During thunderstorms, atmospheric electric fields can be strong enough to accelerate charged particles to tens of MeV and produce bursts of radio, x-ray, and gamma-ray emissions. The bursts are separated from lightning in time and often in location as well. Although the x rays can last for a minute or more, the radio and gamma-ray burst durations typically lie in the micro- or millisecond range. Some unusual, longer-duration gamma events last tens of seconds or even minutes. A collaboration of researchers from four institutions in Japan has now described one such event that took place during a winter thunderstorm over the Sea of Japan on 6 January 2007. Specialized detectors atop a nuclear power station recorded about 40 seconds of gamma rays, followed some 70 seconds later by a lightning stroke. The photons had energies that reached and exceeded 10 MeV and were unambiguously determined to have come from the...

You do not currently have access to this content.