Advertisement

Solar Physics

, Volume 174, Issue 1–2, pp 175–190 | Cite as

SIGNATURES OF CORONAL CURRENTS IN MICROWAVE IMAGES

  • Jeongwoo Lee
  • Stephen M. White
  • N. Gopalswamy
  • M. R. Kundu
Article

Abstract

Microwave emission from solar active regions at frequencies above 4 GHz is dominated by gyroresonance opacity in strong coronal magnetic fields, which allows us to use radio observations to measure coronal magnetic field strengths. In this paper we demonstrate one powerful consequence of this fact: the ability to identify coronal currents from their signatures in microwave images. Specifically, we compare potential-field (i.e., current-free) extrapolations of photospheric magnetic fields with microwave images and are able to identify regions where the potential extrapolation fails to predict the magnetic field strength required to explain the microwave images. Comparison with photospheric vector magnetic field observations indicates that the location inferred for coronal currents agrees with that implied by the presence of vertical currents in the photosphere. The location, over a neutral line exhibiting strong shear, is also apparently associated with strong heating.

Keywords

Magnetic Field Magnetic Field Strength Neutral Line Vector Magnetic Field Strong Shear 
These keywords were added by machine and not by the authors. This process is experimental and the keywords may be updated as the learning algorithm improves.

Preview

Unable to display preview. Download preview PDF.

Unable to display preview. Download preview PDF.

References

  1. Akhmedov, Sh. B. and others: 1986, Astrophys. J. 301, 460.CrossRefGoogle Scholar
  2. Alissandrakis, C. E.: 1981, Astron. Astrophys. 100, 197.Google Scholar
  3. Alissandrakis, C. E. and Kundu, M. R.: 1984, Astron. Astrophys. 139, 271.Google Scholar
  4. Alissandrakis, C. E., Kundu, M. R., and Lantos, P.: 1980, Astron. Astrophys. 82, 30.Google Scholar
  5. Aschwanden, M. J., Lim, J., Gary, D. E., and Klimchuk, J. A.: 1995, Astrophys. J. 454, 512.Google Scholar
  6. Bastian, T. S.: 1990, Solar Phys. 130, 265.Google Scholar
  7. Chae, J.-C.: 1996, Ph.D. thesis, Seoul National University.Google Scholar
  8. Chiuderi-Drago, F., Alissandrakis, C., and Hagyard, M.: 1987, Solar Phys. 112, 89.Google Scholar
  9. Gary, D. E. and Hurford, G. J.: 1994, Astrophys. J. 420, 903.Google Scholar
  10. Gary, D. E. and Hurford, G. J.: 1987, Astrophys. J. 317, 522.Google Scholar
  11. Kakinuma, T. and Swarup, G.: 1962, Astrophys. J. 136, 975.Google Scholar
  12. Kopp, G. and Rabin, D.: 1992, Solar Phys. 141, 253.Google Scholar
  13. Lee, J., Chae, J.-C., Yun, H. S., and Zirin, H.: 1996, Solar Phys. 171, 269.CrossRefGoogle Scholar
  14. Lites, B.W. and Skumanich, A.: 1981, in Lawrance E. Cram and John H. Thomas (eds.), The Physics of Sunspots, Sacramento Peak Observatory, p. 156.Google Scholar
  15. Low, B. C.: 1992, Astrophys. J. 399, 300.CrossRefGoogle Scholar
  16. Martínez Pillet, V. and Vázquez, M.: 1993, Astron. Astrophys. 270, 494.Google Scholar
  17. Pallavicini, R., Sakurai, T., and Vaiana, G. S.: 1981, Astron. Astrophys. 98, 316.Google Scholar
  18. Sakurai, T.: 1982, Solar Phys. 76, 301.CrossRefGoogle Scholar
  19. Sakurai, T.: 1980, Solar Phys. 69, 343.Google Scholar
  20. Sakurai, T.: 1979, Publ. Astron. Soc. Japan 31, 209.Google Scholar
  21. Schmahl, E. J., Kundu, M. R., Strong, K. T., Bentley, R. D., Smith, J. B., and Krall, J. R.: 1982, Solar Phys. 80, 233.Google Scholar
  22. Schmelz, J. T., Holman, G. D., Brosius, J. W., and Wilson, R. F.: 1994, Astrophys. J. 434, 786.CrossRefGoogle Scholar
  23. Shibasaki, K., Chiuderi Drago, F., Melozzi, M. Slottje, C., and Antonucci, E.: 1983, Solar Phys. 89, 307.CrossRefGoogle Scholar
  24. Varsik, J. R.: 1995, Solar Phys. 161, 207.Google Scholar
  25. Vernazza, J., Avrett, H., and Loeser, R.: 1981, Astrophys. J. Suppl. 45, 635.CrossRefGoogle Scholar
  26. Yun, H. S., Beebe, H. A., and Baggett, W. E.: 1981, Lawrance E. Cram and John H. Thomas, (eds.), The Physics of Sunspots, Sacramento Peak Observatory, p. 148.Google Scholar
  27. Zheleznyakov, V. V.: 1962, Astron. Zh. 39, 5 (Soviet Astron. 6, 3).Google Scholar
  28. Zlotnik, E. Ya.: 1968, Astron. Zh. 45, 310 (Soviet Astron. 12, 245).Google Scholar

Copyright information

© Kluwer Academic Publishers 1997

Authors and Affiliations

  • Jeongwoo Lee
    • 1
  • Stephen M. White
    • 1
  • N. Gopalswamy
    • 1
  • M. R. Kundu
    • 1
  1. 1.Department of AstronomyUniversity of MarylandCollege ParkU.S.A

Personalised recommendations