Solar Physics

, Volume 211, Issue 1–2, pp 357–370 | Cite as

Group Sunspot Numbers: Sunspot Cycle Characteristics

  • David H. Hathaway
  • Robert M. Wilson
  • Edwin J. Reichmann


We examine the `Group' sunspot numbers constructed by Hoyt and Schatten to determine their utility in characterizing the solar activity cycle. We compare smoothed monthly Group sunspot numbers to Zürich (International) sunspot numbers, 10.7-cm radio flux, and total sunspot area. We find that the Zürich numbers follow the 10.7-cm radio flux and total sunspot area measurements only slightly better than the Group numbers. We examine several significant characteristics of the sunspot cycle using both Group numbers and Zürich numbers. We find that the `Waldmeier Effect' – the anti-correlation between cycle amplitude and the elapsed time between minimum and maximum of a cycle – is much more apparent in the Zürich numbers. The `Amplitude–Period Effect' – the anti-correlation between cycle amplitude and the length of the previous cycle from minimum to minimum – is also much more apparent in the Zürich numbers. The `Amplitude–Minimum Effect' – the correlation between cycle amplitude and the activity level at the previous (onset) minimum is equally apparent in both the Zürich numbers and the Group numbers. The `Even–Odd Effect' – in which odd-numbered cycles are larger than their even-numbered precursors – is somewhat stronger in the Group numbers but with a tighter relationship in the Zürich numbers. The `Secular Trend' – the increase in cycle amplitudes since the Maunder Minimum – is much stronger in Group numbers. After removing this trend we find little evidence for multi-cycle periodicities like the 80-year Gleissberg cycle or the two- and three-cycle periodicities. We also find little evidence for a correlation between the amplitude of a cycle and its period or for a bimodal distribution of cycle periods. We conclude that the Group numbers are most useful for extending the sunspot cycle data further back in time and thereby adding more cycles and improving the statistics. However, the Zürich numbers are slightly more useful for characterizing the on-going levels of solar activity.


Solar Activity Sunspot Number Cycle Period Group Sunspot Group Number 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.


Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.


  1. Ahluwalia, H. S.: 1998, J. Geophys. Res. 103, 12 103.Google Scholar
  2. Baiada, E. and Merighi, R.: 1982, Solar Phys. 77, 357.Google Scholar
  3. Baliunas, S. and Soon, W.: 1995, Astrophys. J. 450, 896.Google Scholar
  4. Chernosky, E. J.: 1954, Publ. Astron. Soc. Pacific 66, 241.Google Scholar
  5. Eddy, J. A.: 1980, in R. O. Pepin, J. A. Eddy, and R. B. Merrill (eds.), The Ancient Sun, Pergamon Press, New York, p. 119.Google Scholar
  6. Friis-Christensen, E. and Lassen, K.: 1991, Science 254, 698.Google Scholar
  7. Gleissberg, M. N.: 1939, The Observatory 62, 158.Google Scholar
  8. Gnevyshev, M. N. and Ohl, A. I.: 1948, Astron. Zh. 25, 18.Google Scholar
  9. Hathaway, D. H., Wilson, R. M., and Reichmann, E. J.: 1999, J. Geophys. Res. 104, 22 375.Google Scholar
  10. Howard, R. F., Gilman, P. A., and Gilman, P.: 1984, Astrophys. J. 283, 373.Google Scholar
  11. Hoyt, D. V. and Schatten, K. H.: 1995a, Solar Phys. 160, 371.Google Scholar
  12. Hoyt, D. V. and Schatten, K. H.: 1995b, Solar Phys. 160, 379.Google Scholar
  13. Hoyt, D. V. and Schatten, K. H.: 1995c, Solar Phys. 160, 387.Google Scholar
  14. Hoyt, D. V. and Schatten, K. H.: 1995d, Solar Phys. 160, 393.Google Scholar
  15. Hoyt, D. V. and Schatten, K. H.: 1997, The Role of the Sun in Climate Change, Oxford University Press, New York, 279 pp.Google Scholar
  16. Hoyt, D. V. and Schatten, K. H.: 1998a, Solar Phys. 179, 189.Google Scholar
  17. Hoyt, D. V. and Schatten, K. H.: 1998b, Solar Phys. 181, 491.Google Scholar
  18. Hoyt, D. V., Schatten, K. H., and Nesmes-Ribes, E.: 1994, Geophys. Res. Lett. 21, 2067.Google Scholar
  19. Kiepenheuer, K. O.: 1953, in Kuiper, G. P. (ed.) The Sun, The University of Chicago Press, Chicago, p. 322.Google Scholar
  20. McKinnon, J. A.: 1987, Rep. UAG-95, World Data Ctr. A for Solar-Terr. Phys., Boulder, 112 pp.Google Scholar
  21. Rabin, D., Wilson, R. M., and Moore, R. L.: 1986, Geophys. Res. Lett. 13, 352.Google Scholar
  22. Vitinskii, Yu. I.: 1965, Solar Activity Forecasting, NASA TTF-289, NASA, Washington, D.C., 129 pp.Google Scholar
  23. Waldmeier, M.: 1935, Astron. Mitt. Zürich 14, 105.Google Scholar
  24. Waldmeier, M.: 1939, Astron. Mitt. Zürich 14, 439 and 470.Google Scholar
  25. Waldmeier, M.: 1961, The Sunspot-Activity in the Years 1610–1960, Schulthess, Zürich, Switzerland, 171 pp.Google Scholar
  26. Wilson, R. M.: 1987, J. Geophys.Res. 92, 10 101.Google Scholar
  27. Wilson, R. M.: 1988, Solar Phys. 115, 397.Google Scholar
  28. Wilson, R. M.: 1992, Solar Phys. 140, 181.Google Scholar
  29. Wilson, R. M.: 1998a, J. Geophys. Res. 103, 11 159.Google Scholar
  30. Wilson, R. M.: 1998b, Solar Phys. 182, 217.Google Scholar
  31. Wilson, R. M., Hathaway, D. H., and Reichmann, E. J.: 1998, J. Geophys. Res. 103, 6595.Google Scholar

Copyright information

© Kluwer Academic Publishers 2002

Authors and Affiliations

  • David H. Hathaway
    • 1
  • Robert M. Wilson
    • 1
  • Edwin J. Reichmann
    • 1
  1. 1.NASA/Marshall Space Flight CenterHuntsvilleU.S.A

Personalised recommendations