Coronal holes on the background of the quiet sun - Analysis of RATAN-600 observations in the 2-32-cm range

Observations of coronal holes (CH) and neighboring inactive solar-surface regions were performed at 10 wavelengths of the cm and dm range with the RATAN radio telescope. Based on the radio data as well as on optical observations of the sun, homogeneous models of the upper atmospheric layers of the quiet sun and coronal holes were constructed. These models are characterized by the fact that the ratio of temperature gradients in the transition region is 5-6 at a temperature of 500,000 K, while the density at the coronal base of a CH is lower than that in earlier models.