torus 不稳定性阈值的参数化研究
Parametric Study of the Torus Instability Threshold
浏览论文内容
中文总结 AI 辅助
本文通过参数化数值研究，利用 Titov-Démoulin 平衡模型探究 torus 不稳定性阈值，发现外部环向场和线拴可提升阈值，且基于势场的近似阈值与精确值吻合良好，解释了观测与数值结果的离散性。
中文摘要 AI 辅助
拱形电流通道的 torus 不稳定性被认为是引发和驱动太阳及恒星重大爆发的原因，该不稳定性的阈值由电流通道位置处平衡外部极向场（即所谓的束缚场）的临界衰减指数决定，目前对该阈值的了解尚不充分。本文采用力-free 的 Titov-Démoulin 线拴部分环形电流通道与通量绳平衡模型，对该阈值开展参数化数值研究，以解决阈值相对于其标准值 n_cr=3/2 的离散问题。在太阳通量绳爆发的数值与观测研究中，通常发现阈值的离散范围为 n_cr≈1~2。当外部环向（引导或剪切）场为零且几何形状近似为半圆形（对应光球线拴的最小值）时，研究发现阈值处于理论预期的≈1~1.5 范围内。外部环向场会对该不稳定性产生强烈的稳定作用，将阈值提高至≈2.5，这可以解释观测和数值研究中高于标准值的结果。研究还发现线拴同样具有稳定作用；此外，本文还基于势场计算近似阈值，结果表明，只要使用垂直于通量绳轴的水平分量来近似外部极向场，近似阈值与精确数值结果吻合度极高。
英文摘要
The torus instability of an arched current channel has been suggested to initiate and drive major solar and stellar eruptions. Its threshold, given by the critical decay index of the equilibrium external poloidal field (the so-called strapping field) at the position of the current channel, is insufficiently known. Here, we carry out a parametric numerical study of the threshold, employing the force-free Titov-Démoulin (TD) equilibrium of a line-tied partial toroidal current channel and flux rope. This addresses the scatter of the threshold about its canonical value, $n_\mathrm{cr}=3/2$. Values scattering in the range $n_\mathrm{cr}\approx$\,1--2 are typically found in numerical and observational studies of flux rope eruptions on the Sun. For zero external toroidal (guide, or shear) field and approximately semicircular geometry (corresponding to minimal photospheric line-tying), we find the threshold to lie in the theoretically expected range of $\approx$\,1--1.5. An external toroidal field introduces a strong stabilizing effect on the instability, raising the threshold up to $\sim$\,2.5, which can explain observational and numerical results above the canonical value. Line-tying is found to act as a stabilizer as well. We also consider the approximate threshold based on the potential field and find a very good agreement with the exact numerical value, provided the horizontal component perpendicular to the flux rope axis is used to approximate the external poloidal field.
发表机构
- Purple Mountain Observatory, Chinese Academy of Sciences（中国科学院紫金山天文台）
- Institute of Physics and Astronomy, University of Potsdam（波茨坦大学物理与天文学研究所）
- Department of Geophysics and Planetary Sciences, University of Science and Technology of China（中国科学技术大学地球物理与行星科学学院）
机构由 AI 辅助整理，请以论文原文为准。
