Transition from steady to oscillating convection rolls in Rayleigh-Bénard convection under the influence of a horizontal magnetic field

The effect of a horizontal magnetic field on the oscillatory instability of convection rolls in a finite liquid-metal layer is investigated. The flow measurements reveal that the first developing oscillations are of a two-dimensional nature. In particular, a mutual increase and decrease in the size of adjacent convection rolls is observed where the periodicity of the ``breathing'' convection rolls can be related to standing inertial waves. With gradual reduction of the magnetic-field strength, the oscillating convection rolls are increasingly affected by three-dimensional disturbances.