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The majority of people learn about lightning and the havoc it wreaks on forests. They do not understand about the weak electrical radiance, called a corona, that is believed to form on tree leaves under thunderstorms. Utilizing an ultraviolet-sensitive instrument, Pennsylvania State University scientists have actually now straight observed and determined this electrical phenomenon on sweetgum, loblolly pine and other tree types under thunderstorms in a number of U.S. states.
Coronae radiance on the ideas of spruce needles, caused by charged metal plates in a lab. Image credit: William Brune.
For as long as thunderstorms have actually rolled throughout the world’s forests, cloud-to-ground lightning has actually commanded attention: splitting trunks, sparking wildfires and briefly turning night into day.
Researchers are now focusing on a far subtler electrical phenomenon that forms on the suggestions of leaves throughout thunderstorms.
Unlike lightning, which superheats the air to 10s of countless degrees, coronae are weak electrical discharges, with temperature levels just somewhat above the surrounding air.
These downplayed triggers produce severe quantities of hydroxyl, the environment’s primary oxidizer, damage tree leaves, and possibly contribute charged particles to the thunderstorm cloud base.
“These things really take place; we’ve seen them; we understand they exist now,” stated Dr. Patrick McFarland, a meteorologist at the Pennsylvania State University.
“To lastly have concrete proof of that … is what I believe is the most enjoyable.”
“In the lab, if you shut off all the lights, close the door and obstruct the windows, you can simply hardly see the coronae. They appear like a blue radiance,” he included.
For their research study, Dr. McFarland and his coworkers established a multi-component mobile instrument efficient in determining coronae on treetops and climatic homes that can affect their development.
The primary element was a 25-cm size telescope that focuses the UV radiation onto a solar-blind UV cam conscious wavelengths in between 255 and 273 nm.
The researchers had the ability to observe coronae on sweetgum and evergreen throughout a thunderstorm in North Carolina.
“Coronae hopped amongst leaves and in some cases followed a branch as it swayed in the wind,” they kept in mind.
The authors made comparable observations on other tree types under 4 other thunderstorms from Florida to Pennsylvania.
“Our observations show that corona shimmer on the swath of trees below a thunderstorm,” they stated.
“These coronae can modify air quality in forests, discreetly damage leaves, and potentially provide charge to overhead thunderstorms.”
The research study was released online February 12 in the journal Geophysical Research Letters
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P.J. McFarland et al2026. Corona Discharges Glow on Trees under Thunderstorms. Geophysical Research Letters 53 (4 ): e2025GL119591; doi: 10.1029/ 2025GL119591
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