摘要:

It is shown that a wake of electron plasma oscillations can be created by the nonlinear ponderomotive force of an intense neutrino flux. The electrons trapped in the plasma wakefield will be accelerated to high energies. Such processes may be important in supernovas and pulsars. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.872704

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

It is shown that there are two low-frequency modes associated with vertical oscillations in the Coulomb crystal of dust grains arranged in two horizontal chains in a sheath region of a low-temperature gas discharge plasma. The dispersion relations and characteristic frequencies of the modes are found. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.872705

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

It is demonstrated that Alfve´n waves may be the convenient trigger for the formation of transport barriers in tokamaks. Kinetic or slow Alfve´n waves, which appear in the tokamak plasma as a result of the rf wave’s conversion, have small radial localizations. It is proposed that these waves can be used to create strongly sheared plasma flows at any point of the plasma minor radius, to suppress the plasma turbulence and to obtain the locally reversed magnetic shear configuration. Estimations concerning the absorbed power of Alfve´n waves, which are necessary to suppress the plasma turbulence in some tokamaks, are about the level of absorbed power to be used in early fulfilled experiments. This method can assist the achievement of self-organization processes in tokamaks. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.872706

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The formalism necessary to study the collective properties of a plasma system with inhomogeneous flows is nonlocal and generally in the form of an integrodifferential equation. Usually the eigenvalue condition is reduced to a second-order differential equation for simplicity. While the gross physical behavior of the system can be obtained from the second-order differential equation level of description, higher-order corrections are necessary for greater accuracy. The limit in which the scale-size of the velocity inhomogeneity is large compared to the ion gyroradius is considered and a transverse flow profile sharply localized in space (“top-hat” profile) is assumed. In this limit, a simple analytical method for the solution of the general eigenvalue condition to all orders is developed. A comparison of the properties of the solutions obtained from the second-order differential equation level of description with those obtained from higher orders is presented. Both the resonant (dissipative) and the nonresonant (reactive) effects of velocity shear are considered. It is found that while the overall features are well represented by the second-order level of description, the higher-order corrections moderate the destabilizing effects due to velocity shear, which can be quite significant in some cases. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.872671

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Rayleigh–Taylor instability in a finely structured emulsion-like medium consisting of the two components of different compressibility is considered. Although the term “emulsion” is used to describe the structure of the medium, under typical conditions of pulsed fusion devices the medium is actually a plasma. The two components are chosen in such a way that their densities in the unperturbed state are approximately equal. Specific emphasis has been made on the analysis of perturbations with the scale &slgr; considerably exceeding the size of the grainsa.Average equations describing such perturbations are derived. The difference in compressibility of the two components leads to the formation of temperature variations at the scalea,and increases the rate of the thermal dissipation by a factor(&slgr;/a)2.The strongest stabilizing effect of the thermal dissipation takes place when the heat conduction time is comparable with the instability growth rate. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.872672

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The relaxation process of a space uniform plasma composed of cold electrons and one species of hot ions is studied numerically using one- and two-dimensional Landau–Fokker–Planck codes. Relaxation of a monoenergetic ion beam is considered in possibly extreme temperature regimes. Special attention is paid to the deviation of the relaxation process from the classical picture, which is characterized by the close initial temperaturesTe≫(me/mi)1/3Ti.The present results give quite a clear idea of the relaxation picture for any initial temperatures also in extreme temperature regimes. A difference scheme, preserving the number of particles and the energy, gives the possibility of solving the problem numerically without error accumulation, except for machine errors. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.872673

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A new type of mode conversion between two linear waves in a nonuniform medium is investigated. Single-crossing conversion occurs when a ray of one wave crossestransverselythe dispersion manifold of another wave.Double-crossingmode conversion theory describes when the ray punctures the dispersion manifold twice due to raycurvature. To study this new process, a one dimensionally nonuniform background medium is considered, which gives rise to four scenarios. These scenarios are distinguished on the basis of whether the two waves have equal or opposite energy signs, and whether they are copropagating or counterpropagating. Usingmodular-eikonal theory (suitable for multiple crossings), each scenario is first studied analytically by constructing anS-matrix relation between theoutgoingandincomingasymptotic wave amplitudes. The analytical results are then compared with numerical results and excellent agreement is found. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.872674

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

A whistler wave propagating through a magnetized dusty plasma undergoes stimulated Brillioun scattering off ion-cyclotron and ion-acoustic modes. The dust has little effect on nonlinear coupling. However, it reduces the growth rate by introducing linear damping on the low-frequency modes. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.872675

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

Employing quasipotential analysis, the Sagdeev potential equation has been derived in a multicomponent plasma consisting of free and trapped electrons and contaminated by the dust charged grains forming therein by the attachment of electrons to finite-size dust particles. Because of the free and trapped electrons in the dusty plasma, the plasma-acoustic wave exhibits the different features of various solitary waves. The Sagdeev potential equation, at a small-amplitude approximation, leads to the evaluation, by a proposed new formalism of a simple wave solution technique, of the new scenario of solitary wave propagation in a dusty plasma. It has been shown that the ordering of the nonisothermality in the dusty plasma also plays a unique role. In the case of a plasma with first-order nonisothermality, the Sagdeev potential equation derives the compressive solitary wave propagation, while for plasma with higher-order nonisothermality the method might fail to solve the Sagdeev potential equation and, thus, an alternate method is used to reveal the coexistence of compressive and rarefactive solitary waves. In addition, for certain plasma parameters, the solitary waves disappear and a double layer is expected. Again, with the better approximation in the Sagdeev potential, more features of solitary waves, known as spiky and explosive, along with the double layers, are also highlighted. The observations made of the solitary waves could be of further interest in the understanding of laboratory and space plasmas.©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.872699

出版商:AIP    

年代:1998

数据来源: AIP

摘要:

The kinematic-dynamo problem with steady Beltrami flows at high magnetic Reynolds number is studied by a local analysis along unstable Lagrangian trajectories in the chaotic region and from some global considerations. The chaos properties of the flow, especially the local characteristic directions, are related to the time evolution and to the spatial distribution of the field solutions derived from the local analysis. Global considerations show that there are some integral constraints that a growing eigenmode of the magnetic field should satisfy, and an antidynamo result is given for the understanding of why some chaotic flows are not capable of fast dynamo action. ©1998 American Institute of Physics.

ISSN:1070-664X    

DOI:10.1063/1.872676

出版商:AIP    

年代:1998

数据来源: AIP