External regulation of convection in a weak electrically conducting non-Newtonian liquid with g-jitter

The effect of time-periodic temperature/gravity modulation at the onset of magneto-convection in weak electrically conducting second order liquids is investigated by making a linear stability analysis. The Venezian [J. Fluid Mech. 35 (1969) 243] approach is adopted in arriving at the critical Rayleigh and wave numbers for small amplitude temperature/gravity modulation. The temperature modulation is shown to give rise to subcritical motion and gravity modulation leads to delayed convection. Subcriticality or super-criticality depends on the sign of a correction Rayleigh number being negative or positive. An asymptotic analysis is also presented for small/large frequencies. A similar role is shown to be played by the Prandtl number. Comparison is made between the effects of temperature, gravity and combined (temperature+gravity) modulations.