On the zebra structure in the frequency range near 3 GHz

We present 19 cases of zebra pattern structure (ZPS) and fiber bursts (FB) in radio bursts in frequency range around 3GHz, and one such case in the range 5.2-7.6 GHz, using the new microwave spectrometer of NAOC between 2.6-3.8 and 5.2-7.6 GHz (China, Huairou station) with high resolution (10 MHz and 8 ms). The FB and ZPS have about the same spectral parameters: the frequency bandwidth of emission stripes Deltaf similar to 20 MHz, the frequency separation between the emission and the neighboring low frequency absorption -Deltaf(ea) similar to 30 MHz and the frequency separation between emission stripes (when a periodic structure persists) Deltaf(s) similar to 60-70 MHz. Therefore we consider both these fine structures to be whistler manifestations, i.e., interactions of plasma electrostatic waves with whistler waves (generated by the same fast particles with loss-cone anisotropy) l + w --> t. The duration of the fiber bursts of about 2s corresponds to whistler waves propagating undamped at about 2s, which requires a whistler increment < 0.5 s(-1). In the frequency range 3-7 GHz the relation between the ratios of plasma to cyclotron frequencies and whistler to cyclotron frequencies is almost independent of the decrement of whistler electron damping. This finding is used to obtain the magnetic field strength in the region of generation. For a reasonable value of electron temperature (2-20 MK), we find B = 125-190 G when the electron density is (8-18) x 10(10) cm(-3) and B = 520-610 G when the electron density is (35-60) x 10(10) cm(-3). In two remarkable events, 1998-04-15 and 2000-10-29, the right-hand polarization is strong for all the fine structures and corresponds to ordinary wave.