It has been observed that quasi-periodic oscillations in the solar wind and interplanetary magnetic field (IMF) can result in the generation of auroral electrojet bursts and gravity waves with a similar period. In this paper, we present radar and magnetometer observations of quasi-periodic ionospheric disturbances during stable, northward IMF. Magnetic deviations of ~ 10 nT with a 40-min periodicity were registered with ground magnetometers between magnetic latitudes 75¿ and 80¿ over an extended region along the longitudinal direction in the morning sector. A sequence of gravity waves were observed by HF radars at lower latitudes and appeared to be closely related to the high-latitude 40-min current disturbances. There were no obvious source perturbations in the upstream solar wind for the ionospheric disturbances. We suggest that field line resonances could be excited in a closed magnetosphere during prolonged northward IMF and result in the generation of the ionospheric current disturbances and gravity waves. ¿ 2000 American Geophysical Union