On the relationship between the geometrical control of scintillation indices and the data detrending problems observed at high latitudes

The experimental estimate of radio waves scintillation, caused by plasma density irregularities in the ionosphere,
is usually attempted by means of scintillation indices which are essentially standard deviations of stochasticly
fluctuating parts of the received radio wave intensity and phase. At high latitudes, provided that the propagation
problem may be modelled by means of the weak scattering theory, the typical scintillation indices S4 and σφ depend
on a geometrical factor which introduces some amplifications on their values. Scintillation indices S4 and
σφ measured at auroral latitudes are estimated by means of different boundary detrending conditions and the geometrical
effect on those detrending conditions is investigated. In the case of the polar Low Earth Orbiting (LEO)
satellite links considered here, high phase with low intensity scintillation events do not seem to be related to geometrical
effects only, but rather to misleading data detrending.