Climatology and modeling of ionospheric scintillations and irregularity zonal drifts at the equatorial anomaly crest region

摘要

In this study the climatology of ionospheric scintillations and the zonal driftvelocities of scintillation-producing irregularities are depicted for astation located under the southern crest of the equatorial ionizationanomaly. Then, the  −  ionospheric fading model is used for thefirst- and second-order statistical characterization of amplitudescintillations. In the statistical analyzes, data are used fromsingle-frequency GPS receivers acquired during ∼ 17 years(September 1997–November 2014) at Cachoeira Paulista (22.4° S;45.0° W), Brazil. The results reveal that the nocturnal occurrenceof scintillations follows the seasonal distribution of plasma bubbleirregularities observed in the longitudinal sector of eastern South America.In addition to the solar cycle dependence, the results suggest that theoccurrence climatology of scintillations is also modulated by the secularvariation in the dip latitude of Cachoeira Paulista, since the maximumoccurrence of scintillations during the peak of solar cycle 24 was∼ 20 % lower than that observed during the maximum of solar cycle23. The dynamics of the irregularities throughout a solar cycle, asinvestigated from the estimates of the mean zonal drift velocities, presenteda good correlation with the EUV and F10.7 cm solar fluxes. Meanwhile, theseasonal behavior showed that the magnitude of the zonal drift velocities islarger during the December solstice months than during the equinoxes. Interms of modeling, the resultsfor the  −  distribution fit quite well with the experimental dataand with the temporal characteristics of fading events independently of the solar activitylevel.