Large-scale electric fields in the dayside magnetosphere

Observations of auroral dynamics in the polar cusp region is used to derive regularities of the time and space distribution of large-scale electric fields at the magnetopause and in the polar ionosphere. The interpretation of experimental data is based on the supposition that the magnetopause electric field (the reconnection electric field) consists of the potential and vortex components which have different sources in the magnetopause vicinity, and different signatures in the polar ionosphere. Energy sources of magnetic field reconnection at the magnetopause are discussed; the distribution of electric currents in the magnetic barrier region and in the magnetopause vicinity are calculated. There is shown that the magnetopause electric currents are partially closed within the magnetic barrier region. The relationship between the development of electric currents in the day-and night-side auroral zone is considered.