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arXiv · 1706.00595

Comparison of Two Coronal Magnetic Field Models for Reconstructing a Sigmoidal Solar Active Region With Coronal Loops

Aiying Duan·Chaowei Jiang·Qiang Hu·Huai Zhang·G. Allen Gary·S. T. Wu·Jinbin Cao
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Abstract

Magnetic field extrapolation is an important tool to study the three-dimensional (3D) solar coronal magnetic field which is difficult to directly measure. Various analytic models and numerical codes exist but their results often drastically differ. Thus a critical comparison of the modeled magnetic field lines with the observed coronal loops is strongly required to establish the credibility of the model. Here we compare two different non-potential extrapolation codes, a non-linear force-free field code (CESE-MHD-NLFFF) and a non-force-free field (NFFF) code in modeling a solar active region (AR) that has a sigmoidal configuration just before a major flare erupted from the region. A 2D coronal-loop tracing and fitting method is employed to study the 3D misalignment angles between the extrapolated magnetic field lines and the EUV loops as imaged by SDO/AIA. It is found that the CESE-MHD-NLFFF code with preprocessed magnetogram performs the best, outputting a field which matches the coronal loops in the AR core imaged in AIA 94 Å with a misalignment angle of ~10 degree. This suggests that the CESE-MHD-NLFFF code, even without using the information of coronal loops in constraining the magnetic field, performs as good as some coronal-loop forward-fitting models. For the loops as imaged by AIA 171 Å in the outskirts of the AR, all the codes including the potential-field give comparable results of mean misalignment angle (~30 degree). Thus further improvement of the codes is needed for a better reconstruction of the long loops enveloping the core region.

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Aiying Duan, Chaowei Jiang, Qiang Hu, Huai Zhang, G. Allen Gary, S. T. Wu, Jinbin Cao. 2017-06-02. Comparison of Two Coronal Magnetic Field Models for Reconstructing a Sigmoidal Solar Active Region With Coronal Loops. https://doi.org/10.3847/1538-4357%2Faa76e1

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