A physical model for electron radiation belts of Saturn

Abstract

Radiation belts cause irreversible damages to on‐board instrument materials. Studies about radiation belts can provide precious information for future interplanetary missions. Pioneer 11, Voyager 2 and nowadays Cassini missions give the characteristics of Saturn's inner magnetosphere: Saturn's famous rings, various moons, neutral particles ejected from Enceladus and waves. Thanks to its experience with the Earth's and Jupiter's radiation belt studies, ONERA is now able to develop an electron radiation belt model for Saturn's environment, i.e., a new version of Salammbô. The study of Saturn's inner magnetosphere emphasizes the most important physical processes governing radiation belt dynamics: electrons losses due to dense rings are the dominant physical process near the planet (L < 2.3). For high energies (E > ∼50 keV), radial diffusion and local losses due to the moons are predominant from L = 2.3 to the boundary condition (L = 6). The analysis of spacecraft in situ data (Pioneer 11, Voyager 2, and Cassini) allows a boundary condition to be built for the model and the Salammbô results to be validated. The Salammbô Kronian model has also been compared to the empirical radiation belt model SATRAD (for SATurn RADiation model) based on Pioneer 11 and Voyager 2 data. Comparisons of Salammbô results with in situ data and SATRAD confirm that Salammbô is a good mean model for Saturn electron radiation belts, for energies from about a hundred keV to a few MeV.