论文标题
小规模发电机中的耗散磁性结构和尺度
Dissipative magnetic structures and scales in small-scale dynamos
论文作者
论文摘要
小规模的发电机在现代天体物理学中起着重要作用，尤其是在银河系和外层面尺度上。由于发电机的作用，纯粹的流体动力kolmogorov湍流几乎不存在，并且通常被水磁湍流所取代。了解耗散磁结构的大小在估计银河闪烁的时间尺度以及星际和播出的小型小尺度发电机的其他观察和理论方面很重要。在这里，我们表明，在小尺度发电机的运动学阶段，磁能光谱尺度的截止波数尺度如预期的，对于大型磁性prandtl数字，但对于中等小值的方式也以相同的方式持续 - 与预期相反。对于临界磁性prandtl的数量约为0.3，发现耗散型和电阻截止在同一波数字上发生。在非线性饱和度方案中，临界磁性prandtl数量变为统一。现在，截止尺度的缩放比例较浅，磁性prandtl数低于大约三个，而与运动学状态相比，较陡峭的尺度。
Small-scale dynamos play important roles in modern astrophysics, especially on Galactic and extragalactic scales. Owing to dynamo action, purely hydrodynamic Kolmogorov turbulence hardly exists and is often replaced by hydromagnetic turbulence. Understanding the size of dissipative magnetic structures is important in estimating the time scale of Galactic scintillation and other observational and theoretical aspects of interstellar and intergalactic small-scale dynamos. Here we show that, during the kinematic phase of the small-scale dynamo, the cutoff wavenumber of the magnetic energy spectra scales as expected for large magnetic Prandtl numbers, but continues in the same way also for moderately small values - contrary to what is expected. For a critical magnetic Prandtl number of about 0.3, the dissipative and resistive cutoffs are found to occur at the same wavenumber. In the nonlinearly saturated regime, the critical magnetic Prandtl number becomes unity. The cutoff scale now has a shallower scaling with magnetic Prandtl number below a value of about three, and a steeper one otherwise compared to the kinematic regime.
