Microwave radiation of solar active regions before X flares according to the RATAN-600 observations in 2011

The evolution of the microwave radiation from four active regions, where strong X-ray flares (X-class, GOES) occurred in 2011, has been studied. Daily multiwavelength RATAN-600 radio observations of the Sun in the 1.6–8.0 cm range have been used. It has been indicated that the radiosource above the photospheric magnetic field neutral line (above the region with the maximal convergence of the fields opposite in sign) becomes predominant in the structure of the active region microwave radiation one to two days before a powerful flare as in the eruptive events previously studied with RATAN-600. The appearance of such a radiosource possibly reflects the current sheet formation in the corona above the active region. The energy necessary for a flare is stored in the magnetic field of active region, which can be considered as a factor for predicting a powerful flare.