Magnetosphere, Rings, and Moons of Uranus

The observation of an ultraviolet aurora on Uranus implies the existence of a magnetosphere. It is suggested that the magnetospheres of Uranus and Saturn may be very similar. Charged particle sputtering of water ice surfaces on the Uranian moons may maintain an oxygen ion plasma torus similar to the heavy ion plasma torus at Saturn. Atmospheric cosmic ray albedo neutron decay may sustain an inner radiation belt with omnidirectional proton fluxes. If the 100 keV ion fluxes near 7 RU are similar to Saturnian ion fluxes at such energies, the Uranian aurora may be maintained by ion precipitation from the radiation belts at nearly the strong diffusion rate. This mechanism predicts comparable aurorae over both magnetic poles of Uranus, in contrast with the Faraday disc dynamo mechanism, which powers an aurora only over the sunlit pole of uranus. If, however, the 100 kev ion fluxes at Uranus are comparable to those at Saturn, any exposed methane ice surfaces on the moons and rings of Uranus would be quickly transformed by ion impacts to a black, carbonaceous polymer.