论文标题
色球磁场：He I 10830 A观测值的比较非线性磁场外推
Chromospheric magnetic field: A comparison of He I 10830 A observations with nonlinear force-free field extrapolation
论文作者
论文摘要
非线性力场（NLFFF）建模已广泛用于推断太阳电晕中的三维（3D）磁场。 NLFFF外推的假设之一是等离子体β较低，但是这种情况在Photosphere中被认为是不正确的。我们通过在He I 10830 A时通过光谱极化观测值检查了两个活性区域中色球磁场的直接测量，该观测值与从Photosphere外推的电位场和NLFFFS进行了比较。比较允许对NLFFF外推的不确定性进行定量估计。我们的分析表明，与光磁场相比，观察到的色球磁场可能具有更大的非电位性。此外，从光球磁场的NLFFF推断出来，色球高度的大型非电位性可能不会再现。在某些位置，剪切签名的角度可能达到30-40度的非电位性低估的大小。这种偏差可能是由于光球中的非福利性而引起的。我们的研究表明，在NLFFF建模中纳入了测得的色球磁场以改善冠状外推的重要性。
The nonlinear force-free field (NLFFF) modeling has been extensively used to infer the three-dimensional (3D) magnetic field in the solar corona. One of the assumptions in the NLFFF extrapolation is that the plasma beta is low, but this condition is considered to be incorrect in the photosphere. We examine direct measurements of the chromospheric magnetic field in two active regions through spectropolarimetric observations at He I 10830 A, which are compared with the potential fields and NLFFFs extrapolated from the photosphere. The comparisons allow quantitative estimation of the uncertainty in the NLFFF extrapolation from the photosphere. Our analysis shows that observed chromospheric magnetic field may have larger non-potentiality compared to the photospheric magnetic field. Moreover, the large non-potentiality in the chromospheric height may not be reproduced by the NLFFF extrapolation from the photospheric magnetic field. The magnitude of the underestimation of the non-potentiality at chromospheric heights may reach 30-40 degree in shear signed angle in some locations. This deviation may be caused by the non-force-freeness in the photosphere. Our study suggests the importance of the inclusion of measured chromospheric magnetic fields in the NLFFF modeling for the improvement of the coronal extrapolation.
