Radial Diffusion in Jupiter's Magnetosphere

Before the Pioneer 10 and 11 Jupiter flybys, it was suggested that the Jovian radiation belts are populated by strong radial inward diffusion [see, e.g., Birmingham et al., 1974; Coroniti, 1974; Mead, 1972] violating the third adiabatic invariant. Birmingham et al. [1974] and Coroniti [1974] showed that the general features of the Jovian decimetric radiation (DIM) can be explained in terms of a diffusion solution for the energetic particles. Mead [1972], Mead and Hess [1973], and Hess et al. [1973] considered the effects that the Jovian satellites, in particular the moon Io, would have on the radially inward diffusing particles. They showed that unless the diffusion is rapid, few particles would be able to cross the moon's orbit. Practically all authors dealing with diffusion in Jupiter's magnetosphere have concluded that diffusion must be strong, in particular at small values of L (Mcllwain parameter). Data provided by Pioneer 10 and 11 have been analyzed to yield information about radial diffusion. Mogro-Campero [1976], Simpson et al. [1974], and Mogro-Campero and Fillius [1976], for example, use the observed decreases of particle fluxes at the orbits of the moons Amalthea, Io, and Europa to find diffusion coefficients. Their combined results seem to in-