Characteristics of the chandler wobble

We carried out a spectral analysis (by FFT and periodograms) on a homogenized set of data of coordinates of the Earth's pole in the period 1900–1969.9, and found the Chandler wobble to have 4 peaks at periods of 1.142, 1.169, 1.199 and 1.230 years. The two main peaks at 1.169 and 1.199 years have equal amplitudes (TABLE 4 and Fig. 1). According to Fedrov and Yatskiv's (1964) interpretation of sudden phase changes, our data would give a natural period of 1.184 years, but the observed asymmetry between the two secondary peaks is a difficulty for this interpretation. The observed multiplicity of peaks can also be explained by the theory of amplitude modulation, if we suppose there is a modulating oscillation with a period around 48 years. In this case, the natural period of the Chandler wobble would be 1.199 years; but this interpretation also has some difficulties.