论文标题
圆形和椭圆形的黑子遮阳杆中的磁流失动力波模式识别:高阶模式的证据
Magnetohydrodynamic wave mode identification in circular and elliptical sunspot umbrae: evidence for high order modes
论文作者
论文摘要
在本文中,我们通过将适当的正交分解(POD)和动态模式分解(DMD)技术应用于圆形和椭圆形黑子中的多个并发高阶磁性水力学(MHD)模式的直接证据。这些技术在流体力学,液压和颗粒流的领域有充分的文献记载和验证,但在太阳能物理领域相对较新。虽然POD基于空间的正交性标识模式,并且它根据其对信号差异的贡献提供了清晰的模式排名,但DMD解析了时间正交的模式。使用POD和DMD分析鉴定出了圆形和循环的Sunspots的POD和DMD分析,使用POD和DMD分析,使用POD和DMD分析来确定基本慢的香肠和扭结体模式的明显存在,以及高阶慢速香肠和扭结体模式。此外,在各种慢速体模式下,在圆形黑子中发现了快速表面扭结模式的证据。所有MHD模式模式与理论上预测的对应物交叉相关,我们证明在解释MHD波模式时不能忽略椭圆度。高阶MHD波模式对蒙布拉尔横截面形状的不规则性更加敏感,因此必须考虑到更精确的黑子和毛孔模式的建模。
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, yet are relatively new to the field of solar physics. While POD identifies modes based on orthogonality in space and it 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 H$α$ line at 6562.808~Å for both the circular and elliptical sunspots. Additionally, to the various slow body modes, evidence for the presence of the fast surface kink mode was found in the circular sunspot. All the MHD modes 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 modelling of the modes in sunspots and pores.