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arXiv 1303.1371astro-ph.SR
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日冕加热的参数化:空间分布和可观测的结果

Parametrization of coronal heating: spatial distribution and observable consequences

T. van Wettum, S. Bingert, H. Peter

摘要:

我们调查的能量输入的空间分布的差异参数化的不同机制来加热日冕的太阳和日冕发射的可能影响。我们使用一个三维MHD模型的太阳活动区作为参考,并比较欧姆型加热在这个模型中的参数化的交流(AC)和直流(DC)加热模型,特别是,我们使用阿尔芬波和MHD湍流加热。我们从参考模型中提取这两个参数化所需的量,并研究在所有三种情况下,全球和沿个别场线的热输入的空间分布。为了研究由此产生的日冕发射的差异,我们采用了1D环路模型与规定的热输入的基础上,我们提取沿一束场线的加热速率。平均而言,所有加热实施方式显示加热速率随高度大致下降。这也适用于单个场线。虽然所有的机制都显示出对大气低部分的能量输入的集中,但对于单个场线,DC机制对足点的集中比Alfven波AC情况强得多。相比之下,AC模型给出了朝向足点的更强的排放浓度。这是因为能量输入的更均匀分布导致更高的日冕温度和更扩展的过渡区。对于AC和DC机制,朝向足点的热输入的浓度的显著差异,以及对于这些情况,日冕发射的空间分布的指向差异表明,这两种机制应该通过观测来区分。在得出最终结论之前,这些参数化应该以更加自洽的方式在新的3D模型中实现。

英文摘要:

We investigate the difference in the spatial distribution of the energy input for parametrizations of different mechanisms to heat the corona of the Sun and possible impacts on the coronal emission. We use a 3D MHD model of a solar active region as a reference and compare the Ohmic-type heating in this model to parametrizations for alternating current (AC) and direct current (DC) heating models, in particular, we use Alfven wave and MHD turbulence heating. We extract the quantities needed for these two parametrizations from the reference model and investigate the spatial distribution of the heat input in all three cases, globally and along individual field lines. To study differences in the resulting coronal emission we employ 1D loop models with a prescribed heat input based on the heating rate we extracted along a bundle of field lines. On average, all heating implementations show a roughly drop of the heating rate with height. This also holds for individual field lines. While all mechanism show a concentration of the energy input towards the low parts of the atmosphere, for individual field lines the concentration towards the footpoints is much stronger for the DC mechanisms than for the Alfven wave AC case. In contrast, the AC model gives a stronger concentration of the emission towards the footpoints. This is because the more homogeneous distribution of the energy input leads to higher coronal temperatures and a more extended transition region. The significant difference in the concentration of the heat input towards the foot points for the AC and DC mechanisms, and the pointed difference in the spatial distribution of the coronal emission for these cases shows that the two mechanisms should be discriminable by observations. Before drawing final conclusions, these parametrizations should be implemented in new 3D models in a more self-consistent way.

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