论文标题
在剪切流湍流中大尺度上隔离磁能的机制
Mechanism for Sequestering Magnetic Energy at Large Scales in Shear-Flow Turbulence
论文作者
论文摘要
鉴于天体物理学中对大尺度磁场的持续观察，通过大规模剪切流对磁场的扭曲，通常假定导致小尺度的强化和产生。结果表明，在磁性水力动力的湍流中，不稳定的剪切流具有隔离磁能在大尺度上具有出乎意料的效果，这是由于对非线性激发的大规模稳定特征模的过滤运动的应对性运动。通过人工去除稳定模式，通过耗散速率，能量传递速率和可视化的可视化来量化此效果。这些分析表明，基于线性不稳定性物理学的预测会错过实质动力学，包括磁波动的动力学。
Straining of magnetic fields by large-scale shear flow, generally assumed to lead to intensification and generation of small scales, is re-examined in light of the persistent observation of large-scale magnetic fields in astrophysics. It is shown that, in magnetohydrodynamic turbulence, unstable shear flows have the unexpected effect of sequestering magnetic energy at large scales, due to counteracting straining motion of nonlinearly excited large-scale stable eigenmodes. This effect is quantified via dissipation rates, energy transfer rates, and visualizations of magnetic field evolution by artificially removing the stable modes. These analyses show that predictions based upon physics of the linear instability alone miss substantial dynamics, including those of magnetic fluctuations.
