New Class of Gamma-Ray Flashes Indicate Gamma Glow Reset through Fast Streamer Discharge.

Recent aircraft campaign over the Caribbean region in July 2023, called ALOFT, resulted in several discoveries that significantly improved our understanding of atmospheric gamma-ray phenomena. It was demonstrated that strong convective systems produce strong, long lasting electric fields that generate highly dynamic gamma-ray glow emissions. About 600 individual glows, arranged in tens of glowing episodes were recorded, a certain part of which show abrupt decrease in photon flux due to some electrical discharge leading to reduction of the electric field in the active region. Many of those abruptly reset glows bear a bright terrestrial gamma-ray flash (TGF) at the very apex of the gamma-ray glow. All these TGFs are closely followed by a fast streamer discharge recorded as a positive narrow bipolar event (NBE) in radio and as a strong optical pulse in the 337 nm blue light emission with very little contribution in the 777.4 nm red light emission. This indicates that the +IC leader is not involved in this process, contrary to “conventional” leader-related TGFs usually observed from space. The partial discharge of the active volume and the gamma glow reset is achieved through the fast streamer discharge. The TGFs associated with this gamma glow reset process have very short rise time, short duration peak phase, and low fluence, which makes them undetectable from space and kept them undiscovered until the ALOFT campaign.