An overview of discharge plasma modeling for Hall effect thrusters

The current status and challenges of the discharge plasma modeling capabilities in Hall effect thrusters (HETs) are reviewed. Partially magnetized plasmas in HETs present unique physics in that collisions with neutral atoms (a feature of low-temperature plasmas) and instabilities and oscillations (a feature of high-temperature plasmas) coexist. A discharge plasma model is constructed by choosing the numerical methods, e.g. fluid or kinetic, for individual plasma constituents, including neutral atoms, ions, and electrons. The governing equations, boundary conditions, and collision models of a xenon discharge plasma in HETs are discussed. Various models are used to illustrate device-scale phenomena, including the breathing mode and azimuthally rotating spokes, as well as small-scale physics, such as the electron cyclotron drift instability and current-carrying instability that may occur in a hollow cathode plume.