Modelling the effects of solar activity on the ionospheric F2 critical frequency over Wakkanai

For many decades ionospheric researchers investigated the variations in the ionosphere due to solar activity. The suggested relevant models are based on singlestation data, considering regional and global geographic conditions. The present study investigated the impact of the solar cycles 21st (1976 to 1986) and 23rd (1996 to 2008) on the ionospheric F₂ layer’s critical frequency (f₀F₂) at mid-latitude over the Wakkanai region (45.39º N, 141.68º E), Japan. The statistical analyses showed that monthly median f₀F₂ has a significant non-linear association with high sunspot numbers (SSN) over Wakkanai, which represents a saturation effect depending on the time of the day in different months and on the magnitude of the solar cycle. Polynomial empirical models of f₀F₂ based on parameters such as SSN and geomagnetic index Ap were examined. Considering the rate of change in solar activity factor much improved the accuracy of our empirical model and also reduces the hysteresis effect. The most appropriate empirical model for single-station diurnal models of f₀F₂ was developed using Fourier series. Diurnal models incorporate Japanese standard time, months and sunspot numbers. The computed f0F2 models were compared with the IRI-2012 model’s predicted f₀F₂ values, which demonstrated the better accuracy of the Fourier model compared to the global IRI model. The models obtained in this study are useful for researchers and organisations working in the field of sunspot performance relating to the dynamics of the ionosphere.