Freak waves in laboratory and space plasmas
Freak waves in laboratory and space plasmas
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DOI：
10.1140/epjst/e2010-01238-7
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发表时间：
2010-08
期刊：
影响因子：
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通讯作者：
M. Ruderman
中科院分区：
文献类型：
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作者：
M. Ruderman
讨论了等离子体中小振幅初始扰动产生大振幅短寿命波群的问题。考虑等离子体中存在的两种特定波模式。第一个是离子声波。在带有负离子的等离子体中，当负离子浓度接近临界值时，可以通过加德纳方程来描述。给出了具有调制不稳定初始条件的加德纳方程的数值求解结果。这些结果清楚地表明由于调制不稳定性而可能产生异常离子声波。第二种波型是阿尔文波。当该波相对于平衡磁场以小角度传播且其波长与离子惯性长度相当时，可以用DNLS方程描述。使用线性化 DNLS 方程研究初始扰动的演化表明，由于线性色散聚焦，可能会产生异常的阿尔文波。 DNLS方程的数值解表明非线性色散聚焦也会产生反常的阿尔文波。
Generation of large-amplitude short-lived wave groups from small-amplitude initial perturbations in plasmas is discussed. Two particular wave modes existing in plasmas are considered. The first one is the ion-sound wave. In a plasmas with negative ions it is described by the Gardner equation when the negative ion concentration is close to critical. The results of numerical solution of the Gardner equation with the modulationally unstable initial condition are presented. These results clearly show the possibility of generation of freak ion-acoustic waves due to the modulational instability. The second wave mode is the Alfvén wave. When this wave propagates at a small angle with respect to the equilibrium magnetic field, and its wave length is comparable with the ion inertia length, it is described by the DNLS equation. Studying the evolution of an initial perturbation using the linearized DNLS equation shows that the generation of freak Alfvén waves is possible due to linear dispersive focusing. The numerical solution of the DNLS equation reveals that the nonlinear dispersive focusing can also produce freak Alfvén waves.