Posted on 03/21/2008 2:35:24 AM PDT by Swordmaker
NASA Spacecraft Make New Discoveries about Northern Lights
12.11.2007 |
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"The mission is only beginning but THEMIS is already surprising us," says Vassilis Angelopoulos the mission's principal investigator at the University of California, Los Angeles. The discoveries began in March less than a month after the five THEMIS satellites had been activated. "On March 23, 2007, a substorm erupted over Alaska and Canada producing vivid auroras for more than two hours." A network of ground cameras organized to support THEMIS photographed the display from below while the satellites measured particles and fields from above. Right: Auroras over Alaska on March 23-24, 2007. Photo credit: Daryl Pederson. [More] Right away the substorm surprised investigators: "The auroras surged westward twice as fast as anyone thought possible, crossing 15 degrees of longitude in less than one minute," says Angelopoulos. The storm had traversed an entire polar time zone in 60 seconds flat! Also, "the display was surprisingly bursty." Photographs taken by ground cameras and NASA's Polar satellite (also supporting the THEMIS mission) revealed a series of staccato outbursts each lasting 10 minutes or so. "Some of the bursts died out while others reinforced each other and went on to become major events."
Even more impressive was the substorm's power. Angelopoulos estimates the total energy of the two-hour event at five hundred thousand billion (5 x 1014) Joules. That's approximately equivalent to the energy of a magnitude 5.5 earthquake. Where does all that energy come from? THEMIS may have found an answer: "The satellites have found evidence for magnetic ropes connecting Earth's upper atmosphere directly to the Sun," says Dave Sibeck, project scientist for the mission at the Goddard Space Flight Center. "We believe that solar wind particles flow in along these ropes, providing energy for geomagnetic storms and auroras." A "magnetic rope" is a twisted bundle of magnetic fields organized much like the twisted hemp of a mariner's rope. Spacecraft have detected hints of these ropes before, but a single spacecraft is insufficient to map their 3D structure. THEMIS's five satellites were able to perform the feat. Right: A magnetic map of a magnetospheric rope observed in cross-section by the THEMIS satellites on May 20, 2007. [Larger image] "THEMIS encountered its first magnetic rope on May 20, 2007," says Sibeck. "It was very large, about as wide as Earth, and located approximately 40,000 miles above Earth's surface in a region called the magnetopause." The magnetopause is where the solar wind and Earth's magnetic field meet and push against one another like sumo wrestlers locked in combat. There, the rope formed and unraveled in just a few minutes, providing a brief but significant conduit for solar wind energy. Other ropes quickly followed: "They seem to occur all the time," says Sibeck. THEMIS has also observed a number of relatively small explosions in Earth's magnetic bow shock. "The bow shock is like the bow wave in front of a boat," explains Sibeck. "It is where the solar wind first feels the effects of Earth's magnetic field." When a knot of magnetism within the solar wind hits the bow shock--"Bang!" he says. "We get an explosion." The technical term for these explosions is "hot flow anomalies" or HFAs. HFAs boost the temperature of solar wind particles ten-fold (as high as 10 million degrees) and they can stop the solar wind dead its tracks. "This is no mean achievement considering the fact that the solar wind moves at supersonic speeds near a million miles per hour." Above: A cartoon of a hot flow anomaly observed by THEMIS on July 4, 2007, and a computer simulation of the explosion. Credit: N. Omidi. [More] "Hot flow anomalies may not play a major role in energizing auroral substorms--they happen too infrequently, less than once a day," notes Jonathan Eastwood of the University of California, Berkeley, who is studying them. "Nevertheless they are of interest. This is a fundamental physical process that accelerates particles to high energies and we are delighted to be able to study it." Powerful substorms, giant magnetic ropes, explosions that stop the solar wind in its tracks: "We have much more to learn about all these things," says Angelopoulos. "I can't wait to see what comes next." |
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Anthropogenic global warming just took another step towards irrelevance. We now realize the earth is encompassed by an electric blanket plugged into the sun.
Cheers!
...and Happy Good Friday.
If we ever figure out how to harness Gravity, there will be no end to our place in the Universe.
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This is just breathtaking...I’ve seen only one, but it was very beautiful....
Just think, if those ropes and streams were always visible to the naked eye, how amazing our view of the solar system would be.
They are always visible here. Lately, though, they have been pale, color washed out even though they can be fairly bright and cover the whole sky. I suspect the quiet sun is not capable of sending the colorful particles these days.
The one I saw was a definite rose color, it looked as though it was rising out of the trees at the end of the road...it got so bright that on a moonless night, you could see the road, the trees on either side, a deer crossing the highway half a mile on down...
I’d love to see the lights again, but Alaska is so far away.
Some day, when I have time.
;)
ping
One of my aurora photographs many years ago actually made a magazine cover, but the aurora is so feeble anymore that it’s not worth it to set up camera and tripod, and the city lights overwhelm everything anyway. Besides, you don’t have to go to Alaska to see what is left of the aurora. There is also Greenland.
Cool!
Oh, well, Greenland is right next door. /joke
I was so glad that we lived in a very rural area, the night of the aurora here. It was REALLY dark, and thus we could see it very well...
Approximately where in Alaska are you?
We have the aurora all the time, so that is not of interest. The changes such as loss of color and loss of focus are of interest. The sun is weakening and the mag field is also weakening, according to some who track these things, and it might be visible in changes to the aurora that we can see. But, sky season is about over. It will be light all night in a few weeks and we will have to wait for next fall for the next installment.
I am in the middle of this paradise. It is zero again this morning and the yard is overrun with rabbits, which also follows the sunspot cycle. It was -50 a little ways north of here this morning.
I see...I live in S. central MO...very beautiful here, now, with daffodils coming up; sadly there’s been a lot of flooding in the state the past few days.
I know that sunspot activity has been far too quiet lately, and that it isn’t good news for the climate, being related to cooling...
I hope spring comes soon for you. :D
Last summer came late and left early and gardeners didn’t do well. Actually the growing season was missing nearly altogether. Even the black spruce produced no spruce cones and the squirrels are skinny now. Most interesting.
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