Gamma-ray glows associated with thunderclouds have been observed since the 1980s, however it remains unclear how, and at which thunderstorms gamma-ray glows are generated in dense atmospheres. In this study, we report the first Compton camera imaging of a gamma-ray glow from a winter thundercloud. On 14 January 2022, using two identical Bi4Ge3O12 scintillators in energy range of 0.05–5 MeV, we detected two gamma-ray glows lasting ∼4 min in a mountain area 25 km from the Japan Sea and 410 m above sea level. The same events were also observed by the Compton camera, where the first glow we observed suggested statistically significant (4.0 and 5.9 σ level) signals of two enhanced concentrations in gamma-ray photon images in a range of 0.15–1.5 MeV. These concentrations were most clearly observed in a time window of Δt = 50 s around the peak intensity of the gamma-ray glow.
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