RESONANT ION-ACCELERATION BY OBLIQUE MAGNETOSONIC SHOCK-WAVE IN A COLLISIONLESS PLASMA

A magnetosonic shock wave propagating obliquely to a magnetic field is studied by theory and simulation, with particular attention to the resonant ion acceleration (the υp×B acceleration) by the shock. Theoretical analysis based on a two-fluid model shows that, in the laminar shock, the electric field strength in the direction normal to the wave is about (mi/me)1/2 times larger for the quasiperpendicular shock than that for the quasiparallel shock, which is a reflection of the fact that the width of the quasiperpendicular shock is much smaller than that of the quasiparallel shock. Time evolution of a totally self-consistent magnetosonic shock wave is studied by using a 2 1/2 -dimensional fully relativistic, fully electromagnetic particle simulation with full ion and electron dynamics. Even the low Mach number shock wave can significantly accelerate some ions by the υp×B acceleration. The resonant ion acceleration occurs more strongly in the quasiperpendicular shock, because the magnitude of this acceleration is proportional to the electric field strength. © 1986 American Institute of Physics.