Nordita Astrophysics seminars

Shocks, turbulence and particle acceleration in relativistic magnetohydrodynamics

by Camilia Demidem (Nordita)

122:026 ()


Particle acceleration is ubiquitous in the universe as evidenced by the non-thermal features in the spectra of high-energy astrophysical sources or by the regular detection of cosmic rays. Yet, despite continuous theoretical and numerical progress, the mechanisms behind this particle acceleration remain elusive, all the more so in the less studied relativistic regime. Shocks are today widely recognized as promising accelerating regions but their study implies to face a highly non-linear and multi-scale problem where the shock, the turbulence and the non-thermal particles influence each other. In this presentation, I single out some of the processes at play, within the framework of magnetohydrodynamics (MHD). I first present our work in connection with the problem of shock-turbulence interactions; namely, we investigate the response of a perpendicular fast shock to upstream MHD waves by means of 2D special relativistic MHD simulations and demonstrate that this response can be resonant. I then shift the focus towards the problem of stochastic acceleration of test particles interacting with relativistic MHD turbulence and discuss in particular how quasi-linear calculations compare to numerical simulations when accounting for different sources of resonance broadening.