Numerical Simulation of Plasma Perturbations and Electron Transport in Hall Thrusters

抄録

Identification of the spatio-temporal structure of plasma turbulence will be key to understanding anomalous electron transport driven by plasma perturbations in Hall thrusters. A radial-axial (r–z) two-dimensional three-velocity fully kinetic particle-in-cell simulation was performed for a 100 W class Hall thruster. The electron transport across the magnetic field was estimated and compared to the fluid-based electron drift-diffusion model. The cross-field electron transport outside the channel was found to be larger than that deduced from the classical diffusion model, and the electron inertia terms were found to play a significant role. That is, the electron transport outside the channel can be explained by the so-called “Reynolds stress” derived from the plasma turbulence. The frequency of the perturbations was observed to be several tens of MHz, and the wave number was found to be several thousand m⁻¹. The perturbation is identified as ion acoustic waves; the dispersion relation agrees well with that of ion acoustic waves, and the Boltzmann relation is satisfied.