  Solar small scale microwave bursts (SMBs), including microwave dot, spike,
and narrow band type III bursts, are characterized with very short timescales,
narrow frequency bandwidth, and very high brightness temperatures. Based on
observations of the Chinese Solar Broadband Radio Spectrometer at Huairou with
superhigh cadence and frequency resolution, this work presents an intensive
investigation of SMBs in several flares occurred in active region NOAA 10720
during 2005 Jan 14-21. Especially long-duration flares, SMBs occurred not only
in early rising and impulsive phase, but also in the flare decay phase, and
even in time of after the flare ending. These SMBs are strong bursts with
inferred brightness temperature at least 8.18*10^11 - 1.92*10^13 K, very short
lifetime of 5-18 ms, relative frequency bandwidths of 0.7-3.5%, and superhigh
frequency drifting rates. Together with their obviously different polarizations
from the background emission (the quiet Sun, and the underlying flaring
broadband continuum), such SMBs should be individual independent strong
coherent bursts which is related to some non-thermal energy releasing and
production of energetic particles in small scale source region. These facts
show the existence of small scale strong non-thermal energy releasing
activities after the flare maxima, which is meaningful to the prediction of
space weather. Physical analysis indicates that plasma mechanism may be the
most favorable candidate for the formation of SMBs. From plasma mechanism, the
velocities and kinetic energy of fast electrons can be deduced, and the region
of electron acceleration can also be tracke.
