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

In this study the climatology of ionospheric scintillations and the zonal drift velocities of scintillation-producing irregularities are depicted for a station located under the southern crest of the equatorial ionization anomaly. Then, the α − μ ionospheric fading model is used for the first- and second-order statistical characterization of amplitude scintillations. In the statistical analyzes, data are used from single-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 occurrence of scintillations follows the seasonal distribution of plasma bubble irregularities observed in the longitudinal sector of eastern South America. In addition to the solar cycle dependence, the results suggest that the occurrence climatology of scintillations is also modulated by the secular variation in the dip latitude of Cachoeira Paulista, since the maximum occurrence of scintillations during the peak of solar cycle 24 was ∼ 20 % lower than that observed during the maximum of solar cycle 23. The dynamics of the irregularities throughout a solar cycle, as investigated from the estimates of the mean zonal drift velocities, presented a good correlation with the EUV and F10.7 cm solar fluxes. Meanwhile, the seasonal behavior showed that the magnitude of the zonal drift velocities is larger during the December solstice months than during the equinoxes. In terms of modeling, the results for the α − μ distribution fit quite well with the experimental data and with the temporal characteristics of fading events independently of the solar activity level.Published1201–12182A. Fisica dell'alta atmosferaJCR Journa

3D Ionospheric Imaging for Space Weather Monitoring at Low-Latitudes

Three-dimensional (3D) ionospheric imaging at Low-Latitudes is challenging due to the high ionospheric variability and dynamics in the region. The region is characterized by the presence of the Equatorial Ionization Anomaly (EIA), plasma bubbles, layered structures, and strong vertical drifts upwards during the evening pre-reversal enhancement. Aiming to better understand the ionosphere at low latitudes, this study shows the latest developments conducted by the authors to map the region with 3D inversion algorithms based on Global Navigation Satellite Systems (GNSS), ionosondes, GNSS radio-occultation, and empirical models, such as the International Reference Ionosphere (IRI). We address the capabilities of the developed 3D imaging methods to disclose the main morphologies and dynamics of the ionospheric electron density in the region. Limitations are also discussed since data assimilation schemes are still ill-conditioned for a complete 3D reconstruction. Based on the experiments conducted by the authors, the main conclusions have outlined that better 3D representation of the ionosphere in the region of particular interest requires three main improvements: 1) denser GNSS networks on ground and space; 2) better representation by empirical models to be used as background to the inversion technique, mainly to better represent the plasmasphere, topside ionosphere, and during the pre-reversal enhancements; and 3) dedicated signals for navigation transmitted by Low Earth Orbit (LEO) satellites