Fermi-GBM Observations of Terrestrial Gamma-ray Flashes
by
Suzanne Foley(MPE, Garching)
→
Europe/Stockholm
Description
Terrestrial Gamma-ray Flashes are short bursts of energetic radiation associated with thunderstorms and lightning. While the Gamma-ray Burst Monitor (GBM) on Fermi was designed to observe gamma-ray bursts, its large BGO detectors are excellent for observing TGFs. The TGF pulses observed with GBM appear to either be symmetrical or have faster rise time than fall times. A variety of time profiles are observed including TGFs with multiple pulses separated in time and some clear cases of TGFs consisting of partially overlapping pulses. Using ground-based radio observations of lightning from the World Wide Lightning Location Network (WWLLN), TGFs and their associated lightning are found to be simultaneous to ~ 40 µ s. The lightning locations are typically within 300 km of the sub-spacecraft point. Some TGFs are observed mainly as electrons and have significantly longer durations than typical gamma-ray TGFs. Strong 511 keV positron lines have been found in a number of GBM TGFs, showing that they have a significant positron component.