Vibrationally excited H 2 in the upper atmosphere of Saturn

Abstract

We have considered the impact of resonance fluorescense of solar EUV radiation by H 2 on the distribution of the vibrational levels of H 2 in the upper atmosphere of Saturn. This source has not been considered to date. It appears that, for v ≥ 3, this is the most important source, more important than those due to photoelectron induced fluorescence, recombination of molecular ions such as H 3 +, and vibrational excitation of H 2 by photoelectron impact. Based on the Voyager limb observations of H 2 band emission we estimate that some of the higher vibrational levels may have effective temperatures ∼ 3500 K. Such high vibrational densities may have an impact on ionospheric densities.