Strong zonal flows greater than 1,000 m/s have recently been identified by Swarm in the midnight sector of the winter hemisphere auroral zone. These flows are typically observed between upward and downward field aligned current pairs and therefore are referred to as Birkeland current boundary flows (BCBFs). The Swarm observations also identify ion heating and upflows associated with the fast zonal flows. BCBFs and the resulting ion heating and upflows play an important role in thermosphere‐ionosphere‐magnetosphere coupling given their high occurrence rate in the quiet time nightside auroral zone. This paper utilizes Super Dual Auroral Radar Network (SuperDARN) high‐resolution fits to line‐of‐sight data to investigate two known BCBF events. The large (>2,000 m/s) BCBFs observed with Swarm A and B are found to be collocated with the location of field line resonances (FLRs) with periods of approximately 20–30 min. The SuperDARN high‐resolution fits determine FLR peak flow velocities of 400–700 m/s. When the FLR velocities are superimposed upon the background ionospheric convection of 400–600 m/s, this yields total east‐west velocities of 800–1,300 m/s near the time and location of the BCBF events. The peak flows of the field line resonances are shown to be bounded by pairs of upward and downward field aligned current similar to the BCBFs. The observations suggest a causal relationship between BCBFs and FLRs.

中文翻译：

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与场线共振相关的Birkeland当前边界流

Swarm最近在冬季半球极光区的午夜区域发现了大于1000 m / s的强纬向气流。通常在向上和向下磁场对准的电流对之间观察到这些流，因此将其称为Birkeland电流边界流（BCBF）。Swarm观测还确定了与快速纬向流相关的离子加热和上流。BCBF及其导致的离子加热和上流在热层-电离层-磁层的耦合中起着重要作用，因为它们在安静的夜晚夜晚极光区中的发生率很高。本文利用超双极光雷达网络（SuperDARN）的高分辨率拟合到视线数据来研究两个已知的BCBF事件。大（> 2，000 m / s）用群A和B观测到的BCBF被发现与场线共振（FLR）的位置并置，周期约为20–30分钟。SuperDARN高分辨率拟合确定的FLR峰值流速为400–700 m / s。当FLR速度叠加在400-600 m / s的背景电离层对流上时，在BCBF事件发生的时间和地点附近，东西方向的总速度为800-1,300 m / s。场线谐振的峰值流量显示为受类似于BCBF的成对的向上和向下磁场对准的电流限制。观察结果表明BCBF和FLR之间存在因果关系。当FLR速度叠加在400-600 m / s的背景电离层对流上时，在BCBF事件发生的时间和地点附近，东西方向的总速度为800-1,300 m / s。场线谐振的峰值流量显示为受类似于BCBF的成对的向上和向下磁场对准的电流限制。观察结果表明BCBF与FLR之间存在因果关系。当FLR速度叠加在400-600 m / s的背景电离层对流上时，在BCBF事件发生的时间和地点附近，东西方向的总速度为800-1300 m / s。场线谐振的峰值流量显示为受类似于BCBF的成对的向上和向下磁场对准的电流限制。观察结果表明BCBF和FLR之间存在因果关系。