Centimetric type N and type M bursts

Two special fine structures observed with the 5.2-7.6 GHz high temporal and spectral resolution spectrometer of Beijing Astronomical Observatory (BAO) are described and analyzed in this paper. Because they appear as the lette rs N and M on dynamic spectra, we call them centimetric type N and type M b ursts, respectively. They have very short durations (about 500 ms and 300 m s), small flux densities (tens of SFU), narrow bandwidth (relative bandwidt h about 10%), and very small polarization degree (close to the accuracy lim it of observation instruments), but each branch has considerable high frequ ency drift rates (several GHz/s). We think that they are an extension of me tric or decimetric type U(N) bursts in centimetric wavelengths. Type N and type M bursts may be due to the mirroring effect near the foot point, as we ll as a scattering effect caused by whistler wave turbulence near the top o f loop. They may also be interpreted by the quasi-periodic particle injecti on into coronal loops.