Regional ionospheric delay mapping for low-latitude environments

The ionosphere in low-latitude regions has strong dynamics reflected by unique phenomena such as the equatorial ionization anomaly and equatorial plasma bubbles. Since the ionosphere can significantly affect space-to-Earth technologies, notably communication systems and Global Navigation Satellite Systems (GNSS), the variations in ionospheric total electron content are of great interest to the space weather community and operators of these technologies. Motived by these issues, this paper proposes a new methodology to generate ionospheric delay maps using data from a network of GNSS monitoring stations. The methodology developed is suitable for low latitudes and has low level of complexity. It is based on the thin shell model of the ionosphere and uses groupings of measurements in time and space, triangulation, linear interpolation, and smoothing. The resulting maps show detailed coverage of large-scale phenomena, like structures of equatorial plasma bubbles, in a way that other geophysical instruments are not able to provide. In a qualitative validation using a network of stations in Brazil, it was demonstrated that the maps were able to clearly identify plasma bubble structures also captured by other instruments, like scintillation monitors and all-sky imager. The quantitative assessment showed errors less than 4 m in 99.9% of the times in days with high variability of the ionosphere and less than 1 m in a day with very low ionization. The quality of the generated maps with this new methodology using this density of data opens a wide range of possibilities for scientific and operational applications in low-latitude ionosphere environment.