Abstract:
Based on the amplitude scintillation index
S4 observed from Constellation Observing System for Meteorology, Ionosphere and Climate (COSMIC) radio occultation technique, the radio occultation point is taken as the position of the ionospheric irregularities resulting in the ionospheric scintillation phenomena. In this paper, the temporal and special variations, as well as its dependence on solar activities and geomagnetic activities of the ionospheric E-region irregularities and F-region irregularities are analyzed. It is found that the E region irregularities mainly occur in the mid-latitude of the summer hemisphere, the F region irregularities mainly occur in the equatorial and low latitudes during spring and autumn, which are strongly controlled by the geomagnetic field. In addition to the seasonal influence, the dependence of E region irregularities on the solar activity is not fundamental, while the solar activity has a distinct impact on the F-region irregularities in the equatorial ionization anomaly and equatorial region. In comparison with those during the low solar activity years, the intensity and latitudinal range of F region irregularities are much greater and wider during the high solar activity years. In general, the morphology of E-region irregularities during the geomagnetic active periods is similar to that during the geomagnetic quiet period. However, the intensity of E region scintillation increases slightly, especially during 00:00−06:00LT. Meanwhile, the morphology of F-region irregularities during the geomagnetic active periods is also similar to that during the geomagnetic quiet period. The intensity of F region scintillation increases notably and the latitudinal range extends to be wider, especially during 00:00−06:00LT and 18:00−24:00LT in the Pacific sector . In comparison with the scintillation occurrence results from space-based in-situ observations, it is found that GNSS occultation technique can not only reflect the detailed characteristics of ionospheric irregularities on a global scale, such as seasonal/longitudinal variations, and its dependence on local time, solar activities and geomagnetic latitudes, but also reflect the variation of ionospheric irregularities with altitude, which is unprecedented for the previous observational techniques.