PIC and fluid simulations of magnetized plasma expansions for electric propulsion*

This presentation discusses recent efforts on modeling magnetized plasma expansions in the context of electric propulsion. First, we focus on the magnetic arch, a novel magnetic topology that forms when two magnetic nozzles of opposing polarities are placed side by side so that their lines interconnect. This is a fully 3D problem, but it is preliminarily tackled as a planar 2D problem with (1) a fluid code and (2) a hybrid PIC/fluid code, to investigate the plasma extraction from the closed magnetic lines, the effect of the plasma-induced magnetic field, and that of collisionality with background neutrals (facility effects). Results show that a plasma jet can be extracted from the closed-line configuration, with a divergence lower or comparable to that of a single magnetic nozzle, albeit with a slightly lower energy. This finding is in agreement with experimental mesaurements.

Secondly, we show the propagation and absorption of RHP electromagnetic waves and the kinetic features of plasma expansion in a paraxial magnetic nozzle a novel electromagnetic, time-implicit particle-in-cell code (TIPIC). Contrary to explicit PIC codes, this model is energy-conserving and enables to overcome their timestep and cellsize constraints, producing accurate solutions at a fraction of the computational cost. We compare the solution with a prescribed cold plasma wave and the self-consistent Darwin solution. TIPIC is currently 1D3V, but is considered a crucial stepping stone toward practical yet predictive simulation capabilities for electric propulsion in higher dimensionality.