The Empirical Canadian High Arctic Ionospheric Model (E-CHAIM): N_mF₂ and h_mF₂

We present here the Empirical Canadian High Arctic Ionospheric Model (E-CHAIM) quiet N_mF₂, perturbation N_mF₂, and quiet h_mF₂ models. These models provide peak ionospheric characteristics for a domain above 50°N geomagnetic latitude. Model fitting is undertaken using all available ionosonde and radio occultation electron density data, constituting a data set of over 28 million observations. A comprehensive validation of the model is undertaken, and performance is compared to that of the International Reference Ionosphere (IRI). In the case of the quiet N_mF₂ model, the E-CHAIM model provides a systematic improvement over the IRI Union Radio Scientifique Internationale maps. At all stations within the polar cap, we see drastic RMS error improvements over the IRI by up to 1.3 MHz in critical frequency (up to 60% in N_mF₂). These improvements occur primarily during equinox periods and at low solar activities, decreasing somewhat as one tends to lower latitudes. Qualitatively, the E-CHAIM is capable of representing auroral enhancements in N_mF₂, as well as the location and extent of the main ionospheric trough, not reproduced by the IRI. The included N_mF₂ storm model demonstrates improvements over the IRI by up to 35% and over the quiet time E-CHAIM model by up to 30%. In terms of h_mF₂, over the validation periods used in this study, we found overall RMS errors of ~13 km for E-CHAIM, with IRI2007 overall h_mF₂ errors ranging between 16 km and 22 km. The E-CHAIM performs comparably to or slightly better than the IRI within the polar cap; however, significant improvements are found within the auroral oval.