Performance Evaluation of Modified IRI2016 and Its Application to the 24 hr Ahead Forecast foF2 Mapping Over China

Abstract

The F2 layer is the uppermost layer of the ionosphere, which plays an important role for long distance high frequency (HF) communication because of its thickness and minimal attenuation for probing radio waves. The F2 layer critical frequency foF2, which determines the maximum useable frequency in the HF band reflecting from the ionosphere, is one of the most pivotal parameters for the HF communication. However, in the real ionosphere, there are many "anomalies" observed in the F2 layer (Rishbeth, 1998(Rishbeth, , 2000Wills et al., 1994), such as the "winter anomaly," the "seasonal anomaly," the "semi-annual anomaly," and the "annual anomaly" of foF2. In addition, the variation of foF2 also depends on the solar activity (Balan et al., 1998;Yu et al., 2004) and magnetic activity (Stanislawska et al., 2002). Therefore, accurate measurement and determination of foF2 has become a key point for the HF communication systems (Ssessanga et al., 2015;Wichaipanich et al., 2017).However, due to the paucity of ionospheric measurements, a number of empirical ionospheric models have been developed to model and predict the spatial and temporal structures of the ionosphere. The most commonly used global empirical ionospheric model for predicting the foF2 is the International Reference Ionosphere (IRI) model. The IRI model can estimate and predict the ionospheric parameters especially the foF2 with appropriate inputs (Wichaipanich et al., 2017). The IRI model has been steadily improved with newer data and with better mathematical descriptions of ionospheric spatial/temporal variation patterns, and IRI2016 is now the latest version (S. Wang et al., 2016), which can be accessed from https://ccmc.gsfc.nasa.gov/pub/modelweb/ionospheric/iri/ iri2016 (Bilitza et al., 2017).The IRI model normally gives a complete spatial and temporal representation of the average state of the ionosphere based on available data from the ionosonde stations, incoherent scatter radars, alouette topside sounders, rockets and in situ measurements on several satellites (