  Mildly relativistic shocks in magnetized electron-ion plasmas are
investigated with 2D kinetic particle-in-cell simulations of unprecedentedly
high resolution and large scale for conditions that may be found at internal
shocks in blazar cores. Ion-scale effects cause corrugations along the shock
surface whose properties somewhat depend on the configuration of the mean
perpendicular magnetic field, that is either in or out of the simulation plane.
We show that the synchrotron maser instability persists to operate in mildly
relativistic shocks in agreement with theoretical predictions and produces
coherent emission of upstream-propagating electromagnetic waves. Shock front
ripples are excited in both mean-field configurations and they engender
effective wave amplification. The interaction of these waves with upstream
plasma generates electrostatic wakefields.
