Zonal flow generation by modulational instability
Zonal flow generation by modulational instability
复制标题
通过调制不稳定性产生分区流
DOI：
10.1142/9789812771025_0017
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发表时间：
2006
期刊：
影响因子：
--
通讯作者：
R. F. Abdullatif
中科院分区：
文献类型：
--
作者：
R. Dewar;R. F. Abdullatif
本文对通过等离子体漂移波或罗斯贝波的非线性相互作用激励纬向流的包络形式进行了教学回顾，分别用长谷川-美马 (HM) 方程或准地转正压位涡方程等效描述。在等离子体情况下，还分析了 HM 方程的修改形式，该方程考虑了通过少量旋转变换对磁表面平均电子密度响应的抑制。在修改的 HM 情况下，调制波列对纬向平均流的激励特别强。通过对背景平均流进行线性化来计算相干波列的局部色散关系，并用于通过插入非线性激励平均流来找到非线性频移。使用关于均匀载波的通用非线性薛定谔方程，找到了波列小调制的不稳定性标准，以及在修改和未修改的情况下调制和层流的最大增长率和相速度。
This paper gives a pedagogic review of the envelope formalism for excitation of zonal flows by nonlinear interactions of plasma drift waves or Rossby waves, described equivalently by the Hasegawa-Mima (HM) equation or the quasigeostrophic barotropic potential vorticity equation, respectively. In the plasma case a modified form of the HM equation, which takes into account suppression of the magnetic-surface-averaged electron density response by a small amount of rotational transform, is also analyzed. Excitation of zonal mean flow by a modulated wave train is particularly strong in the modified HM case. A local dispersion relation for a coherent wave train is calculated by linearizing about a background mean flow and used to find the nonlinear frequency shift by inserting the nonlinearly excited mean flow. Using the generic nonlinear Schroedinger equation about a uniform carrier wave, the criterion for instability of small modulations of the wave train is found, as is the maximum growth rate and phase velocity of the modulations and zonal flows, in both the modified and unmodified cases.