On the Long-Term Modulation of Solar Differential Rotation

TL;DR

This study analyzes long-term changes in solar differential rotation over multiple solar cycles, revealing periodic modulation and hemispheric differences that have implications for understanding the solar dynamo.

Contribution

It provides new insights into the long-term modulation patterns of solar differential rotation and hemispheric phase shifts over several solar cycles.

Findings

Global B-value modulates over six or seven cycles

Hemispheric B-values show quasi-oscillatory behavior with phase shifts

High B-values occur during full-cycle years when cycle-averaged B-values are high

Abstract

Long-term modulation of solar differential rotation was studied with data from Mt. Wilson and our original observations during Solar Cycles 16 through 23. The results are: i) The global B-value (i.e. latitudinal gradient of differential rotation), is modulated in a period of about six or seven solar cycles. ii) The B-values of the northern and southern hemispheres are also modulated with a similar period to the global one, but iii) they show quasi-oscillatory behavior with a phase shift between them. We examined the yearly fluctuations of the B-values in every solar cycle with reference to the phase of the sunspot cycle and found that the B-values show high values over the full-cycle years, when the cycle-averaged B-values are high. We discuss the independent long-term behavior of solar differential rotation between the northern and southern solar hemispheres and its implication for the solar dynamo.