Multiple Gamma‐Ray Glows and a Downward TGF Observed From Nearby Thunderclouds. Issue 18 (21st September 2021)

• Record Type: Journal Article
• Authors: Hisadomi, S.; Nakazawa, K.; Wada, Y.; Tsuji, Y.; Enoto, T.; Shinoda, T.; Morimoto, T.; Nakamura, Y.; Yuasa, T.; Tsuchiya, H.
• Is Part Of: Journal of geophysical research. Volume 126:Issue 18(2021)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2021-09-21
• Subjects: gamma‐ray glow -- terrestrial gamma‐ray flash -- lightning -- energetic in‐cloud pulse -- thunderstorm; Atmospheric physics -- Periodicals; Geophysics -- Periodicals; 551.5
• DOI: 10.1029/2021JD034543
• Languages: English
• ISSNs: 2169-897X

Abstract

Abstract: Around 17:00 on January 12, 2020 (UTC), radiation detectors installed at two locations with a 1.35 km separation in Kanazawa City, Japan, captured a total of four gamma‐ray enhancements. The first pair was simultaneously observed at the two locations at 17:03 and were abruptly terminated by a lightning discharge. The remaining two enhancements were also nearly simultaneously observed ∼ 3 min later, and one of them was also terminated by another lightning discharge. At the last termination, a downward terrestrial gamma‐ray flash and a negative energetic in‐cloud pulse were observed. Both pairs were associated with thundercloud cells. In the first pair, simultaneous detection in two locations 1.35 km apart suggests either a gamma‐ray glow emerged in‐between and time variability of its intensity were directly observed or there were two (or more) gamma‐ray glows in the cell which reached the two detectors coincidentally. In the latter pair, the peak time in the downwind detector was ∼ 40 s later than that of the upwind detector. If the irradiation region moved with the cell, it would have taken ∼110 s. The discrepancy suggests either the glow moved 2.5 times faster than the cell or there were two (or more) glows in the cell. Also, the fact that the thunderstorm cell hosting the latter glows experienced the lightning discharge ∼ 3 min before suggests that the strong electric field in the cell can develop within a few minutes. Plain Language Summary: Thunderclouds sometime emit gamma rays with a duration of minutes, which are called "gamma‐ray glow". It is bremsstrahlung emission from high‐energy electrons accelerated in the cloud. At around 17:00 (UTC) January 12, 2020, two radiation detectors installed 1.35 km apart in Kanazawa City, Japan, captured a total of four count rate enhancements. The first two disappeared with a lightning discharge, and the last one with another lightning, in this case accompanied by an intense gamma ray flash called a "downward terrestrial gamma‐ray flash" (TGF). The overall behavior is similar to another gamma‐ray glow observed in the same location on January 2018 (e.g. Wada et al. 2019, https://doi.org/10.1038/s42005-019-0168-y ). This is also the third report of gamma‐ray glow termination associated with both lightning discharges and TGFs. However, while the 2018 event can be explained well by assuming that the electron acceleration region moves with the thundercloud cell (monitored by rainfall map) and then terminated by a lightning discharge, the time profiles of the four current events cannot. To explain the behavior of the 2020 data, new models such as electron acceleration region(s) rapidly emerging in a thundercloud cell, and/or multiple electron acceleration regions co‐existing in a single cell, are discussed. Key Points: Four gamma‐ray enhancements were observed at two locations 1.35 km apart along the wind direction, and their time profiles were analyzed The termination of three of them was also recorded. The last one was associated with a downward terrestrial gamma‐ray flash and a negative energetic in‐cloud pulse The acceleration region of gamma‐ray glows in a thundercloud can develop within a few minutes after experiencing a discharge