The propagation of ELF and VLF radio waves beneath an inhomogeneous anisotropic ionosphere

Abstract Computations have been made of the attenuation and phase velocity of ELF and VLF radio waves propagating under a realistic anisotropic ionosphere. The anisotropy produced by the Earth's magnetic field has been found to have its greatest effect on propagation at frequencies in the range 1–4 kHz where differences in attenuation of greater than 45 dB/1000 km have been observed between West to East and East to West propagation in the least attenuated mode. The computed values of attenuation constant have been found to be in very good agreement with the existing experimental data except for the heavily attenuated region. The computed values of phase velocity, however, do not show such a good agreement with experimental data. It is concluded that if future experimental observations of attenuation constant and phase velocity are to be of any practical value for determining ionosphere profiles, the azimuth of the propagation paths for which these constants are determined must also be recorded.

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