arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2001.06123astro-ph.SRphysics.app-ph
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利用禁戒发射线的多线分光偏振观测测量单点日冕磁场

Using multi-line spectropolarimetric observations of forbidden emission lines to measure single-point coronal magnetic fields

Gabriel I. Dima, Thomas A. Schad

摘要:

极化磁偶极(M1)发射线为主导日冕演化的磁场提供了重要的诊断。本文提出了一种多线技术,使用特定的M1线的组合来推断全矢量磁场的光学薄发射,可以定位在一个给定的视线区域。我们的分析形式主义是一个推广的“单点反演”的方法介绍了普洛曼。我们发现,M1过渡的组合,其中每个是一个$J=1\rightarrow0$过渡或具有相等的Landé g因子的上,下水平包含退化的光谱偏振信息,禁止应用的单点反演技术。这可能包括Plowman讨论的一对红外Fe XIII线。我们将Fe XIII 1074.7 nm和Si X 1430.1 nm线确定为实施该技术的一种替代组合。我们的灵敏度分析,基于日冕环的性质,表明,对于光子噪声水平周围的$10^{-4}$的线强度,这将是可以实现的国家科学基金会的丹尼尔K。在Inouye太阳望远镜中,用这种方法可以恢复足够强度(${\sim}10$ G)且不严重倾斜于视线($\lesssim 35^{\circ}$)的磁场。退化的解决方案是存在的;但是,我们讨论如何添加约束可能有助于解决它们或减少它们的数量。

英文摘要:

Polarized magnetic dipole (M1) emission lines provide important diagnostics for the magnetic field dominating the evolution of the solar corona. This paper advances a multi-line technique using specific combinations of M1 lines to infer the full vector magnetic field for regions of optically thin emission that can be localized along a given line of sight. Our analytical formalism is a generalization of the "single-point inversion" approach introduced by Plowman. We show that combinations of M1 transitions for which each is either a $J=1\rightarrow0$ transition or has equal Landé g-factors for the upper and lower levels contain degenerate spectropolarimetric information that prohibits the application of the single-point inversion technique. This may include the pair of infrared Fe XIII lines discussed by Plowman. We identify the Fe XIII 1074.7 nm and Si X 1430.1 nm lines as one alternative combination for implementing this technique. Our sensitivity analysis, based on coronal loop properties, suggests that for photon noise levels around $10^{-4}$ of the line intensity, which will be achievable with the National Science Foundation's Daniel K. Inouye Solar Telescope, magnetic fields with sufficient strength (${\sim}10$ G) and not severely inclined to the line-of-sight ($\lesssim 35^{\circ}$) can be recovered with this method. Degenerate solutions exist; though, we discuss how added constraints may help resolve them or reduce their number.

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