CONVECTIVE INSTABILITY IN A ROTATING FLUID LAYER UNDER MODULATION OF THE ROTATING RATE

The onset of convection in a rotating fluid layer heated from below is studied when the rotation speed is sinusoidally modulated. We study the instability that, in the absence of modulation, leads to stationary convection. We show that under modulation the conduction state can be stabilized or destabilized depending on the Taylor number, that the instability can be forward or backward for a range of Taylor numbers and modulation amplitudes, and that the critical Taylor number for the K̈ppers-Lortz instability is lowered. The calculations are carried out in the limit of large Prandtl number. © 1990 The American Physical Society.