VLF Electromagnetic Wave Propagation over Large Distances using Time-domain Segmented Long Path Technique

A three-dimensional Segmented Long Path (SLP) technique [1] is used to study both sub-ionospheric and trans-ionospheric electromagnetic wave propagation at Very Low Frequencies (VLF). This approach allows for the efficient calculation of transient electromagnetic fields radiated by impulsive sources (e.g. lightning) over great distances (hundreds of wavelengths) and utilizes the Finite-Difference Time-Domain (FDTD) method. Maxwell’s equations are used to solve for the electromagnetic fields and are coupled with the method of [2] for treating the anisotropic ionosphere. For the trans-ionospheric propagation study, comparisons are made between our method and the full wave solution of [3]. In addition, we examine the differences between existing mode based techniques such as the Long Wavelength Propagation Capability (LWPC) [4] and our model for several case studies.