The ionosphere as a major supplier of plasma to the
Another important aspect of the ionosphere-magnetosphere interaction is the outflow of plasma from the ionosphere into the magnetosphere. This outflow is so substantial --10**26 ions per second during magnetically disturbed periods near solar maximum-- that the ionosphere could, in principle, fully populate the magnetosphere with plasma. (In fact, the magnetosphere contains a mixture of solar wind and ionospheric plasmas.) The outflow of ions from the ionosphere takes a variety of forms: the supersonic polar wind, ion upwelling from the cleft ion fountain, polar cap outflows, and upward ion conics and beams from the auroral zone. In addition to these high-latitude sources, strong O+ outflows from the mid-latitude ionosphere have been observed at times of intense geomagnetic activity. The strength and composition of the ionospheric plasma outflows vary with geomagnetic activity, season, solar cycle, local time, and altitude. For example, the O+ component of the ionospheric outflow increases with increasing solar and geomagnetic activity, with a corresponding increase in the O+ density of the plasma sheet.