Advertisement

Solar Physics

, Volume 124, Issue 1, pp 81–100 | Cite as

Average properties of bipolar magnetic regions during sunspot cycle 21

  • Y. -M. Wang
  • N. R. SheeleyJr.
Article

Abstract

We examine the statistical properties of some 2700 bipolar magnetic regions (BMRs) with magnetic fluxes ≥3 × 1020 Mx which erupted during 1976–1986. Empirical rules were used to estimate the fluxes visually from daily magnetograms obtained at the National Solar Observatory/Kitt Peak. Our analysis shows the following: (i) the average flux per BMR declined between 1977 and 1985; (ii) the average tilts of BMRs relative to the east-west line increase toward higher latitudes; (iii) weaker BMRs had larger root-mean-square tilt angles than stronger BMRs at all latitudes; (iv) over the interval 1976–1986, BMRs with their leading poles equatorward of their trailing poles contributed a total of 4 times as much flux as BMRs with ‘inverted’ tilts, but the relative amount of flux contributed by BMRs with inverted or zero tilts increased as the sunspot cycle progressed; (v) only 4% of BMRs had ‘reversed’ east-west polarity orientations; (vi) although the northern hemisphere produced far more flux during the rising phase of the sunspot cycle, the southern hemisphere largely compensated for this imbalance during the declining phase; (vii) southern-hemisphere BMRs erupted at systematically higher latitudes than northern-hemisphere ones through most of sunspot cycle 21.

Keywords

Magnetic Flux Average Property Sunspot Cycle Empirical Rule Magnetic Region 
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.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Babcock, H. W.: 1961, Astrophys. J. 133, 572.Google Scholar
  2. Babcock, H. W. and Babcock, H. D.: 1955, Astrophys. J. 121, 349.Google Scholar
  3. Brunner, W.: 1930, Astron. Mitteil. (Eidgen. Sternw., Zürich) 13, 67.Google Scholar
  4. Gaizauskas, V., Harvey, K. L., Harvey, J. W., and Zwaan, C.: 1983, Astrophys. J. 265, 1056.Google Scholar
  5. Hale, G. E., Ellerman, F., Nicholson, S. B., and Joy, A. H.: 1919, Astrophys. J. 49, 153.Google Scholar
  6. Harvey, K. L. and Martin, S. F.: 1973, Solar Phys. 32, 389.Google Scholar
  7. Howard, R. F.: 1989, Solar Phys. 123, 271.Google Scholar
  8. Kiepenheuer, K. O.: 1953, in G. P. Kuiper (ed.), The Sun, Univ. of Chicago Press, Chicago, p. 322.Google Scholar
  9. Leighton, R. B.: 1964, Astrophys. J. 140, 1547.Google Scholar
  10. Leighton, R. B.: 1969, Astrophys. J. 156, 1.Google Scholar
  11. Mattig, W.: 1953, Z. Astrophys. 31, 273.Google Scholar
  12. Mosher, J. M.: 1977, ‘The Magnetic History of Solar Active Regions’, Ph.D. Thesis, California Institute of Technology.Google Scholar
  13. Sheeley, N. R., Jr.: 1966, Astrophys. J. 144, 723.Google Scholar
  14. Sheeley, N. R., Jr.: 1981, in F. Q. Orrall (ed.), Solar Active Regions, Colorado Assoc. Univ. Press, Boulder, p. 17.Google Scholar
  15. Sheeley, N. R., Jr., DeVore, C. R., and Boris, J. P.: 1985, Solar Phys. 98, 219.Google Scholar
  16. Tang, F.: 1982, Solar Phys. 75, 179.Google Scholar
  17. Tang, F., Howard, R. F., and Adkins, J. M.: 1984, Solar Phys. 91, 75.Google Scholar
  18. Wang, Y.-M., Nash, A. G., and Sheeley, N. R., Jr.: 1989, Science 245, 712.Google Scholar
  19. Wang, Y.-M., Sheeley, N. R., Jr., Nash, A. G., and Shampine, L. R.: 1988, Astrophys. J. 288, 769.Google Scholar
  20. Weart, S. R.: 1970, Astrophys. J. 162, 987.Google Scholar
  21. Zirin, H.: 1988, Astrophysics of the Sun, Cambridge Univ. Press, Cambridge, p. 322.Google Scholar

Copyright information

© Kluwer Academic Publishers 1989

Authors and Affiliations

  • Y. -M. Wang
    • 1
  • N. R. SheeleyJr.
    • 1
  1. 1.E.O. Hulburt Center for Space Research, Naval Research LaboratoryWashington, DCU.S.A.

Personalised recommendations