Modeling the Impact of Sporadic-E on Over-the-Horizon Radar (OTHR) in the Polar Region

Abstract

Recent studies have highlighted the frequent occurrence of sporadic-E (Es) layers—thin, localized zones of enhanced electron density—especially in high-latitude and polar regions. To address this, a new statistical model for Es has been incorporated into the Empirical Canadian High Arctic Ionosphere Model (E-CHAIM). The impact of Es on high-frequency (HF) radio wave propagation is examined using 3-D ray-tracing. This study aims to evaluate how Es layers affect key radar parameters for over-the-horizon radar (OTHR) systems. The results indicate that Es layers can significantly improve signal propagation by establishing additional, stable, and usable propagation paths, particularly during nighttime hours when these paths would otherwise not be available. As a result, a broader range of frequencies can be used for transmission. In addition, the shift in reflection height from the F-region to the Es layer necessitates lower elevation angles for OTHR operations, as radar waves must be directed at shallower angles to reach their intended targets.