A quantitative description of the source of Jupiter's diffuse aurora

Jupiter's diffuse aurora (E_precip > 10 ergs-cm−2 -s−1-sr−1) result primarily from the atmospheric precipitation of electrons. These energetic particles originate in the magnetosphere and are pitch-angle scattered via resonant interactions with electromagnetic whistler-mode plasma waves. This dissertation presents a study of in-situ measurements of magnetospheric fields and particles at Jupiter. Observations were taken with the Galileo spacecraft, which has been orbiting Jupiter for the last seven years. Detailed analysis of concurrent measurements from the Galileo Energetic Particles Detector, Plasma Wave Subsystem, and Magnetometer shows that energetic electrons (15–527 keV) originating in the middle magnetosphere (15–40 Jovian radii (R_J)) are responsible for diffuse auroral precipitation. Enhancements in electron flux are associated with up to a 100-fold increase in plasma wave power in the extended Io torus region, where wave-particle interactions lead to the isotropization of typically pancaked pitch-angle distributions. Whistler-mode wave intensification occurs from ∼ the lower hybrid frequency, f_LH, to a few tenths of the electron gyrofrequency, Ω₋. Wave amplitudes can approach 100 pT during intense injection periods, in excess of the strong diffusion limit at ∼7 R_J of B_SD ∼ 60 pT. It is expected that wave amplitude exceeds the strong diffusion limit at larger radial distances from Jupiter. It is shown that appreciable Doppler broadening of plasma wave observations occurs for oblique waves. Power spectral densities indicate that wave amplitudes exceed the strong diffusion threshold, and filled loss cones are likely.; Auroral intensifications at Earth have been associated with enhanced particle flux. Wave-particle interactions similar to those identified in this thesis have also been identified at Earth, where they are associated with diffuse auroral emission.