A research group at Kyoto University and others has found that lightning causes a nuclear reaction (photonuclear reaction) in the atmosphere.
In recent years, it has been pointed out that lightning and thunderclouds act as natural accelerators in nature and can accelerate electrons to near the speed of light.Recently, it has become possible to observe high-energy gamma rays emitted when accelerated electrons collide with atmospheric molecules, and a phenomenon called "long burst" has been discovered in which gamma rays fall on the ground for several minutes as thunderclouds pass. Was done.On the other hand, apart from the "long burst", a mysterious sudden phenomenon called "short burst", in which strong gamma rays arrive in a short time of 1 second or less, was also discovered, but the details were unknown.
In this study, a radiation detector installed on the ground detected a burst of intense gamma rays at the same time as a lightning strike that occurred in Kashiwazaki City, Niigata Prefecture on February 2017, 2 (short burst).About 6 seconds later, as the lightning cloud passed over the detector, it detected pair annihilation gamma rays from positrons (antimatter of electrons).
According to the announcement, short bursts are gamma rays emitted by the gamma rays associated with lightning causing a photonuclear reaction with nitrogen in the atmosphere and the resulting neutrons being absorbed by the nuclei in the atmosphere and on the surface of the earth. ..Then, in the pair annihilation gamma ray detected with a delay of 35 seconds, the radioactive isotope of nitrogen generated by the photonuclear reaction gradually undergoes beta-plus decay, and the positrons emitted at that time pair annihilate with the electrons in the atmosphere. It is said that it is a gamma ray emitted by doing so.
In other words, the detected short burst and annihilation gamma rays are clear evidence of the photonuclear reaction caused by lightning.This will bring a "nuclear" perspective to future research on lightning, and is expected to open up observation methods using positrons and neutrons.
Paper information:[Nature] Photon clear reactions triggered by lightning discharge
