| 磁尾地向传播等离子体团的模拟研究 |
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| 引用本文： | 杨红昂,金曙平.磁尾地向传播等离子体团的模拟研究[J].地球物理学报,2002,45(5):611-623. |
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| 作者姓名： | 杨红昂 金曙平 |
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| 作者单位： | 中国科学技术大学地球与空间科学系,合肥,230026 |
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| 基金项目： | 国家自然科学基金资助项目 (4 0 1 740 442983 40 40 )，部分受到一流大学空间物理基地资助 |
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| 摘 要： | 卫星观测证实了磁尾等离子体团与亚暴活动的相关性,除了具有北-南双极特征的尾向传播等离子体团外,还发现地向传播等离子体团,它们表现为南-北双极中性片事件和南-北双极瓣区讯号. 资料分析表明:南-北双极讯号的出现几率远低于北-南双极讯号,并且南-北双极事件主要发生于行星际磁场北向和地磁宁静条件,它们往往与小的孤立的地磁亚暴相关. 本文根据地磁宁静时期(IMF Bz北向且By≥Bz)越尾电场Ey分量的分布特点,对地向传播等离子体团作模拟研究. 两类算例的数值结果展示了通量绳磁结构及具有复杂闭合磁力线位形的等离子体团的基本特征,上述特征与尾向传播的等离子体团类似,与IMP 8卫星关于地向传播南-北中性片事件的观测特征大致相符. 数值结果还展示了与Schindler示意图相类似的磁力线拓扑位形,在一定程度上为南-北事件出现几率低作出了解释;并且揭示了磁尾中性片内越尾磁场分量By对磁重联发展的抑制作用. 本文的模拟研究说明:无论磁尾处于活动时期(IMF Bz为南向),还是宁静时期(IMF Bz为北向且By≥Bz),磁场重联均是磁尾等离子体加速和加热的通用机制.
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| 关 键 词： | 南-北双极中性片事件 地磁宁静时期 越尾磁场By分量 |
| 文章编号： | 0001-5733(2002)05-0611-13 |
| 收稿时间： | 2001-08-21 |
A NUMERICAL SIMULATION ON THE EARTHWARD PROPAGATING PLASMOIDS |
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| YANG HONG,ANG\ JIN SHU,PING.A NUMERICAL SIMULATION ON THE EARTHWARD PROPAGATING PLASMOIDS[J].Chinese Journal of Geophysics,2002,45(5):611-623. |
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| Authors: | YANG HONG ANG\ JIN SHU PING |
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| Institution: | University of Science and Technology of China,Hefei,230026, China |
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| Abstract: | The correlation between plasmoids and geomagnetic substorms has been demonstrated by satellite observations. In addition to the tailward propagating plasmoids with N S bipolar signatures,earthward propagating plasmoids have been found,which are characterized by plasma sheet S N bipolar events and lobe S N bipolar signatures. The occurrence rate of the S N bipolar events is apparently lower than that of the N S events. The S N bipolar events occur primarily during quiet geomagnetic and north IMF B z conditions,and are correlated with small isolated geomagnetic substorms. A 2.5 dimensional MHD simulation on the earthward propagating plasmoids has been carried out on the basis of the specific distribution of the cross tail electric fields E y component during geomagnetically quiet times （IMF B z is northward and B y ≥ B z ）. The simulation results of the two cases showed the major signatures of the flux rope magnetic structures and plasmoids with complex closed magnetic field lines. The similar signatures to tailward propagating plasmoids could be consistent with IMP 8 observations about the earthward propagating plasma sheet S N bipolar events.The results also displayed a configuration similar to the schematic given by Schindler,which may explain the low occurrence frequency of the S N events. It is noted that the dynamic growth of the magnetic reconnection becomes considerably suppressed for a strong cross tail magnetic field B y. In conclusion,the magnetic reconnection can be the genetic mechanism of the plasma acceleration and heating in the magnetotail in both geomagnetically active and quiet times,namely,under both southward and northward （with B y≥B z ） IMF conditions. |
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| Keywords: | Plasma sheet S N bipolar events Geomagnetically quiet times Cross tail magnetic field B y component |
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