Ionospheric effects on aviation applications in South America

With increasing worldwide interests in using GNSS satellite augmentation systems for aviation applications, it is important to define and understand the challenges posed by the ionosphere in areas where these applications are most vulnerable. These regions, of course, are the low-latitude regions where problematic features including strong latitudinal gradients and post-sunset plasma depletions and scintillation are a common occurrence, particularly at high levels of solar activity. Depletions occur quite frequently in the nighttime ionospheric F-region and they often stretch for hundreds of kilometers in the north-south direction. Depletions are a significant limiting factor for satellite-based navigation systems as radio signals propagating through these depletions suffer large range delays and may result in poor positioning accuracies. Scintillation is associated with depletion activity and it affects the performance of GNSS navigation and communication systems by inducing losses of lock and cycles slips. These effects limit the performance and availability of GNSS satellites for positioning and for precise safety-of-life applications such as GNSS based satellite augmentation systems used for aviation. This paper will describe Satellite Based Augmentation Systems (SBAS) and Ground-Based Augmentation Systems (GBAS) and illustrate how the ionosphere affects their performance. This will include how often, and where and when, availability and accuracy of SBAS and GBAS systems can be challenged due to plasma bubbles and/or large electric fields that induce bigger gradients into the equatorial anomaly regions. Finally, our work will estimate the potential improvements in aviation system performance at low latitudes with the arrival of new GNSS system and signals in the next decade.