A novel approach for estimating scintillation threat levels: Description and example results using GOLD observations and ground-based scintillation monitors

Amplitude scintillation is very often experienced by Global Navigation Satellite System (GNSS) signals propagating through the low-latitude ionosphere during nighttime. These scintillation events are associated with the occurrence of Equatorial Plasma Bubbles. Previous studies have already shown that scintillation severity is enhanced around the region of the Equatorial Ionization Anomaly peaks, being intrinsically related to the ionospheric F-region background density. Here, a novel approach is proposed where the maximum scintillation severity that can threat a trans-ionospheric L-band signal, referred in this work as to the scintillation threat level [S4(max)], is estimated from background F-region peak electron density (NmF2) observations. The main novelty of the approach is that it employs collocated observations from space-based and spatially distributed ground-based instruments that are now available to quantify the relationship between the background F-region peak electron density (NmF2) and the scintillation threat level reached at a given night over distinct dip latitudes. To test this approach and its feasibility, NmF2 observations provided by the Global-scale Observations of the Limb and Disk (GOLD) instrument and L-band scintillation measurements, made by a network of GNSS-based scintillation monitors, were used. Results show that the scintillation threat level is indeed heavily controlled by the background F-region peak electron density. The results quantify the control of the latitudinal distribution of S4(max) values by the latitudinal variation of the F-region peak electron density. More importantly, we show that an empirical relationship between NmF2 and S4(max), for the local time interval covered by GOLD, can be derived. Additionally, it is demonstrated that the relationship can be employed to create regional (Brazilian region) maps of potential scintillation threat level using GOLD-like data. The estimated scintillation threat levels using the proposed approach show excellent agreement with measurements. Our results also suggest that the approach proposed can be well-suited to estimate S4(max) from independent observations at distinct longitudes, provided that solar flux and seasonal trends are similar to those used to obtain the relationship between NmF2 and S4(max).