Quasi‐periodic ionospheric disturbances with a 40‐min period during prolonged northward interplanetary magnetic field

Abstract

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.