Equatorial Plasma Bubble Threat Parameterization to Support GBAS Operations in the Brazilian Region

Abstract

The Brazil ionospheric study project aims to develop a new ground-based augmentation system (GBAS) ionospheric threat model to better reflect Brazil's low-latitude conditions. Data processing from the global navigation satellite system for 123 active ionospheric days identified 1017 anomalous ionospheric gradients caused by nighttime equatorial plasma bubbles (EPBs). A significant number of gradients, including the largest verified gradient of 850.7mm/km, exceed the upper bound (375-425mm/km) of the conterminous United States (CONUS) threat model. This paper defines a series of parameters to model the geometry of EPBs. A maximum ionospheric delay drop of 35m and a transition zone between 20 and 450km are estimated for EPBs that move roughly eastward and parallel to the geomagnetic equator with speeds between 40 and 250m/s. These parameters are key to the development of a GBAS ionospheric mitigation and safety case for operational approval in Brazil and other low-latitude locations. Copyright (C) 2017 Institute of Navigation