Abstract
We analyze the record of facular areas compiled by the Royal Greenwich Observatory (RGO) from daily white-light observations between 1874 and 1976. Curiously, the relative amplitudes of the three largest sunspot cycles 17, 18, and 19 in this record are reversed when they are ranked by facular area. We show that this negative correlation arises from a general decrease of the ratioA F/A S, of facular to sunspot area, with increasingA S. Within a given cycle,A F/A Sdecreases in active regions of largeA S, butA F/A Sis also lower at allA S, in cycles of higher peak amplitude inA S. This decrease ofA F/A Sin large spot groups is consistent with its decrease in younger, more active solar-mass stars, and it may explain why stars only slightly more magnetically active than the Sun tend to exhibit much greater variability in broad-band photometry. We suggest that the physical explanation is an increased spatial filling factor of magnetic flux, favoring formation of sunspots over faculae. We also explain why the decrease inA F/ASis not seen in the disc-integrated Ca K plage areas, nor in theF10.7 microwave index, both of which exhibit remarkable linearity when plotted against smoothed sunspot area. This explanation suggests how complementary data on faculae and plages from RGO and Mt. Wilson could be used to improve empirical models of total irradiance variation, extending back to 1874.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Brown, G.: 1981,Solar Phys. 74, 125.
Brown, G. and Evans, D.: 1980a,Solar Phys. 66, 233.
Brown, G. and Evans, D.: 1980b,Solar Phys. 68, 141.
Donnelly, R.: 1986,Solar Phys. 109, 37.
Eddy, J.: 1983, in B. LaBonteet al. (eds.),Solar Irradiance Variations on Active Region Time Scales, NASA Conference Publication 2310, p. 213.
Foukal, P.: 1990,Solar Astrophysics, Wiley-Interscience, New York.
Foukal, P. and Lean, J.: 1988,Astrophys. J. 328, 347.
Foukal, P. and Lean, J.: 1990,Science 247, 505.
Foukal, P., Harvey, K., and Hill, F.: 1991,Astrophys. J. 383, L89.
Greenwich Observatory: 1923,Monthly Notices Roy. Astron. Soc. 84, 96.
Harvey, K.: 1992, private communication.
Howard, R.: 1991,Solar Phys. 131, 239.
Hoyt, D. and Eddy, J.: 1982, Tech Note TN-194 + STR National Center for Atm. Research, Boulder, CO.
Lawrence, J.: 1987,Solar Phys. 110, 73.
Lean, J.: 1992, private communication.
Lean, J.: 1987,J. Geophys. Res. 92, 839.
Lockwood, G., Skiff, B., Baliunas, S., and Radick, R.:: 1992,Nature 360, 653.
Marquette, W.: 1992, private communication.
Radick, R., Lockwood, W., and Baliunas, S.: 1991,Science 273, 39.
Schatten, K., Miller, N., Sofia, S., Endal, A., Chapman, G., and Hickey, J.: 1985,Astrophys. J. 294, 689.
Schrijver, C. and Harvey, K.: 1989,Astrophys. J. 343, 481.
Sheeley, N.: 1966,Astrophys. J. 144, 723.
Solar Geophysical Data (Descriptive Text): February, 1967, U.S. Department of Commerce EDS/ESSA publication, p. 8.
Swartz, W. and Overbeek, R.: 1971, Penn State University Scientific Report 373(E); PSU-IRL-SCI 373.
Tapping, K.: 1987,J. Geophys. Res. 92, 829.
Willson, R. and Hudson, H.: 1988,Nature 332, 810.
Zirin, H.: 1988,Astrophysics of the Sun, Cambridge University Press, Cambridge.
Zwaan, C.: 1981, in S. Jordan (ed.),The Sun as a Star, NASA Publication SP-450, p. 163.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Foukal, P. The curious case of the greenwich faculae. Sol Phys 148, 219–232 (1993). https://doi.org/10.1007/BF00645087
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF00645087