发表机构
Institute of Plasma Turbulence and Magnetic Fields（等离子体湍流与磁场研究所）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本文通过三种α和β系数推导方法分析DNS数据，发现电流螺旋度调节湍流磁扩散系数，非线性阶段需加入湍流磁场贡献以避免无界增长，β效应主导磁场演化。
AI 中文摘要
我们利用基于大尺度磁场$\overline{\mathbf{B}}$、湍流速度$\mathbf{u}$和湍流磁场$\mathbf{b}$的三种互补的α和β系数推导方法，研究了电流螺旋度对湍流磁扩散系数$\beta$的影响。将这些系数应用于原始DNS数据，我们重建了$\overline{\mathbf{B}}$，并将结果与原始模拟进行了比较。在运动学阶段，所有模型均与DNS数据吻合良好。然而，在非线性阶段，仅使用$\beta_{\mathrm{vv-vw}}$会导致$\overline{\mathbf{B}}$无界增长。加入湍流磁场的贡献（$\beta_{\mathrm{bb+jb}}$）抑制了这种非物理增长，并恢复与DNS结果的一致性。我们发现，动力学螺旋度使$\beta$更负，而电流螺旋度则将其拉回零附近。系数的加权组合进一步表明，$\beta$效应在整个过程中主导$\overline{\mathbf{B}}$的演化，而α效应主要对非线性阶段维持磁场起重要作用。提供了相应的IDL分析脚本，以促进理论模型的实际应用。
英文摘要
We investigate the influence of current helicity on the turbulent magnetic diffusivity $β$ using three complementary derivations of the $α$ and $β$ coefficients, based on the large-scale magnetic field $\overline{\mathbf{B}}$, the turbulent velocity $\mathbf{u}$, and the turbulent magnetic field $\mathbf{b}$. Applying these coefficients to raw DNS data, we reconstruct $\overline{\mathbf{B}}$ and compare the results with the original simulations. In the kinematic regime all models agree well with the DNS data. In the nonlinear regime, however, $β_{\mathrm{vv-vw}}$ alone produces unbounded growth of $\overline{\mathbf{B}}$. Including the contribution from turbulent magnetic fields ($β_{\mathrm{bb+jb}}$) suppresses this unphysical growth and restores agreement with the DNS results. We find that kinetic helicity drives $β$ more negative, while current helicity shifts it back toward zero. Weighted combinations of the coefficients further show that the $β$ effect dominates the evolution of $\overline{\mathbf{B}}$ throughout, whereas the $α$ effect becomes important mainly for sustaining the field in the nonlinear regime. The corresponding IDL analysis scripts are provided to facilitate practical implementation of the theoretical models.
Comments26p, IDL analysis code in Appendix
