Abstract
A steady-state model is constructed to describe the inward diffusion of energetic Jovian radiation belt ions that is driven by the outward interchange diffusion of cool ions derived from the satellite Io. A new explicit form for the height-integrated Pedersen ionospheric conductivity is derived incorporating ion precipitation from the Jovian radiation belt. The normalized loss rate for the energetic ions is assumed to take on a spatially-peaked form consistent with recent observations and theoretical expectations. We isolate the effects of the spatial variation in conductivity by omitting the pressure gradient of the radiation belt population. In order to construct solutions we apply the conditions necessary for the auroral-zone conductivity to maximize at a specified location within the lo plasma torus. The model solutions for the energetic (E ∗ > 100 keV) radiation belt ion density agree adequately with reported observations though since the latter densities are unavailable in absolute units only a relative comparison can be made. Solutions are also obtained corresponding to the unobserved lower energy (10keV < E ∗ < 100 keV) ions that are expected to dominate the auroral energy input, but the neglect of the impoundment pressure gradient may not be justified in all cases. For all realistic solutions the Iogenic ion density gradient over the Io plasma “ramp” is relatively insensitive to the model parameters and is typically less than about one half of the value originally calculated from the Voyager 1 observations; this is consistent with a recent revision of the plasma data.
Published Version
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