Rate of phase change and fade depth on GPS paths due to ionospheric scintillation

GPS (or other satellite navigation system) receivers can lose phase lock if the received signal shows too fast a rate of phase change and/or too great a fade depth, particularly when the received SNR is low. Such phase changes and fades can occur due to ionospheric scintillations and it is known can result in phase lock loss particularly when scintillations are large, the worst effects being during solar maximum years. In this paper we estimate phase and amplitude variations introduced by time fluctuating electron density irregularities responsible for the scintillations and assess their effect on GPS receivers. In order to make these calculations, we use a further extension of the propagation model for satellite transionospheric links developed in Gherm et al. (2000). The extended model permits the calculation of some detailed effects of propagation for transionospheric radio links including the rate of change of phase when scintillations occur and the generation of time sequences for the field amplitude (log-amplitude) and phase fluctuations of the received GPS signal, including also the case of strong amplitude fluctuations (Gherm et al. 2002). These calculations can be performed for any 3D models of the background ionosphere and an anisotropic inverse power law spatial spectrum of fluctuations of the electron density of the ionosphere.