Observations, made both in space and on the ground show that phase jumps occur between wave packets in dayside pulsation signals. During the course of a single wave packet, the signals from two stations may drift apart in phase. The action of the phase jump is to bring the signals back into phase. This suggests an impulsive source for such dayside pulsations, each wave packet being excited by a new impulse. We speculate about a nightside source connected with changes in magnetospheric convection.