Analysis of a basic electron cyclotron maser model

The interaction process in a cyclotron maser is analyzed with emphasis on the basic physics. It is shown that the key factor in the interaction process is the dependence of the electron cyclotron frequency on the relativistic factor gamma. When the wave frequency is slightly greater than the relativistic electron cyclotron frequency, this dependence leads to stronger interaction for those electrons that initially lose energy and weaker interactions for those that initially gain energy, i.e., it causes the electrons to bunch toward the region in the cyclotron phase space which favors electron energy extraction by the wave.