Inversion of polar motion data: Chandler wobble, phase jumps, and geomagnetic jerks

Abstract

We reconsider the analysis of the polar motion with a method totally different from the wavelet analysis used in previous papers. The total polar motion is represented as the sum of oscillating annual and Chandler terms whose amplitude and phase perturbations are inverted with a nonlinear simulated annealing method. The phase variations found in previous papers are confirmed with the huge phase change (≈3π/2) occurring in the 1926–1942 period and another less important one (≈π/3) in the 1970–1980 epoch. The best Chandler period, Tc, is found to be 434 ± 0.5 mean solar days. The epochs of significant phase changes found in the Chandler wobble are also those where important geomagnetic jerks occur in the secular variation of the geomagnetic field. Turbulent viscous friction produced by small‐scale topography at the core‐mantle boundary might be responsible for the observed phase jumps.