Prof.
Jacek Niemiec
(Institute of Nuclear Physics Polish Academy of Sciences)
Radio and X-ray observations of so-called radio relics indicate electron acceleration at merger shocks in galaxy clusters. These large-scale shocks are also candidate sites for ultra-high-energy cosmic ray production. Merger shocks have low Mach numbers and propagate in high beta plasmas, . Particle acceleration and in particular electron injection mechanisms are poorly understood in such conditions. Here we report results of our large-scale 2D particle-in-cell simulations of cluster shocks that allow the development of multi-scale turbulence in the shock transition, including ion-scale shock rippling modes. We show that the presence of turbulence in multi scales is critical for efficient electron pre-acceleration. The main injection process is stochastic Shock Drift Acceleration, in which electrons are confined in the shock region by pitch-angle scattering off magnetic turbulence and gain energy from motional electric field. Wide-energy non-thermal electron distributions are formed both upstream and downstream of the shock. We demonstrate that the downstream electron spectrum has a power-law form with index , in agreement with observations. Pre-acceleration to very high energies occurs that should lead to electron injection to Diffusive Shock Acceleration processes in the presence of long-wave MHD upstream turbulence.
Prof.
Jacek Niemiec
(Institute of Nuclear Physics Polish Academy of Sciences)
Dr
Oleh Kobzar
(Institute of Nuclear Physics Polish Academy of Sciences)
Dr
Takanobu Amano
(Department of Earth and Planetary Science, University of Tokyo)
Prof.
Masahiro Hoshino
(Department of Earth and Planetary Science, University of Tokyo)
Prof.
Shuichi Matsukiyo
(Faculty of Engineering Sciences, Kyushu University)
Dr
Yosuke Matsumoto
(Department of Physics, Chiba University)
Prof.
Martin Pohl
(Institute of Physics and Astronomy, University of Potsdam, DESY-Zeuthen)
