Gradient-drift and resistive mechanisms of the anomalous electron transport in Hall effect thrusters

The problem of the anomalous electron transport in crossed electric and magnetic fields in Hall plasma thrusters is investigated. Two mechanisms of turbulent transport are considered: a gradient-drift mechanism and a resistive one. A strong connection between these mechanisms and the corresponding instabilities is established. Our analysis shows that the gradient-drift transport prevails over the resistive one in the most turbulent domain of the channel. The gradient-drift transport organizes plasma in such a way to minimize the increment of the corresponding instability. This allows one to avoid explicit calculations of the fluctuation intensity while modeling transport phenomena. The modification of the dispersion relation for the gradient-drift instability, offered by Frias et al. (Phys. Plasmas, 19 (2012) 072112) to account for the current-free (vacuum) nature of a two-dimensional magnetic field, is discussed.