Abstract
Daily observations of Doppler line shifts made with very low spatial resolution (3′) with the Stanford magnetograph have been used to study the equatorial rotation rate, limb effect on the disk, and the mean meridonial circulation. The equatorial rotation rate was found to be approximately constant over the interval May 1976–January 1977 and to have the value 2.82 μrad s−1 (1.96 km s−1). This average compares favorably with the results of Howard (1977) of 2.83 μrad s−1 for the same time period. The RMS deviation of the daily measurements about the mean value was 1% of the rate (20 m s−1), much smaller than the fluctuations reported by Howard and Harvey (1970) of several per cent. These 1% fluctuations are uncorrelated from day-to-day and may be due to instrumental problems. The limb effect on the disk was studied in equatorial scans (after suppressing solar rotation). A redshift at the center of the disk relative to a position 0.60R ⊙ from the center of 30 m s−1 was found for the line Fe i λ5250 Å. Central meridian scans were used (after correcting for the limb effect defined in the equatorial scans) to search for the component of mean meridonial circulation symmetric across the equator. A signal is found consistent with a polewards flow of 20 m s−1 approximately constant over the latitude range 10–50°. Models of the solar differential rotation driven by an axisymmetric meridonial circulation and an anisotropic eddy viscosity (Kippenhahn, 1963; Cocke, 1967; Köhler, 1970) predict an equatorwards flow at the surface. However, giant cell convection models (Gilman, 1972, 1976, 1977) predict a mean polewards flow (at the surface). The poleward-directed meridonial flow is created as a by-product of the giant cell convection and tends to limit the differential rotation. The observation of a poleward-directed meridonial circulation lends strong support to the giant cell models over the anisotropic eddy viscosity models.
Article PDF
Similar content being viewed by others
Avoid common mistakes on your manuscript.
References
Cocke, W. J.: 1967, Astrophys. J. 150, 1041.
Gilman, P. A.: 1972, Solar Phys. 27, 3.
Gilman, P.A.: 1976, in V. Bumba and J. Kleczek (eds.), ‘Basic Mechanisms of Solar Activity’, IAU Symp. 71, 207.
Gilman, P. A.: 1977, Geophys. Astrophys. Fluid Dyn. 8, 93.
Hart, M.: 1974, Astrophys. J. 187, 393.
Howard, R.: 1972, Solar Phys. 24, 123.
Howard, R.: 1977, private communication.
Howard, R. and Harvey, J.: 1970, Solar Phys. 12, 23.
Kippenhahn, R.: 1963, Astrophys. J. 137, 664.
Köhler, H.: 1970, Solar Phys. 13, 3.
Kubičela, A. and Karabin, M.: 1977, Solar Phys. 52, 199.
Lites, B. W.: 1972, HAO Research Memorandum No. 185.
Scherrer, P., Wilcox, J. M., Svalgaard, L., Duvall, T. L., Jr., Dittmer, P. H., and Gustafson, E. K.: 1977, Solar Phys., 54, 353.
Svalgaard, L., Scherrer, P. H., and Wilcox, J. M., 1979, Solar Phys., in press.
Author information
Authors and Affiliations
Additional information
Now at Kitt Peak National Observatory, Tucson, Ariz., U.S.A.
Rights and permissions
About this article
Cite this article
Duvall, T.L. Large-scale solar velocity fields. Sol Phys 63, 3–15 (1979). https://doi.org/10.1007/BF00155690
Received:
Revised:
Issue Date:
DOI: https://doi.org/10.1007/BF00155690