CHARACTERISTICS OF SMALL-SCALE IONOSPHERIC IRREGULARITIES AS DEDUCED FROM SCINTILLATION OBSERVATIONS OF RADIO SIGNALS FROM SATELLITES ETS-2 AND POLAR-BEAR-4 AT IRKUTSK

This paper presents some new results on the small-scale inhomogeneous ionospheric structure obtained at a facility for spaced-antenna reception of transionospheric signals from ETS-2 and Polar Bear 4 near Irkutsk (Eastern Siberia, 52-degrees-N, 104-degrees-E). A technique based on transferring time spectra of scintillations to spatial spectra using measured horizontal irregularity drift velocities is used to obtain an estimate of the mean spatial spectrum of midlatitude scintillations. Two different methods were used to determine the inclination index of the scintillation spectrum, which was found to be equal to -2, in agreement with the value recently predicted for small-scale F region irregularities generated through mapping of small-scale, turbulent electric fields from the E region to the F region. Drift velocities of the diffraction pattern, and also the altitudes at which ionospheric irregularities are located, agree well with results obtained by other authors for midlatitudes. Using simultaneous measurements for a geostationary satellite and an orbiting satellite, the supposition about the existence of the southern boundary of the scintillation region has been confirmed. Finally, analysis of quasi-periodic (QP) scintillations and simultaneously determined diffraction pattern velocities is used to show that the height of isolated irregularities giving rise to QP scintillations corresponds to the maximum of the ionospheric F2 region.