Global role of E|| in magnetopause reconnection : An explicit demonstration
Global role of E|| in magnetopause reconnection : An explicit demonstration
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DOI：
10.1029/2000ja000062
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发表时间：
2001-07
影响因子：
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通讯作者：
G. Siscoe;G. Erickson;B. Sonnerup;N. Maynard;K. Siebert;D. Weimer;W. White
中科院分区：
文献类型：
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作者：
G. Siscoe;G. Erickson;B. Sonnerup;N. Maynard;K. Siebert;D. Weimer;W. White
我们使用全球MHD模拟计算了E‖在磁层顶面上的分布，该分布由最后一个闭合场线面表示。在MHD代码中，E‖是磁重联的代理。沿着开放和闭合磁场线之间的拓扑分隔线积分E‖，得到磁层顶的全球重联率。在本文研究的情况下，行星际磁场（IMF）正好处于黄昏，我们发现全球重联率为~ 49千伏，与从极帽测量中推断出的电位相当。该练习演示了一般重联定理的应用，该定理实际上等同于E‖重联。它为磁层顶E‖等高线重联的MHD成像铺平了道路。结果还说明了在全球范围内不被普遍认识的平行势的性质。在南北两极帽之间的一些闭合场线上存在着几乎完全的磁层顶重联电压，因此它们离开黎明时，南半球具有相当大的正极性，进入黄昏时，北半球具有相当大的负极性。一个意想不到的发现是磁层顶和电离层在北部黎明和南部黄昏扇区之间存在大量平行电位（在10和15千伏之间）。（将“黎明”和“黄昏”换成“黎明IMF”。）这种电势具有加速电子进入黄昏区域电离层的极性，因此，可能是在沉淀电子中看到的“热点”的起源。
We use a global MHD simulation to compute the distribution of E‖ on the face of the magnetopause as represented by the last closed field line surface. In MHD codes, E‖ is a proxy for magnetic reconnection. Integrating E‖ along the topological separator line between open and closed magnetic field lines gives the global reconnection rate at the magnetopause. In the case studied here, where the interplanetary magnetic field (IMF) is precisely duskward, we find the global reconnection rate to be ∼49 kV, comparable to potentials inferred from measurements made in the polar cap. The exercise demonstrates an application of a general reconnection theorem that, in effect, equates reconnection with E‖. It prepares the way for MHD imaging of reconnection in terms of contours of E‖ on the magnetopause. The result also illustrates a property of parallel potentials in the global context that is not generally recognized. Nearly the full magnetopause reconnection voltage exists on some closed field lines between the northern and southern polar caps, so that they leave the dawn, southern hemisphere with a sizable positive polarity and enter the dusk, northern hemisphere with a sizable negative polarity. An unexpected finding is a substantial parallel potential (between 10 and 15 kV) between the magnetopause and the ionosphere in northern dawn and southern dusk sectors. (Interchange “dawn” and “dusk” for dawnward IMF.) This potential has the polarity that accelerates electrons into the ionosphere in the dusk sector and, so, might be the origin of the “hot spot” seen there in precipitating electrons.