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1 March 2007 USA

Twin spacecraft track solar storms, NASA says

By Maggie Fox, Health and Science Editor

WASHINGTON (Reuters) – New twin spacecraft are helping scientists track pesky solar storms from the sun to Earth, where they can disrupt satellites, communications and sometimes the electricity supply, the US space agency said on Thursday.

Even though the STEREO spacecraft are struggling to get into their final orbits, they are already sending back images that have experts re-evaluating what they know about these storms, called coronal mass ejections, project scientists said.

"These are big powerful things that leave the sun," Michael Kaiser, STEREO project scientist at NASA Goddard Space Flight Center in Greenbelt, Maryland, told reporters.

"They are storms full of electrically charged particles. They flow away from the sun at speeds of more than a thousand miles a second."

These are the storms that cause colorful auroras, but they can also cause electrical disturbances to satellites, and if they hit the surface of the planet they can overload electrical grids.

"The airlines are quite interested in these solar storms because they are flying polar routes," Kaiser added. "When a solar storm comes they can actually be out of radio communications."

So predicting when and how a storm will hit is increasingly important.

"With STEREO, we can track the front (of a storm) from the sun all the way to Earth, and forecast its arrival within a couple hours," said Russ Howard, principal investigator for the Sun Earth Connection Coronal and Heliospheric Investigation instrument, called SECCHI for short.

The orbiting SOHO observatory is providing some information, but the two STEREO spacecraft will be able to triangulate with SOHO and give a much better view of these bursts as they bud off the sun's surface.

The Solar Terrestrial Relations Observatory spacecraft are still nosing into position, where they will orbit the sun, one ahead of Earth, the other following behind.

But STEREO has already seen one such ejection come off the surface of the sun and morph as it headed into interplanetary space, crashing into, and then being blown along by, the solar wind – a stream of charged particles called ions.

"It's being picked up and swept along just like a leaf in a stream," Howard said.

Scientists thought the burst would maintain its shape. "But apparently it's not," Howard said.

"We are already surprised by how the structure has evolved as it is propagated outward."

Mission scientists said they would be distributing three-dimensional images from STEREO to museums and on the Internet, along with instruction of how to get 3-D glasses to view them.

The mission's Web site can be found at http://www.nasa.gov/mission_pages/stereo/mission/index.html

Source: Reuters

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