Detection of polarized radiation sources with
unusual spectral characteristics in the Sun

    Solar flare activity is produced by the processes of accumulation and release of energy in an active region. A complex magnetic structure is formed over the spots, the reconnection of which leads to the generation of a flare. The information about the magnetic field can be retrieved from is polarized microwave radiation, the spectrum of which is correlated with the flare activity. The polarized emission spectra of the stable active regions are monotonic (Fig.1), whereas the spectra of flare-productive active regions reveal sharp dips (Fig.2). In the framework of study of solar active regions, producing powerful flares the researchers from the RATAN-600 radio telescope have detected sources with features in the form of a sharp drop in the intensity of polarized radiation in various parts of the recorded frequency range (2-16GHz), sometimes changing the sign of polarization. Modelling of the phenomenon in the form of a hot coronal loop (Fig.3), located at heights of about 10~Mm (at the height of the transition region of about 22-5Mm) indicates that the discovered features of polarized light (Fig.4) may be explained by the presence of a hot region in the solar corona above the active region. This model and multi-wave observations allow to determine the magnetic field strength of the hot region (360-450G) and the product of the relative magnetic field gradient on the thickness of the loop (0.26-0.63).
Yasnov L.V., Kaltman T.I., Bogod V.M.
In collaboration with St. Petersburg State University.
Published: AJ, 2010, Vol 87, no. 11, 1-9.