Observation of interplanetary magnetic field and of ionospheric plasma convection in the vicinity of the dayside polar cleft

Dayside ionospheric convection at high latitudes has been examined during a series of experiments using the Sondrestrom radar together with ancillary observations of the interplanetary magnetic field (IMF) by the IMP-8 spacecraft. The radar experiments obtained a latitude coverage of 67.6° Λ to 81.30° Λ and a temporal resolution of between 14 to 25 minutes. A total of 17 rotations through the dayside cleft region during April, June and July, 1983 have been examined. The observations show two convection cells with sunward flow at lower latitudes and antisunward flow at higher latitudes. The flow commonly rotates through a 180° angle resulting in the predominant appearance of east-west flows. Rapid temporal variations in the convection velocities are frequently observed. Many of the high latitude variations in convection velocity appear to be directly related to variations in the IMF B_y component, with eastward (westward) velocity associated with negative (positive) B_y. This is strong evidence for a direct electrical coupling between the solar wind and dayside high latitude ionosphere.