Abstract
As a first step in constructing three-dimensional decaying sunspot models we select the relevant observational data. From these we conclude:
-
(i)
sunspots, except the smallest, obey a radial and evolutionary similarity;
-
(ii)
sunspots may be considered as isolated, fairly well defined flux tubes, wrapped in thin current sheets;
-
(iii)
a substantial number among stable regular spots show a phase of slowest decay whose rate is independent of the spot's area.
Arguments are given that the slowest rate of decay is ultimately determined by Ohmic dissipation in the inner part of the current sheet. Preliminary asymptotic models for the deep layers (deeper than 2000 km below the photosphere) are given which satisfy the above three constraints. To meet the observed rate of slowest decay the current sheet has to be very thin, about 10−5 to 10−4 times the umbral radius.
Radial large-scale fluid motions are required in the current sheet to maintain the similarity of the structure. The radial motions are linked with the vertical motions which may be connected with the Evershed flow.
Finally we discuss details which are less relevant in the large-scale structure of stable sunspots, such as fine structures, twists, the break-down of the similarity and the relation between sunspots and smaller magnetic structures, and the intrinsic scatter in some observed quantities.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Adam, M. G.: 1969, Monthly Notices Roy. Astron. Soc. 145, 1.
Beckers, J. M. and Schröter, F. H.: 1969, Solar Phys. 10, 384.
Bray, R. J. and Loughhead, R. E.: 1964, Sunspots, Chapman and Hall, London.
Broxon, J. W.: 1949, Phys. Rev. 75, 606.
Bumba, V.: 1963, Bull. Astron. Inst. Czech. 14, 91.
Chitre, S. M.: 1963, Monthly Notices Roy. Astron. Soc. 126, 431.
Chistyakov, V. F.: 1962, Soviet Astron. A. J. 6, 363.
Cowling, T. G.: 1946, Monthly Notices Roy. Astron. Soc. 106, 218.
Cowling, T. G.: 1953, in G. P. Kuiper (ed.), The Sun, University of Chicago Press, Chicago.
Danielson, R. E.: 1961, Astrophys. J. 134, 289.
Deinzer, W.: 1965, Astrophys. J. 141, 548.
Gokhale, M. H.: 1972, in preparation.
Hale, G. E., Ellerman, F., Nicholson, S.B., and Joy, A.H.: 1919, Astrophys. J. 49, 153.
Hénoux, J. C.: 1969, Astron. Astrophys. 2, 288.
Jensen, E., Nordø, J., and Ringnes, T. S.: 1955, Astrophys. Norv. 5, 167.
Klüber, H. von: 1947, Z. Astrophys. 24, 121.
Kopecky, M. and Kuklin, G. V.: 1966, Bull. Astron. Inst. Czech. 17, 45.
Moe, O. K. and Maltby, P.: 1969, Solar Phys. 8, 275.
Musman, S.: 1967, Astrophys. J. 149, 201.
Nicholson, S. B.: 1933, Publ. Astron. Soc. Pac. 45, 51.
Oster, L.: 1968, Solar Phys. 3, 543.
Piddington, J. H.: 1954, Monthly Notices Roy. Astron. Soc. 114, 629.
Savage, B. D.: 1969, Astrophys. J. 156, 707.
Schlüter, A. and Temesvary, St.: 1958, in B. Lehnert (ed.), ‘Electromagnetic Phenomena in Cosmical Physics’, IAU Symp. 6, 263.
Schmidt, H. U.: 1968, in K.O. Kiepenheuer (ed.), ‘Structure and Development of Solar Active Regions’, IAU Symp. 35, 95.
Schröter, E. H.: 1966, Atti del Convegno sulle Macchi Solari, Firenze, p. 222.
Schröter, E. H.: 1971, in R. Howard (ed.), ‘Solar Magnetic Fields’, IAU Symp. 43, 167.
Severny, A. B.: 1965, Soviet Astron.-A. J. 9, 171.
Spruit, H. Ch.: 1972, in preparation.
Steenbeck, V. M. and Krause, F.: 1969, Astron. Nachr. 291, 49.
Stellmacher, G. and Wiehr, E.: 1970, Astron. Astrophys. 7, 432.
Suzuki, Y.: 1961, Bull. Kyoto Gakugi Univ. Ser. B 19, 4.
Suzuki, Y.: 1967, Publ. Astron. Soc. Japan 19, 220.
Tandberg-Hanssen, E.: 1956, Astrophys. Norvegica 5, 207.
Waldmeier, M.: 1939, Astron. Min. Zürich 138, 439.
Wilson, P. R. and Cannon, C. J.: 1968, Solar Phys. 4, 3.
Wilson, P. R. and McIntosh, P. S.: 1969, Solar Phys. 10, 370.
Wittmann, A. and Schröter, E. H.: 1969, Solar Phys. 10, 357.
Yun, H. S.: 1968, Theoretical Sunspot Models, Ph.D. Thesis, Indiana University (summary: Astrophys. J. 162 (1970), 975).
Yun, H. S.: 1971, Solar Phys. 16, 398.
Zhugzhda, Yu.D.: 1970, Soviet Astron.-A.J. 14, 274.
Zwaan, C.: 1965, Rech. Astron. Obs. Utrecht 17, Part 4.
Zwaan, C.: 1967, Solar Phys. 1, 478.
Zwaan, C.: 1968, Ann. Rev. Astron. Astrophys. 6, 135.
Zwaan, C. and Buurman, J.: 1971, in R. Howard (ed.), ‘Solar Magnetic Fields’, IAU Symp. 43, 220.
Author information
Authors and Affiliations
Rights and permissions
About this article
Cite this article
Gokhale, M.H., Zwaan, C. The structure of sunspots. Sol Phys 26, 52–75 (1972). https://doi.org/10.1007/BF00155105
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF00155105