HF Sounder Characterization of Traveling Ionospheric Disturbances using the N-Dimensional Lomb-Scargle Periodogram
Ian Collett, Joseph A. Hughes, Scott Alan Thaller, Camella Nasr, Anastasia M. Newheart, A. Reynolds, Dan Knight, Geoff Crowley · 2025
Traveling ionospheric disturbances (TIDs) are electron density fluctuations that travel as waves through the ionosphere.Measuring TIDs with HF sounders and other instruments enables the scientific and operational community to better understand the response of the ionosphere and predict its impact on technological systems.Orion Space Solutions is developing a next-generation HF sounding system called the Traveling Ionospheric Disturbance Evaluation Tri-wave (TRIDENT) sensor.This paper describes a novel TID characterization algorithm that we have developed for TRIDENT.The algorithm is based on the N-Dimensional Lomb-Scargle Periodogram (ND-LSP) spectral analysis technique and marks the first application of the ND-LSP to HF Doppler data.The performance of the algorithm is demonstrated in two cases using simulated observations.In the first case, the ionosphere is perturbed with a superposition of three TIDs and the algorithm can characterize each individual TID from the synthetic HF measurements of Doppler frequency.In the second case, the ionosphere is perturbed with a single TID of large enough amplitude to produce multiple off-great circle propagation modes through the F region of the ionosphere.The ND-LSP can handle multiple simultaneous measurements on a single transmit-receive link and, by including angle of arrival information, estimates the TID characteristics accurately.