On the Technique of Coronal Magnetography Through Quasi-Transverse Propagation of Microwaves
Abstract
The technique of coronal magnetography is illustrated and analyzed on the samples of four solar active regions (ARs). Observational bases for the coronal magnetography are the radio maps of the Sun taken with the Siberian Solar Radio Telescope (SSRT) at the wavelength 5.2 cm both in l I and l V Stokes parameters. The magnetic field strength is found using the theory of wave mode coupling in the region of quasi-transverse (QT) propagation. The proper values are found to be in the range of 10--30 G. The technique used is based on the fact that the circular polarization of a radio source is modified when the ray path crosses a region in the solar corona where the magnetic field is transverse to the line of sight. We have successfully applied this method to the whole period of transit on the solar disk of NOAA 9068, 9097 and NOAA 9339, while we have noticed some limitations of the coronal magnetography for the flare-productive active region NOAA 9415. The coronal magnetograms appear to be a series of 2D partial magnetograms, each day covering a part of the AR: the following part near the eastern limb and the leading one near the western limb. The technique has been verified to be reliable in the determination of coronal magnetic fields, but needs further improvements concerning the evaluation of their height, related to the heights of the QT-region.
- Publication:
-
Baltic Astronomy
- Pub Date:
- 2005
- Bibcode:
- 2005BaltA..14...83B
- Keywords:
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- Sun: radio radiation;
- corona;
- magnetic fields