标题： 三维磁重联扩展的标度理论 显示英文标题

标题： Scaling Theory of 3D Magnetic Reconnection Spreading

摘要： 我们开发了一种基于第一性原理的尺度理论，用于描述在平面外方向具有有限范围的三维（3D）磁重联的扩展。该理论适用于存在或不存在平面外（引导）磁场的系统，以及是否存在霍尔物理效应的系统。该理论再现了有无引导磁场时已知的扩展速度和方向，在单一理论中统一了先前的知识。新结果包括：（1）如果在重联区域和非重联区域之间的界面上诱导出x线，则重联会在特定方向上扩展，这由流出方向的电场平面外梯度控制。（2）对于反平行无碰撞重联，扩展机制是对流，这是已知的，但对于引导磁场重联，其机制是磁场弯曲。我们通过三维双流体和电阻磁流体动力学模拟验证了该理论。（3）该理论解释了为什么电阻磁流体动力学中的反平行重联不会扩展。（4）模拟区域的长宽比，与自由磁能相关，会影响在固定x线长度下重联是扩展还是对流。（5）我们进行了一项模拟，使用压力脉冲而非磁场扰动来启动反平行无碰撞重联，发现扩展情况不变，而不是如之前所建议的以磁声速扩展。这些结果提供了一个理论框架，用于理解在此处研究的系统之外的扩展，并在包括双带太阳耀斑和地球磁层中的重联等应用中非常重要。 显示英文摘要

摘要： We develop a first-principles scaling theory of the spreading of three-dimensional (3D) magnetic reconnection of finite extent in the out of plane direction. This theory addresses systems with or without an out of plane (guide) magnetic field, and with or without Hall physics. The theory reproduces known spreading speeds and directions with and without guide fields, unifying previous knowledge in a single theory. New results include: (1) Reconnection spreads in a particular direction if an x-line is induced at the interface between reconnecting and non-reconnecting regions, which is controlled by the out of plane gradient of the electric field in the outflow direction. (2) The spreading mechanism for anti-parallel collisionless reconnection is convection, as is known, but for guide field reconnection it is magnetic field bending. We confirm the theory using 3D two-fluid and resistive-magnetohydrodynamics simulations. (3) The theory explains why anti-parallel reconnection in resistive-magnetohydrodynamics does not spread. (4) The simulation domain aspect ratio, associated with the free magnetic energy, influences whether reconnection spreads or convects with a fixed x-line length. (5) We perform a simulation initiating anti-parallel collisionless reconnection with a pressure pulse instead of a magnetic perturbation, finding spreading is unchanged rather than spreading at the magnetosonic speed as previously suggested. The results provide a theoretical framework for understanding spreading beyond systems studied here, and are important for applications including two-ribbon solar flares and reconnection in Earth's magnetosphere.