An Initial Survey of Juno-UVS Auroral Emission Spectra

We present an initial Juno-UVS survey of spectra of the major features of Jupiter’s ultraviolet auroras, which primarily include band emissions of H2 excited by electron impact, and the Lyman series of H arising from electron impact dissociative excitation of H2. The primary difference found in most of the observed spectra is the column of hydrocarbons (mostly methane) overlying the aurora production layer in Jupiter’s atmosphere. This leads to the “color ratio” of the emissions, commonly defined as the ratio of auroral emissions at wavelengths 155-162 nm, where methane is transparent, to those at 125-130 nm, where methane is strongly absorbing. Over the course of the Juno mission, it has been found that the brightness of most auroral features known from previous observations from Earth orbit have a strong dependence on local time. The primary purpose of this survey is to examine if other details in the spectra of these features are likewise correlated with local time, and whether they are also sensitive to other changes, either in the precipitating particles (e.g., the mean electron energy) or in the auroral atmosphere (e.g., the ambient H2 vibrational distribution)