Swarm Satellite and EISCAT Radar Observations of a Plasma Flow Channel in the Auroral Oval Near Magnetic Midnight
Swarm Satellite and EISCAT Radar Observations of a Plasma Flow Channel in the Auroral Oval Near Magnetic Midnight
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群卫星和 EISCAT 雷达对近磁午夜极光椭圆区等离子体流通道的观测
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发表时间：
2018
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通讯作者：
D. Knudsen
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作者：
A. Aikio;H. Vanhamäki;A. Workayehu;I. Virtanen;K. Kauristie;L. Juusola;S. Buchert;D. Knudsen
我们目前的Swarm卫星和EISCAT雷达观测的电动力学参数在午夜部门在高纬度地区。最显著的特征是黎明对流单体内极帽边界赤道方向的等离子体流动通道。该流动通道在纬度上宽1.5°，包含150 mV/m的向南电场，对应于F区电离层中3，300 m/s的向东等离子体速度。理论计算的离子温度增加所产生的观测离子速度是一致的EISCAT雷达的测量。极光椭圆的总宽度约为纬度10°。向极部分以电场为主，电导率低，有流动通道;向赤道部分以电导率为主，至少有5个极光弧。向西电射流的主体在电导率主导区流动，但向电场主导区延伸。根据Kamide和Kokubun（1996）的研究，整个午夜向西的电急流都是电导率主导的，因此所研究的事件挑战了传统的观点。亚暴开始后观察到流动通道。我们认为，所观察到的流动通道，这是与13千伏的水平电位差，适应增加的夜侧等离子体流在亚暴膨胀阶段的结果，在近地磁尾重连。
We present Swarm satellite and EISCAT radar observations of electrodynamical parameters in the midnight sector at high latitudes. The most striking feature is a plasma flow channel located equatorward of the polar cap boundary within the dawn convection cell. The flow channel is 1.5° wide in latitude and contains southward electric field of 150 mV/m, corresponding to eastward plasma velocities of 3,300 m/s in the F‐region ionosphere. The theoretically computed ion temperature enhancement produced by the observed ion velocity is in accordance with the measured one by the EISCAT radar. The total width of the auroral oval is about 10° in latitude. While the poleward part is electric field dominant with low conductivity and the flow channel, the equatorward part is conductivity dominant with at least five auroral arcs. The main part of the westward electrojet flows in the conductivity dominant part, but it extends to the electric field dominant part. According to Kamide and Kokubun (1996), the whole midnight sector westward electrojet is expected to be conductivity dominant, so the studied event challenges the traditional view. The flow channel is observed after substorm onset. We suggest that the observed flow channel, which is associated with a 13‐kV horizontal potential difference, accommodates increased nightside plasma flows during the substorm expansion phase as a result of reconnection in the near‐Earth magnetotail.