Mesoscale F Region Neutral Winds Associated With Quasi-steady and Transient Nightside Auroral Forms
Mesoscale F Region Neutral Winds Associated With Quasi-steady and Transient Nightside Auroral Forms
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与准稳态和瞬变夜边极光形态相关的中尺度 F 区中性风
DOI：
10.1029/2018ja025457
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发表时间：
2018
期刊：
影响因子：
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通讯作者：
Mende, Stephen
中科院分区：
文献类型：
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作者：
Zou, Ying;Nishimura, Yukitoshi;Lyons, Larry;Conde, Mark;Varney, Roger;Angelopoulos, Vassilis;Mende, Stephen
在大尺度极光强迫的驱动下，高纬度中性风通常以双单体模式环流。然而，极光强迫也以各种类型的中尺度形式发生（即，在几十到几百公里的空间和几到几十分钟的时间），并且在中尺度上比在大尺度上包含更多的能量输入。一个问题出现了，即风是否以及如何对中尺度强迫作出反应。我们使用扫描多普勒成像仪、极光成像仪和雷达来表征与各种极光形式相关的区域风。观测到的极光包括一个准稳定的东西拉长弧线、一个准稳定的哈朗极光、瞬态流光和一个瞬态次暴向西移动的浪涌。我们发现风表现出独特的空间结构，以通道、漩涡和反转的形式出现。这样的结构与与极光相关的等离子体流的结构是一致的。风表现出与等离子体流动非常相似的时间演变，在流动后仅<~20分钟就达到了最大扰动。上述结果表明，热层通过离子阻力与电离层/磁层紧密耦合。<~20分钟的时间尺度可以部分地解释为与极光相关的强电离效应，部分地解释为风扰动不接近流扰动，而是在~20%时停止，这可能是由于动量力而不是离子阻力。
High‐latitude neutral winds often circulate in a two‐cell pattern as driven by large‐scale auroral forcing. However, auroral forcing also occurs in various types of mesoscale forms (i.e., tens to hundreds of kilometers in space and a few to tens of minutes in time) and contains more energy input over mesoscale than large scale. A question arises as to whether and how winds respond to the mesoscale forcing. We characterizeFregion winds associated with various types of auroral forms using scanning Doppler imagers, auroral imagers, and radars. The auroras examined include a quasi‐steady east‐west elongated arc, a quasi‐steady Harang aurora, transient streamers, and a transient substorm westward traveling surge. We find that winds exhibit distinct spatial structures, appearing as channels, vortices, and reversals. Such structures are consistent with the structures of the plasma flows associated with the auroras. Winds exhibit a temporal evolution very similar to the plasma flows and reach maximum perturbations only <~20 min after the flows. The above results suggest that the thermosphere is closely coupled to the ionosphere/magnetosphere through the ion drag force. The <~20‐min time scale can be partially explained by the strong ionization effect associated with the auroras and partially by the fact that the wind perturbations do not approach the flow perturbations but halt at ~20% possibly due to momentum forces other than the ion drag.