Harmonic structures of gyrosynchrotron radiation and cyclotron maser instability

The harmonic structures of the gyrosynchrotron radiation are studied and co mpared with the results of the electron cyclotron maser instability. The st ructures only appear at lower harmonics (s < 10), and their peaks deviate b y a small amount from integer harmonic numbers. The amplitudes of harmonic structures of the extraordinary modes are usually larger than that of the o rdinary modes. The numbers and amplitudes of harmonic structures increase w ith increasing electron energy spectral index delta and propagation angle t heta. All the properties of harmonic structures are consistent with the pre dictions of the electron cyclotron maser instability in an extremely magnet ized plasma on the basis of Maxwell and Vlasov equations. The physical rela tions between gyrosynchrotron radiation and cyclotron maser instability and a possible application of the properties of the harmonic structures are di scussed.