Detection and Characterization of Traveling Ionospheric Disturbances (TIDs) with GPS and HF sensors

Abstract:

Recently there has been increasing interest and awareness in the coupling between the neutral atmosphere and the ionosphere and specifically in processes that cause wave-like non-stationary perturbations in the bottom-side of the F-region. A class of these perturbations having periods greater than about five minutes and wavelengths greater than a kilometer or so are believed to occur routinely and propagate throughout the ionosphere; they are known as traveling ionospheric disturbances (TIDs). In this study we investigate ground-based techniques for detecting and characterizing TIDs with periods ranging from 30-90 minutes and wavelengths of 10s of km or more. These waves are believed to affect the Doppler and propagation angles of high frequency (HF) radio waves refracting through the affected regions. Wave-like perturbations are also commonly observed in GPS total electron content (TEC) data. In the current study we monitor a number of different commercial HF broadcast transmitters from a station in Wallops Island, VA and collect GPS TEC data from numerous stations along the path between the HF receiver at Wallops and specific HF transmitters. The objective is to understand the relationship between TID signatures on HF and GPS sensors and to possibly characterize TIDs using such observations, including propagation velocity, amplitude, wavelength and potentially source. Given that GPS TEC data are now relatively abundant around the globe, establishing a reliable technique for quantifying TIDs with these measurements would yield an important new technique towards developing a global TID monitoring capability that could support ionosphere-thermosphere coupling science as well as potential monitoring capabilities for natural disasters (e.g., earthquakes, tsunamis, volcanic eruptions) with significant TID signatures.