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arXiv 1006.0231astro-ph.SRastro-ph.GA
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通过三维磁对流模拟导出的太阳丰度修正

Solar abundance corrections derived through 3D magnetoconvection simulations

D. Fabbian, E. Khomenko, F. Moreno-Insertis, Å. Nordlund

摘要:

我们探讨的效果时,使用现实的三维对流实验,以确定太阳元素丰度的磁场。通过进行磁对流模拟与辐射水代码(哥本哈根交错代码),并通过后验谱合成的三个Fe I线,我们得到的证据表明,中等量的平均磁通量导致显着的变化,推导出的等效宽度相比,那些为非磁性的情况下。相应的Fe丰度校正的平均通量密度为200 G达到~0.1德克斯的数量级。这些结果的基础上的空间和时间平均线的轮廓在2.5个太阳小时的时间跨度在统计稳定的对流制度。引起等效宽度变化的主要因素,即塞曼加宽和温度分层的改变,以不同的量起作用,并且对于这里考虑的铁谱线,以相反的方向起作用;然而,所得到的$|Δ\logε_{\odot}(Fe)|$在所有铁谱线中都在因子2内一致,尽管可见谱线和红外谱线的总丰度校正的符号不同。我们的结论是,在讨论太阳和恒星丰度的精确值时,应考虑到磁效应,并有必要进行深入的研究。

英文摘要:

We explore the effect of the magnetic field when using realistic three-dimensional convection experiments to determine solar element abundances. By carrying out magnetoconvection simulations with a radiation-hydro code (the Copenhagen stagger code) and through a-posteriori spectral synthesis of three Fe I lines, we obtain evidence that moderate amounts of mean magnetic flux cause a noticeable change in the derived equivalent widths compared with those for a non-magnetic case. The corresponding Fe abundance correction for a mean flux density of 200 G reaches up to ~0.1 dex in magnitude. These results are based on space- and time-averaged line profiles over a time span of 2.5 solar hours in the statistically stationary regime of the convection. The main factors causing the change in equivalent widths, namely the Zeeman broadening and the modification of the temperature stratification, act in different amounts and, for the iron lines considered here, in opposite directions; yet, the resulting $|Δ\logε_{\odot}(Fe)|$ coincides within a factor two in all of them, even though the sign of the total abundance correction is different for the visible and infrared lines. We conclude that magnetic effects should be taken into account when discussing precise values of the solar and stellar abundances and that an extended study is warranted.

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