Abstract

In the present work, we investigate modulational instability (MI) in an unmagnetised collisionless electronegative plasma consisting of inertialess adiabatic electrons, inertialess adiabatic negative ions and mobile positive ions. For this purpose, a nonlinear Schrodinger equation (NLSE) is derived to study envelope evolution of the ion-acoustic carrier waves for our system by using reductive perturbation technique. In examining the stability/instability of the ion-acoustic envelope wavepackets, the critical wavenumber k_c at which MI sets in is found to be shifted to higher values as adiabaticity γ increases. The effects of electron-to-negative ion temperature ratio σ_n and negative ion density fraction f on the region for propagation of stable wave pulses are also discussed. Within the instability region, the rational solution of NLSE provides the rogue wave (RW) profiles which is localised in space and time. With the increase of adiabaticity, the possibility for the formation of RW decreases at the lower wavenumber which is in good agreement with experimental observations. The change in adiabaticity significantly influences the rogue wave amplitudes. Maximum pulse height for RW is found to be increasing with the increase of adiabaticity. Our theoretical findings may be helpful for basic characteristic study of rogue waves in the laboratory as well as space plasmas.

Graphical abstract

中文翻译：

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电子和负离子的绝热性对负电等离子体中离子声波调制不稳定性的影响

摘要

在本工作中，我们研究了由无惯性绝热电子，无惯性绝热负离子和移动性正离子组成的非磁化无碰撞无负电等离子体的调制不稳定性（MI）。为此目的，使用还原摄动技术推导了非线性薛定inger方程（NLSE），以研究系统中离子声载波的包络线演化。在检查离子声包络波包的稳定性/不稳定性时，发现随着绝热系数γ的增加，MI进入的临界波数k _c会移到更高的值。电子至负离子温度比的影响σ _Ñ和负离子密度级˚F还讨论了在稳定波脉冲传播区域的问题。在不稳定区域内，NLSE的合理解提供了流浪（RW）轮廓，该轮廓在空间和时间上局部化。随着绝热性的增加，在较低波数下形成RW的可能性降低，这与实验观察结果非常吻合。绝热的变化显着影响流浪振幅。发现RW的最大脉冲高度随着绝热性的增加而增加。我们的理论发现可能对实验室流氓波以及空间等离子体的基本特性研究有所帮助。

图形概要