Detection of terrestrial gamma-ray flashes with the AGILE/MCAL

Abstract

AGILE is one of the satellites currently detecting terrestrial gamma-ray flashes (TGFs). In particular, the AGILE MiniCALorimeter detected more than 2000 events in 8 years activity, by exploiting a unique sub-millisecond timescale trigger logic and high-energy range. A change in the onboard configuration enhanced the trigger capabilities for the detection of these events, overcoming dead time issues and enlarging the detection rate of these events up to >50 TGFs/month, allowing to reveal shorter duration flashes. The quasi-equatorial low-inclination (2.5∘) orbit of AGILE allows for the detection of repeated TGFs coming from the same storms, at the same orbital passage and throughout successive orbital overpasses, over the same geographic region. All TGFs detected by AGILE are fulfilling a database that can be used for offline analysis and forthcoming studies. The limited number of missions currently detecting these brief terrestrial flashes makes the understanding of this phenomenon very challenging and, in this perspective, the AGILE satellite played and still plays a major role, helping shedding light to many aspects of TGF science.