Cluster observations in the magnetotail during sudden and quasiperiodic solar wind variations
Cluster observations in the magnetotail during sudden and quasiperiodic solar wind variations
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DOI：
10.1029/2003ja010328
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发表时间：
2004-04
影响因子：
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通讯作者：
Khan-Huk Kim;C. Cattell;Dong‐Hun Lee;A. Balogh;E. Lucek;M. André;Y. Khotyaintsev;H. Rème
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文献类型：
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作者：
Khan-Huk Kim;C. Cattell;Dong‐Hun Lee;A. Balogh;E. Lucek;M. André;Y. Khotyaintsev;H. Rème
2001年10月11日（第284天）太阳风不连续期间，在磁尾星团上的三个航天器观测到Ey分量明显的双极（负/正）特征，这导致了地面上的突然开始（sc）。正的Ey扰动伴随着向北/向南的等离子体流动和Bx增强，这是主要的磁场分量。从等离子体流和磁场中估计的电流值与观测到的电流值吻合较好。因此，正的Ey扰动可以解释为向内等离子体运动的特征，对应于磁层顶的压缩。在Ey负摄动期间，磁场的增加主要是由于By和Bz的增加，而不是由于Bx的增加。与正Ey摄动不同，负Ey摄动与估计的Ey不一致。因此负的Ey特征似乎与等离子体运动没有直接的联系。观测到的磁场和流的变化可能与磁尾的变形有关，这是由于太阳风的不连续性而导致的。星系团的三艘航天器可以确定sc锋向尾部传播的方向和形状。在sc事件发生后，我们还在Kakioka低纬度地面站观测到准周期地磁扰动（L = 1.25）。它们与磁尾团簇处的磁场扰动高度相关（Xgse = ~ 12 RE）。我们表明，这些扰动的来源是准周期太阳风变化叠加在增加的太阳风压力背后的行星际不连续。
[1] A clear bipolar (negative/positive) signature in the Ey component was observed by three spacecraft on Cluster in the magnetotail during the passage of a solar wind discontinuity on October 11, 2001 (day 284), which caused a sudden commencement (sc) on the ground. The positive Ey perturbation was accompanied by the northward/dawnward plasma flow and the Bx enhancement, which is the dominant magnetic field component. The estimated Ey from the plasma flow and magnetic field was in good agreement with the observed Ey. Thus the positive Ey perturbation can be interpreted to be the signature of inward plasma motions, corresponding to the compression of the magnetopause. During the interval of the negative Ey perturbation, the magnetic field increase was mainly due to the increase in By and Bz, not in Bx. Unlike the positive Ey perturbation, the negative Ey perturbation was not consistent with the estimated Ey. Therefore the negative Ey signature does not seems to have a direct connection with plasma motions. The observed field and flow variations may be associated with a deformation of the magnetotail due to the solar wind discontinuity moving tailward. The direction and shape of the sc front propagating tailward can be confirmed by three spacecraft of Cluster. We also observed quasiperiodic geomagnetic perturbations at the low-latitude ground station Kakioka (L = 1.25) following the sc event. They were highly correlated with the magnetic field perturbations at Cluster in the magnetotail (Xgse = ∼12 RE). We show that the source of these perturbations is the quasiperiodic solar wind variations superposed on the increased solar wind pressure behind the interplanetary discontinuity.