A statistical study of long-lived solar microbursts (MB) at
decimeter-wave frequencies has been performed for the first time. The
data are obtained with the radio telescope RATAN-600 and have the form
of one-dimensional scans of intensity and circular polarization with a
sensitivity of about 5 10 Jy. MB fluxes and polarization degrees lie in
the 0.001 0.1 s.f.u. and 10% to 100% intervals, respectively, and
individual pulses have durations of one to two seconds. Microbursts can
be observed in the same active region over several days. MB are compared
to noise storms (NS) at meter-wave frequencies. The analysis indicates
that MB are NS manifestations at decimeter-wave frequencies. The
possible cause of the significant difference between the radio fluxes of
MB and NS is analyzed. It is shown within the framework of a unified
model of the generation of MB and NS radio waves that unlike type I
bursts MB are associated with the incoherent mechanism of the generation
of Langmuir waves. MB emission is, by its nature, closer to the
continuous emission of noise storms, but it is pulse-like because of the
high rate of pitch-angular diffusion.