Observation of Terrestrial Gamma-Ray Flashes with AGILE

We report the status of the detection of Terrestrial Gamma-Ray Flashes (TGFs) by the AGILE satellite. During the period June 2008 - August 2009 the Mini-Calorimeter (MCAL) detector onboard AGILE revealed 78 high-significance events showing millisecond duration, photons energy extended up to several tens of MeV and a geographical distribution peaked over continental Africa and South-East Asia. The cumulative spectrum in the range 0.5-40 MeV can be effectively described by a Bremsstrahlung spectrum. Both the TGF cumulative spectral properties and their geographical and local time distributions are in good agreement with the RHESSI results. The onset of the trigger logic on the 1ms time scale in March 2009 enhanced the trigger sensitivity resulting in a detection rate more than doubled with respect to the previous configuration. Thanks to its very low inclination orbit (2.5°) AGILE can map the equatorial belt in search of TGFs with unprecedented exposure.