Particle acceleration at ultrarelativistic, perpendicular shock fronts

ABSTRACT Using an eigenfunction expansion to solve the transport equation, complemented by Monte Carlo simulations, we show that ultrarelativistic shocks can be effective particle accelerators even when they fail produce large amplitude turbulence in downstream plasma. This finding contradicts widely held belief a uniform magnetic field perpendicular shock normal inhibits acceleration first-order Fermi process. In limit, find stationary power-law spectrum of index s = 4.17 for these shocks, close predicted strictly parallel shock.