Investigations of Ganymede´s Magnetic Field Environment with new Hubble Space Telescope Observations and Galileo Spacecraft Measurements

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Jupiter s satellite Ganymede is the only known satellite in our solar system which possesses a self-generated internal magnetic field. This internal field generates a mini-magnetosphere within Jupiter s large magnetosphere. As Ganymede is constantly moving relative to Jupiter s magnetized plasma, the resulting forces significantly reshape the magnetic field environment of its mini-magnetosphere. Additionally, time varying magnetic field components of Jupiter s magnetosphere induce secondary magnetic fields in a possible electrolytically conductive subsurface water ocean on Ganymede. We will develop and apply three-dimensional numerical models to describe Ganymede s magnetic field environment in order to better understand and disentangle the relative contributions to the magnetic field in Ganymede s vicinity: The dynamo field generated in the core of Ganymede, the plasma fields generated outside of Ganymede, and the induced fields in the possible ocean and also in the core. Our model results will be compared with measurements obtained by the Galileo spacecraft in order to constrain the individual magnetic field contributions. Another focus of our work will be on the morphology of Ganymede s aurora observed by the Hubble Space Telescope. The morphology of Ganymede s auroral oval is diagnostic of its magnetic field environment. Our results will also be directly relevant for a planned future Ganymede orbiter by the European Space Agency.