The direct penetration of electric fields from the polar cap to low latitudes is modulated by interaction of the hot plasma in the magnetosphere with the ionosphere. This interaction drives the Region-2 currents that flow into and out of the auroral region equatorward of the polar cap. The ionospheric electric field associated with these Region-2 currents has a tendency to counteract the east-west component of the electric field coming from the polar cap, and thus
to reduce the penetration of the polar cap electric field toward middle and low latitudes