NASA’s Dr. David Hathaway has just published a new paper, and it has advanced solar science. He’s found something they’ve been looking for a long time; long lived convection cells. Massive, long-lasting plasma flows 15 times the diameter of Earth transport heat from the sun’s depths to its surface, according to a study in the Dec. 6 Science. The finding supports a decades-old explanation of why the sun rotates fastest at its equator.
Convection motions within the Sun transport heat from its interior to its surface. The hot regions are seen as granular (∼1000 kilometers across) and supergranular (∼30,000 kilometers across) cells in the Sun. Using data from the Helioseismic Magnetic Imager on the Solar Dynamics Observatory, Hathaway et al. (p. 1217) found evidence for even larger cells that have long been predicted by theory but not unambiguously detected. The flows associated with these giant cells transport angular momentum toward the equator and are important for maintaining the Sun’s equatorial rotation.
GO WITH THE FLOW Long-lasting plasma flows appear in red and blue in this animation, which portrays data from four solar rotations. Some flows persist for several months; these patterns are especially visible near the sun’s north pole. Scientists think these flows keep the sun’s equator rotating faster than its poles.
Giant Convection Cells Found on the Sun
1NASA Marshall Space Flight Center, Huntsville, AL 35812, USA.
2Department of Physics and Astronomy, Vanderbilt University, Nashville, TN 37235, USA.
3Department of Space Science, University of Alabama in Huntsville, Huntsville, AL 35899, USA.
4Department of Physics and Astronomy, University of Rochester, Rochester, NY 14627, USA.
Heat is transported through the outermost 30% of the Sun’s interior by overturning convective motions. These motions are evident at the Sun’s surface in the form of two characteristic cellular structures: granules and supergranules (~1000 and ~30,000 kilometers across, respectively). The existence of much larger cells has been suggested by both theory and observation for more than 45 years. We found evidence for giant cellular flows that persist for months by tracking the motions of supergranules. As expected from the effects of the Sun’s rotation, the flows in these cells are clockwise around high pressure in the north and counterclockwise in the south and transport angular momentum toward the equator, maintaining the Sun’s rapid equatorial rotation.