Formation of Lunar Swirls

TL;DR

This paper proposes a plasma physics-based mechanism for lunar swirl formation, supported by particle-in-cell simulations that replicate observed features like dark lanes and surface shielding on the Moon.

Contribution

It introduces a self-consistent simulation model demonstrating how mini-magnetospheres can create lunar swirl features through plasma interactions.

Findings

Simulations reproduce sharp dark lane features.

Mini-magnetospheres shield lunar surface from solar wind.

Model aligns with observed plasma parameters.

Abstract

In this paper we show a plausible mechanism that could lead to the formation of the Dark Lanes in Lunar Swirls, and the electromagnetic shielding of the lunar surface that results in the preservation of the white colour of the lunar regolith. We present the results of a fully self-consistent 2 and 3 dimensional particle-in-cell simulations of mini-magnetospheres that form above the lunar surface and show that they are consistent with the formation of `lunar swirls' such as the archetypal formation Reiner Gamma. The simulations show how the microphysics of the deflection/shielding of plasma operates from a kinetic-scale cavity, and show that this interaction leads to a footprint with sharp features that could be the mechanism behind the generation of `dark lanes'. The physics of mini-magnetospheres is described and shown to be controlled by space-charge fields arising due to the magnetized electrons and unmagnetized ions. A comparison between model and observation is shown for a number of key plasma parameters.