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"Corkscrew" Waves Seen on Sun -- Keys to Solar Mystery?

Anne Minard
for National Geographic News
March 19, 2009
 
New pictures have revealed that mysterious "corkscrew" waves appear to be pushing heat from the sun's surface to its outer atmosphere.

The discovery could help solve the long-standing puzzle of how the sun is able to heat its atmosphere to millions of degrees hotter than its surface, a new study says.

And here on Earth, the finding may one day lead to more sustainable energy sources, the researchers say.

The team used the Swedish Solar Telescope in the Canary Islands (see map) to watch the motion of bright spots in the sun's atmosphere that correspond to the release of millions of degrees of heat.

"These are vast, vast areas on the surface of the sun," said study co-author David Jess, a solar physicist at Queen's University Belfast in Ireland.

Each spot spans about 267,190 square miles (430,000 square kilometers), Jess said—twice the size of the United Kingdom, but minuscule compared with the total area of the sun.

The spots are common over the sun's surface, especially during energetic phases of the star's 11-year cycles of high and low activity, Jess said.

Each bright spot represents a place where the sun's magnetic field lines form clusters that guide so-called Alfvén waves into the atmosphere, the researchers say.

First proposed in the 1940s, Alfvén waves were finally detected in 2007, in solar plasmas. But a mystery remained: Are the observed waves purely magnetic or magneto-acoustic?

Magnetic waves would move in a corkscrew fashion, while magneto-acoustic waves would move back and forth like sound waves from a plucked guitar string.

The waves seen by the team traveled at more than twice the speed of sound, moving through the sun's surface layers for just a few moments, on average, before spilling their energy into the thin outer layers of the atmosphere.

This creates the bright spots, which twisted left and right like corkscrews, Jess said—possibly proving that Alfvén waves are magnetic.

The finding may eventually allow scientists to use Alfvén waves to revolutionize Earth's energy needs.

Now that we know how the sun uses Alfvén waves, Jess said, we may be able to reproduce them in power plants to distribute energy from fusion—an as-yet uncontrollable form of nuclear power created when two atoms fuse together.

Findings published in the March 20 issue of the journal Science.
 

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