Curvature radiation for intermediate pitch angles

The radiation by a charged particle in a non-uniform magnetic field is analyzed when the particle’s trajectory forms a curved spiral. The case when the pitch angle is less than the inverse of the Lorentz factor is considered. It is shown that the spectral angular distribution of the radiation consists of two parts that are substantially separated in frequency. One of these components represents curvature radiation, which is primarily linearly polarized, while the other possesses the typical properties of undulatory radiation, with a high degree of circular polarization. The derived formulas can be used to analyze the radiation of pulsars.