具有强剪切流等离子体中离子声波与涡旋的转化

研究了在具有剪切本底流的非磁化等离子体中离子声波的激发及其与涡旋的转化。从流体方程组出发，导出了描述低频静电扰动的微分方程组。采用非模方法，得到了扰动量的剪切傅里叶谐波分量随时间演化的方程组，并对方程组进行了数值分析。结果表明：在强剪切条件下，剪切旋涡可以转化为离子声波；同样地，离子声波也激发剪切旋涡。     

受激布里渊散射的非线性增强和饱和

针对典型激光聚变等离子体参数条件，利用弗拉索夫程序研究非均匀流等离子体中受激布里渊散射的非线性行为。在动理学效应占主导的参数区域，观察到受激布里渊散射激发的离子声波由于非线性动理学频移和非均匀流空间失谐相互补偿引起的离子声波自共振增长，这会导致受激布里渊水平量级的增强；提出用光束时间去相干抑制这种绝对增长。在流体非线性占主导的参数区域，观察到由于离子声波谐波导致的孤立波产生、离子加热以及受激布里渊散射饱和现象。     

强激光与等离子体相互作用中受激陷俘电子声波散射及相空间离子涡旋的形成

应用一维相对论电磁粒子模拟程序，研究了线性极化强激光入射到无碰撞密度均匀的次临界密度等离子体中所引起的受激陷俘电子声波散射不稳定性过程.不稳定性的早期行为与是否考虑离子动力学效应无关.当考虑离子动力学效应之后会激发一个随时间增长的离子声波，并且最终由于大振幅电磁孤立子的产生而中断.由于电磁孤立子内的静电场与电磁场所产生的离子加速与俘获效应，导致一个离子涡旋在离子相空间中形成；当电磁孤立子向后加速过程中，若干个离子涡旋结构随之形成.研究发现，离子涡旋结构同样存在于密度不均匀的次临界密度等离子体中.从拓扑的观 关键词： 粒子模拟 受激陷俘电子声波散射 电磁孤立子 离子涡旋     

离子与尘埃相互作用对离子声波和尘埃声波的影响

基于流体力学方程和与时间相关的线性微扰理论,分析了尘埃等离子体环境中离子与尘埃粒子的相互作用对离子声波和尘埃声波的影响,结果表明两者间的相互作用使得离子声波变得稳定而使尘埃声波变得不稳定。     

利用离子声波朗道阻尼测量氧化物阴极放电中的离子温度

作为等离子体重要参数之一, 特别是在低温等离子体中离子温度的测量一直较为困难. 在磁化线性等离子体装置氧化物阴极脉冲放电条件下, 利用栅网激发离子声波, 通过测量波幅在朗道阻尼作用下随空间的演化, 利用阻尼长度是离子温度和电子温度的函数, 计算得到离子温度为0.3 eV. 测量值与国外类似装置利用光谱诊断所得结果基本相同.     

离子声波对电子输运的影响

从Balescu-Lenard碰撞项出发,得到了电子-电子通过交换离子声波对碰撞的贡献项,并计算了电子输运(热导)系数.计算结果表明,由于离子声波的作用电子热导系数有所下降 关键词： 电子输运 离子声波 Balescu-Lenard方程     

多尺度等离子体动力学数值模拟中最初的无方程投影积分技术

发展一种针对等离子体多尺度问题的"最初的无方程投影积分(p-EFPI)"方法并成功应用于离子声波的模拟.该方法包括时间推进和时间投影两部分.电子速度通过概率分布函数或累积分布函数投影外推,电子位置坐标则通过投影外推的电子电荷密度重新调出;与电子相比,假设粗糙的离子运动可以很好地描述宏观尺度等离子体的演化行为,通过追踪和投影外推每个离子轨道保持全部离子运动学效应.尝试和检验p-EFPI方法在模拟等离子体物理现象中的应用.以离子声波为范例,数值计算表明:在离子相空间出现离子捕获效应前,p-EFPI模拟能够很好地再现PIC的结果,在离子捕获发生后,p-EFPI模拟仍然可以抓住除了离子捕获特征之外的其它主要物理特征.     

Mn掺杂ZnO柱的结构及光学性质

采用电化学沉积方法在Si(111)衬底上制备出了Mn掺杂的ZnO柱,长度约为500~600 nm,直径为200~300 nm。通过XRD和XPS的表征可以判断出:Mn2+离子代替部分Zn2+离子进入了ZnO晶格,Mn离子的掺杂量为2%。样品的共振拉曼谱表明:由于Mn2+离子进入了晶格,导致ZnO的1LO和2LO光学纵向声子向高频移动。在He-Cd激光器325 nm激发下,可以观测到光谱中存在两个发光谱带,分别位于可见区和紫外区。     

高频波激发低频磁场和离子声波的重整化强湍动理论

本文给出了高温等离子体中高频波激发低频磁场和离子声波强湍动过程的重整化理论,以便改善通常的弱非线性处理方法,从Vlasov-Maxwell方程组出发,在Fourier表象中得到了包含“最发散”和“次发散”效应互相耦合的高频和低频传播于重整化方程组,从而获得了高、低频振荡粒子重整化分布函数和场的耦合关系。在“最发散”重整化近似下,我们求解了高低频传播子方程组,得到了展开到v₄(高频湍动场能密度与等离子体热能密度之比)一次方的近似解和重整化介电函数等表达式。然后,在Fourier逆变换下导得了我们所要的时空表用中重整化强湍动方程组。最后,作为一个说明重整化作用的例子,在一维稳态下求解了孤立子的形式。 关键词：     

光衍射法观测叉指换能器在石英晶体中激发的各种声波

利用声光相互作用所引起的光衍射现象,观测了叉指换能器在石英晶体上激发的各种声波及其倒速度图。着重研究了z-切割石英晶体表面、沿y方向激发表面声波的叉指换能器在这个样品上激发的各种表面声波和体声波。对观察到的不同于瑞利波形式的表面声波进行了探讨,并说明这类波的特性值得进一步研究。     

Ion acoustic waves in the presence of electron plasma waves

Long-wavelength ion acoustic waves in the presence of propagating short-wavelength electron plasma waves are examined. The influence of the high frequency oscillations is to decrease the phase velocity and the damping distance of the ion wave.     

