Lightning Strikes Produce Antimatter Particles in Earth’s Atmosphere

Scientists from Japan and Singapore report in the November 23 issue of the journal Nature that they observed positron (antimatter counterpart of the electron) and neutron signals after lightning.

Enoto et al describe how gamma rays from lightning react with the air to produce radioisotopes and even positrons. Image credit: Teruaki Enoto, Kyoto University.

“We already knew that thunderclouds and lightning emit gamma rays, and hypothesized that they would react in some way with the nuclei of environmental elements in the atmosphere,” said Kyoto University scientist Dr. Teruaki Enoto, lead author of the paper.

“In winter, Japan’s western coastal area is ideal for observing powerful lightning and thunderstorms. So, in 2015 we started building a series of small gamma-ray detectors, and placed them in various locations along the coast.”

During a thunderstorm on February 6, 2017 in Japan, the team’s detectors installed in Kashiwazaki city, Niigata, recorded a gamma-ray flash with a duration of less than one millisecond immediately after a lightning strike a few hundred feet away.

“It was the moment we realized we’re seeing a new, hidden face of lightning,” the researchers said.

“When we analyzed the data, we found three distinct gamma-ray bursts,” they added.

“The first was less than one millisecond in duration; the second was a gamma-ray afterglow that decayed over several dozens of milliseconds; and finally there was a prolonged emission lasting about one minute.”

“We could tell that the first burst was from the lightning strike. Through our analysis and calculations, we eventually determined the origins of the second and third emissions as well,” Dr. Enoto said.

“The second afterglow, for example, was caused by lightning reacting with nitrogen in the atmosphere.”

“The gamma rays emitted in lightning have enough energy to knock a neutron out of atmospheric nitrogen, and it was the reabsorption of this neutron by particles in the atmosphere that produced the gamma-ray afterglow.”

“The final, prolonged emission was from the breakdown of now neutron-poor and unstable nitrogen atoms. These released positrons, which subsequently collided with electrons in annihilation events releasing gamma rays.”

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Teruaki Enoto et al. 2017. Photonuclear reactions triggered by lightning discharge. Nature 551: 481-484; doi: 10.1038/nature24630