Pattern formation and dynamic transition for magnetohydrodynamic convection

Abstract

The main objective of this paper is to describe the dynamic transition of the incompressible MHD equations in a three dimensional (3D) rectangular domain from a perspective of pattern formation.We aim to classify the formations of roll, rectangle and hexagonal patterns at the first critical Rayleigh number.When the first eigenvalue of the linearized operator is real and simple, the critical eigenvector has either a roll structure or a rectangle structure.In both cases we find that the transition is continuous or jump depending on a non-dimensional number computed explicitly in terms of system parameters.When the critical eigenspace has dimension two corresponding to two real eigenvalues, we study the transitions of hexagonal pattern.In this case, we show that all three types of transitions--continuous, jump and mixed--can occur in eight different transition scenarios.Finally, we study the case where the first eigenvalue is complex, simple and corresponding eigenvector has a roll structure.In this case, we find that both continuous and jump transitions are possible.We give several bounds on the parameters which separate the parameter space into regions of different transition scenarios.