The electron diffusion coeffcient in Jupiter's magnetosphere

A steady state model of Jupiter's electron radiation belt is developed. The model includes injection from the solar wind, radial diffusion, energy degradation by synchrotron radiation, and absorption at Jupiter's surface. A diffusion coefficient of the form DRR/RJ² = kRm is assumed, and then observed data on synchrotron radiation are used to fit the model. The free parameters determined from this fit are m = 1.95 ± 0.5, k = 1.7 ± 0.5 × 109/s, and μ1 (the magnetic moment of injected particles) = 770 ± 300 MeV/G. The value of m shows quite clearly that the diffusion is not caused by magnetic pumping by a variable solar wind or by a fluctuating convection electric field. The process might be field line exchange driven by atmospheric-ionospheric winds; our diffusion coefficient has roughly the same radial dependence but is considerably smaller in magnitude than the upper bound diffusion coefficients recently suggested for this process by Brice and McDonough (1973) and S. A. Jacques and L. Davis, Jr. (unpublished manuscript, 1972).