A Relationship between the Solar Rotation and Activity Analysed by Tracing Sunspot Groups

TL;DR

This study analyzes the relationship between solar rotation and activity over a long period, revealing inverse correlations and changes in differential rotation related to solar activity cycles.

Contribution

It provides a comprehensive analysis of long-term data linking solar differential rotation parameters with activity levels, highlighting new patterns and correlations.

Findings

Sun rotates more differentially at activity minima.

Inverse correlation between equatorial rotation and solar activity.

Secular decrease in equatorial rotation rate has halted.

Abstract

The sunspot position from Greenwich Photoheliographic Results (GPR), US Air Force Solar Optical Observing Network and National Oceanic and Atmospheric Administration (USAF/NOAA), and Debrecen Photoheliographic Data (DPD) data bases in the period 1874 to 2016 were used to calculate yearly values of the solar differential-rotation parameters $A$ and $B$. The calculated differential-rotation parameters were compared with the solar-activity level. We found that the Sun rotates more differentially at the minimum than at the maximum of activity during the 1977 - 2016 epoch. An inverse correlation between equatorial rotation and solar activity was found using the recently revised sunspot number. The secular decrease of equatorial rotation rate accompanying the increase of activity stopped in the last part of the 20th century. It was noted that when a significant peak of equatorial rotation velocity is observed during minimum of activity, the strength of the next maximum is smaller than the previous one.