For the large geomagnetic disturbance on April 11, 2001, we combine data from the Millstone Hill radar, a network of GPS TEC receivers, and the DMSP F-12 and IMAGE satellites, to estimate the sunward flux of thermal plasma associated with erosion of the outer plasmasphere/ionosphere in the dusk sector. Direct radar observations of the E ¿ B advection of SED plasma determine a flux of >10E26 ions/s to the noontime cusp at F-region heights. DMSP in situ observations provide a similar estimate. Assuming a dipolar magnetic field, we project our low-altitude observations into the outer plasmasphere, obtaining a total sunward flux of >10E27 ions/s. High-altitude IMAGE EUV observations of the plasmasphere drainage plume provides an estimate of 1.5 ¿ 10E27 ions/s for the sunward flux. Such rates of sunward plasma transport are sufficient to deplete a 1-Re shell of the outer plasmasphere in ~1 hour.