[2] The properties of electromagnetic fields excited in the terrestrial waveguide by low-frequency elementary emitters located in the ionosphere were studied in a series of papers. Various models of the geomagnetic field and terrestrial regular waveguide with the properties depending only on the coordinate orthogonal to the boundaries [see, e.g., Einaudi and Wait, 1971a, 1971b; Galejs, 1971a; Pappert, 1973; Rybachek, 1985, 1995] and irregular waveguide with the properties changing additionally in the longitudinal (tangential) to the boundaries direction [Galejs, 1971b; Rybachek et al., 1997a, 1997b] were used.
[3] In our papers we used the model of a spherical anisotropic waveguide with an arbitrary orientation of the geomagnetic field vector H0. Point electric and magnetic dipoles of arbitrary orientation were considered as the field sources. The cold plasma approximation was used to describe the ionospheric properties. Nonlinear effects were not taken into account.
[4] The solution of the problem of the terrestrial waveguide excitation by ionospheric emitters is found using the generalized theorems of reciprocity for magnetoactive media [Ginzburg, 1970] and is reduced to determination of ionospheric fields created by the dipoles located in the cavity of the waveguide. The latter problem, in its turn, leads to a series of waveguide problems (the source and observation point are located in the waveguide cavity) and to the problem of integration of the Maxwell's equations for anisotropic media. The solution of waveguide problems is obtained by the normal waves method for a regular waveguide [Krasnushkin, 1962] and by the cross sections method for an irregular waveguide [Katsenelenbaum, 1961]. The problem of determination of the fields in the anisotropic ionosphere using the asymptotic separation of variables in the Maxwell's equations is reduced to an integration of the system of differential equations, coinciding in the form with the system describing propagation of plane waves through plane-stratified media [Budden, 1961].
[5] This paper is dedicated to studies of the efficiency of excitation of the Earth-ionosphere waveguide by horizontal and vertical electric and magnetic ionospheric dipoles in the ELF (extremely low frequencies) range where the single-mode representation of the field is mainly applicable.
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