Kink-like flapping motions of current sheets are commonly observed in the magnetotail. Such oscillations have periods of a few minutes down to a few seconds and they propagate toward the flanks of the plasma sheet. Here, we report a short-period ( s) flapping event of a thin current sheet observed by the Magnetospheric Multiscale spacecraft in the dusk-side plasma sheet following a fast Earthward plasma flow. We characterize the flapping structure using the multi-spacecraft spatiotemporal derivative and timing methods, and we find that the wave-like structure is propagating along the average current direction with a phase velocity comparable to the ion velocity. We show that the wavelength of the oscillating current sheet scales with its thickness as expected for a drift-kink mode. The decoupling of the ion bulk motion from the electron bulk motion suggests that the current sheet is thin. We discuss the presence of the lower hybrid waves associated with gradients of density as a broadening process of the thin current sheet.

中文翻译：

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短期离子尺度电流片扑动的观察

在磁尾中通常观察到电流片的扭结状拍打运动。这种振荡的周期从几分钟到几秒不等，它们会向等离子体片的侧面传播。在这里，我们报告了一个短期（s) 磁层多尺度航天器在快速向地等离子流之后在黄昏侧等离子片中观察到的薄电流片的扑动事件。我们使用多航天器时空导数和计时方法来表征扑翼结构，我们发现波状结构沿平均电流方向传播，相速度与离子速度相当。我们表明，如漂移扭结模式所预期的那样，振荡电流片的波长与其厚度成比例。离子体运动与电子体运动的分离表明电流片很薄。我们将与密度梯度相关的较低混合波的存在作为薄电流片的加宽过程进行讨论。