The modulational instability in the extended Hasegawa-Mima equation with a finite Larmor radius
The modulational instability in the extended Hasegawa-Mima equation with a finite Larmor radius
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DOI：
10.1063/1.4773050
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发表时间：
2012-12
影响因子：
2.2
通讯作者：
S. Gallagher;B. Hnat;C. Connaughton;S. Nazarenko;G. Rowlands
中科院分区：
文献类型：
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作者：
S. Gallagher;B. Hnat;C. Connaughton;S. Nazarenko;G. Rowlands
利用扩展形式的长谷川-米玛方程，研究了有限Larmor半径对四波调制不稳定性产生纬向流的影响。使用四模截断模型的解析预测以及非线性扩展的长谷川-米玛方程的直接数值模拟，量化了纬向模的增长率。我们不仅考虑了纯纬向流，而且还研究了一般的斜向情况，结果表明，对于较小的Larmor半径，离轴模可能成为主导。我们找到了一个关键参数Mρ，它描述了由于拉莫尔半径的变化而导致的系统行为。我们发现，与以前通过改变驱动波振幅得到的结果类似，可以访问两个不同的动力学区域。这对应于纬向流与驱动波和完全饱和的纬向流之间的振荡能量传递。
The effects of the finite Larmor radius on the generation of zonal flows by the four-wave modulational instability are investigated using an extended form of the Hasegawa-Mima equation. Growth rates of the zonal mode are quantified using analytical predictions from a four-mode truncated model, as well as from direct numerical simulation of the nonlinear extended Hasegawa-Mima equation. We not only consider purely zonal flows but also examine the generic oblique case and show that, for small Larmor radii, off-axis modes may become dominant. We find a key parameter Mρ which characterises the behaviour of the system due to changes in the Larmor radius. We find that, similarly to previous results obtained by changing the driving wave amplitude, two separate dynamical regimes can be accessed. These correspond to oscillatory energy transfer between zonal flows and a driving wave and the fully saturated zonal flow.