Recent research led by the University of Bergen reveals that large thunderstorms emit high-energy gamma radiation, a phenomenon more prevalent and intricate than previously understood. This groundbreaking finding was published on October 16, 2024, in the journal Nature.
NASA satellites initially detected high-energy particles from thunderstorms in the 1990s, which were originally designed to observe cosmic events like supernovae. To further investigate, an international team of scientists employed a modified U2 spy plane to fly over these storms and conduct in-situ analysis.
Steve Cummer, a professor at Duke University and co-author of the study, stated, "There are many more phenomena occurring in thunderstorms than we imagined. Essentially, all large thunderstorms generate gamma rays throughout the day in various forms." The study elucidates that the physics behind the generation of these high-energy bursts is well understood.
As thunderstorms develop, swirling air currents interact with water droplets, hail, and ice, creating an electric charge comparable to that generated by rubbing a balloon on a towel. Positive particles accumulate at the storm's summit, while negative ones settle at the base, resulting in an electric field potentially as powerful as 100 million AA batteries.
When charged particles such as electrons encounter this intense field, they accelerate. If they gain sufficient speed and collide with air molecules, they can eject high-energy electrons, triggering a cascading process that can lead to nuclear reactions and the production of gamma rays, antimatter, and other radiation forms.
The study found that gamma radiation is not a rare occurrence; during a month of research flights over large tropical storms south of Florida, the team observed gamma radiation in 9 out of 10 flights. This consistent radiation output is likened to steam escaping from a boiling pot, suggesting a limit to the energy that can accumulate in these storms.
Additionally, the team identified multiple short-duration gamma ray bursts, often coinciding with active lightning discharges, indicating that the electric fields generated by lightning likely enhance the energy of electrons, facilitating high-energy nuclear reactions. They also recorded two previously unseen types of gamma ray bursts: one lasting less than a millisecond and another comprising a rapid sequence of ten individual bursts within a tenth of a second.
While the radiation poses a risk only when in close proximity to its source, Cummer notes that the dangers of turbulence and extreme winds in active storm cores are of greater concern for aircraft.