摘要:

The free energy associated with the anisotropy in the velocity space of a microwave‐heated hot electron distribution can drive the mirror mode unstable. The real frequency of this instability is of the same order as the diamagnetic drift frequency of the hot electrons.

ISSN:0031-9171    

DOI:10.1063/1.864008

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A mechanism is proposed to interpret the experimental results which show a reduction in the short wavelength output power when gyroresonance is reached. The presence of an axial magnetic field in a free electron laser around gyroresonance introduces a strong long wavelength Raman backscattering instability which itself gives rise to electron trapping and causes the desired short wavelength radiation to saturate earlier than unmagnetized free electron lasers.

ISSN:0031-9171    

DOI:10.1063/1.863980

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

New experiments and new finite element computations with surface tension of jet shapes at Reynolds numbers up to 100 were made. Good agreement between experiment and computations was obtained.

ISSN:0031-9171    

DOI:10.1063/1.863987

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Laser‐Doppler velocimetry has been used to measure the critical Reynolds number for the onset of time‐dependent motion and its characteristic features in Taylor‐Couette flow. For moderate values of the aspect ratio &Ggr; the critical Reynolds number is observed to be extremely sensitive to length effects, and the form of oscillation arising at the stability limit is found to change in neighboring ranges of &Ggr;. At even higher Reynolds number the oscillation type may change and hysteresis phenomena are observed. These new features are beyond the reach of any available theory and they highlight the need for caution when transition to turbulence observations are interpreted.

ISSN:0031-9171    

DOI:10.1063/1.863998

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Solitary waves in density stratified fluids of shallow depth are described, to first order in wave amplitude, by the Korteweg–de Vries equation; the solution for a single solitary wave has the familiar ‘‘sech2’’ profile and a phase speed which varies linearly with the wave amplitude. This theory is here extended to second order in wave amplitude. The second‐order correction to the wave profile and the phase speed and the first‐order correction to the wavelength are all determined. Four special cases are discussed in detail. In certain special circumstances the first‐order theory may fail due to the vanishing of the nonlinear coefficient in the Korteweg–de Vries equation. When this occurs a different theory is required which leads to an equation with both quadratic and cubic nonlinearities.

ISSN:0031-9171    

DOI:10.1063/1.863994

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

It is shown that when the wavelength of the internal gravity wave in the propagation direction is close to some integer multiple of the characteristic half‐width of the background Bru¨nt‐Va¨isa¨la¨ frequency, a sequence of period doubling bifurcations occurs. This process transfers energy from high horizontal, low vertical wavenumber modes to low horizontal, high vertical wavenumber modes.

ISSN:0031-9171    

DOI:10.1063/1.863973

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A Hamiltonian is constructed for the description of internal motions of a stratified fluid in terms of Eulerian coordinates. The Hamiltonian describes both internal waves and motions with vertical vorticity and the couplings between them. The construction is made by a motivated recipe, based on a motivated Legendre transformation. The role of the Lin constraints in the recipe is clarified. The number of canonical variables (4) exceeds the number of physical degrees of freedom (3), giving rise to a ‘‘gauge’’ invariance. The group of gauge transformations is indentified.

ISSN:0031-9171    

DOI:10.1063/1.863981

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

The shock thickness is estimated for a stationary shock in an ideal gas by equating the internal entropy production to the entropy increase found from the Rankine–Hugoniot equation. For elementary assumed profiles, the thickness is expressed by a simple formula. For realistic dependence of viscosity on temperature, results are in qualitative agreement with experiment.

ISSN:0031-9171    

DOI:10.1063/1.863982

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

A matched asymptotic expansion technique is used to derive the equations describing the hydrodynamic behavior of a diatomic gas. As an example, for which the complete description is explicitly known, sound dispersion due to vibrational relaxation is shown to correspond to an inner asymptotic description.

ISSN:0031-9171    

DOI:10.1063/1.863983

出版商:AIP    

年代:1983

数据来源: AIP

摘要:

Quasilinear theory for the usual weak warm beam instability is reconsidered. It is found that mode‐coupling terms yield non‐negligible corrections to the quasilinear diffusion coefficient and mode growth rates. These mode coupling effects give rise to non‐Gaussian statistics that invalidate both the usual Fokker–Planck equations and the resonance broadening theories.

ISSN:0031-9171    

DOI:10.1063/1.863984

出版商:AIP    

年代:1983

数据来源: AIP