Theory and simulations of relativistic particle motions in a magnetosonic shock wave
SHUNSUKE USAMI a1andY. OHSAWA a2 a1 Computer and Information Network Center, National Institute for Fusion Science, 322-6 Oroshi-cho, Toki, Gifu 509-5292, Japan a2 Department of Physics, Nagoya University, Nagoya 464-8602, Japan
The motions of relativistic particles in a magnetosonic shock wave propa- gating obliquely to an external magnetic field are studied. In the zeroth-order theory, particles continue to move nearly parallel to the external magnetic field in the shock transition region, when the shock speed is close to $c \cos \theta$, where $c$ is the speed of light and $\theta$ is the propagation angle. Perturbations to this zeroth-order motion are also analyzed for positrons and ions. The perturbation frequency of positrons is $\omega \sim \Omega_{\rm p0} \gamma^{-1}$ and that of ions is $\omega \sim \Omega_{\rm i0} \gamma^{-1/2}$, where $\Omega_{\rm p0}$ and $\Omega_{\rm i0}$ are the non-relativistic gyrofrequencies of positrons and of ions, respectively, and $\gamma$ is the Lorentz factor. These theoretical predictions are confirmed with numerical simulations.
(Received August 15 2005) (Accepted December 20 2005)
