Choice of a model of the ionosphere to use in high latitudes

Recently, interest in the high-latitudinal zone of the ionosphere has increased, in particular, several special satellite experiments have been proposed for studying this zone. One of the forms for setting the conditions of the ionosphere is the use of empirical models. Recently, SIMP and E-CHAIM models have been developed, aimed at improving the setting of parameters in this particular area, in addition to the traditionally used IRI model. In this paper, we compare the observational critical frequencies foF2(obs) with the model frequencies in accordance with 4 options: 1) model IRI2016, 2) model SIMP, 3) model E-CHAIM, 4) join usage of observational values of TEC(obs) and the median of the equivalent ionospheric slab thickness τ(med) according to Longyearbyen station in 2010-2014. In addition, the previous results of the IRI2016 model comparison with experiment according to data from other Russian stations are complemented by a comparison with the SIMP and E-CHAIM models. Special attention is paid to disturbed conditions. It is proposed to use in these cases the total electron content TEC. Comparison of the model values of foF2 and experimental medians showed that the IRI and SIMP models do not have advantages against each other, the E-CHAIM model provides 1.5 times the best fit: the average absolute deviations for 5 years were 0.49 MHz for the IRI model, 0.52 MHz for the SIMP model and 0.31 MHz for the E-CHAIM model. The relative deviations were 13.36%, 13.88% and 8.42%, respectively. The E-CHAIM model has an even greater advantage in obtaining foF2 during disturbances: it reflects positive and negative daytime disturbances, nightly enhancements of ionization.