Scientists Capture Trees Glowing During Thunderstorms

Imagine every tree in a forest quietly glowing during a thunderstorm, putting on an invisible light show that could be cleaning our air.

That's exactly what scientists from Penn State just captured on camera for the first time. After decades of attempts, they finally recorded corona discharges: tiny electrical sparks that shimmer across treetops when thunderstorms pass overhead.

The glow is so faint that human eyes can barely detect it. These sparks emit mostly ultraviolet light, which means they're nearly invisible to us without special equipment.

P.J. McFarland, who led the study, built a custom UV telescope mounted on a research vehicle. The camera detects light between 255 and 273 nanometers, a range that sunlight never reaches thanks to the ozone layer.

The team chased storms from Florida to Pennsylvania, parking near forests and pointing their telescope at treetops. In Pembroke, North Carolina, everything clicked.

As a thunderstorm rolled over a sweetgum tree and a loblolly pine, the camera caught hundreds of tiny UV flashes dancing along the branches. Each flicker lasted anywhere from a fraction of a second to a few seconds, hopping from leaf to leaf as the wind shifted.

The biggest surprise? Every single branch they examined was glowing. Both tree species showed similar activity, and the pattern repeated across four different storms on completely different types of trees.

"It's nearly invisible to the naked eye, but our instruments give rise to a vision of swaths of scintillating corona glowing as thunderstorms pass overhead," McFarland said.

The Ripple Effect

This discovery matters far beyond a pretty light show. The coronas produce massive amounts of hydroxyl radicals, molecules that scrub pollutants and hydrocarbons from forest air.

Forests might be cleaning themselves during storms in ways scientists never accounted for. That could reshape our understanding of air quality in wooded areas.

The electrical activity can also slowly damage leaf tips over many storms, especially in areas where thunderstorms are frequent. The charged particles might even feed energy back into the storms themselves, subtly influencing weather patterns.

Lab experiments with potted spruce and maple trees confirmed the connection. The brighter the UV glow, the more electrical current flows through the plant.

For centuries, we've stood under thunderstorms seeing only rain, lightning, and dark clouds. Now we know the forest canopy has been performing its own light show all along, possibly shaping the air, the trees, and the storms themselves.