Since 1978, radar observations of F region electric fields within the region 55¿<&Lgr;<75¿ have been made from Millstone Hill (42.6¿N, 71.5¿W). Average convection patterns have been calculated from the ion drift data gathered in 109 of these experiments conducted between January 1978 and August 1981. Most of the experiments lasted between 24 and 48 hours, and over 3,700,000 values of the line-of-sight velocity were determined and included in the averages. The observed velocities were sorted into ''bins'' of 1/2-hour intervals of magnetic local time and 2¿ intervals of apex latitude. Each of these cells had been viewed by the radar over a wide range of aspect angles in the course of the 109 experiments, allowing the average vector velocity to be determined. The data were separated further into three levels of Kp, according to whether the interplanetary magnetic field (IMF) was ''toward'' or ''away'' from the sun, and by season. The average patterns are discussed and compared with earlier models based on satellite and incoherent scatter data. There is an expansion and intensification of the pattern with Kp for all seasons and IMF orientations. The polar cap entry and exit points of the plasma, the center of the cells, and the polar cap boundary all depend on the IMF. The Harang discontinuity, which can be seen clearly on individual days, is largely lost in the averages. |