Breakthrough in understanding rare lightning-triggered gamma-rays

The Telescope Array detected 10 bursts of downward terrestrial gamma-ray flashes (TGFs) between 2014 and 2016, more events than have been observed in rest of the world combined. They are the first to detect downward TGFs at the beginning of cloud-to-ground lightning, and to show where they originated inside thunderstorms. The array is by far the only facility capable of documenting the full TGF 'footprint' on the ground.