Chartier A T, Datta-Barua S, McDonald S E, Bust G S, Tate J, Goncharenko L P, Romeo G, Schaefer R K
Johns Hopkins Applied Physics Laboratory Laurel MD USA.
Illinois Institute of Technology Chicago IL USA.
J Geophys Res Space Phys. 2021 Sep;126(9):e2021JA029324. doi: 10.1029/2021JA029324. Epub 2021 Sep 13.
The Ionospheric Data Assimilation Four-Dimensional (IDA4D) technique has been coupled to Sami3, which is another model of the ionosphere (SAMI3). In this application, ground-based and space-based GPS total electron content (TEC) data have been assimilated into SAMI3, while in-situ electron densities, autoscaled ionosonde NmF2, and reference GPS stations have been used for validation. IDA4D/SAMI3 shows that night-time ionospheric localized enhancements (NILE) are formed following geomagnetic storms in November 2003 and August 2018. The NILE phenomenon appears as a moderate, longitudinally extended enhancement of NmF2 at 30°-40°N MLAT, occurring in the late evening (20-24 LT) following much larger enhancements of the equatorial anomaly crests in the main phase of the storms. The NILE appears to be caused by upward and northward plasma transport around the dusk terminator, which is consistent with eastward polarization electric fields. Independent validation confirms the presence of the NILE, and indicates that IDA4D is effective in correcting random errors and systematic biases in SAMI3. In all cases, biases and root-mean-square errors are reduced by the data assimilation, typically by a factor of 2 or more. During the most severe part of the November 2003 storm, the uncorrected ionospheric error on a GPS 3D position at 1LSU (Louisiana) is estimated to exceed 34 m. The IDA4D/SAMI3 specification is effective in correcting this down to 10 m.
电离层数据同化四维（IDA4D）技术已与另一个电离层模型Sami3（SAMI3）耦合。在该应用中，地基和天基全球定位系统总电子含量（TEC）数据已被同化到SAMI3中，同时原位电子密度、自动缩放电离层测高仪的NmF2以及参考GPS站已被用于验证。IDA4D/SAMI3显示，2003年11月和2018年8月的地磁暴之后形成了夜间电离层局部增强（NILE）。NILE现象表现为在磁纬30°-40°N处NmF2的适度、纵向扩展增强，发生在傍晚后期（当地时间20-24时），此前在风暴主相期间赤道异常峰值有更大增强。NILE似乎是由黄昏终止线周围的等离子体向上和向北传输引起的，这与向东极化电场一致。独立验证证实了NILE的存在，并表明IDA4D在纠正SAMI3中的随机误差和系统偏差方面是有效的。在所有情况下，通过数据同化，偏差和均方根误差都有所降低，通常降低了2倍或更多。在2003年11月风暴最严重的部分期间，估计在路易斯安那州1LSU处GPS三维位置上未校正的电离层误差超过34米。IDA4D/SAMI3规范有效地将此误差校正至10米。
