When Lightning Strikes, Antimatter Spikes

Gamma ray bursts produced during lightning strikes can generate antimatter, Japanese scientists say.

AsianScientist (Dec. 1, 2017) – In a study published in Nature, scientists in Japan have demonstrated that lightning creates the conditions required to produce antimatter.

Particle physicists have pondered for years the imbalance of matter and antimatter in the universe, that is, why matter is commonplace while antimatter is extremely elusive. Antimatter is detectable by the two gamma rays produced every time positrons (the anti-particle of the negatively charged electron) annihilate with nearby matter. Scientists typically search far-away galaxies for antimatter.

In this study, researchers from Japan discovered that gamma rays from lightning react with the air to produce radioisotopes and even positrons.

“We already knew that thunderclouds and lightning emit gamma rays, and we hypothesized that they would react in some way with the nuclei of environmental elements in the atmosphere,” explained study leader Dr. Teruaki Enoto from Kyoto University.

“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,” he added.

Two years later, in February 2017, four detectors installed in Kashiwazaki city recorded a large gamma ray spike immediately after a lightning strike a few hundred meters away. When the researchers analyzed the data, the scientists found three distinct gamma ray bursts. 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,” said Enoto.

The second afterglow was caused by lightning reacting with nitrogen in the atmosphere. The researchers reported that the gamma rays emitted in lightning had 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 the neutron-poor and unstable nitrogen atoms. These released positrons, which subsequently collided with electrons in annihilation events that continued to release gamma rays for almost a minute.

“We have this idea that antimatter is something that only exists in science fiction. Who knew that it could be passing right above our heads on a stormy day?” Enoto said.

The article can be found at: Enoto et al. (2017) Photonuclear Reactions Triggered by Lightning Discharge.


Source: Kyoto University; Photo: Pexels.
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