Solar Polar Fields During Cycles 21 --- 23: Correlation with Meridional Flows

TL;DR

This study analyzes polar magnetic fields over solar cycles 21-23, revealing a significant decline correlated with meridional flow speeds, and discusses implications for solar cycle prediction and the prolonged minimum at cycle 24's start.

Contribution

It provides new insights into the correlation between polar magnetic fields and meridional flows during solar cycles 21-23, aiding in understanding and forecasting solar activity.

Findings

Significant drop in polar fields from cycle 22 to 23 maximum.

Strong correlation between polar field strength and meridional flow speeds.

Implications for predicting the prolonged minimum at cycle 24's start.

Abstract

We have examined polar magnetic fields for the last three solar cycles, {$\it{viz.}$}, cycles 21, 22 and 23 using NSO Kitt Peak synoptic magnetograms. In addition, we have used SoHO/MDI magnetograms to derive the polar fields during cycle 23. Both Kitt Peak and MDI data at high latitudes (78${^{\circ}}$--90${^{\circ}}$) in both solar hemispheres show a significant drop in the absolute value of polar fields from the late declining phase of the solar cycle 22 to the maximum of the solar cycle 23. We find that long term changes in the absolute value of the polar field, in cycle 23, is well correlated with changes in meridional flow speeds that have been reported recently. We discuss the implication of this in influencing the extremely prolonged minimum experienced at the start of the current cycle 24 and in forecasting the behaviour of future solar cycles.