A generation mechanism of electrostatic waves and subsequent electron heating in the plasma sheet–lobe boundary region during magnetic reconnection
A generation mechanism of electrostatic waves and subsequent electron heating in the plasma sheet–lobe boundary region during magnetic reconnection
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DOI：
10.1029/2005ja011542
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发表时间：
2006-09
影响因子：
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通讯作者：
K. Fujimoto;S. Machida
中科院分区：
文献类型：
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作者：
K. Fujimoto;S. Machida
[1]通过在大系统中使用2-1/2维动力学模拟，研究了与磁重联相关的等离子体片-叶边界区域中高能电子的产生机制。我们的模拟代码在传统的粒子内单元代码中采用了自适应网格细化技术和粒子分裂算法，这使我们能够执行大规模的动力学模拟。结果表明，冷背景电子和高温强束流电子之间产生的电子双流不稳定性是导致磁重联发生时边界区域经常观察到的平顶电子的原因。由于静电势阱中的俘获效应，电子沿着环境磁场被快速加热，平顶电子分布的肩能达到几keV，与卫星观测结果一致。强束由垂直方向的高能和低能电子组成。前者电子来自通过 X 线附近的波瓣区域，而后者则源自等离子体片的相对边界区域。与磁重联相关的电子双流不稳定性也是产生边界区域中经常检测到的静电孤立波的原因。这表明静电湍流应该在磁重联过程中等离子体片-叶边界区域的强电子激发中发挥重要作用。
[1] A generation mechanism of high-energy electrons in the plasma sheet–lobe boundary region associated with magnetic reconnection is studied by using 2-1/2-dimensional kinetic simulations in a large system. Our simulation code employs the adaptive mesh refinement technique and the particle splitting algorithm to the conventional particle-in-cell code, which enable us to perform large-scale kinetic simulations. It is shown that the electron two-stream instability arising between the cold background electrons and the intense beam electrons with high temperature is responsible for the formation of the flat-topped electrons, which have been often observed in the boundary region when magnetic reconnection has occurred. Electrons are quickly heated along the ambient magnetic field due to the trapping effect in the electrostatic potential wells, and the shoulder energy of the flat-topped electron distribution reaches a few keV, consistent with satellite observations. The intense beam consists of high- and low-energy electrons in the perpendicular direction. The former electrons come from the lobe region through the vicinity of the X line, while the latter originate from the opposite boundary region of the plasma sheet. The electron two-stream instability in association with magnetic reconnection is also responsible for the generation of the electrostatic solitary waves that have been frequently detected in the boundary region. This indicates that the electrostatic turbulence should play an important role in strong electron energization in the plasma sheet–lobe boundary region during magnetic reconnection.