Evidence of Alfvén Waves Generated by Mode Coupling in the Magnetotail Lobe
Evidence of Alfvén Waves Generated by Mode Coupling in the Magnetotail Lobe
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DOI：
10.1029/2021gl096359
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发表时间：
2021-12
影响因子：
5.2
通讯作者：
Jicheng Sun;Guoqiang Wang;Tielong Zhang;Hongqiao Hu;Huigen Yang
中科院分区：
文献类型：
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作者：
Jicheng Sun;Guoqiang Wang;Tielong Zhang;Hongqiao Hu;Huigen Yang
模式耦合是激发Alfvén波的一种重要机制，并且已经基于数值模拟进行了广泛的研究。然而，在磁尾叶中没有发现关于这种机制的直接观测证据。在这里，我们报告了一个现场观察，一个阿尔文波的周期为几分钟，显然是相关的快模式波在磁尾瓣的基础上观察的集群航天器。这些波发生在阿尔文速度在太阳风动压增强期间具有梯度的区域。这表明阿尔文波是在阿尔文速度有梯度的区域由模转换产生的，而快模波可能是由太阳风驱动的。我们的观测为磁层中波的产生和能量转换提供了重要的见解。
Mode coupling is an important mechanism to excite Alfvén waves and has been extensively investigated based on numerical simulations. However, no direct observational evidence has been found regarding to this mechanism in the magnetotail lobe. Here, we report an in‐situ observation that an Alfvén wave with a period of several minutes is clearly relevant to a fast mode wave in the magnetotail lobe based on observations of the Cluster spacecraft. These waves occur at the region where the Alfvén speed has a gradient during an enhancement of the solar wind dynamic pressure. This suggests that the Alfvén wave is generated by the mode conversion at the region where the Alfvén speed has a gradient, and the fast mode wave might be driven by the solar wind. Our observations provide an important insight into the wave generation and energy conversion in the magnetosphere.