Solar-wind electron precipitation on weakly magnetized bodies: the planet Mercury

TL;DR

This study uses a 3D kinetic plasma model to demonstrate that solar wind electron precipitation on Mercury causes surface ionization and X-ray emissions, providing the first numerical evidence of Mercury's X-ray auroras.

Contribution

First numerical demonstration that solar wind electrons cause ionization and X-ray auroras on Mercury's surface.

Findings

Electron precipitation drives ionization of surface species.

Precipitation induces X-ray emissions from Mercury.

First numerical evidence of Mercury's X-ray auroras.

Abstract

Mercury is the archetype of a weakly magnetized, airless, telluric body immersed in the solar wind. Due to the lack of any substantial atmosphere, the solar wind directly precipitates on Mercury's surface. Using a 3D fully-kinetic self-consistent plasma model, we show for the first time that solar-wind electron precipitation drives (i) efficient ionization of multiple species (H, He, O and Mn) in Mercury's neutral exosphere and (ii) emission of X-rays from the planet's surface. This is the first, independent evidence of X-ray auroras on Mercury using a numerical approach.