Termination of Downward‐Oriented Gamma‐Ray Glow by Normal‐Polarity In‐Cloud Discharge Activity

Abstract

A gamma‐ray glow, a minute‐lasting burst of high‐energy photons from a thundercloud, was detected by ground‐based apparatus at Kanazawa University, Japan, in a winter thunderstorm on 18 December 2018. The gamma‐ray glow was quenched by a lightning flash within a brief time window of 40 ms. The lightning flash produced several low‐frequency (LF) E‐change pulses that were temporally coincident with the termination of the gamma‐ray glow, and that were located within 0.5 km from the observation site by the Fast Antenna Lightning Mapping Array. The LF pulses had the same polarity as a positive cloud‐to‐ground current and a normal‐polarity in‐cloud current. Since this polarity is against the upward electric field for producing the gamma‐ray glow (accelerating electrons to the ground), we infer that the glow was terminated by a normal‐polarity in‐cloud discharge activity between a middle negative layer and an upper positive layer.

Negative Excursion of Surface Electric Fields During Gamma‐Ray Glows in Winter Thunderstorms

“…It could suggest that positively charged graupels and/or snow aggregates were falling, and the upward E‐field responsible for the electron acceleration was descending. The same feature was also seen in another glow detected at the same site on 18 December 2018 (Wada, Wu, et al., 2023).…”