The General Circulation of the Solar Atmosphere and the Maintenance of the Equatorial Acceleration.

Many theories have been advanced to explain how the equatorial acceleration of the Sun originated or is maintained. These range from Cowling's "fossil" rotation theory which has the excess velocity left from the birth of the solar system, to Rander's conclusion that polar heating leads necessarily to an increase in rotational velocity toward the equatorial plane. But all these theories assume that the large- scale fluid motions are symmetric about the rotational axis. However, recent hydrodynamical model experiments show how rotation can significantly alter such motions. Consideration of the solar rotation and the magnitude and character of its latitudinal gradient leads to the more likely hypothesis that the general circulation of the solar atmosphere is not axially symmetric, but consists of wave motions, in which large components of fluid velocities are along spherical surfaces. These waves (or eddies) transport angular momentum equatorward from high latitudes along these spherical surfaces by horizontal exchange processes. The analysis of Greenwich sunspot data for one sunspot cycle (1935-1944) supported the above hypothesis. The data for two more sunspot cycles have now been analyzed and verifies the previous result in all major respects. Moreover, if the transport of angular momentum by these eddies were to cease and all other processes were to continue unabated, the zone between +2721 would go to solid rotation (at the velocity of its boundaries) in less than four solar rotations. These results also indicate the necessity for a re-evaluation of the solar rotation rate, and indicate that significant latitudinal drifts are confined to +51 of the solar equator.