非平衡分布等离子体中调制坍塌动力学研究

发布时间：2018-07-16 22:02

【摘要】：探索等离子体湍动的诱发机制和描述等离子体的湍动演化是等离子体物理的重要课题。基于Zakharov模型,研究等离子体中湍动物理现象,如太空中观测到的朗缪尔振幅调制和激光等离子体中的孤立波等。研究表明,等离子体中多尺度耦合非线性相互作用极易诱发等离子体湍动,调制不稳定性是诱发等离子体波不稳定的重要因素,其中非线性调制坍塌是导致等离子体湍动串级的重要机制之一。此外在天文观测和实验室等离子体中观察到的快电子爆发和耀斑现象,这些现象不能被现有的统计分布所描述。因此,本文基于天体和激光等离子体中的非平衡分布,研究其中波-波和波-粒非线性相互作用诱发的调制坍塌过程,获得其中的物理演化图像和特征量,将能为相关实验和观测研究提供理论参考。首先,基于Kappa分布等离子体中的自生磁场控制方程,分析了Kappa分布等离子体中波-波和波-粒相互作用诱发的低频非线性流。采用差分法研究准静态极限下的自生磁场的坍塌动力学演化图像以及分析了超热电子对非线性湍动问题的影响。结果表明调制不稳定性将导致低频电磁包络场坍塌,局部高涨的有质动力使得等离子体密度局部稀化,等离子体形成局域化非线性腔体结构;自生电磁包络场演化成高度局域化的湍动磁流;超热指数会影响坍塌的特征时标,当超热指数很小的时候,即超热粒子越多系统的自由能越大的时候,随着超热粒子的增多使得自生磁场坍塌加快,强度变强,局域化越明显。其次,基于流体理论,采用双时标的方法,从理论上导出了描述双温电子等离子体中朗缪尔波、电磁波和电声波之间波-波非线性相互作用双温电子-Zakharov方程。通过采用数值差分法对该控制方程进行了求解。结果表明朗缪尔波、电磁波和电声波是调制不稳定的,电磁场最终坍塌成高度局域化的非线性结构;同时朗缪尔波由小波数向大波数转移,形成湍动花样;电声波最终塌缩成腔子结构,由于其具有很高的能量及特征时标与电子匹配,将能有效地加速电子。另一方面,采用差分方法数值研究了在广义Zakharov方程系统中驻波形式解的演化规律。数值结果表明,电场波包在x方向的分量上呈现驻波振幅调制的演化规律,在y方向分量上呈现双极子振荡结构;最终它们都会经历非线性坍缩形成高度局域化的腔子结构。此外,利用数值计算方法研究了广义非线性薛定谔方程,即由广义Zakharov方程退化的标量形式方程,此方程一般是用来描述较低频的离子声波不稳定性的,分析了其中波场的调制、自散焦不稳定性以及湍流现象。结果表明,不管有没有外加势场,在复数薛定谔方程系统情况下会发生自散焦不稳定性;频谱空间上都是由小波数向大波数转移最后形成湍动;最终的系统总能量都趋于稳定;在有外势的情况下自散焦不稳定性的增长将会受到抑制,而无外势的情况下,自散焦的不稳定性增长率明显较大。
[Abstract]:Exploring the induced mechanism of plasma turbulence and describing the turbulent evolution of plasma is an important topic in plasma physics. Based on the Zakharov model, we study the turbulent physical phenomena in plasma, such as the Langmuir amplitude modulation in space and the solitary waves in the laser plasma. The nonlinear interaction is very easy to induce plasma turbulence, and the modulation instability is an important factor to induce the instability of plasma waves, in which the nonlinear modulation collapse is one of the important mechanisms leading to the cascade of plasma turbulence. In addition, the fast electron burst and flare observed in the astronomical observation and laboratory plasma are in addition to the phenomenon of the rapid electron burst and flare. Some phenomena can not be described by the existing statistical distribution. Therefore, based on the nonequilibrium distribution in the celestial and laser plasma, this paper studies the modulation collapse induced by wave wave and wave particle nonlinear interaction, and obtains the physical evolution images and characteristic quantities, and will be able to provide theoretical reference for the related experiments and observation research. Firstly, based on the control equation of the spontaneous magnetic field in the Kappa distributed plasma, the low-frequency nonlinear flow induced by wave wave and wave particle interaction in the Kappa distributed plasma is analyzed. The evolution image of the collapse dynamics of the autogenic magnetic field under quasi static limit is studied by the difference method and the shadow of the super thermal electron to the nonlinear turbulence problem is analyzed. The results show that the modulation instability will result in the collapse of the low frequency electromagnetic envelope field. The locally high mass force makes the plasma density partially dilute, the plasma formed localized nonlinear cavity structure, the spontaneous electromagnetic envelope field evolves into a highly localized turbulent magnetic flux, and the SUPERTHERMAL index will affect the characteristic time mark of the collapse, when the superheat is superheated. When the exponent is very small, the more free energy of the system is more hot, the more the free energy of the system increases. With the increase of the super hot particles, the autogenic magnetic field collapses faster, the intensity becomes stronger and the localization is more obvious. Secondly, based on the theory of fluid, the Langmuir wave, electromagnetic wave and electromagnetic wave in the dual temperature electron plasma are derived from the theory of double time scale. The two temperature electronic -Zakharov equation of wave wave wave non linear interaction between electric waves is solved by using numerical difference method. The result shows that the Muir wave, electromagnetic wave and electroacoustic wave are unstable, and the electromagnetic field collapses into a highly localized nonlinear structure. At the same time, the Langmuir wave is from the wavelet number to the large wave. There is a number transfer to form a turbulent pattern; the electroacoustic wave eventually collapses into a cavity structure. Because of its high energy and characteristic time, it can effectively accelerate the electron. On the other hand, the evolution law of the standing wave form solution in the generalized Zakharov equation system is numerically studied by the difference method. The numerical results show that the electric field wave is wrapped in X. The direction component presents the evolution law of the amplitude modulation of the standing wave, and presents the bipolar oscillating structure in the Y direction component. Finally, they all experience nonlinear collapse to form a highly localized cavity structure. In addition, the generalized nonlinear Schrodinger square, which is the scalar form degenerated by the generalized Zakharov equation, is studied by the numerical method. This equation is generally used to describe the instability of the relatively low frequency ion acoustic wave. The modulation, self defocusing instability and turbulence phenomena in the wave field are analyzed. The results show that the defocusing instability will occur in the complex Schrodinger equation system, regardless of the external potential field, and the spectrum space is all from the wavelet number to large. The wave number transfer finally forms the turbulence; the total energy of the final system tends to be stable; the growth of self defocus instability will be suppressed in the case of external potential, and the growth rate of self defocus is significantly higher without the external potential.
【学位授予单位】：南昌大学
【学位级别】：博士
【学位授予年份】：2017
【分类号】：O53

【相似文献】