Combined Juno observations and modeling of th e Jovian auroral electron interaction with the Jovian upper atmosphere

The Juno mission provides a unique opportunity during each perijove pass to sample the downward electron flux at spacecraft altitude while observing far ultraviolet H2 and infrared H3+ emissions at Juno’s magnetic footprint. In addition, the ratio of the H2 spectral band absorbed by hydrocarbons to the unabsorbed portion of the spectrum (FUV color ratio) is often used as a proxy for the depth of the penetration of energetic electrons (relative to the hydrocarbon homopause). The relationship between the color ratio and the electron penetration has been simulated with a Monte Carlo model solving the Boltzmann transport equation. Analysis of concurrent FUV and IR images obtained during the first perijove (PJ1) suggests that the ratio of H3+ radiance to H2 unabsorbed emission is maximal in regions with low FUV color ratio. This result suggests that part of the H3+ column is lost in reactions with methane which converts H3+ into heavier ions. We also examine the observed relationship between the detailed morphology of the ultraviolet structures and of the associated UV color ratio, the total downward electron energy flux and its spectral characteristics.