14-moment maximum-entropy modeling of collisionless ions for Hall thruster discharges

Ions in Hall effect thrusters are often characterized by a low collisionality. In the presence of acceleration fields and azimuthal electric field waves, this results strong deviations from thermodynamic equilibrium, introducing kinetic effects. This work investigates application 14-moment maximum-entropy model to problem. method consists set 14 partial differential equations (PDEs) for density, momentum, pressure tensor components, heat flux vector, fourth-order moment associated with particle velocity distribution function. The is applied study collisionless ion dynamics thruster-like configuration, its accuracy assessed against different models, including Vlasov equation. Three test cases considered: purely axial problem, problem ion-wave trapping, finally evolution ions axial-azimuthal plane. Most considers only, coupling electrons removed prescribing reasonable values field. allows us obtain direct comparison among models. However, possibility run self-consistent plasma simulations also briefly discussed, considering quasi-neutral or multi-fluid system appears be robust accurate option considered cases. improved over simpler pressureless gas (cold ions) Euler dynamics, while computational cost shows remain much lower than simulations.