Efficient Ray Tracing for Exploring TEC Estimation Uncertainty from On-orbit Recovered VHF Lightning Events

Abstract:

Radio-frequency (RF) lightning emissions, when detected on an on-orbit RF antenna, can be used to estimate total-electron content (TEC) along the trans-ionospheric propagation path. This data can provide spatially unique measurements to that of ground-based GPS TEC measurements, particularly for space weather forecasting over areas where ground stations do not exist (e.g. oceans). However, lightning RF emissions occur in the VHF frequency range, with the ionosphere propagation more affected by ray bending than for L-band GPS signals. Quantifying the error from these on-board measurements is crucial for assimilating this data into future forecasting tools. This study explores the effect of the ray bending on the VHF band TEC estimates by simulating the propagation through a stratified ionosphere medium using the first-order Appleton-Hartree index of refraction and Bouger’s formulation. By using the time delays calculated from the ray tracing model, we attempt to quantify the uncertainty of the TEC estimates in different VHF bands by comparing to a truth (NeQuick2) ionosphere.