Does Correction Factor Vary with Solar Cycle?

Chang, Heon-Young;Oh, Sung-Jin

  • Received : 2012.04.23
  • Accepted : 2012.05.09
  • Published : 2012.06.15


Monitoring sunspots consistently is the most basic step required to study various aspects of solar activity. To achieve this goal, the observers must regularly calculate their own correction factor $k$ and keep it stable. Relatively recently, two observing teams in South Korea have presented interesting papers which claim that revisions that take the yearly-basis $k$ into account lead to a better agreement with the international relative sunspot number $R_i$, and that yearly $k$ apparently varies with the solar cycle. In this paper, using artificial data sets we have modeled the sunspot numbers as a superposition of random noise and a slowly varying background function, and attempted to investigate whether the variation in the correction factor is coupled with the solar cycle. Regardless of the statistical distributions of the random noise, we have found the correction factor increases as sunspot numbers increase, as claimed in the reports mentioned above. The degree of dependence of correction factor $k$ on the sunspot number is subject to the signal-to-noise ratio. Therefore, we conclude that apparent dependence of the value of the correction factor $k$ on the phase of the solar cycle is not due to a physical property, but a statistical property of the data.


Sun;sunspot;data analysis


  1. Berghmans D, van der Linden RAM, Vanlommel P, Warnant R, Zhukov A, et al., Solar activity: nowcasting and forecasting at the SIDC, AnGeo, 23, 3115-3128 (2005).
  2. Chang H-Y, A new method for North-South asymmetry of sunspot area, JASS, 24, 261-268 (2007).
  3. Chang H-Y, Stochastic properties in North-South asymmetry of sunspot area, NewA, 13, 195-201 (2008).
  4. Clette F, Berghmans D, Vanlommel P, van der Linden RAM, Koeckelenbergh A, et al., From the Wolf number to the International Sunspot Index: 25 years of SIDC, AdSpR, 40, 919-928 (2007).
  5. Kim B-Y, Chang H-Y, Short periodicities in latitudinal variation of sunspots, JASS, 28, 103-108 (2011).
  6. Kim RS, Cho K-S, Park Y-D, Moon Y-J, Kim YH, et al., The relative sunspot numbers from 1987 to 2002, PKAS, 180, 25-35 (2003).
  7. Letfus V, Relative sunspot numbers in the first half of eighteenth century, SoPh, 194, 175-184 (2000).
  8. Lockwood M, Twenty-three cycles of changing open solar magnetic flux, JGR, 108, 1128-1142 (2003).
  9. Oh S-J, Chang H-Y, Relative sunspot number observed from 2002 to 2011 at Butterstar observatory, JASS, 29, 103-113 (2012).
  10. Petrovay K, Solar cycle prediction, LRSP, 7, 6-59 (2010).
  11. Pulkkinen PJ, Brooke J, Pelt J, Tuominen I, Long-term variation of sunspot latitudes, A&A, 341, L43-L46 (1999).
  12. Sim KJ, Kim KM, Park YD, Yoon HS, Analysis of the observational data of sunspots, PKAS, 5, 26-39 (1990).
  13. Solanki SK, Usoskin IG, Kromer B, Schussler M, Beer J, Unusual activity of the Sun during recent decades compared to the previous 11,000 years, Natur, 431, 1084-1087 (2004).
  14. Ternullo M, The butterfly diagram internal structure, Ap&SS, 328, 301-305 (2010).
  15. Usoskin IG, A history of solar activity over millennia, LRSP, 5, 3-88 (2008).
  16. Vaquero JM, Historical sunspot observations: a review, AdSpR, 40, 929-941 (2007).
  17. Wang Y-M, The Sun's large-scale magnetic field and its long-term evolution, SoPh, 224, 21-35 (2004).

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Supported by : National Research Foundation of Korea