Effect of electrically conducting walls on rotating magnetoconvection

Abstract

In an experiment carried out by Aurnou and Olson [J. Fluid Mech. 430, 283 (2001)] thermal convection in a liquid gallium layer in the presence of a uniform vertical magnetic field was investigated. The critical Rayleigh number at the onset of magnetoconvection was determined as a function of the Chandrasekhar number Q (the ratio of the Lorentz force to the viscous force) and the Taylor number Ta (the squared ratio of the Coriolis force to the viscous force). In the experimental apparatus, the upper and lower boundaries of the liquid gallium layer were electrically conducting copper plate walls. This paper presents a study of the effect of electrically conducting walls on rotating magnetoconvection. It is shown that the electrical properties of the walls have significant effects on the characteristics of rotating magnetoconvection when both the Chandrasekhar number Q and the Taylor number Ta are sufficiently large. It is demonstrated that, as a consequence of the electrically conducting walls, oscillatory magnetoconvection can become steady and the critical Rayleigh number can change by as much as 60%. The problem of convectively driven Alfvén waves in a rotating fluid layer in the presence of a uniform vertical magnetic field is discussed in an appendix.