In June 2024, a group of Penn State meteorology and atmospheric science researchers set out on a road trip along the East Coast in a modified 2013 Toyota Sienna. The van was outfitted with a custom-built telescopic weather instrument extending from the roof. Their goal was to track down Florida's near-daily summer thunderstorms and observe a phenomenon that had never been confirmed outside a laboratory.

That phenomenon, known as corona discharge, involves tiny bursts of electricity forming at the tips of leaves. These faint electrical pulses can cause treetops to emit a subtle glow in the ultraviolet (UV) range.…