RUI: Multi-wavelength Spectroscopic and Spectropolarimetric Diagnostics of the Solar Atmosphere

这个为期3年的项目旨在发展数据分析技术，通过同时对不同高度形成的光谱线进行多波长观测，推断从光球到约2-5毫米高度的太阳大气的热力学和磁场结构。许多目前的分析方法只能得到简化的结果，而不能得到物理性质的分层。该项目将开发一种自动的半经验方法，将这种较低复杂性的结果转换为大气分层，无论这些结果不能直接从光谱反演中得到。该方法将在太阳黑子的观测中进行测试，在那里，磁场拓扑结构、连通性和气体密度的附加约束可以从组织良好的空间结构和磁场外推中获得。这些结果将使人们能够解决目前几乎所有与太阳低层大气有关的悬而未决的问题，例如，了解太阳黑子内部从光球层深处到色球层的质量流和振荡的精细结构和特性。这将增加我们对太阳黑子基本特性的理解，太阳黑子是天体物理学中最神秘的物体之一。太阳黑子是晚型恒星的一个组成部分，在恒星演化中发挥着至关重要的作用，并可以通过植根于太阳黑子及其活动区域的空间天气事件影响包括地球在内的支持生命的系外行星。推断太阳大气热力学和磁结构的方法将基于对不同光球和色球光谱线的分段分析，并使用已有的反演代码和项目期间开发的附加工具。对于目前的分析方法不能提供太阳大气物理参数分层的任何谱线，例如，在656nm处中性氢α的显色球谱线，将采用一种利用磁场外推的外部约束的半经验方法，将从简化的辐射传输模型中获得的结果转换为分层。一项主要工作将是始终如一地将来自不同高度的分层转换和组合成太阳大气中从0到约5毫米的所有相关热力学和磁参数的单一大气分层。所得到的大气模式预计将处于流体静力平衡状态，在几何高度尺度上提供所有物理参数，并在对模式大气进行光谱合成时再现所有观测到的光谱线。由于磁场拓扑结构的空间连续性，该方法在太阳黑子观测上的可靠性得到了成功的证明，这将使人们能够决定它是否适合于任意太阳目标的观测。任何需要精确的太阳低层大气物理特性的科学问题都可以用分析方法的结果来解决。通过该项目开发的工具将免费提供给太阳研究人员社区，并将有助于充分利用NSF的4米级Daniel K. Inouye太阳望远镜的观测结果。加州州立大学北岭分校未被充分代表的学生参与分析和可视化高分辨率光谱偏振数据，将为未来一代太阳物理学的科学工作者做好准备。该项目的研究和EPO议程支持AGS部门在发现、学习、多样性和跨学科研究方面的战略目标。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This 3-year project aims to develop data analysis techniques to infer the thermodynamic and magnetic structure of the solar atmosphere from the photosphere to a height of about 2-5 Mm using simultaneous multi-wavelength observations of spectral lines formed at different heights. Many current analysis approaches yield only simplified results instead of stratifications of physical properties. The project will develop an automatic, semi-empirical method to convert such results of lower complexity to atmospheric stratifications wherever they cannot be directly derived from an inversion of spectra. The method will be tested on observations of sunspots, where additional constraints on the magnetic field topology, connectivity and the gas density are available from the well-organized spatial structuring and magnetic field extrapolations. The results will enable one to address nearly all currently open questions in relation to the lower solar atmosphere, e.g., understanding the fine-structure and the properties of mass flows and oscillations inside sunspots from deep in the photosphere to the chromosphere. This will add to our understanding of the basic properties of sunspots, which are some of the most enigmatic objects in astrophysics. Sunspots are an integral part of late-type stars, play a vital role in stellar evolution and can influence life-supporting exoplanets including the Earth through space weather events that are rooted in sunspots and the active regions that host them. The method to infer the thermodynamic and magnetic structure of the solar atmosphere will be based on a piece-wise analysis of different photospheric and chromospheric spectral lines with already available inversion codes and the additional tools developed during the project. For any spectral line where current analysis methods do not provide stratifications of physical parameters of the solar atmosphere, e.g., the prominent chromospheric spectral line of neutral Hydrogen Alpha at 656 nm, a semi-empirical method using external constraints from magnetic field extrapolations will be employed to convert the results retrieved from a simplified modeling of the radiative transfer to stratifications. A major effort will be to consistently convert and combine the stratifications from different height regimes into a single atmospheric stratification of all relevant thermodynamic and magnetic parameters from 0 to about 5 Mm in the solar atmosphere. The resulting atmospheric model is expected to be in hydrostatic equilibrium, to provide all physical parameters on a geometrical height scale and to reproduce all observed spectral lines when a spectral synthesis of the model atmosphere is executed. A successful demonstration of the reliability of the approach on sunspot observations, where additional constraints are available because of the spatial continuity of the magnetic field topology, will allow one to decide on its suitability for observations of arbitrary solar targets. Any scientific question that requires accurate physical properties of the lower solar atmosphere can potentially be addressed with the results of the analysis approach. The tool developed through this project will be freely available to the community of solar researchers and will help in fully exploiting the observations with the NSF’s 4-meter class Daniel K. Inouye Solar Telescope. The participation of underrepresented students at California State University Northridge to both analyze and visualize the high-resolution spectropolarimetric data will prepare a future generation of the scientific workforce in solar physics. The research and EPO agenda of this project supports the Strategic Goals of the AGS Division in discovery, learning, diversity, and interdisciplinary research.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.