On modulations of the Chandler wobble excitation

We derive the Chandler wobble excitation from the polar motion (PM) observations by using the Panteleev corrective filtering. The latter method is based on inversion of the Euler–Liouville equation, with additional filtering in the Chandler frequency band. The excitation reconstruction reveals amplitude changes different from the one observed in the Chandler wobble itself. Their main feature, well observable over the length of the day (LOD), is the presence of a 18.6-year amplitude modulation synchronous with the lunar orbital precession cycle and tidal effects. The filtering of oceanic and atmospheric excitation in the Chandler frequency band also reveals a coherent 18.6-year oceanic pattern. Most probably the ocean provide a channel for the tidal energy transfer.

► Chandler excitation reconstructed from the polar motion observations.
► The Panteleev corrective filtering was used to solve the inverse problem.
► 18.6 years modulation found in the excitation.
► AAM and OAM filtered in the Chandler frequency band.
► Good correspondence found between the reconstructed (geodetic) and geophysical excitation.