27–31 Aug 2018
LVH, Luisenstraße 58, 10117 Berlin
Europe/Berlin timezone

Kinetic modeling of low Mach number collisionless shocks in galaxy clusters

27 Aug 2018, 16:55
15m
-3- Rudolf Virchow

-3- Rudolf Virchow

Talk Extragalactic Extragalactic Science

Speaker

Dr Jacek Niemiec (Institute of Nuclear Physics Polish Academy of Sciences)

Description

Collisionless shocks are found in a number of astrophysical objects, ranging in size from the Earth's bow shock through solar flares, termination shock of the solar wind, supernova remnant shocks, and merger shocks in galaxy clusters. In the latter case, low Mach number (Ms << 10) shocks are found propagating in a high beta (β > 1) plasmas, where β is the ratio of thermal to magnetic pressure. Observations in X-ray and radio show that cluster shocks are electron accelerators to non-thermal energies. However, the mechanism of particle energization is poorly known. Recent studies with kinetic PIC simulations suggested the so-called shock-drift acceleration followed by particle-wave interactions in the shock upstream as a mechanism of electron injection in high-β regime. However, other works demonstrated the importance of the multi-scale shock structure which includes ion-scale shock-rippling fluctuations that can significantly alter the injection mechanism. Here we present preliminary results of our first-principles 2D large-scale PIC simulations of shocks for conditions of high-β plasmas, as appropriate to galaxy clusters. The aim is to investigate the multi-scale electron injection physics. We demonstrate the slowly growing rippling modes to emerge after a few tens of ion gyro times and their appearance is marked with an increase in accelerated electron energy. This suggests an energization mechanism that is different from processes identified so far in low Mach number shocks. The micro-physics of these processes is now under detailed investigation whose results will be presented at the conference.

Primary authors

Dr Jacek Niemiec (Institute of Nuclear Physics Polish Academy of Sciences) Dr Oleh Kobzar (Institute of Nuclear Physics Polish Academy of Sciences)

Co-authors

Martin Pohl (DESY) Prof. Masahiro Hoshino (University of Tokyo) Shuichi Matsukiyo (Kyushu University) Dr Takanobu Amano (University of Tokyo)

Presentation materials