A region of density enhancements of thermal heavy ions (O+, O++, and N+) has been observed on numerous occasions by the retarding ion mass spectrometer on the Dynamics Explorer 1 satellite. Our plasmasphere densities of heavy ions are often observed to be up to 2 orders of magnitude higher than equatorward densities within an orbital pass. This phenomenon is almost always observed in the region of the plasmasphere just inside the plasmapause and has been seen at all local times. A statistical study of these heavy ion density enhancements, covering almost 600 passes of DE 1 through the plasmasphere, shows that O+ and O++ enhancements occur over about 64% of the observed passes, with the highest frequency of occurrence being found in the late evening and morning regions. O+ enhancements tend to be seen more frequently in the morning, while O++ enhancements are more likely to be observed in the evening. O+ appears to have a higher outer plasmasphere density enhancement than O++ in all local time regions. Evidence showing that the L shell of the heavy ion density enhancement peaks is dependent upon Dst is presented. Finally, mechanisms for the creation of the heavy ion density enhancements are briefly discussed, including the ''geomagnetic mass spectrometer'' and plasmapause-associated electron heating of the topside ionosphere. ¿ American Geophysical Union 1987