On October 29--31, 2003, the ground observations of field line resonance signals and the total electron content (TEC) along the 330th magnetic meridian recorded extraordinary density variations in both the magnetosphere and the ionosphere. In the magnetosphere, the density decreased at outer L shells due to strong convection, whereas it increased significantly in the afternoon sector at L ≤ 4. In the ionosphere, a strong positive storm occurred at low latitudes, and storm enhanced density was also observed at approximately 1400 LT in mid-latitude regions. The density enhancements in both the magnetosphere and ionosphere coincided with intervals of southward IMF and high-speed solar wind, consistent with the scenario that the eastward electric field imposed on the ionosphere led to a positive storm which might contribute to the dense plasmaspheric drainage plume. These results demonstrate that the ionosphere can be an important factor modulating the density variations in a storm-time plasmasphere.