Field-reversed configurations in an unmagnetized plasma

An oscillating magnetic field is applied with a loop antenna to an unmagnetized plasma. At small amplitudes the field is evanescent. At large amplitudes the field magnetizes the electrons, which allows deeper field penetration in the whistler modes. Field-reversed configurations are formed at each half cycle. Electrons are energized. Transient whistler instabilities produce high-frequency oscillations in the magnetized plasma volume.     

Stirring unmagnetized plasma

A new concept for spinning unmagnetized plasma is demonstrated experimentally. Plasma is confined by an axisymmetric multicusp magnetic field and biased cathodes are used to drive currents and impart a torque in the magnetized edge. Measurements show that flow viscously couples momentum from the magnetized edge (where the plasma viscosity is small) into the unmagnetized core (where the viscosity is large) and that the core rotates as a solid body. To be effective, collisional viscosity must overcome the ion-neutral drag due to charge-exchange collisions.     

Head-on collision of ion-acoustic solitary waves in an unmagnetized electron-positron-ion plasma

The head-on collision between two ion-acoustic solitary waves in an unmagnetized electron-positron-ion plasma has been investigated. By using the extended Poincaré-Lighthill-Kuo perturbation method, we obtain the KdV equation and the analytical phase shift after the head-on collision of two solitary waves in this three-component plasma. The effects of the ratio of electron temperature to positron temperature, and the ratio of the number density of positrons to that of electrons on the phase shift are studied. It is found that these parameters can significantly influence the phase shifts of the solitons. Moreover, the compressive solitary wave can propagate in this system.     

电磁波在非磁化等离子体中衰减效应的实验研究

针对等离子体隐身技术在航空航天领域的良好应用前景, 开展垂直入射到具有金属衬底的非磁化等离子体中电磁波衰减特性的理论与实验研究. 利用WKB方法对电磁波衰减随等离子体参数的变化规律进行了理论分析. 利用射频电感耦合放电方式产生稳定的大面积等离子体层, 搭建了等离子体反射率弓形测试系统, 进行了电磁波在非磁化等离子体中衰减效应的实验研究. 利用微波相位法和光谱诊断法, 得到不同放电功率下的等离子体电子密度, 其范围为8.17×10⁹–7.61× 10¹⁰ cm^-3. 本实验获得的等离子体可以使2.7 GHz 和10.1 GHz电磁波分别得到一定的衰减, 且电磁波衰减的理论与实验结果符合较好. 结果表明, 提高等离子体电子密度和覆盖均匀性有利于增强等离子体对电磁波的衰减效果.     

Higher-order solution for dust acoustic solitary waves in an unmagnetized dusty plasma

The effect of higher-order nonlinearity on dust acoustic solitary waves is studied taking into account the dust-charge variation. The model of charge fluctuation, taken here, is of the formI _e+I _i=0,I _e andI _i being the electronic and ionic currents. The dust charge is determined self consistently from the current-balance equation. It is found that the higher-order correction modifies the amplitude and width of the dust acoustic solitary waves. The effect of dust-charge streaming is also discussed.     

Negative plasma potential in unmagnetized DC electropositive plasma with conducting walls

Negative plasma potentials were obtained in DC hot filament unmagnetized electropositive argon plasma for sufficiently low neutral pressure. Double layers provide ion and electron confinement near the walls. The potential profiles from the center of the plasma to the potential minima are quite similar in shape to those observed when the plasma has positive plasma potentials. The primary electrons emitted from the filaments are important for charge conservation and for modification of the Bohm criteria but are not important for current balance.     

