  Observations of the solar radio emission in the microwave frequency range
show fine structures consisting of a number of the almost parallel narrow
frequency bands. We interpret these bands as the cyclotron harmonics plasma
emission. This emission is generated by the anisotropic electron beam, which
excites longitudinal waves on the normal Doppler effect resonance. Then the
longitudinal waves convert into the radio emission on the second harmonic of
the longitudinal waves frequency and sometimes into the fundamental one.
Estimations of the magnetic field strength made on the basis of such a model
give the values of the magnetic field in the microwave burst sources as ~
100-200 G. The estimations of density variations are also given.
