A computer simulation on microinstabilities and anomalous resistivity near the magnetic neutral sheet

Microinstabilities in a field-reversed plasma were studied using a 2 D magnetostatic particle code. It was observed that a flute instability occurs in local regions with steep density gradient off the neutral sheet; its frequency is approximately the lower-hybrid frequency and the wavelength is near the electron Larmor radius. The observed dispersion relation suggests that the instability must be the lower-hybrid-drift instability (LHDI). The initial laminar diamagnetic current is rapidly disturbed to form E x B electron vortices, with simultaneous electron and ion acceleration in the neutral sheet. On the neutral line where the plasma Beta is extremely large, an unstable electromagnetic mode is observed to develop after the LHDI saturates; accordingly, the magnetic neutral line is deformed into a meandering structure. Anomalous resistivity and anomalous plasma transport are observed associated with the development of the LHDI; even on the neutral line there exists a small but finite resistivity which is attributed to the unstable magnetic mode.