Data from two intervals when pulsation activity was simultaneously observed on both ATS 1 and Ogo 5 satellites are presented. The first example, a Pc 4, indicates that this pulsation is caused by a field line near L=7 resonating in its second-harmonic mode. This is inferred from both plasma density measurements and polarization characteristics. The wave was not observed at three ground stations in the vicinity of the satellite conjugate points. This indicates that Pc 4 waves are very localized in latitude and that a close array (<100 km) is needed to perform effective correlation with satellites. The second event, which is also in the Pc 4 band, can again be inferred to be a field line resonance from the polarization characteristics.