摘要:

The strongest fluid motions produced by the general dynamical nonequilibrium of close-packed twisted flux tubes are associated with the neutral point reconnection of the magnetic field, expelling jets of fluid along the neutral sheet away from each reconnection point at velocities comparable to the Alfven speed. Most of the energy of the reconnecting field goes into the kinetric energy of the jets.

ISSN:0309-1929    

DOI:10.1080/03091928308209060

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Calculations are presented for the evolution of a magnetic field which is subject to the effect of three-dimensional motions in a convecting layer of highly conducting fluid with hexagonal symmetry. The back reaction of the field on the motions via the Lorentz force is neglected. We consider cases where the imposed field is either vertical or horizontal. In the former case, flux accumulates at cell centres, with subsidiary concentrations at the vertices of the pattern. In the latter, topological asymmetries between up- and down-moving fluid regions generate positive flux at the base of the layer and negative flux at the top, though the system is actually an amplifier rather than a self-excited dynamo. Spiral field lines form in the interiors of the cells, and the phenomenon of “flux expulsion” found in two-dimensional solutions is somewhat altered when the imposed field is horizontal. Applications for stellar magnetic fields include a possible mechanism for burying flux at the base of a convection zone.

ISSN:0309-1929    

DOI:10.1080/03091928308209061

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

The convective critical effects of water near 4°C in a finite vertical cylinder are examined by means of local temperature measurements at the midplane of the cell. The properties of water in such a state induce a different behaviour from that observed in “Boussinesq” fluids. In particular, at the threshold the convective temperature jumps discontinuously from zero to a finite value. Convection occurs via an inverted bifurcation, the associated hysteresis loop being observed for the first time.

ISSN:0309-1929    

DOI:10.1080/03091928308209062

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

摘要:

Solutions of the steady, inviscid, non-linear equations for the conservation of potential vorticity are presented for linearly sheared geostrophic flow over a right circular cylinder. The indeterminancy introduced by the presence of closed streamline regions is removed by requiring that the steady flow retains above topography a given fraction of that fluid initially present there, assuming the flow to have been started from rest. Those solutions which retain the largest fraction in uniform and negatively sheared streams satisfy the Ingersoll (1969) criterion (that, in the limit of vanishingly small viscosity, closed streamline regions are stagnant) and so are unaffected by Ekman pumping. These flows are set up on the advection time scale. In positively sheared flows the maximum retention solutions do not satisfy the Ingersoll criterion and thus would be slowly spun down on the far longer viscous spin-up time.

ISSN:0309-1929    

DOI:10.1080/03091928308209063

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor

ISSN:0309-1929    

DOI:10.1080/03091928308209064

出版商:Taylor & Francis Group    

年代:1983

数据来源: Taylor