Every Tree in Every Forest Has Been Doing This During Storms. We Just Couldn't See It.

Thunderstorms pass over forests constantly. What nobody knew, until now, is that the trees are quietly glowing back.

A Penn State research team that follows thunderstorms in a minivan caught faint electrical glimmers rippling through the treetops — something we've never observed in nature before now. The phenomenon, known as corona discharge, had been theorized for decades but had only ever been produced artificially. Out in the wild, it showed up as faint UV flickers at the very tips of leaves. The paper ran in Geophysical Research Letters in February.

Here's how it works. During a storm, clouds build up strong negative charges that attract the opposite positive charge from the ground below. That charge rises up through the trees to the highest point, causing an electric field at the tiny, hair-like tips of leaves intense enough to produce a weak corona glow in both visible and UV light.

The hypothesis was nearly as old as the postwar era. Researchers had been predicting this since the 1950s, but no one had ever caught it happening in an actual forest. The team built a custom Corona Observing Telescope System — a Newtonian telescope feeding into a UV camera that filters out sunlight entirely — mounted it on the van and drove the East Coast looking for a storm that would cooperate. They ended up in a parking lot at the University of North Carolina at Pembroke, training their instruments on a sweetgum tree about 30 meters (100 feet) away. The thunderstorm lasted nearly two hours, long enough to also capture corona on a nearby loblolly pine as it weakened.

The implications reach beyond the light show. The coronae should produce hydroxyl radicals, sometimes called the atmosphere's detergent because they destroy methane and carbon monoxide. They can also produce hazes from interactions with volatile organic compounds emitted by trees. The amount of hydroxyl produced during a single storm is too small to affect global climate, but could influence air quality in the region surrounding a forest canopy.

Whether all this crackling electricity damages trees remains unclear. Previous lab work showed leaf tips get visibly burnt after only seconds of corona-level voltages. But "trees are incredibly resilient," says forest ecologist Evan Gora, and they likely have adaptations for it.

Every forest. Every storm. 859 corona events recorded on a single sweetgum tree in one two-hour window, and that's with instruments only sensitive enough to catch the strongest ones.

Read the full story at ScienceDaily, April 21, 2026

Hot Take: Scientists spent 70 years theorizing that forests glow with electricity during thunderstorms, and the thing that finally cracked it open was a grad student, a distinguished professor, a homemade UV telescope, and a 2013 Toyota Sienna — which is either a triumph of low-budget field science or the most relatable research methodology in atmospheric physics.