Substorm-associated fluctuations in magnetopause position were observed on October 8, 1974, as the Hawkeye satellite approached the magnetopause outbound. On October 4, while Hawkeye was well within the magnetosheath, substorm activity was accompanied by a significant increase in the magnetic field fluctuation level at the satellite and on the ground in the polar cap and nightside sectors. Several mechanisms for producing the pulsations observed in the magnetosheath are considered. Some fluctuations of magnetopause position are produced internally by substorms, while others are produced externally by interaction of the interplanetary medium with the magnetosphere. Reconnection on the dayside together with invasion of the inertia current into the magnetosheath may account for the wave activity observed in the magnetosheath during the October 4 substorm.