From your skin feeling tingly to your hair standing on end, nature gives a few warning signs that lightning is imminent, but not every sign of an electrical discharge is as flashy or easily visible as lightning.
We’ve known about corona discharge for centuries, particularly when it comes to “St. Elmo’s Fire” hovering above tall ships’ masts and the like, but its glowing presence dancing on treetops during storms has been largely understudied, until now.
Meteorologist Dr. Patrick McFarland at Penn State University says those corona discharges have long been theorized as the source for that electric field discrepancy, but had never been directly observed due to how weak they are: “Above the forest canopy, the electric field is much, much stronger than below the forest canopy.”
The basic primer is that a storm overhead separates into two main charge layers, one mainly positive, the other negative. That induces an opposite charge in the ground… and because opposites attract, the ground charge will try to get as close as possible to its skyward counterpart. “It’s going to travel up to the tallest point it can reach,” Dr. McFarland explains, “which in a forest, that tallest point is going to be the tops of trees.”
Of course, occasionally that connection completes to a spectacular, loud, and dangerous effect. There’s often a lot of light competing for your eyes, like the Sun, flashlights, your phone screen… so a key challenge here was filtering out the source from the noise. A new solar-blind ultraviolet camera provided that key, with the team producing the first documented evidence of corona discharge on treetops in a North Carolina forest.
“These coronae were very, very jumpy and sporadic,” he recalls, “moving all over the place, into our field of view and then out of it and then back in… and they were hopping from branch to branch, leaf to leaf.”
Dr. McFarland says the very tips of the leaves and needles showed signs of burning and discoloration in a lab setting, but further study is needed for how much damage may actually be taken here: “I would imagine that trees have somehow adapted to these corona to mitigate their formation or maybe even use their formation as a benefit.”
Another fun consideration lies with those discharges producing “free radicals” like hydroxyl, the atmosphere’s main cleaning agent for improving air quality. It reacts with and removes many chemicals emitted by trees, like the one that gives pine trees their scent, as well as atmospheric methane and CO₂.
It’s also thought these coronae can be found within the storm itself, perhaps on the tips of ice crystals and that, Dr. McFarland says, is just one of several ideas for future endeavors: “These corona could be an even weaker sort of precursor to these streamers that eventually build up and lead to lightning formation.”
Latest Local News | First Alert Weather | Crime | National | 13abc Originals
Copyright 2026 WTVG. All rights reserved.
