Correlation studies are made on relationships between ionospheric currents calculated from EISCAT radar data (ion drift, electron density and temperature of ions and electrons), and ground magnetic variations observed at seven stations of the EISCAT magnetometer cross. The data used are 5-min averaged values taken every 10 min during 24 hours on July 28--29, 1987, when the eastward and westward electrojet were well developed in the afternoon and early morning, respectively. Two coordinate systems called B and E frame are used. The B frame represents the ordinary geomagnetic coordinates where the geomagnetic north and east are taken as x and y axis, respectively. In the E frame, the direction of the horizontal electric field in the ionosphere is parallel to the x axis so that the Hall current always flows in the positive y direction and the Pedersen current in the positive x direction. The correlations in both frames are examined for the x and y component of the ionospheric currents and the corresponding magnetic variation on the ground. The correlation is highest for the y (Hall) current and x magnetic field in the E frame and lowest for the x (Pedersen) current and y magnetic field in the E frame. More detailed quantitative analysis is made by taking into account the dependence on the direction, latitudinal location and nonuniform distribution of the current. The contribution of the Hall current was estimated as 0.56 nT/(A/km), when its center is above the radar station. The Pedersen current also makes contributions of 0.14--0.20 nT/(A/km). The results of this analysis also show that the nighttime level of a quiet day is a suitable choice of the base value for the geomagnetic variations in the auroral zone. ¿ American Geophysical Union 1989