Instability analysis of rotating plasma in stationary gas

A numerical study is conducted using a magnetohydrodynamics (MHD) code to a nalyze a unique plasma structure-the persistent spiral arm structure-observ ed in experiments by Ikehata et al. [Phys. Rev. Lett. 81 (1998) 1853]. The numerical simulation suggests that the structure is caused by centrifugal i nstability as proposed by them.