The precise 3-D ionospheric electron density (IED) modeling is in general difficult due to costly and insufficient observations in the ionosphere. The Constellation Observing System for Meteorology, Ionosphere, and Climate (COSMIC) mission has provided a significant opportunity for estimating the IED profile during the past 15 years. In this article, a precise empirical 3-D global electron density model (GEDM) from COSMIC GNSS radio occultation (RO) data is developed based on Fourier expansion and principal component analysis (PCA) and evaluated with independent datasets. Each profile is described by five essential parameters: the mean scale height Hm, bottom and topside slopes of the scale height (a1 and a2), peak density of the F2 layer (NmF2), and height of the F2 layer peak density (hmF2). The GEDM model can provide IED at any local time (LT) (0–24 h), F10.7 (70–150 sfu), Kp (0–9), latitude (90°S–90°N), longitude (180°W–180°E), and altitude, especially in the F region. The model is validated by the incoherent scatter radar (ISR), International Reference Ionosphere (IRI)-2020, K-Band Ranging system (KBR) of the Gravity Recovery and Climate Experiment (GRACE), and the Global Ionospheric Map (GIM) TEC in 2010 and 2014. The results show that the GEDM model has preferable reliability and consistency with respect to the independent observations and the IRI-2020 model. The statistical error of the GEDM model is lower than that of the IRI-2020, particularly in the mid-latitude region. Furthermore, the GEDM model is capable of precisely capturing typical ionospheric features, such as the equatorial ionization anomaly (EIA), winter anomaly, and the annual anomaly.

中文翻译：

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基于 GNSS 无线电掩星数据的多参数全局电子密度模型 (GEDM)


由于电离层观测成本高昂且观测不足，精确的 3-D 电离层电子密度 (IED) 建模通常很困难。过去 15 年里，气象、电离层和气候星座观测系统 (COSMIC) 任务为估算 IED 剖面提供了重要机会。在本文中，基于傅里叶展开和主成分分析 (PCA)，开发了基于 COSMIC GNSS 无线电掩星 (RO) 数据的精确经验 3-D 全球电子密度模型 (GEDM)，并使用独立数据集进行了评估。每个剖面由五个基本参数描述：平均鳞片高度 Hm、鳞片高度的底部和顶部斜率（a1 和 a2）、F2 层的峰值密度 (NmF2) 以及 F2 层峰值密度的高度 (hmF2) 。 GEDM模型可以提供任意本地时间（LT）（0-24小时）、F10.7（70-150 sfu）、Kp（0-9）、纬度（90°S-90°N）、经度（ 180°W–180°E) 和海拔高度，特别是在 F 区域。该模型经过非相干散射雷达 (ISR)、国际参考电离层 (IRI)-2020、重力恢复和气候实验 (GRACE) 的 K 波段测距系统 (KBR) 以及全球电离层图 (GIM) TEC 的验证2010年和2014年的结果表明，GEDM模型相对于独立观测和IRI-2020模型具有较好的可靠性和一致性。 GEDM模型的统计误差低于IRI-2020，特别是在中纬度地区。此外，GEDM模型能够精确捕捉典型的电离层特征，例如赤道电离异常（EIA）、冬季异常和年度异常。