LAUSR

The analytical formulas are obtained for the tangential components of an extremely low-frequency electromagnetic field in the Earth–ionosphere plane waveguide excited by a grounded linear horizontal antenna. The behavior of the surface impedance is studied as a function of the electrodynamic characteristics of the waveguide and the distance from the source. It is shown that the surface impedance coincides with the plane wave impedance on the Earth’s surface at distances from the source larger than the skin depth provided that the skin layer is thinner than double the waveguide’s height. The influence of the ionosphere on the amplitude of an extremely low- and lower frequency magnetic field and, thus, on the impedance at the shorter distances than two ionospheric heights is theoretically substantiated. This type of effect was observed in the experiments conducted on the Kola Peninsula, where the low conductivity of the Earth allowed the detection of the effect of the ionosphere on the amplitude of the magnetic field in the low-frequency band.