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Lightning Shows II

March 22, 2011

Airliners stay far away from thunderstorms to avoid the hail, lightning, and strong winds. And recent observations have shown one more potential hazard: outbursts of gamma rays, the most powerful form of energy.

These outbursts are known as TGFs -- terrestrial gamma-ray flashes. They were discovered in the 1990s by a space telescope that was looking for gamma rays from far beyond Earth.

Since then, observations by other space telescopes have suggested that thunderstorms produce hundreds of TGFs every day.

The origin of the flashes remains a bit of a mystery. The leading idea says that lightning inside powerful thunderstorms produces a strong electric field at the tops of the clouds. The electric field creates a geyser of electrons that shoots toward space. If an electron's path is altered by a nearby molecule, the electron emits a gamma ray. And if that happens with enough electrons, the result is a TGF.

Most of the energy seems to be concentrated above about 10 miles -- a little higher than most airliners fly. But exposure to a TGF could zap a passenger with the equivalent of several hundred chest X-rays.

The process that creates TGFs is still poorly understood. But a spacecraft that'll launch later this year may yield some answers. It's only the size of a football, but it'll spend several months studying TGFs and other outbursts from thunderstorms. More about these outbursts -- and beams of antimatter -- tomorrow.

Script by Damond Benningfield, Copyright 2011


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