A new algorithm for ground wave propagation based on a hybrid ray‐mode approach

Abstract

The authors consider wave propagation over the spherical, finitely conducting earth in a radially inhomogeneous atmosphere, excited by a vertical electrical dipole. They combine a ray-optical asymptotic approximation (going back to Norton, and using computations of reflection and diffraction coefficients and of the complementary error function with complex argument) and series expansion (Wait approach: normal modes propagating along the surface of the earth, necessitating computations of Airy functions and roots of nonlinear equations) into a more efficient numerical method. The new algorithm can handle mixed land and sea paths and delivers results also in the diffraction and the interference regions. It is compared here against the approximate parabolic equation method (which is applicable in a narrow region around the propagation direction) and against CCIR recommendations; the results are rather good.