  The objective of the paper is the assessment of the accuracy of a
conventional FDTD code in the computation of the near and far-field scattering
characteristics of a circular dielectric cylinder. We excite the cylinder with
an electric or magnetic line current and demonstrate the failure of the
two-dimensional FDTD algorithm to characterize accurately the emission rate and
the field patterns near high-Q whispering-gallery-mode resonances. This is
proven by comparison with the exact series solutions. The computational errors
in the emission rate are then studied at the resonances still detectable with
FDTD, i.e. having Q-factors up to 10^3.
