Optical emissions associated with terrestrial gamma ray flashes

Wei Xu, Sebastien Celestin, Victor P. Pasko

Research output: Contribution to journalArticlepeer-review

20 Scopus citations


Terrestrial gamma ray flashes (TGFs) are high-energy photon bursts produced by high-energy electrons originating in the Earth's atmosphere through bremsstrahlung processes. In this paper, we present modeling studies on optical emissions resulting from the excitation of air molecules produced by the large population of electrons involved in TGF events based on two possible production mechanisms: relativistic runaway electron avalanches (RREAs) and acceleration of thermal runaway electrons produced by high-potential intracloud lightning leaders. Numerical models developed in this study are first validated through the calculation of fluorescence emissions from air excited by energetic electrons and comparison with available laboratory observations. Detailed discussion of the role of excitation and ionization collisions on the formation of the electron energy distribution is presented. Moreover, using Monte Carlo simulations, we show that electron energy distributions established from the two TGF production mechanisms considered here are inherently different over the full energy range. The strong energy dependence of the capability of electrons to generate excited states responsible for optical emissions from neutral and ionized nitrogen molecules leads to intrinsic differences in optical emissions produced by different mechanisms of TGF production. We also show that TGFs are most likely accompanied by detectable levels of optical emissions and that the distinct optical features are of significant interest for constraining and validating current TGF production models.

Original languageEnglish (US)
Pages (from-to)1355-1370
Number of pages16
JournalJournal of Geophysical Research: Space Physics
Issue number2
StatePublished - Feb 2015

All Science Journal Classification (ASJC) codes

  • Geophysics
  • Space and Planetary Science


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