Field-Aligned Current Systems at Mercury

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Planet Mercury is the closest orbiting planet around the sun and is therefore embedded inan intensive and highly varying solar wind. The interaction of the solar wind withthe relatively weak interior magnetic field yields a magnetosphere that is similar in shape but much smaller in size to the magnetosphere of the Earth. Hence, multiple models for the magnetic field and current systems that are valid for Earth can be applied to Mercury with certain restraints. One restraint is the apparent lack of a measured Region 2 field-aligned current (R2-FAC) system. In this project, we will address this question, whether the R2-FAC exist at Mercury with our hybrid simulation code A.I.K.E.F. . The current model of the Hermean magnetosphere will be expanded using multiple approaches: 1. Consideration of a heavy ion exosphere (huge ion gyro radii might carry needed closure currents), 2. Inclusion of a multiple shell conductivity model (inner planetary currents are expected), 3. Consideration of a sub-alfvénic solar wind (different current systems). With these approaches, we will improve the existing average magnetosphere model. The model will be compared against reanalyzed in-situ MESSENGER magnetic field data. Knowing about the sources of potential R2-FAC will improve our knowledge about the unique Hermean magnetosphere. Furthermore, the improved Mercury model will greatly aid in the scientific planning of the upcoming ESA-JAXA BepiColombo mission.