TETRA observation of gamma-rays at ground level associated with nearby thunderstorms

Abstract

Terrestrial gamma-ray flashes (TGFs) - very short, intense bursts of electrons, positrons, and energetic photons originating from terrestrial thunderstorms - have been detected with satellite instruments. TGF and Energetic Thunderstorm Rooftop Array (TETRA), an array of NaI(Tl) scintillators at Louisiana State University, has now been used to detect similar bursts of 50 keV to over 2 MeV gamma-rays at ground level. After 2.6 years of observation, 24 events with durations 0.02-4.2 ms have been detected associated with nearby lightning, three of them coincident events observed by detectors separated by ∼1000 m. Nine of the events occurred within 6 ms and 5 km of negative polarity cloud-to-ground lightning strokes with measured currents in excess of 20 kA. The events reported here constitute the first catalog of TGFs observed at ground level in close proximity to the acceleration site. Key Points Twenty-four terrestrial gamma-ray flashes are detected at ground level Nine TGFs were within 6 ms and 3 km of negative polarity cloud-ground lightning Gamma-rays are detected over the energy range 50 keV-2 MeV ©2013 The Authors. Journal of Geophysical Research: Space Physics published by Wiley on behalf of the American Geophysical Union.