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Abstract

We exploit the recent absence of the Chandler wobble (CW) to more simply estimate the Chandler period (P) and Q without using any geophysical excitation data. While we can compute "geodetic CW" by re-integrating the non-seasonal "geodetic excitation" derived with the prescribed P and Q, we should note that the CW could also be derived without assuming any pairs of the P and Q but by simply taking out the annual wobble (AW) from the polar motion time-series data; we here assume that the amplitude changes of AW can be negligible. Denoting the geodetic CW as the CWgeod and the latter as the CWobs, we compare a series of CWgeod with CWobs. Because the two CW are in disagreement during the early- to mid-period due to the lack of the freely damping term in the CWgeod, we focus on to what extent the CWgeod and the CWobs are matching during the recent non-excited period. While this analysis is not strongly sensitive to the P, it turns out that the larger Q (>100) is unlikely and should be below 50. Although the lower Q as much as 25 also gives good agreement, we must include the excitation sources to constrain the lower bound of Q. Indeed, Yamaguchi and Furuya showed that the Q~25 is too low to account for the CW in 1980-2000s.