磁零点附近的内爆坍缩：二维和三维磁零点的定量比较
Implosive collapse about magnetic null points: A quantitative comparison between 2D and 3D nulls
摘要：
磁流体坍缩是一种内爆过程，其中MHD波将其能量集中在零点附近，形成电流片并引发磁重联。我们认为，第一次，崩溃的情况下，三维磁零点在非线性，电阻MHD使用数值模拟，探索系统的关键物理方面，以及进行详细的参数研究。我们发现，在一个特定的平面内包含的3D零，等离子体和电流密度的增强所造成的崩溃是定量和定性的每2D的情况下，在线性和非线性崩溃制度。然而，缩放与电阻率的3D重联率-这是一个全球性的量-被发现是不太有利的磁零点是更旋转对称时，由于增加的磁背压的作用。此外，我们发现，随着周围的等离子体压力的增加，崩溃可以节流，是二维零的情况下。我们讨论了这种压力限制的背景下，在太阳大气中的快速重联，并提出了机制，它可以被克服。我们还讨论了零崩溃的背景下，振荡重联，时间相关的重联机制的触发机制的结果的影响，也在更广泛的主题波零点相互作用。我们的结论是，在一般情况下，越来越多的旋转非对称零将是更有利的磁能释放通过零崩溃比他们更对称的同行。
英文摘要：
Null collapse is an implosive process whereby MHD waves focus their energy in the vicinity of a null point, forming a current sheet and initiating magnetic reconnection. We consider, for the first time, the case of collapsing 3D magnetic null points in nonlinear, resistive MHD using numerical simulation, exploring key physical aspects of the system as well as performing a detailed parameter study. We find that within a particular plane containing the 3D null, the plasma and current density enhancements resulting from the collapse are quantitatively and qualitatively as per the 2D case in both the linear and nonlinear collapse regimes. However, the scaling with resistivity of the 3D reconnection rate - which is a global quantity - is found to be less favourable when the magnetic null point is more rotationally symmetric, due to the action of increased magnetic back-pressure. Furthermore, we find that with increasing ambient plasma pressure the collapse can be throttled, as is the case for 2D nulls. We discuss this pressure-limiting in the context of fast reconnection in the solar atmosphere and suggest mechanisms by which it may be overcome. We also discuss the implications of the results in the context of null collapse as a trigger mechanism of Oscillatory Reconnection, a time-dependent reconnection mechanism, and also within the wider subject of wave-null point interactions. We conclude that, in general, increasingly rotationally-asymmetric nulls will be more favourable in terms of magnetic energy release via null collapse than their more symmetric counterparts.
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