Fast Particle Acceleration in 3D Hybrid Simulations of Quasiperpendicular Shocks.

Abstract

Understanding the conditions conducive to particle acceleration at collisionless, nonrelativistic shocks is important for the origin of cosmic rays. We use hybrid (kinetic ions-fluid electrons) kinetic simulations to investigate particle acceleration and magnetic field amplification at nonrelativistic, weakly magnetized, quasiperpendicular shocks. So far, no self-consistent kinetic simulation has reported nonthermal tails at quasiperpendicular shocks. Unlike 2D simulations, 3D runs show that protons develop a nonthermal tail spontaneously (i.e., from the thermal bath and without preexisting magnetic turbulence). They are rapidly accelerated via shock drift acceleration up to a maximum energy determined by their escape upstream. We discuss the implications of our results for the phenomenology of heliospheric shocks, supernova remnants, and radio supernovae.