Near equality of ion phase space densities at earth, Jupiter, and Saturn
Energetic-ion phase-space density profiles are strikingly similar in the inner magnetospheres of earth, Jupiter, and Saturn for ions of first adiabatic invariant near 100 MeV/G and small mirror latitudes. Losses occur inside L approximately equal to 7 for Jupiter and Saturn and inside L approximately equal to 5 at earth. At these L values there exist steep plasma-density gradients at all three planets, associated with the Io plasma torus at Jupiter, the Rhea-Dione-Tethys torus at Saturn, and the plasmasphere at earth. Measurements of ion flux-tube contents at Jupiter and Saturn by the low-energy charged-particle experiment show that these are similar (for O ions at L = 5-9) to those at earth (for protons at L = 2-6). Furthermore, the thermal-ion flux-tube contents from Voyager plasma-science data at Jupiter and Saturn are also very nearly equal, and again similar to those at earth, differing by less than a factor of 3 at the respective L values. The near equality of energetic and thermal ion flux-tube contents at earth, Jupiter, and Saturn suggests the possibility of strong physical analogies in the interaction between plasma and energetic particles at the plasma tori/plasma sheets of Jupiter and Saturn and the plasmasphere of earth.