To understand the features of the quasistatic field-aligned currents (FACs) consisting of multiple mesoscale (∼10–100 km) upward and downward FAC regions in the duskside auroral oval, we examined the magnetic field data obtained through the constellation measurements of Swarm satellites for a duration of more than three years. We introduced a method of automated event identification and took the events in 577 satellite orbits that pass through the high-latitude part of the 14–18 magnetic local time auroral oval. The results of the analysis reveal that the occurrence ratio of the FAC events increases with the IMF B_Z, and that the event can be detected at a ratio exceeding 20% for B_Z greater than 1 nT. This indicates that the quasistatic mesoscale FACs in the duskside sector are pertinent to a northward IMF condition and that they are not a simple remnant of the diminished Region 1. The results also show that the FAC density tends to increase with the solar wind proton density, implying that the latter is directly associated with FAC generation. The FAC events can occur in a wide range of solar zenith angles, that is, 65–135°, indicating that whether the ionosphere is sunlit or dark is not crucial for the appearance of the event. These results strongly suggest that multiple mesoscale FACs are produced in the low-latitude boundary layer through a mechanism related to solar wind plasma entry processes that can be more easily attained as the northward component of the IMF increases.

中文翻译：

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北向 IMF 对黄昏扇区衰减区 1/2 洋流系统中嵌入的准静态中尺度场对齐洋流的重要性

为了了解由黄昏极光椭圆中的多个中尺度（~10-100 km）向上和向下 FAC 区域组成的准静态场对齐电流 (FAC) 的特征，我们检查了通过 Swarm 卫星星座测量获得的磁场数据持续时间超过三年。我们引入了一种自动事件识别方法，并在通过 14-18 磁当地时间极光椭圆的高纬度部分的 577 个卫星轨道上采集了事件。分析的结果表明，与IMF的FAC事件的增加的发生比率乙_Ž，并且该事件可以以比超过20％检测到的乙_ž大于 1 nT。这表明黄昏扇区中的准静态中尺度 FAC 与向北的 IMF 条件有关，并且它们不是减弱的区域 1 的简单残余。结果还表明，FAC 密度倾向于随着太阳风质子密度的增加而增加，暗示后者与 FAC 生成直接相关。FAC事件可以发生在很宽的太阳天顶角范围内，即65-135°，表明电离层是阳光照射还是黑暗对事件的出现并不重要。这些结果强烈表明，通过与太阳风等离子体进入过程相关的机制，在低纬度边界层中产生了多个中尺度 FAC，随着 IMF 向北分量的增加，这种机制更容易实现。