Cyclotron Emission with a Helical Wavefront from an Electron Accelerated by the Circularly Polarized Wave

In this paper, we calculated the radiation from the state where an electron in cyclotron motion under the uniform magnetic field Bex was accelerated by the externally applied circularly polarized wave with strong Ein and Bin. The electron was accelerated in the parallel direction by the term β⊥ × Bin (β⊥: perpendicular velocity of the electron) as well as in the perpendicular direction by the electric field of the wave Ein. Then, the electron can be resonantly accelerated when the Bex is set to the magnetic field strength which is equivalent to frequency of the externally applied circularly polarized wave. The radiation from such an accelerated electron was confirmed to have helical wavefront at harmonics cyclotron frequency.