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本文得到了高低频、双流体、无外磁场,初始密度为均匀时,等离子体动力学方程组的一个双向一维平面高频横波(光波)和纵波(Langmuir波)耦合的孤立波系,它的离子密度凹陷的深度和宽度与实验结果基本一致。这种耦合的孤立波与单独的光孤立波或Langmuir孤立波比较,表现出若干新的性质。 相似文献
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通过理论研究与数值计算,不均匀等离子体中Langmuir波与电磁波的相互作用及其线性模式转换规律得到了充分的展示.导出了不均匀等离子体中的电磁色散关系,研究了入射电磁波或Langmuir波在通过不均匀等离子体的过程中发生转换的物理过程,以及波的传播矢量随空间坐标变化的关系,并对电磁波与Langmuir波相互作用的机理进行了讨论.研究结果对密度梯度所驱动的等离子体波产生电磁辐射的研究具有重要意义.
关键词:
电磁波
Langmuir波
不均匀等离子体
线性模式转换 相似文献
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对长度为45 cm的短放电管螺旋波放电等离子体进行了Langmuir探针、原子发射光谱以及集成电荷耦合检测器(ICCD)检测诊断,研究螺旋波等离子体的放电特性.Langmuir探针数据显示电子密度在射频功率增加过程中出现两次大幅增长,由此确认了放电模式的转换及螺旋波放电模式的出现.发射光谱测量结果与Langmuir探针测量的电子密度数据一致,发现Ar原子和Ar离子的谱线强度与放电模式变化有着密切相关性.而通过对不同放电模式的ICCD测量,获得射频功率吸收因放电模式转变而变化的方式,认为放电模式转换时电子行为和能量传递方式也发生着变化. 相似文献
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波片精度对偏振光学系统性能有着重要的影响,故需要对其相位延迟量和快轴方位角进行高精度测量。提出了一种新型基于双频激光干涉相位检测的高精度波片测量方法,采用双频激光外差干涉光路,利用一个可旋转半波片和一个角锥反射棱镜测量待测波片,可实现任意波片的相位延迟量和快轴方位角的高精度同时测量。所提方法不受波片、偏振片等双折射器件的方位角精度的影响,从原理上避免了该类系统误差。所设计的系统具有共光路结构,测量稳定性高,信号处理采用相位检测方式相对于一般的光强检测方式测量精度更高。此外,所设计的测量系统中元件很少,结构简单,测量过程快捷。误差分析表明,在现有实验条件下,测量系统的波片相位延迟量的测量不确定度约为3.9′,快轴方位角的测量不确定度约为5′′。实验比对结果表明,所提方法的测量结果与其他方法测量结果的一致性很好。重复性测量实验表明,测量结果的标准偏差约为2′。 相似文献
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Kinetic simulations of backward stimulated Raman scattering (BSRS), where the Langmuir wave coherence time is greater than the bounce time for trapped electrons, yield transient reflectivity levels far above those predicted by fluidlike models. Electron trapping reduces the Langmuir wave damping and lowers the Langmuir wave frequency, and leads to a secular phase shift between the Langmuir wave and the BSRS beat ponderomotive force. This phase shift detunes and saturates BSRS and a similar effect, due to ion trapping, is the saturation mechanism for backward stimulated Brillouin scattering. Competition with forward SRS is discussed. 相似文献
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Pulse broadening and two-frequency mutual coherence function of the scattered wave from rough surfaces 总被引:4,自引:0,他引:4
Akira Ishimaru Lynn Ailes-sengers Phillip Phu Dale Winebrenner 《Waves in Random and Complex Media》1994,4(2):139-148
Analytical expressions for the two-frequency mutual coherence function and angular correlation function of the scattered wave from rough surfaces based on the Kirchhoff approximation are presented. The coherence bandwidth depends on the illumination area as well as on the incident and scattered angles and the surface characteristics. Scattered pulse shapes are calculated as the Fourier transform of the two-frequency mutual coherence function. Calculations based on analytical solutions are compared with millimetre wave experimental data and Monte Carlo simulations showing good agreement. 相似文献
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K. Furutsu 《Waves in Random and Complex Media》1993,3(3):157-175
An exact functional integral representation for the two-point intensity correlation function was previously obtained by the author for a collimated beam wave by solving the moment equation. The variable functions of integration involved therein can be effectively limited to a set of functions determined so that the entire phase term of the integrand becomes stationary against arbitrary variation of the variable functions, exactly according to the Lagrange variational principle in dynamics. The result is free from any expansion and is presented with a set of unperturbed equations of closed form. When making a formal expansion, it leads to the zeroth- and first-order expressions similar to those obtained by an improved two-scale method. With exactly the same procedure, the three-point intensity correlation and the two-frequency intensity correlation were also obtained.The Lagrange method leads to the 'equation of motion' subjected to boundary conditions to continue the phase term from the incident beam wave. The boundary conditions were previously found based on a physical reasoning, while the same conditions are found here purely based an the variational principle. A focused beam wave is assumed for the incident wave, including both spherical and plane waves as special cases. 相似文献
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Albert C. Fannjiang 《Journal of statistical physics》2005,120(3-4):543-586
