Thunderstorms create radiation in Earth's atmosphere

Research from Kyoto University in Japan shows that lightning bolts trigger nuclear reactions in thunderclouds, firing radioactive particles toward its surface.

Thunderstorms create radiation and antimatter in Earth's atmosphere that then rains down on our planet, scientists have found.

New research shows that lightning bolts trigger nuclear fission reactions in thunderclouds, firing radioactive particles toward Earth's surface.

Experts claim the 'fallout' poses no threat to life on our planet as it is no more dangerous than Earth's normal background radiation.

Scroll down for video

Thunderstorms create radiation in Earth's atmosphere that then rains down on our planet, scientists have found. New research shows that lightning bolts trigger nuclear reactions in thunderclouds, firing radioactive particles toward Earth's surface (stock image)

Thunderstorms create radiation in Earth's atmosphere that then rains down on our planet, scientists have found. New research shows that lightning bolts trigger nuclear reactions in thunderclouds, firing radioactive particles toward Earth's surface (stock image)

WHAT THEY FOUND 

Researchers have showed for the first time that radioactive gamma rays produced by lightning react with Earth's atmosphere.

Gamma rays fired off by lightning hit Nitrogen gas in the air, dislodging neutrons - small particles that help to make up the nuclei of atoms.

This reaction leaves unstable Nitrogen atoms floating in the air, which quickly decay.

The unstable atoms release positrons as they break apart - the antimatter equivalent of electrons.

Positrons react with electrons in the air, annihilating both particles and producing gamma radiation, which rains down on Earth.

'Since the radioactive isotopes are short-lived, spatially restricted, and [comprise a] relatively small amount compared to usual background radiative environments, I think there is no health risk from this phenomena,' study lead author Dr Teruaki Enoto said.

Dr Enoto and his team, from Kyoto University in Japan, showed for the first time that radioactive gamma rays produced by lightning react with air in the atmosphere.

This reaction produces radioactive particles called radioisotopes and positrons - the antimatter equivalent of electrons.

This array of radioactive particles has been detected since the 1980s by aircraft, ground-based observatories, and satellites.

But experts had struggled to confirm that it was lightning-induced nuclear reactions that were giving off the neutrons, positrons, and other particles observed. 

'We already knew that thunderclouds and lightning emit gamma rays, and hypothesised that they would react in some way with the nuclei of environmental elements in the atmosphere,' Dr Enoto said.

The team installed gamma-ray detectors along Japan's western coastal area, which the researchers say is ideal for observing powerful lightning and thunderstorms. 

In February, four detectors installed in Kashiwazaki city, Niigata, recorded a large gamma-ray spike immediately after a lightning strike a few hundred meters away. 

When they analysed the data, the scientists found three distinct gamma-ray bursts. 

Gamma (y) rays fired off by lightning (left) hit Nitrogen gas in the air, dislodging a neutron (blue particle). This leaves an unstable Nitrogen isotope (13N), which decays into a carbon isotope (13C), a neutrino and a positron. The positron reacts with electrons in the air, annihilating both particles and producing gamma radiation (arrows right), which rains down on Earth

Gamma (y) rays fired off by lightning (left) hit Nitrogen gas in the air, dislodging a neutron (blue particle). This leaves an unstable Nitrogen isotope (13N), which decays into a carbon isotope (13C), a neutrino and a positron. The positron reacts with electrons in the air, annihilating both particles and producing gamma radiation (arrows right), which rains down on Earth

The first lasted less than one millisecond; 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.

Dr Enoto said: '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.'

The second afterglow was caused by lightning reacting with nitrogen gas in the atmosphere.

Experts claim the radiation caused by lightning storms poses no threat to life on our planet as it is no more dangerous than Earth's normal background radiation

Experts claim the radiation caused by lightning storms poses no threat to life on our planet as it is no more dangerous than Earth's normal background radiation

The gamma rays emitted in lightning have enough energy to knock a neutron - a particle that makes up a chunk of the atom's nucleus - out of nitrogen gas.

Particles in the atmosphere then reabsorb these free-floating neutrons into their nuclei, producing a gamma-ray afterglow - the team's second burst.

The final, prolonged emission was from the breakdown of unstable nitrogen atoms in the atmosphere that were now missing a neutron.

These released positrons, which collided with electrons. When matter and anti-matter meet, they annihilate one another, releasing a large burst of gamma rays.

This final, prolonged gamma-ray detection achieved by the team proves for the first time that lightning strikes cause nuclear reactions.

Earth's background radiation is also caused by cosmic rays fired from the sun, which strike particles in the atmosphere, raining subatomic radiation onto Earth (artist's impression)

Earth's background radiation is also caused by cosmic rays fired from the sun, which strike particles in the atmosphere, raining subatomic radiation onto Earth (artist's impression)

'This ... is a conclusive indication of electron–positron annihilation, and represents unequivocal evidence that photonuclear reactions can be triggered by thunderstorms,' said experimental physicist Dr Leonid Babich from the Russian Federal Nuclear Centre, in a commentary on the research in Nature.

According to Dr Enoto, the findings show there is more going on in thunderstorms than scientists thought.

'Usually people think lightning can interact with electrons in atoms,' he told ScienceAlert.

'The photonuclear reactions indicate that lightning also interacts even with nuclei if gamma rays have sufficiently high energy to knock out neutrons from the nuclei.'

'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?' he said.