A destabilizing vertical temperature gradient and a rotating magnetic field have been
applied to a cylindrical column of liquid gallium. The convective flows which arise
as a function of these parameters are identified. For small magnetic field strengths,
a regime of stationary flow is observed. This regime is bounded by critical values
of the Rayleigh and magnetic Taylor numbers. As the rotating magnetic field is
increased, the critical Rayleigh number can increase by more than a factor of 10.
The rotating magnetic field itself induces an instability at a critical value of the
magnetic Taylor number independent of the Rayleigh number. The nature of the
bifurcations (whether subcritical or supercritical) and the convective flows occurring
at the critical Rayleigh numbers are dependent upon the magnetic Taylor number.
For small magnetic Taylor numbers, the experimental observations are consistent
with the occurrence of a single asymmetric meridional roll which is driven around
the cylinder by the rotating magnetic field.