Simultaneous space-based observations of terrestrial gamma-ray flashes and lightning optical emissions: Investigation of the terrestrial gamma-ray flash production mechanisms

The relative timing between terrestrial gamma-ray flashes (TGFs) and lightning optical emissions is a critical parameter that may elucidate the production mechanism(s) of TGFs. In this work, we study the correlation between optical emissions detected by the Geostationary Lightning Mapper and TGFs triggered by the Fermi Gamma-ray Burst Monitor. The correlation result suggests that TGFs are produced during the last stage of lightning leader channel development. Accordingly, TGFs are initiated by lightning leaders perhaps augmented by additional electron acceleration and multiplication by the ambient large-scale electric field in thunderclouds.