Model of the E-Layer Critical Frequency for the Auroral Region

A new foE model for the auroral region is constructed; the model is based on an analysis of the models of auroral electron precipitations, the boundaries of the discrete and diffusive aurora, the main ionospheric trough, and measurements of the E-layer critical frequency foE. The model is an analytical model. It consists of solar (foE(sol)) and auroral (foE(avr)) components. The solar component of the model does not depend of geomagnetic activity. It depends on solar activity via the F index, which is determined by the solar radio emission flux at a wavelength of 10.7 cm over the previous day and three solar rotations. The auroral component of the model does not depend of solar activity. It depends on geomagnetic activity via the effective Kp* index, which takes into account the prehistory of changes in this activity. The model indirectly takes into account the dependence of the relative contribution of foE(sol) and foE(avr) to the total foE value on the difference in the heights of the maxima of these model components via the addition of a coefficient. The model qualitatively takes into account the effect of the winter anomaly in foE(avr) via the addition of a function. It is found that the errors of the new foE model in the auroral region at the nighttime hours are much lower than those in the international IRI model (with the STORM-E option) for both moderate and high geomagnetic activity. For example, the comparison with data from ionospheric stations shows that the IRI model underestimates foE in these conditions by approximately a factor of 2 on average. The average shift in foE relative to the experimental data in the new model does not exceed 20%.