The First Fermi-GBM Terrestrial Gamma Ray Flash Catalog

We present the first Fermi Space Telescope Gamma Ray Burst Monitor (GBM) catalog of 4,144 terrestrial gamma ray flashes (TGFs), detected since launch in 11 July 2008 through 31 July 2016. We discuss the updates and improvements to the triggered data and off-line search algorithms, comparing this improved detection rate of similar to 800 TGFs per year with event rates from previously published TGF catalogs from other missions. A Bayesian block algorithm calculated the temporal and spectral properties of the TGFs, revealing a delay between the hard (>300 keV) and soft (<= 300 keV) photons of around 27 mu s. Detector count rates of low-fluence events were found to have average rates exceeding 150 kHz. Searching the World-Wide Lightning Location Network data for radio sferics within +/- 5 min of each TGF revealed a clean sample of 1,314 World-Wide Lightning Location Network locations, which were used to to accurately locate TGF-producing storms. It also revealed lightning and storm activity for specific regions, as well as seasonal and daily variations of global lightning patterns. Correcting for the orbit of Fermi, we quantitatively find a marginal excess of TGFs being produced from storms over land near oceans (i.e., narrow isthmuses and small islands). No difference was observed between the duration of TGFs over the ocean and land. The distribution of TGFs at a given local solar time for predefined American, Asian, and African regions were confirmed to correlate well with known regional lightning rates.