Sunspot activity according to Greenwich observations

Kopecký, M.

doi:10.1007/bf00156663

Cited by 4 publications

(4 citation statements)

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“…Nagovitsyn et al (2019) suggested t life (days) ; 0.077S md (MSH), a slightly shorter lifetime for the specified S md compared that in Gnevyshev (1938), but this also gives large values of lifetimes. According to Kopecky (1984), the As will be discussed in Section 6.3, the gamma function model for F(Φ md ) described in Section 5.1 gives the instantaneous distributions of sunspot area or magnetic flux, which are consistent with the observed distributions only if the region lifetimes are much shorter; a reasonable value we found is (a, b) = (0.3, 20.0). The value of a is fixed to 0.3 because the rise time of region growth (;1/a) does not strongly depend on the region size.…”

Section: Modelsupporting

confidence: 71%

“…The latter may be an independent process from the dynamo. In the case of the Sun, the diffusive decay of sunspots leads to lifetimes of at most 7 months (Kopecky 1984). Under which conditions one may have larger starspots (stronger dynamo) or starspots living for many years (reduced diffusion) could be an important issue in understanding the nature of super-large starspots.…”

Section: Summary and Discussionmentioning

confidence: 99%

“…The lifetimes of the 500 and 6132 MSH regions in this model are 16 and 107 days, respectively. Figure 8 Kopecky (1984). The asterisks denote the lifetimes of maximum sunspot areas >3000 MSH taken from Spencer Jones (1955).…”

Section: Modelmentioning

confidence: 99%

“…The dotted lines denote the formulae given byGnevyshev (1938) andNagovitsyn et al (2019), respectively. The diamond signs and asterisks denote the lifetimes of regions taken from published data (Spencer Jones 1955;Kopecky 1984).…”

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confidence: 99%

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Probability Distribution Functions of Sunspot Magnetic Flux

Sakurai

Toriumi

2023

ApJ

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We investigated the probability distributions of sunspot area and magnetic flux by using data from the Royal Greenwich Observatory and USAF/NOAA. We constructed a sample of 2995 regions with maximum-development areas ≥500 MSH (millionths of solar hemisphere), covering 146.7 yr (1874–2020). The data were fitted by a power-law distribution and four two-parameter distributions (tapered-power-law, gamma, lognormal, and Weibull distributions). The power-law model was unfavorable compared to the four models in terms of AIC, and was not acceptable according to the classical Kolmogorov–Smirnov test. The lognormal and Weibull distributions were excluded because their behavior extended to smaller regions (S ≪ 500 MSH) do not connect to previously published results. Therefore, our choices were tapered-power-law and gamma distributions. The power-law portion of the tapered-power-law and gamma distributions was found to have a power exponent of 1.35–1.9. Due to the exponential falloff of these distributions, the expected frequencies of large sunspots are low. The largest sunspot group observed had an area of 6132 MSH, and the frequency of sunspots larger than 104 MSH was estimated to be every 3–8 × 104 yr. We also estimated the distributions of the Sun-as-a-star total sunspot areas. The largest total area covered by sunspots on record was 1.67% of the visible disk, and can be up to 2.7% by artificially increasing the lifetimes of large sunspots in an area evolution model. These values are still smaller than those found on active Sun-like stars.

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Section: Modelsupporting

confidence: 71%

Section: Summary and Discussionmentioning

confidence: 99%

Section: Modelmentioning

confidence: 99%

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confidence: 99%

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