Abstract
To improve the accuracy of predictions and simplify the difficulty with the algorithm, a simplified empirical model is proposed in developing a long-term predictive approach in determining the ionosphere’s F2-layer critical frequency (foF2). The main distinctive features introduced in this model are: (1) Its vertical incidence sounding data, which were obtained from 18 ionosonde stations in east Asia between 1949 and 2017, used in reconstructing the model and verification; (2) the use of second-order polynomial and triangle harmonic functions, instead of linear ones, to obtain the relationship between the seasonal vs. solar-cycle variations of foF2 and solar activity parameters; (3) the flux of solar radio waves at 10.7 cm and sunspot number are together introduced in reconstructing the temporal characteristics of foF2; and (4) the use of the geomagnetic dip coordinates rather than geographic coordinates in reconstructing the spatial characteristics of foF2. The statistical results reveal that foF2 values calculated from the proposed model agree well with the trend in the monthly median statistical characteristics obtained from measurements. The results are better than those obtained from the International Reference Ionosphere model using both the CCIR and URSI coefficients. Furthermore, the proposed model has enabled some useful guidelines to be established for a more complete and accurate Asia regional or global model in the future.
Highlights
The critical frequency of the F2 layer of the ionosphere is a very important characteristic parameter in various civil and military applications such as high-frequency communications [1], satellite communications [2], navigation [3], timing, radar tracking, detections, locations, and spectrum management [4]
To estimate and demonstrate the predictive capability of the proposed simplified regional and spatial values of fo F2 predicted by the simplified regional prediction model (SRPM) and those predicted by the International Reference Ionosphere (IRI) model (using both prediction model (SRPM) concerning characteristic foF2 values both the temporal the Union of Radio Science (URSI) and CCIR coefficients) were compared with the observed values of fo F2 obtained from the and spatial values of foF2 predicted by the SRPM and those predicted by the IRI model (using both verification stations (Figure 2) along with the Root-mean-square error (RMSE) and the calculated relative differences (RRMSE)
Than that during low solar activity; the overall percentage error difference between IRI and SRPM is the maximum during spring and is
Summary
The critical frequency of the F2 layer of the ionosphere In the absence of real-time measurements, the ionospheric models play an important role in all parts of related research fields For this reason, many empirical models were developed in the past. The empirical ionospheric model has been continually improved and further developed by different groups in the public domain making use of the latest measured data [8,19] or introducing advanced techniques, for instance, artificial neural networks [22] and EOF analyses [23,30,31]. Several studies have shown that there are relatively large discrepancies in the values of the ionospheric parameters predicted by the IRI model and the observational data in equatorial and low-latitude regions, especially in East. The predicted values of the new model will be compared with the measured values and IRI model to validate its effectiveness
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