Magnetic Field on Earth Flawed

Add particularly nasty solar storms to the list of woes facing the planet in the coming years.

Scientists have learned that it's not just the size and the strength of the sun's eruptions that threaten power grids, disable satellites and scramble radio signals on Earth. In a startling reversal of generally accepted theory, researchers using a fleet of solar-watching satellites have learned that thick gobs of solar plasma have easy and regular access into Earth's magnetosphere, thanks to a trick of nature.

Scientists previously believed that when sun's magnetic field was aligned with Earth's, the planet was safely cocooned within its protective bubble. Not so, report researchers at this week's American Geophysical Union meeting in San Francisco.


"It's exactly opposite of the way we thought," said David Sibeck, with NASA's Space Weather Laboratory at the Goddard Space Flight Center in Greenbelt, Md. "If all of this is true it should be that we're in for a much tougher time in the next 11 years than we have been in the past 11."

The sun has an 11-year cycle, which is next expected to peak in 2011 or 2012. During maximum periods of activity, the sun produces more flares and geomagnetic storms, which can blast Earth with powerful streams of electrically charged plasma.

The sun's magnetic field flips direction every cycle, and the next solar maximum will occur when the field is unfavorably aligned with Earth's, scientists said.

With data taken by the five-member THEMIS satellite network, scientists have learned that huge blankets of solar particles -- 4,000 miles thick -- stream into Earth's magnetosphere via solar magnetic field lines that wrap around Earth, north to south, "like an octopus wraps its tentacles around its prey," said Jimmy Raeder, with the University of New Hampshire's Physics and Space Science Center.

Earth adopts the field lines as its own, incorporating the stowaway plasma into its sphere of space. When a solar storm strikes, the particles are energized.

"We had always thought the shields would be completely closed if the fields were aligned. There would be virtually no plasma coming in. What this shows is that it's really the opposite," Rader said.

The discovery will be incorporated into computer models and simulations used to predict adverse space weather.

"We'll have more confidence in the future that when we observe things coming from the sun we'll come to a (forecaster), provide those observations and ask him 'What's going to happen next?'" Sibeck said.

"We're moving toward the capability to predict these troublesome intervals. If we can do that, we can protect our spacecraft; we can notify astronauts in space that this is not a good time to spacewalk; we can tell a power line company, 'You're likely to experience a transformer blowout.'," he said.