共查询到20条相似文献,搜索用时 15 毫秒
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A theoretical study is made on the generation mechanism of Langmuir mode wave in the presence of kinetic Alfvén wave turbulence
in a magnetized plasma on the basis of plasma-maser interaction. It is shown that a test high frequency Langmuir mode wave
is unstable in the presence of low frequency kinetic Alfvén wave turbulence. The growth of the Langmuir wave occurs due to
direct and polarization coupling terms. Because of the universal existence of the kinetic Alfvén waves in large scale plasmas,
the results have potential importance in space and astrophysical radiation processes. 相似文献
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基于修正Rytov理论,导出了适应于强湍流起伏区的光束漂移方差表达式,分析了湍流外尺度、有效散射区域尺度和光束束腰对光束漂移的影响,并与实验结果进行了比较。结果表明,相对于基于指数模型的光束漂移方差表达式,基于修正Rytov理论给出的表达式的计算结果能更好地与实验结果吻合。当光束束腰大于有效散射区域尺度时,不发生饱和效应,导出的表达式与传统理论给出的表达式一致;当光束束腰小于有效散射区域尺度时,光束漂移的幅度不随Rytov方差的增大而明显变化。 相似文献
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Based on the modified spectrum, the analytic expressions for the
variance and normalized covariance of angle-of-arrival (AOA)
fluctuations are presented, which are applicable to the weak and
strong regimes. The experimental data of AOA fluctuations validate
the new derived expressions in weak and strong regimes. The results
show that the receiving aperture D, outer scale and cell scale
larger than the scattering disc S contribute significantly to the
AOA fluctuations, and contributions from the small-scale turbulence
are negligible. For the case of 4S/D\ll 1, the receiving aperture
dominates low-pass filtering effects and the new displacement
variances are in good agreement with the results from the
old weak-fluctuation theory. For the case of 4S/D\gg 1, the scattering disc dominates the low-pass
filtering effects and the new displacement variances depart from the
results from the old
weak-fluctuation theory. 相似文献
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Power spectra of fluctuations in strong Langmuir turbulence 总被引:1,自引:0,他引:1
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Nucleation and transients at the onset of vortex turbulence 总被引:1,自引:0,他引:1
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Nonlinear coupling between Langmuir waves with finite amplitude dispersive dust acoustic perturbations is considered. It is shown that the interaction is governed by a pair of coupled nonlinear differential equations. Numerical results reveal the formation of Langmuir envelope solitons composed of the dust density depression created by the ponderomotive force of bell-shaped Langmuir wave envelops. The associated ambipolar potential is positive. The present nonlinear theory should be able to account for the trapping of large amplitude Langmuir waves in finite amplitude dust density holes. This scenario may appear in Saturn's dense rings, and the Cassini spacecraft should be able to observe fully nonlinear cavitons, as presented herein. Furthermore, we propose that new electron-beam plasma experiments should be conducted to verify our theoretical prediction. 相似文献
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L. N. Vyacheslavov V. S. Burmasov I. V. Kandaurov É. P. Kruglyakov O. I. Meshkov A. L. Sanin 《JETP Letters》2002,75(1):41-54
The regime of strong Langmuir turbulence characterized by the plasma nonisothermality and by the presence of an appreciable non-Maxwellian hot-electron component was experimentally studied. Turbulence was excited in the preliminary produced plasma by the relativistic electron beam. Thomson scattering of laser IR radiation served as the main diagnostic method. The spatial spectra of the Langmuir turbulence and of the attendant ion-sound turbulence were studied using Thomson collective scattering. Thomson incoherent scattering was used for studying the plasma electron distribution function and searching for the local dips of plasma density. Stark spectroscopy of turbulent microfields and the method of observation of plasma radiation at the double plasma frequency were also used. Based on the experimental data, the mechanism of Langmuir oscillation damping by plasma electrons was analyzed. The Langmuir wave conversion induced by the ion-sound turbulence is the most probable channel for energy transfer from the turbulence to plasma electrons, the low-frequency fluctuations being the direct consequence of the strong Langmuir turbulence. 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
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The field correlations of annular beams are formulated when the atmosphere assumes extremely strong turbulence. Thicker and larger ring sized annular beams are found to exhibit larger absolute field correlations. For the same transverse distance at the receiver plane, annular beams attain larger field correlations if the transverse distance starts from the receiver origin. Comparisons of the annular beam absolute field correlations in extremely strong turbulence with the no turbulence results show that the absolute field correlation variations follow similar trends, except that the magnitudes of the absolute field correlations are much smaller in extremely strong turbulence and the annular fields become decorrelated at very short transverse distances. When the inner scale of turbulence becomes smaller, the absolute field correlations of the annular beams in extremely strong turbulence become smaller. 相似文献
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In strong atmospheric turbulence, the asymptotic on-axis scintillation behaviors of Laguerre Gaussian (LG) beams are examined.
To arrive at the strong-turbulence solution, we utilize the existing filtering approach for weak-turbulence solutions and
our recently reported weak-turbulence scintillation index formula for LG beams. In the limiting case, our solution correctly
predicts the asymptotic strong-turbulence behavior of Gaussian beam wave scintillation. Investigation of the scintillations
versus the propagation distance, source size, wavelength and refractive index structure parameter lead to the conclusion that
the LG beams with higher order radial modes can provide less scintillation. The results are applicable to long-haul atmospheric
optical communication links. 相似文献
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M.J. Lavan 《Optics Communications》1976,16(3):359-361
An optical method for remotely determining the average crosswind under all conditions of atmospheric turbulence is proposed and analyzed. The method depends upon the phase structure function, which does not saturate with increasing range or strength of turbulence. The method also has the advantage that the path-weighting functions are almost constant over the entire path - in contrast to the highly selective path-weighting functions appropriate to remote wind-sensing using amplitude scintillations. 相似文献
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E. N. Sergeev V. L. Frolov G. N. Boiko G. P. Komrakov 《Radiophysics and Quantum Electronics》1998,41(3):206-228
The results of investigations of the temporal evolution of high-frequency plasma turbulence obtained by measurements of stimulated
ionospheric emission (SIE) features for different stages of interaction of powerful radio emission, with an ionospheric F
region plasma are presented. It is found that the relaxation time decreased up to 2–4 times with increase in the pump duration
and pumping power under the conditions of striction parametric instability (excitation of Langmuir plasma turbulence) over
times t≤2.00 ms. A similar decrease of the SIE relaxation time was also observed under the conditions of thermal parametric
instability (excitation of upper-hybrid plasma turbulence) in long-term quasicontinuous heating of ionospheric plasma. The
possible mechanisms of collisionless dissipation of plasma turbulence energy are discussed to explain the observed dependence
of the plasma wave damping rate on the temperal stage of development and intensity of plasma turbulence.
Radiophysical Research Institute, Nizhny Novgorod, Russia. Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Radiofizika,
Vol. 41, No. 3, pp. 313–347, March, 1998. 相似文献
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