An extension for the model IMAZ for large absorption

The empirical Ionospheric Model of the Auroral Zone (IMAZ) is based on more than 100,000 electron density profiles measured by the European Incoherent Scatter Radar EISCAT combined with about 100 from sounding rockets. The mathematical procedure applied is a neural network (NN) which works fine as long as one requests predictions from inside the so-called input space, but predicting situations outside it, i.e. for conditions not or only poorly covered by data, are in general utterly unrealistic. An analytical procedure is presented which reasonably extrapolates the NN results for conditions inadequately covered by input data.