DatasetDetermining a lower limit of luminosity for the first satellite observation of a reverse beam terrestrial gamma-ray flash associated with a cloud to ground lightning leaderChaffin, Jeffrey; Pu, Yunjiao; Smith, David; Cummer, Steve; Splitt, Mike; for_Particle_Physics, Santa_Cruz Institute{"Abstract":["We provide an updated analysis of the gamma-ray signature of a terrestrial\n gamma ray flash (TGF) detected by the Fermi Gamma-ray Burst Monitor first\n reported by Pu et al. 2020. A TGF produced 3 ms prior to a negative\n cloud-to-ground return stroke was close to simultaneous with an isolated\n low frequency radio pulse during the leader’s propagation, with a polarity\n indicating downward moving negative charge. In prior observations this\n ‘slow’ low frequency signal has been strongly correlated with upward\n (opposite polarity) directed TGF events [Pu et al. 2019; Cummer et al.\n 2011]  leading the authors to conclude that the Fermi gamma ray\n observation is actually the result of a reverse positron beam generating\n upward directed gamma rays. We investigate the feasibility of this\n scenario and determine a lower limit on the luminosity of the downward TGF\n from the perspective of gamma-ray timing uncertainties, TGF Monte Carlo\n simulations, and meteorological analysis of a model storm cell and its\n possible charge structure altitudes. We determined the most likely source\n altitude of the reverse beam TGF to be 7.5 km +/- 2.6 km, just below an\n estimated negative charge center at 8 km. At that altitude the Monte Carlo\n simulations indicate a lower luminosity limit of 2 x 10^18 photons above 1\n MeV for the main downward beam of the TGF making the reverse beam\n detectable by the Fermi Gamma Ray Burst Monitor."],"Other":["Geant4  Python "]}Dryad2023-03-1510661855https://doi.org/10.7291/d1gm4p2235299FOS: Physical sciencesFOS: Physical sciences489694814 bytes2National Science Foundation