Abstract

Using the microwave radio observations with Siberian Solar Radio Telescope (SSRT) and Nobeyama Radio Heliograph (NoRH) we derived 2D coronal magnetograms of solar active region NOAA 8365. The circular polarization (CP) of radio source is modified, when the radiation passes through the overlying magnetic field transverse to the line-of-sight. This change in CP was used to study the properties of coronal fields. We employed the known theory of wave-mode coupling in quasi-transverse (QT) region to evaluate the distribution of the field strength at the level of transformation of 5.2 cm radiation (SSRT, field strength ∼ 10-30 G) and 1.76 cm (NoRH, ∼ 50-110 G). The magnetic field strength was derived under the assumption N~Lα = 1018 cm-2, where N is electron density and Lα is the scale of coronal field divergence along line-of-sight. The height of QT-region (HQTR) was estimated using force free field extrapolations, HQRT = 6.3 x 109 cm (2.3 x 109 cm) for 20 G (85 G). We then compared the coronal radio magnetograms and the force free field extrapolation of photospheric magnetic field, and we found close similarity between them on large spatial scale.