Magnetometric Resistivity Inversion of Region 1 Field-Aligned Currents in Mercury’s Interior

Mercury hosts a highly dynamic magnetosphere in which energy and momentum can be transported between different regions by field-aligned currents (FACs). The region 1 FAC are generated near the dawnside magnetopause, propagate along magnetic field lines toward the planet, and return toward the dusk magnetospheric flank. In-situ observations have established FACs as a ubiquitous feature of the Hermean magnetosphere. However, in the absence of a substantial ionosphere, the mechanisms by which these currents close remain poorly understood. In this study, we present the analysis results from in-situ MESSENGER magnetic field observations and apply the magnetometric resistivity inversion technique to infer FAC closure pathways above and within the planetary surface and within Mercury’s interior without any pre-assumptions about the conductivity structure. We further show the influence of different inversion side constraints, including solenoidal current continuity and minimum-norm regularization, on the inferred current systems.