发表机构
University of Salford（索尔福德大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文从电阻MHD推导出连续β-FPUT模型，解释日冕环无衰减横向振荡，通过内部流体机制实现频率自聚焦，并提供宏观日冕地震学方法反演波导精细结构参数。
AI 中文摘要
我们提出了一个解析框架，直接从三阶电阻磁流体动力学（MHD）展开推导出流体连续介质$\beta$-费米-帕斯塔-乌拉姆-青（$\beta$-FPUT）系统，以解释在太阳日冕环中观测到的持续、无衰减的横向振荡。对于沿纵向磁场传播且具有横场密度变化的连续波场，多尺度展开表明，由于面外极化对称性，二次$\mathcal{O}(2)$平流项和麦克斯韦张力项完全消失。相反，二次纵向有质动力驱动场向密度调制，该调制对主横向波产生反作用，从而产生三次$\mathcal{O}(3)$恢复力。在长波长极限下，控制方程简化为流体连续介质修正Korteweg-de Vries（mKdV）系统，其中横场轮廓变化提供了非线性色散机制。我们证明了这种内部流体机制建立了稳定的、振幅依赖的频率自聚焦，该自聚焦使相邻元素相位锁定，并防止相位混合波衰减，而无需外部稳态驱动参数化。该框架能够实现宏观尺度日冕地震学，提供闭合形式表达式，将观测到的无衰减波包持续时间反演为未解析的横场密度梯度尺度长度（$L_x$）和内部体积填充因子（$f_V$），而无需依赖传统的发射测量或光谱线比诊断。正如恩里科·费米历史上使用宏观尺度位移来估算复杂原子爆炸产额一样，该框架建立了一种范式，即监测宏观振荡持续时间使观测者能够提取精细尺度、否则无法解析的波导特性。
英文摘要
We present an analytical framework deriving the fluid-continuum $β$-Fermi-Pasta-Ulam-Tsingou ($β$-FPUT) system directly from a third-order resistive magnetohydrodynamics (MHD) expansion to explain persistent, decayless transverse oscillations observed in solar coronal loops. For a continuous wave field propagating along a longitudinal magnetic field with cross-field density variations, a multi-scale expansion demonstrates that quadratic $\mathcal{O}(2)$ advective and Maxwell tension terms vanish identically due to out-of-plane polarization symmetry. Instead, the quadratic longitudinal ponderomotive force drives field-aligned density modulations that back-react on the primary transverse wave, yielding a cubic $\mathcal{O}(3)$ restoring force. In the long-wavelength limit, the governing equations reduce to a fluid-continuum Modified Korteweg-de Vries (mKdV) system where cross-field profile variation provides the non-linear dispersive mechanism. We prove that this internal fluid mechanism establishes stable, amplitude-dependent frequency self-focusing, which phase-locks adjacent elements and prevents phase-mixing wave attenuation without requiring external steady driving parameterizations. This framework enables macro-scale coronal seismology, providing closed-form expressions to invert observed decayless wave-packet durations to compute the unresolved cross-field density gradient scale length ($L_x$) and the internal volumetric filling factor ($f_V$) without relying on traditional emission measure or spectroscopic line-ratio diagnostics. Much like famous Enrico Fermi's historic use of macro-scale displacements to estimate complex atomic explosion yields, this framework establishes a paradigm where monitoring macroscopic oscillation durations empowers observers to extract fine-scale, otherwise unresolvable waveguide properties.
CommentsCode, interactive simulation engine, and supplementary video available at https://doi.org/10.5281/zenodo.23120908 , submitted for publication
