Termination of Electron Acceleration in Thundercloud by Intracloud/Intercloud Discharge

Abstract

An on‐ground observation program for high‐energy atmospheric phenomena in winter thunderstorms along the Japan Sea has been performed via measurements of gamma ray radiation, atmospheric electric field, and low‐frequency radio band. On 11 February 2017, the radiation detectors recorded gamma ray emission lasting for 75 s, and then abruptly terminated with a nearby lightning discharge. The gamma ray spectrum extended up to 20 MeV and was reproduced by a cutoff power law model with a photon index of 1.36−0.04+0.03, being consistent with Bremsstrahlung radiation from a thundercloud (known as a gamma‐ray glow or a thunderstorm ground enhancement). The low‐frequency radio monitors, installed ∼50 km away from the gamma ray observation site recorded leader development of an intracloud/intercloud discharge spreading over ∼60 km area with a ∼300‐ms duration. The timing of the gamma ray termination coincided with the moment when the leader development of the intracloud/intercloud discharge passed 0.7 km horizontally away from the radiation monitors. The intracloud/intercloud discharge started ∼15 km away from the gamma ray observation site. Therefore, the glow was terminated by the leader development, while it did not trigger the lightning discharge in the present case.

High Peak‐Current Lightning Discharges Associated With Downward Terrestrial Gamma‐Ray Flashes

“…We have been performing the Gamma‐Ray Observation of Winter Thunderclouds experiment on the north‐west coast of the Sea of Japan, aiming at detecting high‐energy phenomena associated with low‐charge‐center winter thunderstorms (Enoto et al, ; Tsuchiya et al, , , ; Umemoto et al, ; Wada et al, , , , ). In the present paper, data from three observation points in Kanazawa City, Ishikawa Prefecture, Japan, are used: Detector A at Kanazawa Izumigaoka High School (36.538° N, 136.649° E), Detector B at Kanazawa University High School (36.539° N, 136.664° E), and Detector C at Kanazawa University Kakuma Campus (36.546° N, 136.709° E).…”

“…They are sensitive to 0.4–20 MeV photons. Details of the gamma‐ray detectors are described in our previous publications (Enoto et al, ; Wada et al, , ).…”

“…We have been performing the Gamma-Ray Observation of Winter Thunderclouds experiment on the north-west coast of the Sea of Japan, aiming at detecting high-energy phenomena associated with low-charge-center winter thunderstorms (Enoto et al, 2017;Tsuchiya et al, 2007Tsuchiya et al, , 2011Tsuchiya et al, , 2013Umemoto et al, 2016;Wada et al, 2018Wada et al, , 2019cWada et al, , 2019aWada et al, , 2019b Details of the gamma-ray detectors are described in our previous publications (Enoto et al, 2017;Wada et al, 2018Wada et al, , 2019c.…”

“…They have been observed near thunderclouds by airborne experiments (Eack et al, 1996;Kelley et al, 2015;Kochkin et al, 2017;McCarthy & Parks, 1985;Parks et al, 1981) and mountain-top experiments (Alexeenko et al, 2002;Bowers et al, 2019;Chilingarian et al, 2010Chilingarian et al, , 2011Chilingarian et al, , 2016Torii et al, 2009;Tsuchiya et al, 2009Tsuchiya et al, , 2012. Since cloud bases are lower during winter thunderstorms in coastal areas of Japan Sea than summer (Goto & Narita, 1992;Kitagawa & Michimoto, 1994), gamma-ray glows become detectable even by sea level experiments (Kuroda et al, 2016;Torii et al, 2002Torii et al, , 2011Tsuchiya et al, 2007Tsuchiya et al, , 2011Tsuchiya et al, , 2013Wada et al, 2018). They sometimes terminate with lightning discharges (Alexeenko et al, 2002;Chilingarian et al, 2015Chilingarian et al, , 2017Eack et al, 1996, Kelley et al, 2015Kochkin et al, 2017;McCarthy & Parks, 1985;Tsuchiya et al, 2013;Wada et al, 2018), and a part of them also coincided with downward TGFs (Smith et al, 2018;Wada et al, 2019a).…”

“…Since cloud bases are lower during winter thunderstorms in coastal areas of Japan Sea than summer (Goto & Narita, 1992;Kitagawa & Michimoto, 1994), gamma-ray glows become detectable even by sea level experiments (Kuroda et al, 2016;Torii et al, 2002Torii et al, , 2011Tsuchiya et al, 2007Tsuchiya et al, , 2011Tsuchiya et al, , 2013Wada et al, 2018). They sometimes terminate with lightning discharges (Alexeenko et al, 2002;Chilingarian et al, 2015Chilingarian et al, , 2017Eack et al, 1996, Kelley et al, 2015Kochkin et al, 2017;McCarthy & Parks, 1985;Tsuchiya et al, 2013;Wada et al, 2018), and a part of them also coincided with downward TGFs (Smith et al, 2018;Wada et al, 2019a).…”