非线性无力模拟：测量磁矢量中不精确性的影响
Nonlinear force-free modelling: influence of inaccuracies in the measured magnetic vector
摘要：
内容：太阳磁场有规律地外推到日冕开始光球磁测量，可以遭受重大的不确定性。目的：在这里，我们研究如何引入到光球磁矢量的理想和嘈杂的斯托克斯参数反演的地图的不准确性影响外推的非线性无力磁场。研究方法：本文利用三维辐射磁流体模拟快照反演Stokes剖面产生的模拟矢量磁图计算非线性无力磁场。这些外推进行比较外推直接从该领域的MHD模拟，这是我们的参考。我们调查如何线的形成和仪器的影响，如噪音，有限的空间分辨率和效果，采用过滤器仪器的影响所产生的磁场结构。通过目视检查磁场分布进行定性比较，并通过不同度量进行定量比较。结果如下：如果理想的斯托克斯数据被反演，则重建的场是最准确的，如果包括仪器效应和噪声，则重建的场变得不太准确。结果表明，在这里测试的非线性无力场外推法是相对不敏感的噪声的影响，在测量的偏振光谱与当今的仪器一致的水平。结论标题：我们的研究结果表明，我们可以重建日冕磁场作为一个非线性的无力场从现实的光球测量的精度为百分之几，至少在没有太阳黑子。
英文摘要：
Context: Solar magnetic fields are regularly extrapolated into the corona starting from photospheric magnetic measurements that can suffer from significant uncertainties. Aims: Here we study how inaccuracies introduced into the maps of the photospheric magnetic vector from the inversion of ideal and noisy Stokes parameters influence the extrapolation of nonlinear force-free magnetic fields. Methods: We compute nonlinear force-free magnetic fields based on simulated vector magnetograms, which have been produced by the inversion of Stokes profiles, computed froma 3-D radiation MHD simulation snapshot. These extrapolations are compared with extrapolations starting directly from the field in the MHD simulations, which is our reference. We investigate how line formation and instrumental effects such as noise, limited spatial resolution and the effect of employing a filter instrument influence the resulting magnetic field structure. The comparison is done qualitatively by visual inspection of the magnetic field distribution and quantitatively by different metrics. Results: The reconstructed field is most accurate if ideal Stokes data are inverted and becomes less accurate if instrumental effects and noise are included. The results demonstrate that the non-linear force-free field extrapolation method tested here is relatively insensitive to the effects of noise in measured polarization spectra at levels consistent with present-day instruments. Conclusions heading: Our results show that we can reconstruct the coronal magnetic field as a nonlinear force-free field from realistic photospheric measurements with an accuracy of a few percent, at least in the absence of sunspots.
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