Sunspot Count Periodicities in Different Zurich Sunspot Group Classes since 1986

TL;DR

This study analyzes sunspot count periodicities across different sunspot group classes from 1986 to 2013 using advanced spectral methods, revealing consistent solar rotation periods and cycle-dependent behaviors that vary among groups.

Contribution

It introduces a comparative analysis of sunspot group classes' periodicities using multi-taper and wavelet methods, highlighting differences and cycle-related patterns.

Findings

Solar rotation periodicity of 25-37 days found in all groups

Periodic behavior correlates with cycle amplitude and group distribution

No significant periods during solar minimum phases

Abstract

In this study, we used two methods to investigate the periodic behavior of sunspot counts in four categories for the time period January 1986-October 2013. These categories include the counts from simple (A and B), medium (C), large (D, E, and F), and final (H) sunspot groups. We used: i) the Multi-taper Method with red noise approximation, and ii) the Morlet wavelet transform for periodicity analysis. Our main findings are: (1) the solar rotation periodicity of about 25 to 37 days, which is of obvious significance, is found in all groups with at least a 95% significance level; (2) the periodic behavior of a cycle is strongly related to its amplitude and group distribution during the cycle; (3) the appearance of periods follow the amplitude of the investigated solar cycles, (4) meaningful periods do not appear during the minimum phases of the investigated cycles. We would like to underline that the cyclic behavior of all categories is not completely the same; there are some differences between these groups. This result can provide a clue for the better understanding of solar cycles.