AI 中文总结
研究电子磁流体动力学中电流片形成，在二维半EMHD系统用分裂分数耗散数值模拟，发现其形成主要受磁势阻尼控制，有衰减/集中二分法，增长符合能量临界自相似率，完善了对称和图景。
AI 中文摘要
薄电流片是电子磁流体动力学（EMHD）中的核心小尺度结构，与电子尺度的能量耗散和快速磁重联密切相关。我们在具有分裂分数耗散的周期性域上的二维半EMHD系统中对其形成进行了数值研究，其中磁势和垂直磁分量分别被阻尼。局部理论由对称组合阻尼平衡控制，但小尺度增长的数值起始不必遵循这种对称性。尺度分析确定面外电流是主要的可观测集中量，因为它仅通过磁势方程进行正则化。使用具有分辨率控制诊断的经过验证的傅里叶伪谱指数时间差分求解器，我们发现了明显的衰减/集中二分法。起始边界明显不对称：电流片的形成似乎主要由磁势的阻尼控制，而不是由组合阻尼强度控制。解析带坍缩到网格尺度，在网格细化下集中加剧，并且观察到的增长与能量临界自相似率一致，指数接近三。这些实验表明磁势阻尼是电流片集中的明显约束，完善了对称和的图景。
英文摘要
Thin current sheets are central small-scale structures in electron magnetohydrodynamics (EMHD), closely associated with energy dissipation and fast magnetic reconnection at electron scales. We study their formation numerically in a $2\frac{1}{2}$-dimensional EMHD system on a periodic domain with split fractional dissipation, where the magnetic potential and the vertical magnetic component are damped separately. The local theory is governed by a symmetric combined damping balance, but the numerical onset of small-scale growth need not follow this symmetry. A scaling analysis identifies the out-of-plane current as the primary concentration observable, since it is regularized only through the magnetic-potential equation. Using a validated Fourier pseudospectral exponential time-differencing solver with resolution-controlled diagnostics, we find a clear decay/concentration dichotomy. The onset boundary is markedly asymmetric: current-sheet formation appears to be controlled mainly by damping of the magnetic potential, rather than by the combined damping strength. The analyticity strip collapses to the grid scale, the concentration sharpens under grid refinement, and the observed growth is consistent with an energy-critical self-similar rate, with exponent near three. These experiments indicate that magnetic-potential damping is the apparent binding constraint for current-sheet concentration, refining the symmetric sum picture.
