Range rate–Doppler correlation for HF propagation in traveling ionospheric disturbance environments



[1] Using ionospheric sounding together with fast computational inverse processing, it is now possible to obtain good real-time ionospheric models for use in geolocation for over-the-horizon (OTH) radar. However, deflection of HF propagation paths by traveling ionospheric disturbances (TIDs) remains a troubling cause of coordinate registration errors. Bandwidth and coverage limitations in ionospheric soundings preclude the ability to model TID structure in real time in most cases. It would be useful if TID-induced path deflections could be related to radar-measurable quantities like Doppler shift. As a first step in studying this possibility, we have considered the relationship between Doppler shift and group range rate for point-to-point HF propagation paths in TID environments. The nature of group range rate–Doppler correlation is exposed in three ways: (1) simple theoretical modeling, (2) ray tracing in simulated TID environments, and (3) analysis of OTH radar measurements of a fixed beacon. It is shown that group range rate and Doppler shift for fixed-point propagation paths are usually proportional with a ratio that depends on whether ionospheric motion or density changes predominate in the TID environment.