[en] The dependence of the polar cap magnetic disturbance on the polarity and magnitude of the Z component of the interplanetary magnetic field is investigated by regression analysis using hourly values. The Svalgaard-Mansurov effect has been eliminated by assuming a linear dependence on the Y component of the interplanetary field. It is shown that as the northward component of the interplanetary magnetic field increases, a characteristic current system appears in the polar cap. This current system is composed of two current vortices in the day side polar cap: one in the prenoon sector and the other in the afternoon sector. The current direction is antisunward in the central polar cap, suggesting that sunward plasma convection is induced in the polar cap. Current intensity is strongest at phi/subM/approx.84degree around the noon meridian. It is proposed that the tail field lines are reconnected with the northward interplanetary field on the polar side of the day side polar cusp and, as a result, that plasma convection is induced which is closed within the high-latitude magnetosphere. On the other hand, when the interplanetary magnetic field is directed southward, a transpolar current sheet appears, covering the whole polar cap (phi/subM/> or =77.5degree). The characteristics of this transpolar current sheets are given