Recent IMAGE Extreme Ultraviolet Imager (EUV) observations showed the first global images of plasmaspheric convection plumes, which have been interpreted as the plasmaspheric tails predicted theoretically 3 decades earlier. Using observations by the IMAGE Radio Plasma Imager (RPI), we show that these convection plumes have large latitudinal extent. These results complement those recently made by others in correlating IMAGE EUV data with measurements of total electron content in the ionosphere. By correlating in situ RPI density measurements with global plasmaspheric EUV images, we have shown that apparently detached plasma structures, as appear in RPI dynamic spectrograms, are in many cases plasmaspheric convection plumes. The temporal separation between the RPI and EUV observations help constrain the interpretation of one data set in the context of the other, thereby enabling an examination of the three-dimensional plasma density structures outside the core plasmasphere. The data sets are mutually reinforcing because the data are collected within a few hours of one another. We used the EUV data to provide unambiguous identification of density enhancements in the region outside the plasmasphere and used the RPI data to obtain accurate number densities and extend information from the EUV data set by measuring densities below the EUV sensitivity threshold.