Alternating North‐South Brightness Ratio of Ganymede's Auroral Ovals: Hubble Space Telescope Observations Around the Juno PJ34 Flyby

We report results of Hubble Space Telescope observations from Ganymede's orbitally trailing side which were taken around the flyby Juno spacecraft on June 7, 2021. find that northern and southern auroral ovals alternate in brightness such oval facing Jupiter's magnetospheric plasma sheet is brighter than other one. This suggests generator powers aurora momentum Jovian north south magnetosphere. Magnetic coupling Ganymede to above below moon causes asymmetric magnetic stresses electromagnetic energy fluxes ultimately powering acceleration process. No clear statistically significant time variability emission short scales 100s could be resolved. show electron several tens mW m$^{-2}$ are required for its OI 1356 \AA$\;$ making a very poor emitter.