Flickering gamma-ray flashes, the missing link between gamma glows and TGFs

• Published in: Nature (London) Vol. 634; no. 8032; pp. 53 - 56
• Main Authors: Østgaard, N., Mezentsev, A., Marisaldi, M., Grove, J. E., Quick, M., Christian, H., Cummer, S., Pazos, M., Pu, Y., Stanley, M., Sarria, D., Lang, T., Schultz, C., Blakeslee, R., Adams, I., Kroodsma, R., Heymsfield, G., Lehtinen, N., Ullaland, K., Yang, S., Qureshi, B. Hasan, Søndergaard, J., Husa, B., Walker, D., Shy, D., Bateman, M., Bitzer, P., Fullekrug, M., Cohen, M., Montanya, J., Younes, C., van der Velde, O., Krehbiel, P., Roncancio, J. A., Lopez, J. A., Urbani, M., Santos, A., Mach, D.
• Format: Journal Article
• Language: English
• Published: London Nature Publishing Group UK 03.10.2024; Nature Publishing Group
• Subjects: 639/766; 639/766/400/1106; Aircraft; Atmospheric electricity; Electrons; Gamma ray flashes; Gamma Rays; Humanities and Social Sciences; Leader currents; Lightning; multidisciplinary; Observatories; Radiation; Science; Science (multidisciplinary); Sensors; Storms; Thunderstorms; Time Factors; El Salvador; Mexico
• ISSN: 0028-0836; 1476-4687; 1476-4687
• DOI: 10.1038/s41586-024-07893-0

Two different hard-radiation phenomena are known to originate from thunderclouds: terrestrial gamma-ray flashes (TGFs) 1 and gamma-ray glows 2 . Both involve an avalanche of electrons accelerated to relativistic energies but are otherwise different. Glows are known to last for one to hundreds of seconds, have moderate intensities and originate from quasi-stationary thundercloud fields 2 – 5 . TGFs exhibit high intensities and have characteristic durations of tens to hundreds of microseconds 6 – 9 . TGFs often show a close association with an emission of strong radio signals 10 – 17 and optical pulses 18 – 21 , which indicates the involvement of lightning leaders in their generation. Here we report unique observations of a different phenomenon, which we call flickering gamma-ray flashes (FGFs). FGFs resemble the usual multi-pulse TGFs 22 – 24 but have more pulses and each pulse has a longer duration than ordinary TGFs. FGF durations span from 20 to 250 ms, which reaches the lower boundary of the gamma-ray glow duration. FGFs are radio and optically silent, which makes them distinct from normal TGFs. An FGF starts as an ordinary gamma-ray glow, then suddenly increases exponentially in intensity and turns into an unstable, ‘flickering’ mode with a sequence of pulses. FGFs could be the missing link between the gamma-ray glows and conventional TGFs, whose absence has been puzzling the atmospheric electricity community for two decades. Flickering gamma-ray flashes associated with terrestrial thunderstorms have been observed, which may be the missing link between gamma-ray glows and TGFs.