The results of a study to improve the global maps of monthly median values of the F2 region critical frequency, f0 F2, using values determined from a theoretical model are presented. Values of the midlatitude F2 region critical frequency that could be used to improve the prediction of f0 F2 in regions of the earth inaccessible to ground-based measurements were obtained. This was accomplished by including in the theoretical calculations realistic physical processes along with a realistic geomagnetic field model. Parameters were adjusted so that agreement was achieved between calculated and observed f0 F2 values as a function of local time at different stations, and then these same input parameters (i.e., neutral wind field, and neutral atmospheric model) were assumed valid at all regions of interest where the major difference is the geomagnetic field line configuration. Coefficients that yield global representations of f0 F2 were then determined using the theoretically derived f0 F2 values, and the predicted critical frequencies were compared with observed values to estimate the degree of improvement.
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