• It was found that the development of microwave emission sources is nonuniform in character when active regions appear and evolve, and in periods preceding an increase in flaring actvity^1,2.

• The phenomenon of the emission circular poalrization reversal of the active region during its solar disk passage has been investigated. Time dependencies of characteristics of the microwave emission circular polarization reversal process on active region parameters have been obtained^3,4.

• Buildup signatures of powerful flares have been identified:

• from an increase of the degree of correlation of the number of microwave emission bursts and the number of subflares in the active region;

• from the microwave source with increased temperature and small circular polarization above the neutral line of the photospheric magnetic field⁵.

• An efficient criterion of the importance of proton flares has been developed and tested, which allows for the dependence of the character of the polarization distribution on the active region location on the solar disk⁶.

• A technique has been proposed for diagnosing coronal mass ejections from "negative bursts" in the emission of active regions.

• By analyzing 37 microwave bursts observed simultaneously at the SSRT and the spectrograph of the Institute of Applied Physics (University of Bern), it was found that a change in spectrum frequency maximum is always accompanied by a change in spatial structure of microwave emission sources.

Images of the flare-productiveactive region NOAA 7978 of July 8-10, 1996, obtained in the additive-correlation mode. Color - I, profic=les - V. The middle radio source is located above the neutral line