Linear Analysis of Obliquely Propagating Longitudinal Waves in Partially Spin Polarized Degenerate Magnetized Plasma

Linear analysis of low frequency obliquely propagating electrostatic waves in a partially spin polarized degenerate magnetized plasma is presented. Using Fourier analysis, a general linear dispersion relation is derived for low frequency electrostatic lower hybrid(LH) wave, ion acoustic(IA) wave and ion cyclotron(IC) wave in the presence of electron spin polarization. It is found that the electron spin polarization gives birth to a new spin-dependent wave(spin electron acoustic wave) in the spectrum of these waves. Further, the electron spin polarization also causes drastic shifts in the frequency spectrum of these waves. These effects would have a strong bearing on wave phenomena in degenerate astrophysical plasmas.     

Electrostatic waves in a paired fullerene-ion plasma

Three kinds of electrostatic modes are experimentally observed to propagate along magnetic-field lines for the first time in the pair-ion plasma consisting of only positive and negative fullerene ions with an equal mass. It is found that the phase lag between the density fluctuations of positive and negative ions varies from 0 to pi depending on the frequency for ion acoustic wave and is fixed at pi for an ion plasma wave. In addition, a new mode with the phase lag about pi appears in an intermediate-frequency band between the frequency ranges of the acoustic and plasma waves.     

Low frequency waves in a positive column of discharge

The propagation of longitudinal low frequency waves in the plasma of the positive column of a d.c. glow discharge is studied theoretically. The dispersion characteristics are obtained for conduction, ion acoustic and neutral acoustic waves. Equations are solved numerically and the results are compared with other theories and measurements.     

Ion acoustic waves excited by boundary sheaths

Low frequency signals applied to a grid immersed in a plasma excite ion acoustic waves at the plasma boundaries simulataneous with those excited at the grid. A mechanism is suggested which involves the “direct coupled signal”.     

Ionenschallinstabilitäten in Edelgas-Gleichstromentladungen bei niedrigen Drücken. II. Vergleich der experimentellen Ergebnisse mit einer eindimensionalen kinetischen Dispersionstheorie

The experimental measurements of the propagation properties of self-exicted ion acoustic waves in a de-low pressure column are compared with a one dimensional dispersion theory. The corresponding dispersion relation is developed starting from the linearised Vlasov equation with a Davydov-type collision term. It is shown, that the mean features of the propagation behaviour of the ion acoustic waves can be explained by the theory. The experimental results concerning the dependence of the upper limit frequency of the waves upon the discharge current should be analysed on the base of new results from plasma diagnostics, taking also into account nonlinear and geometrical effects.     

Impact of electron exchange-correlation on drift acoustic solitary waves

The impact of electron exchange-correlation term on the linear and nonlinear quantum ion (QIA) acoustic drift waves in a highly degenerate plasma is investigated. An analytical approach is employed to derive the differential equation which is later on turned into Sagdeev energy integral equation that can be utilized to get drift solitons under existence conditions. It is noted that phase speed/frequency of the linear drift quantum ion acoustic (QIA) waves increases with electron exchange-correlation effect, but the amplitude of the corresponding solitons decreases with inclusion of these effects. Present study is carried out with reference to highly dense plasma environments like fast ignition inertial confinement fusion and white dwarfs etc.     

Propagation of electrostatic energy through a quantum plasma

The theory of propagation of electrostatic energy through an infinite, homogeneous electron–ion quantum plasma is presented. Simple expressions for the energy flow, energy density, and energy velocity of longitudinal oscillation waves in the system are derived using the linearized quantum hydrodynamic theory for the electron fluid, which incorporates the important quantum statistical pressure and electron diffraction force, while the optical response of the ion particles is characterized by the classical frequency‐dependent dielectric function, ?_ion. Both cases of plasmon (high‐frequency) and quantum ion‐acoustic (low‐frequency) waves are considered.     

Parametric excitation by a pump magnetic field in a high temperature plasma

The parametric growth rates of Alfvén waves, fast compressional waves and ion acoustic waves excited by a time modulated magnetic field are calculated for the case of a high temperature plasma with anisotropic pressure. The plasma is described by the C.G.L. model.     

Nonlinear Electrostatic Ion‐Acoustic Waves in the Solar Atmosphere

Basing on recent solar models, the excitation of ion‐acoustic turbulence in the weakly‐collisional, fully and partially‐ionized regions of the solar atmosphere is investigated. Within the frame of hydrodynamics, conditions are found under which the heating of the plasma by ion‐acoustic type waves is more effective than the Joule heating. Taking into account wave and Joule heating effects, a nonlinear differential equation is derived, which describes the evolution of nonlinear ion‐acoustic waves in the collisional plasma.