Variations of microwave radiation from solar active regions and coronal heating

Y.T. Tsap

G.B. Gelfreikh, Y.G. Kopylova, T.B. Goldvarg, Y.A. Nagovitsin, L.I. Tsvetkov

On the basis of observed data obtained with the radio telescope RT-22 of the Crimean Astrophysical Observatory at 8.6 and 15.4 GHz the quasi-periodic variations of macrowave radiation from solar active regions with periods T < 10 min are investigated. As follows from the wavelet analysis oscillations with periods 3-5 min and 10-40 s had largest amplitudes in the dynamical spectra while oscillations with T < 10 s turned out to be absent. It has been shown that acoustic modes with T < 1 min strongly dissipate in lower corona due to the thermalconductivity. Oscillations with T =10-40 s are found to be connected with the Alfven disturbances. Within the framework of the homogeneous model the influence of acoustic and Alfven oscillations on the thermal mechanisms of microwave radiation is analyzed. The probable sources of the coronal heating are discussed.