Giant "Tornadoes" Seen Erupting From the Sun
Richard A. Lovett
for National Geographic News
|June 3, 2008|
The sun produces giant tornado-like jets that stretch thousands of miles into space, new satellite data shows.
The solar tornadoes typically last about ten minutes and occur near the sun's poles.
"These solar tornadoes are almost a thousand times faster than a terrestrial tornado and are very big," said Spiros Patsourakos, a researcher at George Mason University.
Scientists have known since the 1990s that jets of gas wider than North America were erupting from the sun's poles, but it is only now that they discovered these jets are rotating.
That's because a new pair of NASA satellites called STEREO allowed the features to be observed from two directions at once, revealing their three-dimensional structures.
"The main element [of the new observations] is that the erupting structures possess twist," said Patsourakos, who described his findings last week at an American Geophysical Union meeting in Fort Lauderdale, Florida.
(See striking images of the sun.)
That twist comes from the sun's magnetic field, said Etienne Pariat, also of George Mason University.
"The magnetic field lines act like a spring, which expands and jumps outward," said Pariat, who has used computer simulations to model the forces producing the jets.
The forces originate in the solar interior, he added, where the sun's rotation twists the magnetic field.
"But the twist cannot be stored, so it must be ejected."
Understanding these forces is important, Patsourakos added, because other solar phenomena can affect our lives here on Earth.
The jets may be a "Rosetta stone for understanding all kinds of ejections from the sun," he said.
The biggest and most dangerous of these events are massive solar storms called coronal mass ejections, which affect "space weather" by producing radiation that can extend all the way to Earth.
(Read: "Space Weather Forecast: More Solar Storms on the Way" [January 9, 2008].)
Their impacts range from vivid auroras to electromagnetic storms that can damage satellites. The radiation can also put astronauts at risk.
In another presentation at the Fort Lauderdale meeting, another team of scientists said they had found similar twisting in a recent coronal mass ejection.
Although such ejections are well studied, the twisting hadn't been seen before, partly because superbright solar flares make it difficult for satellite instruments to see their details.
But on April 9, 2008, the flare was out of sight, just around the edge of the sun.
This allowed the scientists' instruments to take detailed images of the ejection without being blinded by the flare itself. (Read about how satellites are probing secrets of the Sun.)
The new pictures provided "a beautiful view of the process," said Ed DeLuca, an astronomer at the Harvard-Smithsonian Center for Astrophysics.
This advantageous angle allowed instruments from the Japanese spacecraft Hinode to spot the twist.
Unlike the polar jets in which the twist appeared quite simple, the ejection twist proved to be much more complex, DeLuca said. Parts of it were rotating clockwise, while others were rotating counter-clockwise.
Nevertheless, DeLuca believes the twisting is due to similar mechanisms to those which cause the tornadoes to rotate.
The difference, he said, is that mass ejections are much larger with much more complex magnetic fields at their bases.
Also, the jets occur near the poles, where the background magnetic field is directed primarily up and down.
The mass ejections also occur closer to the sun's equator, where the background magnetic field is almost horizontal, producing much more complicated interactions.
DeLuca hopes that by comparing observations from multiple instruments, scientists will be able to determine the magnetic conditions at the sun's surface at the time of the ejection.
This would allow computer modelers such as Pariat to know what parameters to use for their simulations.
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