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17 April 2014 12:48 pm ,
Vol. 344 ,
- 17 April 2014 12:48 pm , Vol. 344 , #6181
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ScienceShot: Massive 'Cells' Seen on Sun
5 December 2013 2:00 pm
Large flows of material that circulate heat from the sun’s interior to its surface, theorized since the late 1960s but never seen directly, have finally been spotted. Researchers have long known of smaller flows called granules (which last a few minutes and are typically about 1000 kilometers across) and supergranules (which last about 1 day and are usually about 30,000 km across). The new swirls, which roil the outermost 30% of the sun’s interior, are several hundreds of thousands of kilometers across and persist for several months, the researchers report online today in Science. The team analyzed space-based observations of the sun taken every 45 seconds for several years. After removing the effects of solar rotation and accounting for the angle of view of areas not facing directly toward Earth, the researchers could discern the so-called giant cell flow patterns (material moving east is depicted in red, that moving toward the west in blue), which cause supergranules to slowly drift across the surface of the sun. Flow speeds within the giant cells, akin to the convection that carries hot water from the bottom of a heated pan to the surface, are only a few meters per second, the researchers estimate. But the overall effects of these flows (such as the long, jet stream-like red swath in the sun’s northern hemisphere) are important. Among other things, giant cell circulation helps transport energy from the sun’s polar regions to its equator, where material rotates around the sun about 10 days faster than it does near the poles. The flows also substantially influence the structure and evolution of the sun’s magnetic field, the researchers suspect. Active regions on the solar surface, often the sources of solar flares, may form in areas where flows converge, causing magnetic fields to become concentrated.