Large-Scale Solar Cycle Features of Photospheric Magnetic Flux

Abstract

It is well accepted that the solar cycle originates from a magnetohydrodynamics dynamo deep inside the Sun. Many dynamo models have long been proposed based on a lot of observational constraints. In this Letter, using 342 NSO/Kitt Peak solar synoptic charts, we study the large-scale solar cycle features of photospheric magnetic flux to set further constraints. (1) We find the mean latitudes () of the boundaries of the polar regions to be near 5535 during solar minimums and 6761 during solar maximums. There is a good correlation between the variability of its area and the sunspot number with a time lag of 5 years. (2) A unipolar poleward flow is found in the high-latitude region (|| [40°, 60°]) during solar maximums because of the different gradients between the positive flux and the negative flux in the active belts from || = 20° to || = 40°. (3) The flux peak time keeps steady from || = 40° to || = 20° and then shifts forward with a speed of 32.2 day deg-1 toward the equator. At the same time, the total magnetic flux increases with an average gradient of -2.48 × 1020 Mx deg-1 and then decreases with an average gradient of 3.63 × 1020 Mx deg-1. (4) The latitude migration of photospheric magnetic flux that represents the Sporer law is no different from that of the sunspot groups found by Li et al. These typical characteristics may provide us with hints for constructing a more reliable solar dynamo.