Dependence of plasma dynamics on the strength of spatiotemporal-changing magnetic field in an RF plasma thruster using rotating magnetic field acceleration method

Abstract The rotating magnetic field (RMF) acceleration method is a newly proposed approach to enhance the performance of electrodeless radio frequency (RF) plasma thruster. In the previous study, electron current drive in the azimuthal direction was observed using the RMF method, which resulted in the electromagnetic force in the presence of a magnetic nozzle. To further optimize the acceleration effect with the RMF method, we investigated the dependence of spatial profiles of plasma parameters and the driven current density on the RMF field strength. We observed a higher azimuthal-current density in plasma compared to the previous campaign. According to spatial electrostatic probe measurements, the ion Mach number spatially increases with the increase in RMF strength. The ion acceleration on the z -axis can result from the presence of spatial convergence of electron pressure due to radial electron transport. Total thrust composed of a static pressure term and electromagnetic force increases with higher RMF strength under the full penetration condition of the RMF. We clarified the strengthening RMF field contributes to the enhancement of the azimuthal current and spatial ion acceleration effect, leading to the thrust increment. These findings, although the thrust performance is not yet at a practical level, hold significant potential for the future optimization of the RMF acceleration method applied to electrodeless RF plasma thrusters.