Advertisement

Solar radio astronomy at low frequencies

  • George A. Dulk
III. Low Frequency Solar System Astronomy
Part of the Lecture Notes in Physics book series (LNP, volume 362)

Abstract

Powerful radio radiation often originates from the Sun at decametric and kilometric wavelengths. Radiation from the quiet Sun is produced by the thermal mechanism of bremsstrahlung, and radio bursts of several kinds are produced by the non-thermal mechanisms of plasma radiation and, rarely, gyrosynchrotron radiation.

Radio bursts are frequent during years of high solar activity. They are produced by several mechanisms of excitation: i) streams of electrons, individual, in groups of ten or so, or in storms of tens of thousands, ii) shock waves, with the radiation coming either from near the shock or distant from it by electrons accelerated by the shock, and iii) configurations of magnetic field that contain energetic electrons. In the frequency range of interest here, the radiation is produced at a distance from the Sun that varies from R ≈ 2 R at 20 MHz to R ≈ 10 R at 1 MHz, and R ≈ 1 AU at 30 kHz. In that frequency range the observed flux densities range from S ∶ 10−17 to 10−14 W m−2 Hz−1, and values of brightness temperature range from Tb ∶ 1012 to 1015.5 K.

To the present time there have been almost no observations of solar radiation between about 20 MHz, the limit of observations from the ground, and about 2 MHz where most observations from spacecraft commence. Below about 2 MHz, dynamic spectra of flux densities of solar bursts have been recorded, and, by the use of (short) dipoles on spinning spacecraft, observations have been made of the directions of centroids and characteristic sizes of the emitting sources. Even in the absence of true imaging capabilities, this information has proved to be very valuable in studies of morphology, brightness temperatures, and physics of solar radio phenomena. Proper imaging of the sources will remove present ambiguities and allow new phenomena to be observed.

Keywords

Solar Wind Radio Wave Brightness Temperature Coronal Hole Dynamic Spectrum 
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. Aubier, M., Leblanc, Y. and Boischot, A., 1971, Astron. Astrophys., 12, 435.Google Scholar
  2. Bougeret, J.L., Fainberg, J. and Stone, R.G., 1984, Astron. Astrophys., 136, 255.Google Scholar
  3. Cane, H.V. and Stone, R.G., 1984, Astrophys. J., 282, 339.CrossRefGoogle Scholar
  4. Cane, H.V., Stone, R.G., Fainberg, J., Steinberg, J.L. and Hoang, S., 1982, Solar Phys., 78, 187.CrossRefGoogle Scholar
  5. Couzens, D.A. and King, J.H., 1986, Interplanetary Medium Data Book, Suppl. 3 and 3a, NSSDC-WDC-A 86-04 and 86-04a, NASA Goddard Space Flight Center, Greenbelt, MD, USA.Google Scholar
  6. Dulk, G.A., Steinberg, J.L., Lecacheux, A., Hoang, S. and McDowall R.J., 1985, Astron. Astrophys. (Letters), 150, 28–30.Google Scholar
  7. Dulk, G.A., 1985, Ann. Rev. Astron. Astrophys., 23, 169.CrossRefGoogle Scholar
  8. Dulk, G.A., Steinberg, J.L., Hoang, S. and Goldman, M.V., 1987, Astron. Astrophys., 173, 366.Google Scholar
  9. Dulk, G.A., 1990, Solar Phys., in press.Google Scholar
  10. Kahler, S.W., Cliver, E.W. and Cane, H.V., 1989, Solar Phys., 120, 393.CrossRefGoogle Scholar
  11. Kai, K., Melrose, D.B. and Suzuki, S., 1985, in Solar Radiophysics, eds. D.J. McLean and N.R. Labrum (Cambridge: Cambridge University Press), p. 385.Google Scholar
  12. Kennel, C.F., Scarf, F.L., Coroniti, F.V., Smith, E.J. and Gurnett, D.A., 1982, J. Geophys. Res., 87, 17.Google Scholar
  13. Krüger, A., 1979, Introduction to Solar Radio Astronomy and Radio Physics, (Dordrecht: Reidel), 330 pp.Google Scholar
  14. Kundu, M.R., 1983, Solar Phys., 86, 205.CrossRefGoogle Scholar
  15. Kundu, M.R. and Gergely, E. eds., 1980, Radio Physics of the Sun, IAU Symp. No. 86, (Dordrecht: Reidel), 475 pp.Google Scholar
  16. Kundu, M.R., Gergely, E., Schmahl, E.J., Szabo, A., Loiacono, R. and Wang, Z., 1987, Solar Phys., 108, 113.CrossRefGoogle Scholar
  17. Lecacheux, A., Steinberg, J.L., Hoang, S. and Dulk, G.A., 1989, Astron. Astrophys., 217, 237.Google Scholar
  18. Lin, R.P., Potter, D.W., Gurnett, D.A. and Scarf, F.L., 1981, Astrophys. J., 251, 364.CrossRefGoogle Scholar
  19. Lin, R.P., Levedahl, W.K., Lotko, W., Gurnett, D.A. and Scarf, F.L., 1986, Astrophys. J., 308, 954.CrossRefGoogle Scholar
  20. McLean, D.J. and Labrum, N.R. eds., 1985, Solar Radiophysics, (Cambridge: Cambridge University Press), 516 pp.Google Scholar
  21. Melrose, D.B., Dulk, G.A. and Cairns, I.H., 1986, Astron. Astrophys., 163, 229.Google Scholar
  22. Melrose, D.B. and Dulk, G.A., 1988, Solar Phys., 116, 141.CrossRefGoogle Scholar
  23. Nelson, G.J. and Melrose, D.B., 1985, in Solar Radiophysics, eds. D.J. McLean and N.R. Labrum (Cambridge: Cambridge University Press), p. 333.Google Scholar
  24. Pick, M., 1990, Solar Phys., in press.Google Scholar
  25. Reiner, M.J. and Stone, R.G., 1989, Astron. Astrophys., 217, 251.Google Scholar
  26. Reiner, M.J. and Stone, R.G., 1990, Astron. Astrophys., in press.Google Scholar
  27. Robinson, R.D., 1985, in Solar Radiophysics, eds. D.J. McLean and N.R. Labrum (Cambridge: Cambridge University Press), p. 385.Google Scholar
  28. Sheridan, K.V. and Dulk, G.A., 1980, in Solar and Interplanetary Dynamics, eds. M. Dryer and E. Tandberg-Hanssen, (Dordrect: Reidel), p. 37.Google Scholar
  29. Sheridan, K.V. and McLean, D.J., 1985, in Solar Radiophysics, eds. D.J. McLean and N.R. Labrum (Cambridge: Cambridge University Press), p. 443.Google Scholar
  30. Smerd, S.F., 1950, Austr. J. Sci. Res., Ser. A, 3, 34.Google Scholar
  31. Stewart, R.T., 1985, in Solar Radiophysics, eds. D.J. McLean and N.R. Labrum (Cambridge: Cambridge University Press), p. 361.Google Scholar
  32. Suzuki, S. and Dulk, G.A., 1985, in Solar Radiophysics, eds. D.J. McLean and N.R. Labrum (Cambridge: Cambridge University Press), p. 289.Google Scholar
  33. Wild, J.P., Smerd, S.F. and Weiss, A.A., 1963, Ann. Rev. Astron. Astrophys., 1, 291.CrossRefGoogle Scholar

Copyright information

© Springer-Verlag 1990

Authors and Affiliations

  • George A. Dulk
    • 1
  1. 1.Department of Astrophysical, Planetary and Atmospheric SciencesUniversity of ColoradoBoulder

Personalised recommendations