Contribution of surface wave to horizontal magnetic dipole in three-layered media

Abstract

Extremely low frequency (ELF) electromagnetic (EM) wave propagation located in stratified media has attracted considerable interest in recent years. The present study theoretically investigates the contribution of surface waves to EM wave propagation of ELF from a horizontal magnetic dipole (HMD). EM wave propagation has great attenuation in seawater, hence the assumption that no multiple reflection wave exists at the receiver. A set of mathematical expressions based on certain assumptions and simplification can be formulated for a simplified model of three-layered conducting media (air-seawater-seafloor). The simulation results show that surface wave plays a main role on the EM field intensity of longdistance propagation and that the contributions of reflection waves and direct wave can be ignored. The depth of sea impacts the intensity of the total field. The total field is weakened by the seafloor surface wave in the shallow sea. However, its intensity is not impacted when the depth is more than a certain value. Hence, the approach is effective for the research of ELF wave propagation in layered media generated by the HMD.