The Relationship Between Instantaneous Lightning Flash Rates and TGF Production in Thunderstorms

Abstract:

We provide evidence that Terrestrial Gamma-Ray Flashes (TGFs) occur ubiquitously in thunderstorm phases with the exception that they are produced less often during the peak lightning flash rate periods of the storms. This conclusion comes from examining the results of 418 manually tracked TGF-producing thunderstorms. Fermi-GBM identified TGFs are used for this analysis and lightning data comes from both WWLLN and ENTLN. The data from these storms suggests that TGFs are likely to occur in almost every phase of the storm. However, we note that TGFs tend to occur more often when the flash rates of the storm are lower, and they rarely occur during the peak flash rate periods of the storms. Furthermore, we find that 65% of the TGFs in our sample occur after the peak lightning activity in their storms, even though the time of the peak lightning activity varies in each storm. This implies that the TGFs are likely to occur in the declining stages of the thunderstorms. We also show that lightning flashes (both IC and CG) near the time of the TGF tend to be stronger than most other flashes in the same storm.