�˶��ǴŻ����������е�Ų��������ЧӦ

根据狭义相对性原理,应用Lorentz变换法则,从相对运动媒质静止参考系中的有关结论,获取了实验室参考系中所需结果。通过证明平面波相位是Lorentz不变量,指出实验室参考系中平面波解的存在性。由Lorentz变换导出了实验室参考系中平面波色散关系表示式,据此给出运动媒质的波动方程。由Lorentz变换导出运动媒质中平面波Maxwell方程。基于这些结果,应用Lorentz变换获得了平面波从自由空间垂直入射到各向同性运动等离子体半空间时反射波与透射波的有关特性。     

Experimental observation of dust circulation in unmagnetized cogenerated dusty plasma

The vortex motion of a dust cloud was experimentally observed in unmagnetized cogenerated dusty plasma in different experimental parameters. Particle image velocimetry analysis demonstrated that several vortex zones exist in the dust cloud at relatively low pressures (0.06 mbar (or 6 Pa)–0.08 mbar (or 8 Pa)) and low discharge voltages (peak‐to‐peak voltage 540–560 V), whereas in relatively high pressure (0.4 mbar (or 40 Pa)–0.7 mbar (or 70 Pa)) and high discharge voltage (peak‐to‐peak voltage 690–740 V), dust vortices formed in dense dust cloud with background plasma fluctuation.     

Dispersion characteristics of two-dimensional unmagnetized dielectric plasma photonic crystal

This paper studies dispersion characteristics of the transverse magnetic (TM) mode for two-dimensional unmagnetized dielectric plasma photonic crystal by a modified plane wave method. First, the cutoff behaviour is made clear by using the Maxwell--Garnett effective medium theory, and the influences of dielectric filling factor and dielectric constant on effective plasma frequency are analysed. Moreover, the occurence of large gaps in dielectric plasma photonic crystal is demonstrated by comparing the skin depth with the lattice constant, and the influence of plasma frequency on the first three gaps is also studied. Finally, by using the particle-in-cell simulation method, a transmission curve in the \Gamma -X direction is obtained in dielectric plasma photonic crystal, which is in accordance with the dispersion curves calculated by the modified plane wave method, and the large gap between the transmission points of 27~GHz and 47~GHz is explained by comparing the electric field patterns in particle-in-cell simulation.     

Oblique collisional effects of dust acoustic waves in unmagnetized dusty plasma

Effects of oblique collisions of the dust acoustic(DA)waves in dusty plasma are studied by considering unmagnetized fully ionized plasma.The plasma consists of inertial warm negatively charged massive dusts,positively charged dusts,superthermal kappa distributed electrons,and isothermal ions.The extended Poincaré–Lighthill–Kuo(e PLK)method is employed for the drivation of two-sided Korteweg–de Vries(KdV)equations(KdVEs).The Kd V soliton solutions are derived by using the hyperbolic secant method.The effects of superthermality index of electrons,temperature ratio of isothermal ion to electron,and the density ratio of isothermal ions to negatively charged massive dusts on nonlinear coefficients are investigated.The effects of oblique collision on amplitude,phase shift,and potential profile of right traveling solitons of DA waves are also studied.The study reveals that the new nonlinear wave structures are produced in the colliding region due to head-on collision of the two counter propagating DA waves.The nonlinearity is found to decrease with the increasing density ratio of ion to negative dust in the critical region.The phase shifts decrease(increase)with increasing the temperature ratio of ion to electron(κe).The hump(compressive,κeκec)and dipshaped(rarefactive,κeκec)solitons are produced depending on the angle(θ)of oblique collision between the two waves.     

非磁化等离子体填充的相对论返波管的粒子模拟

 对非磁化等离子体填充的相对论返波管进行了粒子模拟分析，结果表明在一定的等离子密度范围内，观察到电子注的良好传输，得到了高功率电磁波输出。等离子体密度变化过程中，输出存在有峰值功率点。通过粒子模拟清晰地观察到注、等离子体及波相互作用的物理过程，并且模拟结果解释了部分实验现象。     

Relativistic and nonrelativistic modulational instability of a laser radiation in an unmagnetized laser-produced plasma: Kinetic theory

Summary This paper presents a rigorous theoretical investigation of the relativistic and nonrelativistic modulational instability of a high-power laser radiation propagating in a collisionless and unmagnetized laser-produced plasma. The kinetic equationviz. the relativistic Vlasov equation has been employed to find the nonlinear response of electrons for this four-wave parametric process in the plasma. The actual motivation behind this theoretical investigation is to find the relativistic effect on this four-wave paremetric processviz. the modulational instability. Here, it can be noted that the modulational instability of the laser radiation under our situation has not a large but considerable relativistic effect and for the same set of plasma parameters the growth rate of the instability in ultrarelativistic consideration is approximately three times higher than that in the nonrelativistic consideration. The authors of this paper have agreed to not rective the proofs for correction.     

