Dust Sheared Flow Driven Instability of Dust Drift Waves in a Nonuniform Magnetoplasma

We investigate instability of dust drift waves in a nonuniform dusty magnetoplasma containing transverse sheared plasma flow that is produced by a nonuniform electric field. By using Boltzmann distributed electrons and ions, Poisson’s equation, as well as the dust continuity equation with perpendicular guiding center dust drift speed, we derive an eigenvalue equation, which strongly depends on the profiles of dust sheared flow and dust density gradient. The eigenvalue equation is analytically solved to obtain expressions for the growth rate and threshold of a convective instability arising from resonant interactions between the dust drift waves and sheared flows. The result may be relevant to the understanding of short wavelength (in comparison with the ion gyroradius) electrostatic fluctuations in magnetized plasmas of Saturn rings and in cometary tails. PACS numbers: 52.27.Lw; 52.35.Fp     

Effects of Vortex-Like Ion Distribution on Dust-Acoustic Solitary Waves in a Self-Gravitating Opposite Polarity Dusty Plasmas

A self-gravitating opposite polarity dust plasma (SGOPDP) medium (containing both positively and negatively charged dust, vortex-like distributed ions and Maxwellian electrons) has been considered in order to examine the effect of vortex-like (trapped) ion distribution on dust-acoustic (DA) solitary waves (SWs) propagating in SGOPDP medium. The reductive perturbation method, which is valid for small but finite amplitude SWs, is employed to derive a modified Korteweg-de Vries equation having stronger nonlinearity. The basic features of the DA SWs in SGOPDP medium are found to be significantly modified by the combined effect of self-gravitational field and vortex-like ion distribution. The results of this paper have many implications in space and laboratory dusty plasmas.

     

Three-Dimensional Dust-Acoustic Waves in a Collisional Dusty Plasma with Opposite Polarity Particles

The dispersion relation is derived for three-dimensional dust-acoustic waves in a current-driven dusty plasmas with both positively and negatively charged dust particles. The dependencies of the frequency and the growth rate on the wave number K, the intensity of magnetic field B, and the inclination angle θ have been numerically shown in this paper. The growth rate is negative for the laboratory dusty plasma, but it is positive for the cosmic dusty plasma.It is found that when the inclination angle θ = π/2, there is no instability. The effect of the electrostatic field E0 has also been studied in this paper.     

Three-Dimensional Dust-Acoustic Waves in a Collisional Dusty Plasma with Opposite Polarity Particles

The dispersion relation is derived for three-dimensional dust-acoustic waves in a current-driven dusty plasmas with both positively and negatively charged dust particles. The dependencies of the frequency and the growth rate on the wave number K, the intensity of magnetic field B, and the inclination angle θ have been numerically shown in this paper. The growth rate is negative for the laboratory dusty plasma, but it is positive for the cosmic dusty plasma. It is found that when the inclination angle θ = π/2, there is no instability. The effect of the electrostatic field Eo has also been studied in this paper.     

Solitons and Vortices in Plasmas

The various types of nonlinear wave solutions in plasmas are reviewed. First, the generation, pro- pagation, and stability of solitary waves are demonstrated for some simple examples. Then, relevant two-and three-dimensional models for Langniuir solitons are proposed and investigated. The collapse as an effective dissipation mechanism in plasmas is discussed in detail. Finally, simple models of two-dimensional vortex motion and their consequences are considered.     

Instability Driven by Anisotropy Ion Temperature Gradient in Toroidal Plasmas

Stimulated by ion cyclotron resonance frequency (ICRF) heating and neutral beam injection (NBI) heating which can generate anisotropy in temperature and temperature gradient of ions in tokamak experiments, Migliuolo first investigated effects of ion temperature anisotropy on ion temperature gradient (ITG) driven modes in a shearless slab configuration.     

Difusion in Two-dimensional Magnetized Dusty Plasmas

A molecular dynamical simulation method is used to investigate the difusion of the two-dimensional magnetized dusty plasmas.The efects of charge and mass of the particles,as well as the external magnetic field are discussed in detail.It is shown that,relative to the mass of particulate,the charge and magnetic field have a more considerable efect on the difusion process,particularly on the resulting structure of the system.The dependence of difusion coefcient on the temperature is shown to be linearly changed over a wide range of temperature.     

Stability of Rayleigh-Taylor Vortices in Dusty Plasma

The evolution of Rayleigh-Taylor mode in dusty plasma with vortex-flow is investigated. Based on fluid theory and Bayly＇s method, we derive the coupling equations describing the Rayleigh-Taylor mode in the core of vortex, and research the evolution characteristics of the perturbation amplitude with time numerically. It is shown that the eccentric of vortex and the content of dust have considerable effects on the amplitude evolutions.     

Short Wavelength Ion Temperature Gradient Driven Instability in Noncircular Flux Surface Plasmas with Finite Aspect Ratio

By employing the local equilibrium of shaped tokamak plasmas, a gyrokinetic model with integral eigenmode equations is developed to investigate effects of the finite aspect ratio and noncircular flux surface on short wavelength ion temperature gradient （SWITG） driven modes. It is found that when nonadiabatic electron and trapped particle effects are not considered, the SWITG mode can be stabilized by finite aspect ratio A, elongation and triangularity δ, and can be destabilized by the Shafranov shift gradient θRo/θr.     

