On the energy source for diffuse Jovian auroral emissivity

Data from the Energetic Particle Detector on Galileo have been used to investigate whether the radiation belt population can act as a direct energy reservoir for Jovian auroral emissions. Energetic (E > 42 keV) ion distributions in the middle magnetosphere (9 < R-J < 26) yield peak precipitation energy fluxes comparable to a few ergs-cm(-2)-s(-1), which are too weak to produce significant auroral emissivity. Detailed analysis of energetic electrons (15 - 884 keV) indicates the presence of an enhanced population near the loss cone that may provide precipitation energy flux above 10 ergs-cm(-2)-s(-1) over an extended region (10 less than or equal to R-J less than or equal to 25) of the middle magnetosphere. The available precipitation electron energy flux decreases at higher radial distance, falling to values below 1 erg-cm(-2)-s(-1) outside 30 R-J. Additional acceleration mechanisms such as field-aligned currents are required to account for observed auroral intensities at higher L. The precipitation flux values presented here have been calculated under the assumption of strong pitch-angle scattering due to wave-particle interactions in the essentially collisionless middle magnetosphere. Plasma waves with relatively modest amplitude (B-w greater than or equal to 25 pT or E-w greater than or equal to 5 mV/m) are sufficient to induce strong diffusion scattering outside 10 R-J. Such scattering can account for energy deposition over a broad latitude range (Delta lambda greater than or equal to5 degrees) associated with the diffuse Jovian aurora.