Magnetohydrodynamic Wave Mode Identification in Circular and Elliptical Sunspot Umbrae: Evidence for High-order Modes
Magnetohydrodynamic Wave Mode Identification in Circular and Elliptical Sunspot Umbrae: Evidence for High-order Modes
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DOI：
10.3847/1538-4357/ac51d9
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发表时间：
2022-02
期刊：
影响因子：
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通讯作者：
A. B. Albidah;V. Fedun;A. Aldhafeeri;I. Ballai;W. Brevis;D. Jess;J. Higham;M. Stangalini;S. Silva;G. Verth
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作者：
A. B. Albidah;V. Fedun;A. Aldhafeeri;I. Ballai;W. Brevis;D. Jess;J. Higham;M. Stangalini;S. Silva;G. Verth
在本文中，我们提供了明确的直接证据，多个并发高阶磁流体动力学（MHD）模式在圆形和椭圆形太阳黑子应用适当的正交分解（POD）和动态模式分解（DMD）技术对太阳观测数据。这些技术在流体力学、水力学和颗粒流领域有很好的文献记载和验证，但在太阳物理学领域相对较新。POD基于空间正交性来识别模式，并根据模式对信号方差的贡献提供模式的清晰排名，而DMD则解决时间正交的模式。对圆形和椭圆形黑子的色球Hα线在6562.808的POD和DMD分析表明，基本的慢香肠模和扭折体模以及高阶慢香肠模和扭折体模都明显存在。此外，对于各种慢体模式，在圆形太阳黑子中发现了快速表面扭结模式存在的证据。所有的MHD模式模式的交叉相关与理论预测的对应物，我们证明了椭圆度不能忽略时解释MHD波模式。高阶MHD波模式对本影横截面形状的不规则性更加敏感;因此，必须考虑到这一点，以便更准确地模拟太阳黑子和孔隙中的模式。
In this paper, we provide clear direct evidence of multiple concurrent higher-order magnetohydrodynamic (MHD) modes in circular and elliptical sunspots by applying both proper orthogonal decomposition (POD) and dynamic mode decomposition (DMD) techniques on solar observational data. These techniques are well documented and validated in the areas of fluid mechanics, hydraulics, and granular flows but are relatively new to the field of solar physics. While POD identifies modes based on orthogonality in space and provides a clear ranking of modes in terms of their contribution to the variance of the signal, DMD resolves modes that are orthogonal in time. The clear presence of the fundamental slow sausage and kink body modes, as well as higher-order slow sausage and kink body modes, have been identified using POD and DMD analysis of the chromospheric Hα line at 6562.808 Å for both the circular and elliptical sunspots. Additionally, for the various slow body modes, evidence for the presence of the fast surface kink mode was found in the circular sunspot. All of the MHD mode patterns were cross-correlated with their theoretically predicted counterparts, and we demonstrated that ellipticity cannot be neglected when interpreting MHD wave modes. The higher-order MHD wave modes are even more sensitive to irregularities in umbral cross-sectional shapes; hence, this must be taken into account for more accurate modeling of the modes in sunspots and pores.