A long standing and vexing problem in magnetospheric physics is mapping the ionosphere to the magnetosphere. To date almost all information on the topic has come from magnetic field mappings. Herein a complementary approach is tried: regions are identified based on the plasma characteristics as observed by low-altitude satellites. Using an automated identification scheme applied to approximately 60,000 individual satellite passes through the dayside oval, probability maps are computed for observing various types of plasma precipitating into the ionosphere. The synthesis of the various individual maps allows the construction of an ionospheric map into the magnetosphere based on plasma characteristics. The results suggest a cusp which is about 2.5 hours in total local time extent; an LLBL which typically extends to about 0900 MLT; and a mantle which reaches to about 0800/1600. Consistent with earlier results, the extension of the nightside region of discrete aurora into the dayside is far more substantial at dusk than at dawn. ¿ American Geophysical Union 1992