A 10-moment multi-fluid model for partially ionized, partially magnetized plasmas*

Fluid moment models are an attractive option for plasma modeling because macroscopic behavior can be described without needing to track individual particle trajectories. However, the key challenge of fluid models is the closure problem.  Particularly in the presence of a magnetic field, anisotropic transport can lead to  deviation from local equilibrium, i.e., a Maxwellian velocity distribution function. In this study, a 10-moment multi-fluid model is developed to capture non-equilibrium, non-Maxwellian effects in low-temperature magnetized plasmas. In addition to mass density and bulk velocity, the full pressure tensor is accounted for, allowing one to capture anisotropy and shear effects without needing explicit viscosity models. Closure is obtained by extension of a Braginskii-type heat flux obtained using Chapman-Enskog expansion. The one-dimensional model is developed and applied to the discharge plasma in a Hall-effect thruster, and compared to both a 5-moment (equilibrium) fluid model [1] and a  particle-in-cell Monte-Carlo-Collision model [2].