NUMERICAL SIMULATIONS OF CORONAL HEATING THROUGH FOOTPOINT BRAIDING

NUMERICAL SIMULATIONS OF CORONAL HEATING THROUGH FOOTPOINT BRAIDING
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通过足点编织进行日冕加热的数值模拟

DOI：
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发表时间：
2015
期刊：
影响因子：
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通讯作者：
M. Carlsson
M. Carlsson
中科院分区：
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文献类型：
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作者：
V. Hansteen;N. Guerreiro;B. Pontieu;M. Carlsson

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先进的三维（3D）辐射MHD模拟现在再现了太阳外层大气的许多特性。当包括从对流区到日冕的一个域时，热色球和日冕是自我一致地维持的。本文研究了两种具有不同模拟面积、磁场强度和拓扑结构以及数值分辨率的现实模型。将这些进行比较，以便在3D-MHD模拟中表征加热，该模拟自一致地维持大气结构。我们分析了大尺度和小尺度的加热，发现加热在空间上是偶发的和高度结构化的，但沿着环形结构发生，并随着磁场移动。在大尺度上，我们发现在过渡区附近每粒子的加热最大，光球中广泛分布的相反极性场导致日冕中更高的加热尺度高度。在较小的尺度上，加热集中在电流片上，电流片的厚度由数值分辨率决定。一些电流片在时间上断裂，这一过程在高分辨率模型中更容易发生，导致空间上高度间歇性的加热。大尺度的加热结构在不到五分钟的时间内消失，而较小的局部加热在一个模型中显示出两分钟的时间尺度，在另一个更高分辨率的模型中显示出一分钟的时间尺度。
Advanced three-dimensional (3D) radiative MHD simulations now reproduce many properties of the outer solar atmosphere. When including a domain from the convection zone into the corona, a hot chromosphere and corona are self-consistently maintained. Here we study two realistic models, with different simulated areas, magnetic field strength and topology, and numerical resolution. These are compared in order to characterize the heating in the 3D-MHD simulations which self-consistently maintains the structure of the atmosphere. We analyze the heating at both large and small scales and find that heating is episodic and highly structured in space, but occurs along loop-shaped structures, and moves along with the magnetic field. On large scales we find that the heating per particle is maximal near the transition region and that widely distributed opposite-polarity field in the photosphere leads to a greater heating scale height in the corona. On smaller scales, heating is concentrated in current sheets, the thicknesses of which are set by the numerical resolution. Some current sheets fragment in time, this process occurring more readily in the higher-resolution model leading to spatially highly intermittent heating. The large-scale heating structures are found to fade in less than about five minutes, while the smaller, local, heating shows timescales of the order of two minutes in one model and one minutes in the other, higher-resolution, model.