Magnetic reconnection is an important process in astrophysical environments, as it reconfigures magnetic field topology and converts magnetic energy into thermal and kinetic energy. In extreme astrophysical systems, such as black hole coronae and pulsar magnetospheres, radiative cooling modifies the energy partition by radiating away internal energy, which can lead to the radiative collapse of the reconnection layer. In this paper, we perform two- and three-dimensional simulations to model the MARZ (Magnetic Reconnection on Z) experiments, which are designed to access cooling rates in the laboratory necessary to investigate reconnection in a previously unexplored radiatively cooled regime. These simulations are performed in GORGON, an Eulerian two-temperature resistive magnetohydrodynamic code, which models the experimental geometry comprising two exploding wire arrays driven by 20 MA of current on the Z machine (Sandia National Laboratories). Radiative losses are implemented using non-local thermodynamic equilibrium tables computed using the atomic code Spk, and we probe the effects of radiation transport by implementing both a local radiation loss model and $P_{1/3}$ multi-group radiation transport. The load produces highly collisional, super-Alfvénic (Alfvén Mach number $M_A \approx 1.5$ ), supersonic (Sonic Mach number $M_S \approx 4-5$ ) strongly driven plasma flows which generate an elongated reconnection layer (Aspect Ratio $L/\delta \approx 100$ , Lundquist number $S_L \approx 400$ ). The reconnection layer undergoes radiative collapse when the radiative losses exceed the rates of ohmic and compressional heating (cooling rate/hydrodynamic transit rate = $\tau _{\text {cool}}^{-1}/\tau _{H}^{-1}\approx 100$ ); this generates a cold strongly compressed current sheet, leading to an accelerated reconnection rate, consistent with theoretical predictions. Finally, the current sheet is also unstable to the plasmoid instability, but the magnetic islands are extinguished by strong radiative cooling before ejection from the layer.

中文翻译：

---

脉冲功率驱动的辐射冷却磁重联仿真

磁重联是天体物理环境中的一个重要过程，因为它重新配置磁场拓扑并将磁能转化为热能和动能。在黑洞日冕和脉冲星磁层等极端天体物理系统中，辐射冷却通过辐射内部能量来改变能量分配，这可能导致重联层的辐射塌陷。在本文中，我们进行二维和三维模拟来模拟 MARZ（Z 上磁重联）实验，这些实验旨在获得实验室中研究先前未探索的辐射冷却状态中的重联所需的冷却速率。这些模拟是在 GORGON 中进行的，GORGON 是一种欧拉双温电阻磁流体动力学代码，它对实验几何结构进行建模，该几何结构包括由 Z 机器（桑迪亚国家实验室）上 20 MA 电流驱动的两个爆炸线阵列。辐射损失是使用原子代码 Spk 计算的非局部热力学平衡表来实现的，我们通过实现局部辐射损失模型和 $P_{1/3}$ 多组辐射传输。负载产生高度碰撞、超阿尔夫文（阿尔夫文马赫数） $M_A \约1.5$ ）、超音速（音速马赫数 $M_S \约4-5$ ）强烈驱动的等离子体流，产生细长的重新连接层（纵横比 $L/\delta \约 100$ , 伦德奎斯特数 $S_L \约400$ ）。当辐射损失超过欧姆和压缩加热速率（冷却速率/流体动力传输速率 = $\tau _{\text {酷}}^{-1}/\tau _{H}^{-1}\约100$ ）；这会产生冷的、强烈压缩的电流片，从而导致重新连接率加快，这与理论预测一致。最后，电流片对于等离子体不稳定也不稳定，但是磁岛在从层中喷射之前被强辐射冷却所消灭。