The Jovian Aurora: Implications of Multiwavelength Auroral Spectra for Auroral Particle Identity and Auroral Microphysics

Remote sensing of Jupiter's aurora from x-ray to radio wavelengths has revealed much about the nature of the jovian aurora and about the impact of ionosphere-magnetosphere coupling on Jupiter's upper atmosphere. Both energetic heavy ions and electrons energized in the outer magnetosphere contribute to the auroral excitation, as indicated by the combination of x-ray and ultraviolet observations. Imaging with the HST in the ultraviolet and with the IRTF at infrared wavelengths reveals several distinct regions of interaction: 1) a dusk sector where turbulent auroral patterns extend well into the polar cap; 2) a morning sector generally characterized by a single spatially confined auroral arc originating in the outer magnetosphere of Jupiter; 3) diffuse emissions associated with the Io plasma torus; and 4) a distinct region associated with the Io Flux Tube footprint. Ultraviolet spectroscopy has provided important information about the thermal structure of the upper atmosphere and altitude distribution of the auroral particle energy deposition, while Lyman alpha line profiles offer clues to the nature of thermospheric dynamical effects. Galileo observations at visible wavelengths on the nightside have provided a new view of the jovian aurora with unprecedented spatial information. Infrared observations have added much to the understanding of thermal structure and morphology and may hold the key to understanding the role of Joule heating. Radio observations imply that energetic particle precipitation extends to low latitudes, a result that has been corroborated at x-ray wavelengths. Multispectral observations of jovian auroral emissions will be discussed within a theoretical/modeling framework that serves to provide some insight into magnetosphere-ionosphere coupling and its effect on the upper atmosphere. Particular emphasis will be placed on the use of auroral spectra to identify incident energetic particles and their energy spectra as a means of elucidating the microphysics of auroral processes.