A superposed epoch analysis of the regions 1 and 2 Birkeland currents observed by AMPERE during substorms
A superposed epoch analysis of the regions 1 and 2 Birkeland currents observed by AMPERE during substorms
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DOI：
10.1002/2014ja020500
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发表时间：
2014-12
期刊：
影响因子：
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通讯作者：
J. Coxon;S. Milan;Lasse Boy Novock Clausen;Brian J. Anderson;H. Korth
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文献类型：
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作者：
J. Coxon;S. Milan;Lasse Boy Novock Clausen;Brian J. Anderson;H. Korth
我们对亚暴期间活动磁层和行星电动力学响应实验（AMPERE）观测到的伯克兰电流（场向电流）的演变进行了叠加时代分析。该研究由SuperMAG实验提供的2900个亚暴组成。我们发现，目前的椭圆形扩大和收缩的过程中的亚暴周期和电流的大小增加接近亚暴发病，并进一步增强在扩张阶段。随后，我们根据亚暴的起始纬度（磁层中开放磁通量的代理）对亚暴进行分类，并发现在低纬度亚暴的整个时期，Birkeland电流都显着较高。我们的结果与之前的研究一致，即当亚暴开始时开放通量较大时，亚暴强度更强，闭合的开放通量也更多。我们把这些研究结果的背景下，以前的工作，连接白天和黑夜的重新连接率，伯克兰目前的优势和位置。
We perform a superposed epoch analysis of the evolution of the Birkeland currents (field‐aligned currents) observed by the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE) during substorms. The study is composed of 2900 substorms provided by the SuperMAG experiment. We find that the current ovals expand and contract over the course of a substorm cycle and that currents increase in magnitude approaching substorm onset and are further enhanced in the expansion phase. Subsequently, we categorize the substorms by their onset latitude, a proxy for the amount of open magnetic flux in the magnetosphere, and find that Birkeland currents are significantly higher throughout the epoch for low‐latitude substorms. Our results agree with previous studies which indicate that substorms are more intense and close more open magnetic flux when the amount of open flux is larger at onset. We place these findings in the context of previous work linking dayside and nightside reconnection rate to Birkeland current strengths and locations.