摘要:

This is a sequel to our earlier study on ion‐acoustic waves studied through the augmentation to a modified Korteweg–deVries (K–dV) equation. We have derived a K–dV equation in a plasma, taking account of weakly relativistic effects, and the result shows that the solitary wave does exhibit the relativistic effect in the presence of ion streaming.

ISSN:0031-9171    

DOI:10.1063/1.865050

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The quasistationary slow plasma response to the Langmuir and electromagnetic waves is investigated. Conditions for the wave localization are obtained analytically, and new kinds of soliton profiles are found.

ISSN:0031-9171    

DOI:10.1063/1.865407

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

It is shown that an electrostatic wave near the upper‐hybrid resonance frequency can parametrically excite extraordinary (X‐) mode radiation accompanied by a great variety of low‐frequency oscillations. The latter may include the lower‐hybrid, the electron‐acoustic, the ion‐cyclotron, and the shear Alfve´n waves. Nonlinear dispersion relations and the growth rates are obtained for each case. Comparison of our investigation to an earlier work and its possible application to space plasmas are pointed out.

ISSN:0031-9171    

DOI:10.1063/1.865051

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

New results concerning the mathematical properties of the Fokker–Planck equation describing the electron distribution function are presented. The validity of the approximations obtained by using a finite number of Legendre polynomials to describe the electron distribution function is discussed. It is shown that, due to the Landau form of the electron‐ion collision operator, it is sufficient to use two or three Legendre polynomials in problems of interest. The theory is applied to the classical albedo problem as a test, and is also applied to determine the distribution and the heat flux in a heat front typical of laser plasma experiments. It is shown that the heat flux can be expressed as a sort of convolution of the Spitzer–Ha¨rm heat flux by a delocalization function. The convolution formula leads in a physically relevant way to the saturation and the delocalization of the heat flux.

ISSN:0031-9171    

DOI:10.1063/1.865052

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In the literature, the emission of radiation at 2&ohgr;e, where &ohgr;edenotes the electron plasma frequency, is usually explained as having been produced by the nonlinear interaction of two Langmuir waves via a backscattering process. Since the emission is frequently observed in solar radio bursts, the mechanism has attracted considerable theoretical interest. In the present paper a model is proposed based on a synchrotron‐maser instability excited by a hollow beam of moderately relativistic electrons in a plasma, in which the plasma frequency is much higher than the gyrofrequency. An important conclusion is that, as a result of this instability, unpolarized electromagnetic waves with frequencies near 2&ohgr;emay be amplified.

ISSN:0031-9171    

DOI:10.1063/1.865053

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The electric field pattern is studied in the capacitor model of resonance absorption. Hydrodynamic and kinetic theory are used. The electric field is calculated forL≳10&lgr;D, whereLis the density gradient length and &lgr;Dthe Debye length. The effect of collisional damping is studied. One obtains three different regimes. In the intermediate regime, the electric field amplitude is determined by the thermal convection, while the energy absorption is mainly caused by collisional damping.

ISSN:0031-9171    

DOI:10.1063/1.865054

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A general approximate criterion is developed (via WKB analysis) for the absolute instability of two parametrically pumped decay waves with one‐dimensional inhomogeneity. The absolute instability threshold pump power proves to be higher than that required for amplitude amplificationRby a factor &pgr;k’l2/27R, whenk’is the phase mismatchd&Sgr;ki/dxat the location of maximum instability andl−2is the effective curvature of the necessarily second‐order expansion about that point. Previous results are included as special cases.

ISSN:0031-9171    

DOI:10.1063/1.865055

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The characteristics of the partial differential equations describing three‐dimensional toroidal magnetohydrodynamic equilibria with nested flux surfaces in inverse flux coordinates are derived and examined. The equilibrium equations are then variationally reduced to a truncated set of ordinary differential equations by decomposing the flux surface geometry into a spectral representation. The magnetic field lines on the flux surfaces are given in terms of a variable stream function to allow optimum choice of the angle coordinates over the flux surfaces and to simplify the treatment in the vicinity of a rational magnetic surface. Analytic properties of the spectral representation and moment equations are considered. Comparative calculations are performed numerically. The results agree well with those calculated using a standard three‐dimensional equilibrium code, but the variational spectral method is substantially faster computationally. The Mercier stability criterion is given.

ISSN:0031-9171    

DOI:10.1063/1.865056

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

In a closed‐field‐line device such as a bumpy torus, the combinedE×Band ∇Bdrifts lead to charge separation that is balanced by the ion polarization drift. In this work, we determine self‐consistent potential and density profiles and the condition for electric island formation.

ISSN:0031-9171    

DOI:10.1063/1.865057

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Nonadiabatic changes of the magnetic moment &mgr; in the ELMO Bumpy Torus‐Scale (EBT‐S) have been studied both analytically and numerically. Simple forms of &Dgr; &mgr; and gyrophase change were obtained, permitting the changes in these quantities to be studied using an iteration mapping. The mapping results show stochastic behavior for particles having high energy and low initial &mgr;. Otherwise, superadiabatic motion appears. The stochastic diffusion coefficient for the variation of &mgr; was measured numerically by mapping and was also calculated from quasilinear theory. The results are shown to agree well in the stochastic region. For high‐energy particles, the diffusion in &mgr; caused by nonadiabaticity can be comparable to collisional diffusion when stochastic motion occurs for EBT‐S.

ISSN:0031-9171    

DOI:10.1063/1.865058

出版商:AIP    

年代:1985

数据来源: AIP