  A full particle simulation study is carried out on the electron acceleration
at a collisionless, relatively low Alfven Mach number (M_A=5), perpendicular
shock. Recent self-consistent hybrid shock simulations have demonstrated that
the shock front of perpendicular shocks has a dynamic rippled character along
the shock surface of low-Mach-number perpendicular shocks. In this paper, the
effect of the rippling of perpendicular shocks on the electron acceleration is
examined by means of large-scale (ion-scale) two-dimensional full particle
simulations. It has been shown that a large-amplitude electric field is excited
at the shock front in association with the ion-scale rippling, and that
reflected ions are accelerated upstream at a localized region where the
shock-normal electric field of the rippled structure is polarized upstream. The
current-driven instability caused by the highly-accelerated reflected ions has
a high growth rate to large-amplitude electrostatic waves. Energetic electrons
are then generated by the large-amplitude electrostatic waves via electron
surfing acceleration at the leading edge of the shock transition region. The
present result suggests that the electron surfing acceleration is also a common
feature at low-Mach-number perpendicular collisionless shocks.
