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.