Particle-in-Cell Simulation of Anomalous Transport in a Penning Discharge

Results are presented from two-dimensional (radial-azimuthal), electrostatic Particle-In-Cell simulations of a Penning discharge, where an electron beam is injected along the axis, parallel to the magnetic field, into a cylindrical plasma radially bounded by grounded metal. In preliminary, one-dimensional (radial) simulations, the anomalous electron transport is solely due to the instability of the pure lower-hybrid mode. With also the azimuthal direction numerically resolved, the Simon-Hoh mode becomes active and the lower-hybrid mode is destabilized by density-gradient effects. In the more realistic, twodimensional simulations, the lower-hybrid and Simon-Hoh modes both contribute to the anomalous transport. These latter simulations demonstrate the excitation of an azimuthally asymmetric, spoke-like structure rotating in the direction of ExB and electron diamagnetic drifts and persisting throughout the remainder of this simulation. The spokes are characterized by an increase in plasma density and are shown to channel most of the radial leakage current. The spoke appears similar to the one seen in experiments and it exhibits the same scaling with ion mass. The Hall parameter in the simulations is also in good agreement with experiment.