Can We Improve the Preprocessing of Photospheric Vector Magnetograms by the Inclusion of Chromospheric Observations?
Can We Improve the Preprocessing of Photospheric Vector Magnetograms by the Inclusion of Chromospheric Observations?
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DOI：
10.1007/s11207-008-9130-y
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发表时间：
2008-01
期刊：
影响因子：
2.8
通讯作者：
T. Wiegelmann;J. Thalmann;C. Schrijver;M. DeRosa;T. Metcalf
中科院分区：
文献类型：
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作者：
T. Wiegelmann;J. Thalmann;C. Schrijver;M. DeRosa;T. Metcalf
太阳磁场是理解太阳大气物理过程的关键。非线性无力代码已被证明是有用的，在推断日冕场向上从底层矢量边界数据。然而，我们只能在光球层中常规地高精度地测量磁场矢量，不幸的是，这些数据不满足无力条件。因此，我们必须对这些数据进行一些变换，然后才能自洽地应用非线性无力外推代码。为此，我们已经开发了一个最小化的程序，产生一个更像色球场，使用测量的光球场矢量作为输入。该程序包括无力一致性积分，空间平滑，以及-新包括在这里提出的版本-改进匹配的场方向推断纤维可以观察到，例如，色球Hα图像。我们测试的过程中使用的模型活动区字段，包括在光球水平的浮力。所提出的预处理方法使我们能够近似色球矢量场在几度和自由能在日冕领域的百分之一。
The solar magnetic field is key to understanding the physical processes in the solar atmosphere. Nonlinear force-free codes have been shown to be useful in extrapolating the coronal field upward from underlying vector boundary data. However, we can only measure the magnetic field vector routinely with high accuracy in the photosphere, and unfortunately these data do not fulfill the force-free condition. We must therefore apply some transformations to these data before nonlinear force-free extrapolation codes can be self-consistently applied. To this end, we have developed a minimization procedure that yields a more chromosphere-like field, using the measured photospheric field vectors as input. The procedure includes force-free consistency integrals, spatial smoothing, and – newly included in the version presented here – an improved match to the field direction as inferred from fibrils as can be observed in, for example, chromospheric Hα images. We test the procedure using a model active-region field that included buoyancy forces at the photospheric level. The proposed preprocessing method allows us to approximate the chromospheric vector field to within a few degrees and the free energy in the coronal field to within one percent.