The Ultraviolet Spectra of the Jovian Aurora

Abstract

The ultraviolet spectra of molecular hydrogen H₂ due to electron impact excitation are calculated and compared with the high-resolution (0.56 Å) spectra of the Jovian aurora obtained with the Hubble Space Telescope Goddard High-Resolution Spectrograph. All the observed features are reproduced by electron impact excitation emissions of H₂, and the predicted intensities agree well with the observed intensities. Accurate molecular parameters are used, and effects of secondary electrons are included. The auroral emissions are reproduced by energetic electron impact excitation of H₂ with a temperature of 400-600 K. Large temperature gradients occur with respect to altitude within the auroral emission regions. The auroral spectra contain a cascade contribution to the Lyman band emission from high-lying E and F states that are populated by the low-energy secondary electrons produced as the energetic auroral electrons slow down.