中文摘要：

一个 flapping 波浪被 THEMIS-B (P1 ) 观察，黎明上的 THEMIS-C (P2 ) 探针 magnetotail 站在一起，当太阳的风通常是稳定的时。磁性的活动是相当弱的，建议这个 flapping 波浪被内部不稳定性产生，它通常发生在磁性的安静时间期间。我们 flapping 波浪与至少 3.7 RE 的排列尾巴的规模向下正在宣传并且没出现的分析表演很从 P1 在它的繁殖期间在形状改变到 P2。关联分析采用了估计时间在相应一半之间落后沿着当前的表正常方向的宣传速度在开始互相接近了，但是以后线性地增加了的 P1 和 P2 表演的波形。flapping 波浪的平均波长是约 4 RE。理论分析建议乘气球类型波浪模型不能是为观察 flapping 波浪的机制，但是磁性的双坡度不稳定性模型是一个更嘴巧的候选人。

英文摘要：

A flapping wave was observed by THEMIS-B （P1） and THEMIS-C （P2） probes on the dawn side of the magnetotail, while the solar wind was generally stable. The magnetic activity was quite weak, suggesting that this flapping wave was generated by an internal instability, which normally occurs during magnetic quiet times. Our analysis shows that the flapping wave was propagating downward with a tail-aligned scale of at least 3.7 RE and did not show much change in shape during its propagation from P1 to P2. Correlation analysis employed to estimate the time lag between the corresponding half waveforms of P1 and P2 shows that the propagating velocities along the current sheet normal directions were close to each other in the beginning, but increased linearly later on. The average wavelength of the flapping wave is approximately 4 RE. Theoretical analysis suggests that the ballooning type wave model may not be the mechanism for the observed flapping wave, but that the magnetic double-gradient instability model is a more plausible candidate.