Theories and observations of ion energization and outflow in the high latitude magnetosphere

A review is given of several mechanisms causing outflow at high latitudes of ionospheric ions to the terrestrial magnetosphere. The upward ion motion along the geomagnetic field can be divided into several categories, including polar wind, bulk ion outflow in the auroral region, upwelling ions and ion conics and beams. More than one ion energization mechanism can be operating within each category, and a combination of categories is important for the total ion outflow.