Detection of magnetospheric ion drift patterns at Mars

Abstract

Mars lacks a global magnetic field, and instead possesses small-scale crustal magnetic fields, making its magnetic environment fundamentally different from intrinsic magnetospheres like those of Earth or Saturn. Here we report the discovery of magnetospheric ion drift patterns, typical of intrinsic magnetospheres, at Mars using measurements from Mars Atmosphere and Volatile EvolutioN mission. Specifically, we observe wedge-like dispersion structures of hydrogen ions exhibiting butterfly-shaped distributions (pitch angle peaks at 22.5°−45° and 135°−157.5°) within the Martian crustal fields, a feature previously observed only in planetary-scale intrinsic magnetospheres. These dispersed structures are the results of drift motions that fundamentally resemble those observed in intrinsic magnetospheres. Our findings indicate that the Martian magnetosphere embodies an intermediate case where both the unmagnetized and magnetized ion behaviors could be observed because of the wide range of strengths and spatial scales of the crustal magnetic fields around Mars.

Direct Observations of Magnetic Reconnections at the Magnetopause of the Martian Mini‐Magnetosphere

“…It was recently reported that hydrogen ions, which possibly originate from solar wind, exist in the minimagnetosphere (Zhang et al, 2023), although how solar wind enters the mini-magnetosphere has not been determined. When the magnetic field from the crustal field reconnects with the IMF, solar wind can enter the crustal field region along these reconnected magnetic field lines.…”

“…However, this process does not indicate that crustal fields can repel all external plasmas. Wedge-like dispersion structures of hydrogen ions, likely originating from solar wind, are observed within crustal fields (Zhang et al, 2023), indicating that channel(s) exist for solar wind to enter crustal fields. Because the minimagnetopause is the boundary between solar wind and crustal fields on the dayside, it is important for us to investigate the direct interaction at the mini-magnetopause, which is also a direct connection between the solar wind and the mini-magnetosphere.…”