Formation and motion of horse collar aurora events
Formation and motion of horse collar aurora events
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马项圈极光事件的形成和运动
DOI：
10.1002/essoar.10512714.1
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发表时间：
2022
期刊：
影响因子：
--
通讯作者：
Bower G
中科院分区：
文献类型：
--
作者：
Bower G
极冠可以通过极光椭圆的黄昏和黎明部分向极地扩展而变成泪滴状，形成所谓的马领极光（HCA）。HCA的形成与双瓣重联（DLR）有关，其中磁通量在向阳侧磁层顶闭合。HCA的形成需要较长时间的IMF北移。HCA之前已经在国防气象卫星计划（DMSP）航天器F16，F17和F18上的特殊传感器紫外光谱成像仪（SSUSI）仪器捕获的紫外图像中被识别出来。与DMSP/SSUSI相比，Redline Geospace Observatory（REGO）Resolute Bay站点同时具有630.0 nm全天空相机（ASC）数据的事件现在被更详细地研究，利用ASC图像的更高节奏。根据事件结束时的IMF条件，对11个HCA事件进行了研究和分类。五个事件被发现结束通过向南转向的国际货币基金组织，两个结束与positiveBydominantly国际货币基金组织和4个negitiveBydominantly。在正（负）By下，弧在北方半球向黄昏（黎明）移动，而在南半球则相反。在向南转向的情况下，弧向赤道移动。一个事件是特别感兴趣的，因为它发生时，有一个跨极弧（TPA）也存在。了解HCA的演变将有助于更详细地研究DLR。
The polar cap can become teardrop shaped through the poleward expansion of the dusk and dawn sectors of the auroral oval, to form what is called horse collar aurora (HCA). The formation of HCA has been linked to dual‐lobe reconnection (DLR) where magnetic flux is closed at the dayside magnetopause. A prolonged period of northward IMF is required for the formation of HCA. HCA have previously been identified in UV images captured by the Special Sensor Ultraviolet Spectrographic Imager (SSUSI) instrument on‐board the Defense Meteorological Satellite Program (DMSP) spacecraft F16, F17 and F18. Events that have concurrent 630.0 nm all‐sky camera (ASC) data from the Redline Geospace Observatory (REGO) Resolute Bay site are now studied in more detail, making use of the higher cadence of the ASC images compared to DMSP/SSUSI. 11 HCA events are studied and classified based on the IMF conditions at the end of the event. Five of the events were found to end via a southward turning of the IMF, two end with positiveBydominated IMF and four with negativeBydominance. Under positive (negative)Bythe arcs move duskward (dawnward) in the northern hemisphere with the opposite true in the southern hemisphere. Under a southward turning the arcs move equatorward. One event is of particular interest as it occurred while there was a transpolar arc (TPA) also present. Understanding the evolution of HCA will allow DLR to be studied in more detail.