Theory of ELF Wave Propagation in a Layered Anisotropic Oceanic Lithosphere Waveguide

In this study, we investigate the theory of extremely low-frequency (ELF, below 30 Hz) wave propagation within a layered, anisotropic oceanic lithosphere waveguide. By considering the anisotropic properties of the lower layer of the waveguide, we derive the reflection coefficients for the guided modes. The modal equation for the anisotropic case is developed and solved by evaluating the reflection coefficients of the upper and lower waveguide boundaries. Analytical expressions for the propagating mode and field strength under anisotropic conditions are presented. Calculations and analysis reveal that when the transverse conductivity of the lower boundary is greater than its longitudinal conductivity, the field strength is marginally reduced compared to the isotropic case. Additionally, when the medium conductivity is anisotropic, the antenna pattern differs from the isotropic case and exhibits an asymmetric distribution.