| Summary: | High Frequency (HF) radio propagation, and applications such as Over-The-Horizon Radar (OTHR), is sensitive to ionospheric disturbances caused by space weather. Improved ionospheric modelling and monitoring techniques for the high-latitude and polar regions supports high quality OTHR long-range surveillance. One such ionospheric disturbance is Sporadic-E, a phenomenon in which a thin enhancement in E-region (approximately 90–150 km altitude) electron density acts as a strong reflector of HF radio waves. In this study, we perform a case study of the effect a sporadic-E layer has on HF radio propagation for a layer that was detected over Eureka on July 11, 2012. We study this event using HF radio receiver measurements for a path intersecting the layer, simultaneous ionosonde measurements of the layer, and a series of ray traces through a model ionosphere containing a model of the sporadic-E layer. Utilizing these measurements and simulations, we show how sporadic-E can aid HF radio propagation in some cases, and show that a simple Gaussian sporadic-E model can replicate real HF radio measurements. We also comment on how sporadic-E could affect OTHR operation.
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