Energetic particle absorption by atmosphereless satellites and rings

In outer planet magnetospheres, theoretical estimates of the rate of energetic particle absorption by solid satellites and rings have two primary applications. First, in regions where satellite absorption is the dominant energetic particle loss process, model calculations combined with measured fluxes and derived phase space densities can be employed to constrain the amplitude and L-dependence of the magnetospheric radial diffusion process that is responsible for populating the radiation belts. Since only flyby data are available, this approach provides the only present means for probing the dynamics of outer planet radiation belts. Second, if the rate of radial diffusion is independently constrained, observed ring absorption signatures can be combined with model calculations to solve for certain undetermined parameters such as the mean particulate size in a planetary ring. Examples of applications to radial diffusion in the Uranian radiation belts and to the interpretation of the Jovian ring absorption signature in Pioneer 11 energetic particle data are discussed.