论文标题
磁通管和磁能转移的多尺度动力学
Multi-scale dynamics of magnetic flux tubes and inverse magnetic energy transfer
论文作者
论文摘要
我们报告了在血浆的降低磁性流体动力学描述中，对三维磁管的三维阵列的动力学进行了分析和数值研究。我们建议该系统的长期演变由通量管的合并决定，并且此类合并受到每个管的磁电势和轴向通量的保护（理想）不变性的保护。我们还建议，在垂直于合并平面的方向上，通量管以批判性平衡的方式演变。这些概念使我们能够为诸如磁能和含能量量表等数量的分析模型构建分析模型。特别重要的是，与其二维对应物一样，该系统表现出磁能的反向传递，仅在系统尺度下终止。我们执行直接的数值模拟，以确认这些预测并揭示系统演变的其他有趣方面。例如，我们发现早期演化的特征是初始磁能的急剧衰减，我们将其归因于当前板的无处不在形成。我们还表明，当初始条件是一个随机的小规模磁性种子场时，定量相似的磁能反向转移。
We report on an analytical and numerical study of the dynamics of a three-dimensional array of identical magnetic flux tubes in the reduced-magnetohydrodynamic description of the plasma. We propose that the long-time evolution of this system is dictated by flux-tube mergers and that such mergers are dynamically constrained by the conservation of the pertinent (ideal) invariants, {\it viz.} the magnetic potential and axial fluxes of each tube. We also propose that in the direction perpendicular to the merging plane, flux tubes evolve in critically-balanced fashion. These notions allow us to construct an analytical model for how quantities such as the magnetic energy and the energy-containing scale evolve as functions of time. Of particular importance is the conclusion that, like its two-dimensional counterpart, this system exhibits an inverse transfer of magnetic energy that terminates only at the system scale. We perform direct numerical simulations that confirm these predictions and reveal other interesting aspects of the evolution of the system. We find, for example, that the early time evolution is characterized by a sharp decay of the initial magnetic energy, which we attribute to the ubiquitous formation of current sheets. We also show that a quantitatively similar inverse transfer of magnetic energy is observed when the initial condition is a random, small-scale magnetic seed field.
