Relating terrestrial gamma-ray flash production to associated lightning and thunderstorm characteristics

Abstract

Terrestrial Gamma-ray Flashes (TGFs) are puzzling, but potentially hazardous bursts of high-energy radiation associated with the everyday phenomena of lightning. Not every lightning flash produces a TGF, however, and the question of what makes a TGF-associated lightning flash different is not well understood. This dissertation investigates this question by examining how TGF production is related to thunderstorm characteristics such as inter-flash intervals, flash rate trends, and flash amplitudes. Additionally, investigation into the precise timing relationship between TGFs and stroke signatures in their associated lightning flash is also presented. The conclusions of these studies show that TGFs are most likely to occur after longer than usual charge-up times, when the flash rates tend to be declining in storms, and when amplitudes of flashes are stronger than normal. The last study also details the presence of two distinct excess peaks of delayed lightning signals occurring after TGFs compared to other non-TGF flashes. This study examines the amplitudes of these delayed lightning signals and compares those signals to the entire distribution of non-TGF strokes. These findings hint that TGF-production may be the result of unusually complex lightning flashes. However, further research into these peaks requires additional data from other spacecraft and perhaps updated TGF catalogs to examine the context of these lightning flashes. Nonetheless, this initial study may further help explain why TGFs are not produced in association with all lightning flashes.