摘要:

A comparison is made between seven different numerical methods for calculating two-dimensional thermal convection in an infinite Prandtl number fluid. Among the seven methods are finite difference and finite element techniques that have been used to model thermal convection in the Earth's mantle. We evaluate the performance of each method using a suite of four benchmark problems, ranging from steady-state convection to intrinsically time-dependent convection with recurring thermal boundary layer instabilities. These results can be used to determine the accuracy of other computational methods, and to assist in the development of new ones.

ISSN:0309-1929    

DOI:10.1080/03091929008204111

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The relatively large resistivity in the solar photosphere and chromosphere softens the ideal tangential discontinuities of magnetostatic equilibrium into continuous transitions in field direction over scales of 0.1–10 km. This softening is communicated upward at the Alfvén speed into the active solar corona. The degree of softening is a vital part of the theory of magnetic heat input to the active X-ray corona, because the very low resistivity of the coronal gas provides effective dissipation only if the current sheets are reduced to a thickness of 10−2km.

ISSN:0309-1929    

DOI:10.1080/03091929008204112

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The stability of an internally heated horizontal water layer, with prescribed heat flux on the lower surface and constant upper surface temperature, is studied using a nonlinear energy analysis. The density of the fluid is assumed constant except in the buoyancy term. In this term we will employ an equation of state which assumes cubic dependence on temperature, as proposed by Merkeret al.(1979).

ISSN:0309-1929    

DOI:10.1080/03091929008204113

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

The linear stability of the sheet pinch is examined for a rapidly rotating fluid. The sheet pinch is a horizontal layer of uniform, incompressible, inviscid fluid of densityp, electrical conductivity [sgrave], magnetic permeability μ, confined between two perfectly conducting planesz=0,d, wherezis height. The prevailing magnetic field,B0(z), is horizontal; at each height it is unidirectional, but that direction turns continuously (in one sense only) aszincreases; the system is in magnetostatic equilibrium. The layer rotates about the vertical with an angular velocity, Ω, that is large: Ω>>VA/d, whereVA=B0/√(μp) is the Alfvén velocity and μ is the magnetic permeability. The dimensionless measure of [sgrave] is the Elsasser number A = [sgrave]B02/2Ωp.

ISSN:0309-1929    

DOI:10.1080/03091929008204114

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

A meridional circulation of sunspots has been measured through the digital analysis of the Meudon spectroheliograms from 1978 to 1983. Old and young sunspots follow a zonal meridional circulation, in several bands of latitude, in which two adjacent bands have opposite motions. This meridional circulation pattern is time-dependent. Using theHαfilaments as magnetic field tracers, a large-scale magnetic pattern has been found that was also obtained independently by direct measurement of the magnetic field (Hoeksema, 1988).

ISSN:0309-1929    

DOI:10.1080/03091929008204115

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor

摘要:

Finite amplitude convection is considered in a plane fluid layer rotating with angular velocity Ω about a horizontal axis in the y-direction. The fluid is electrically conducting, and a uniform horizontal magnetic field of strengthB0is applied horizontally, in the x-direction, perpendicular to the rotation axis. The gravitational acceleration, g is parallel toOz. The layer is infinite in y-extent but is bounded laterallyin the y-direction by vertical walls, which may be either stress-free or rigid, i.e. prevent fluid motion. The model is intended to simulate crudely conditions near the equator of the solar convection zone.

ISSN:0309-1929    

DOI:10.1080/03091929008204116

出版商:Taylor & Francis Group    

年代:1990

数据来源: Taylor