Scientists Film Trees Glowing With Electricity During Thunderstorms

Hidden Light Show in Forest Canopies

When thunderstorms roll through forests, an extraordinary phenomenon occurs that has remained invisible to human eyes for nearly a century. Scientists have long suspected that treetops emit tiny electrical discharges during storms, causing the canopy to glow in ultraviolet light, but for more than 70 years these corona discharges had never been documented outside laboratory settings. Now, researchers from Penn State have finally captured this elusive spectacle on camera, revealing a hidden electrical light show that transforms every forest into something resembling the glowing trees of Pandora from Avatar.

In June 2024, a team of meteorology experts embarked on an ambitious road trip along the East Coast in a converted 2013 Toyota Sienna, equipped with a custom-built telescopic weather instrument protruding from the roof. Their mission was to document what had only existed in scientific theory: the natural occurrence of corona discharges in wild forests during active thunderstorms.

The breakthrough came in North Carolina, where the researchers set up their equipment in a university parking lot and aimed their instruments at a sweetgum tree about 100 feet away during a thunderstorm that persisted for nearly two hours. Using their specialized Corona Observing Telescope System, they captured 859 individual corona events on the sweetgum tree and 93 on a nearby loblolly pine.

The Science Behind Nature's Electric Display

During thunderstorms, storm clouds become highly negatively charged, which induces an opposite positive charge in the ground below, and because opposite charges attract, the ground's charge seeks to close the gap with the cloud by climbing to leaf tips via trees' electrically conductive trunks and branches. At the leaf tips, these charges concentrate and create a strong, localized electric field that excites and ionizes nearby air molecules, creating a plasma that emits light when the molecules relax or recombine—producing a brief, shimmering corona.

To observe this phenomenon outdoors, the team created a specialized Newtonian telescope connected to a UV-sensitive camera that blocks solar UV wavelengths, leaving only corona, lightning, and fire as detectable light sources. In nature, ambient light drowns out the corona glow, making it invisible to cameras and the human eye at visible wavelengths. The corona events ranged from brief flashes lasting fractions of a second to sustained glows persisting for more than three seconds.

The electrical discharges appeared to jump quickly between leaf tips on different branches, suggesting that "hopping" is a fundamental characteristic of coronae, potentially due to shifting electric fields or electrical charges taking different paths up trees. This suggests that whenever a thunderstorm rolls over a forest, basically every treetop underneath it is quietly shimmering with these little sparks, creating "swaths of scintillating corona glowing as thunderstorms pass overhead."

Implications for Forest Health and Air Quality

The discovery has implications beyond confirming the existence of coronae in nature, as the flashes produce large amounts of molecules that can react with other compounds to form haze and smog, potentially helping scientists better understand how thunderstorms affect forest air quality. Previous Penn State research has shown that corona-related processes can boost production of hydroxyl radicals near treetops during storms—molecules that drive atmospheric "cleanup" reactions.

However, the phenomenon may come with costs: laboratory experiments show that coronae cause leaf tips to burn within seconds, and researchers speculate that in nature, repeated exposure could severely harm leaves, potentially leading to sun damage and dehydration. The authors note that leaf tips can show visible damage under electrical stress, and they speculate that repeated exposure across many storms might subtly shape canopy health and perhaps even long-term evolutionary pressures on leaf form and protective coatings.

Future Research and Unanswered Questions

While researchers have confirmed the phenomenon, significant questions remain: Are trees harmed during this process, or do they benefit in some way? Have they evolved to withstand it? Does the atmospheric cleansing have a benefit to the forest? The researchers are beginning collaborations with tree ecologists and biologists to answer these questions, blazing new paths of discovery into the natural world.

If humans could see these coronae in nature, the phenomenon would create "a pretty cool light show," as if thousands of fireflies were dancing on treetops—a hidden electrical ballet that occurs whenever thunderstorms pass through forests. This groundbreaking research opens an entirely new window into understanding the complex electrical relationship between Earth's atmosphere and its forests, revealing that even in our well-studied world, nature still holds spectacular secrets waiting to be discovered.