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Ionosonde measurements obtained at College (64.9°N, 212.0°E), Goose Bay (53.39°N, 299.7°E), Boulder (40°N, 254.7°E) and Wallops Island (37.9°N, 284.5°E) during low solar activity years were used to check the performance of International Reference Ionosphere model to predict the critical frequency of the F2 region (foF2) of the ionosphere. Data were obtained from the University of Massachusetts Lowell DIDBase through internet and correspond to low solar activity years. CCIR and URSI options were used to model calculations. The results show that the modeled values given for Goose Bay, Boulder and Wallops Island are better than those given for the other station. For the middle latitude stations, in general, the deviations between modeled and measured foF2 are lower than 20%. Cases with very good agreement between predictions and measurements have been obtained. The worst predictions are given for the high latitude station. The study of maximum electron density of the F2 region (NmF2) shows cases where the deviation between modeled and measured NmF2 reaches values as high as 40% or more. The effects of these disagreements on ionospheric modelling are stressed. Additional studies considering other solar activities are needed. |
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