Attenuation of Solar Energetic Particles by Wave-Particle Interaction with an Ion Thruster Plume

Solar energetic particles (SEP) are a significant concern for interplanetary human spaceflight. This work investigates wave-particle interactions caused by the incidence of a beam of energetic protons, representing a notional SEP event, onto a cloud of xenon ions and neutrals, representing a notional ion thruster plume. The resulting electromagnetic ion/ion instability is developed to investigate the degree to which energetic protons can be scattered out of the initial beam and toward isotropy, and to characterize the electromagnetic radiation generated by the interaction. Thruster orientation and plume ion density and energy are examined to determine how powerful an ion thruster would need to be in order to meaningfully mitigate the effects of a SEP event in the vicinity of a spacecraft in interplanetary space.