Termination of electron acceleration in thundercloud by intracloud/intercloud discharge

和田 有希*; Bowers, G. S.*; 榎戸 輝揚*; 鴨川 仁*; 中村 佳敬*; 森本 健志*; Smith, D.*; 古田 禄大*; 中澤 知洋*; 湯浅 孝行*; et al.

Geophysical Research Letters, 45(11), p.5700 - 5707, 2018/06

https://doi.org/10.1029/2018GL077784

An on-ground observation program for high energy atmospheric phenomena in winter thunderstorms along Japan Sea has been performed via lightning measurements of -ray radiation, atmospheric electric field and low-frequency radio band. On February 11, 2017, the radiation detectors recorded -ray emission lasting for 75 sec. The -ray spectrum extended up to 20 MeV and was reproduced by a cutoff power-law model with a photon index of 1.36, being consistent with a Bremsstrahlung radiation from a thundercloud (as known as a -ray glow). Then the -ray glow was abruptly terminated with a nearby lightning discharge. The low-frequency radio monitors, installed 50 km away from Noto School, recorded intra/inter-cloud discharges spreading over 60km area with a 300 ms duration. The timing of the -ray termination coincided with the moment when a sequence of intra/inter-cloud discharges passed 0.7 km horizontally away from the radiation monitors. The atmospheric electric-field measurement presented that negative charge was located in the cloud base and not neutralized by the lightning discharge. This indicates that the -ray source was located at an higher region than the cloud base.