Magnetic flux ropes (MFRs)—transient magnetic structures widely observed in Earth's magnetosphere—play crucial roles in particle acceleration and energy dissipation. MFRs above ion scale have been well studied, while MFRs at subion scales and their coupling with larger-scale ropes still remains not well understood. In this paper, we present the first observation of a subion-scale MFR nested in an ion-scale MFR, using high-resolution data from the magnetospheric multiscale (MMS) mission. We find that the subion-scale MFR hosts more intense plasma activity than the ion-scale MFR, including distinct electron agyrotropy and strong electromagnetic turbulence. In addition, axis of the subion-scale MFR is oblique to that of the ion-scale MFR, indicating that their generation may be ascribed to 3D magnetic reconnection. Observations of such cross-scale structure may shed new lights into understanding energy cascade in space plasmas.

中文翻译：

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亚离子级通量绳嵌套在地球磁尾中的离子级通量绳内

磁通绳（MFR）——在地球磁层中广泛观察到的瞬态磁结构——在粒子加速和能量耗散中起着至关重要的作用。离子级以上的 MFR 已得到很好的研究，而亚离子级的 MFR 及其与更大规模绳索的耦合仍不清楚。在本文中，我们使用来自磁层多尺度 (MMS) 任务的高分辨率数据，首次对嵌套在离子尺度 MFR 中的亚离子尺度 MFR 进行了观察。我们发现亚离子级 MFR 比离子级 MFR 具有更强烈的等离子体活动，包括明显的电子回旋性和强电磁湍流。此外，亚离子尺度 MFR 的轴与离子尺度 MFR 的轴倾斜，表明它们的产生可能归因于 3D 磁重联。