The COSMIC radio occultation observations are used to investigate the wavenumber-4 (WN4) structure of the Sporadic E (Es) layer during 2007–2018. The WN4 pattern is observed in the Es occurrence rate over the middle- and low-latitudes. This pattern is stronger at the low-latitudes than at the middle-latitudes. It shows the peak intensity in latitude bands between 5° and 15° dip latitudes in both hemispheres. The WN4 structure occurs predominantly during daytime. It appears above 110 km in the morning, then descends slowly down to about 105 km, and finally disappears after sunset. The WN4 structure moves eastward with a speed of approximately 90°/day. It is prominent in boreal autumn and summer, and disappears in boreal winter. The dominant role of the DE3 tide for the formation of the WN4 structure is supported by similar features between the Es occurrence rate and the DE3 tide of the zonal wind shear, such as the phase, eastward speed, seasonal variation, symmetrical distribution, and strong activity at the low-latitudes.

中文翻译：

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中低纬度零星E的4号波模式

COSMIC 无线电掩星观测用于研究 2007-2018 年间零星 E (Es) 层的波数 4 (WN4) 结构。在中低纬度地区的 Es 发生率中观察到 WN4 模式。这种模式在低纬度地区比在中纬度地区更强。它显示了两个半球在 5° 和 15° 倾角纬度之间的纬度带中的峰值强度。WN4 结构主要发生在白天。早上出现在110公里以上，然后缓慢下降到105公里左右，日落后消失。WN4结构以大约90°/天的速度向东移动。在寒带秋夏季突出，在寒带冬季消失。