We propose a mechanism for the formation of the horse‐collar auroral configuration during periods of strongly northward interplanetary magnetic field (IMF), invoking the action of dual‐lobe reconnection (DLR). Auroral observations are provided by the Imager for Magnetopause‐to‐Aurora Global Exploration (IMAGE) satellite and spacecraft of the Defense Meteorological Satellite Program (DMSP). We also use ionospheric flow measurements from DMSP and polar maps of field‐aligned currents (FACs) derived from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). Sunward convection is observed within the dark polar cap, with antisunward flows within the horse‐collar auroral region, together with the NBZ FAC distribution expected to be associated with DLR. We suggest that newly closed flux is transported antisunward and to dawn and dusk within the reverse lobe cell convection pattern associated with DLR, causing the polar cap to acquire a teardrop shape and weak auroras to form at high latitudes. Horse‐collar auroras are a common feature of the quiet magnetosphere, and this model provides a first understanding of their formation, resolving several outstanding questions regarding the nature of DLR and the magnetospheric structure and dynamics during northward IMF. The model can also provide insights into the trapping of solar wind plasma by the magnetosphere and the formation of a low‐latitude boundary layer and cold, dense plasma sheet. We speculate that prolonged DLR could lead to a fully closed magnetosphere, with the formation of horse‐collar auroras being an intermediate step.

中文翻译：

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双叶重连和马领极光

我们提出了在强北向行星际磁场（IMF）期间调用双瓣重连（DLR）作用的马领极光构造的形成机制。磁更年期至极光全球勘探（IMAGE）卫星和国防气象卫星计划（DMSP）的航天器提供了极光观测。我们还使用了来自DMSP的电离层流量测量结果以及源自主动磁层和行星电动力学响应实验（AMPERE）的场对准电流（FAC）的极坐标图。在黑暗的极地帽内观察到向阳对流，在马领极光区域内有逆向流，以及预计与DLR有关的NBZ FAC分布。我们建议新近封闭的通量在与DLR相关的反向波瓣对流模式内逆向运输，并到达黎明和黄昏，从而导致极帽获得泪珠形状，并在高纬度地区形成弱极光。马领极光是安静磁层的一个共同特征，该模型提供了对它们形成的初步了解，解决了有关北向IMF期间DLR的性质以及磁层结构和动力学的几个悬而未决的问题。该模型还可以为磁层捕获太阳风等离子体以及形成低纬度边界层和冷而致密的等离子体片提供深刻见解。我们推测长时间的DLR可能导致磁层完全封闭，而马领极光的形成是中间步骤。