Absence of Electron Surfing Acceleration in a Two-dimensional Simulation

Abstract

Electron acceleration in high Mach number perpendicular shocks is investigated through a two-dimensional electrostatic particle-in-cell (PIC) simulation. We simulate the shock-foot region by modeling particles that consist of three components-such as incident protons and electrons, and reflected protons in the initial state-which satisfies the Buneman instability condition. In contrast to previous one-dimensional simulations in which strong surfing acceleration is realized, we find that surfing acceleration does not occur in two-dimensional simulations. This is because excited electrostatic potentials have a two-dimensional structure that makes electron trapping impossible. Thus, the surfing acceleration does not work either in itself or as an injection mechanism for the diffusive shock acceleration. We briefly discuss implications of the present results on the electron heating and acceleration by shocks in supernova remnants.