The Daily Item, Sunbury, PA


March 1, 2013

Van Allen probes spy third band of radiation before it disappears

By Brian Vastag

The Washington Post

WASHINGTON — Happy accidents litter the annals of scientific discovery.

Here’s another: NASA probes that are exploring the treacherous twin Van Allen radiation belts encircling the Earth spied a third, unexpected band of radiation that burst into view and then disappeared, scientists report Thursday.

The NASA probes spotted the temporary band of high-energy electrons just three days after launch.

The discovery has stunned scientists and is forcing a rethink of the radiation environment above Earth, with implications for proposed human deep-space missions.

In 1958, early NASA satellites recorded two zones of dangerous electron and proton radiation extending 12,000 miles beyond Earth. Named for scientist James Van Allen, the dual donut-shaped regions were the first major discovery of the space age.

Last Aug. 30, NASA launched the twin Radiation Belt Storm Probes - since renamed the Van Allen Probes - to provide a deeper understanding of the region. A radiation-detection instrument was scheduled to be switched on a month later, but mission scientists decided to turn it on early.

Three days after launch, and just a day after the instrument powered up, the third belt appeared.

“We initially thought, ‘This looks odd, maybe something’s screwed up with our instrument,’” said Shri Kanekal, a mission scientist at NASA’s Goddard Space Flight Center in Greenbelt, Md. “But as days went by [the third belt] just stood there. We checked our instrument and became more and more confident there was not something wrong.”

The third belt, which formed between the two known belts, disappeared about a month later when a blast of energy from the sun blew past Earth. Such solar weather can warp and compress the outer Van Allen belt, but earlier missions had never seen a third belt form.

Researchers are now puzzling over the temporary band of high-energy electrons. They’re trying to understand why it did not quickly merge with the outer belt, as predicted by current understanding of the physics of the region.

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