Article: Sky high: gamma-ray bursts are common in Earth's upper atmosphere.(This Week)

Enigmatic bursts of high-energy gamma rays produced in Earth's atmosphere are surprisingly strong and frequent, satellite data suggest.

In the early 1990s, Earth-orbiting sensors originally designed to monitor sporadic flares of gamma rays from exotic sources such as black holes and neutron stars also detected the high-energyphotons coming from a more mundane source--Earth's atmosphere. These terrestrial gamma-ray flashes (TGFs) were seen once every few weeks and lasted around a millisecond, says physicist David M. Smith of the University of California, Santa Cruz.

Now, Smith and his colleagues have analyzed portions of data gathered by another gamma ...