Institute of Space Physics and Applied Technology, Peking University, Beijing, 100871, China.
Geophysical Institute, University of Alaska Fairbanks, Fairbanks, AK, 99775, USA.
Nat Commun. 2019 Mar 4;10(1):1040. doi: 10.1038/s41467-019-08971-y.
Magnetic cavities (sometimes referred to as magnetic holes) at electron kinetic scale are thought to be one of the extremely small intermittent structures formed in magnetized turbulent plasmas, where the turbulence energy cascaded down to electron scale may finally be dissipated and consequently energize the electrons. However, the geometry and formation of these structures remain not definitively resolved. Here we discuss an electron scale magnetic cavity embedded in a proton scale magnetic cavity observed by the MMS spacecraft in the magnetosheath. By applying an innovative particle sounding technique, we directly depict the boundary of the electron scale magnetic cavity and uncover the geometry. We find that this structure is nearly circular with a radius of 10.0 km and its formation is due to the diamagnetic current. Investigation of the electron scale structure is only recently made possible by the high spatial and temporal resolution provided by MMS observations.
电子动力学尺度上的磁腔（有时也称为磁孔）被认为是在磁化湍流等离子体中形成的极其微小的间歇结构之一，在那里，湍流能量级联到电子尺度最终可能被耗散，并因此给电子提供能量。然而，这些结构的几何形状和形成方式仍未得到明确解决。在这里，我们讨论了由 MMS 航天器在磁鞘中观测到的嵌入在质子尺度磁腔中的电子尺度磁腔。通过应用一种创新的粒子探测技术，我们直接描绘了电子尺度磁腔的边界并揭示了其几何形状。我们发现，这个结构几乎是圆形的，半径为 10.0 公里，其形成是由于抗磁性电流。对电子尺度结构的研究直到最近才成为可能，这要归功于 MMS 观测提供的高空间和时间分辨率。
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