Shock Waves due to Grain-Charge Variation in Dusty Plasmas

Nonlinear electrostatic wave structures in plasmas containing variable-charge dust grains, Boltz-mann electrons, and inertial ions are investigated. The charge variation is assumed to be caused by electron and ion currents at the grains. It is found that intense shock waves can exist. The dissipation in such shock waves originate from the process of dust charging.     

Current-Driven Kink-Like Instability in Collisional Plasmas

The stability of left-hand circularly polarized waves propagating along an external magnetic field with wavelengths much larger than the ion Larmor radius is studied for fully-ionized collisional plasmas carrying a field-aligned current. It is found that, in the presence of electron-ion collisions, this "kink-like" instability has two branches of unstable wavenumbers: a main branch and a resistive branch. The resistive branch owes its existence to electron-ion collisions, but its growth rate is much smaller than that of the main branch, which is typically some fraction of the ion cyclotron frequency. The effect of collisions on the main branch is to reduce its maximum growth rate while extending the range of unstable wavenumbers to larger values. However, these changes are significant only when the electron-ion collision frequency is comparable to the electron cyclotron frequency. The dispersion relation is solved numerically for plasma and magnetic field parameters appropriate to the UCLA arcjet plasma. The results show that, within the framework of an infinite and homogeneous theory, the kink-like instability should occur in this plasma device.     

Assembling Stabilization of the R-T Instability by the Effects of Finite Larmor Radius and Sheared Axial Flow

In the present paper, based on the incomepressible finite Larmor radius （FLR） magnetohydrodynamic （ MHD ） equations, we consider the stabilizing effect of the finite Larmor radius on the Rayleigh-Taylor （ RT ） instability in implosions of annular Z-pinch plasma. Here, the FLR is considered as a type of viscositytll, independent of any collisions （i.e., collisionless viscosity, or gyrouiscosity ）. Since we are introducing a sheared velocity,     

Drift and Diffusion in Periodically Driven Renewal Processes

We consider the drift and diffusion properties of periodically driven renewal processes. These processes are defined by a periodically time dependent waiting time distribution, which governs the interval between subsequent events. We show that the growth of the cumulants of the number of events is asymptotically periodic and develop a theory which relates these periodic growth coefficients to the waiting time distribution defining the periodic renewal process. The first two coefficients, which are the mean frequency and effective diffusion coefficient of the number of events are considered in greater detail. They may be used to quantify stochastic synchronization.     

Collisional Effects on Drift Wave Microturbulence in Tokamak Plasmas

Collisional effects on the microturbulence, excited by the electrostatic drift-wave instability, are investigated through first-principle large scale gyrokinetic particle simulations using the realistic discharge parameters of the DIII–D Tokamak. In the linear simulations, the growth rates of the drift waves are decreased by the collisions compared to the collisionless simulations in the lower and higher T_e plasmas. In the lower T_e plasma, the collisions can promote the transition of the drift wave regime from the TEM-dominant instability to the ITG-dominant instability. The zonal flows are excited by the microturbulence and work as a modulation mechanism for the microturbulence in the nonlinear simulations. Microturbulence can excite high frequency zonal flows in the collisionless plasmas, which is in agreement with the theoretical work. In the lower T_e plasma, the collisions decrease the microturbulence in the nonlinear saturated stage compared to the collisionless simulations, which are beneficial for the plasma confinement. In the higher T_e plasma, the final saturated microturbulence shows a slight change.     

Weibel Instability Growth Rate in Magnetized Plasmas with Quasi-Relativistic Distribution Function

The mechanism of the Weibel instability is investigated for dense magnetized plasmas. As we know, due to the electron velocity distribution, the Coulomb collision effect of electron-ion and the relativistic properties play an important role in such study. In this study an analytical expression for the growth rate and the condition of restricting the Weibel instability are derived for low-frequency limit. These calculations are done for the oscillation frequency dependence on the electron cyclotron frequency. It is shown that, the relativistic properties of the particle lead to increasing the growth rate of the instability. On the other hand the collision effects and background magnetic field try to decrease the growth rate by decreasing the temperature anisotropy and restricting the particles movement.     

Modulational Instability of Ion-Acoustic Waves in Collisional Plasmas

Nonlinear ion-acoustic waves, which in the absence of collisions are moderately stable in the long wave length limit, become modulationally unstable due to presence of collisions. These waves are unstable in the wave number range kmin < k < kmax.     

Instability of Electromagnetic Ion Cyclotron Harmonic Waves in Plasmas

The stability of electromagnetic ion cyclotron harmonic waves propagating normal to an external magnetic field is studied for plasmas whose ions possess loss cone type velocity distributions. It is found that, if the ions are stationary, no instability develops except in the extreme case when the ratio of parallel to perpendicular "temperatures" of the ions is of the order mi/me, where mi and me are the ion and electron masses respectively. However, for the case of two counterstreaming ion beams in a neutralizing background of electrons, instability at zero frequency and near the first several ion cyclotron harmonics can occur if the streaming velocity is of the order of the electron thermal speed.     

相对论电子的逆韧致吸收

在激光强度大于１０＾１８Ｗ／ｃｍ＾２的条件下，利用强激光场中完全相对论的电子运动轨迹，得到了稀薄等离子体中的韧致吸收系数计算公式，并与原有的逆韧致吸收系数的计算公式进行了比较。