2018
DOI: 10.1051/0004-6361/201833924
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Principal component analysis of sunspot cycle shape

Abstract: Aims. We study the shape of sunspot cycles using the Wolf sunspot numbers and group sunspot numbers of solar cycles 1-23. We determine the most typical "model" cycles and the most asymmetric cycles, and test the validity of the two Waldmeier rules: the anti-correlation between cycle height and the length of its ascending phase (rule 1), and between cycle height and the length of the preceding cycle (rule 2). Methods. We applied the principal component analysis to sunspot cycles and studied the first two compon… Show more

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Cited by 24 publications
(25 citation statements)
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“…The temporal evolution of sunspot areas shows a lack of large sunspots for four years (exactly between 4.2 -4.5 years), i.e., about 40% after the start of the cycle. This is related to the Gnevyshev gap and is consistent with the earlier result by Takalo and Mursula (2018). The significance level of this gap for even cycles is at least 95% for all sunspots and still higher (99%) for large sunspots.…”
Section: Resultssupporting
confidence: 92%
See 1 more Smart Citation
“…The temporal evolution of sunspot areas shows a lack of large sunspots for four years (exactly between 4.2 -4.5 years), i.e., about 40% after the start of the cycle. This is related to the Gnevyshev gap and is consistent with the earlier result by Takalo and Mursula (2018). The significance level of this gap for even cycles is at least 95% for all sunspots and still higher (99%) for large sunspots.…”
Section: Resultssupporting
confidence: 92%
“…c) Same as a) but for sunspots of odd cycles in the range SC13 -23 and d) same as c) but for odd cycles. Bazilevskaya, Makhmutov, and Sladkova, 2006;Norton and Gallagher, 2010;Du, 2015;Takalo and Mursula, 2018). The distribution of odd cycles has only a small decrease in the distribution at 4.2 -4.3 years, but it is insignificant according to two-sided T-test analysis (p = 0.40).…”
Section: Two-sample T-testmentioning
confidence: 89%
“…The solar cycle has basically three phases: an ascending phase, a descending phase, and between them a so-called Gnevyshev gap (GG: Antalova and Gnevyshev, 1965; Gnevyshev, B J. Takalo jojuta@gmail.com 1 Space Physics and Astronomy Research Unit, University of Oulu, POB 3000, 90014, Oulu, Finland 1967Feminella and Storini, 1997;Storini et al, 2003;Ahluwalia and Kamide, 2004;Kane, 2005;Bazilevskaya, Makhmutov, and Sladkova, 2006;Kane, 2008;Norton and Gallagher, 2010;Du, 2015;Takalo and Mursula, 2018), which is a kind of separatrix between the first two (main) phases. The time of the Gnevyshev gap is 45 -55 months after the start of the nominal cycle, that is, approximately 33 -42% into the cycle after its start (Takalo and Mursula, 2018). Storini et al (2003) gave a review of the effects of the GG in different space-weather parameters.…”
Section: Introductionmentioning
confidence: 99%
“…The solar cycle has been modelled with many different mathematical formulations accounting for their asymmetry (Nordemann 1992;Elling & Schwentek 1992;Hathaway et al 1994;Volobuev 2009;Du 2011). Takalo & Mursula (2018) applied the Principal Component Analysis to the solar cycle and divided it into two components, an average cycle component, which always has the same shape, with varying period and amplitude, and one component varying from cycle to cycle.…”
Section: Introductionmentioning
confidence: 99%