Daytime VLF modeling over land and sea, comparison with data from DEMETER satellite

Very Low Frequency (VLF) radio waves propagate with little attenuation within the Earth-ionosphere waveguide. Perturbations of the lower ionosphere produce a modification of the geometry of the waveguide, resulting in a disruption of the VLF propagation conditions. A model based on the Wait´s mode theory is developed to investigate temporal and spatial changes in ionospheric conditions. As VLF waves propagating from a transmitter reflect off the lower ionosphere, a portion of the energy leaks up into space leaving a `fingerprint´ of the modal structure of the fields at the reflection height. Simulations are compared to averaged data taken over a year from the DEMETER satellite over the NWC transmitter in North-West Australia to test the validity of the model.