On the dynamic interaction between magnetic fields and convection

A simple two-dimensional model of convection in an electrically conducting Boussinesq fluid with an externally imposed magnetic field has been investigated in a series of numerical experiments. Convection is driven by horizontal gradients in an imposed temperature field which is unaffected by the motion. The transition from a kinematic to a dynamic regime is studied: magnetic flux is concentrated into ropes and the maximum field strength depends on the ratio of the viscous and magnetic diffusivities. The magnetic energy density in the ropes is unrelated to, and may be much greater than, the kinetic energy density outside. These results are relevant to the interaction between small-scale magnetic fields and photospheric in the Sun. (author)