Discovery of Intrinsic Magnetospheric Ion Behavior at Mars

Abstract Mars lacks a planetary-scale intrinsic magnetosphere, and instead possesses small-scale crustal magnetic fields, creating a distinct class of plasma environments from intrinsic magnetospheres such as that of Earth or Saturn. Here we report the discovery of intrinsic magnetospheric ion behavior at Mars based on the measurements provided by Mars Atmosphere and Volatile EvolutioN mission (MAVEN). We observed wedge-like dispersion structures of H+ exhibiting butterfly-shaped distributions within the Martian crustal fields, a feature previously observed only in intrinsic magnetospheres. These dispersed structures are a result of drift motions that fundamentally resemble those observed in intrinsic magnetospheres. Our findings indicate that the Martian crustal fields have the potential to behave similarly to intrinsic magnetospheres in modifying the ion motions despite their weak strength and large inhomogeneity. This study offers insights into the role of crustal fields in ion escape and the mass-energy transfer between solar wind and Mars.