Abstract
The thermal contrast α, and the umbra-penumbraA u/A p, were calculated for 63 sunspots of various sizes and morphologies. Contrary to the assumptions of the PSI model, α andA u/A p were found to be quite variable. The values of α ranged from 0.1807 to 0.4266;A u/A p ranged from 0.0089 to 0.4899. The values of α andA u/A p correlated well (r = 0.6018;p<0.005) and the regression for α andA u/A p was obtained: α = (0.220 ± 0.016) + (0.340 ± O.06)A u/A p. The values of α andA u/A p were then compared with complexity ratings, magnetic field strength, time, and μ. The quantities α andA u/A p were found to be independent of the complexity, magnetic field strength, and time factors. The correlation between α andA u/A p lead to the proposed division of α into an umbral thermal contrast αu, and a penumbral thermal contrast αp. These values were calculated from the photometric data: αu = 0.57 ± 0.01 and αp = 0.26 ± 0.006.
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References
Affifi, A. A. and Clark, V.: 1984,Computer-Aided Multivariate Analysis, Van Nostrand Reinhold Co., New York.
Allen, C. W.: 1973,Astrophysical Quantities, Athlone Press, London.
Beck, J. G.: 1991, M.S. Thesis CSUN, Northridge.
Bevington, P. R.: 1969,Data Reduction and Error Analysis for the Physical Sciences, McGraw-Hill, New York.
Brahde, R.: 1972,Solar Phys. 26, 318.
Brandt, P. N., Schmidt, W., and Steinegger, M.: 1990,Solar Phys. 129, 191.
Chapman, G. A.: 1987,Ann. Rev. Astron. Astrophys. 25, 633.
Chapman, G. A.: 1988,Adv. Space Res. 8(7), 721.
Chapman, G. A. and Meyer, A. D.: 1981, in L. E. Cram and J. H. Thomas (eds.),The Physics of Sunspots, Sacramento Peak Observatory, Sunspot, NM, p. 446.
Chapman, G. A. and Walton, S. R.: 1989, in O. Van der Luhe (ed.),High Spatial Resolution Solar Observations, Sacramento Peak Observatory, Sunspot, NM, p. 402.
Chapman, G. A. and Walton, S. R.: 1991, in L. J. November (ed.),Solar Polarimetry, Sacramento Peak Observatory, Sunspot, NM, p. 37.
Chapman, G. A., Herzog, A. D., Laico, D. E., Lawrence, J. K., and Templer, M. S.: 1989,Astrophys. J. 343, 547.
Chapman, G. A., Herzog, A. D., Lawrence, J. K., Walton, S. R., Hudson, H. S., and Fisher, B. M.: 1992,J. Geophys. Res. 97, 8211.
Foukal, P.: 1981, in L. E. Cram and J. H. Thomas (eds.),The Physics of Sunspots, Sacramento Peak Observatory, Sunspot, NM, p. 391.
Hansen, T.: 1973,Solar Phys. 32, 505.
Hudson, H. S., Silva, S., Woodard, M., and Willson, R. C.: 1981,Solar Phys. 76, 211.
Laico, D. E.: 1987, M.S. Thesis CSUN, Northridge.
Lawrence, J. K. and Chapman, G. A.: 1990,Astrophys. J. 361, 709.
Lawrence, J. K., Chapman, G. A., and Walton, S. R.: 1991,Astrophys. J. 375, 771.
Lawrence, J. K., Chapman, G. A., Herzog, A. D., and Shelton, J. C.: 1985,Astrophys. J. 292, 297.
Meyer, A. D.: 1983, M.S. Thesis CSUN, Northridge.
Pierce, A. K. and Slaughter, C. D.: 1977,Solar Phys. 51, 25.
Neckel, H. and Labs, D.: 1984,Solar Phys. 90, 205.
Staveland, L.: 1974,Solar Phys. 36, 235.
Steinegger, M., Brandt, P. N., Pap, J., and Schmidt, W.: 1990,Astrophys. Space Sci. 170, 127.
Willson, R. C., Gulkis, S., Janssen, M., Hudson, H. S., and Chapman, G. A.: 1981,Science 211, 700.
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Beck, J.G., Chapman, G.A. A study of the contrast of sunspots from photometric images. Sol Phys 146, 49–60 (1993). https://doi.org/10.1007/BF00662169
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DOI: https://doi.org/10.1007/BF00662169