Detection of prolonged, extremely faint decimeter bursts on the sun

We report the detection of long-lived sources of radio bursts accompanied b y polarized background emission in solar active regions. Both types of radi o sources were detected at several decimeter wavelengths in observations on the RATAN-600 radio telescope in one-dimensional scans in intensity and ci rcular polarization with a sensitivity of about 5-10 Jy. The degree of pola rization is from 70 to 100%. The microburst and background sources exist fo r several days and appear at sites of prolonged energy release. The typical duration of an individual microburst is about 1-2 s, and the time interval between microbursts is about 3-5 s. A negative microburst frequency drift of about 100 MHz/s or more is also observed. Some interpretations of the mi croburst and background sources are discussed. The most probable microburst model involves the generation of radio emission via the plasma mechanism, with the upward propagation of fast electrons above an active region. In th is case, the required energy of the Langmuir waves is 2 x 10(-8) of the hea t energy of the background plasma. Microbursts appear in different places i n an active region. New methods for determining the magnetic-field intensit y in the regions of generation of the decimeter-wavelength emission are pro posed. (C) 2001 MAIK "Nauka/Interperiodica".