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

木星S卫星木卫三是太阳系中唯一已知的具有自生内部磁场的卫星。这个内部磁场在木星S大磁层内产生一个微型磁层。由于木卫三相对于木星S的磁化等离子体不断运动，由此产生的力显著重塑了木卫三微型磁层的磁场环境。此外，木星S磁层的时变磁场分量在木卫三上可能存在的导电次表层水海洋中感应出二次磁场。我们将开发和应用三维数值模型来描述木卫三S的磁场环境，以便更好地了解和解开木卫三S附近对磁场的相对贡献：木卫三核心产生的发电机磁场，木卫三外部产生的等离子体场，以及可能的海洋和核心中的感应场。我们的模型结果将与伽利略航天器获得的测量结果进行比较，以限制单个磁场的贡献。我们工作的另一个重点将是哈勃太空望远镜观测到的木卫三S极光的形态。木卫三S极光椭圆形的形态是其磁场环境的诊断依据。我们的结果也将与欧洲航天局计划中的未来木卫三轨道器直接相关。

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.