Numerical Modeling of Rotating Spokes in Hall Thruster Discharge Plasma

Abstract

Rotating spoke is a coherent structure observed in cross-field devices, such as Hall effect thrusters (HETs), magnetrons, and Penning discharges. In spite of being frequently observed in the experiments, it has been numerically challenging to perform stable calculations using electron fluid models to model rotating spokes. It is suggested that the electron fluid model using drift-diffusion approximation is mathematically ill-conditioned due to the differences (e.g. 100-1000 times) in the characteristic speeds of the electron velocity in the axial and azimuthal directions 1. We have developed a robust pseudo-time stepping method that solves the diffusion equation to model magnetized electron fluid 2, which uses the drift-diffusion model but can be calculated more robustly and stably by adding time derivative terms. The steady-state solution is the converged solution of the diffusion equation. This model has been used to model the discharge plasma in HETs in the radial-axial direction.