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.

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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.

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