Latitudinal Distribution of Sunspots Revisited

Cho, Il-Hyun; Chang, Heon-Young

doi:10.5140/jass.2011.28.1.001

Cited by 16 publications

(6 citation statements)

References 78 publications

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“…The sunspot numbers form the longest directly observed index of solar activity allowing us to study its variations. The observed sunspot numbers depict well-known the 11-year cycle, namely the Schwabe cycle (Cho & Chang 2011, Kim & Chang 2011. It is evident that the sunspot cycle is rather irregular (for a comprehensive discussion, see Petrovay 2010).…”

Section: Introductionsupporting

confidence: 52%

Maximum Sunspot Numbers and Active Days

Chang¹

2013

Journal of Astronomy and Space Sciences

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Parameters associated with solar minimum have been studied to relate them to solar activity at solar maximum so that one could possibly predict behaviors of an upcoming solar cycle. The number of active days has been known as a reliable indicator of solar activity around solar minimum. Active days are days with sunspots reported on the solar disk. In this work, we have explored the relationship between the sunspot numbers at solar maximum and the characteristics of the monthly number of active days. Specifically, we have statistically examined how the maximum monthly sunspot number of a given solar cycle is correlated with the slope of the linear relationship between monthly sunspot numbers and the monthly number of active days for the corresponding solar cycle. We have calculated the linear correlation coefficient r and the Spearman rank-order correlation coefficient r s for data sets prepared under various conditions. Even though marginal correlations are found, they turn out to be insufficiently significant (r ~ 0.3). Nonetheless, we have confirmed that the slope of the linear relationship between monthly sunspot numbers and the monthly number of active days is less steep when solar cycles belonging to the "Modern Maximum" are considered compared with rests of solar cycles. We conclude, therefore, that the slope of the linear relationship between monthly sunspot numbers and the monthly number of active days is indeed dependent on the solar activity at its maxima, but that this simple relationship should be insufficient as a valid method to predict the following solar activity amplitude.

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Section: Introductionsupporting

confidence: 52%

Maximum Sunspot Numbers and Active Days

Chang¹

2013

Journal of Astronomy and Space Sciences

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“…The asymmetrical distribution of solar activity represents an important detail in solar dynamics, which is related to research about the genesis of the solar cycle and related activity. The N-S asymmetries of different solar activities, such as sunspot numbers, sunspot group numbers, sunspot areas, numbers of flares, the flare index, filaments, radio bursts, coronal holes, coronal mass ejections, photospheric magnetic fields, faculae, and green corona intensity, have been extensively studied by various authors (Oliver & Ballester 1994;Atac ¸& Özgüc ¸1996;Verma 1987;Gao et al 2007Gao et al , 2009Li et al 2002Li et al , 2003Zhang et al 2007;Yan et al 2008;Cho & Chang 2011;Deng et al 2011aDeng et al , 2012Xie et al 2012). These studies have indicated that the N-S asymmetry of solar activities is a real phenomenon and is not due to random fluctuations (for details, see Vizoso & Ballester 1990;Li et al 2002;Carbonell et al 2007).…”

Section: Introductionmentioning

confidence: 99%

Long-term hemispheric variation of the flare index

Feng¹,

Deng²,

Xu³

2013

Res. Astron. Astrophys.

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The long-term hemispheric variation of the flare index is investigated. It is found that, (1) the phase difference of the flare index between the northern and southern hemispheres is about 6–7 months, which is near the time delay between flare activity and sunspot activity; (2) both the dominant and phase-leading hemisphere of the flare index is the northern hemisphere in the considered time interval, implying that the hemispheric asynchrony of solar activity has a close connection with the N-S asymmetry of solar activity.

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“…In this paper, we take the area of sunspots into account in the latitudinal solar-cyclic behavior of sunspots (Cho & Chang 2011). This consideration is required, as it reduces the noise level of a power spectrum in the sense that small sunspots prevail in the butterfly diagram, which scatter over wider latitude ranges than larger ones.…”

Section: Center-of-latitude Of Sunspot and Wavelet Analysismentioning

confidence: 99%

Short Periodicities in Latitudinal Variation of Sunspots

Kim¹,

Chang²

2011

Journal of Astronomy and Space Sciences

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The latitudinal variation of sunspots appearing during the period from 1874 to 2009 has been studied in terms of centerof-latitude (COL). The butterfly diagram has been used to study the evolution of the magnetic field and the dynamics at the bottom of the solar convection zone. Short-term periodicities have been of particular interest, in that they are somehow related to the structure and dynamics of the solar interior. We thus have focused our investigation on shortterm periodicities. We first calculated COL by averaging the latitude of sunspots with the weight function in area. Then, we analyzed the time series of COL using the wavelet transform technique. We found that a periodicity of ~5 years is the most dominant feature in the time series of COL, with the exception of the ~11 year solar cycle itself. This periodicity can be easily understood by considering small humps between the minima in the area-weighted butterfly diagram. However, we find that periodicities of ~1.3 (0.064), ~1.5 (0.056), or ~1.8 (0.046) years (1 month), which have been previously suggested as evidence of links between the changing structure of the sunspot zone and the tachocline rotation rate oscillations, are insignificant and inconsistent. We therefore conclude that the only existing short-term periodicity is of ~5 years, and that periodicities of ~1.3, ~1.5, or ~1.8 years are likely to be artifacts due to random noise of small sunspots.

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Latitudinal Distribution of Sunspots Revisited

Cited by 16 publications

References 78 publications

Maximum Sunspot Numbers and Active Days

Maximum Sunspot Numbers and Active Days

Long-term hemispheric variation of the flare index

Short Periodicities in Latitudinal Variation of Sunspots

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