摘要:

The threshold intensity for excitation of the stimulated Raman backscatter instability has been measured at 9.58 &mgr;m in a well‐diagnosed plasma free of Brillouin scattering. The initial level of density fluctuations was independently measured by ruby laser scattering. The observed threshold of 1×1011 W/cm2is somewhat below the calculated ‘‘absolute’’ threshold for underdense plasmas, and the apparent noise level is higher than that measured directly.

ISSN:0031-9171    

DOI:10.1063/1.865770

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A new method is demonstrated for extracting radiation from a virtual cathode oscillator in transverse electric (TE) waveguide modes. The dominant radiation mechanism occurs in the region of the virtual cathode, and is not due to reflexing of electrons. Microwave radiation occurs simultaneously or just after beam pinching in the diode. Electrostatic signals show simultaneous occurrence of the virtual cathode and microwave radiation. At the same time, the electron population divides into a beam population and a reflexing electron population. Inhibition of pinching by an axial guide field suppresses microwave radiation.

ISSN:0031-9171    

DOI:10.1063/1.865771

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Steady thermocapillary convection is examined in a differentially heated rectangular cavity of small aspect ratioA. It is shown that when the capillary number isC=O(A3), the interface undergoes anO(1) deformation from its flat position and the flow inside the cavity becomes nonparallel everywhere. The velocity and temperature profiles and the shape of the deformed interface are derived using the method of matched asymptotic expansions.

ISSN:0031-9171    

DOI:10.1063/1.865772

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A scalar model of turbulent incompressible convection is presented in which transfer of energy between modes at different scales or between horizontal and vertical vorticity modes is represented by quadratic nonlinear interactions. The growth rate of the modes is parametrized in order to take into account the buoyancy force and the mean temperature gradient. At a small Prandtl number (which is of astrophysical interest) it is found that the Nusselt number scales as (R&sgr;)1/3. The form of the spectrum at large wavenumbers is that of three‐dimensional turbulence (Kolmogoroff spectrum). At small wavenumbers the spectrum is determined by the growth rate of the unstable modes.

ISSN:0031-9171    

DOI:10.1063/1.866013

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The motion of a sphere in a rarefied gas is considered with the use of the BGK model and a boundary condition of diffuse reflection. The role of temperature variation in the Knudsen layer is studied; results show that velocity and pressure in the layer and the drag on the sphere are not sensitive to this variation.

ISSN:0031-9171    

DOI:10.1063/1.865773

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

This Brief Communication introduces a special relativistic extension of ideal magnetohydrodynamics having anisotropic pressure, and provides its Hamiltonian formulation in a fixed inertial frame. The nonrelativistic limit of this theory recovers the ‘‘double adiabatic’’ hydromagnetic equations of Chew, Goldberger, and Low [Proc. R. Soc. London Ser. A236, 112 (1956)]. For isotropic pressure distribution the equations and Hamiltonian structure reduce to the usual theory of relativistic magnetohydrodynamics. The Poisson bracket for the system is not symplectic. Rather, it is dual to a Lie algebra of semidirect‐product type.

ISSN:0031-9171    

DOI:10.1063/1.865774

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

A high &bgr; plasma is injected into an axisymmetric magnetic mirror. The &bgr; is varied principally by varying the midplane value of the magnetic field. The plasma fills most of the space inside of a conducting vacuum chamber. It is observed for a radially averaged ⟨&bgr;⟩>35% that the plasma is initially stable, while for ⟨&bgr;⟩<25% the plasma is initially unstable. The values of &bgr; required for stability are lower than those predicted from magnetohydrodynamic (MHD) theory.

ISSN:0031-9171    

DOI:10.1063/1.865775

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

Certain objections regarding the article of Horiuchi and Sato [Phys. Fluids29, 1161 (1986)] are presented. One class of objections is technical and the second concerns matters of attribution.

ISSN:0031-9171    

DOI:10.1063/1.865776

出版商:AIP    

年代:1986

数据来源: AIP

摘要:

The essence of nonlinear driven reconnection, which does not seem to be well understood by the reader as of yet, is described in order to avoid unnecessary misunderstanding of the magnetohydrodynamic self‐organization mechanism proposed by the present authors[Phys. Fluids29, 1161 (1986)].

ISSN:0031-9171    

DOI:10.1063/1.865777

出版商:AIP    

年代:1986

数据来源: AIP

ISSN:0031-9171    

DOI:10.1063/1.866026

出版商:AIP    

年代:1986

数据来源: AIP