Efficiency of the Earth–ionosphere waveguide excitation by ELF sources located in an anisotropic ionosphere

[1] This paper is devoted to the problem of excitation of the Earth‐ionosphere waveguide by the sources located in an anisotropic ionosphere. The ELF range where a single-mode representation of the field can be applied is considered. The generalized theorem of reciprocity makes it possible to find the relation between the field components excited in the waveguide by electric and magnetic dipoles of various orientation. At the location of the emitters in the field of applicability of the quasi-longitudinal approximation, this relation is described by simple analytical expressions. Some results of calculations characterizing the eciency of waveguide excitation by horizontal and radial dipoles and applicability of approximate formulae are presented. The dependencies of the eciency parameters on the frequency, latitude, height of the emitter location, and propagation conditions are analyzed. INDEX TERMS: 6964 Radio Science: Radio wave propagation; 2403 Ionosphere: Active experiments; 2471 Ionosphere: Plasma waves and instabilities; KEYWORDS: Earth‐ionosphere waveguide; ELF radiation; lower ionosphere.