Abstract

Observations of two successive prolonged dipolarizations in the geomagnetic tail (at a distance of X ~ –18.3R_E from the Earth, where R_E is the Earth’s radius) according to the data obtained by the MMS mission are presented and analyzed. Eight dipolarization fronts (DF) were identified during these dipolarizations, and their propagation velocities and spatial scale were determined. The DF propagation velocities were found to be in the range between 130 and 360 km/s. The spatial scale of quasi-isolated DFs in the direction of their propagation at the beginning of the first dipolarization was ~1ρ_i (where ρ_i is the ion gyroradius), while the spatial scale of DFs observed in the flux pile up region was ~5ρ_i. Using methods of multi-spacecraft observation, densities of electric currents related to DFs were determined on a sub-ion scale. It is demonstrated that thin (\( \lesssim {\kern 1pt} 0.4{{\rho }_{i}}\)) intense electron current structures with amplitudes of current density varying from 10 to 60 nA/m² that form complex multi-scale three-dimensional configurations are observed simultaneously with the DFs.

中文翻译：

---

通过 MMS 任务观测近地磁尾部长时间偶极化过程中的小尺度磁和电流结构

摘要

介绍并分析了根据 MMS 任务获得的数据对地磁尾部（距地球X ~ –18.3 R _{E 的}距离，其中R _E是地球半径）中连续两次延长偶极化的观测结果。在这些偶极化过程中确定了八个偶极化锋 (DF)，并确定了它们的传播速度和空间尺度。发现测向传播速度在 130 和 360 公里/秒之间的范围内。在第一次偶极化开始时，准隔离 DF 在其传播方向上的空间尺度为 ~1ρ _i（其中 ρ _i是离子回旋半径），而在通量堆积区观察到的 DF 的空间尺度为~5ρ _i。使用多航天器观测方法，在亚离子尺度上确定了与 DF 相关的电流密度。结果表明，薄 ( \( \lesssim {\kern 1pt} 0.4{{\rho }_{i}}\) ) 强电子流结构，电流密度幅度从 10 到 60 nA/m ²不等，形成复杂的与DF同时观察多尺度三维配置。