ABSTRACT
Magnetic reconnection will drive a tailward plasma flow on open field lines across the polar caps and the magnetospheric lobes, while viscous-like processes will drive a tailward plasma flow in the low-latitude boundary layers which are threaded by closed field lines. The electric field pattern in the auroral oval reflects the large-scale pattern of magnetospheric plasma convection associated with the solar wind-magnetosphere coupling. During magnetospheric substorms the ionospheric current flow is affected in two ways to accommodate for the enhanced energy input from the solar wind via increased dissipation. While the nightside auroral currents are governed by processes taking place in the magnetospheric equatorial plane, the currents flowing in and near the polar cusp and in the dayside polar cap are connected along magnetic field lines to the vicinity of the magnetopause. In a sense, the magnetosphere-ionosphere coupling is the interaction of different physical processes taking place in either of the ionosphere and the magnetosphere regions.
