Solar Physics

, Volume 137, Issue 1, pp 155–165 | Cite as

Fitting the sunspot cycles 10–21 by a modified F-distribution density function

  • W. Elling
  • H. Schwentek


It has been found that sunspot cycles 10–21, represented by quarterly mean values of Zürich sunspot number, can be suitably described by the F-distribution density function provided it is modified by introducing five characteristic parameters, in order to achieve an optimal fitting of each cycle. The average cycle calculated from cycles 10–21 has been used as a basis to forecast time and magnitude of the maximum of each cycle, as a function of various numbers of the first quarterly mean values in the beginning N = 8 to 16 quarters. The standard deviations at a 99% significance level calculated from the observed values depend on N, and vary from 1.6 to 1.1 quarters and 65 to 16 units of sunspot number. A rather sufficient forecast is obtained from N = 12 quarters (with inaccuracy of ± 1.5 quarters and ± 24 units); the forecast for cycle 22 yielded, for N = 12, the values t m = (15.4 ± 1.5) quarters (∼ 1990.I) and f(t m ) = (175 ±24 units).


Standard Deviation Density Function Characteristic Parameter Sunspot Number Sunspot Cycle 
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Copyright information

© Kluwer Academic Publishers 1992

Authors and Affiliations

  • W. Elling
    • 1
  • H. Schwentek
    • 1
  1. 1.Max-Planck-Institut für AeronomieKatlenburg-LindauGermany

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