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Regional model of foF2 for Pakistan using empirical orthogonal function technique


The ionosphere F2 layer is principally used for the reflection of radio waves in high-frequency communication and broadcasting. The ionosphere is used as a propagation medium for HF propagation. Global models like the IRI model may not define variation in the ionosphere of a specific area exactly. Several studies have found significant differences between the ionospheric parameters forecasted by the IRI model and observed data. Regional models provide more accurate data of ionospheric parameters, which can serve to update IRI in Pakistan. Variations in the ionosphere from low to mid-latitude in the F region of Pakistan will be studied. This study will help with navigation and HF communication. A comprehensive study about variation in the ionosphere will help to operate space communication smoothly in this region. It is our aim to construct regional models of ionospheric parameter, foF2, by using empirical orthogonal analysis combined with linear regression method for Karachi (geographic 24.95°N, 67.14°E), Islamabad (geographic 33.75°N, 72.87°E), and Multan (geographic 30.18°N, 71.48°E) stations by using the data from the years 1986–1996. In this study, parameter \({F}_{10.7}\) with a known significant impact on foF2 was used. To evaluate ionospheric response, base functions and their associated coefficients features will be investigated. \({E}_{\mathrm{k }}(h)\) k-the base function represents the diurnal variation of foF2 and corresponding principal components coefficients \({A}_{\mathrm{k}}(d)\) denote the long-term variation such as solar cycle and seasonal variations. \({A}_{1}\), \({A}_{2}\), and \({A}_{3}\) first three EOF coefficients are characterized by the solar cycle, annual, and semi-yearly variation. \({A}_{1}\) represents a long-term trend which shows variation in solar activity. \({E}_{1}\) represents the diurnal variation in foF2. Diurnal variation in foF2 is caused by the ionization and recombination process. The model can reproduce the whole variability of the ionosphere by only the first three components of EOF. To evaluate the model accuracy, results will be compared with observed data and with the IRI model.

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The \({F}_{10.7}\) index data is downloaded from the OmniWeb and ionospheric foF2 data is obtained from Suparco (Pakistan Space and Upper Atmosphere Research Commission) for stations Karachi, Islamabad, and Multan. Special thanks to Madam Madiha Talha for their help and guidance.

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Correspondence to Fozia Hanif.

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Communicated by Zhihua Zhang.

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Ashraf, U., Hanif, F. & Ashraf, S. Regional model of foF2 for Pakistan using empirical orthogonal function technique. Arab J Geosci 15, 568 (2022).

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