Wednesday, June 12, 2013

1306.2388 (H. Tsuchiya et al.)

Hardening and termination of long-duration gamma rays detected prior to lightning    [PDF]

H. Tsuchiya, T. Enoto, K. Iwata, S. Yamada, T. Yuasa, T. Kitaguchi, M. Kawaharada, K. Nakazawa, M. Kokubun, H. Kato, M. Okano, T. Tamagawa, K. Makishima
We report the first observation of 3$-$30 MeV prolonged gamma-ray emission that was abruptly terminated by lightning. The gamma-ray detection was made during winter thunderstorms on December 30, 2010 by the Gamma-Ray Observation of Winter THunderclouds (GROWTH) experiment carried out in a coastal area along the Sea of Japan. The gamma-ray flux lasted for less than 3 min, continuously hardening closer to the lightning occurrence. The hardening at energies of 3$-$10 MeV energies was most prominent. The gamma-ray flux abruptly ceased less than 800 ms before the lightning flash that occurred over 5 km away from the experimental site. In addition, we observed a clear difference in the duration of the 3$-$10 MeV gamma rays and those $>$10 MeV, suggesting that the area of $>$10 MeV gamma-ray emission is considerably smaller than that of the lower-energy gamma rays. This work may give a manifestation that a local region emitting prolonged gamma rays connects with a distant region to initiate lightning.
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