Team spots waves that heat corona: find supports theory explaining why sun's atmosphere sizzles.
Magnetic waves theorized to transfer heat from the surface of the sun to its outer atmosphere have been directly observed for the first time, a team reports in the March 20 Science.
Physicists have long wondered why the sun's corona, the outer part of the solar atmosphere, is millions of degrees hotter than its surface. "It's counterintuitive," says study coauthor David Jess of Queen's University Belfast in Northern Ireland. "When you hold your hands in front of a fire, it's hottest closest to the flames."
The magnetic waves, called Alfven waves, are considered the most plausible explanation for the transfer of so much energy from the sun's surface to its corona. First theorized by Nobel laureate Hannes Alfven in 1942, the waves could carry energy several hundred thousand kilometers from the surface.
The new observation "means that we can get to the root of what's heating the corona," says Craig DeForest of the South west Research Institute in Boulder, Colo.
Alfven waves move along the sun's magnetic fields like "waves traveling along a string," Jess explains. The waves are created by magnetic reconnections--disturbances in the sun's magnetic field created when magnetic lines twist, break apart and then snap back together again.
Researchers have employed theoretical models to predict the waves' behavior. But in the new study, Jess and his colleagues used the Swedish 1-meter Solar Telescope to observe a highly magnetized bright point on the surface of the sun and measure the magnetic waves oscillating from that point. Data gathered by the team suggest that Alfven waves are energetic enough to heat the whole corona.
"The next logical step is to measure how much energy the waves produce at different places in the sun's atmosphere to figure out if Alfven waves are the dominant mechanism for heating the whole solar atmosphere," Jess says.
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|Title Annotation:||Atom & Cosmos|
|Article Type:||Brief article|
|Date:||Apr 11, 2009|
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