Both ground‐ and satellite‐based airglow imaging have significantly contributed to understanding the low‐latitude ionosphere, especially the morphology and dynamics of the equatorial ionization anomaly (EIA). The NASA Global‐scale Observations of the Limb and Disk (GOLD) mission focuses on far‐ultraviolet airglow images from a geostationary orbit at 47.5°W. This region is of particular interest at low magnetic latitudes because of the high magnetic declination (i.e., about ‐20°) and proximity of the South Atlantic magnetic anomaly. In this study, we characterize an exciting feature of the nighttime EIA using GOLD observations from October 5, 2018 to June 30, 2020. It consists of a wavelike structure of a few thousand kilometers seen as poleward and equatorward displacements of the EIA‐crests. Initial analyses show that the synoptic‐scale structure is symmetric about the dip equator and appears nearly stationary with time over the night. In quasi‐dipole coordinates, maxima poleward displacements of the EIA‐crests are seen at about ± 12° latitude and around 20 and 60° longitude (i.e., in geographic longitude at the dip equator, about 53°W and 14°W). The wavelike structure presents typical zonal wavelengths of about 6.7 × 10³ km and 3.3 × 10³ km. The structure's occurrence and wavelength are highly variable on a day‐to‐day basis with no apparent dependence on geomagnetic activity. In addition, a cluster or quasi‐periodic wave train of equatorial plasma depletions (EPDs) is often detected within the synoptic‐scale structure. We further outline the difference in observing these EPDs from FUV images and in situ measurements during a GOLD and Swarm mission conjunction.

中文翻译：

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夜间赤道电离异常的天气尺度波状结构

基于地面和基于卫星的气辉成像都对理解低纬度电离层，尤其是赤道电离异常（EIA）的形态和动力学做出了重要贡献。美国国家航空航天局（NASA）对肢体和磁盘的全球观测（GOLD）专注于从地球静止轨道47.5°W处产生的远紫外线气辉影像。由于高磁偏角（即大约-20°）和南大西洋磁异常的临近，该区域在低纬度地区特别受关注。在这项研究中，我们使用2018年10月5日至2020年6月30日的GOLD观测来表征夜间EIA的一个激动人心的特征。它由数千公里的波浪状结构组成，被视为EIA波峰的极点和赤道位移。初步分析表明，天气尺度结构关于俯仰赤道是对称的，并且在夜间随着时间的推移几乎是静止的。在准偶极坐标系中，在约±12°的纬度和约20和60°的经度（即，在赤道赤道处的地理经度，约53°W和14°W）可以看到EIA顶的最大极向位移。波形结构呈现典型的约6.7×10的纬向波长³ 公里和3.3×10 ³ 公里。该结构的出现和波长每天变化很大，而对地磁活动没有明显的依赖性。另外，在天气尺度结构中经常会检测到赤道等离子体损耗（EPD）的簇或准周期波列。我们进一步概述了在GOLD和Swarm任务结合期间从FUV图像观察这些EPD和现场测量的差异。