A numerical study is made of buoyant convection of air in an enclosure under constant gravity and time-periodic magnetizing force. Buoyant convection occurs when the two vertical sidewalls are maintained at different temperatures and the horizontal walls are thermally insulated. To this basic layout, electric coils are located at the left and right sides of the cavity for case 1. For case 2, the electric coils are located below and above the cavity. The currents in the coils are activated in an alternating fashion. Comprehensive numerical solutions are found for the time-dependent Navier-Stokes equations, which include the magnetizing force term. The computed results reveal the existence of resonance, which is characterized by maximal amplification of the fluctuations of heat transfer in the interior. This resonance phenomenon is apparent when the basic mode of internal gravity oscillation is excited. The augmentation and/or suppression of convective activities by the action of magnetizing force is the primary factor to induce resonance. The configuration of case I is seen to be more effective than that of case 2 in heat transfer enhancement. (c) 2006 Elsevier Ltd. All rights reserved.