282-291Convection in magnetic fluids is considered in the presence of vertical magnetic field and periodically modulated gravitational field. Depending upon the different physical parameters, modulation may have destabilizing effect on the unmodulated stable system. Also, the unstable system may get stabilized with modulation. Instability may occur either as subharmonic instability or harmonic instability. Using Floquet theory, the regions of parametric instability have been obtained