Determining 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 leader
Data files
Mar 15, 2023 version files 489.64 MB
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12km_full_upward_Hits.txt
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20190725.nldn.txt
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6km_full_upward_Hits.txt
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8km_full_upward_Hits.txt
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joeAltdown_reverseonly_10.txt
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joeAltdown_reverseonly_6.txt
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joeAltdown_reverseonly_8.txt
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joeAltdown_reverseonly_9.txt
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joeupAlt_12.txt
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joeupAlt_6.txt
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joeupAlt_8.txt
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README.md
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x10_10km_reverseonly_Hits.txt
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x1000_6km_reverseonly_Hits.txt
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x1000_8km_reverseonly_Hits.txt
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x1000_9km_reverseonly_Hits.txt
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Abstract
We provide an updated analysis of the gamma-ray signature of a terrestrial gamma ray flash (TGF) detected by the Fermi Gamma-ray Burst Monitor first reported by Pu et al. 2020. A TGF produced 3 ms prior to a negative cloud-to-ground return stroke was close to simultaneous with an isolated low frequency radio pulse during the leader’s propagation, with a polarity indicating downward moving negative charge. In prior observations this ‘slow’ low frequency signal has been strongly correlated with upward (opposite polarity) directed TGF events [Pu et al. 2019; Cummer et al. 2011] leading the authors to conclude that the Fermi gamma ray observation is actually the result of a reverse positron beam generating upward directed gamma rays. We investigate the feasibility of this scenario and determine a lower limit on the luminosity of the downward TGF from the perspective of gamma-ray timing uncertainties, TGF Monte Carlo simulations, and meteorological analysis of a model storm cell and its possible charge structure altitudes. We determined the most likely source altitude of the reverse beam TGF to be 7.5 km +/- 2.6 km, just below an estimated negative charge center at 8 km. At that altitude the Monte Carlo simulations indicate a lower luminosity limit of 2 x 10^18 photons above 1 MeV for the main downward beam of the TGF making the reverse beam detectable by the Fermi Gamma Ray Burst Monitor.
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Python