Ionospheric and Radio Frequency Propagation Modeling

Werne, Joseph (NorthWest Research Associates)

Franke, Patricia
Nickisch, L.J.


Accurately assessing the performance of High-frequency (HF) communications systems and over-the-horizon (OTHR) radar – both of which are critical for military operations and mission planning – requires accurate modeling of the ionization structure in the ionosphere up to 300-400 km and understanding the effects this ionization has on HF signal propagation. This project engages basic research on fundamental ionospheric processes affecting the structure of the ionization in order to enhance and validate two of the most useful HF-communication and OTH-radar tools available today, namely GPSII and HiCIRF, which we describe briefly below.

GPSII – NorthWest Research Associates is the developer of algorithms and software for assimilative ionospheric modeling and HF propagation analysis. The assimilative ionospheric-modeling package is called GPS Ionospheric Inversion (GPSII; pronounced "gypsy"). GPSII assimilates GPS L1/L2 beacon data and a host of other ionospheric data sources to reconstruct the three-dimensional ionospheric electron-density distribution that reproduces the data to within the errors of measurement.

HiCIRF – High-frequency Channel Impulse Response Function (HiCIRF) is a software package for simulating HF skywave propagation for HF communications and OTH radar studies. HiCIRF can utilize either climatological or GPSII ionospheric models to generate high-fidelity realizations for HF radio-wave signals for studying HF communication and OTH radar performance for hypothesized antenna array geometrics and signal-processing strategies.

In this HPC project, our focus is on improving our understanding of the effects mid-latitude E-region electron density has on the propagation of HF radio signals. By comparing observations with candidate processes that we simulate numerically, our goal is to determine the causes for small-scale ionospheric structure at mid-latitudes. Basic mechanisms we are investigating include gravity-wave breaking, Kelvin-Helmholtz overturning, convective instability responsible for plasma-bubble formation, and wave/wave and wave/mean-flow coupling. The purpose of these studies is to develop results that can be used to enhance, validate, and test the GPSII and HiCIRF capabilities. In this talk we discuss progress made in developing the needed codes and simulating the electron density structure generated by these physical processes.