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arXiv 1001.3022astro-ph.SR
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可见谱线偏振光谱测量

On spectropolarimetric measurements with visible lines

J. C. del Toro Iniesta, D. Orozco Suárez, L. R. Bellot Rubio

摘要:

新仪器提供矢量磁场和太阳等离子体视线速度的精确推断的能力,在很大程度上取决于所选测量的谱线对这些物理量的灵敏度。最近,人们对可见的斯托克斯轮廓提出了质疑,以提供一个明确的区分弱场和强场填充一小部分的观察区域。本文的目标是提供定性和定量的论据,帮助解决这一争论,因为几个采用可见线条的工具正在运作或计划在不久的将来。斯托克斯分布的灵敏度是通过响应函数计算的(例如,Ruiz Cobo & Del Toro Mesesta,1994年)。理论和经验证据收集有利于可见斯托克斯轮廓的可靠性。响应函数也用于估计观测中噪声引起的物理量的不确定性。一个有用的公式已被推导出来,考虑到测量技术(偏振测量,偏振效率,波长样品的数量),模型假设(自由参数的数量,填充因子),和辐射转移(响应函数)。我们的结论是,一个弱磁场的情况下,可以合理地区分与另一个强场,但类似的斯托克斯$V$振幅可见线,只要米尔恩-爱丁顿近似是足够好的描述太阳大气和偏振信号是至少三或四倍大于典型的均方根噪声的$ 10^{-3} I_{\rm c}$达到的观测。

英文摘要:

The ability of new instruments for providing accurate inferences of vector magnetic fields and line-of-sight velocities of the solar plasma depends a great deal on the sensitivity to these physical quantities of the spectral lines chosen to be measured. Recently, doubts have been raised about visible Stokes profiles to provide a clear distinction between weak fields and strong ones filling a small fraction of the observed area. The goal of this paper is to give qualitative and quantitative arguments that help in settling the debate since several instruments that employ visible lines are either operating or planned for the near future. The sensitivity of the Stokes profiles is calculated through the response functions (e.g. Ruiz Cobo & Del Toro Iniesta, 1994). Both theoretical and empirical evidences are gathered in favor of the reliability of visible Stokes profiles. The response functions are used as well for estimating the uncertainties in the physical quantities due to noise in the observations. A useful formula has been derived that takes into account the measurement technique (number of polarization measurements, polarimetric efficiencies, number of wavelength samples), the model assumptions (number of free parameters, the filling factor), and the radiative transfer (response functions). We conclude that a scenario with a weak magnetic field can reasonably be distinguished with visible lines from another with a strong field but a similar Stokes $V$ amplitude, provided that the Milne-Eddington approximation is good enough to describe the solar atmosphere and that the polarization signal is at least three or four times larger than the typical rms noise of $ 10^{-3} I_{\rm c}$ reached in the observations.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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