For the first time, scientists have witnessed lightning triggering nuclear reactions in the atmosphere, confirming a hypothesis dating back almost a century.
It’s long been predicted that high-energy electrons in lightning can produce gamma rays that induce nuclear reactions in thunderclouds, but before now, the phenomenon has never been conclusively observed.
“The photonuclear reaction in the atmosphere has been theoretically expected [to be] triggered by such high energy radiation,” one of the researchers, astrophysicist Teruaki Enoto from Kyoto University in Japan, explained to ScienceAlert.
“Several groups have accumulated signatures of this phenomena, such as signals of either neutrons or positrons, which are the products of this reaction.”
Since the 1980s, scientists have detected these kinds of signals using ground-based observatories, aircraft, and satellites, but before now it was difficult to confirm experimentally that nuclear reactions were yielding the neutrons, positrons, or particles observed.
Here, Enoto and fellow researchers made use of radiation detectors installed at the Kashiwazaki-Kariwa nuclear power station in Niigata, along the coast of the Sea of Japan.
During a thunderstorm in February this year, the team detected “intense radiation” from lightning strikes just off the coast, including a brief gamma ray flash.