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On the Interpretation of Weak Sources of Enhanced 80 MHz Emission in theSolar Corona

Published online by Cambridge University Press:  25 April 2016

A. C. Riddle
A. C. Riddle*
Affiliation:
Division of Radiophysics, CSIRO, Sydney
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Extract

Recent two-dimensional observations of the quiet sun at 80 MHz by Sheridan showed a persistent low-intensity source (radio enhancement) whose daily motion was consistent with a source at radius 0.95 R® rotating with a synodic period of 27.3 d. In this paper we shall attempt to interpret this result in terms of the effects of refraction and opacity in model coronas. Comprehensive studies of the Sun at 169 MHz show that similar radio enhancements are associated with coronal streamers and that reasonable values for electron density and temperature within the coronal streamer allow the observations to be explained in terms of thermal radiation. Hence we shall consider only coronal models that possess streamer structure. We shall show that temperature enhancements within the streamer (‘thermal model’) do not lead to an apparent radius as small as that observed by Sheridan and that his observation may be better understood in terms of a non-thermal model for radiation from the streamer region.

Type
Contributions
Information
Publications of the Astronomical Society of Australia , Volume 1 , Issue 8 , September 1970 , pp. 375 - 376
Copyright
Copyright © Astronomical Society of Australia 1970

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References

1 Sheridan, K. V., Proc. ASA, 1, 376 (1970).Google Scholar
2 Leblanc, Y., Aatron. Astrophys., 1, 467 (1969).Google Scholar
3 Leblanc, Y., Astron. Astrophys., 4, 315 (1970).Google Scholar
4 Newkirk, G. A., Ap. J., 133, 983 (1961).CrossRefGoogle Scholar