Large subauroral convection velocities are striking features of the vector ion drift measurements made with the RPA's and drift meters on the Atmosphere Explorer satellites. The large AE-C data base has been utilized to investigate the character and morphology of this phenomenon. These latitudinally narrow features are found to be confined predominantly to the local time sector between 18.00 hrs and 02.00 hrs. They occur either singly or as multiple events, one of which nearly always straddles the equatorward edge of the auroral zone. Their occurrence probability as a function of AE index suggests a dependence on magnetic substorm activity.