First observation of a mini-magnetosphere above a lunar magnetic anomaly using energetic neutral atoms

TL;DR

This paper reports the first imaging of a lunar mini-magnetosphere above a magnetic anomaly using energetic neutral atoms, revealing a new class of magnetic phenomena on airless bodies.

Contribution

It introduces a novel observational technique using backscattered neutral atoms to image mini-magnetospheres on the Moon.

Findings

Mini-magnetosphere is 360 km across at the lunar surface.

A surrounding plasma flux region 300 km thick is observed.

High-energy hydrogen atoms reveal the mini-magnetosphere's structure.

Abstract

The Sub-keV Atom Reflecting Analyzer (SARA) instrument on the Indian Chandrayaan-1 spacecraft has produced for the first time an image of a lunar magnetic anomaly in backscattered hydrogen atoms. The image shows that a partial void of the solar wind, a mini-magnetosphere, is formed above the strong magnetic anomaly near the Crisium antipode. The mini-magnetosphere is 360 km across at the surface and is surrounded by a 300-km-thick region of enhanced plasma flux that results from the solar wind flowing around the mini-magnetosphere. The mini-magnetosphere is visible only in hydrogen atoms with energy exceeding 150 eV. Fluxes with energies below 100 eV do not show corresponding spatial variations. While the high-energy atoms result from the backscattering process, the origin of the low-energy component is puzzling. These observations reveal a new class of objects, mini-magnetospheres, and demonstrate a new observational technique to study airless bodies, imaging in backscattered neutral atoms.