H2 emissions from the outer planets

Calculations of the H2 electronic band spectrum produced by fluorescence scattering of solar radiation are presented and compared with observations of the ultraviolet spectrum of Jupiter. The calculations demonstrate that the observed spectra are consistent with the suggestion by Yelle et al. (1987) that the bright H2 day-glow of the outer planets is due predominantly to fluorescence of solar radiation. The calculations also demonstrate that large differences between solar scattered and electron excited spectra are evident at high spectral resolution. This fact may be used to observationally determine the relative importance of the two excitation mechanisms.