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 $\simeq 0.2$, consistent with the theoretical prediction.

中文翻译：

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二维磁流体动力学中电阻率梯度引起的快速磁重联

使用二维 (2D) 磁流体动力学模拟，我们表明可以在重联流出方向使用简单的电阻率梯度诱导 Petschek 型磁重联，揭示碰撞极限中稳定快速重联的关键因素。我们发现扩散区会自行调整其半长以适应给定的电阻率梯度尺度。诱导重连 x 线和流动停滞点始终位于靠近较高电阻率端的电阻率过渡区域内。通过这种电阻率梯度打开一个排气口将导致位于 x 线另一侧、在均匀电阻率区域内的另一个排气口的开口。讨论了这种设置对基于重新连接的推进器和太阳能针状体的潜在应用。在一组单独的数值实验中，我们使用位于 x 线的大且空间局部电阻率来探索最大似是而非的重联率。有趣的是，在 x 线上产生的电流密度显着下降，因此归一化的重新连接率仍然受该值的限制$\simeq 0.2$，与理论预测一致。