Thunderstorms bring a hidden glow to forests. The same forces that trigger lightning also make treetops sparkle like Christmas-tree toppers (even if this is barely visible to the human eye).
For nearly a century, scientists have discussed a blue glow known as Saint Elmo’s fire. Thunderstorms create electric fields in the sky. Electric currents can flow from them to some objects below, such as ship masts, triggering them to glow. More recently, researchers wondered if lightning might do something similar to treetops.
Initially triggered in the lab, these glows have now been spotted in nature.
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The idea of whether these glimmers might form at treetops first arose a few years ago, says Patrick McFarland. He’s a meteorologist at Pennsylvania State University in State College. He and William Brune were eating lunch at a picnic table under a tree. McFarland remembers Brune, an atmospheric chemist at the school, gazing up and musing: “Hmm, I wonder if those trees glow under thunders...
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