Intermittent Electron-Only Reconnection at Lunar Mini-Magnetospheres

TL;DR

This study uses high-resolution kinetic simulations to reveal intermittent electron-only magnetic reconnection at lunar magnetic anomalies, affecting solar wind interactions and proton reflection.

Contribution

It demonstrates the occurrence of bursty electron-only reconnection in lunar mini-magnetospheres, a novel insight into lunar space weather phenomena.

Findings

Periodic formation and ejection of magnetic islands.

Enhanced reflected protons during reconnection events.

Modification of magnetic pressure and electric fields by islands.

Abstract

Lunar crustal magnetic anomalies (LCMA) are sub-ion-gyroradius structures that have been shown to stand off the solar wind (SW) plasma from the Moon's surface, forming shock-like discontinuities and reflecting incident SW protons. In this letter, the results of high-resolution, two-dimensional fully kinetic simulations show a bursty electron-only magnetic reconnection in the SW-LCMA interaction region, characterized by the quasi-periodic formation and ejection of magnetic islands and strong parallel electron flows along the X-point separator lines. The islands are observed to modify the magnetic pressure pile-up and Hall electric field above the LCMA, leading to sharp increases in reflected protons that drive electromagnetic fluctuations downstream and short distances upstream in the SW.