Lightning-induced relativistic electron precipitation from the inner radiation belt

The Earth's radiation belts are maintained by a range of acceleration, loss, and transport processes that produce highly variable electron fluxes. Microbursts—sub-second bursts of energetic electrons precipitating into the atmosphere—are a key loss mechanism, typically observed in the outer belt and driven by whistler-mode chorus waves, but also in the inner belt and slot region when driven by lightning-generated whistlers (LEP). While LEP is commonly observed at 10s–100s of keV and MeV energies have been inferred indirectly from ground VLF measurements, direct in situ resolution of the rapid time evolution has been lacking. Here we present direct observations of lightning-induced precipitation at MeV energies from the inner radiation belt, revealing a coupling between terrestrial lightning and relativistic electron microbursts that links Earth weather to space weather.