Observations from the ANARE station at Macquarie Island show that the development of an auroral display is characterized by a slow northward drift, east to west longitudinal motion, and an associated positive bay in the horizontal component magnetogram in the evening hours. This is followed by a sudden change in structure of the aurora and appearance of a negative bay. The negative bay persists for some hours, accompanied by west to east longitudinal motion and slow southward drift of the aurora.