Quasidiscrete spectrum Cherenkov radiation by a charge moving inside a dielectric waveguide

We investigate the Cherenkov radiation by a charge uniformly moving inside a dielectric cylindrical channel in a homogeneous medium. The expressions for the Fourier components of the electric and magnetic fields are derived by using the electromagnetic field Green tensor. The spectral distribution of the Cherenkov radiation intensity in the exterior medium is studied for the general case of frequency dispersion of the interior and exterior dielectric functions. It is shown that, under certain conditions on the dielectric permittivities, strong narrow peaks appear in the spectral distribution. The spectral locations of those peaks are specified and their heights and widths are estimated analytically on the base of the dispersion equation for the electromagnetic eigenmodes of the cylinder.