Thunderstorms are a 'boiling pot' of gamma rays, scientists find

Big thunderstorms continuously emit gamma rays that are undetectable from the ground, two studies said on Wednesday, upending what was previously thought -- and potentially pointing towards a clue in the mystery of how lightning is sparked.

Despite the fact that 40,000 thunderstorms generate more than eight million lightning strikes above our heads every day, they "remain poorly understood", physicist Joseph Dwyer said in an analysis of the new research in the journal Nature.

Normally when people think of gamma rays -- bursts of an incredibly high-energy form of light -- they are coming from out of this world, such as solar flares, exploding stars or black holes.

However in the 1990s, NASA satellites tasked with hunting down high-energy particles from such cosmic sources detected gamma rays coming from Earth.

Other than inside nuclear reactors, nothing on our planet had been thought capable of generating gamma rays.

Since then, two different types of gamma rays have been observed inside thunderstorms -- both invisible to the naked eye.

Gamma-ray glows can last for a few minutes over a region roughly 20 kilometres (12 miles) wide, while more powerful "flashes" last less than a millisecond.

"As it turns out, essentially all big thunderstorms generate gamma rays all day long in many different forms," Steven Cummer, a researcher at Duke University and a co-author of one of the studies, said in a statement. To find out more about what is happening inside thunderstorms, the international team of researchers used an NASA ER-2 airplane.