  The asymptotic closed-form solution to the fundamental diffraction problem of
a linear horizontal Hertzian dipole radiating over the metallo-dielectric
interface is provided. For observation points just above the interface, we
confirm that the total surface near-field is the sum of two components: a
long-range surface plasmon polariton and a short-range radiative cylindrical
wave. The relative phases, amplitudes and damping functions of each component
are quantitatively elucidated through simple analytic expressions for the
entire range of propagation: near and asymptotic. Validation of the analytic
solution is performed by comparing the predictions of a dipolar model with
recently published data
