In the 1990s, NASA satellites designed to detect high-energy particles from celestial events such as supernovae discovered unexpected bursts of high-energy gamma-ray radiation from storms on Earth. Researchers quickly attributed these gamma-ray bursts to thunderstorms, but questions remained about whether this was a common occurrence.

The satellites were not optimized to track Earth’s gamma rays and had to be in the right place at the right time to capture events. Now, thanks to a new approach, a group of scientists have been able to get a clearer picture. The team made some surprising discoveries after retooling NASA’s U2 reconnaissance plane to fly above storms.

Storm produces gamma radiation

In two articles published in the journal NatureExperts have discovered that storms produce gamma radiation much more frequently than previously thought. Additionally, the complex dynamics that drive these radioactive particles have revealed many new mysteries.

“There’s a lot more going on in a storm than we imagine,” said co-author Steve Kammer, an engineering professor at Duke University. “It appears that nearly all major thunderstorms produce gamma rays in some form throughout the day.”

Physics of storm radiation

The physics underlying how storms produce high-energy bursts of gamma rays is not entirely new. During a storm, rising air currents and spinning particles such as water droplets, hail and ice create electrical charges.

These charges separate, positive charges rise to the top of the storm and negative charges fall below, creating an electric field strong enough to equal that of 100 million AA batteries packed together.

If charged particles such as electrons find themselves in this electric field, they accelerate. When they collide with air molecules at high speed, they knock off more electrons, creating a chain reaction that ultimately leads to nuclear reactions. This causes bursts of gamma rays, antimatter and other types of radiation.

Radioactive glow during a storm

But there’s more to the story. Planes flying near the storm detected a faint glow of gamma-ray emission from the clouds; This energy is powerful enough to create gamma rays but lacks the explosive flash seen in more intense gamma ray events. It is like a boiling cauldron producing gamma radiation without full power.

“Several air operations have attempted to find out whether this phenomenon is widespread, but the results have been mixed, and no gamma radiation has been detected in many operations over the United States,” Kammer said. “This project is designed to solve these problems once and for all.”

An ideal place to observe gamma radiation

To solve this mystery, the research team used NASA’s ER-2 high-altitude science aircraft, an upgraded U2 reconnaissance aircraft. This Cold War-era plane flies twice as high as commercial jets and can outlast most storms by nearly three miles. Its speed allowed researchers to identify the most promising storms to study.

“The ER-2 aircraft will be the best platform for observing gamma ray emission from storm clouds,” said Nikolaj Ostgaard, professor of space physics at the University of Bergen in Norway and principal investigator of the project. “Flying at an altitude of 20 km [12,4 милі]”We can fly right above the clouds, as close as possible to the source of the gamma radiation.”

The team didn’t know what to expect. If gamma radiation were rare, they might not see much of it. But if it was widespread, they expected to find a lot. And they were not disappointed.

Radioactive thunderstorms are a common occurrence

In a month-long flight, ER-2 flew over 10 major tropical storms south of Florida and detected gamma radiation in 9 of these storms. Radiation came in more dynamic and diverse forms than previously expected.

“The dynamics of gamma-ray storm clouds are in stark contrast to the earlier quasi-steady radiation model and are more like a giant gamma-ray boiling cauldron in both pattern and behavior,” said Martino Marisaldi, professor of physics and technology. University of Bergen.

Tropical storms are much larger than storms at other latitudes, and the team now believes that more than half of tropical storms are radioactive, with low levels of gamma radiation boiling over like steam from a boiling cauldron. This boiling effect can act as a pressure valve, releasing the storm’s energy before it reaches a full gamma ray burst.

Lightning can cause radiation

But the team also observed several intense short gamma-ray bursts. Some of these were consistent with the types of flashes that occur with lightning discharges first detected by NASA satellites. This suggests that lightning recharges electrons during the storm, triggering nuclear reactions that release gamma radiation.

But interestingly, the other two types of gamma-ray bursts have never been observed before. One type lasts less than a thousandth of a second, while the other consists of a series of about 10 flashes that occur in a tenth of a second.

“These two new types of gamma radiation are what I’m most interested in,” Kammer said. “They do not appear to be associated with the development of lightning strikes.” “They somehow appear spontaneously. There are hints in the data that they may actually be related to the processes that initiate lightning strikes, which is still a mystery to scientists.”

Are these storms dangerous?

For those concerned about the potential dangers of gamma radiation during thunderstorms, Kammer offered some reassurance. The amount of radiation produced is not enough to pose a danger to people on the ground or in the aircraft unless they are very close to the source.

“If you were there, radiation would be the least of your problems. Kammer said planes avoid flying during active storms due to extreme turbulence and wind. “Even knowing what we know now, I’m no more worried about flying than I used to be.”

This study showed how much there is to learn about thunderstorms and the radioactive gamma radiation they produce. With new data available, scientists can’t wait to continue exploring the mysteries of these high-energy storms.