Title of the thesis
Acceleration of energetic particles in coronal mass ejections.
Composition of the jury
- Marie-Christine ANGONIN (Sorbonne Université) - Examinatrice
- Pierre HENRI (OCA) - Rapporteur
- Simone LANDI (Université de Florence) - Rapporteur
- Petr HELLINGER (IAP, CAS) - Examinateur
- Barbara PERRI (CEA Saclay) - Examinatrice
- Filippo Pantellini (LIRA Observatoire de Paris-PSL) - Superviser
- Léa Griton (LIRA Observatoire de Paris-PSL) - Superviser
Abstract
The interplanetary medium, dominated by the solar wind, is populated by a wide variety of particles, from thermal populations to relativistic particles of solar or cosmic origin. The interaction between these particles and the transient structures of the solar wind, such as coronal mass ejections (CMEs), plays a major role in their transport and acceleration. Understanding these interactions requires combining a realistic description of the large-scale electromagnetic fields, provided by magnetohydrodynamics (MHD), with a kinetic model capable of accounting for the individual dynamics of the particles. During this thesis, a particle code was developed, based on the centre-guide approximation in the relativistic regime. It is used to simulate the propagation of charged particles in 3D electromagnetic fields derived from MHD simulations. Two main studies were carried out using this tool. The first concerns the propagation of quasi-relativistic electrons in a stationary solar wind. It highlights a loss of particle energy, attributed to their drift along the convective electric field, and reproduces the angular distributions measured by the WIND probe at 1 AU. The second study focuses on the interaction of a CME modelled by a spheromak with 5 GeV relativistic protons. The results show that the transient fields of the CME profoundly modifient the spatial distribution of the particles and significantly broaden their energy spectra, the energy gain being mainly related to gradient drift in regions of high ∇B.
