A particle accelerator operates in Earths upper atmosphere above major thunderstorms at energies comparable to some of the most exotic environments in the universe, according to new satellite observations of terrestrial gamma-ray flashes.
Terrestrial gamma-ray flashes (TGFs) are very short blasts of gamma rays, lasting about one millisecond, that are emitted into space from Earths upper atmosphere. The gamma rays are thought to be emitted by electrons traveling at near the speed of light when they scatter off of atoms and decelerate in the upper atmosphere. TGFs were first discovered in 1994 by the Burst and Transient Source Experiment (BATSE) on the Compton Gamma-Ray Observatory.
BATSE could only detect TGFs in a special observing mode and was limited in its ability to count them or measure their peak energies. New observations from the Reuven Ramaty High Energy Solar Spectroscopic Imager (RHESSI) satellite raise the maximum recorded energy of TGFs by a factor of ten and indicate that the Earth gives off about 50 TGFs every day, and possibly many more. The findings are reported in the February 18 issue of Science by a team of researchers from the University of California, Santa Cruz, UC Berkeley, and the University of British Columbia (UBC). "The idea that the Earth, a fairly small and tame planet, can be an accelerator of particles to ultrarelativistic energies is fascinating to me," said David Smith, an assistant professor of physics at UC Santa Cruz and first author of the paper. "The energies we see are as high as those of gamma rays emitted from black holes and neutron stars," Smith said.
Tim Stephens | EurekAlert!
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