Effect of Frequency Monitoring System for Over-The-Horizon Radar due to the presence of patches and arcs within the polar cap ionosphere

High frequency Over-the-Horizon Radar (OTHR)provides an economical means to track non-cooperative airtargets over large expanses of land and ocean. Because ofdynamic ionospheric conditions in polar regions, any OTHRwould necessitate a system where the operating frequenciesand elevation angles change periodically to maintain constantdetection of targets downrange. In this regard, an accurateelectron density model is necessary for the purpose of improvingoperational OTHR and OTHR planning/design. Observationsover recent years have established that large-scale electrondensity structures are a common feature of the polar cap F-region ionosphere. These structures take the form of convectingpatches and arcs of enhanced electron density which form tiltedreflection surfaces for HF radiowaves, allowing off-great circlepropagation paths to be established. Numerical ray tracing hasbeen employed to simulate the effects of these structures on theray paths of the radiowaves. The effect of frequency monitoringsystem for OTHR due to the presence of patches of enhancedelectron density within the polar cap ionosphere has been studiedin this paper.