ESA’s Swarm constellation mission makes it possible for the first time to determine field-aligned currents (FACs) in the ionosphere uniquely. In particular at high latitudes, the dual-satellite approach can reliably detect some FAC structures which are missed by the traditional single-satellite technique. These FAC events occur preferentially poleward of the auroral oval and during times of northward interplanetary magnetic field (IMF) orientation. Most events appear on the nightside. They are not related to the typical FAC structures poleward of the cusp, commonly termed NBZ. Simultaneously observed precipitating particle spectrograms and auroral images from Defense Meteorological Satellite Program (DMSP) satellites are consistent with the detected FACs and indicate that they occur on closed field lines mostly adjacent to the auroral oval. We suggest that the FACs are associated with Sun-aligned filamentary auroral arcs. Here we introduce in an initial study features of the high-latitude FAC structures which have been observed during the early phase of the Swarm mission. A more systematic survey over longer times is required to fully characterize the so far undetected field aligned currents.

中文翻译：

---

用 Swarm 星座导出的北行星际磁场期间极冠区域的丝状场对齐电流

ESA 的 Swarm 星座任务首次使唯一地确定电离层中的场对齐电流 (FAC) 成为可能。特别是在高纬度地区，双卫星方法可以可靠地检测到传统单卫星技术遗漏的一些 FAC 结构。这些 FAC 事件优先发生在极光椭圆的两极和北行行星际磁场 (IMF) 方向期间。大多数事件发生在夜边。它们与尖端的典型 FAC 结构（通常称为 NBZ）无关。同时观察到的来自国防气象卫星计划 (DMSP) 卫星的降水粒子谱图和极光图像与检测到的 FAC 一致，表明它们出现在主要与极光椭圆相邻的闭合场线上。我们认为 FAC 与与太阳对齐的丝状极光弧有关。在这里，我们介绍了在 Swarm 任务的早期阶段观察到的高纬度 FAC 结构的初步研究特征。需要在更长时间内进行更系统的调查，以完全表征迄今为止未检测到的场对齐电流。