Erlangen 2018 – scientific programme
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P: Fachverband Plasmaphysik
P 14: Astrophysical Plasmas - Poster
P 14.4: Poster
Tuesday, March 6, 2018, 16:15–18:15, Redoutensaal
Mechanism of enhanced energization of heavier ions in collisionless shocks — •Adrian Hanusch1, Tatyana Liseykina1, and Mikhail Malkov2 — 1Universität Rostock - Institut für Physik — 2University of California San Diego
The acceleration of particles to high energies is an outstanding problem in space and astrophysical plasmas. One physically simple and robust mechanism of interest is diffusive acceleration (DSA) at collisionless shocks [1]. Before acceleration to high energies can occur, particles must be pre-accelerated above the energies of the background plasma so that they may then keep on crossing the shock front and gain more energy. This injection process is still not fully understood. To simulate the evolution of collisionless shocks and the acceleration of ions we use a hybrid code in which only the plasma ions are treated kinetically and electrons as a massless fluid. In our simulations shocks are generated by sending a super-sonic flow of multi-component plasma, consisting of electrons, background protons and additional ion species with different mass to charge (A/Z) ratios, towards a reflecting wall. To investigate the elemental selectivity of the injection mechanism, we determine the injection efficiency of each particle species included in the simulation. We obtain the energy spectra of all particles downstream of the shock transition from the simulation using a logarithmic binning procedure. Comparing the distributions of the number of shock reflections vs. single particle energy for different A/Z we observe the increasing narrowness of such distribution with A/Z.
[1] A. R. Bell, MNRAS, 182, 147-156, (1978).