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

TL;DR

This study compares the differential rotation of H-alpha filaments and magnetic features during solar cycles 20 and 21, revealing that filaments rotate more differentially and at lower rates than magnetic features.

Contribution

It provides new insights into the differential rotation characteristics of different solar features across two solar cycles.

Findings

H-alpha filaments have lower rotation rates than magnetic features.

Filaments exhibit more differential rotation than magnetic features.

The study uses historical data from observatories and atlases.

Abstract

For solar activity cycles 20 and 21 (1966-1985) the solar differential rotation has been investigated using H{\alpha} filaments and relatively small-scale long-lived magnetic features with negative and positive polarities. We used annual averaged angular velocities of quiescent H{\alpha} filaments from H{\alpha} 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 H{\alpha} filaments as well as for long-lived magnetic features and have found that for solar cycles 20 and 21 the H{\alpha} filaments have lower rotation rates and rotated more differentially than the long-lived magnetic features.