Small‐scale magnetic fields on the lunar surface inferred from plasma sheet electrons

Abstract

The origins of the lunar crustal magnetic fields remain unclear although dozens of magnetic field measurements have been conducted on and above the lunar surface. A major obstacle to resolving this problem is the extreme difficulty of determining a surface distribution of small‐scale magnetization. We present a new technique to map small‐scale magnetic fields using nonadiabatic scattering of high‐energy electrons in the terrestrial plasma sheet. Particle tracing, utilizing three‐dimensional lunar magnetic field data synthesized from magnetometer measurements, enables us to separate the contributions to electron motion of small‐ and large‐scale magnetic fields. We map significant kilometer‐scale magnetic fields on the southwestern side of the South Pole‐Aitken basin that are correlated with larger‐scale magnetization. This implies that kilometer‐scale magnetization may be ubiquitous over the lunar surface and related to the large‐scale magnetization.