Nonlinear Force-free Coronal Magnetic Stereoscopy
Nonlinear Force-free Coronal Magnetic Stereoscopy
复制标题
非线性无力冠状磁立体镜
DOI：
10.3847/1538-4357/aa5b9a
复制
发表时间：
2017
期刊：
影响因子：
--
通讯作者：
B. Inhester
中科院分区：
文献类型：
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作者：
I. Chifu;T. Wiegelmann;B. Inhester
太阳日冕磁场的三维结构在过去已经通过两种完全不同的方法获得了深入的了解。第一种方法是非线性无力场（NLFFF）外推，它使用光球矢量磁图作为边界条件。第二种方法使用从不同Vantage位置在EUV冠状图像中观察到的冠状磁环的立体观察。这两种方法各有优缺点。外推方法对边界数据中的噪声和不一致性很敏感，并且立体视觉的准确性受到在不同图像中识别相同结构的能力以及视图方向之间的分离角的影响。因此，对于相同的观测数据，用这两种方法计算的三维日冕磁场不一定一致。在较早的工作（论文I），我们扩展了我们的NLFFF优化代码，包括立体约束。该方法成功地测试了合成数据，并在这项工作中，我们应用新开发的代码的SDO/HMI，SDO/AIA，和两个立体声航天器的组合数据集。扩展的方法（称为S-NLFFF）包含一个额外的术语，监测和最大限度地减少局部磁场方向和立体重建的3D冠状环的方向之间的角度。我们发现，当我们规定的3D立体重建的循环的形状，S-NLFFF方法导致一个更好的协议之间的建模领域和立体重建的循环。我们还发现电流和磁场之间的角度明显减小了两倍。这表明通过S-NLFFF获得的无力解的质量得到改善。
Insights into the 3D structure of the solar coronal magnetic field have been obtained in the past by two completely different approaches. The first approach are nonlinear force-free field (NLFFF) extrapolations, which use photospheric vector magnetograms as boundary condition. The second approach uses stereoscopy of coronal magnetic loops observed in EUV coronal images from different vantage points. Both approaches have their strengths and weaknesses. Extrapolation methods are sensitive to noise and inconsistencies in the boundary data, and the accuracy of stereoscopy is affected by the ability of identifying the same structure in different images and by the separation angle between the view directions. As a consequence, for the same observational data, the 3D coronal magnetic fields computed with the two methods do not necessarily coincide. In an earlier work (Paper I) we extended our NLFFF optimization code by including stereoscopic constrains. The method was successfully tested with synthetic data, and within this work, we apply the newly developed code to a combined data set from SDO/HMI, SDO/AIA, and the two STEREO spacecraft. The extended method (called S-NLFFF) contains an additional term that monitors and minimizes the angle between the local magnetic field direction and the orientation of the 3D coronal loops reconstructed by stereoscopy. We find that when we prescribe the shape of the 3D stereoscopically reconstructed loops, the S-NLFFF method leads to a much better agreement between the modeled field and the stereoscopically reconstructed loops. We also find an appreciable decrease by a factor of two in the angle between the current and the magnetic field. This indicates the improved quality of the force-free solution obtained by S-NLFFF.