Influence of Natural Magnetic Field on the Propagation Characteristics of Different Modes of LF One-Hop Sky Waves in the Day-Night Transition Area

The study of the propagation characteristics of low-frequency (LF) sky waves in the anisotropic Earth-ionosphere waveguide is of great value for the improvement of the accuracy of navigation and timing systems. In this paper, we focus on the one-hop sky-wave propagation characteristics in the day-night transition area in the anisotropic Earth-ionosphere waveguide under the influence of natural magnetic field. The finite-difference time-domain (FDTD) method is utilized to construct a day-night mixed field, and the propagation delay and field strength of a one-hop sky waves are obtained using the fast Fourier transform and inverse fast Fourier transform (FFT/IFFT) spectral-division technique. And the propagation characteristics in the models of day-to-night variation and night-to-day variation under different directions of the natural magnetic field are analyzed, respectively. The numerical results show that the magnetic field in the horizontal direction has the greatest effect on the wave propagation delay and field strength in the nighttime area of the day-to-night path and in the daytime area of the night-to-day path, compared with the magnetic field in the vertical direction and 45° direction.