Detection of high-energy gamma rays from winter thunderclouds.
A report is made on a comprehensive observation of a burstlike gamma-ray emission from thunderclouds on the Sea of Japan, during strong thunderstorms on 6 January 2007. The detected emission, lasting for approximately 40 sec, preceded cloud-to-ground lightning discharges. The burst spectrum, extending to 10 MeV, can be interpreted as consisting of bremsstrahlung photons originating from relativistic electrons. This ground-based observation provides the first clear evidence that strong electric fields in thunderclouds can continuously accelerate electrons beyond 10 MeV prior to lightning discharges.
Tsuchiya
H
H
Cosmic Radiation Laboratory, Riken, 2-1, Hirosawa, Wako, Saitama 351-0198, Japan.
Enoto
T
T
Yamada
S
S
Yuasa
T
T
Kawaharada
M
M
Kitaguchi
T
T
Kokubun
M
M
Kato
H
H
Okano
M
M
Nakamura
S
S
Makishima
K
K