Though scientists have long understood how lightning strikes, the precise atmospheric events that trigger it within thunderclouds remained a perplexing mystery.
Though scientists have long understood how lightning strikes, the precise atmospheric events that trigger it within thunderclouds remained a perplexing mystery. The mystery may be solved, thanks to a team of researchers led by Victor Pasko, professor of electrical engineering in the Penn State School of Electrical Engineering and Computer Science, that has revealed the powerful chain reaction that triggers lightning.
In the study published today (July 28) in the Journal of Geophysical Research, the authors described how they determined strong electric fields in thunderclouds accelerate electrons that crash into molecules like nitrogen and oxygen, producing X-rays and initiating a deluge of additional electrons and high-energy photons — the perfect storm from which lightning bolts are born.
“Our findings provide the first precise, quantitative explanation for how lightning initiates in nature," Pasko said. "It connects the dots between X-rays, electric fields and the physics of electron avalanches."
The team used mathematical modeling to confirm and explain field observations of photoelectric phenomena in Earth’s atmosphere — when relativistic energy electrons, which are seeded by cosmic rays entering the atmosphere from outer space, multiply in thunderstorm electric fields and emit brief high-energy photon bursts. This phenomenon, known as a terrestrial gamma-ray flash, comprises the invisible, naturally occurring bursts of X-rays and accompanying radio emissions.
Read more at Penn State
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