Galileo orbiter ultraviolet observations of Jupiter aurora

Abstract

In 1996 during the first four orbits of the satellite tour the Galileo ultraviolet spectrometer (UVS) (1130-4320 Å) and extreme ultraviolet spectrometer (EUVS) (540-1280 Å) performed near-simultaneous observations of the Jupiter aurora in both the north and south polar regions. These observations are modeled to provide the absolute surface brightness of the aurora from the H2 Rydberg Systems (B, B′, B″, C, D, D′ → X band systems). The spectral distribution and brightness of the EUV aurora are sensitive to H2 abundance, H2 temperature, CH4 abundance. Analysis of the emission spectra indicates that the EUV aurora (800-1200 Å) are produced over a range of altitudes corresponding to slant column abundances of H2 from 1016 to 1020 cm-2 or greater. The UVS spectra of the far ultraviolet (FUV) from 1130 to 1700 Å are optically thin in H2, but highly sensitive to the CH4 column abundance and to the secondary electron energy distribution. The slant column abundance of CH4 absorbers found from models of the FUV spectra varied in the range 0 -10 × 1016 cm-2, indicating the presence of both high altitude aurora, at or above the homopause, deep aurora. The FUV spectra show C2H2 absorption bands near 1520 Å. The surface brightness of the aurora from the H2 Rydberg Systems ranged from 100 to 600 kR and of H Lyman α was 60 to 130 kR for a 2000 km wide oval. The total power input to the atmosphere from particle deposition is estimated to be ∼ 1 × 1014 W. Copyright 1998 by the American Geophysical Union.