Average properties of bipolar magnetic regions during sunspot cycle 21
Rent the article at a discountRent now
* Final gross prices may vary according to local VAT.Get Access
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.
- Babcock, H. W.: 1961, Astrophys. J. 133, 572.
- Babcock, H. W. and Babcock, H. D.: 1955, Astrophys. J. 121, 349.
- Brunner, W.: 1930, Astron. Mitteil. (Eidgen. Sternw., Zürich) 13, 67.
- Gaizauskas, V., Harvey, K. L., Harvey, J. W., and Zwaan, C.: 1983, Astrophys. J. 265, 1056.
- Hale, G. E., Ellerman, F., Nicholson, S. B., and Joy, A. H.: 1919, Astrophys. J. 49, 153.
- Harvey, K. L. and Martin, S. F.: 1973, Solar Phys. 32, 389.
- Howard, R. F.: 1989, Solar Phys. 123, 271.
- Kiepenheuer, K. O.: 1953, in G. P. Kuiper (ed.), The Sun, Univ. of Chicago Press, Chicago, p. 322.
- Leighton, R. B.: 1964, Astrophys. J. 140, 1547.
- Leighton, R. B.: 1969, Astrophys. J. 156, 1.
- Mattig, W.: 1953, Z. Astrophys. 31, 273.
- Mosher, J. M.: 1977, ‘The Magnetic History of Solar Active Regions’, Ph.D. Thesis, California Institute of Technology.
- Sheeley, N. R., Jr.: 1966, Astrophys. J. 144, 723.
- Sheeley, N. R., Jr.: 1981, in F. Q. Orrall (ed.), Solar Active Regions, Colorado Assoc. Univ. Press, Boulder, p. 17.
- Sheeley, N. R., Jr., DeVore, C. R., and Boris, J. P.: 1985, Solar Phys. 98, 219.
- Tang, F.: 1982, Solar Phys. 75, 179.
- Tang, F., Howard, R. F., and Adkins, J. M.: 1984, Solar Phys. 91, 75.
- Wang, Y.-M., Nash, A. G., and Sheeley, N. R., Jr.: 1989, Science 245, 712.
- Wang, Y.-M., Sheeley, N. R., Jr., Nash, A. G., and Shampine, L. R.: 1988, Astrophys. J. 288, 769.
- Weart, S. R.: 1970, Astrophys. J. 162, 987.
- Zirin, H.: 1988, Astrophysics of the Sun, Cambridge Univ. Press, Cambridge, p. 322.
- Average properties of bipolar magnetic regions during sunspot cycle 21
Volume 124, Issue 1 , pp 81-100
- Cover Date
- Print ISSN
- Online ISSN
- Kluwer Academic Publishers
- Additional Links