Drift Waves In Plasma Research Articles

Electrostatic drift waves in nonuniform quantum magnetized plasmas

Electrostatic drift waves (EDWs) in nonuniform quantum magnetized plasmas are described by the quantum hydrodynamic model. Electrons are viewed as a low-temperature Fermi gas. Analytical expression of the dispersion relationship of the quantum EDW is presented. Quantum effects are shown to affect the dispersion of the EDW significantly. The effects on the dispersion relation due to the magnetic field and spatial inhomogeneity give rise to results similar to the classical case. Our results should be relevant to dense astrophysical objects, e.g., neutron stars, magnet-stars, and white dwarfs.

Collisional instability of the drift wave in multi-component plasmas

The collisional instability of the drift wave in a multi-component plasma is investigated. It is shown that when the electron and ion density gradients are different, e.g., due to the presence of a static third component or due to neutral drag effects, the drift mode becomes unstable. The instability is caused by the simultaneous action of the electron collisions with all other plasma species and the spatial difference of the density of the plasma components. This instability may be expected as a natural consequence of the stratification of a multi-component plasma placed in an external gravity field where it can operate for any amount of charge on heavy particles. Therefore it could develop in weakly ionized cold interstellar regions for example, when the heavy particles, i.e. charged grains, are a few tens of Å in size, and carry typically ± 1 , ± 2 charge. In the solar atmosphere, it may appear in the weakly ionized photospheric layers due to the convective motion of the neutral component.

Statistical mechanics of two-dimensional turbulence

The statistical mechanical description of two-dimensional inviscid fluid turbulence is reconsidered. Using this description, we make predictions about turbulent flow in a rapidly rotating laboratory annulus. Measurements on the continuously forced, weakly dissipative flow reveal coherent vortices in a mean zonal flow. Statistical mechanics has two crucial requirements for equilibrium: statistical independence of macro-cells (subsystems) and additivity of invariants of macro-cells. We investigate these requirements in the context of the annulus experiment. The energy invariant, an extensive quantity, should thus be additive, i.e. the interaction energy between a macro-cell and the rest of the system (reservoir) should be small, and this is verified experimentally. Similarly, we use additivity to select the appropriate Casimir invariants from the infinite set available in vortex dynamics, and we do this in such a way that the exchange of micro-cells within a macro-cell does not alter an invariant of a macro-cell. A novel feature of the present study is our choice of macro-cells, which are continuous phase-space curves based on mean values of the streamfunction. Quantities such as energy and enstrophy can be defined on each curve, and these lead to a local canonical distribution that is also defined on each curve. The distribution obtained describes the anisotropic and inhomogeneous properties of a flow. Our approach leads to the prediction that on a mean streamfunction curve there should be a linear relation between the ensemble-averaged potential vorticity and the time-averaged streamfunction, and our laboratory data are in good accord with this prediction. Further, the approach predicts that although the probability distribution function for potential vorticity in the entire system is non-Gaussian, the distribution function of micro-cells should be Gaussian on the macro-cells, i.e. for curves defined by mean values of the streamfunction. This prediction is also supported by the data. While the statistical mechanics approach used was motivated by and applied to experiments on turbulence in a rotating annulus, the approach is quite general and is applicable to a large class of Hamiltonian systems, including drift-wave plasma models, Vlasov–Poisson dynamics, and kinetic theories of stellar dynamics.

Solar wind interaction with the stationary dust can produce drift waves to form nonlinear structures

Solar wind electrons and ions penetrating with shear flow into the stationary dust can introduce electrostatic drift wave in plasmas of cometary and planetary environments. The drift wave becomes linearly unstable in the presence of shear flow. The background current also produces shear in the static magnetic field which does not allow the Shukla-VarmaPhys. Fluids B [5, 236 (1993)] mode to exist in such a system. The vortex structures can be formed in nonlinear regime. The relevance of this investigation to space plasmas is pointed out.

