Eerie Cosmic-Ray 'Cavity' Found Lurking in Earth-Moon Space

China's Chang'e 4 lander measured a localized decrease in galactic cosmic ray proton flux between Earth and Moon.

The team found about a 20% drop in proton counts when the Moon was in the prenoon sector during certain Parker spiral alignments.

Researchers attribute the dip to interplanetary magnetic field lines connecting the Moon to Earth's magnetic region, creating a temporary GCR 'shadow'.

The proton flux reduction lasts roughly two days during the Moon's transit and was reported in Science Advances.