REGIONAL MODELLING AND MAPPING OF THE IONOSPHERIC CHARACTERISTIC PARAMETERS BY SPHERICAL CAP HARMONIC EXPANSION

Abstract The method of Spherical Cap Harmonic Analysis, SCHA /1/, has been applied to the critical frequency of the F 2 layer observed at several European vertical incident ionospheric stations. The aim was the regional mapping and modelling of this parameter in Europe. To make it possible a spherical cap including Europe, centred at 50°N, 14°E with the half-angle of 20° has been considered. The model is based on the expansion of Fourier longitudinal series and Legendre colatitudinal functions as the orthogonal basis functions over the caplike region of interest. It has been found that for the modelling of the f 0 F 2, a SCH model with only 9 coefficients (K up to 2) well portrays its basic features.