A quasi-hemispheric model of the Hermean’s magnetic field

We analyse and process magnetic field measurements provided by the MErcury Surface, Space ENvironment, Geochemistry, and Ranging (MESSENGER) mission. The vector magnetic field measurements are modeled with a dedicated regional scheme expanded in space and in time. Compared to the widely used global Spherical Harmonics (SH), the regional approach is here well suited because of the partial coverage of the MESSENGER's data. We confirm that the internal magnetic field of Mercury is mostly axisymmetric with, on average, a magnetic equator shifted northward. We also observe new features in the time dependencies in the model that we tentatively interpret in terms of: 1) induction in Mercury's mantle 2) Currents in the magnetosphere 3) currents in the ionosphere/exosphere 4) fluid flow in Mercury's outer core.