Estimating the Rate of Field Line Braiding in the Solar Corona by Photospheric Flows
Estimating the Rate of Field Line Braiding in the Solar Corona by Photospheric Flows
复制标题
DOI：
10.3847/1538-4357/aad8bc
复制
发表时间：
2018-09-10
影响因子：
4.9
通讯作者：
Hornig, G.
中科院分区：
文献类型：
--
作者：
Candelaresi, S.;Pontin, D., I;Hornig, G.
在本文中，我们试图了解的时间尺度，其中光球运动的太阳编织日冕磁场线。这是决定编织机制可行性的关键因素，可以解释日冕中观察到的高温。我们研究的拓扑结构的复杂性引起的日冕磁场，主要是使用等离子体运动提取的磁对流模拟。这种拓扑的复杂性量化使用场线绕组，有限时间拓扑熵（FTTE），和被动标量混合。有了这些措施，我们对比混合效率的磁对流模拟，一个基准流被称为“闪烁的漩涡”，最后光球流推断从序列中观察到的磁图使用本地相关跟踪。虽然高分辨率的磁对流模拟引起了强烈程度的场线绕组和FTTE，从斑区的观测获得的值是一个数量级左右的小。这种行为会延续到FTTE。然而，结果表明，光球运动引起复杂的纠缠的日冕场的时间尺度上的小时。
In this paper, we seek to understand the timescale in which the photospheric motions on the Sun braid coronal magnetic field lines. This is a crucial ingredient for determining the viability of the braiding mechanism for explaining the high temperatures observed in the corona. We study the topological complexity induced in the coronal magnetic field, primarily using plasma motions extracted from magneto-convection simulations. This topological complexity is quantified using the field line winding, finite time topological entropy (FTTE), and passive scalar mixing. With these measures, we contrast mixing efficiencies of the magneto-convection simulation, a benchmark flow known as a "blinking vortex", and finally photospheric flows inferred from sequences of observed magnetograms using local correlation tracking. While the highly resolved magneto-convection simulations induce a strong degree of field line winding and FTTE, the values obtained from the observations from the plage region are around an order of magnitude smaller. This behavior is carried over to the FTTE. Nevertheless, the results suggest that the photospheric motions induce complex tangling of the coronal field on a timescale of hours.