An equation governing the combined radial diffusion and stochastic acc
eleration of super-Afvenic ions by magnetohydrodynamic waves in Jupite
r's outer magnetosphere is derived. The formulation is based upon a to
tal energy invariant of the adiabatic transport which applies to an is
otropic distribution undergoing rapid pitch angle scattering by waves.
An analytic solution to the double diffusion equation is obtained and
numerical results are presented for two models of ion injection. The
first model assumes S+ and O+ are injected throughout a broad region o
f space through photoionization of Jupiter's magnetospheric neutral wi
nd and obtain an initial energy corresponding to the local corotation
energy after pickup by the planetary magnetic field. The second model
assumes a monoenergetic distribution of energetic protons is implanted
in the middle magnetosphere by the action of field-aligned potential
drops in Jupiter's auroral ionosphere. For both light and heavy ions t
he injection process creates a seed population of particles which are
further accelerated nonadiabatically by the MHD waves and adiabaticall
y through radial diffusion. A comparison of the theoretical results wi
th a recent data analysis of Voyager low-energy charged particle measu
rements is made with very good agreement thus providing a rigorous qua
ntitative account of and definitive explanation for the high-energy io
n component of Jupiter's magnetosphere.