AGILE observation of terrestrial gamma-ray flashes

Marisaldi, M.; Argan, A.; Trois, A.; Giuliani, A.; Tavani, M.; Labanti, C.; Fuschino, F.; Bulgarelli, A.; Longo, F; Barbiellini, G.; Del Monte, E.; Moretti, E.; Trifoglio, M.; Costa, E.; Caraveo, P.; Cattaneo, P; Chen, A.; D'Ammando, F.; De Paris, G.; Di Cocco, G.; Di Persio, G.; Donnarumma, I.; Evangelista, Y.; Feroci, M.; Ferrari, A.; Fiorini, M.; Froysland, T.; Galli, M.; Gianotti, F.; Lapshov, I.; Lazzarotto, F.; Lipari, P.; Mereghetti, S.; Morselli, A.; Pacciani, L.; Pellizzoni, A.; Perotti, F.; Picozza, P.; Piano, G.; Pilia, M.; Prest, M.; Pucella, G.; Rapisarda, M.; Rappoldi, A.; Rubini, A.; Sabatini, S.; Soffitta, P.; Striani, E.; Vallazza, E.; Vercellone, S.; Vittorini, V.; Zambra, A.; Zanello, D.; Antonelli, L. A.; Colafrancesco, S.; Cutini, S.; Giommi, P.; Lucarelli, F.; Pittori, C.; Santolamazza, P.; Verrecchia, F.; Salotti, L.

doi:10.1393/ncc/i2011-10870-5

Terrestrial Gamma-ray Flashes (TGFs) are very short (up to a few milliseconds) energetic bursts of photons and electrons originating from severe thunderstorms mainly in the equatorial and tropical regions. Although several production models have been proposed so far, TGFs still remains a mistery since there is not wide consensus yet on their acceleration mechanism, production sites, maximal energy and fluence. AGILE, operating since mid 2007. is detecting hundreds of TGFs with the Mini-Calorimeter (MCAL) instrument. Thanks to the MCAL energy range extended up to 100 MeV and its flexible trigger logic on sub-millisecond time scales. AGILE is adding a wealth of observations which pose severe constraints on production models. In this paper we will describe the main characteristics of the AGILE TGFs sample, focusing on the recent results concernings the first localization of TGFs at gamma-ray energies by means of the AGILE silicon tracker.