The sub- and quasi-centurial cycles in solar and geomagnetic activity data series/v.3

TL;DR

This study investigates the existence and stability of solar and geomagnetic cycles ranging from 20 to 250 years using various data series and advanced time series analysis methods, revealing consistent multi-decadal and centurial cycles over the last millennium.

Contribution

It provides a comprehensive analysis of long-term solar and geomagnetic cycles, identifying stable multi-decadal and centurial oscillations across multiple data sets using wavelet and T-R periodogram methods.

Findings

A strong 55-60 year cycle is present in all data series.

Stable ~110-120 year and ~200-year cycles are identified.

A ~29-year cycle emerges after the 1898-1923 minimum.

Abstract

The subject of this paper is the existence and stability of solar cycles with durations in the range of 20-250 years. Five types of data series are used: 1) The Zurich series (1749-2009 AD), the mean annual International sunspot number Ri, 2) The Group sunspot number series Rh (1610-1995 AD), 3) The simulated extended sunspot Rsi number from Extended time series of Solar Activity Indices (ESAI) (1090-2002 AD), 4) The simulated extended geomagnetic aa-index from ESAI (1099-2002 AD), 5) The Meudon filament series (1919-1991 AD) (it is used only particularly). Data series are smoothed over 11 years and supercenturial trends are removed. Two principally independent methods of time series analysis are used: the T-R periodogram analysis (both in the standard and "scanning window" regimes) and the wavelet-analysis. The obtained results are very similar. It is found that in all series a strong cycle with mean duration of 55-60 years exists. It is very well expressed in the 18th and the 19th centuries. It is less pronounced during the end of the 19th and the beginning of the 20th centuries. On the other hand a strong and stable quasi 110-120 years and ~200-year cycles are obtained in all of these series except in Ri. In the last series a strong mean oscillation of ~ 95 years is found, which is absent in the other data sets. The analysis of the ESAI (1090-2002 AD) proved that the quasi century cycle has a relatively stable doublet (~80 and ~120 years) or triplet (~55-60, 80 and 120 years) structure during the last ~900 years. An interesting feature in all series is the existence of significant ~29-year cycle after the last centurial Gleissberg-Gnevishev's minimum (1898-1923 AD). Most probably the different types of oscillations in the sub-century and century period range correspond to cycles of different classes of active regions.