A Deep Learning‐Based Approach for Modeling the Dynamics of AMPERE Birkeland Currents
A Deep Learning‐Based Approach for Modeling the Dynamics of AMPERE Birkeland Currents
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DOI：
10.1029/2020ja027908
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发表时间：
2020-08
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通讯作者：
B. Kunduri;M. Maimaiti;J. Baker;J. Ruohoniemi;B. Anderson;S. Vines
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作者：
B. Kunduri;M. Maimaiti;J. Baker;J. Ruohoniemi;B. Anderson;S. Vines
伯克兰磁场对准电流（FAC）系统的存在在一个多世纪前就被提出，从那时起，它对于研究太阳风-磁层-电离层耦合的本质就引起了极大的兴趣。在本文中，我们提出了深度学习架构的首次应用，使用来自活跃磁层和行星电动力学响应实验（AMPERE）的数据对伯克兰电流进行建模。该模型使用几个不同参数（例如行星际磁场 (IMF)、太阳风以及地磁和太阳指数）的 1 小时时间历史作为输入，以确定北半球伯克兰电流的全球分布。我们对稳定 IMF 条件下以及 IMF 可变时的模型和箱平均统计模式进行了比较。我们的深度学习模型与箱平均模式表现出良好的一致性，捕获了几个突出的大尺度特征，例如区域 1 和区域 2 FAC、NBZ 电流系统、尖点电流及其季节变化。然而，当 IMF 和太阳风条件不稳定时，我们的模型可以更准确地了解伯克兰电流随时间的演变。 IMF 方向突然改变后 FAC 的重新配置可以在其细节中追踪到。发现 FAC 的大小随着 e 折叠时间的变化而变化，而 e 折叠时间随季节和 MLT 的变化而变化。当 IMF Bz 在长时间向北定向后转向南时，NBZ 电流呈指数衰减，e 折叠时间约为 25 分钟，而区域 1 电流则根据 MLT，以 6-20 分钟的 e 折叠时间增长。
The existence of Birkeland magnetic field‐aligned current (FAC) system was proposed more than a century ago, and it has been of immense interest for investigating the nature of solar wind‐magnetosphere‐ionosphere coupling ever since. In this paper, we present the first application of deep learning architecture for modeling the Birkeland currents using data from the Active Magnetosphere and Planetary Electrodynamics Response Experiment (AMPERE). The model uses a 1‐hr time history of several different parameters such as interplanetary magnetic field (IMF), solar wind, and geomagnetic and solar indices as inputs to determine the global distribution of Birkeland currents in the Northern Hemisphere. We present a comparison between our model and bin‐averaged statistical patterns under steady IMF conditions and also when the IMF is variable. Our deep learning model shows good agreement with the bin‐averaged patterns, capturing several prominent large‐scale features such as the Regions 1 and 2 FACs, the NBZ current system, and the cusp currents along with their seasonal variations. However, when IMF and solar wind conditions are not stable, our model provides a more accurate view of the time‐dependent evolution of Birkeland currents. The reconfiguration of the FACs following an abrupt change in IMF orientation can be traced in its details. The magnitude of FACs is found to evolve with e‐folding times that vary with season and MLT. When IMF Bz turns southward after a prolonged northward orientation, NBZ currents decay exponentially with an e‐folding time of ∼25 min, whereas Region 1 currents grow with an e‐folding time of 6–20 min depending on the MLT.