The plasmapause position has been measured quite well by the light ion mass spectrometer aboard OGO 5, which measures the concentrations of H+, He+, and O+ions as a function ofLand local time. The influence of magnetic activity on this plasmapause position has been studied for the local‐time regions at 1000±2 hours and 0200±2 hours. The plasmapause location shows a general decrease in radius with increasing activity in both regions. The time lag between the onset of magnetic activity and the change in plasmapause radius is found to be about 2 to 6 hours for the 0200 local‐time region. However, the time lag for the 1000 local‐time region is not well defined, although the 6‐hour lag time seemed to fit some of the cases better than the 12‐ or 24‐hour periods that were examined. By using the 2‐ to 6‐hour response time, the plasmapause density profiles in the 0200 local‐time region were grouped according to magnetic activity. This grouping displays the typical plasmapause reaction in this local‐time region to increasing magnetic activity with the knee position moving to lowerLvalues, the sharpness of the knee increasing, and the total concentration levels inside and outside the knee remaining approximately the same at 10³ ions/cm³ and