Wave-Optics Analysis of HF Propagation through Traveling Ionospheric Disturbances and Developing Plasma Bubbles

Abstract

We apply a wave-optics technique to model the propagation of high-frequency (HF) waves through simulated traveling ionospheric disturbances (TIDs) and developing plasma bubbles at low latitudes. Wave-optics is derived from a forward-propagation approximation of the Helmholtz equation governing the electric field in the frequency domain. The technique is implemented using the split-step Fourier approach commonly referred to as the multiple phase screen method (MPS). At an intermediate step in the computation, the electric field along each phase screen is expressed explicitly in terms of the angular spectrum of plane waves intersecting the screen.We use this approach to produce angle-of-arrival “maps,” which depict the spectrum of angle-of-arrival (AOA) at all locations on the ground. These AOA maps identify all radio propagation modes reaching the receiver along with their individual amplitudes. With the wave-optics approach there is no need to ‘home’ rays to identify the propagation modes that are present. A full-wave technique, wave-optics accurately represents the interaction (via diffraction) between the different propagation modes, which can result in fading of the received HF signal. Ray-tracing techniques neglect diffraction and therefore cannot represent these interactions nor the signal fading they produce.