A Spectral Global Gyrokinetic Approach to Plasma Linear Microinstability Analysis

With the term microinstabilities, we indicate a class of plasma drift waves such as the ion temperature gradient (ITG) mode, the trapped electron mode (TEM), and the electromagnetic Alfvénic ion temperature gradient (AITG) mode. They are usually driven by spatial gradients in the plasma and they are held responsible for anomalous transport and enhanced heat flux in tokamaks. Their understanding is therefore crucial for the development of magnetically confined plasma fusion devices. Our approach is based on the gyrokinetic model (Hahm 1988) for particle dynamics. The gyrokinetic nonlinear Vlasov equation, in the presence of an electromagnetic perturbation (Brizard 1989, 1995), is derived using Lie perturbation theory (Cary and Littlejohn 1983) to average out the fast particle motion around the gyrocenter. We have linearized the gyrokinetic Vlasov equation and added the quasi‐neutrality equation and Ampère's law, providing closure to the system. A temporal spectral formulation is used, ensuring the absence of numerical instabilities due to high frequency modes. The equations are simplified with a large aspect ratio approximation for an axisymmetric toroidal configuration. The fields are expanded in a Fourier series in the three spatial directions (radial, poloidal, and toroidal) reducing the problem in a matrix form. The code EM‐GLOGYSTO (Brunner et al. 1998; Falchetto et al. 2003; Joint Varenna‐Lausanne International Workshop 2002) has been developed to look at its solutions. Recently, we have included in the model an electrostatic equilibrium potential in order to provide E×B sheared flow. The code has been optimized for running in a parallel environment using MPI routines, and it allows us to study frequencies, growth rates, and mode structures of electromagnetic microinstabilities. Results on an AITG mode are shown to illustrate these features.

Instability of Drift Waves in Two-Component Solid-State Plasma

Summary form only given. The instabilities of longitudinal waves in the infinite semiconductor electron-hole plasma have been considered. It was assumed that the thermal velocity of electrons slightly exceeds the thermal velocity of holes. The investigated structure has been placed in an external electric field which results in the relative motion of electrons and holes. The consideration has been realized by a hydrodynamical approximation. The electromagnetic processes at such a structure have been described by Maxwell's and material equations. It was shown that the effective interaction of various drift waves is possible in the area of negative phase velocities. A correlation between the drift velocities of electrons and holes and thermal velocities of carriers have been obtained. The numerical calculation shows that the resonance area of frequencies exists. The width of the area grows when the ratio of electron and hole Langmuir frequencies tends to unity. The instabilities have aperiodic character when the Langmuir frequencies and thermal velocities of carriers are equal. A nonresonance instability (resistive instability) of hole waves appear when the dissipation processes are taken into consideration. Such an instability is possible when the phase velocity is both positive and negative. In this case the electron drift waves are damped.

Zonal flow and field generation by finite β drift waves: Finite ion temperature effects

The generation of zonal flows and zonal fields by finite β drift waves in plasmas with finite ion temperature Ti is investigated. This work extends our earlier work with zero ion temperature. The growth rate of the zonal flow and field is enhanced by finite Ti effects. This leads to a reduction in the critical electron temperature derived earlier for triggering low to high transitions in tokamak plasmas.

Ion temperature gradient instability in a dusty plasma.

An analysis of the temperature-gradient-driven ( eta(i) ) instability of drift waves in dusty plasma is presented. Various limits that allow for the coupling of the drift wave with the dynamics of dust grains are discussed. In particular, the cases of tiny (magnetized) and relatively heavy (unmagnetized) grains are studied. It is shown that in both limits the behavior of the eta(i) mode is considerably affected by the dust dynamics. The growth rate turns out to be higher in the presence of dust, and the instability threshold is lower, resulting in a more unstable plasma.

Critical dynamic events at the crisis of transition to spatiotemporal chaos.

