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 \times 10 ^ { 11 } - 1.92 \times 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 tracked .