  Electron acceleration in high Mach number perpendicular shocks is
investigated through 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 simulation. 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.