In the driven/damped drift-wave plasma system a collision of the weak chaotic attractor with a saddle point is demonstrated at the crisis that induces a transition from a spatially coherent state to spatiotemporal chaos (STC). The phenomenon of the collision is consistent with the previous observation of the "pattern resonance" that triggers the crisis. Subsequent to the collision, before the system is ejected to the STC attractor, there is evidence of another critical dynamic event involving state transition of a mode phase. The second event plays a crucial role in the destruction of the spatial coherence.

Particle diffusion in anisotropic turbulence

We have investigated the diffusion of test particles in anisotropic two-dimensional turbulence. To be specific we have considered electrostatic drift-wave turbulence in magnetized plasma, described by the so-called Hasegawa–Wakatani equations, which produce a two-dimensional turbulent flow-field with a self-consistent instability drive. However, our results are also relevant for particle dispersion in beta-plane turbulence, due to the similarity between drift waves in plasmas and Rossby waves on the beta-plane. In general, we observe that the particle dispersion is strongly anisotropic, with the diffusion in the zonal direction much larger than the diffusion in the direction parallel to the background density gradient––the radial direction (meridional direction for the beta-plane analogy). Trapping of particles in and subsequent displacement with vortical structures leads to an intermediate anomalous diffusion with superdiffusive behaviour in the zonal direction and subdiffusive behaviour in the radial direction. However, the time asymptotic behaviour always approaches a normal diffusive process. By including inertial effects in the particle velocity we observe a tendency for increased superdiffusive behaviour.

On the two-dimensional regularized long-wave equation in fluids and plasmas

To the two-dimensional regularized long-wave equation we perform computerized symbolic computation to obtain a new auto-Backlund transformation and picture out some new bell-shaped and anti-bell-shaped solitary waves, which could help in the investigations on the Rossby waves in rotating fluids and the drift waves in plasmas.

Taming Drift Wave Turbulence

Drift waves in magnetized plasmas often occur in a turbulent form and are often considered as being responsible for anomalous cross-field particle transport. It is thus very appealing to achieve active control of the drift wave dynamics. A control scheme acting both in space and in time is developed to synchronize drift wave turbulence. It consists of an arrangement of eight electrodes (octupole exciter) in flush-mounted geometry in the edge region of the magnetized plasma column. The electrodes of the octupole exciter are driven by sinusoidal signals. Between each two neighbouring electrodes, the phase shift of the exciter signal is kept fixed. It is demonstrated experimentally that the exciter signals have strong influence on the different drift wave states, i.e. the turbulent states can be synchronized to a single preselected drift wave mode. The efficiency of the spatiotemporal synchronization is sensitively dependent on both driver frequency and phase shift.

Taming Drift Wave Turbulence

Drift waves in magnetized plasmas often occur in a turbulent form and are often considered as being responsible for anomalous cross-field particle transport. It is thus very appealing to achieve active control of the drift wave dynamics. A control scheme acting both in space and in time is developed to synchronize drift wave turbulence. It consists of an arrangement of eight electrodes (octupole exciter) in flush-mounted geometry in the edge region of the magnetized plasma column. The electrodes of the octupole exciter are driven by sinusoidal signals. Between each two neighbouring electrodes, the phase shift of the exciter signal is kept fixed. It is demonstrated experimentally that the exciter signals have strong influence on the different drift wave states, i.e. the turbulent states can be synchronized to a single preselected drift wave mode. The efficiency of the spatiotemporal synchronization is sensitively dependent on both driver frequency and phase shift.

Stability enhancement by boundary control in the Kuramoto–Sivashinsky equation

where we refer to ? 0 as the “anti-di ussion” parameter. Note that a more general form ut + 1uxxxx + 2uxx + 3uux = 0 can always be reduced to (1.1) by appropriate rescaling of t; x and u. Eq. (1.1) was derived independently by Kuramoto et al. [20–22] as a model for phase turbulence in reaction–di usion systems and by Sivashinsky [33] as a model for plane ame propagation, describing the combined in uence of di usion and thermal conduction of the gas on stability of a plane ame front. So far, it has been well understood that the KS-equation can also serve as a mathematical model for cellular instabilities in a variety of situations: the ow of thin liquid lms on inclined planes [30] (in the limit of large surface tension), dendritic fronts in dilute binary alloys [31], and Alfven drift waves in plasmas [23] (as a nonlinear saturation mechanism of the dissipative trapped ion modes).

