Currents in the Martian Ionosphere: Cases Without Strong Crustal Magnetic Fields

Abstract

The Martian ionosphere hosts complex current systems driven both by solar wind interactions and neutral wind dynamo processes. While the global patterns of these current systems have been statistically examined, their detailed structures and orientations remain poorly constrained. Using magnetic field observations from NASA's Mars Atmosphere and Volatile Evolution (MAVEN) spacecraft during the Deep Dip 2 campaign, we resolve the horizontal components of dayside ionospheric currents over regions without strong Crustal Magnetic Fields (CMF). The currents are most prominent between 130 and 150 km altitude, with peak magnitudes of ∼1 μA/m ² , and are oriented counterclockwise from, and roughly perpendicular to, the draped Interplanetary Magnetic Field in the horizontal plane when viewed from above. Theoretically calculated neutral wind‐driven dynamo currents show significant discrepancies from the derived currents, likely reflecting uncertainties in neutral winds and conductivities. In contrast, simulated magnetohydrodynamic (MHD) ionospheric currents, which are purely solar wind‐induced in the model, share similar features with the derived currents. We conclude that, for the four cases examined here, which were sampled in near‐subsolar regions with weak CMF, the derived ionospheric currents are more consistent with a solar wind‐induced origin, whereas neutral wind‐driven dynamo currents may play only a minor role under these conditions.