Modeling of the Ionospheric Critical Frequency of the F2 layer over Asia based on Modified Temporal‐Spatial Reconstruction

A model based on modified temporal‐spatial reconstruction is proposed to improve the accuracy of predicting the monthly median ionospheric critical frequency of the F2 layer. This model has three new characteristics. (1) The solar activity parameters of the 10.7‐cm solar radio flux and sunspot number are together introduced into temporal reconstruction. (2) Both the geomagnetic dip and its modified value are chosen as features of the geographical spatial variation for spatial reconstruction. (3) Harmonic functions are used to represent the ionospheric critical frequency of the F2 layer, which reflects seasonal and solar cycle variations. Furthermore, combining the least squares fitting regression for these characteristics with harmonic analysis, a valid model can be established from vertical sounding data spread across three ionospheric regions (high, middle, and low latitudes in Asia). Statistical results reveal that the ionospheric critical frequency of the F2 layer calculated by the proposed model is consistent with the trend of the monthly median observations. The average root‐mean‐square error is only 0.70 MHz (corresponding to relative error 11.30%), reflecting that our model outperforms the International Reference Ionosphere model with International Union of Radio Science and Consultative Committee on International Radio (CCIR) coefficients. Moreover, the proposed method has great potential in terms of providing higher prediction accuracy for ionospheric parameters on the global scale. Plain Language Summary The critical frequency of F2 layer of ionosphere is a very important characteristic parameter in various civil and military applications. To further improve the accuracy of predicting the monthly median ionospheric critical frequency of the F2 layer, a new model based on modified temporal‐spatial reconstruction is proposed. This model was established from vertical sounding data collected at 33 stations spread across three ionospheric regions (high, middle, and low latitudes in Asia). To use the new model requires only the following inputs: latitude, longitude, month, hour, the 12‐month running mean value of the monthly flux of solar radio waves at 10.7 cm, and sunspot numbers. Statistical results reveal that the ionospheric critical frequency of the F2 layer calculated by the proposed model is consistent with the trend of the monthly median observations. The average root‐mean‐square error is only 0.70 MHz (corresponding to relative error 11.30%)