Evaluation of the efficiency of a model of the decameter radiowave propagation environment

We present a concept regarding the effectiveness of ionospheric models in maximum usable frequency (MUF) forecasts according to the fitting criterion for daily progress in predicted and experimentally observed MUFs. For example, it is shown using the daily variability in the MUF on two one-leap paths that an MUF model on the basis of a long-term IPG forecast is characterized by efficiency within 0.8. It is shown using the same two paths that a forecast on the basis of the International Reference Ionosphere (IRI) model has the same efficiency. A model of the effectiveness probability density function is constructed on the basis of a generalization of the method of nonholomorphic functions.