Computationally Efficient Analysis of Complex Sferic Waveform Parameters for Remote D-Region Sensing

The ionosphere’s D-region and the Earth’s surface form what is known as the Earth-ionosphere waveguide (EIWG), facilitating long-distance propagation of VLF signals within this waveguide. Lightning discharges emit VLF signals, known as sferics, which can travel hundreds or thousands of miles in the EIWG with little degradation. The characteristics of lightning sferic waveforms are impacted by the D-region along the path of propagation between the source of the strike and the receiver. Thus, sferics are exceedingly useful for remote sensing of the D-region. In this work, we present several parameterized models of lightning sferics to aid in the analysis of the D-region. These models are then applied to large VLF datasets obtained during typical atmospheric conditions and during abnormal geophysical events, and the resulting variation in distributions of the sferic parameters are analyzed.