11:00 am–12:00 pm ERC 545
Host: Emily Lichko
Sophie Aerdker (Ruhr-Universität Bochum) "Time-dependent diffusive shock acceleration: The case of a Galactic wind termination shock"
The origin of cosmic rays (CRs) in the transition region between the spectral knee and ankle is still unknown. One source that might contribute is the Galactic wind termination shock (GWTS) which may emerge when the Galactic wind slows down due to interaction with the Intergalactic Medium. CRs pre-accelerated in the Galactic disk are advected outwards and re-accelerated at the GWTS. When they make it back to the Galaxy, they can contribute to the transition region of the CR spectrum. Motivated by this scenario, I will present a numerical model for time-dependent Diffusive Shock Acceleration (DSA) based on the stochastic differential equation solver (DiffusionSDE) of the cosmic ray propagation framework CRPropa 3.2 with two modifications: An importance sampling module is introduced to improve statistics at high energies in order to keep the simulation time short. An adaptive time step is implemented to efficiently meet constraints on the time and diffusion step, which is crucial to obtain the correct shock spectra. I present first results on CR re-acceleration at a GWTS by considering a spherically symmetric shock, a spiral Galactic magnetic field, and anisotropic diffusion. I will also discuss the effect of parameters like the diffusion tensor, adiabatic cooling in the expanding wind and a finite shock lifetime on the acceleration time scale as well as the probability of CRs to diffusive back to the Galaxy.
