A dipolarization of the background magnetic field was observed during a conjunction of the Magnetospheric Multiscale (MMS) spacecraft and Van Allen Probe B on September 22, 2018. The spacecraft were located in the inner magnetosphere at L ∼ 6–7 just before midnight magnetic local time (MLT). The radial separation between MMS and Probe B was ∼1R_E. Gradual dipolarization or an increase of the northward component B_Z of the background field occurred on a timescale of minutes. Exploration of energization and Radiation in Geospace located 0.5 MLT eastward at a similar L shell also measured a gradual increase. The spatial scale was of the order of 1 R_E. On top of that, MMS and Probe B measured B_Z increases, and a decrease in one case, on a timescale of seconds, accompanied by large electric fields with amplitudes > several tens of mV/m. Spatial scale lengths were of the order of the ion inertial length and the ion gyroradius. The inertial term in the momentum equation and the Hall term in the generalized Ohm's law were sometimes non‐negligible. These small‐scale variations are discussed in terms of the ballooning/interchange instability and kinetic Alfvén waves among others. It is inferred that physics of multiple scales was involved in the dynamics of this dipolarization event.

中文翻译：

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内磁层双极化事件的多仪器研究

9月22日的磁层多（MMS）航天器和范艾伦探测器B的结合过程中观察到的背景磁场的偶极，2018。宇宙飞船分别位于在所述内磁层大号 〜6-7午夜磁性本地之前时间（MLT）。MMS和探针B之间的径向间距为〜1 - [R _ë。在几分钟的时间尺度上发生了逐渐的双极化或背景场的北向分量B _Z的增加。在类似的L壳向东0.5 MLT处探索的地球空间中的增能和辐射，也发现其逐渐增加。空间尺度约为1 R _E。最重要的是，MMS和探针B的测量B _Z在几秒钟的时间尺度上增加，在一种情况下减少，同时伴随着振幅大于几十mV / m的大电场。空间尺度长度约为离子惯性长度和离子陀螺半径。动量方程中的惯性项和广义欧姆定律中的霍尔项有时不可忽略。这些小范围的变化是根据气球膨胀/互换不稳定性和动力学Alfvén波等进行讨论的。可以推断，多尺度物理学都参与了该双极化事件的动力学过程。