A numerical study is made of transient convective cool-down of air in a cylindrical container when both gravity and magnetizing force act. The magnetizing force is generated in an inhomogeneous magnetic field for an electrically nonconducting fluid with high magnetic susceptibility. Cooling of air is accomplished by abruptly lowering the temperature of the cylindrical sidewall under a strong vertical magnetic field. Comprehensive numerical computations are obtained for ranges of pertinent external parameters. The behavior of flow and temperature fields are delineated as the radius and axial position of the electrical coil are varied. When the magnetizing force is parallel to gravity, the flow is invigorated and cool-down process is facilitated. When the magnetizing force opposes the gravity, the overall cool-down process is least effective when the strength of magnetizing force is comparable to gravity. (c) 2005 Elsevier Ltd. All rights reserved.