Strong evidence found for large-scale solar convection patterns

Nature : In 1801 William Herschel described patterns of convection on the surface of the Sun that were 1000 km across, later called granules. In the 1960s, 30 000-km supergranules were found, which led to the prediction of even bigger ones 200 000 km in size. Now, David Hathaway of NASA’s Marshall Space Flight Center in Huntsville, Alabama, and his colleagues have found the first strong evidence for the existence of those extra-large granules. Because of their size, the cells move very slowly—which makes them hard to discern. Hathaway’s team used the Solar Dynamics Observatory (SDO) to map the movement of the smaller granules, which revealed the large convection patterns that moved just 8 m/s and lasted for up to six months. The large structures may explain why the Sun’s equator rotates 30% faster than the poles: The motion of the plasma follows the direction of the Sun’s rotation, so it may add to the angular momentum at the equator. The structures may also be linked to the Sun’s internal magnetic fields and the formation of sunspots and solar flares.