Testing a Data-driven Active Region Evolution Model with Boundary Data at Different Heights from a Solar Magnetic Flux Emergence Simulation
Testing a Data-driven Active Region Evolution Model with Boundary Data at Different Heights from a Solar Magnetic Flux Emergence Simulation
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DOI：
10.3847/1538-4357/abb5ac
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发表时间：
2020-10
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影响因子：
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通讯作者：
C. Jiang;S. Toriumi
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文献类型：
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作者：
C. Jiang;S. Toriumi
为了研究日冕磁场的复杂结构和动力学，建立了一个数据驱动的活动区演化（DARE）模型。该模型配置有典型的日冕环境，由强磁场控制的稀薄气体，因此其下边界设置在日冕底部，但由光球中观察到的磁场驱动。以前的评估模型使用的数据从磁通量出现模拟（FES）表明，DARE未能再现日冕磁场的FES，这是由于这样一个事实，即光球数据在FES有一个非常强的洛伦兹力，因此虚假的流量产生的DARE模型。在这里，我们进一步测试的DARE通过使用三组数据从FES切片在递增的高度，这对应于光球层，色球层，和基地的日冕。研究发现，三组数据的关键区别在于洛伦兹力的大小，这使得数据驱动模型的表现非常不同。在光球层以上的两个较高的水平，洛伦兹力大幅下降，DARE模型达到的结果与FES更好的协议，确认洛伦兹力的边界数据是一个关键问题，影响DARE模型的结果。然而，与FES数据不同，最近发现SDO/HMI观测的光球场非常接近于无力。因此，我们认为，它仍然是合理的光球磁场作为一个近似的场在冕底驱动DARE模型。
A data-driven active region evolution (DARE) model has been developed to study the complex structures and dynamics of solar coronal magnetic fields. The model is configured with a typical coronal environment of tenuous gas governed by strong magnetic field, and thus its lower boundary is set at the base of the corona, but driven by magnetic fields observed in the photosphere. A previous assessment of the model using data from a flux emergence simulation (FES) showed that the DARE failed to reproduce the coronal magnetic field in the FES, which is attributed to the fact that the photospheric data in the FES has a very strong Lorentz force and therefore spurious flows are generated in the DARE model. Here we further test the DARE by using three sets of data from the FES sliced at incremental heights, which correspond to the photosphere, the chromosphere, and the base of the corona. It is found that the key difference in the three sets of data is the extent of the Lorentz force, which makes the data-driven model perform very differently. At the two higher levels above the photosphere, the Lorentz force decreases substantially, and the DARE model attains results in much better agreement with the FES, confirming that the Lorentz force in the boundary data is a key issue affecting the results of the DARE model. However, unlike the FES data, the photospheric field from SDO/HMI observations has recently been found to be very close to force-free. Therefore, we suggest that it is still reasonable to use the photospheric magnetic field as an approximation of the field at the coronal base to drive the DARE model.