A 10-Moment Multi-Fluid Model for Low-Temperature Partially Magnetized Plasmas

Fluid moment models are an attractive option to model devices because they can describe the macroscopic device-scale behavior of an ensemble of particles without needing to track individual particle trajectories. In plasma devices, non-Maxwellian effects may arise due to the coupling between plasma-wall interactions, collisions, and instabilities. While kinetic models can describe distributions far from equilibrium, these models are often computationally more expensive than conventional fluid models, e.g., drift-diffusion or generalized Ohm's law. In this study, a 10-moment multi-fluid model is developed to capture non-equilibrium and non-Maxwellian effects in low-temperature magnetized plasmas. The model solves for the number density, three components of bulk velocity, and six components of a symmetric pressure tensor. Closure is obtained by extension of the typical Braginskii-type heat flux obtained using Chapman-Enskog expansion. The one-dimensional model is developed to simulate the dynamics of ions, electrons, and neutrals and is applied to the discharge plasma in a Hall-effect thruster and compared to the results obtained from a 5-moment fluid model and a kinetic particle-in-cell Monte Carlo collision model. The off-diagonal terms of the pressure tensor allow for a direct modeling of shear, which can give better insight into shear-induced cross-field transport and the non-Maxwellian effects which can be indicative of plasma turbulence in low-temperature magnetized plasmas.