THEMIS observation of a magnetotail current sheet flapping wave  

作　　者：Weijie Sun Suiyan Fu Quanqi Shi Qiugang Zong Zhonghua Yao Ting Xiao George Parks 

机构地区：[1]School of Earth and Space Sciences, Peking University [2]Shandong Provincial Key Laboratory of Optical Astronomy and Solar-Terrestrial Environment, School of Space Science and Physics, Shandong University at Weihai [3]Space Sciences Laboratory, UC Berkeley, Berkeley

出　　处：《Chinese Science Bulletin》2014年第2期154-161,共8页

基　　金：supported by the National Natural Science Foundation of China(41031065,41074106 and 40874086);Shandong Natural Science Foundation(JQ201112);partly by the National Basic Research Program of China(2011CB811404)

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 R E 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 R E.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.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.

关 键 词：电流片 磁尾 传播速度 不稳定性 波动模型 相关性分析 总体稳定 时间延迟 

分 类 号：P353[天文地球—空间物理学]