ON THE SATURATION OF THE MAGNETOROTATIONAL INSTABILITY VIA PARASITIC MODES
ON THE SATURATION OF THE MAGNETOROTATIONAL INSTABILITY VIA PARASITIC MODES
复制标题
通过寄生模式论磁旋转不稳定性的饱和
DOI：
10.1088/0004-637x/698/1/l72
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发表时间：
2009
期刊：
影响因子：
--
通讯作者：
J. Goodman
中科院分区：
文献类型：
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作者：
M. Pessah;J. Goodman
我们研究了不可压缩的，精确的，非理想的磁旋转（MRI）模式对寄生不稳定性的稳定性。Kelvin-Helmholtz和撕裂模式寄生不稳定性都可能发生在当前数值模拟可访问的耗散制度。我们假设，一个主要的MRI模式饱和的幅度，使其最快的寄生虫具有与自己的增长率。预测的α参数，然后取决于最快的主模式和寄生模式是否适合在计算域内，以及是否允许非轴对称寄生模式。因此，即使是解决粘性和电阻尺度的模拟也可能不会适当地饱和，除非数值域足够大以允许MRI和寄生模式的自由演化。为了在具有垂直背景场的模拟中最低限度地满足这些要求，域的垂直范围应适应增长最快的MRI模式，而径向和方位角范围必须是其两倍大。最快的寄生虫的水平波长大约是主要的垂直波长的两倍。
We investigate the stability of incompressible, exact, non-ideal magnetorotational (MRI) modes against parasitic instabilities. Both Kelvin–Helmholtz and tearing-mode parasitic instabilities may occur in the dissipative regimes accessible to current numerical simulations. We suppose that a primary MRI mode saturates at an amplitude such that its fastest parasite has a growth rate comparable to its own. The predicted alpha parameter then depends critically on whether the fastest primary and parasitic modes fit within the computational domain and whether non-axisymmetric parasitic modes are allowed. Hence, even simulations that resolve viscous and resistive scales may not saturate properly unless the numerical domain is large enough to allow the free evolution of both MRI and parasitic modes. To minimally satisfy these requirements in simulations with vertical background fields, the vertical extent of the domain should accommodate the fastest growing MRI mode while the radial and azimuthal extents must be twice as large. The fastest parasites have horizontal wavelengths roughly twice as long as the vertical wavelength of the primary.