Pulsations in Pc 1 period range recorded at Ottawa for three years during the IMS are analyzed to study some of their occurrence characteristics. The diurnal occurrence pattern depends on the seasons and on the prevailing magnetic activity conditions. In both cases the morning peak shifts to earlier hours and the evening peak shifts to later hours with increasing conduction (electron density) in the ionosphere. The largest number of events were recorded in the winter months and about as many in the equinoctial months. A large majority of the events are inferred to occur, at Ottawa, during the recovery phase of magnetic storms. The enhancements of Pc 1's noted at different levels of magnetic activity seem to be controlled by the location of the plasmapause and also by the propagation conditions in the ionosphere. The existence of a relationship between the occurrence of Pc 1 pulsations and the sector polarity of the interplanetary magnetic field remains to be established.