IEEE Access (Jan 2023)
Propagation Characteristics of Extremely Low-Frequency Electromagnetic Waves in a Uniformly Infinite Polar “Sea-Sea Ice” Half-Space
Abstract
In this study, we accurately calculated the propagation characteristics of extremely low-frequency (ELF) electromagnetic waves (EMWs) excited by horizontal electric dipoles (HEDs) in the uniformly infinite polar “sea-sea ice” half-space. This was achieved by combining the program platform written by the message passing interface (MPI) with the three-dimensional total field scattered field source finite difference time domain (TSS-FDTD) method to develop an improved calculation method of parallel TSS-FDTD electromagnetic field. Using equivalent principle and boundary grid field value transformation technology, the calculation space of electromagnetic field (EMF) in seawater and sea ice is divided into several regional grids to establish the calculation model of TSS-FDTD in the polar “sea-sea ice” half-space. The maximum radiation direction and average minimum attenuation of ELF EMF in the uniformly infinite polar “sea-sea ice” half-space (near the interface between seawater and sea ice) are obtained. The simulation results show that, at depth ${d}$ = 10 m and propagation distance $\rho $ = 125 m from the interface between seawater and sea ice, the maximum radiation directions of EMF intensity are vertical electric field direction $E_{z}$ and horizontal magnetic field direction $H_{x}$ , respectively; moreover, their average minimum attenuation values in the sea water medium are 30 dB and 20 dB, respectively, and their corresponding values in sea ice medium are 20 dB and 10 dB, respectively. Therefore, compared with the directions of other electric and magnetic field components, these directions more suitable for receiving underwater signals. Finally, we selected different thickness values of the sea ice medium for simulation, and compared the results with the Sommerfeld numerical integration method (SNIM) proposed by Pan. The results show that the calculation results of the two methods are consistent, and that the average error is less than 5%, which verifies the effectiveness and accuracy of the proposed method.
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