In its first 2 years of operation, the ground‐based Terrestrial gamma ray flash and Energetic Thunderstorm Rooftop Array (TETRA)‐II array of gamma ray detectors has recorded 22 bursts of gamma rays of millisecond‐scale duration associated with lightning. In this study, we present the TETRA‐II observations detected at the three TETRA‐II ground‐level sites in Louisiana, Puerto Rico, and Panama together with the simultaneous radio frequency signals from the lightning data sets VAISALA Global Lightning Dataset, VAISALA National Lightning Detection Network, Earth Networks Total Lightning Network, and World Wide Lightning Location Network. The relative timing between the gamma ray events and the lightning activity is a key parameter for understanding the production mechanism(s) of the bursts. The gamma ray time profiles and their correlation with radio sferics suggest that the gamma ray events are initiated by lightning leader activity and are produced near the last stage of lightning leader channel development prior to the lightning return stroke.
The terrestrial gamma‐ray flash (TGF) and Energetic Thunderstorm Rooftop Array (TETRA‐II) detected 22 X‐ray/gamma‐ray flash events associated with lightning between October 2015 and March 2019 across three ground‐based detector locations in subtropical and tropical climates in Louisiana, Puerto Rico, and Panama. Each detector array consists of a set of bismuth germanate scintillators that record X‐ray and gamma‐ray bursts over the energy range 50 keV–6 MeV (million electron volts). TETRA‐II events have characteristics similar to both X‐ray bursts associated with lightning leaders and TGFs: sub‐millisecond duration, photons up to MeV energies, and association with nearby lightning (typically within 3 km). About 20 of the 22 events are geolocated to individual lightning strokes via spatiotemporally coincident sferics. An examination of radar reflectivity and derived products related to events located within the Next Generation Weather Radar (NEXRAD) monitoring region indicates that events occur within mature cells of severe and non‐severe multicellular and squall line thunderstorms, with core echo tops which are at or nearing peak altitude. Events occur in both high lightning frequency thunderstorm cells and low lightning frequency cells. Events associated with high frequency cells occur within 5 min of significant lightning jumps. Among NEXRAD‐monitored events, hail is present within 8 km and 5 min of all except a single low‐altitude cold weather thunderstorm. An association is seen with maximum thunderstorm development, lightning jumps, and hail cells, indicating that the TETRA‐II X‐ray/gamma‐ray events are associated with the peak storm electrification and development of electric fields necessary for the acceleration of electrons to high energies.more » « less
- NSF-PAR ID:
- Publisher / Repository:
- DOI PREFIX: 10.1029
- Date Published:
- Journal Name:
- Journal of Geophysical Research: Atmospheres
- Medium: X
- Sponsoring Org:
- National Science Foundation
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