Stormtime Pc 5 pulsations are a class of magnetic pulsations observed at synchronous orbit most frequently during the main phase of magnetic storms. The waves are linearly polarized in a meridian plane with nearly equal compressional and transverse components. The waves usually accompany a depression in local field magnitude associated with the onset of a magnetospheric substorm. In this paper, we use local time-universal time maps of mid-latitude magnetic perturbations to study the asociation of thee waves with the development of the partial ring current. We find that these waves occur at the local time of maximum development of the partial ring current, at or shortly after the onset of a magnetospheric substorm. These results confirm our earlier speculation based on satellite data alone that the waves are associated with substorm enhancement of the partial ring current.