Electron Cyclotron Maser with Moderately Relativistic Electrons

Abstract Electron cyclotron maser (ECM) emission is an important coherent emission mechanism for the direct amplification of electromagnetic waves by nonthermal electrons in a magnetized plasma. This paper will report on our recent study on ECM emission by fast electron beams with moderately relativistic energy. The results show that, similar to the spontaneous emission by the magnetic cyclotron motion of energetic electrons in a magnetic field, the coherent emission also exhibits the characteristic of a gradual transition from harmonic emission to continuous emission as the energy of the energetic electrons increases from subrelativistic to relativistic. The effects of the characteristic beam electrons energy ( E c ) and the plasma-to-cyclotron frequency ratio ( ω pe / ω ce ) on the growth rate, the peak-value frequency, and the spectral width are discussed further. These results are helpful for us to understand phenomena associated with astrophysical radio bursts.