On plasma acceleration in magnetic nozzle/mirror configurations

This talk provides an overview of the basic physics of plasma acceleration in the converging-diverging magnetic field configurations such as magnetic mirrors for plasma confinement and magnetic nozzles for electric propulsion. A simple fluid model of the quasineutral plasma flow in the magnetic nozzle predicts a unique profile of the accelerated plasma strongly coupled to the magnetic field profile via the regularization condition at the sonic point, i.e. at the point where the plasma flow velocity is equal to the local ion sound velocity. The results of the full kinetic model for ions and electrons, including the Poisson equation, demonstrate similar robustness in the global profiles of plasma density, ion velocity, and potential profiles. The development of anisotropies in electron and plasma pressure, electron and ion heat fluxes, energy conversion between electrons and ions, and their role in plasma acceleration are discussed using fluid and kinetic models. Conversion of the energy of azimuthal plasma rotation and magnetic field and resulting plasma acceleration are discussed using the electromagnetic model.