The event began with the approach of two opposing electrical discharges: a downward-propagating leader from a thundercloud and an upward leader emerging from a television transmission tower in Kanazawa, Japan. Just 31 microseconds before their convergence, a burst of gamma radiation—undetectable to the human eye—was emitted, preceding the visible lightning strike.
It was something rarer (and interesting) than ordinary lightning. It was a terrestrial gamma-ray flash, or TGF, a brief burst of radiation a million times more powerful than the flash that would soon follow.
This split-second sequence, reported in a landmark study published in Science Advances, marks the first time that scientists have captured a downward TGF tied with precision to a lightning strike, observed entirely from the ground. And it may reshape how we understand what unfolds inside our planet’s most powerful storms.
A Storm as a Particle Accelerator
Scientists have known about TGFs for decades. First discovered in the 1990s by satellites orbiting Earth, these flashes are cousins to the distant gamma-ray bursts that blaze across the universe during supernovae or the formation of black holes. But TGFs originate from our own atmosphere.
Still, watching one unfold in real time is incredibly rare. “Most TGFs have been detected by satellites, but spaceborne observations can provide limited information,” Yuuki Wada, a researcher at Osaka University and lead author of the study, told Gizmodo.
So Wada’s team built a multi-sensor detection system aimed at the storm clouds over Kanazawa—a region famous for its fierce winter lightning. They deployed radiation detectors, radio frequency sensors, and high-speed optical cameras around two television towers known to attract bolts from the heavens.
Then they waited.
When Lightning Strikes, So Do Gamma Rays
On January 30, 2023, at 01:13 AM local time, lightning struck Tower 1. A downward negative stream of electric charge—called leader—from the clouds met an upward positive leader from the tower tip. At the very instant they neared each other—just before their collision at about 800 to 900 meters above the ground—the TGF burst out.
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“The TGF started when two leaders approached each other,” Wada’s team reported. “An immense number of electrons were produced and accelerated to relativistic energies in a strong and compact electric-field region between the two leaders”.
The burst of gamma rays lasted just 20 microseconds—less than a blink of an eye—but that was all it took. To confirm what they had seen, the researchers used special sensors that can detect very high-energy light. What they found ruled out ordinary X-rays. These rays were far more powerful—strong enough to trigger nuclear reactions in the air, something normally seen only in extreme cosmic events.
After the main flash, the detectors continued to pick up signals for over 80 milliseconds. This “afterglow,” researchers say, is likely caused by neutron emissions from photonuclear reactions—where the gamma rays are energetic enough to break apart atoms like nitrogen and oxygen in the air, generating cascades of nuclear particles.
Cracking a Lightning Mystery
The discovery supports a long-standing idea that’s been hard to prove: that these powerful bursts of radiation come from the early stages of lightning. Before a lightning bolt strikes, leaders reach out from the cloud and the ground. When leaders with opposite charges move toward each other and get close, they can create an extremely strong electric field—strong enough to hurl tiny particles called electrons to speeds approaching the speed of light.
That idea has been floating in atmospheric physics for years. But direct confirmation has been elusive. “The multi-sensor observations performed here are a world-first,” said Harufumi Tsuchiya, senior author of the study. “Although some mysteries remain, this technique has brought us closer to understanding the mechanism of these fascinating radiation bursts.”
Crucially, the TGF occurred just before—not after—the visible lightning. This detail supports the idea that the gamma-ray burst isn’t a byproduct of lightning, but a precursor triggered by the electric field in the milliseconds before the strike.
We Got Extreme Physics at Home
Gamma-ray flashes like this don’t threaten people on the ground. Earth’s thick atmosphere shields us from the energy. But they offer scientists a chance of studying extreme particle physics right here on Earth.
“The ability to study extreme processes such as TGFs originating in lightning allows us to better understand the high-energy processes occurring in Earth’s atmosphere,” said Wada.
And in doing so, they hint at even stranger physics. Some theories suggest that TGFs may even produce antimatter. Others look to exotic processes like relativistic feedback or thermal runaway, where a single electron can set off an avalanche of particle acceleration.
Though the Japanese team’s sensors couldn’t detect antimatter directly, the burst they witnessed supports models in which the leaders’ converging paths focus energy so tightly that the air itself becomes a kind of natural particle accelerator.
Lightning, Rethought
In the public imagination, lightning is already a powerful force, capable of splitting trees and igniting wildfires. But to scientists, this new view reveals something more sublime: a bolt that could tap into the quantum realm, unleashing particles that move at relativistic speeds and trigger reactions that ripple into nuclear physics.
This discovery opens new doors—not only for storm science but for improving lightning protection systems, satellite measurements, and even our grasp of the Earth’s radiation environment.