arXiv 2106.077862021-06-16astro-ph.SR

测量太阳耀斑、日冕物质抛射和空间天气的磁源

Measuring the magnetic origins of solar flares, CMEs and Space Weather

Philip Judge, Matthias Rempel, Rana Ezzeddine, Lucia Kleint, Ricky Egeland, Svetlana Berdyugina, Thomas Berger, Joan Burkepile, Rebecca Centeno, Giuliana de Tom… 展开作者

Philip Judge, Matthias Rempel, Rana Ezzeddine, Lucia Kleint, Ricky Egeland, Svetlana Berdyugina, Thomas Berger, Joan Burkepile, Rebecca Centeno, Giuliana de Toma, Mausumi Dikpati, Yuhong Fan, Holly Gilbert, Daniela Lacatus

备注：: Accepted in ApJ, V2 fixed author spelling error
DOI：: 10.3847/1538-4357/ac081f

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摘要：

我们采取广泛的问题，确定磁太阳的原因空间天气。与乏善可陈的表现外推磁场测量的基础上在光球，我们确定了一个区域在近紫外光谱的一部分作为最佳的研究活动区域的磁自由能的发展。使用SORCE，哈勃太空望远镜和SKYLAB的数据，以及近紫外（NUV）光谱的一维计算和基于MURaM辐射MHD和HanleRT辐射转移代码的数值实验，我们解决了多个挑战。这些挑战最好通过明亮的\ion{Mg}{2}的近紫外线以及在色球层中形成高达$2\times10^4$ K的\ion{Fe}{2}和\ion{Fe}{1}的线（主要在$4s-4p$过渡阵列内）的组合来满足。汉勒效应和塞曼效应原则上都可以用来导出矢量磁场。然而，对于任何给定的谱线，由于诸如原纤维和针状物的精细结构，$τ=1$表面通常是几何波纹状的。通过使用跨越不同光学深度的多个谱线，可以在低等离子体$β$区域中推断出穿过接近水平表面的磁场，由此可以导出自由能、磁拓扑和其他量。基于最近报道的成功的亚轨道空间磁场测量CLASP2仪器，我们认为，一个温和的星载望远镜将能够在预测太阳爆发的尝试取得重大进展。附录中显示，与混合线相关的困难很小。

英文摘要：

We take a broad look at the problem of identifying the magnetic solar causes of space weather. With the lackluster performance of extrapolations based upon magnetic field measurements in the photosphere, we identify a region in the near UV part of the spectrum as optimal for studying the development of magnetic free energy over active regions. Using data from SORCE, Hubble Space Telescope, and SKYLAB, along with 1D computations of the near-UV (NUV) spectrum and numerical experiments based on the MURaM radiation-MHD and HanleRT radiative transfer codes, we address multiple challenges. These challenges are best met through a combination of near UV lines of bright \ion{Mg}{2}, and lines of \ion{Fe}{2} and \ion{Fe}{1} (mostly within the $4s-4p$ transition array) which form in the chromosphere up to $2\times10^4$ K. Both Hanle and Zeeman effects can in principle be used to derive vector magnetic fields. However, for any given spectral line the $τ=1$ surfaces are generally geometrically corrugated owing to fine structure such as fibrils and spicules. By using multiple spectral lines spanning different optical depths, magnetic fields across nearly-horizontal surfaces can be inferred in regions of low plasma $β$, from which free energies, magnetic topology and other quantities can be derived. Based upon the recently-reported successful suborbital space measurements of magnetic fields with the CLASP2 instrument, we argue that a modest space-borne telescope will be able to make significant advances in the attempts to predict solar eruptions. Difficulties associated with blended lines are shown to be minor in an Appendix.

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