The newly introduced indexPCfor magnetic activity in the polar cap has been examined to establish to which extent it can serve as an indicator of auroral electrojet activity.PCis derived from a single nearpole station, as a 15‐min average index. We have derived it for two stations, one in the northern hemisphere (Thule) and one in the southern hemisphere (Vostok). The simplicity of thePCindex enables us to make a large data base for statistical investigations. We have thus used 7 years ofPCvalues for the two stations to analyze the relationship betweenPCand the auroral zone indicesAE,AU, andALstatistically. We find a very high correlation betweenPCandAEduring winter and equinox, the linear correlation coefficient being ≈0.8–0.9 for Thule and ≈0.7–0.8 for Vostok. During summer the correlation is less because thePCindex is then disturbed by polar cap currents controlled by the northward and east‐west components of the interplanetary magnetic field. We therefore stress the importance of havingPCavailable from both the northern and southern hemisphere. From event studies we find thatPCis sensitive both toDP2 type electrojet activity and to substorm intensifications of the westward electrojet in the midnight or postmidnight sector but less sensitive to substorm intensifications of the westward electrojet in the premidnight sector. We conclude thatPCcan serve as a fast available indicator ofDP2 andDP1 activity in the polar regions, excluding intrusions of the westward electrojet in the premidn