Birkeland currents during substorms: Statistical evidence for intensification of Regions 1 and 2 currents after onset and a localized signature of auroral dimming
Birkeland currents during substorms: Statistical evidence for intensification of Regions 1 and 2 currents after onset and a localized signature of auroral dimming
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亚暴期间的伯克兰洋流：1 区和 2 区洋流爆发后增强的统计证据以及极光变暗的局部特征
DOI：
10.1002/2017ja023967
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发表时间：
2017
期刊：
影响因子：
--
通讯作者：
Coxon J
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文献类型：
--
作者：
Coxon J
我们对来自AMPERE（主动磁层和行星电动力学响应实验）的Birkeland电流密度进行了叠加历元分析，使用由独立导出的数据集确定的孤立亚暴膨胀阶段开始。为了评估R1和R2电流是否对亚暴电流楔有贡献，我们将Birkeland电流的全球地图旋转到以亚暴开始的磁局地时间为中心的共同坐标系中。当考虑亚暴的纬度时，很明显R1和R2电流系统在亚暴的发生中都起作用，这与以往的研究发现R2电流不起作用相反。亚暴发生的纬度与R1和R2电流的交界面重合，可以推断R1电流正好在尾部闭合，R2电流正好在尾部相关电流中断的方向闭合。AMPERE是第一个对整个极帽的伯克兰电流进行近瞬时测量的数据集，该研究解决了先前使用AMPERE来检查亚风暴电流楔形形态的研究中的明显差异。最后，我们提出了亚暴发生前电流密度极局部降低的证据，并将其解释为Birkeland电流中极光变暗的第一个统计特征。
We conduct a superposed epoch analysis of Birkeland current densities from AMPERE (Active Magnetosphere and Planetary Electrodynamics Response Experiment) using isolated substorm expansion phase onsets identified by an independently derived data set. In order to evaluate whether R1 and R2 currents contribute to the substorm current wedge, we rotate global maps of Birkeland currents into a common coordinate system centered on the magnetic local time of substorm onset. When the latitude of substorm is taken into account, it is clear that both R1 and R2 current systems play a role in substorm onset, contrary to previous studies which found that R2 current did not contribute. The latitude of substorm onset is colocated with the interface between R1 and R2 currents, allowing us to infer that R1 current closes just tailward and R2 current closes just earthward of the associated current disruption in the tail. AMPERE is the first data set to give near‐instantaneous measurements of Birkeland current across the whole polar cap, and this study addresses apparent discrepancies in previous studies which have used AMPERE to examine the morphology of the substorm current wedge. Finally, we present evidence for an extremely localized reduction in current density immediately prior to substorm onset, and we interpret this as the first statistical signature of auroral dimming in Birkeland current.
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期刊：
Journal of Geophysical Research: Space Physics
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10.1002/2014ja020522
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2014
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Journal of Geophysical Research: Space Physics
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