Contemporaneous Observations of Jovian Energetic Auroral Electrons and Ultraviolet Emissions by the Juno Spacecraft

Abstract

We present comparisons of precipitating electron flux and auroral brightness measurements made during several Juno transits over Jupiter's auroral regions in both hemispheres. We extract from the ultraviolet spectrograph (UVS) spectral imager H2 emission intensities at locations magnetically conjugate to the spacecraft using the JRM09 model. We use UVS images as close in time as possible to the electron measurements by the Jupiter Energetic Particle Detector Instrument (JEDI) instrument. The upward electron flux generally exceeds the downward component and shows a broadband energy distribution. Auroral intensity is related to total precipitated electron flux and compared with the energy-integrated JEDI flux inside the loss cone. The far ultraviolet color ratio along the spacecraft footprint maps variations of the mean energy of the auroral electron precipitation. A wide diversity of situations has been observed. The intensity of the diffuse emission equatorward of the main oval is generally in fair agreement with the JEDI downward energy flux. The intensity of the ME matches exceeds or remains below the value expected from the JEDI electron energy flux. The polar emission may be more than an order of magnitude brighter than associated with the JEDI electron flux in association with high values of the color ratio. We tentatively explain these observations by the location of the electron energization region relative to Juno's orbit as it transits the auroral region. Current models predict that the extent and the altitude of electron acceleration along the magnetic field lines are consistent with this assumption.