Long-term variations in the north-south asymmetry of solar activity and solar cycle prediction, III: prediction for the amplitude of solar cycle 25

TL;DR

This study analyzes long-term sunspot data to identify periodicities and correlations that enable prediction of solar cycle 25's amplitude, estimating it to be about 31% lower than cycle 24.

Contribution

It introduces a method linking sunspot group areas in specific latitudes to solar cycle amplitudes, providing a new approach for solar activity prediction.

Findings

Identified ~9-year and ~12-year periodicities in sunspot area differences.

Found a high correlation (85%) between southern hemisphere sunspot areas and future sunspot numbers.

Predicted solar cycle 25 amplitude to be approximately 50 ± 10.

Abstract

The combined Greenwich and Solar Optical Observing Network (SOON) sunspot group data during 1874-2013 are analyzed and studied the relatively long-term variations in the annual sums of the areas of sunspot groups in 0-10 deg, 10-20 deg, and 20-30 deg latitude intervals of the Sun's northern and southern hemispheres. The variations in the corresponding north-south differences are also studied. Long periodicities in these parameters are determined from the fast Fourier transform (FFT), maximum entropy method (MEM), and Morlet wavelet analysis. It is found that in the difference between the sums of the areas of the sunspot groups in 0-10 deg latitude intervals of northern and southern hemispheres, there exist ~9-year periodicity during the high activity period 1940-1980 and ~12-year periodicity during the low activity period 1890-1939. It is also found that there exists a high correlation (85% from 128 data points) between the sum of the areas of the sunspot groups in 0-10 deg latitude interval of the southern hemisphere during a Qth year (middle year of 3-year smoothed time series) and the annual mean International Sunspot Number (Rz) of (Q+9)th year. Implication of these results is discussed in the context of solar activity prediction and predicted 50 + or - 10 for the amplitude of solar cycle 25, which is about 31% lower than the amplitude of cycle 24.