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Sunspots at centimeter wavelengths

Published online by Cambridge University Press:  26 August 2011

Mukul R. Kundu  and
Jeongwoo Lee
Mukul R. Kundu
Affiliation:
Department of Astronomy, University of Maryland, College Park, MD 20742, U.S.A.
Jeongwoo Lee
Affiliation:
Physics Department, New Jersey Institute of Technology, Newark, NJ 07102, U.S.A. email: [email protected]
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Abstract

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The early solar observations of Covington (1947) established a good relation between 10.7 cm solar flux and the presence of sunspots on solar disk. The first spatially resolved observation with a two-element interferometer at arc min resolution by Kundu (1959) found that the radio source at 3 cm has a core-halo structure; the core is highly polarized and corresponds to the umbra of a sunspot with magnetic fields of several hundred gauss, and the halo corresponds to the diffuse penumbra or plage region. The coronal temperature of the core was interpreted as due to gyroresonance opacity produced by acceleration of electrons gyrating in a magnetic field. Since the opacity is produced at resonant layers where the frequency matches harmonics of the gyrofrequency, the radio observation could be utilized to measure the coronal magnetic field. Since this simple interferometric observation, the next step for solar astronomers was to use arc second resolution offered by large arrays at cm wavelengths such as Westerbrock Synthesis Radio Telescope and the Very Large Array, which were primarily built for cosmic radio research. Currently, the Owens Valley Solar Array operating in the range 1-18 GHz and the Nobeyama Radio Heliograph at 17 and 34 GHz are the only solar dedicated radio telescopes. Using these telescopes at multiple wavelengths it is now possible to explore three dimensional structure of sunspot associated radio sources and therefore of coronal magnetic fields. We shall present these measurements at wavelengths ranging from 1.7 cm to 90 cm and associated theoretical developments.

Keywords

Sun: coronaSun: magnetic fieldsSun: radio radiationsunspots
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 6 , Symposium S273: The Physics of Sun and Star Spots , August 2010 , pp. 265 - 271
Copyright
Copyright © International Astronomical Union 2011

References

Akhmedov, S. B., Gelfreikh, G. B., Bogod, V. M., & Korzhavin, A. N. 1982, Solar Phys., 79, 41CrossRefGoogle Scholar
Alissandrakis, C. E., Kundu, M. R., & Lantos, P. 1980, Astron. Astrophys., 82, 30Google Scholar
Alissandrakis, C. E. & Kundu, M. R. 1982, ApJ Letters, 253, L49CrossRefGoogle Scholar
Alissandrakis, C. E. & Kundu, M. R. 1984, Astron. Astrophys., 139, 271Google Scholar
Bong, S.-C., Lee, J., Gary, D. E., & Yun, H. S. 2003, J. of the Korean Astron. Soc., 36, S29CrossRefGoogle Scholar
Bogod, V. M. & Gelfreikh, G. B. 1980, Solar Phys., 67, 29CrossRefGoogle Scholar
Brosius, J. W., Landi, E., Cook, J. W., Newmark, J. S., Gopalswamy, N., & Lara, A. 2002, ApJ, 574, 453CrossRefGoogle Scholar
Covington, A. E. 1947, Nature, 159, 405CrossRefGoogle Scholar
Gary, D. E. & Hurford, G. J. 1994, ApJ, 420, 903Google Scholar
Gary, D. E. & Keller, C. U. 2004, Solar and Space Weather Radiophysics – Current Status and Future Developments (Dordrecht: Kluwer).Google Scholar
Gelfreikh, G. B., Grechnev, V., Kosugi, T., & Shibasaki, K. 1999, Solar Phys., 185, 177CrossRefGoogle Scholar
Gopalswamy, N., Payne, T. E. W., Schmahl, E. J., Kundu, M. R., Lemen, J. R., Strong, K. T., Canfield, R. C. & de La Beaujardiere, J. 1994, ApJ, 437, 522Google Scholar
Hurford, G. J., Read, R. B., & Zirin, H. 1984, Solar Phys., 94, 413Google Scholar
Komm, R. W., Hurford, G. J., & Gary, D. E. 1997, Astron. Astrophys. Suppl. Ser., 122, 181CrossRefGoogle Scholar
Krüger, A., Hildebrandt, J., Bogod, V. M., Korzhavin, A. N., & Akhmedov, Sh. B. 1986, Solar Phys., 105, 111Google Scholar
Kundu, M. R. 1959, Paris Symposium on Radio Astronomy, Ed. Bracewell, Ronald N., Stanford U. Press, Stanford, p. 222Google Scholar
Kundu, M. R. & Alissandrakis, C. E. 1984, Solar Phys., 94, 249CrossRefGoogle Scholar
Lee, J. 2007, Space Science Reviews, 133, 73Google Scholar
Lee, J., Hurford, G. J., & Gary, D. E. 1993a, Solar Phys., 144, 45Google Scholar
Lee, J., Gary, D. E., & Hurford, G. J. 1993b, Solar Phys., 144, 349Google Scholar
Lee, J., Gary, D. E., Hurford, G. J., & Zirin, H. 1993c, ASPC, 141, 287.Google Scholar
Lee, J., McClymont, A. N., Mikić, Z., White, S. M. & Kundu, M. R. 1998, ApJ 501, 853Google Scholar
Lee, J., White, S. M., Kundu, M. R., Mikić, Z., & McClymont, A. N. 1999, ApJ, 510, 413Google Scholar
Nindos, A., Alissandrakis, C. E., Gelfreikh, G. B., Bogod, V. M., & Gontikakis, C. 2002, ApJ, 386, 658Google Scholar
Parker, E. N. 1988, ApJ, 330, 474CrossRefGoogle Scholar
Rosner, R., Tucker, W. H., & Vaiana, G. S. 1978, ApJ, 220, 643CrossRefGoogle Scholar
Schmahl, E. J., Kundu, M. R., Strong, K. T., Bentley, R. D., Smith, J. B., & Krall, K. R. 1982, Solar Phys., 80, 233Google Scholar
Schmelz, J. T. & Holman, G. D. 1991, Adv. Space Res., 11, 109Google Scholar
Schmelz, J. T., Holman, G. D., Brosius, J. W., & Willson, R. F. 1994, ApJ, 434, 786Google Scholar
Shibasaki, K. 1996, Adv. Space Res., 17, 135Google Scholar
Shibasaki, K. 1998, ASPC, 140, 373Google Scholar
Shibasaki, K. 2001, ApJ, 550, 1113Google Scholar
Strong, K. T., Alissandrakis, C. E., & Kundu, M. R. 1984, ApJ, 277, 865Google Scholar
Tun, S. 2010, in preparationGoogle Scholar
Vourlidas, A., Bastian, T. S., & Aschwanden, M. J. 1997, ApJ, 489, 403CrossRefGoogle Scholar
Webb, D. F., Holman, G. D., Davis, J. M., Kundu, M. R., & Shevgaonkar, R. K. 1987, ApJ, 315, 716Google Scholar
White, S. M. & Kundu, M. R. 1997, Solar Phys., 174, 31Google Scholar
Zhang, J., Gopalswamy, N., Kundu, M. R., Schmahl, E. J., & Lemen, J. R. 1998, Solar Phys., 180, 285CrossRefGoogle Scholar
Zheleznyakov, V. V. 1962, Soviet Astr., 6, 3Google Scholar
Zlotnik, E. Ya., White, S. M., & Kundu, M. R. 1998, ASPC, 155, 135Google Scholar