摘要:

Two‐dimensional tokamak edge density turbulence data are examined for possible coherent or organized structure. The spatial patterns of density fluctuationsn˜ appear to consist of localized ‘‘blobs’’ of relatively high or low density which can move irregularly both radially and poloidally through the edge region. However, a statistical analysis of the lifetime, area, direction, speed, and amplitude of these blobs does not as yet suggest any organized structure associated with the blobs beyond that which can be described by time‐averaged correlation functions.

ISSN:0031-9171    

DOI:10.1063/1.865069

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Parametric decay processes have been studied using rf probes and CO2laser scattering during the lower‐hybrid wave heating and current drive experiments in the Alcator C tokamak. The most important process is believed to be the nonresonant decay into ion‐cyclotron quasimodes and/or that into electron‐Landau quasimodes. At lower densities &ohgr;0/&ohgr;lh(0)>2 [where &ohgr;0is the frequency of the injected pump wave and &ohgr;lh(0) is the lower‐hybrid frequency evaluated at the plasma center], where efficient current drive and electron heating are obtained, parametric decay is absent or very weak. At higher densities [&ohgr;0/&ohgr;lh(0) ≲2] strong parametric decay is observed which correlates well with ion tail formation near the plasma edge. Above these densities the electron tail is no longer formed and no significant heating or current drive have been obtained. Parametric decay may be responsible, at least partially, for loss of wave power near the plasma periphery.

ISSN:0031-9171    

DOI:10.1063/1.865070

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The effects of inertia (involving a drag which is quadratic in the velocity) on convection in a fluid‐saturated porous medium are considered. It is shown that the effect of quadratic drag is physically significant for natural convection, at realistic values of the Rayleigh number, in a thin layer of a medium whose overall Prandtl number is small. The qualitative effect of quadratic drag on the global stability of the conduction regime, and on bifurcation into the convection regime, is reported. Convection in an inclined slab of material is also discussed.

ISSN:0031-9171    

DOI:10.1063/1.865071

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Nonlinear, slowly‐varying, finite‐depth standing waves over a flat bottom are shown to exhibit sideband instabilities at third order when the depth parameterhis larger than 1.022.

ISSN:0031-9171    

DOI:10.1063/1.865018

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

An analysis predicts an exponential downstream development of turbulent kinetic energy in the asymptotic development range of transversely homogeneous, uniformly sheared, turbulent flows. The analysis is found to be in good agreement with available experimental results and numerical simulations.

ISSN:0031-9171    

DOI:10.1063/1.865019

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A simple, direct, alternative derivation of the magnetohydrodynamic force law from an action principle is presented.

ISSN:0031-9171    

DOI:10.1063/1.865091

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

The equation for them=1 ballooning mode is derived; the dominant finite Larmor radius terms force the mode to be rigid. A dispersion relation with the wall near the plasma is obtained for arbitrary &bgr;, and it is also shown that with the wall at infinity only the vacuum curvature contributes to all orders in &bgr;.

ISSN:0031-9171    

DOI:10.1063/1.865092

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

A general representation of finite‐volume‐preserving maps induced by solenoidal vector fields in periodic cylinders is derived. An important special case is the area preserving Hamiltonian maps which include the standard mapping. Applications to computational problems in plasma physics are briefly indicated.

ISSN:0031-9171    

DOI:10.1063/1.865093

出版商:AIP    

年代:1985

数据来源: AIP

摘要:

Drift vortices are described by the Hasegawa–Mima equation in the case of density gradient drift waves. From computer results, it is known that the modon solutions of the Hasegawa–Mima equation are quite stable. Here the linear stability of ground state modon solutions is proved analytically by an indirect technique.

ISSN:0031-9171    

DOI:10.1063/1.865094

出版商:AIP    

年代:1985

数据来源: AIP