Recommendation ITU-R P.531 describes a method for evaluating of the ionospheric propagation effects on Earth-space paths at frequencies from 0.1 to 12 GHz. The following effects may take place on an Earth-space path when the signal is passing through the ionosphere: ?C rotation of the polarization (Faraday rotation) due to the interaction of the electromagnetic wave with the ionized medium in the Earth's magnetic field along the path; ?C group delay and phase advance of the signal due to the total electron content (TEC) accumulated along the path; ?C rapid variation of amplitude and phase (scintillations) of the signal due to small-scale irregular structures in the ionosphere; ?C a change in the apparent direction of arrival due to refraction; ?C Doppler effects due to non-linear polarization rotations and time delays. The data and methods described in this Recommendation are applicable for planning satellite systems@ in respective ranges of validity indicated in Annex 1.