分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Magnetic field extrapolation is a fundamental tool to reconstruct the three-dimensional solar coronal magnetic field. However, the prevalently used force-free field model might not be applicable in the lower atmosphere, where plasma \b{eta} is greater than 1. In this work, we perform extrapolation in active region 12158, based on an updated magnetohydrostatic (MHS) method. By comparing the results with those from the force-free field method of Current-Field Iteration in Spherical Coordinates (CFITS), we find that the overall properties, which are characterized by the magnetic free energy and helicity, are roughly the same after volume integral. The major differences lie in the magnetic configuration and the twist number of magnetic flux rope (MFR). A coherent MFR with twist around 1 is reproduced from CFITS. In another manner, two sets of MFR, which are highly twisted and slightly coupled, are derived by the MHS method. The latter one is better constrained by the high-resolution observations, such as the filament fibrils, pre-eruptive braiding characteristics and the eruptive double-J shaped hot channel. Overall, our work shows the MHS method is more promising to reproduce the magnetic fine structures that can well match the observations not only in the chromosphere but also in the corona. This initiates the necessity of reconsidering the simplification of low atmosphere for currently widely used nonlinear force-free extrapolation method, since such assumption will not only omit the magnetic structures at low atmosphere but also affect those obtained in the corona, and therefore bringing in ambiguity in interpreting the solar eruption.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
摘要： Magnetic field extrapolation is a fundamental tool to reconstruct the three-dimensional solar coronal magnetic field. However, the prevalently used force-free field model might not be applicable in the lower atmosphere, where plasma \b{eta} is greater than 1. In this work, we perform extrapolation in active region 12158, based on an updated magnetohydrostatic (MHS) method. By comparing the results with those from the force-free field method of Current-Field Iteration in Spherical Coordinates (CFITS), we find that the overall properties, which are characterized by the magnetic free energy and helicity, are roughly the same after volume integral. The major differences lie in the magnetic configuration and the twist number of magnetic flux rope (MFR). A coherent MFR with twist around 1 is reproduced from CFITS. In another manner, two sets of MFR, which are highly twisted and slightly coupled, are derived by the MHS method. The latter one is better constrained by the high-resolution observations, such as the filament fibrils, pre-eruptive braiding characteristics and the eruptive double-J shaped hot channel. Overall, our work shows the MHS method is more promising to reproduce the magnetic fine structures that can well match the observations not only in the chromosphere but also in the corona. This initiates the necessity of reconsidering the simplification of low atmosphere for currently widely used nonlinear force-free extrapolation method, since such assumption will not only omit the magnetic structures at low atmosphere but also affect those obtained in the corona, and therefore bringing in ambiguity in interpreting the solar eruption.
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