摘要:

The zonal momentum fluxes in a turbulent rotating system are formally expressed by sums of flux modes whose latitude dependence is sin21Θ. The resulting profiles in latitude of the angular velocity Ω and the horizontal Reynolds stress are derived for the surface of the fluid. Very thin convection zones and those with strong density stratification behave in a very similar way: their surface profiles show nearly the same modal structure as the momentum fluxes. Besides the turbulence parameters, only the thickness of the convective layer is required to determine the amplitudes of the resulting profiles; no damping due to the strong density stratification appears. Even the lowest order models withl=1 and 2 can account for both the observed solar rotation law and the horizontal Reynolds stress (the Ward profile). The required vertical flux modes represent an inward transport of angular momentum and the required horizontal flux modes an equatorward transport. They must each be increased if the natural outward decrease of the non-fundamental modes (i.e.l>0) of the zonal momentum fluxes is included.

ISSN:0309-1929    

DOI:10.1080/03091928208209003

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Models of a differentially rotating compressible convection zone are calculated, considering the inertial forces in the poloidal components of the equations of motion. Two driving mechanisms have been considered: latitude dependent heat transport and anisotropic viscosity. In the former case a meridional circulation is induced initially which in turn generates differential rotation, whereas in the latter case differential rotation is directly driven by the anisotropic viscosity, and the meridional circulation is a secondary effect.

ISSN:0309-1929    

DOI:10.1080/03091928208209004

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The generation of a mean zonal flow by centrifugally driven thermal convection in a rotating annulus heated from the outside and cooled from within is investigated theoretically as well as experimentally. It is shown that the direction of the mean flow depends on the curvature of the conical surfaces bounding the fluid in the axial direction. Convex conical boundaries give rise to a prograde mean flow in the outer part and a retrograde mean flow in the inner part of the fluid annulus. The directions are reversed for concave conical boundaries. Although the parameter regime for which the theoretical results have been derived could not be realized in the experiment, semi-quantitative agreement between theoretical predictions and observations has been found.

ISSN:0309-1929    

DOI:10.1080/03091928208209005

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

A steady source-sink driven flow in a rotating annulus is considered. The source and sink are located at the inner and outer cylinder, and consist of two immiscible fluids of different density and viscosity. For an axisymmetric source-sink distribution it is shown that the interior (geostrophic) flow in each layer is the sum of a potential vortex and a solid body rotation. Moreover, the flow in each layer is anticyclonic when the source is located at the inner cylinder, and vice versa. Some aspects of the interfacial stability are also reported.

ISSN:0309-1929    

DOI:10.1080/03091928208209006

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

Inertial waves are excited in a fluid contained in a slightly tilted rotating cylindrical cavity while the fluid is spinning up from rest. The surface of the fluid is free. Since the perturbation frequency is equal to the rotation speed resonance occurs at a critical height to radius aspect ratio of the fluid. Detailed study of a particular inertial wave shows that in solid body rotation this “eigenratio” agrees with predictions from linear inviscid theory to within 0.5%. Measured time dependence of the eigenratio during spin-up from rest is a function of the tilt amplitude and agrees favorably with predictions from a numerical study. Mean flow associated with the inertial wave becomes unstable during spin-up and in the steady state. A boundary for the unstable region is found experimentally.

ISSN:0309-1929    

DOI:10.1080/03091928208209007

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

If a conducting fluid shell is undergoing spin-axisymmetric differential rotation and overlies the dynamo generating region of a planet then it is capable of greatly reducing the non-spin-axisymmetric components of the generated field, provided the appropriate magnetic Reynolds number is large. The model, closely related to the electromagnetic skin effect, is quantified and applied to Saturn. The observed small dipole tilt (∼ 1°) of Saturn's magnetic field can be explained because of the presence of a stably stratified conducting layer overlying the dynamo region. This layer is a predicted consequence of the thermal evolution, arises because of the limited solubility of helium in metallic hydrogen (Stevenson, 1980), and appears to be required by the Voyager infrared observations indicating depletion of helium from Saturn's atmosphere. The much larger dipole tilt angles of Jupiter and the Earth indicate the absence of any such stable, differentially rotating layer with a large magnetic Reynolds number.

ISSN:0309-1929    

DOI:10.1080/03091928208209008

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

The stability of steady equilibrium amplitudes of magnetic fields generated by convection flows is investigated. Two cases are considered in detail, for which steady solutions are available from the previous work of Busse (1973) and Busse (1977). In the first case instability occurs primarily because of magnetic flux expulsion at high magnetic Reynolds numbers. In the second case the change in the velocity field caused by the Lorentz force enhances dynamo action. This subcritical finite amplitude dynamo is potentially unstable. In typical cases the nonlinear dynamo oscillations that replace the steady equilibrium solutions are investigated by numerical integration.

ISSN:0309-1929    

DOI:10.1080/03091928208209009

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor

摘要:

This paper is concerned with the derivation of the dispersion relation of a static fully ionized hydrogen plasma, at a temperature much smaller than 1010°K, interacting with radiation through electron scattering. The Fokker-Planck form of the transfer equation is first considered and the derivation of the dispersion relation is reduced to the resolution of av-differential eigenvalue problem, which could be realized by numerical integration. In the second part, the dispersion relation is explicitly derived in the frame of an algebraic approximation of the transfer equation. This shows that the branches of this relation, which are obtained in the optically thick and in the optically thin limits, are continuously connected to each other in a somehow remarkable way.

ISSN:0309-1929    

DOI:10.1080/03091928208209010

出版商:Taylor & Francis Group    

年代:1982

数据来源: Taylor