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arXiv 2009.01537astro-ph.SR
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受限X2 .2耀斑的非LTE反转:I.光球层和色球层中的矢量磁场

Non-LTE inversions of a confined X2.2 flare: I. Vector magnetic field in the photosphere and chromosphere

G. J. M. Vissers, S. Danilovic, J. de la Cruz Rodriguez, J. Leenaarts, R. Morosin, C. J. Diaz Baso, A. Reid, J. Pomoell, D. J. Price, S. Inoue

摘要:

准确获得太阳大气中的磁场矢量对于研究耀斑期间磁场拓扑结构的变化和可靠地模拟空间天气至关重要。我们通过将各种反演方法应用于2017年9月6日NOAA AR 12673中的受限X2.2耀斑来解决这个问题,将光球和色球磁场矢量与该事件的两个数值模型进行比较。我们从Milne-Eddington(ME)和(非)局部热平衡(非LTE)反演的Hinode SOT/SP Fe I 6301.5 μ m和6302.5 μ m得到光球场。色球场是从空间正则化弱场近似(WFA)和非LTE反演的钙II 8542观察CRISP在瑞典1米太阳望远镜。LTE和非LTE推断的光球场分量在整个大气中具有很强的相关性,在非LTE反演中具有更强的场和更高的温度。对于色球场,非LTE反演与空间正则化的WFA相关性很好。我们发现强场补丁超过4.5千克的光球,共同位于类似的浓度超过3千克的色球。得到的场强比数值模型高2-3倍,更集中和结构化的光球到色球剪切接近极性反转线。LTE和非LTE的Fe I反演产生基本上相同的光球场,而ME反演未能再现Fe I在发射的场矢量方向。我们的反演证实了由数值模型预测的磁通绳足点的位置。然而,预处理和较低的空间分辨率导致模型中的场比数据显示的更弱和更平滑。这强调了需要更高的空间分辨率的模型,以更好地约束喷发前的通量绳。

英文摘要:

Obtaining the magnetic field vector accurately in the solar atmosphere is essential for studying changes in field topology during flares and to reliably model space weather. We tackle this problem by applying various inversion methods to a confined X2.2 flare in NOAA AR 12673 on September 6, 2017, comparing the photospheric and chromospheric magnetic field vector with those from two numerical models of this event. We obtain the photospheric field from Milne-Eddington (ME) and (non-)local thermal equilibrium (non-LTE) inversions of Hinode SOT/SP Fe I 6301.5Å and 6302.5Å. The chromospheric field is obtained from a spatially-regularised weak field approximation (WFA) and non-LTE inversions of Ca II 8542Å observed with CRISP at the Swedish 1-m Solar Telescope. The LTE- and non-LTE-inferred photospheric field components are strongly correlated throughout the atmosphere, with stronger field and higher temperatures in the non-LTE inversions. For the chromospheric field, the non-LTE inversions correlate well with the spatially-regularised WFA. We find strong-field patches of over 4.5 kG in the photosphere, co-located with similar concentrations exceeding 3 kG in the chromosphere. The obtained field strengths are up to 2-3 times higher than in the numerical models, with more concentrated and structured photosphere-to-chromosphere shear close to the polarity inversion line. The LTE and non-LTE Fe I inversions yield essentially the same photospheric field, while ME inversions fail to reproduce the field vector orientation where Fe I is in emission. Our inversions confirm the locations of flux rope footpoints that are predicted by numerical models. However, pre-processing and lower spatial resolution lead to weaker and smoother field in the models than what the data indicate. This emphasises the need for higher spatial resolution in the models to better constrain pre-eruptive flux ropes.

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