Sunspot Count Periodicities in Different Zurich Sunspot Group Classes Since 1986

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.

Temporal and Periodic Variations of Sunspot Counts in Flaring and Non-Flaring Active Regions

“…We detect a 45 day period from SSCs of flaring ARs of both solar cycle (Cycle 23 and 24). This periodicity also reported previously by different authors (Bai, 2003;Lou et al, 2003;Lara et al, 2008;Dimitropoulou, Moussas, and Strintzi, 2008;Kilcik et al, 2010Kilcik et al, , 2014bKilcik et al, , 2016, and reference therein). Lou et al (2003) investigate periodicities of X-Ray solar flares by using Fourier power spectral analyses method and Morlet wavelet analysis from 1999 to 2003 and found about 42 days period.…”

“…We detected 72 and 54-56 day periods from only non-flaring ARs of current cycle 24. Those periods are also reported in the literature by different authors (Zieba et al, 2001;Bai, 2003;Ozguc, Atac, and Rybak, 2003;Dimitropoulou, Moussas, and Strintzi, 2008;Kilcik et al, 2010;Chowdhury, Jain, and Awasthi, 2013;Kilcik et al, 2014bKilcik et al, , 2016, and reference therein). Kilcik et al (2010) analyzed the periodicity of H-alpha flare index data for the solar cycle 21, 22, and 23.…”

“…They investigated the cyclic variation of whole data and each cycle (Cycle 21, 22, and 23) separately and found a 113 day period from whole and cycle 23 data. Later, Kilcik et al (2014b) found this period in the SSCs of the simple and final groups. We found that this periodicity only appears in the flaring ARs of solar cycle 23.…”

“…Scafetta and Willson (2013)analyzed the TSI data by using a multiscale dynamical spectral analysis technique from 2003.15 to 2013.16 (descending phase of Cycle 23 and ascending phase of Cycle 24) and detected a 73 day period. Recently, Kilcik et al (2014b) analyzed the periodic variations of SSCs in different categories and found these two periodicities; a 73 day periodicity found in all categories except final (H groups) ones, and a 53 day periodicity detected in all categories. Note that about 55 day period exist in all situations but their significance level just below the 95% confidence level, also it appears in the wavelet scalograms.…”

Short-Term Variations in the Equatorial Rotation Rate of Sunspot Groups

“…In addition to the well-known 11-year solar cycle, solar activity varies on many shorter and longer timescales. For example, periodicities shorter than a year and of about two years are found in many solar activity indices (Rieger et al, 1984;Lean and Brueckner, 1989;Pap, Bouwer, Tobiska, 1990;Bai and Sturrock, 1991;Bouwer, 1992;Richardson et al, 1994;Krivova and Solanki, 2002;Özgüc, Atac, and Rybák, 2003;Kane, 2003;Bai, 2003;Obridko and Shelting, 2000;Obridko and Shelting, 2007;Chowdhury, Khan, and Ray, 2009;Scafetta and Willson, 2013;Kilcik et al, 2014;Chowdhury et al, 2016;and references therein). Studies of similar variations in the solar rotation data may help us to better understand the physical processes responsible for the solar variability.…”