Journal of The Korean Astronomical Society (천문학회지)

The Korean Astronomical Society (한국천문학회)
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SOLAR ACTIVE REGION STUDY USING MICROWAVE MAPS

  • BONG SU-CRAN (Astronomy Program, SEES, Seoul National University) ;
  • LEE JEONGWOO (Department of Physics, New Jersey Institute of Technology) ;
  • GARY DALE E. (Department of Physics, New Jersey Institute of Technology) ;
  • YUN HONG SIK (Astronomy Program, SEES, Seoul National University)
  • Published : 2003.06.01
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Abstract

Quiescent solar radiation, at microwave spectral regime, is dominated by gyroresonant and thermal Bremsstrahlung radiations from hot electrons residing in solar active region corona. These radiations are known to provide excellent diagnostics on the coronal temperature, density, and magnetic field, provided that spatially resolved spectra are available from observations. In this paper we present an imaging spectroscopy implemented for a bipolar active region, AR 7912, using the multifrequency interferometric data from the Owens Valley Solar Array (OVSA), as processed with a new imaging technique, so-called Spatio-Spectral Maximum Entropy Method (SSMEM). From the microwave maps at 26 frequencies in the range of 1.2-12.4 GHz at both right- and left-circular polarizations, we construct spatially resolved brightness spectra in every reconstructed pixel of about 2 arcsec interval. These spectra allowed us to determine 2-D distribution of electron temperature, magnetic field of coronal base, and emission measure at the coronal base above the active region. We briefly compare the present result with existing studies of the coronal active regions.

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References

  1. Aschwanden, M. J., Lim, J., Gary, D. E., & Klimchuk, J. A. 1995, Solar Rotation Stereoscopy in Microwaves, ApJ, 454, 512 https://doi.org/10.1086/176502
  2. Brosius, J. W., Willson, R. F., Holman, G. D., & Schmelz, J. T. 1992, Coronal Magnetic Structures Observing Campaign. IV - Multiwaveband Observations of Sunspot and Plage-associated Coronal Emission, ApJ, 386, 347 https://doi.org/10.1086/171021
  3. Brosius, J. W., Davila, J. M., Thomas, R. J., & White, S. M. 1997, Coronal Magnetography of a Solar Active Region Using Coordinated SERTS and VLA Observations, ApJ, 488. 488 https://doi.org/10.1086/304673
  4. Dulk, G. A. 1985. Radio Emission from the Sun and Stars, ARA&A, 23, 169 https://doi.org/10.1146/annurev.aa.23.090185.001125
  5. Gary, D. E., & Hurford, G. J. 1987, Multifrequency Observations of a Solar Active Region during a Partial Eclipse, ApJ, 317, 522 https://doi.org/10.1086/165296
  6. Gary. D. E., & Hurford, G. J. 1994, Coronal Temperature, Density, and Magnetic Field Maps of a Solar Active Region Using the Owens Valley Solar Array, ApJ, 420, 903 https://doi.org/10.1086/173614
  7. Hurford, G. J., & Gary, D. E. 1986, Measurement of Coronal Fields Using Spatially Resolved Microwave Spectroscopy, in NASA Conf. Proc. 2442, Coronal and Prominence Plasmas, ed. A. I. Poland (Washington: NASA), 319
  8. Klimchuk, J. A., & Gary, D. E. 1995, A Comparison of Active Region Temperatures and Emission Measures Observed in Soft X-Rays and Microwaves and Implications for Coronal Heating, ApJ, 448, 925 https://doi.org/10.1086/176021
  9. Komm. R. W., Hurford, G. J., & Gary, D. E. 1997, A Spatial and Spectral Maximum Entropy Method as Applied to OVRO Solar Data, A&AS, 122, 181 https://doi.org/10.1051/aas:1997300
  10. Lee. J.. Hurford, G. J., & Gary, D. E. 1993, Microwave Emission from a Sunspot. I - Implications for the Sunspot Magnetic Structure, Sol. Phys., 144, 45 https://doi.org/10.1007/BF00667981
  11. Lee, J.. White, S. M., Gopalswamy, N., & Kundu, M. R. 1997. Signatures of Coronal Currents in Microwave Images, Sol. Phys., 174, 175 https://doi.org/10.1023/A:1004956422669
  12. Lee, J., McClymont, A. N., Miki$\'{c}$, Z., White, S. M., & Kundu, M. R. 1998, Coronal Currents, Magnetic Fields, and Heating in a Solar Active Region, ApJ, 501. 853 https://doi.org/10.1086/305851
  13. Lee, J.. White. S. M., Kundu, M. R., Miki$\'{c}$, Z., & Mc Clymont, A. N. 1999, A Test for Coronal Magnetic Field Extrapolations, ApJ, 510, 413 https://doi.org/10.1086/306556
  14. Nindos, A., Kundu, M. R., White, S. M., Shibasaki, K., & Gopalswamy, N. 2000, Soft X-R,ay and Gyroresonance Emission above Sunspots, ApJS, 130, 485 https://doi.org/10.1086/317355
  15. Nitta, N., et al. 1991, Coronal Magnetic Structures Observing Campaign. I - Simultaneous Microwave and Soft X-ray Observations of Active Regions at the Solar Limb. ApJ. 374, 374 https://doi.org/10.1086/170128
  16. Priest, E. R. 1982, Solar Magneto-hydrodynamics (Dordrecht: D. Reidel)
  17. Schmelz, J. T., Holman, G. D., Brosius; J. W., & Gonzalez, R. D. 1992, Coronal Magnetic Structures Observing Campaign. II. Magnetic and Plasma Properties of a Solar Active Region, ApJ, 399. 733 https://doi.org/10.1086/171966
  18. Schmelz, J. T., Holman, G. D., Brosius, J. W., & Willson, R. F. 1994, Coronal Magnetic Structures Observing Campaign. 3: Coronal Plasma and Magnetic Field Diagnostics Derived From Multiwaveband Active Region Observations, ApJ, 434, 786 https://doi.org/10.1086/174781
  19. Strong, K. T., Alissandrakis, C. E., & Kundu, M. R. 1984, Interpretations of Microwave Active Region Structures Using SMM Soft X-ray Observations. ApJ. 277, 865 https://doi.org/10.1086/161757
  20. Webb, D. F., Holman, G. D., Davis, J. M., Kundu, M. R., & Shevgaonkar, R. K. 1987, The Plasma and Magnetic Field Properties of Coronal Loops Observed at High Spatial Resolution, ApJ, 315, 716 https://doi.org/10.1086/165173
  21. White, S. M., & Kundu, M. R, 1997, Radio Observations of Gyroresonance Emission from Coronal Magnetic Fields, Sol. Phys., 174, 31 https://doi.org/10.1023/A:1004975528106
  22. Zhang, J., Kundu, M. R., White, S. M., Dere, K. P., & Newmark, J. S. 2001, Reconciling Extreme Ultraviolet and Radio Observations of the Sun's Corona, ApJ, 561, 396 https://doi.org/10.1086/323212
  23. Zheleznyakov, V. V. 1962, The Origin of the Slowly Varying Component of Solar Radio Emission, Soviet Astron., 6, 3
  24. Zlotnik, E. Ya. 1968a, Theory of the Slowly Changing Component of Solar Radio Emission. I., Soviet Astron., 12. 245
  25. Zlotnik, E. Ya. 1968b, The Theory of the Slowly Changing Component of Solar Radio Emission. II., Soviet Astron., 12, 464

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