electrons in the solar corona. I will briefly present the challenges and some of the advances made in term of onboard and analysis software for this experiment.

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