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New theory behind particle storms in space

Scientists say Earth's radiation belt, not sun bursts, creates high-speed particles that can damage satellites.

Space physicists concerned about speeding particles that damage satellites - cutting off telephone pagers and disrupting power lines - got a wake-up call this week. New research shows some of what they thought they knew is wrong.

For 30 years, textbooks have said the electrically charged particles that whizz around Earth are generated by the sun. Now, they've discovered that - while solar outbursts may trigger storms and supply much of their energy - Earth's own magnetically controlled system supplies the harmful high-speed particles. It's a vital discovery for scientists, who need to know what speeding particles are up to in order to help prevent satellite damage.

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The discoveries were summarized by Thomas Moore, a space physicist at the NASA Goddard Space Flight Center in Greenbelt, Md., during a meeting here of the American Geophysical Union. He said an array of United States and international satellites is giving scientists a more comprehensive view of what goes on around our planet.

These satellites have also led to a related discovery that overturns another theory in textbooks: that solar outbursts add material to Earth's outer atmosphere. They do add some material, Dr. Moore said. However, they stimulate a reaction by which the Earth system ejects a much larger mass - mainly oxygen atoms - from its own atmosphere. This may be a slow-motion version of what happened when Mars lost its atmosphere. But don't worry, "there's no serious loss ... that's going to turn Earth into a Mars-like planet," Moore said.

The stakes are higher when it comes to the particle storms. The solar cycle is moving toward maximum activity. Massive solar outbursts are becoming more frequent. Satellite managers need as good an understanding as scientists can give them of what is likely to happen in the area around Earth.

Earth's magnetic field shunts aside most material coming from the sun. But an energetic outburst hits that field like a hammer, squeezing and jiggling it. This can dump particles into the lower atmosphere, causing auroras. The magnetic storms also can induce voltage surges that trip power outages on the ground. Meanwhile, electrons magnetically confined in the so-called radiation belts accelerate to nearly the speed of light.

It's this neat picture that needs revision. Daniel Baker of the University of Colorado, Boulder, explained that scientists thought these particles were generated by the sun and its outflows. Now, his group's research shows the radiation belts do the accelerating themselves.

Space physicists now have to revise their computer programs that simulate Earth's space-weather system. Until they include the new perspective, their global simulations "will lack reality," Moore warned. And that would be no help at all to spacecraft managers.

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