Lack of interaction and ability to combine between ionosphere models are important problems among them. This study has investigated the interaction between global and regional ionospheric models which are according to the base mathematical functions. Here, spherical Slepian base functions have been suggested for spectral combination. They can be defined in global and regional scales. Two sets of coefficient were assumed for spherical Slepian base function. One set (direct model) is extracted from the direct observation of GPS stations. Another set (indirect model) is derived from spherical harmonic products of Global Ionosphere Models (GIMs). GIM’s efficiency has been modified on a sub-space which was equal to pervious set.

Maximum degree has considered equal to 15 for implementation of spherical Slepian spectral combination theory. Also, the Arctic region has been taken as study area where it is the spherical cap by latitude upper than 60 degrees. Observations of three GPS stations are used for evaluation of models. They have not contributed for direct and indirect modelling. Root Mean Square of Errors (RMSEs) for GIMs, direct, indirect and combining models are equal to 3.7, 2.2, 1.9, 1.4 TECU, respectively. In other words, results show that combining method has improved the ionospheric modelling here. The combining method can decrease the effects of the lack of stations in the indirect model and the inappropriate distribution of stations in the direct one. Therefore, the RMSE of the combining model is less than other models in the Arctic region.