Abstract
Doppler spectroheliograms of sunspots and their surroundings have been obtained with a spatial resolution approaching one second of arc and a time resolution of 20 s per frame. Observations of 5 sunspots, located 18°, 45°, 56°, 60° and 72° from the disk center respectively, showed considerable long-lived fine structure and, in particular, indicated the following:
-
(1)
The Evershed outflow terminated in spoke-like structures that constitute the ragged outer boundary of the penumbra. Some of these spokes extended more than 8000 km beyond the average outer boundary.
-
(2)
Although there was considerable long-lived fine structure of both Doppler polarities in the extra-penumbral photosphere, the spatially-averaged horizontal flow was outward for roughly 10000 km beyond the outer boundary of the penumbra. This extra-penumbral velocity field was distinct from the Evershed flow, and, in particular, did not represent its extension beyond the end of the penumbral spokes.
Although these results are based on observations of relatively few sunspots, they do suggest that if magnetic fields are carried outward from sunspots by material motions, then these motions are more like the supergranulation than an extension of the Evershed velocity.
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.: 1966, Proceedings of the Sunspot Symposium, G. Barbera, Florence, p. 190.
Beckers, J. M.: 1968, Solar Phys. 3, 258.
Beckers, J. M.: 1969, Plasma Instabilities in Astrophysics (ed. by D. G. Wentzel and D. A. Tidman), Gordon and Breach Science Publ., New York, p. 139.
Bhatnagar, A.: 1967, Kodaikanal Obs. Bull. 180, Series A.
Brekke, K. and Maltby, P.: 1963, Ann. Astrophys. 26, 383.
Evershed, J.: 1913, Kodaikanal Obs. Bull. No. 15, 63.
Evershed, J.: 1921, Kodaikanal Obs. Bull. No. 51, 167.
Harvey, J. W. and Harvey, K.: 1971, private communication.
Holmes, J.: 1963, Monthly Notices Roy. Astron. Soc. 126, 155.
Kinman, T. D.: 1952, Monthly Notices Roy. Astron. Soc. 112, 425.
Kinman, T. D.: 1953, Monthly Notices Roy. Astron. Soc. 113, 613.
Leighton, R. B., Noyes, R. W., and Simon, G. W.: 1962, Astrophys. J. 135, 474.
Schröter, E. H.: 1966, Proceedings of the Sunspot Symposium, G. Barbera, Florence, p. 190.
Schröter, E. H.: 1967, in Solar Physics (ed. by J. N. Xanthakis), (The Proceedings of NATO Advanced Study Institute on Solar Physics, Lagonissi, Greece, Sept. 1965), Interscience Publ., New York, p. 325.
Servajean, R.: 1961, Ann. Astrophys. 24, 1.
Sheeley, N. R., Jr.: 1969, Solar Phys. 9, 347.
Sheeley, N. R., Jr.: 1971, in R. Howard (ed.), ‘Solar Magnetic Fields’, IAU Symp. 43, 310.
Sheeley, N. R., Jr. and Bhatnagar, A.: 1971a, Solar Phys. 18, 195.
Sheeley, N. R., Jr. and Bhatnagar, A.: 1971b, Solar Phys. 18, 379.
Simon, G. W. and Leighton, R. B.: 1964, Astrophys. J. 140, 1120.
St. John, C. E.: 1913a, Astrophys. J. 37, 322.
St. John, C. E.: 1913b, Astrophys. J. 38, 341.
Vrabec, D.: 1971, in R. Howard (ed.), ‘Solar Magnetic Fields’, IAU Symp. 43, 329.
Author information
Authors and Affiliations
Additional information
Operated by the Association of Universities for Research in Astronomy, Inc., under contract to the National Science Foundation.
Visiting Astronomer, Solar Division.
Rights and permissions
About this article
Cite this article
Sheeley, N.R., Bhatnagar, A. Two-dimensional observations of the velocity field in and around sunspots. Sol Phys 19, 338–346 (1971). https://doi.org/10.1007/BF00146062
Received:
Issue Date:
DOI: https://doi.org/10.1007/BF00146062