The ion drift measurements made by a number of DMSP satellites during some intervals in 1991, 1997, and 1998 are utilized for estimation of the ionospheric electric fields over the near-pole region; these estimates are then compared with the Polar Cap (PC) magnetic activity index obtained from ground geomagnetic observations at Qaanaaq (former Thule, Greenland) and Vostok (Antarctica). The analysis shows that the polar cap electric field is primarily controlled by variations in the near-Earth's interplanetary electric field. The relationship between the polar cap ionospheric electric field and the PC-index can be approximated by a quadratic polynomial. The polar cap ionospheric electric field tends to saturate at the asymptote of approx. 45-50 mV/m when the PC index reaches large positive values (PC > 10); the residual electric field (for near-zero interplanetary electric field applied to the Earth's magnetosphere) is approx. 12 mV/m. It is concluded that the PC-index can serve as a proxy of the ionospheric electric fields in the near-pole region.