Electron acceleration due to small pulses in shock waves in inhomogeneous plasmas: Perpendicular propagation

Abstract

Electron acceleration in shock waves propagating perpendicular to an external magnetic field, which is inhomogeneous and reversed in a finite region, is studied with relativistic particle simulations. By the time a shock wave reaches the inhomogeneous region, some electrons are energized by a small compressive pulse generated in the shock wave. After penetrating this region, the original shock wave is damped. However, a new shock wave with the magnetic polarity opposite to that of the original shock wave is excited. In this secondary shock wave, particle-accelerating compressive pulses are also generated. Further, after the encounter with the original shock wave, the magnetic null point starts to move with a slightly slower speed than the secondary shock wave, and electric fields are formed around it. Some electrons also gain energy in meandering orbits around the field-reversed pulse.