Excitation of zonal flow by drift waves in toroidal plasmas

An analytical dispersion relation is derived which shows that, in toroidal plasmas, zonal flows can be spontaneously excited via modulations in the radial envelope of a single-n coherent drift wave, with n the toroidal mode number. Predicted instability features are verified by three-dimensional global gyrokinetic simulations of the ion-temperature-gradient mode. Nonlinear equations for mode amplitudes demonstrate saturation of the linearly unstable pump wave and nonlinear oscillations of the drift-wave intensity and zonal flows, with a parameter-dependent period doubling route to chaos.

Bernstein–Greene–Kruskal chain of drift-tearing vortices

Collisionless magnetic reconnection in the driftwave plasma regime, ρs,i≫de, is studied using a drift-kinetic description of electrons and fluid ions. A fully nonlinear Bernstein–Greene–Kruskal (BGK) stationary solution is constructed which has the form of a quasi-three-dimensional chain of electron holes coupled to hydrodynamic vortices. This stationary structure is obtained by setting up a plateau in the electron distribution function, followed by the trapping and consecutive depletion of resonant particles, and by the removal of the singular current layers by their short-circuiting via electron gyrations.

Kinetic vortex chain solution in the drift-wave plasma regime

A fully nonlinear Bernstein-Greene-Kruskal stationary solution is found in the form of a quasi-three-dimensional chain of electron holes coupled to hydrodynamic vortices. This new coherent structure is enabled by the trapping and depletion of resonant particles, and the cyclotron dissipation of the singular current sheets. It is expected to play an important role in the collisionless magnetic field line reconnection in the drift-wave plasma regime, where it represents a plausible saturated state.

Drift waves in plasmas with sheared flows

In the standard approach to the problem of shear stabilization of drift waves the diamagnetic drift velocity v* is regarded as a constant, which is usually not satisfied at the edge of a tokamak plasma. In configurations of this type, with a steep density gradient and radially sheared transverse velocity field, the magnetic shear stabilization criteria are severely restricted, and the velocity profile curvature v0″(x) is found to play a crucial role. In the strongly nonlinear regime, unstable drift waves may saturate into stationary coherent vortex-type structures. The latter include a tripolar vortex.

Nonmodal energetics of resistive drift waves

The modal and nonmodal linear properties of the Hasegawa-Wakatani system are examined. This linear model for plasma drift waves is nonnormal in the sense of not having a complete set of orthogonal eigenvectors. A consequence of nonnormality is that finite-time nonmodal growth rates can be larger than modal growth rates. In this system, the nonmodal time-dependent behavior depends strongly on the adiabatic parameter and the time scale of interest. For small values of the adiabatic parameter and short time scales, the nonmodal growth rates, wave number, and phase shifts (between the density and potential fluctuations) are time dependent and differ from those obtained by normal mode analysis. On a given time scale, when the adiabatic parameter is less than a critical value, the drift waves are dominated by nonmodal effects while for values of the adiabatic parameter greater than the critical value, the behavior is that given by normal mode analysis. The critical adiabatic parameter decreases with time and modal behavior eventually dominates. The nonmodal linear properties of the Hasegawa-Wakatani system may help to explain features of the full system previously attributed to nonlinearity.

Dissipative drift waves in partially ionized plasmas containing high-Zimpurities or dust

The theory of drift waves in plasmas containing highly charged impurities (dust) is developed to include such specific features as attraction of dust grains as well as collisions between dust and neutral particles. Nonlinear equations taking into account variations of drift potential together with plasma electron, ion, and neutral densities, as well as dust charges, are obtained. The range of plasma parameters where the effects introduced by dust can trigger the dissipative drift-wave instability is found.