Evaluating Amplitude Scintillation Severity in the Early Night Hours Using Fading Coefficients

Several studies have investigated the characteristics of amplitude scintillation in low-latitude regions, particularly focusing on the impact of fading events on satellite-dependent systems for navigation and positioning. It is well-established that the severity of amplitude scintillation in transionospheric signals is more pronounced around the Equatorial Ionization Anomaly, influenced by the signal propagation path and background ionospheric density. However, the temporal behavior of amplitude scintillation and fading events across different latitudes remains an ongoing research topic. This study explores the temporal characteristics of scintillation using data from four ground-based scintillation monitor stations located at various dip latitudes in the southern hemisphere, specifically in Brazil. The observation period covers five months during the peak of the previous solar cycle, with data collected from 19:00 LT to 23:59 LT at each station. The study aims to statistically assess the distribution of severe fade events using fading coefficients modeled by an ?-? distribution, which captures the non-linear effects of ionospheric propagation. Our findings indicate that scintillation severity peaks at 21:00 LT at all stations, with greater intensities near the Equatorial Ionization Anomaly and weaker intensities closer to the dip equator. Notably, severe fading coefficients are predominantly observed during the early night hours. The most severe fade statistics occur around 21:00 LT, significantly decreasing thereafter. Additionally, the occurrence probability of deep fading declines after its peak at 21:00 LT. These insights provide a valuable statistical characterization for GNSS (Global Navigation Satellite System) link simulations, especially during the early night hours when the risk of issues such as cycle slips and loss-of-lock is at its highest.