This paper presents and discusses electron density depletion regions observed with the incoherent scatter EISCAT Svalbard Radar (ESR) located at 75.43°N geomagnetic latitude. The data include several decades of measurements, which make them suitable for studying statistical features and characteristics of the ionospheric parameters. Here we focus on the electron density depletions and their dependence on diurnal and seasonal variations and solar activity. An electron density depletion region is identified in the ESR data in the early morning sector. This depletion region seems to be clearest during equinox and winter and moderate/high solar activity. An enhancement in the ion temperature is often co‐located with the electron density depletion region. The ion temperature enhancement could indicate that ion frictional heating is related to the electron density depletion region. However, during summer when the solar activity is low, the electron density depletion is not observed although the ion temperature is enhanced, suggesting that formation of the electron density depletion regions due to ion frictional heating may depend on the background effective temperature and O/N₂ ratio. In addition, seasonal changes in the solar zenith angle could also contribute to the formation of the depletion region.

中文翻译：

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在极帽电离层中观察到的电子密度耗尽区

本文介绍并讨论了位于地磁纬度为75.43°N的非相干散射EISCAT斯瓦尔巴德雷达（ESR）所观测到的电子密度耗尽区。数据包括数十年的测量结果，使其适合研究电离层参数的统计特征和特性。在这里，我们关注电子密度的消耗及其对昼夜和季节变化以及太阳活动的依赖性。在早期的ESR数据中确定了一个电子密度耗尽区。在春分和冬季以及中度/高度太阳活动期间，这种耗尽区域似乎最为清晰。离子温度的升高通常与电子密度耗尽区共存。离子温度升高可能表明离子摩擦加热与电子密度耗尽区有关。然而，在夏季，当太阳活动低时，尽管离子温度升高，但未观察到电子密度耗尽，这表明由于离子摩擦加热而形成的电子密度耗尽区可能取决于背景有效温度和O / N₂比率。此外，太阳天顶角的季节性变化也可能有助于耗尽区的形成。