Electromagnetic signal modification in a localized high-speed plasma flow: Simulations and experimental validation of a stationary plasma thruster

Plasmas alter high-frequency electromagnetic signals primarily through strong electron density gradients or electron densities approaching the critical plasma density. A plasma can potentially degrade electromagnetic systems through signal attenuation as well as increased amplitude or phase noise. This paper reviews the physical mechanisms of a plasma which cause phase shift, attenuation, phase modulation, and amplitude modulation. To make predictions of these effects, a general ray-tracing method is also reviewed and then applied to the localized high-speed plasma flow of a stationary plasma thruster (SPT). The SPT is currently being tested and considered for use aboard next-generation spacecraft, where careful consideration must be given to possible interactions with satellite electromagnetic systems such as for communication, navigation, and remote sensing. The study also models the rather significant plume impact to phase and amplitude for a range of frequencies. A summary is provided of ray-tracing simulations characterizing both phase and amplitude effects at frequencies from 0.5 to 17 GHz and thruster axial positions from 0.25 m to 1.5 m. The results correlate well with known data.