Quantifying the Absorption Loss of Radiation Belt Energetic Particles by Saturn's Inner Moons

Abstract

AbstractSaturn owns various moons embedded in the magnetosphere, which results in the absorption loss of energetic particles in Saturn's radiation belts when they encounter the body of moons. In the present study, we perform a quantitative analysis of radiation belt energetic electron and proton lifetimes due to the absorption loss by five of inner moons of Saturn (Mimas, Enceladus, Tethys, Dione, and Rhea). Our results show that the resultant averaged lifetimes of energetic particles generally range from ∼0.01 days to infinity, depending strongly on particle energy, equatorial pitch angle, and moon orbit. The averaged lifetimes of energetic electrons increase with increasing electron energy at energies of <1 MeV and peak at the resonance energy, at which the electron drift velocities approach the Kepler velocities of moons. For >1 MeV electrons, the corresponding electron lifetimes decrease as electron energy increases. The averaged lifetimes of protons decrease monotonically with increasing equatorial pitch angles and kinetic energies. We find that the absorption loss by Tethys is the strongest, with the corresponding electron lifetimes shorter than 1 day and the corresponding proton lifetimes shorter than 10 days. The moon absorption effects due to Mimas are the weakest. Our results of energetic particle lifetimes due to the absorption loss by Saturn's moons can be incorporated into future modeling efforts of the radiation belt particle dynamics at Saturn.