Abstract
The effect of a vertical ac electric field on the onset of convective instability in a dielectric micropolar fluid layer heated from below confined between two horizontal planes under the simultaneous action of the rotation of the system and the vertical temperature gradient is considered. Under the assumption that the neutral state is a stationary one, the power series method is adopted to obtain the eigenvalue equation which is then computed numerically. The effects of electric field and micropolar parameters on the critical Rayleigh heat number are discussed and illustrated graphically.