We report observations of a magnetosheath jet followed by a period of decelerated background plasma. During this period, THEMIS-A magnetometer showed abrupt disturbances which, in the wavelet spectrum, appeared as prominent and irregular pulsations in two frequency bands (7.6–9.2 and 12–17 mHz) within the Pi2 range. The observations suggest—for the first time to our knowledge—that these pulsations were locally generated by the abrupt magnetic field changes driven by the jet’s interaction with the ambient magnetosheath plasma. Furthermore, similar pulsations, detected by THEMIS-D inside the magnetosphere with a 140 s time-lag (which corresponds to the propagation time of a disturbance traveling with Alfvénic speed), are shown to be directly associated with the ones in the magnetosheath, which raises the question of how exactly these pulsations are propagated through the magnetopause.

中文翻译：

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关于磁鞘射流周围等离子体流动模式引起的 Pi2 脉动的产生

我们报告了磁鞘射流的观察结果，然后是一段减速的背景等离子体。在此期间，THEMIS-A 磁力计显示出突然扰动，在小波谱中，在 Pi2 范围内的两个频段（7.6-9.2 和 12-17 mHz）中表现为显着且不规则的脉动。这些观察结果表明——据我们所知第一次——这些脉动是由喷流与周围磁鞘等离子体相互作用驱动的突然磁场变化局部产生的。此外，由 THEMIS-D 在磁层内检测到的类似脉动具有 140 秒的时滞（对应于以阿尔文速度传播的扰动的传播时间），被证明与磁鞘中的脉动直接相关，