摘要:

The paper explores some of the many facets of the problem of the generation of magnetic fields in convective zones of declining vigor and/or thickness. The ultimate goal of such work is the explanation of the magnetic fields observed inA-stars. The present inquiry is restricted to kinematical dynamos, to show some of the many possibilities, depending on the assumed conditions of decline of the convection. The examples serve to illustrate in what quantitative detail it will be necessary to describe the convection in order to extract any firm conclusions concerning specific stars.

ISSN:0309-1929    

DOI:10.1080/03091928108208835

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The Sun's atmosphere is highly structured by magnetic fields, and this modifies the nature of the usual Alfvén waves which propagate in an everywhere uniform medium. Two simple magnetic field structures are considered: theinterfaceprofile (for which a discontinuity separates two media with different, but uniform, unidirectional magnetic fields), and themonotonicprofile (for which the magnetic field is unidirectional and continuous but not everywhere constant).

ISSN:0309-1929    

DOI:10.1080/03091928108208836

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The ray method is used to study the free oscillations of an incompressible, inviscid, perfectly conducting fluid of constant density contained in a rotating spherical shell, in the presence of a constant toroidal magnetic field. For sufficiently large values of the rate of rotation and sufficiently small values of the azimuthal wave number, the oscillations are confined to seven bands of latitude for a range of frequencies, which are more bands than have been found in the non-hydromagnetic case. The phase velocity is shown to have no preference for either eastward or westward drift.

ISSN:0309-1929    

DOI:10.1080/03091928108208837

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

A variational approximation to the dispersion relation for trapped waves on a flat shelf of depthh1, bounded internally by a vertical coast and externally by a semi-infinite ocean of depthh2>h1, is obtained through an integral-equation formulation that accounts for all of the non-propagated modes that are excited at the discontinuity in depth (the conventional formulation of the edge-wave problem allows only for the propagated mode on the shelf and the dominant, non-propagated mode in the deep water). Coriolis effects are neglected. The exact result in the limit ω2h2/g↓0 (ω = angular frequency) is obtained by conformal mapping and compared with the variational approximation, which proves to be quite accurate over the entire range 1>h2/h1>x. The effects of the higher-order, non-propagated modes are found to be small for the long waves observed over the Southern California shelf by Snodgrass, Munk and Miller (1962).

ISSN:0309-1929    

DOI:10.1080/03091928108208838

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

An exact integral is given for the unforced,f-plane, nondissipative and dissipative quasigeostrophic equations. The integral becomes infinite everywhere in a finite time. It is an extreme example of Bergeron's (1928) hypothesis for frontogenesis, but it does not satisfy side boundary conditions. The only side boundary conditions leading to well-posed problems are those of periodicity in each horizontal direction. Subject to periodicity conditions the forced,f-plane, dissipative quasigeostrophic equations have smooth solutions for all finite time provided that Reynolds' analogy holds and the surface potential temperatures vanish identically. If the latter are allowed to evolve in accordance with the laws of thermodynamics then the equations may only have smooth solutions for a certain finite time. If Reynolds' analogy does not hold then the equations may not have smooth solutions at all.

ISSN:0309-1929    

DOI:10.1080/03091928108208839

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The geostrophic equilibrium of a highly dispersive medium, i.e. a medium in which the propagation speed of disturbances is highly dependent on the local value of mass, is considered. Initially there exists a discontinuity or leading edge at which the mass jumps from zero to a finite value. The study is motivated by consideration of ice dynamics in the Marginal Ice Zone (MIZ). It is shown in general that a geostrophic equilibrium exists in which the leading edge is displaced a finite distance from its initial position. The theory is applied to the Marginal Ice Zone (MIZ) of the Arctic ice pack. Depicted spatial scales are in reasonable agreement with existing observational data. The theory predicts the existence of an along ice edge jet in the MIZ. The jet transports ice along the edge with the ice to the right (Northern Hemisphere).

ISSN:0309-1929    

DOI:10.1080/03091928108208840

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The radial temperature differences at which the transitions from one wave number to the next occur have been measured with either increasing or decreasing positive radial temperature gradients, at five different rotation rates, with the fluid being always in thermal equilibrium and being in contact with an upper rigid lid. Hysteresis has been observed in all wave number transitions, and also in the transition to upper symmetry. There are, nevertheless, regions in the stability diagram where the wave number is unique. There is an excluded region where the wave number four cannot be obtained through quasi-steady procedure. There is a reversal of the sense of the hysteresis of the transitions. At low ΔT, a wave number transition with increasing radial temperature difference occurs at a higher ΔT, than the same transition with decreasing temperature difference. On the other hand, at large values of ΔT, a wave number transition with increasing radial temperature difference occurs at a lower ΔT, than the same transition with decreasing temperature difference. Wave number transitions with increasing ΔT, occur spontaneously out of amplitude oscillations. Wave number transitions with decreasing ΔT, occur via slow wave splitting in association with phase modulations of the waves. The uniqueness of the wave number in the unique areas of the stability diagram has been confirmed by sudden start experiments.

ISSN:0309-1929    

DOI:10.1080/03091928108208841

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

The velocities of the wave patterns relative to the rotating annulus have been measured with either increasing or decreasing positive radial temperature gradients and different rotation rates, with the fluid in thermal equilibrium and in contact with a rigid lid. The pattern velocities are dependent on initial conditions except in the unique areas of the stability diagram, where the velocities observed with either increasing or decreasing ΔT, overlap. The pattern velocities change discontinuously with each wave number transition, with a particularly large discontinuity at the transition from two to one wave. The frequency of the amplitude oscillations of the waves has been measured also. It has been found that the period of the oscillation of the three wave pattern is inversely proportional to the period of the pattern velocity, which means that in this case the ratio of the frequency of amplitude oscillation and the frequency of the pattern revolution is incommensurate.

ISSN:0309-1929    

DOI:10.1080/03091928108208842

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

By K. Lambeck (Cambridge Monograph on Mechanics and Applied Mathematics). Cambridge University Press, Cambridge, England, 1980. xi +449 pp. (Hard cover £35.00) (ISBN 0 521 22769 0).

ISSN:0309-1929    

DOI:10.1080/03091928108208843

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor

摘要:

By John P. Cox. Princeton University Press, 1980. xiv+380 pp. (Hard cover £40; paperback £13.50). (ISBN Hard cover 0691 08252 9, Paperback 0 691 08253 7.)

ISSN:0309-1929    

DOI:10.1080/03091928108208844

出版商:Taylor & Francis Group    

年代:1981

数据来源: Taylor