Northern Lights Controlled by Magnetic "Ropes"

Anne Minard in San Francisco, California
for National Geographic News
December 11, 2007

NASA spacecraft have revealed new insights into the forces that cause the northern lights, including giant magnetic "ropes" between Earth and the sun.

Until now, scientists haven't had adequate tools to study how energy from the sun is captured by Earth's magnetic field to trigger the awe-inspiring phenomenon.

"What it shows is promise," said Vassilis Angelopoulos, researcher at the University of California at Los Angeles and principal investigator for a new NASA mission to study auroras.

"We're coming up on a new era in space physics."

The findings were presented at a teleconference today at the fall meeting of the American Geophysical Union in San Francisco.

Perfect Storm

The latest discoveries began on March 23, when a "substorm" erupted over Alaska and Canada, producing vivid auroras for more than two hours. During such an event, the northern lights' green and white streaks periodically build in intensity until they blast apart into multicolored, fragmented lights.

(Download a desktop photo of the northern lights.)

A network of ground cameras photographed the display from below while a series of five satellites, collectively called THEMIS, looked on from above.

(Read about the THEMIS mission and the probes' launch earlier this year.)

"The auroras surged westward twice as fast as anyone thought possible, crossing 15 degrees of longitude in less than one minute," Angelopoulos said.

"The storm traversed an entire polar time zone, or 400 miles [640 kilometers], in 60 seconds flat."

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