Fast magnetic reconnection induced by resistivity gradients in 2D magnetohydrodynamics
Fast magnetic reconnection induced by resistivity gradients in 2D magnetohydrodynamics
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DOI：
10.1063/5.0052317
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发表时间：
2021-07
影响因子：
2.2
通讯作者：
Shan-Chang Lin;Yi‐Hsin Liu;Xiaocan Li
中科院分区：
文献类型：
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作者：
Shan-Chang Lin;Yi‐Hsin Liu;Xiaocan Li
使用二维（2D）磁流体动力学模拟，我们表明，Petschek型磁重联可以诱导使用一个简单的电阻率梯度在重联流出方向，揭示了稳定的快速重联在碰撞极限的关键成分。我们发现，扩散区自我调整其半长，以适应给定的电阻率梯度规模。感应重联x线和流动停滞点总是位于电阻率过渡区内，更靠近高电阻率端。通过该电阻率梯度打开一个排气装置将导致位于x线另一侧的另一排气装置在均匀电阻率区域内打开。讨论了这种设置在基于重连的推进器和太阳针状体中的潜在应用。在一组单独的数值实验中，我们探索了最大的合理重连率使用一个大的和空间局部的电阻率的权利，在x线。有趣的是，在x线处产生的电流密度显著下降，使得归一化的重连率保持由值<0.2限制，与理论预测一致。
Using two-dimensional (2D) magnetohydrodynamics simulations, we show that Petschek-type magnetic reconnection can be induced using a simple resistivity gradient in the reconnection outflow direction, revealing the key ingredient of steady fast reconnection in the collisional limit. We find that the diffusion region self-adjusts its half-length to fit the given gradient scale of resistivity. The induced reconnection x-line and flow stagnation point always reside within the resistivity transition region closer to the higher resistivity end. The opening of one exhaust by this resistivity gradient will lead to the opening of the other exhaust located on the other side of the x-line, within the region of uniform resistivity. Potential applications of this setup to reconnection-based thrusters and solar spicules are discussed. In a separate set of numerical experiments, we explore the maximum plausible reconnection rate using a large and spatially localized resistivity right at the x-line. Interestingly, the resulting current density at the x-line drops significantly so that the normalized reconnection rate remains bounded by the value ≃ 0.2, consistent with the theoretical prediction.