Investigation of the Differential Rotation by Hα Filaments and Long-Lived Magnetic Features for Solar Activity Cycles 20 and 21

Abstract

For solar activity Cycles 20 and 21 (1966 – 1985) the solar differential rotation has been investigated using Hα filaments and relatively small-scale long-lived magnetic features with negative and positive polarities. We used annual averaged angular velocities of quiescent Hα filaments from Hα photoheliograms of the Abastumani Astrophysical Observatory film collection and selected long-lived magnetic features from the McIntosh atlas (McIntosh, Willock, and Thompson, Atlas of Stackplots, NGDC, 1991). We have determined coefficients of Faye’s formulas for Hα filaments as well as for long-lived magnetic features and have found that for Solar Cycles 20 and 21 the Hα filaments have lower rotation rates and rotated more differentially than the long-lived magnetic features.