Effect of ion composition on ion acceleration by magnetosonic shock waves

Abstract

The study of heavy-ion acceleration by magnetosonic shock waves in multi-ion-species plasmas [M. Toida and Y. Ohsawa, Solar Physics 171, 161 (1997)] is extended to the case in which the ion masses are of the same order of magnitude; specifically, the effect of mass and density ratios is examined for H-T and D-T plasmas with three-dimensional, electromagnetic, particle simulations. The frequency difference Δω, where Δω=(ω+0−ω−r)∕ω+0 with ω+0 the cut-off frequency of the high-frequency magnetosonic mode and ω−r the resonance frequency of the low-frequency mode, is a key parameter in the generation of shock waves from a disturbance. In H-T plasmas with nH⪡nT and with nH⪢nT and in D-T plasmas with any density ratio, Δω is small, and the high-frequency-mode shock wave is mainly generated and plays a central role in ion energization processes. In H-T plasmas with nH=nT, for which Δω is much greater, both the high- and low-frequency-mode shock waves are generated and contribute to the acceleration.