双极化波前中交换不稳定性的自洽播种
Self-consistent Seeding of the Interchange Instability in Dipolarization Fronts
摘要：
我们报告了一个三维磁流体动力学模拟研究磁尾重联过程中的双极化锋的形成。在目前的三维模拟中发现的关键新功能是，重联过程中产生的磁通绳重联区域内的发展。这些通量绳是不稳定的扭结模式，并在黎明黄昏方向上引入自发结构。在重联下游形成的偶极锋强烈地受到扭折绳的影响。在锋面处，存在与加速度场方向相反的密度梯度，并导致交换不稳定性。我们提出了一个因果关系的证据，在那里的扭结通量绳的扰动与他们的自然和明确的尺度驱动器和选择的尺度的交换模式中的偶极锋。模拟结果与Themis任务观测到的测量结构进行了验证。
英文摘要：
We report a 3D magnetohydrodynamics simulation that studies the formation of dipolarization fronts during magnetotail reconnection. The crucial new feature uncovered in the present 3D simulation is that the process of reconnection produces flux ropes developing within the reconnection region. These flux ropes are unstable to the kink mode and introduce a spontaneous structure in the dawn-dusk direction. The dipolarization fronts forming downstream of reconnection are strongly affected by the kinking ropes. At the fronts, a density gradient is present with opposite direction to that of the acceleration field and leads to an interchange instability. We present evidence for a causal link where the perturbations of the kinking flux ropes with their natural and well defined scales drive and select the scales for the interchange mode in the dipolarization fronts. The results of the simulation are validated against measured structures observed by the Themis mission.
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