A 60-Year Old Mystery About the Moon's Magnetosphere Is Finally Solved

Depiction of the KHI-induced shockwaves and vortices on the lunar surface. Credit - Lai et al.

One particularly well known fact about the Moon is that it doesn’t have much of a magnetosphere to speak of. There’s no blanket to protect it from the solar wind ravaging its surface, blowing away its atmosphere and charging the notoriously dangerous dust particles that make up its regolith. However, scientists have also known for around 60 years that some parts of the moon do experience sudden spikes in a magnetic field - some of which are up to 10 times stronger than the background magnetization. Since their discovery, these “lunar external magnetic enhancements” (LEMEs) have puzzled researchers - what was causing them, and why did they reach so high above the lunar surface that spacecraft could see them? A new paper published in The Astrophysical Journal Letters by Shu-Hua Lai and her colleagues at the National Central University in Taiwan explains for the first time what is likely causing these LEMEs - a novel type of the Kelvin-Helmholtz instability.

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