Very energetic protons in Saturn's radiation belt

Very energetic protons are trapped in the inner Saturnian radiation belt. The University of California at San Diego instrument on Pioneer 11 has definitely identified protons of energy >80 MeV on channel M3 and has tentatively detected protons of energy >600 MeV on channel C3. The spatial distribution of the protons is distinct from that of the trapped electrons, the main difference being that the protons are strongly absorbed by the innermost moons and that the electrons are not. We have estimated the source strength for injecting protons by the decay of cosmic ray albedo neutrons generated in the rings of Saturn. The required proton lifetime is ∼20 years.