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| Paper: |
Microwave Spectral-Polarization Structure of Type I Noise Storm-Producing Active Regions on the Sun |
| Volume: |
154, Cool Stars, Stellar Systems and the Sun: Tenth Cambridge Workshop |
| Page: |
573 |
| Authors: |
Bogod, V. M.; Gariamov, V. I.; Gelfreikh, G. B.; Willson, R. F.; Kile, J. N.; Lang, K. R. |
| Abstract: |
RATAN-600 spectral-polarization observations of solar active regions have been compared with with VLA observations of noise storms and Yohkoh soft X-ray images of coronal loops. The RATAN data were used to identify active regions which show narrow-band polarization inversions of sunspot-associated microwave sources. In contrast to some previous observations, our data show that the time at which the polarization inversion occurs does not always depend on the location of the active region on the disc with respect to central meridian passage. For one active region the inverted polarity of a sunspot-associated source persists for several days and then reverts to what one would normally expect from the polarity of the underlying sunspot. For other microwave sources, a double inversion in circular polarization was observed over a relatively narrow frequency range of typically Delta nu/nu <= 5%. The observed inversion of the sign of circular polarization was, in some cases, impossible to explain in terms of the propagation of radio waves through a quasi-transverse (QT) region in the corona. Instead, these narrow-band polarization changes require more complicated magnetic configurations, such as current sheets, that may also produce the accelerated particles responsible for noise storms at longer wavelengths. |
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