Japan Geoscience Union Meeting 2019

Presentation information

[E] Oral

M (Multidisciplinary and Interdisciplinary) » M-IS Intersection

[M-IS05] New technologies to monitor thunderstorm and severe weather activities

Tue. May 28, 2019 3:30 PM - 5:00 PM 101 (1F)

convener:Mitsuteru Sato(Department of Cosmoscience, Hokkaido University), Yukihiro Takahashi(Department of Cosmosciences, Graduate School of Science, Hokkaido University), Hisayuki Kubota(Hokkaido University), Kozo Yamashita(Ashikaga University, Department of Engineering.), Chairperson:Yukihiro Takahashi(Hokkaido University), Hisayuki Kubota(Department of Cosmoscience, Hokkaido University)

4:45 PM - 5:00 PM

[MIS05-12] Thundercloud gamma-ray observations at Kashiwazaki aiming at source altitude and beaming measurements and a new trial at Tokyo Skytree in FY2018

★Invited Papers

*Kazuhiro Nakazawa1, Takahiro Matsumoto2, Yuuki Wada2, Alexia Fabiani1, Teruaki Enoto3, Kazufumi Okuda2, Yoshihiro Furuta4, Yuki Aizawa2, Takayuki Yuasa5, Harufumi Tsuchiya4, Mitsuteru Sato6, Kazuo Makishima7 (1.Nagoya University, 2.University of Tokyo, 3.Kyoto University, 4.JAEA, 5.RIKEN, 6.Hokkaido University, 7.Kalvi IPMU, University of Tokyo)

Keywords:Thundercloud, lightning, MeV gamma rays, TGF

MeV gamma rays from lightning and thundercloud reaching the groud are sometimes observed from the winter thunderstorm activities along the coastline of Japan Sea. We, the Gamma-Ray Observation of Winter Thunderclouds (GROWTH) collaboration, are observing such phenomena from 2006 at Kashiwazaki, Niigata prefecture (e.g. Tsuchiya et al. 2007), and recently increasing the number of observation sites, including Ishikawa prefecture (e.g. Wada et al. at M-IS27 session). Since FY2016, we have been operating new detectors at Kashiwazaki dedicated to measure the altitude and beaming of gamma-ray source in thundercloud. Three collimated detectors aiming at different sky regions are deployed. A minute-long gamma-ray emission (or "long-burst") was observed on Jan 26th, 2019 with the system, and we are analyzing the peaking time difference among the three detectors to perform triangulation using the wind speed. Preliminary results suggest the altitude to be lower than ~300 m, but because the emission was relatively weak and photon statistics are not enough, we are estimating the upper-limit of the source altitude and its beaming. Independently, we also started an observation campaign at the 450 m altitude of Tokyo Skytree, aiming at gamma-ray detection from lightning (so called downward TGF) of summer thunderstorm. The tower is one of the locations most frequently hit by lightning. We had three hits on May-Sep. 2018, but no TGF was observed to date, confirming the fact that not all the lightnings are observationally associated with gamma rays. Because our team is observing several downward TGFs from winter thunderstorms (e.g. Enoto et al. 2017), increasing data will enable us to compare the difference among the lightning with and without TGF. The study will be also boosted with the launch of TARANIS satellite in early 2020, dedicated for simultaneous observation of TGF, electrons, optical and radio emission from lightning.