Structure formation in turbulence as an instability of effective quantum plasma

Structure formation in turbulence can be understood as an instability of “plasma” formed by fluctuations serving as effective particles. These “particles” are quantumlike in the sense that their wavelengths are non-negligible compared to the sizes of background coherent structures. The corresponding “kinetic equation” describes the Wigner matrix of the turbulent field, and the coherent structures serve as collective fields. This formalism is usually applied to manifestly quantumlike or scalar waves. Here, we show how to systematically extend it to more complex systems using compressible Navier–Stokes turbulence as an example. In this case, the fluctuation Hamiltonian is a five-dimensional matrix operator and diverse modulational modes are present. As an illustration, we calculate these modes for a sinusoidal shear flow and find two modulational instabilities. One of them is specific to supersonic flows, and the other one is a Kelvin–Helmholtz-type instability that is a generalization of the known zonostrophic instability. Our calculations are readily extendable to other types of turbulence, for example, magnetohydrodynamic turbulence in plasma.     

非磁化等离子体光子晶体缺陷态的研究

采用时域有限差分法中的分段线性电流密度卷积算法,研究具有单一缺陷层的一维非磁化等离子体光子晶体的缺陷模特性.从频域角度分析得到微分高斯脉冲的透射率,并讨论该光子晶体的缺陷层介电常数、厚度、位置、光子晶体的周期常数和等离子体参数对其缺陷模的影响.结果表明,改变以上参数可获得不同的缺陷模. 关键词： 时域有限差分法 非磁化等离子体光子晶体 缺陷模     

时变非磁化等离子体光子晶体缺陷态研究

采用非磁化等离子体的分段线形电流密度卷积(Current density convolution,JEC)时域有限差分(Finite-dif-ferent time-domain,FDTD)算法研究了具有单一缺陷层的一维时变非磁化等离子体光子晶体的缺陷模特性。以高斯脉冲为激励源,通过由算法公式得到的电磁波透射系数讨论了等离子体上升时间对其缺陷模的影响。结果表明,改变等离子体的上升时间和密度可以获得不同的缺陷模。     

辛几何算法在计算非磁化等离子体中波传播轨迹时的应用

为了在数值计算中保持哈密顿系统的辛几何结构不变,利用辛几何算法得到了在线性哈密顿系统中射线追踪方程的一般辛差分格式。通过具体算例,利用辛几何算法计算了波在非磁化等离子体中的传播轨迹,并且与传统Runge-Kutta-Fehlberg算法所得结果进行了比较。利用辛几何算法所得传播轨迹与解析解一致,其色散函数值的误差随时间线性增长,能在长时间内保持色散函数值在一个很小的误差范围内。利用传统的Runge-Kutta-Fehlberg算法所得传播轨迹与解析解不一致,其误差随时间做大幅振荡增加。计算结果表明辛几何算法在保持传播轨迹和色散函数值方面具有独特的优势。     

�ǴŻ�����������������ĵ�Ų�ɢ�����Է���

The characteristic of electromagnetic scattering by plasma cylinder is researched in this paper. Scattered fields of the parallel-polarized wave and vertical-polarized wave by plasma cylinder are calculated and analyzed. The calculated results show that the higher the electron density, is the greater the scattering intensity in the outside of the cylinder and the higher the plasma frequency of collision, is the smaller the scattering intensity in the outside of the column. In addition, the electromagnetic wave polarization and frequency of the incident wave also have a significant impact on the scattering intensity of electromagnetic waves, the vertically polarized wave is more likely to be scattered, and the lower frequency of the incident wave is also easier to scattering. These have certain reference value for designing and studying of the plasma antenna.