Thursday, March 06, 2008

Scientists identify origin of hiss in upper atmosphere, a 40-year mystery

Scientists have solved a 40-year-old puzzle by identifying the origin of the intense radio waves in the Earth's upper atmosphere that control the dynamics of the Van Allen radiation belts — belts consisting of high-energy electrons that can damage satellites and spacecraft and pose a risk to astronauts performing activities outside their spacecraft.

The source of these low-frequency radio waves, which are known as plasmaspheric hiss, turns out to be not lightning or instabilities from a plasma, as previously proposed, but an intense electromagnetic wave type called "chorus," which energizes electrons and was initially thought to be unrelated to hiss, said Jacob Bortnik, a researcher with the UCLA Department of Atmospheric and Oceanic Sciences.


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