Thunderstorms Get Wilder: New Gamma-Ray Phenomena Discovered Above the Clouds

Recent findings indicate that gamma-ray emissions from thunderstorms are far more complex and dynamic than previously understood, thanks to observations of new phenomena like Flickering Gamma-Ray Flashes (FGFs).

These flashes, alongside in-depth studies on tropical thundercloud emissions, suggest that our understanding of atmospheric electricity is evolving. This is supported by extensive fieldwork during the ALOFT campaign, which gathered unprecedented data over the Gulf of Mexico and surrounding areas.

Thunderstorm Gamma-Ray Emissions

In a recent issue of Nature, researchers unveiled groundbreaking findings on the gamma-ray emissions from thunderstorms. These results demonstrate that gamma-ray emissions from thunderclouds are significantly more complex, diverse, and dynamic than previously understood. Gaining insight into these phenomena is key to unlocking the mysteries of lightning.

Discovery of Flickering Gamma-Ray Flashes

The study, titled “Flickering Gamma-Ray Flashes, the Missing Link between Gamma Glows and TGFs,” reports unique observations of a novel phenomenon known as Flickering Gamma-Ray Flashes (FGFs).

Historically, only two types of hard radiation phenomena were recognized during thunderstorms: Terrestrial Gamma-ray Flashes (TGFs) and gamma-ray glows. The newly identified FGFs, share similarities with these known phenomena but also exhibit unique traits that set them apart. Notably, FGFs are gamma-ray pulses that occur without any associated optical or radio signals.

The Missing Link Found?

“We think that FGFs could be the missing link between TGFs and gamma-ray glows, whose absence has been puzzling the atmospheric electricity community for two decades,” says lead author and Professor Nikolai Østgaard at the University of Bergen.

Dynamic Gamma-Ray Emissions in Tropical Thunderclouds

In another study presented in this edition of Nature, Marisaldi et al. [2024] focus on the phenomenon referenced above and known as gamma-ray glows. The paper, entitled “Highly dynamic gamma-ray emissions are common in tropical thunderclouds,” shows that contrary to what has been believed until now, tropical thunderclouds over ocean and coastal regions commonly emit gamma rays for hours over areas up to a few thousand square kilometers.

A New Understanding of Gamma-Ray Glows

“The dynamics of gamma-glowing thunderclouds starkly contradicts the former quasi-stationary picture of glows, and resembles that of a huge gamma-glowing boiling pot both in pattern and behavior,” says Professor Martino Marisaldi at the University of Bergen.

The ALOFT Campaign

The groundbreaking results presented by these two studies are based on observations from the ALOFT (Airborne Lightning Observatory for FEGS and TGFs) campaign.

ALOFT, a collaboration between NASA and the University of Bergen, involved flying the NASA ER-2 aircraft from the MacDill Air Force Base, Florida, over tropical thunderstorms around the Gulf of Mexico, Central America, and the Caribbean in the summer of 2023. The payload included lightning detectors, gamma-ray scintillators, and a mix of passive and/ or active microwave sensors. A total of 10 flights were conducted above thunderclouds around Mexico, El Salvador, Nicaragua, and Florida.

The ALOFT campaign was financed by the Research Council of Norway and led by Professor Nikolai Østgaard and Professor Martino Marisaldi from the University of Bergen, Timothy Lang (Marshall Space Flight Center, NASA), and Franzeska Becker (ER-2 Mission Management).

The instrumentation on Board ER-2 during the ALOFT campaign included:

• Gamma-ray detectors UIB-BGO (PI: Nikolai Østgaard, UiB) and iStorm (PI: Eric Grove, NRL)
• An optical instrument named FEGS (PI: Mason Quick, Marshall Space Flight Center, NASA)
• Two electric field sensors known as EFCM (PI: Hugh Christian, University of Alabama, Huntsville) and LIP (PI: Christopher Schultz, Marshall Space Flight Center, NASA)
• Four cloud characterization instruments: AMPR (PI: Timothy Lang, Marshall Flight Center, NASA), CRS and EXRAD (PI: Gerry Heymsfield, Goddard Space Flight Center, NASA), and CoSSIR (PI: Rachael Kroodsma, Goddard Space Flight Center, NASA)

The flight campaign was coordinated with ground-based radio observations managed by a large network of collaborators.

For more on this research:

• NASA’s Retrofitted U2 Spy Plane Reveals Tropical Lightning Storms Are Radioactive
• NASA Uncovers Mysterious Gamma Rays Lighting Up Thunderclouds

References:

“Flickering gamma-ray flashes, the missing link between gamma glows and TGFs” by N. Østgaard, A. Mezentsev, M. Marisaldi, J. E. Grove, M. Quick, H. Christian, S. Cummer, M. Pazos, Y. Pu, M. Stanley, D. Sarria, T. Lang, C. Schultz, R. Blakeslee, I. Adams, R. Kroodsma, G. Heymsfield, N. Lehtinen, K. Ullaland, S. Yang, B. Hasan Qureshi, J. Søndergaard, B. Husa, D. Walker, D. Shy, M. Bateman, P. Bitzer, M. Fullekrug, M. Cohen, J. Montanya, C. Younes, O. van der Velde, P. Krehbiel, J. A. Roncancio, J. A. Lopez, M. Urbani, A. Santos and D. Mach, 2 October 2024, Nature.
DOI: 10.1038/s41586-024-07893-0

“Highly dynamic gamma-ray emissions are common in tropical thunderclouds” by M. Marisaldi, N. Østgaard, A. Mezentsev, T. Lang, J. E. Grove, D. Shy, G. M. Heymsfield, P. Krehbiel, R. J. Thomas, M. Stanley, D. Sarria, C. Schultz, R. Blakeslee, M. G. Quick, H. Christian, I. Adams, R. Kroodsma, N. Lehtinen, K. Ullaland, S. Yang, B. Hasan Qureshi, J. Søndergaard, B. Husa, D. Walker, M. Bateman, D. Mach, S. Cummer, M. Pazos, Y. Pu, P. Bitzer, M. Fullekrug, M. Cohen, J. Montanya, C. Younes, O. van der Velde, J. A. Roncancio, J. A. Lopez, M. Urbani and A. Santos, 2 October 2024, Nature.
DOI: 10.1038/s41586-024-07936-6

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