Nocturnal winter increases in total electron content are observed at Bozeman, Boulder, and Dallas with the ATS 6 radio beacon. Results of this investigation suggest that the increases take place mainly in the ionosphere. Changes in plasmaspheric contents are much smaller. The downward motion of the F2 layer and the east-to-west movement of the nocturnal maximum (NM) suggest the presence of an electric field. A westward electric field will move plasma from higher L shells to lower L shells with smaller volumes and thus increase the plasma pressure, the result being an enhanced flow of plasma from plasmasphere to ionosphere. The total flux required to produce the NM is of the order of 1¿1013 m-2 s-1.