Performance of IRI-based ionospheric critical frequency calculations with reference to forecasting

Senalp, Erdem Turker
Tulunay, Ersin
Tulunay, Yurdanur
Ionospheric critical frequency (foF2) is an important ionospheric parameter in telecommunication. Ionospheric processes are highly nonlinear and time varying. Thus, mathematical modeling based on physical principles is extremely difficult if not impossible. The authors forecast foF2 values by using neural networks and, in parallel, they calculate foF2 values based on the IRI model. The foF2 values were forecast 1 h in advance by using the Middle East Technical University Neural Network model (METU-NN) and the work was reported previously. Since then, the METU-NN has been improved. In this paper, 1 h in advance forecast foF2 values and the calculated foF2 values have been compared with the observed values considering the Slough (51.5 degrees N, 0.6 degrees W), Uppsala (59.8 degrees N, 17.6 degrees E), and Rome (41.8 degrees N, 12.5 degrees E) station foF2 data. The authors have considered the models alternative to each other. The performance results of the models are promising. The METU-NN foF2 forecast errors are smaller than the calculated foF2 errors. The models may be used in parallel employing the METU-NN as the primary source for the foF2 forecasting.


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Mutual coupling calibration is an important problem for antenna arrays. There are different methods proposed for omnidirectional antennas in the literature. However, many practical antennas have non-omnidirectional (NOD) characteristics. Hence, the previous mutual coupling calibration methods cannot be applied directly since the mutual coupling matrix of an NOD antenna array has angular dependency. In this paper, a sectorized approach is proposed with a transformation matrix for mutual coupling calibration ...
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Circular-sectoral arrays of log-periodic (LP) antennas are presented for frequency-independent operation and beam-steering capability. Specifically, nonplanar trapezoidal tooth LP antennas are considered in a circular array configuration, where closely spaced antennas occupy a sector of the circle. Electromagnetic interactions of the array elements, each of which is a complicated LP antenna structure, are rigorously computed with the multilevel fast multipole algorithm (MLFMA). Genetic algorithms (GAs) are ...
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[ 1] Basis functions with linear variations are investigated in terms of the accuracy of the magnetic field integral equation (MFIE) and the combined-field integral equation (CFIE), on the basis of recent reports indicating the inaccuracy of the MFIE. Electromagnetic scattering problems involving conducting targets with arbitrary geometries, closed surfaces, and planar triangulations are considered. Specifically, two functions with linear variations along the triangulation edges in both tangential and norma...
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Citation Formats
İ. ÜNAL, E. T. Senalp, A. YEŞİL, E. Tulunay, and Y. Tulunay, “Performance of IRI-based ionospheric critical frequency calculations with reference to forecasting,” RADIO SCIENCE, pp. 0–0, 2011, Accessed: 00, 2020. [Online]. Available: