Propagation Characteristics Of Very Low Frequency Electromagetic Waves In Earth-Ionosphere Waveguide

Very low frequency(VLF)radio waves have a frequency range of 3 kHz to 30 kHz.They are widely used in timing,navigation,and seismic prediction due to their long wavelength,low loss,stable amplitude,stable phase,and high permeability.The complex propagation mechanism and propagation environment of VLF make it difficult to realize the high-precision and real-time prediction.It is of great theoretical value and practical value to study the propagation mechanism of very low frequency waves and construct a high-precision prediction model for very low frequency wave propagation.Based on the theory of the very low frequency analytical method,this paper studies the propagation mechanism and propagation characteristics,and introduces the International Reference Ionosphere(IRI)and NRLMSISE-00 atmospheric models into the analytical method to explore the method of its high-precision and real-time prediction.The specific work is as follows:Firstly,using the analytical method,the propagation mechanism of the very low frequency waveguide is studied.The radiation field of the vertical electric dipole in the ground-ionosphere waveguide is deduced and calculated,and the characteristics of the ionosphere and formation medium in the waveguide are briefly introduced.Secondly,combined with the exponential model of the ionosphere,a comprehensive simulation analysis of the propagation characteristics of the very low frequency in the earth-ionosphere waveguide is carried out.The simulation and analysis of the effects of field strength with distance attenuation,multimode interference,radiation source parameters and waveguide media parameters on propagation characteristics are carried outThirdly,the IRI model and the NRLMSISE-00 atmospheric model are combined to obtain the ionospheric parameter information closer to the actual environment.Based on the analytical method,the VLF field strength daily variation prediction model is established,it can effectively realize the prediction and analysis of the variation characteristics of VLF field strength at different times in a day,the prediction results are in good agreement with the measured results,and the VLF propagation characteristics were analyzed when the ionospheric electron density,electron temperature,and neutral particle density were disturbedThe purpose of this paper is to provide a theoretical basis for VLF navigation timing and earthquake prediction for the high-precision prediction exploration method of VLF propagation characteristics.