Observations of Ganymede’s variable auroral ovals on leading side derived from HST/STIS

Friday, 19 December 2014
Fabrizio Michele Musacchio1, Joachim Saur1, Lorenz Roth2, Paul D Feldman3, Darrell F Strobel3, Kurt D Retherford2 and Melissa A McGrath4, (1)University of Cologne, Cologne, Germany, (2)Southwest Research Institute San Antonio, San Antonio, TX, United States, (3)Johns Hopkins University, Baltimore, MD, United States, (4)NASA Marshall Space Flight Center, Huntsville, AL, United States
We investigate properties of Ganymede’s FUV auroral ovals using spectral images acquired during two visits in 2010 and 2011 with Hubble’s Space Telescope Imaging Spectrograph (HST/STIS campaign 12244) when Ganymede was at eastern elongation. We analyze the variability of the structure and brightness of the auroral ovals as a function of magnetic latitude. The investigation of the aurora is a diagnostic tool of the various processes, which contribute to Ganymede’s complex magnetic field environment. The variability which we find consists of both, spatial inhomogeneities on the moon disk and temporal variation as a function of Ganymede’s position within the current sheet of Jupiter’s magnetosphere. The comparison of our results with those from previous HST/STIS observations reveals an additional temporal variability as the brightness properties vary for different elongations in different periods.