Abstract
The observational set-up for a detailed study of the velocity, intensity and magnetic-field fine structure in and around a sunspot is described. On highly resolved spectra we detected in the vicinity of a sunspot a large number of points with strong magnetic fields (magnetic knots). The magnetic field in these knots causes a striking decrease of the line depth (or a ‘line gap’ after Sheeley, 1967). The properties of the magnetic knots are: (1) magnetic fields up to 1400 gauss; (2) diameter ≈ 1100 km; (3) coincidence with dark intergranular spaces; (4) generally downward material motion; (5) lifetime>30min; (6) estimated total number around an unipolar spot ⩾ 2000; (7) combined magnetic flux comparable to the sunspot flux; (8) coincidence with Ca+ plages.
For the smallest sunspots (pores) we obtained magnetic fields >1500 gauss. Hence a magnetic field of about 1400–1500 gauss appears to be a rather critical level for pore and spot formation.
We found a large number of small areas producing line gaps without measurable magnetic field. These ‘non-magnetic gap-regions’ coincide with bright continuum structures.
Some aspects arising from the occurrence of hundreds of magnetic knots in an active region are discussed in the last section.
This is a preview of subscription content, log in via an institution to check access.
Similar content being viewed by others
References
Beckers, J. M. : 1964, Proc. Meeting on Sunspots, Florence, p. 186.
Beckers, J. M.: 1968, Solar Phys. 3, 258.
Beckers, J.M. and Schröter, E.H.: 1967, I.A.U. Symposium Nr. 35, Budapest.
Beckers, J.M. and Schröter, E.H.: 1968, Solar Phys. 4, 165.
Bray, R.J. and Loughhead, R.E.: 1964, Sunspots (Intern. Astrophys. Series, Vol. VII). Chapman and Hall, London.
Bray, R.J. and Loughhead, R.E.: 1967, The Solar Granulation (Intern. Astrophys. Series, Vol. VIII). Chapman and Hall, London.
Bumba, V.: 1967, Solar Phys. 1, 371.
Clark, A.: 1966, Phys. Fluids 9, 485.
Deubner, F.L.: 1967, Solar Phys. 2, 133.
Evans, J.W.: 1964a, Proc. Meeting on Solar Magnetic Field and High-Resolution Spectroscopy, Rome, p. 123.
Evans, J.W.: 1964b, Astrophys. Norv. 9, 53.
Evans, J.W.: 1967, Solar Phys. 1, 162.
Hale, G.E.: 1922, Comm. Mt. Wilson Observ. Nr. 80 (= Proc. Nat. Acad. Sci. 8), 168.
Hale, G.E. and Nicholson, S.B.: 1938, ‘Magnetic Observations of Sunspots’, Carnegie Inst. Wash. 1, 37.
Howard, R.: 1959, Astrophys. J. 130, 193.
Howard, R.: 1962, Astrophys. J. 136, 211.
Kopecky, M. and Kuklin, G.V.: 1966, Bull. Astron. Inst. Czech. 17, 45.
Leighton, R.B.: 1959, Astrophys. J. 130, 366.
Leighton, R.B.: 1964, Astrophys. J. 140, 1547.
Michard, R.: 1967, Solar Phys. 1, 498.
Parker, E.N.: 1963, Astrophys. J. 138, 226, 552.
Ringness, T.S. and Jensen, E.: 1960, Astrophys. Norv. 7, 99.
Schröter, E.H.: 1962, Z. Astrophys. 56, 183.
Schröter, E.H.: 1964a, Z. Astrophys. 62, 228, 256.
Schröter, E.H.: 1964b, Proc. Meeting on Sunspots, Florence, p. 222.
Severny, A.B.: 1964, Trans. IAU XII A, 755.
Severny, A.B. and Khoklova, U.L.: 1959, Izv. Krymsk. Astrofiz. Observ. 21, 290.
Sheeley, N.R.: 1967, Solar Phys. 1, 171.
Steshenko, N.V.: 1967, Izv. Krymsk. Astrofiz. Observ. 37, 21.
Tsap, T.T.: 1961, Izv. Krymsk. Astrofiz. Observ. 25, 148.
Unno, W.: 1956, Publ. Astron. Soc. Japan 8, 108.
Von Klüber, H.: 1955, in Vistas Astron., I, p. 751.
Author information
Authors and Affiliations
Additional information
Presently guest investigator at the Göttingen Observatory.
Previously member of the High Altitude Observatory solar project at Sacramento Peak (Contract Nr. AF (628) - 4078).
Rights and permissions
About this article
Cite this article
Beckers, J.M., Schröter, E.H. The intensity, velocity and magnetic structure of a sunspot region. Sol Phys 4, 142–164 (1968). https://doi.org/10.1007/BF00148076
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00148076