Forecasting the Propagation of LF-MF-HF Radio Waves over Ice Paths

The field of a vertical electric dipole over a homogeneous impedance surface is considered. A method for calculating the attenuation function of the ground wave field over a flat surface is given. The effects associated with the presence of a surface wave at highly inductive impedances when a signal is received at different heights above the surface are considered. The electromagnetic field exhibits a clearly expressed surface character. It is shown that the conditions for the propagation of LF-MF-HF radio waves over the structure “ice-sea” with highly inductive impedance are more favorable than over the sea without ice due to the occurrence of surface electromagnetic waves (SEW). It has been established that the conditions for the propagation of radio waves over ice paths depend on the frequency, ice thickness and distance from the transmitter.

I. Introduction

The functioning of numerous radio-engineering systems is based on the use of ground radio waves that propagate along the earth’s surface and are not influenced by the ionosphere. The ground wave has the advantage, first, in the stability of its amplitude-phase structure and in the possibility of propagation over long distances in the LF-MF radio wave bands. Many works are devoted to the problems of propagation of ground radio waves, among which the first works of A. Sommerfeld [1], G. Weil, J. Watson, V.A. Fock [2]. In the middle and late 20th century, the theory of radio wave propagation continued to be developed by other researchers. They obtained practical models for calculating electromagnetic fields. G.I. Makarov [3] and J. Wait [4] made the most important contribution to solving the problem for the model of the medium, which has inhomogeneities in the depth of the earth’s structure. Propagation over highly inductive paths, which are possible only with inhomogeneous media, at some distances from the source may be characterized by the fact that the field level will exceed the field level above a perfectly conducting surface. This effect was experimentally confirmed by the researchers of the Laboratory of Electromagnetic Diagnostics of the Institute of Physical Materials Science (Ulan-Ude, Russia) when measuring the field levels in the HF frequency range on the ice of a salt lake [5],[6]. In addition, at some distances, the field can change non-monotonically due to the presence of SEW. Previously, such effects were associated only with waves reflected from the ionosphere.