The ground-based augmentation system must make provisions to being sufficiently robustness to ionospheric anomalies through the development of an ionospheric anomaly threat model. For developing the threat model in Brazil, earlier work found that ionospheric spatial decorrelations larger than those in the midlatitude regions were frequently observed during the peak of Solar Cycle #24 (current cycle). We provide details of a study of the extreme ionospheric spatial decorrelation observed over Brazil during the March 1, 2014, equatorial plasma bubble (EPB) event. As viewed by two Brazilian GNSS reference stations in São José dos Campos, PRN 03 descended to an elevation angle of about 19° in the northern sky. A spatial decorrelation of 850.7 mm/km at the GPS L1 signal at 01:04:00 UT between the two stations SJCU (23.21° S, 45.96° W) and SSJC (23.20° S, 45.86° W) over a baseline of 9.72 km was discovered, when the line of sight of PRN 03 passed through the transition zone of the EPB. Since the EPB-induced ionospheric scintillation can corrupt the ionospheric gradient estimates, multiple gradient observations were made from multiple stations and satellites to verify the largest gradient observation. Severe gradients discovered at other station–satellite pairs support that the event of PRN 03 is a real anomaly as opposed to a receiver fault or the result of post-processing errors. Since the availability loss was estimated to be 41.7% with the Brazilian threat model, remedies to reduce over-estimated ionospheric impact when evaluating and mitigating ionospheric integrity risk are presented.

中文翻译：

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在2014年3月1日赤道等离子气泡事件中观测到的极端电离层空间去相关

地面增强系统必须通过开发电离层异常威胁模型，为电离层异常提供足够的鲁棒性。为了开发巴西的威胁模型，早期的工作发现，在第24号太阳周期（当前周期）的峰值期间，经常观察到电离层空间相关性大于中纬度地区。我们提供了2014年3月1日赤道等离子体气泡（EPB）事件期间在巴西观测到的极端电离层空间去相关的研究细节。正如巴西圣何塞杜斯坎普斯的两个巴西GNSS参考站所看到的那样，PRN 03在北部天空中下降到大约19°的仰角。GPS L处的空间去相关为850.7 mm / km在PRN的视线范围内发现两个站SJCU（23.21°S，45.96°W）和SSJC（23.20°S，45.86°W）在UT的01:04:00 UT上有一个信号在9.72 km的基线上03穿过EPB的过渡区。由于EPB引起的电离层闪烁会破坏电离层梯度估计，因此从多个台站和卫星进行了多次梯度观测，以验证最大的梯度观测。在其他卫星站对上发现的严重梯度表明，与接收机故障或后处理错误的结果相反，PRN 03事件是真正的异常。由于在巴西威胁模型中，可用性损失估计为41.7％，因此提出了在评估和减轻电离层完整性风险时减少过高估计的电离层影响的补救措施。