This research presents a study on ionospheric effects on a Ground Based Augmentation System (GBAS) in equatorial and low latitude regions. The ionosphere affects the propagation of GPS signals and can reduce the positioning accuracy in the equatorial and low-latitude regions. Auxiliary systems have been developed to meet the safety requirements of aviation. In this context, GBAS provide higher accuracy for differential corrections. To evaluate the performance of a GBAS, a simulation model of the GPS L1 signal-in-space has been developed, considering ionospheric delay based on statistical distributions of vertical Total Electron Content residuals obtained from IRI model and Rede Brasileira de Monitoramento Contínuo estimates, in combination with amplitude ionospheric scintillation simulated based on (Alfa) - (Mi) probability distributions, as well as phase scintillation, generated according to empirical relationships between the indices (S)4 and (Sigma)(Fi). The GPS L1 signal model also considers clock and random errors, tropospheric delays, ambiguity, and multipath, for a complete description. The signal in space results are injected into a GBAS ground facility simulation model, implemented to detect a varied array of possible anomalies or failures in the signal in space and to generate differential corrections based on monitoring algorithms. The GBAS generates corrections and its performance is evaluated for aircraft approaches under different ionospheric conditions at the Rio de Janeiro and Fortaleza Airports, emphasizing Approach Category I. The horizontal and vertical errors are estimated using GBAS corrections to evaluate the accuracy. The GBAS integrity is also analyzed by computing the horizontal and vertical protection levels.