Substorm onset: Current sheet avalanche and stop layer
Substorm onset: Current sheet avalanche and stop layer
复制标题
亚暴爆发：当前片状雪崩和停止层
DOI：
10.1002/2014ja020571
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发表时间：
2015
期刊：
影响因子：
--
通讯作者：
G. Haerendel
中科院分区：
文献类型：
--
作者：
G. Haerendel
提出了一种新的关于亚暴开始和破裂弧线性质的假设。有两个主要组成部分，电流片雪崩和停止层。第一种是指从尾部中心电流片向地球流动的等离子体和磁通量，由自发或由与极光流光的某种未知相互作用触发，或在生长阶段结束时突然出现的向东流动。第二部分提供了一种在磁层和尾部交界处突然停止流动的机制，并提取动量和能量，这些动量和能量将部分在当地处理，部分作为坡印亭通量传输到电离层。停止层具有离子惯性长度量级的宽度。自由进入的离子和磁化的电子的不同动力学产生了一个电场，它阻止了离子的流动，并驱动了霍尔电流，流动的动量通过霍尔电流转移到磁场中。一个简单的形式主义被用来描述过程的操作，并使定量的结论成为可能。一个重要的结论是，必然停止层在经度上也是高度结构化的。这为解体弧的粗射线结构提供了一个自然的解释，它是能量和动量传输的基本路径的表现。与射线对准的电流在向上和向下方向之间保持平衡。虽然雪崩被用来解释尾巴内缘的自发亚暴开始，但破裂弧长达数分钟的扩张被认为是近地中性线气流爆发到达后继续形成新的停止层的证据。这与早先关于分手弧线性质的结论一致。小尺度结构、传播速度和能量通量与观测结果定量一致。然而，平衡的小尺度洋流不能构成亚暴洋流楔形。后者的来源必须位于近偶极磁层中停止层的正地面上，并由气流爆发的内部能量提供动力。停止层机制在某种程度上是重新连接的逆机制，因为它将流动转换为电磁能量，并可能在天体物理等离子体中有广泛的应用。
A new scenario is presented for the onset of a substorm and the nature of the breakup arc. There are two main components, current sheet avalanche and stop layer. The first refers to an earthward flow of plasma and magnetic flux from the central current sheet of the tail, triggered spontaneously or by some unknown interaction with an auroral streamer or a suddenly appearing eastward flow at the end of the growth phase. The second offers a mechanism to stop the flow abruptly at the interface between magnetosphere and tail and extract momentum and energy to be partially processed locally and partially transmitted as Poynting flux toward the ionosphere. The stop layer has a width of the order of the ion inertial length. The different dynamics of the ions entering freely and the magnetized electrons create an electric polarization field which stops the ion flow and drives a Hall current by which flow momentum is transferred to the magnetic field. A simple formalism is used to describe the operation of the process and to enable quantitative conclusions. An important conclusion is that by necessity the stop layer is also highly structured in longitude. This offers a natural explanation for the coarse ray structure of the breakup arc as manifestation of elementary paths of energy and momentum transport. The currents aligned with the rays are balanced between upward and downward directions. While the avalanche is invoked for explaining the spontaneous substorm onset at the inner edge of the tail, the expansion of the breakup arc for many minutes is taken as evidence for a continued formation of new stop layers by arrival of flow bursts from the near‐Earth neutral line. This is in line with earlier conclusions about the nature of the breakup arc. Small‐scale structure, propagation speed, and energy flux are quantitatively consistent with observations. However, the balanced small‐scale currents cannot constitute the substorm current wedge. The source of the latter must be located just earthward of the stop layer in the near‐dipolar magnetosphere and be powered by the internal energy of the flow bursts. The stop layer mechanism is in some way the inverse of reconnection, as it converts flow into electromagnetic energy, and may have wide applicability in astrophysical plasmas.
影响因子：
5.2
作者：
Donovan, E.;Liu, W.;Rae, I. J.
通讯作者：
Rae, I. J.