Characteristics of TETRA-II TGFs and their Associated Lightning Activity

Abstract:

Over four years of operation, the ground-based TETRA-II experiment has detected 46 bursts of gamma rays associated with nearby lightning at three different locations in Louisiana, Puerto Rico, and Panama. The observed events have durations typically less than ~1 ms and individual energies up to at least 6 MeV, there is no evidence of pileup of lower energy photons, and they closely resemble terrestrial gamma flashes (TGFs) observed in space. Nearly all events are closely associated with nearby lightning sferics. We present here an overview of the TETRA-II events including a detailed discussion of the temporal patterns, energy spectrum, and relation to nearby lightning. Because ground-based observations are taken in close proximity to the thunderstorms, we can compare the gamma-ray observations with a detailed analysis of the thunderstorm characteristics including lightning frequency, peak currents, and NEXRAD radar data to show that the TETRA-II events are closely connected with the peak intensification of the storms. We present evidence for one event with no lightning within 15 km and show an analysis of the multiple-pulsed and consecutive events.