ON LARGE-SCALE DYNAMO ACTION AT HIGH MAGNETIC REYNOLDS NUMBER
ON LARGE-SCALE DYNAMO ACTION AT HIGH MAGNETIC REYNOLDS NUMBER
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DOI：
10.1088/0004-637x/789/1/70
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发表时间：
2014-05
期刊：
影响因子：
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通讯作者：
F. Cattaneo;S. Tobias
中科院分区：
文献类型：
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作者：
F. Cattaneo;S. Tobias
我们考虑的产生的磁活动发电机波的天体物理极限的非常大的磁雷诺数。我们考虑了由螺旋流和大尺度剪切组成的系统的运动发电机作用。我们表明，大规模的发电机波坚持在高Rm的螺旋流的特点是由一个狭窄的空间尺度和剪切足够大的频带。然而，对于一个宽频带的规模的发电机成为小规模的进一步增加的RM，与发电机波重新出现，只有当剪切然后增加。我们表明，在高RM，剪切的关键作用是抑制小规模的发电机行动，允许大规模的发电机行动进行观察。我们推测，这支持一个一般的“抑制原则”-大规模发电机行动只能观察到，如果有一个机制，抑制小规模的波动。
We consider the generation of magnetic activity—dynamo waves—in the astrophysical limit of very large magnetic Reynolds number. We consider kinematic dynamo action for a system consisting of helical flow and large-scale shear. We demonstrate that large-scale dynamo waves persist at high Rm if the helical flow is characterized by a narrow band of spatial scales and the shear is large enough. However, for a wide band of scales the dynamo becomes small scale with a further increase of Rm, with dynamo waves re-emerging only if the shear is then increased. We show that at high Rm, the key effect of the shear is to suppress small-scale dynamo action, allowing large-scale dynamo action to be observed. We conjecture that this supports a general “suppression principle”—large-scale dynamo action can only be observed if there is a mechanism that suppresses the small-scale fluctuations.