The dynamical behavior of the plasmapause is studied using whistlers recorded at Siple, Antarctica (~84¿W, L~4) during June 17--22, 1973. The magnetic activity during this period remained fairly disturbed until June 21, causing the plasmapause to contract to less than 3 earth radii (RE). Sudden quieting on June 22 caused the plasmasphere to develop complex outlying structures with the high density region extending out to about 6 RE. The plasmapause data show a repeated diurnal pattern of a relatively slow decrease in equatorial radius by ~0.5--1 RE during the night and a more rapid increase by about the same amount near dusk when the plasmasphere bulge is encountered. These data should provide a basis for detailed correlative studies of many plasmapause-associated phenomena.