Magnetohydrostatic modeling of AR11768 based on a SUNRISE/IMaX vector magnetogram
Magnetohydrostatic modeling of AR11768 based on a SUNRISE/IMaX vector magnetogram
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DOI：
10.1051/0004-6361/202037766
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发表时间：
2020-05
影响因子：
6.5
通讯作者：
Xiaoshuai Zhu;T. Wiegelmann;S. Solanki
中科院分区：
文献类型：
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作者：
Xiaoshuai Zhu;T. Wiegelmann;S. Solanki
上下文高分辨率的磁场测量通常只在太阳光球层中进行。高层，如色球层和日冕，可以通过外推这些光球磁场矢量向上建模。在日冕中，等离子体力可以忽略，洛伦兹力消失。在上层光球层和色球层，磁力和引力是同等重要的，但情况并非如此。处理这个问题的一种方法是计算等离子体和磁场自洽，在最低阶磁流体静力学（MHS）模型。非无力层相当薄，MHS模型需要高分辨率的光球磁场测量作为下边界条件。目标。我们的目标是推导出磁场，等离子体压力，和密度的AR 11768通过应用新开发的外推技术嵌入SDO/HMI磁图中的日出/IMAX数据。方法.我们使用的MHS建模的优化方法。初始条件由非线性无力场（NLFFF）和重力层结大气组成。在优化过程中，磁场，等离子体压力和密度计算自洽。结果在非无力层，这是空间上解决了新的代码，洛仑兹力有效地平衡的气体压力梯度力和重力。在强场区，气压和密度都是亏损的，这与观测结果是一致的。然而，在有源区边缘的某些部分也观察到更致密的等离子体。在色球层中，纤维状等离子体结构很好地跟踪磁场。日出/SuFI 3000 X射线图像中的亮点通常伴随着等离子体压力和电流浓度。此外，MHS磁力线与所选色球纤维间夹角的平均值为11.8°，小于NLFFF模型（15.7°）和线性MHS模型（20.9°）的计算值。这表明，MHS解决方案提供了一个更好的代表性的磁场在色球层。
Context. High-resolution magnetic field measurements are routinely only done in the solar photosphere. Higher layers, such as the chromosphere and corona, can be modeled by extrapolating these photospheric magnetic field vectors upward. In the solar corona, plasma forces can be neglected and the Lorentz force vanishes. This is not the case in the upper photosphere and chromosphere where magnetic and nonmagnetic forces are equally important. One way to deal with this problem is to compute the plasma and magnetic field self-consistently, in lowest order with a magnetohydrostatic (MHS) model. The non-force-free layer is rather thin and MHS models require high-resolution photospheric magnetic field measurements as the lower boundary condition. Aims. We aim to derive the magnetic field, plasma pressure, and density of AR11768 by applying the newly developed extrapolation technique to the SUNRISE/IMaX data embedded in SDO/HMI magnetogram. Methods. We used an optimization method for the MHS modeling. The initial conditions consist of a nonlinear force-free field (NLFFF) and a gravity-stratified atmosphere. During the optimization procedure, the magnetic field, plasma pressure, and density are computed self-consistently. Results. In the non-force-free layer, which is spatially resolved by the new code, Lorentz forces are effectively balanced by the gas pressure gradient force and gravity force. The pressure and density are depleted in strong field regions, which is consistent with observations. Denser plasma, however, is also observed at some parts of the active region edges. In the chromosphere, the fibril-like plasma structures trace the magnetic field nicely. Bright points in SUNRISE/SuFI 3000 Å images are often accompanied by the plasma pressure and electric current concentrations. In addition, the average of angle between MHS field lines and the selected chromospheric fibrils is 11.8°, which is smaller than those computed from the NLFFF model (15.7°) and linear MHS model (20.9°). This indicates that the MHS solution provides a better representation of the magnetic field in the chromosphere.