We analyze the temporal relationship between PMSE (polar mesosphere summer echoes) and long-period vertical motions using the Poker Flat, Alaska radar data. The results show that the vertical velocity leads PMSE by 90¿ to 180¿ with a possible upward trend in phase with increasing frequency. We show that this is consistent with the current PMSE theories which depend primarily upon the presence of charged ice aerosols for the enhancement of radar scatter. ¿ American Geophysical Union 1995