Coronal heating in the coronal holes regions

On the basis of analyzing coronal hole observations with different instruments over a wide range of radio frequencies, the behavior of brightness temperatures in coronal holes depending on wavelength in the region of transition from brightenings to depressions with respect to the quiet Sun level was investigated. The study established the ranges of coronal plasma temperature and electron density values determining this period. An investigation of time-coincident images from the SSRT and Nobeyama radioheliograph revealed a linear correlation with a negative coefficient between brightness temperatures at 5.7 and 17 GHz in portions of coronal holes with sufficiently high contrast, which counts in favor of the Alfven wave mechanism of heating.