Inverse low ionospheric characteristic parameters based on VLF signals of NWC station

Based on earth-ionospheric spherical waveguide model, VLF magnetic field signal in waveguide is simulated to analyze the influence of environmental parameters on signal propagation characteristics. A method for inverting the characteristic parameters of low ionosphere is proposed based on the propagation characteristics of VLF signals in waveguides. Magnetic rod antennas were used to form a receiving array to measure magnetic field signals at multiple locations along the propagation path of the Australian NWC station in Yining area of Xinjiang. The measured magnetic field signals are separated into a series of mode superpositions using Newtonian iterative method and the eigenvalues of each wave mode are obtained, including amplitude and phase information. Characteristic parameters of low ionosphere are determined by joint inversion of the data derived from iterative algorithm with the calculations of ground-ionosphere waveguide model.