We introduce two-frequency Wigner distribution in the setting of parabolic approximation to study the scaling limits of the
wave propagation in a turbulent medium at two different frequencies. We show that the two-frequency Wigner distribution satisfies
a closed-form equation (the two-frequency Wigner–Moyal equation). In the white-noise limit we show the convergence of weak
solutions of the two-frequency Wigner–Moyal equation to a Markovian model and thus prove rigorously the Markovian approximation
with power-spectral densities widely used in the physics literature. We also prove the convergence of the simultaneous geometrical
optics limit whose mean field equation has a simple, universal form and is exactly solvable 相似文献
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《Waves in Random and Complex Media》2013,23(2):139-148
Abstract Analytical expressions for the two-frequency mutual coherence function and angular correlation function of the scattered wave from rough surfaces based on the Kirchhoff approximation are presented. The coherence bandwidth depends on the illumination area as well as on the incident and scattered angles and the surface characteristics. Scattered pulse shapes are calculated as the Fourier transform of the two-frequency mutual coherence function. Calculations based on analytical solutions are compared with millimetre wave experimental data and Monte Carlo simulations showing good agreement. 相似文献
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《Waves in Random and Complex Media》2013,23(3):157-175
Abstract An exact functional integral representation for the two-point intensity correlation function was previously obtained by the author for a collimated beam wave by solving the moment equation. The variable functions of integration involved therein can be effectively limited to a set of functions determined so that the entire phase term of the integrand becomes stationary against arbitrary variation of the variable functions, exactly according to the Lagrange variational principle in dynamics. The result is free from any expansion and is presented with a set of unperturbed equations of closed form. When making a formal expansion, it leads to the zeroth- and first-order expressions similar to those obtained by an improved two-scale method. With exactly the same procedure, the three-point intensity correlation and the two-frequency intensity correlation were also obtained.The Lagrange method leads to the ‘equation of motion’ subjected to boundary conditions to continue the phase term from the incident beam wave. The boundary conditions were previously found based on a physical reasoning, while the same conditions are found here purely based an the variational principle. A focused beam wave is assumed for the incident wave, including both spherical and plane waves as special cases. 相似文献
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A. I. Matveev 《Russian Physics Journal》2010,53(4):369-380
Nonlinear damping of the Langmuir wave in a weakly inhomogeneous plasma with a negative concentration gradient is considered.
For phase velocities close to the thermal velocity of electrons, their dispersion strongly differs from the linear one and
cannot be taken into account by means of a small correction to the linear dispersion law. Based on the energy balance and
nonlinear dispersion equations, a dependence of the wave amplitude on its phase velocity is established together with the
limiting phase velocity at which the wave is completely damped. 相似文献
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Evolution of a Langmuir wave is studied numerically for finite amplitudes slightly above the threshold which separates damping from nondamping cases. Arrest of linear damping is found to be a second-order effect due to ballistic evolution of perturbations, resonant power transfer between field and particles, and organization of phase space into a positive slope for the average distribution function f(av) around the resonant wave phase speed nu(ph). Near the threshold trapping in the wave potential does not arrest damping or saturate the subsequent growth phase. 相似文献
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激光等离子体中的强朗缪尔湍动谱分析 总被引:3,自引:1,他引:2
通过数值计算完全的萨哈罗夫方程,得到了朗缪尔波能量密度谱图。从一系列的谱图中可以看出,波的塌缩过程是沿着能量密度谱由小波数区域向大波数区域转移,朗缪尔波在塌缩过程中出现成丝现象。通过对获得的朗缪尔波平均能量密度谱进行拟合,得到了朗缪尔波能量密度谱函数。 相似文献