arXiv 1010.60152010-10-28astro-ph.SR

太阳无力磁场外推预处理方法的比较

A comparison of preprocessing methods for solar force-free magnetic field extrapolation

M. Fuhrmann, N. Seehafer, G. Valori, T. Wiegelmann

备注：: Accepted for Astron. Astrophys
发表信息：: Astron. Astrophys. 526, A70 (2011)
DOI：: 10.1051/0004-6361/201015453

摘要：

将太阳光球矢量磁图外推到色球层和日冕的三维磁场，通常是在磁场无力的假设下进行的。通过对光球磁图进行预处理，可以提高磁场计算的精度。我们比较了目前使用的两种预处理方法，即Wiegelmann等人（2006）和Fuhrmann等人（2007）的方法。这两种预处理方法被应用到最近观察到的矢量磁图。我们研究了两种预处理算法对磁图的影响。此外，原始磁图和两个预处理的磁图分别作为输入数据的非线性无力场外推通过两种不同的方法，我们分析所产生的领域。这两种预处理方法设法显着减少的磁力和磁转矩，通过磁记录区的作用，并可能导致不兼容的假设力自由的解决方案域。这两种方法还减少了观测到的光球场中的小尺度不规则性的数量，这些不规则性会使解决方案的质量急剧恶化。对于所选的参数集，Wiegelmann等人的方法导致强场区域发生更大的变化，而弱场区域几乎没有变化，因此提供了色球层中磁场矢量的近似值，而Fuhrmann等人的方法微弱地改变了整个磁图，从而更好地保留了原始磁图中存在的模式。这两种预处理方法都将外推场的磁能含量提高到对应于势场的最小能量以上的值。此外，从预处理的磁图计算的磁场满足螺线管条件比未经预处理的计算。

英文摘要：

Extrapolations of solar photospheric vector magnetograms into three-dimensional magnetic fields in the chromosphere and corona are usually done under the assumption that the fields are force-free. The field calculations can be improved by preprocessing the photospheric magnetograms. We compare two preprocessing methods presently in use, namely the methods of Wiegelmann et al. (2006) and Fuhrmann et al. (2007). The two preprocessing methods were applied to a recently observed vector magnetogram. We examine the changes in the magnetogram effected by the two preprocessing algorithms. Furthermore, the original magnetogram and the two preprocessed magnetograms were each used as input data for nonlinear force-free field extrapolations by means of two different methods, and we analyze the resulting fields. Both preprocessing methods managed to significantly decrease the magnetic forces and magnetic torques that act through the magnetogram area and that can cause incompatibilities with the assumption of force-freeness in the solution domain. Both methods also reduced the amount of small-scale irregularities in the observed photospheric field, which can sharply worsen the quality of the solutions. For the chosen parameter set, the Wiegelmann et al. method led to greater changes in strong-field areas, leaving weak-field areas mostly unchanged, and thus providing an approximation of the magnetic field vector in the chromosphere, while the Fuhrmann et al. method weakly changed the whole magnetogram, thereby better preserving patterns present in the original magnetogram. Both preprocessing methods raised the magnetic energy content of the extrapolated fields to values above the minimum energy, corresponding to the potential field. Also, the fields calculated from the preprocessed magnetograms fulfill the solenoidal condition better than those calculated without preprocessing.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

摘要：

英文摘要：

相关论文