1,1,1,1,2,- 1University of Bergen, Physics and Technology, Bergen, Norway
- 2DTU Space, Denmark
- 3Instituto de Astrofísica de Andalucía (IAA-CSIC), Granada, Spain
In 2023, the Airborne Lightning Observatory for FEGS and TGFs (ALOFT) flight campaign discovered a weaker population of TGFs previously undetected by satellite instruments. These weak TGFs were estimated to have source photons in the range of 10^12 to 10^16 (>100keV) at 15km reference altitude. [Bjørge-Engeland 2024; Fuglestad 2025]
By studying the population of weaker TGFs, it was found that a significant fraction of TGFs are associated with fast streamer discharges occurring in the gamma-ray-glowing portions of the thundercloud. These TGF distinguish themselves from the classical satellite-detected TGFs due to not having a prominent optical pulse in 777.4 nm associated with a lightning leader, having a short (about 1μs) rise time and being accompanied by a strong 337.1 nm optical pulse associated with streamers. Based on these observations, we hypothesize that these TGFs have a different initiation process than the “classical” leader-associated TGFs, and we therefore considered them a new type of TGF. [Mezentsev 2025]
Motivated by these findings, we search for gamma-ray signals associated to blue discharges detected by the Atmosphere-Space Interactions Monitor (ASIM) mission. ASIM offers global coverage and a much larger dataset of lightning discharges than ALOFT, at the price of a lower sensitivity to gamma-ray events. We hypothesize therefore that any gamma-ray signal associated to blue discharges in ASIM can be detected only by stacking gamma-ray data associated to a large number of blue discharges.
In this presentation, we show the results of a stacking analysis of gamma-ray data associated to blue dominated optical discharges detected by ASIM.
References:
I. Bjørge-Engeland et al. Evidence of a New Population of Weak Terrestrial Gamma—Ray Flashes Observed from Aircraft Altitude.
https://doi.org/10.1029/2024GL110395
A. Fuglestad et al. The source brightness distribution of Terrestrial Gamma-ray Flashes from the ALOFT flight campaign.
A. Mezentsev et al. New Class of Gamma-Ray Flashes Indicate Gamma Glow Rest through Fast Streamer Discharge.
https://doi.org/10.5194/egusphere-egu25-15838
How to cite: Fuglestad, A., Marisaldi, M., Mezentsev, A., Sarria, D., Østgaard, N., Neubert, T., and Gordillo-Vázquez, F.: Gamma-ray Stacking Analysis of Streamer Dominated Discharges detected by ASIM, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-16950, https://doi.org/10.5194/egusphere-egu26-16950, 2026.
