Synchrotron deceleration of electrons in a plasma and the generation of electromagnetic radiation

Electromagnetic radiation generated by electrons with several hundred keV of energy gyrating in a dense magnetized plasma has been studied both experimentally and theoretically. Radiation with an intensity several thousand times greater than that generated by the single particle synchrotron process is observed at the second cyclotron harmonic if the background plasma is sufficiently dense. A critical condition for the generation of this radiation is that the upper hybrid resonance frequency of the background plasma be greater than the observation frequency. The observations are related to a relativistic phase trapping of the energetic electrons by an electromagnetic wave propagating perpendicular to the magnetic field. The plasma instability mechanism proposed is in good agreement with the observations.