Modeling scattering from lightning-induced ionospheric disturbances with the discontinuous Galerkin method

Abstract

Simulation of the propagation of very low frequency (VLF) waves in the Earth-ionosphere waveguide remains a significant computational challenge as a result of the variable wavelength at these frequencies in the magnetized plasma environment of the lower ionosphere. The discontinuous Galerkin (DG) method is naturally and easily adapted to nonuniform grids and so is ideal for simulation in media where the characteristic length scale varies significantly. We present an automatic procedure based on minimal system realization to incorporate any linear, anisotropic dispersive material in the DG framework, with application to a perfectly matched layer and scattering from strong disturbances in a magnetoplasma. We apply these techniques to modeling of scattering from lightning electromagnetic pulse-induced ionospheric disturbances, calculating the full 3-D scattered VLF wavefields from intense lightning-induced ionospheric perturbations over a large volume. We plot the spatial distribution of the phase and amplitude response as seen by a ground-based receiver over a large area. The results are consistent with previous results from 2-D models, showing maximum received signal strength amplitude perturbations on the order of 0.1 to 0.2 dB for intense vertical discharges under smooth ambient conditions and on the order of 0.5 dB for very intense, repeated horizontal discharges.