Physical Model of D-Region Ionosphere and Preliminary Comparison with IRI and Data of MF Radar at Kunming

Based on the ion continuity equation solved under chemical equilibrium, a physical model of the D-region ionosphere (60-90 km) is established. The model involves 145 ion chemical reactions and includes 23 kinds of positive ions, 11 kinds of negative ions, and electrons. The simulation results show that molecular ions, such as NO+, NO+(H2O)(n), H+(H2O)(n), CO3-, and O-3(-), are the main components of ions in the D-region. The diurnal change of electron density at low latitudes is more obvious than at high latitudes. Preliminary comparisons with the International Reference Ionosphere (IRI) model and observed data of Medium Frequency (MF) radar at Kunming Radio Wave Observation Station show that the model is able to describe the basic features of D-region parameters. In addition, the results show that the minimum height of the D-region lower boundary in the low latitude is approximately 65 +/- 1 km, and the height during the daytime is strongly correlated with local time. Furthermore, the results also reveal that the asymmetry of electron density is observed, with higher electron density during sunset than during sunrise at 75-85 km altitude. These above results are helpful for better understanding the variation of the D-region.