Storm clouds have high concentration of gamma rays – 10/02/2024 – Science

Large storm clouds often emit gamma rays continuously, undetectable from the ground, according to two studies published this Wednesday (2), which describe a phenomenon much more common than previously thought.

On Earth, almost 40 thousand storms occur daily, producing more than 8 million lightning strikes per day. But the science behind this phenomenon “remains poorly understood”, according to Joseph Dwyer, a physicist specializing in storms, in an article presenting the two studies in the journal Nature.

In the 1990s, NASA satellites dedicated to detecting high-energy particles from solar storms, exploding stars or black holes recorded gamma ray bursts from Earth. However, other than nuclear power plant reactors, there did not appear to be a terrestrial source for this phenomenon.

Since then, several observations have concluded that they came from thunderstorms and classified them as flashes and gamma-ray bursts, two phenomena invisible to the human eye.

The first, lasting a few minutes over an area of ​​just 20 km, would illuminate the tops of the storm clouds. The second, similar to a shock, would last no more than a thousandth of a second.

“In fact, almost all large storms generate gamma rays continuously and in different ways,” according to Steve Cummer, co-author of the two studies and professor of engineering at Duke University in the United States.

To confirm, an international team of researchers carried out a month-long observation campaign in Florida in 2023.

The study allowed us to fly over, at 20 km altitude, ten storm systems, nine of which provided evidence of a more dynamic spectrum of gamma rays than expected.

“It resembles a giant ‘bubbling pot’ of gamma brightness, both in appearance and behavior,” explains the first study, dedicated to radiation and signed by Martino Marisaldi, professor of physics at the Norwegian University of Bergen.

The storm clouds studied glow with a multitude of gamma-ray emissions that flicker on and off for a few seconds, for hours, and over areas of several thousand square kilometers.

The second study announces the discovery, also thanks to the observation campaign, of a possible “missing link” between flashes and gamma ray explosions.

Signed by Nikolaï Østgaard, professor of space physics at the University of Bergen, this research detected what he describes as oscillating explosions.