Gamma-Ray Localization of Terrestrial Gamma-Ray Flashes

TL;DR

This study presents the first precise space-based localization of terrestrial gamma-ray flashes (TGFs) at energies above 20 MeV, using AGILE satellite data to identify their terrestrial origin within 400 km.

Contribution

The paper introduces an innovative event selection method and correlates AGILE satellite gamma-ray data with TGF detections to localize TGFs with unprecedented accuracy.

Findings

Detected 8 TGFs with gamma-ray energies above 20 MeV.

Localized TGFs within 400 km of the sub-satellite point.

Achieved localization accuracy of 5-10 degrees at 50 MeV.

Abstract

Terrestrial Gamma-Ray Flashes (TGFs) are very short bursts of high energy photons and electrons originating in Earth's atmosphere. We present here a localization study of TGFs carried out at gamma-ray energies above 20 MeV based on an innovative event selection method. We use the AGILE satellite Silicon Tracker data that for the first time have been correlated with TGFs detected by the AGILE Mini-Calorimeter. We detect 8 TGFs with gamma-ray photons of energies above 20 MeV localized by the AGILE gamma-ray imager with an accuracy of 5-10 degrees at 50 MeV. Remarkably, all TGF-associated gamma rays are compatible with a terrestrial production site closer to the sub-satellite point than 400 km. Considering that our gamma rays reach the AGILE satellite at 540 km altitude with limited scattering or attenuation, our measurements provide the first precise direct localization of TGFs from space.