Magnetospheric convection during quiet or moderately disturbed times

We review the main processes which contribute to the large‐scale plasma circulation in the environment of the Earth during quiet times or during reasonably stable magnetic conditions (when the concept of average pattern of plasma convection can make sense). Since field‐aligned currents are the way by which plasma motion perpendicular to the magnetic field is transmitted between the remote regions (solar wind, magnetosphere) and the ionosphere, we describe the processes driving plasma convection as processes generating field‐aligned currents. The electric field distribution will then result as a consequence of the coupling between the regions generating field‐aligned current and the circuit constituted by the ionospheric conducting layer. We discuss the effects of horizontal gradients of ionospheric conductivities on the resulting electric field distribution. As concerns the mechanisms which drive field‐aligned currents, the convective derivative of plasma flow vorticity, produced by the flow deceleration of the solar wind, is believed to be the main generator for region 1 currents, whereas the azimuthal pressure gradients within the region of closed field lines are believed, in the classical view, to be the main generators for region 2 currents. In turn, we recognize two kinds of sources for producing azimuthal pressure gradients in the region of closed field lines, and we illustrate them in the framework of linear theory. These are (1) the adiabatic distortion of the distribution of energetic trapped plasma from azimuthally symmetric distribution in the presence of an electric field and (2) particle losses undergone by the plasma while it is azimuthally convected.