A numerical model of Pi 2 disturbances in the magnetosphere is developed. The model of the magnetosphere is the same as one previously used for the study of Pc 5 pulsations. It is semicylindrical with field lines being semicircular arcs and longitude measured parallel to the axis. The model magnetosphere is excited by a source on the boundary which is limited both in time and in longitude. The disturbance is then a superposition of modes corresponding to all the azimuthal wave numbers excited by the source. The computations show that a global oscillation is excited and that there can be a significant signal on the dayside at low latitudes. The role of the plasmasphere in producing a low-latitude response is important. Because of the simplifications of the model the most important aspect of the calculations is the qualitative understanding that they supply. Nevertheless, quite good quantitative agreement with observation is obtained. The calculations support earlier suggestions about the response of the magnetosphere to the initiation of the substorm current wedge.¿ 1997 American Geophysical Union