Normal waves of the anisotropic Earth—ionosphere waveguide in the VLF-ULF range

Abstract

[1] The problem on determination of the electromagnetic field of a near-Earth horizontal electric dipole in the frequency range 10−1 − 10 Hz at distances 10−1 − 10 km in the Earth–ionosphere waveguide has been solved. The ionosphere is assumed to be horizontally stratified and anisotropic, and the Earth is assumed to be homogeneous to some depth and infinitely conducting below. The representation of the electromagnetic field as expansion in waveguide modes is given. The zero mode is regarded as anisotropic. Local modes are given in the isotropic approximation of the anisotropic ionosphere due to inclusion of an effective exponential conductivity profile. An analytical description of the field reflection for vertical and horizontal polarizations has been obtained for this model. At short distances from the source, the solution coincides with the known solution for the case of the absence of the ionosphere. The range of distances beginning from which the influence of the ionosphere on the near-Earth magnetic field manifests itself has been found.