GEOTAIL observations of flow velocity and north‐south magnetic field variations in the near and mid‐distant tail associated with substorm onsets
GEOTAIL observations of flow velocity and north‐south magnetic field variations in the near and mid‐distant tail associated with substorm onsets
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DOI：
10.1029/1999gl900030
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发表时间：
1999-03
影响因子：
5.2
通讯作者：
S. Machida;Y. Miyashita;A. Ieda;A. Nishida;T. Mukai;Y. Saito;S. Kokubun
中科院分区：
文献类型：
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作者：
S. Machida;Y. Miyashita;A. Ieda;A. Nishida;T. Mukai;Y. Saito;S. Kokubun
应用叠加历元分析方法，研究了−坐标下−7.5>；X(RE)>；−52.5和GSM15<；Y(RE)<；15区域磁尾等离子体流和磁场的时间变化。利用Kakioka站的PI-2脉动确定了亚暴的开始时间。结果表明，与等离子体云相关的尾流在PI-2开始前约2~3分钟开始，而向地面流动在开始前1分钟开始趋于一致。通过得到北向磁场分量与PI-2开始前10.5~7.5min之间的偏离度，研究了该分量的变化。我们发现，在夜幕降临后的午夜前尾部，向北磁场在X∼−10RE处同时增加，而在X∼−28RE处同时减小。这些变化分别对应于偶极化和等离子体的形成。
Temporal changes in the plasma flow and magnetic fields of the Earth's magnetotail in the region of −7.5 > X(RE) > −52.5 and −15 < Y(RE) < 15 in the GSM coordinates were studied by applying a superposed epoch analysis method to 263 substorm events observed by GEOTAIL spacecraft. The onset times of the substorms were determined with Pi‐2 pulsations at Kakioka station. It was found that the tailward flow associated with plasmoids started about 2 or 3 min before the Pi‐2 onsets, and the earthward flow became somewhat coherent 1 min before the onsets. The variation of the northward magnetic field component was investigated by obtaining the deviation of this component from that in the interval from 10.5 to 7.5 min before the Pi‐2 onsets. We found that the northward magnetic field increased at X ∼ −10RE and decreased at X ∼ −28RE simultaneously in the premidnight tail immediately after the onsets. These variations definetely correspond to the dipolarization and plasmoid formation, respectively.