Nonlinear simulations and anomalous transport in hall thruster plasma

摘要

Summary form only given. The plasma inside a Hall thruster is a complex environment full of instabilities and interesting physical phenomena such as anomalous transport. To better understand this complex plasma dynamics, a nonlinear fluid model has been developed. The model contains the effect of electron inertia, electron collisions, electron temperature and density gradients as well as nonlinearities in the ion velocity and the electron advection term that arises from the ExB drift. The model is simulated using BOUT++, a framework for plasma simulations developed at the Lawrence Livermore National Laboratory. The linear limits of the model correspond to the lower hybrid mode rendered unstable by collisions and to the density gradient drift instabilities. Two cases are simulated using BOUT++, one without density gradients and one with density gradients. Both these cases exhibit energy saturation as well as an axial current much larger than the classical collisional value. The simulations with density gradients seem to show a larger axial electron current as well as exhibiting azimuthally propagating structures similar to the spokes observed experimentally.