The radio brightness distribution along the solar limb observed on the Siberian Solar Radio Telescope

Abstract

The radio brightness distribution at 5.2 cm has been obtained along the entire solar limb down to a level of 0.01 of brightness temperature at the disk center T0c during the solar minimum. The measurements are based on strip scans from the Siberian Solar Radio Telescope. Data reduction included model fitting of an actual solar scan for each position angle. The maximum limb brightness, 1.37 T0c, in the derived distribution is at equatorial direction, where the radio radius exceeds the photosphere radius by 7%. Toward the poles, the brightness peak and radio radius gradually decrease to 1.01 T0c and 1.005 R0. The derived two-dimensional brightness distribution was used to calculate radio radius as a function of position angle for several wavelengths from 4 to 31.6 cm. These dependences are consistent with RATAN-600 observations at position angles 0° and 25°.