Three types of Pc 4 pulsations with periods in the range 40--200 s have been identified in the ATS 6 satellite data. Two types are not observed on the ground (80--200 s). Both of these are accompanied by Pc 1--2 activity that is seen simultaneously both at the satellite and on the ground. One of these two types occurs during substorms and coincides with the development of the IPDP subtype of Pc 1--2. The other is observed in the magnetosphere during slow, smooth changes of the background magnetic field during the recovery phase of storms. Pulsation amplitude for these two types is from 5 to several tens of nanoTeslas. The third type of Pc 4 pulsation (T~40--80) has significantly smaller amplitudes in the magnetosphere (A≤5 nT) and can be observed on the ground with amplitudes usually greater than in the magnetosphere. The properties of the first two types of long-period pulsations suggest that the mechanism for their generation is the drift-dissipative instability of the ring current plasma.