Observations and modeling of the spatial distribution and microwave radiation spectrum of the active region NOAA 11734

Microwave observations of the solar active region NOAA 11734 were done on April 28–May 8, 2013 with SSRT and the RATAN-600 radio telescopes. As a result of observations, two-dimensional distributions of the Stokes parameters I and V were obtained according to data from the SSRT at a frequency of 5.7 GHz and a microwave radiation spectra in the range of 3–18 GHz according to data from the RATAN-600. It was found that sunspots of the active region have an anomalous polarization that corresponds to the O-mode of microwave emisson up to 16 GHz. In order to explain the radio emission characteristics, the structure of the magnetic field in the nonlinear force-free approximation is restored, and free-free and gyroresonance radio emission are simulated. Maps of the model distribution of the brightness temperatures of both circular polarizations of the radio emission that replicate the observed spatial structure of the polarization on all days of observations were constructed. Analysis of the observational data and radio emission modeling make it possible to explain the characteristics of the polarization distribution within the mechanism of the weak interaction of radio emission modes in the quasi-transverse magnetic field above sunspots (Zheleznyakov, 1997).