A Review of Grid-Based, Time-Domain Modeling of Electromagnetic Wave Propagation Involving the Ionosphere

The ionosphere plays a critical role in many electromagnetics applications, ranging from long-distance communications to geolocation and satellite communications. As a result, it is of paramount importance to have accurate models of the impact of the ionosphere on electromagnetic wave propagation. Numerous approaches have been suggested over the years to address this problem, including ray tracing, mode theory, and grid-based methods. This paper summarizes the development and applications of grid-based, time-domain methods for predicting electromagnetic wave propagation in the ionosphere. The advantage of these models is their ability to account for detailed inhomogeneities of the ionosphere as well as their ability to model wideband sources and realistic source waveforms (such as lightning strikes). First, different classes of ionospheric algorithms are provided, along with how the required ionospheric parameters are obtained. Second, an overview of the grid-based, time-domain models that have been used to simulate electromagnetic propagation in the ionosphere are described, ranging from 2-D and 3-D FDTD models to FETD and DGTD approaches. Finally, a list of key applications of these models is provided.