SEASONAL ANOMALIES AND IRI-2016 PREDICTION OF F2-LAYER CRITICAL FREQUENCY UNDER GEOMAGNETIC ACTIVITY RECURRENT CONDITIONS DURING SOLAR CYCLES 21 AND 22 AT OUAGADOUGOUSTATION

The ionosonde values of F2-layer critical frequency at Ouagadougou under recurrent geomagnetic activity during solar cycles 21 and 22, show a mild winter anomaly during the morning from 0900LT to 1000LT, in afternoon from 1500LT to 1700LT and during the night from 2000LT to 2300LT.URSI and CCIR subroutines reproduce this anomaly in accordance with the experimental values during the night from 2100LT to 2300LT.The Spring and autumn experimental profiles are similar, with absolute values of the relative deviation lower than 10%. The modeled profiles during these seasons are similar and no equinoctial asymmetry is reported except in the morning from 0200LT to 0500LT with CCIR. The ionosonde values does not predict a semi-annual anomaly. Like the experimental results, IRI-2016 model does not predict this anomaly except from 0000LT to 0300LT with the CCIR. The model gives a good estimate of the equinoctial asymmetry and the semi-annual anomaly. As for the winter anomaly, the predictions of the model during the day are contrary to the ionosonde measurements.