AI 中文总结
研究初始场向速度流引发的非线性纵向扰动对精细结构日冕环链中扭结振荡阻尼的影响，用二维理想磁流体动力学模拟不同流动几何形状，发现其显著影响阻尼时间，为日冕相关研究提供重要参考。
AI 中文摘要
我们研究了由初始场向速度流引发的非线性纵向扰动对等压条件下精细结构、冷却日冕环链中驻立扭结振荡阻尼的影响。使用二维理想磁流体动力学模拟，我们对不同的实际流动几何形状（有界、无界和外部）进行建模，并量化它们对波激发、阻尼和能量泄漏的影响。我们模拟的环链包含强密度对比（\(d = 5\) 和 \(d = 20\)），提供了与来自日冕卫星（Hinode/SOT）和太阳动力学天文台（SDO/AIA）的冷环观测一致的配置。我们的结果表明，虽然非线性扰动对振荡周期影响较小，但它们会显著改变阻尼时间。无界流产生最强的阻尼，与有界流相比，由于增强的波流耦合和散射，阻尼时间减少了高达约 \(25\%\)。纵向不均匀流进一步加剧了阻尼，高密度链向均匀流极限的收敛速度更快。在具有超音速内部流的情况下，还会激发慢香肠模谐波和弱慢震，表明在流动主导的环中产生了混合模波响应。这些发现表明，实际的、空间扩展的非线性扰动在扭结振荡的阻尼中起重要作用，应纳入正向建模和日冕地震学诊断中。
英文摘要
We investigate the influence of nonlinear longitudinal disturbances, triggered by an initial field-aligned velocity flow, on the damping of standing kink oscillations in fine-structured, cool coronal loop strands under isobaric conditions. Using two-dimensional ideal MHD simulations, we model different realistic flow geometries, bounded, unbounded, and external, and quantify their impact on wave excitation, damping, and energy leakage. Our modelled loop strand incorporates strong density contrasts ($d = 5$ and $d = 20$), providing a configuration consistent with cool-loop observations from Hinode/SOT and SDO/AIA. Our results show that while the nonlinear disturbances exert mild influence on the oscillation period, they substantially modify the damping time. Unbounded flows yield the strongest damping, reducing the damping time by up to $\sim 25\%$ compared to bounded flows, caused by enhanced wave-flow coupling and scattering. Longitudinally inhomogeneous flows further intensify the damping, with high-density strands exhibiting faster convergence toward the uniform-flow limit. In cases with supersonic internal flow, slow sausage-mode harmonics and weak slow shocks are additionally excited, indicating the generation of mixed-mode wave responses in flow-dominated loops. These findings demonstrate that realistic, spatially extended nonlinear disturbances play a significant role in the damping of kink oscillations and should be incorporated into forward modeling and coronal seismology diagnostics.
Comments19 pages, 12 figures, 1 table, Accepted for publication in the Philosophical Transactions of the Royal Society A
