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

木星的卫星“木卫三”是目前所知的太阳系中唯一拥有自生内部磁场的卫星。这个内部磁场在木星的大磁层中产生了一个小磁层。由于木卫三相对于木星的磁化等离子体不断移动，由此产生的力显著地重塑了其微型磁层的磁场环境。此外，木星磁层随时间变化的磁场成分会在木卫三上可能存在的导电地下水海洋中产生二次磁场。我们将开发和应用三维数值模型来描述木卫三的磁场环境，以便更好地理解和解开木卫三附近磁场的相对贡献：木卫三核心产生的发电机场，木卫三外部产生的等离子体场，以及可能存在的海洋和核心中的感应场。我们的模型结果将与伽利略号航天器获得的测量结果进行比较，以便约束单个磁场的贡献。我们工作的另一个重点将是通过哈勃太空望远镜观察到的木卫三极光的形态。木卫三极光卵圆的形态是其磁场环境的诊断。我们的研究结果也将与欧洲航天局计划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.