Characterizing Upward Lightning With and Without a Terrestrial Gamma Ray Flash

Academic Article


  • We compare two observations of gamma-rays before, during, and after lightning flashes initiated by upward leaders from a tower during low-altitude winter thunderstorms on the western coast of Honshu, Japan. While the two leaders appear similar, one produced a terrestrial gamma-ray flash (TGF) so bright that it paralyzed the gamma-ray detectors while it was occurring, and could be observed only via the weaker flux of neutrons created in its wake, while the other produced no detectable TGF gamma-rays at all. The ratio between the indirectly derived gamma-ray fluence for the TGF and the 95% confidence gamma-ray upper limit for the gamma-ray quiet flash is a factor of $1\times10^7$. With the only two observations of this type providing such dramatically different results -- a TGF probably as bright as those seen from space and a powerful upper limit -- we recognize that weak, sub-luminous TGFs in this situation are probably not common, and we quantify this conclusion. While the gamma-ray quiet flash appeared to have a faster leader and more powerful initial continuous current pulse than the flash that produced a TGF, the TGF-producing flash occurred during a weak gamma-ray "glow", while the gamma-ray quiet flash did not, implying a higher electric field aloft when the TGF was produced. We suggest that the field in the high-field region approached by a leader may be more important for whether a TGF is produced than the characteristics of the leader itself.
  • Authors

  • Smith, DM
  • Bowers, GS
  • Kamogawa, M
  • Wang, D
  • Ushio, T
  • Ortberg, J
  • Dwyer, Joseph
  • Stock, M
  • Status

    Publication Date

  • October 27, 2018
  • Keywords

  • astro-ph.HE
  • Digital Object Identifier (doi)

    Start Page

  • 11321
  • End Page

  • 11332
  • Volume

  • 123
  • Issue

  • 20