Gamma-ray Localization of Terrestrial Gamma-ray Flashes by AGILE
Abstract
We report the first direct localization of Terrestrial Gamma-ray Flashes (TGFs) in space by the AGILE gamma-ray imager above 20 MeV. AGILE is one of the three currently active space missions detecting TGFs. AGILE is detecting about 10 TGFs/month by the mini-calorimeter (MCAL) instrument sensitive in the energy range 0.35-100 MeV and was the first to clearly show the extension of the TGFs energy spectrum up to at least 40 MeV. Motivated by this initial discovery, we searched for detections in the AGILE Gamma-Ray Imaging Detector (GRID) data correlated with TGFs detected in MCAL. Among the 119 TGFs detected by MCAL at MeV energies during the period June, 2008 - December, 2009, we detect 8 TGFs with gamma-ray photons of energies above 20 MeV localized by the AGILE gamma-ray imager with a relatively good accuracy of 5-10 deg at 50 MeV. Remarkably, all TGF-associated gamma-rays are compatible with a terrestrial production site closer to the sub-satellite point than 400km, independently confirming the results obtained by combining space and ground measurements (sferics). Considering that our photons reach the AGILE satellite at 540 km altitude with limited scattering or attenuation, these results have deep implications for the study of TGFs.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2010
- Bibcode:
- 2010AGUFMAE11A0330M
- Keywords:
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- 3304 ATMOSPHERIC PROCESSES / Atmospheric electricity;
- 3324 ATMOSPHERIC PROCESSES / Lightning