摘要:

An equilibrium quasi-linear regime consisting of forced topographic waves and a steady flow component correlated with bottom relief is analysed using the low-order spectral model of quasi-geostrophic ocean dynamics. Two functions - a correlationCbetween potential vorticity and the topography and a topographic stress forceD- are employed to study the qualitative structure of the steady flow component. Both a negative and positiveCappear in the model. This function is denned mostly by topographically induced energy fluxes among barotropic and/or among baroclinic modes when the horizontal scale of the bottom undulations is smaller than the internal Rossbi radius. Over the large-scale topographic features, the interface displacements, controlled by the energy transfer between barotropic and baroclinic components, dominate inC. The β-effect tries to develop negative homogeneousC.

ISSN:0309-1929    

DOI:10.1080/03091929508228953

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

Using the induction equation, we investigate the generation of electromagnetic fields by the motional electromagnetic induction due to ocean currents. In this paper, solutions are presented for a linear induction equation for the magnetic flux density vector which contains prescribed time-independent ocean current and conductivity fields. Once the magnetic flux density is known, the electric field and electric current density are easily obtained by differentiation.

ISSN:0309-1929    

DOI:10.1080/03091929508228954

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The problem of the onset of convection in a rotating spherical shell with an imposed magnetic field is studied. This problem is relevant to understanding the dynamics of the Earth's outer core. The finite conductivity of the inner core is taken into account and no-slip boundary conditions are assumed at the inner-core and core-mantle boundaries. The problem is investigated numerically, using values of the Ekman number down to 10−6.

ISSN:0309-1929    

DOI:10.1080/03091929508228955

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We consider mean-field dynamo models in uniformly rotating spheres and spherical shells, with anisotropic alpha and magnetic diffusivity tensors which are functions of the inverse Rossby number, Ω*. When we include an a-quenching nonlinearity we show that, for all values of Ω* considered, nonaxisymmetric magnetic fields are stable to axisymmetric perturbations. However the stability of nonaxisymmetric magnetic fields is weakened for large values of Ω*, which would make the generation of axisymmetric magnetic fields more probable. When a small amount of differential rotation is introduced, only axisymmetric dipole-like solutions are stable. We draw attention to the possibility that the nonaxisymmetric magnetic fields of Uranus and Neptune could be the result of anisotropic alpha and magnetic diffusi vity tensors. The more nearly axisymmetric magnetic fields of Jupiter and Saturn could result from their more rapid rotation, or possibly because of internal differential rotation.

ISSN:0309-1929    

DOI:10.1080/03091929508228956

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

We consider a rapidly rotating compressible fluid spherical shell, and study linear perturbations of a polytropic equilibrium state. Instead of considering the fully compressible problem, we make the anelastic approximation. We start from Boussinesq solutions and study the effect of introducing compressibility for different choices of the Prandtl number,Pr, comparing our results with those for a similar model of Glatzmaier and Gilman (1981). ForPr= 1 and 10, the results are similar. As compressibility is increased, convection becomes localised near to the inner boundary, an effect which is magnified by increasing the rotation rate. When we considerPr= 0.1 we find different results. As compressibility is introduced, the critical Rayleigh number,Rcdecreases sharply and becomes negative. This behaviour was not found by Glatzmaier and Gilman.

ISSN:0309-1929    

DOI:10.1080/03091929508228957

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

The many complex regions of positive and negative flux that thread the surface of the Sun are mainly grouped around the edges of supergranule cells. These cells have large concentrations of magnetic flux on their boundaries and very little flux inside, with the magnetic fragments that appear in the centre of the cells swept to the boundaries by convective motions. Thus, a small bipolar pair of magnetic fragments (such as an ephemeral region) emerges inside a cell and moves towards the cell boundary as it grows. On reaching the boundary the fragments encounter unipolar regions of network flux with which they may merge or cancel. When cancellation takes place there is often an associated X-ray bright point in the overlying corona.

ISSN:0309-1929    

DOI:10.1080/03091929508228958

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor

摘要:

BÉnard cells and taylor vorticesby EL. Koschmieder, Cambridge University Press, 1993, X + 339 pp., £35.00, hardback (ISBN 0-521-40204-2)

ISSN:0309-1929    

DOI:10.1080/03091929508228959

出版商:Taylor & Francis Group    

年代:1995

数据来源: Taylor