We present magnetic field data from the cusplatitude South Pole station that exhibit, under appropriate local time and interplanetary magnetic field conditions, the signature expected in the ionosphere from a flux transfer event (FTE) at the magnetopause. In particular, the model of multiple X-line reconnection at the magnetopause predicts field aligned currents in helical flux tubes, with transverse magnetic fields propagating as Alfv¿n waves toward the ionosphere. The distinctive magnetic signature at a polar cap magnetic station, particularly in the vertical component, can be used to infer the signs of the By and Bz components of the interplanetary magnetic field.