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发表于 2009-12-23 10:14:43
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Aurora borealis that lit up the Prairie sky on December 21
A Merry Christmas and Happy New Year to you all!
It's a Xmas time, it's a wonderful time of the year.
Enjoy parties, meet friends and shopping around.
As expected: Aurora borealis that lit up the Prairie sky like never before.
Canadian and U.S. scientists working on a $200-million mission to unravel the mysteries of the northern lights have made a "startling discovery" after 20 cameras positioned throughout Canada and Alaska -- in combination with satellite imagery and radar data -- captured the "spectacular" collision of two waves of aurora borealis that lit up the Prairie sky like never before.
The remarkable sequence of explosive flashes was captured during the winter of 2007-2008 and only recently reconstructed by scientists interpreting data from the network of ground cameras, radar stations and an array of sensors aboard five THEMIS satellites.
It began as a slow-moving "curtain" of auroras moved north across the Prairie provinces, eventually reaching a latitude of about Edmonton.
To the northwest, meanwhile, a fast-moving "knot" of northern lights centred around Fort Nelson, B.C. -- and encompassing the entire region where the boundaries of B.C., Yukon, Northwest Territories and Alberta meet -- sped toward the Prairies' slow-moving band of auroras.
The resulting collision produced a sudden, "explosive" flare-up of northern lights over the Saskatchewan-Manitoba border.
The "movie" depicting the crash of Canadian auroras was created by UCLA researcher Toshi Nishimura, who tapped data from recordings above and below the collision to create a coherent, simulated picture of the event.
"Our jaws dropped when we saw the movies for the first time," said UCLA scientist Larry Lyons, one of scores of researchers involved in the joint NASA-Canadian Space Agency THEMIS project probing the famous polar light show. THEMIS, launched in 2007, stands for "Time History of Events and Macroscale Interactions during Substorms."
"These outbursts are telling us something very fundamental about the nature of auroras," Mr. Lyons said.
The colliding bands of light are so vast that observers in any one location would be unable to perceive the full extent of celestial illumination, the scientists explained in a summary of their study, presented last week at a conference in San Francisco.
Mr. Lyons described how the images were "like nothing I had seen before. Over the next several days, we surveyed more events. Our excitement mounted as we became convinced that the collisions were happening over and over."
The scientists believe the outbursts are produced by interactions between the auroras and the Earth's "plasma tail," a vast stream of charged particles amassed from solar winds and bound together by the planet's magnetic field.
The Northern Lights -- also energized by charged particles -- appear to erupt dramatically when "jetting through the tail."
Dave Sibeck, a THEMIS scientist with NASA's Goddard Space Flight Center in Maryland, said combining data from various sources has given the team "a nearly complete picture of what causes explosive auroral substorms."
By December 2007, project scientists announced they'd already made several key discoveries about the northern lights -- including the presence of "magnetic ropes" linking the Earth's upper atmosphere to the sun.
And in February 2008, the team revealed how the Earth's "magnetotail" -- a stretching of the planet's magnetic field caused by solar winds -- can "snap" during space substorms to make the northern lights "dance."
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发表于 2009-12-9 09:35:40
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