Twisted versus braided magnetic flux ropes in coronal geometry II. Comparative behaviour
Twisted versus braided magnetic flux ropes in coronal geometry II. Comparative behaviour
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冠状几何结构中的扭曲与编织磁通绳 II。
DOI：
10.1051/0004-6361/201528053
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发表时间：
2016
影响因子：
6.5
通讯作者：
Prior C
中科院分区：
文献类型：
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作者：
Prior C
我们介绍了一种产生具有任意轴向几何形状和内部拓扑的管状磁场的技术。作为初步应用，该技术用于构造两个具有相同 S 形管状形状但具有不同内部结构的磁通绳。一种是扭曲的，另一种具有更复杂的编织磁场。磁通绳嵌入在四极线性无力背景中的光球中性线上方。使用电阻磁流体动力学模拟，我们表明两个场都可以松弛到稳定的无力平衡，同时保持其管状结构。两个最终状态都是非线性无力的；扭曲场包含单个α符号（无力参数），表明扭曲磁绳具有单一主导手性；编织场包含两个符号α，表明内部扭曲同时具有正手性和负手性的磁绳。这些最终状态下的电流结构在具有扩散结构的编织场和显示出清晰的 S 形曲线的扭曲场之间存在显着差异。这种差异可能是可以观察到的。
We introduce a technique for generating tubular magnetic fields with arbitrary axial geometry and internal topology. As an initial application, this technique is used to construct two magnetic flux ropes that have the same sigmoidal tubular shape, but have different internal structures. One is twisted, the other has a more complex braided magnetic field. The flux ropes are embedded above the photospheric neutral line in a quadrupolar linear force-free background. Using resistive-magnetohydrodynamic simulations, we show that both fields can relax to stable force-free equilibria whilst maintaining their tubular structure. Both end states are nonlinear force-free; the twisted field contains a single sign of alpha (the force-free parameter), indicating a twisted flux rope of a single dominant chirality, the braided field contains both signs of alpha, indicating a flux rope whose internal twisting has both positive and negative chirality. The electric current structures in these final states differ significantly between the braided field, which has a diffuse structure, and the twisted field, which displays a clear sigmoid. This difference might be observable.