Evidence for newly closed magnetosheath field lines at the dayside magnetopause under northward IMF
Evidence for newly closed magnetosheath field lines at the dayside magnetopause under northward IMF
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DOI：
10.1029/2005ja011266
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发表时间：
2006-05
影响因子：
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通讯作者：
B. Lavraud;M. Thomsen;B. Lefebvre;S. Schwartz;K. Seki;T. Phan;Y. Wang;A. Fazakerley;H. Rème-H.-Rèm
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文献类型：
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作者：
B. Lavraud;M. Thomsen;B. Lefebvre;S. Schwartz;K. Seki;T. Phan;Y. Wang;A. Fazakerley;H. Rème-H.-Rèm
[1]分析了行星际磁场（IMF）作用下高纬磁层顶的结构。利用2001年至2003年56次磁层顶观测资料，对高纬度向阳面磁层顶外的磁鞘电子边界层的统计特性进行了研究。我们专注于低的绝对平行热通量在这一层中的发生和它的依赖于集群同时测量的磁场时钟角。低的绝对平行热通量的磁鞘电子边界层中的双向加热电子的存在下，主要观察到的局部磁场是向北。双向加热的电子被解释为新关闭的磁鞘场线，在高纬度磁层顶，尾部的尖点，在两个半球重新连接的签名。这项研究强烈表明，双高纬重联是一个站得住脚的低纬边界层的形成机制，并可能的冷，致密的等离子体片下向北IMF。虽然这种机制的效率（在质量和能量转移方面）仍有待研究，但它是一种明显的捕获北向IMF下太阳风等离子体的方法。
[1] We analyze the structure of the high-latitude magnetopause under steady interplanetary magnetic field (IMF). We use 56 magnetopause encounters of Cluster spacecraft from 2001 to 2003 to explore the statistical properties of the magnetosheath electron boundary layer, observed outside the high-latitude dayside magnetopause. We focus on the occurrence of low absolute parallel heat flux in this layer and its dependence on the magnetic field clock angle simultaneously measured by Cluster. The low absolute parallel heat fluxes result from the presence of bidirectional heated electrons in the magnetosheath electron boundary layer and are primarily observed when the local magnetic field is northward. The bidirectional heated electrons are interpreted as the signature of newly closed magnetosheath field lines that have reconnected at the high-latitude magnetopause, tailward of the cusp, in both hemispheres. This study strongly suggests that double high-latitude reconnection is a tenable mechanism for the formation of the low-latitude boundary layer and potentially of the cold, dense plasma sheet under northward IMF. Although the efficiency (in terms of mass and energy transfer) of this mechanism is still to be investigated, it is an obvious way of capturing solar wind plasma under northward IMF.