Modelling of VLF radio propagation in the earth-ionosphere waveguide.

Understanding the propagation of Very Low Frequency radio waves in the waveguide formed between the surface of the Earth and the lower edge of the ionosphere is of great interest and practical use.Very Low Frequency radio waves serve as a useful tool to investigate the ionosphere and different factors influencing it, most notably solar conditions and events.In this thesis, two methods of simulating the propagation of narrowband Very Low Frequency radio waves are presented, namely Waveguide Mode Theory and the Finite-Difference Time-Domain method.The principles behind these methods are introduced and the advantages and drawbacks of each are discussed.Wait's two ionospheric parameters, H and β, are used in both cases to simulate the electron density and conductivity of the lower ionosphere; probably the most important factors in this field of study.The two models are first used to investigate some theoretical aspects and concepts.Applications of the models are then illustrated through the use of data from UltraMSK and the DEMETER satellite.