Strong evidence for the harmonic structure of Pc 3--5 magnetic pulsations observed on the ground has been provided by extracting coherent oscillations from magnetic pulsation data recorded at the Syowa-Husafell conjugate pair near L=6 and then calculating the phase difference of the H components between the conjugate points as a function of local time. The model calculation suggests that the Pc 4/5 band observed in the frequency range ~3--10 mHz is the fundamental mode of standing shear Alfven waves near L=6, while the Pc 3 band with multiple harmonic structure observed in the frequency range ~20--100 mHz is the higher harmonics (usually third to sixth harmonics). The second harmonic is not notable in comparison with other harmonics. It is found further that the fundamental mode and the higher harmonics are not always excited simultaneously. Therefore it is likely that when the frequency of the external driving source is in the Pc 3 range, it excites higher harmonics of standing near Alfven waves near L=6, while when the frequency of the external driving source is in the Pc 4/5 range, it excites the fundamental mode.