This work concerns the comparative study of the diurnal variation of the critical frequency of the F2 layer (foF2) between experimental data from the Dakar station and those of the IRI 2016 model through its URSI. The comparison was made during the solar cycles 21 and 22, during different phases and on different days of geomagnetic shock activity. The results show that at solar minimum, the graphs of the experimental data globally show the signature of vertical drift, whereas the IRI model gives us a plateau profile characterizing the absence of electrojet. During this phase, the highest values of the deviation percentages were around sunrise. They also show that, at Dakar station, the increasing phase was characterized by a pre-reversal of the electric field on the different shock days. Whatever the duration of the shock, the decreasing phase was marked by the total absence of electrojet recorded on the graphs of two data sets. The quantitative study shows that at solar maximum, our results give a good correlation between the experimental data and the IRI model. During all phases, predictions were good during the daytime and show high values around sunrise.

Keywords: foF2, geomagnetic shock activity, IRI model 2016 prediction, solar cycle, Sub-programme URSI