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The First-time Absence of Chandler Wobble since 2015 in the Observation History
  • Ryuji Yamaguchi,
  • Masato Furuya
Ryuji Yamaguchi
Hokkaido University

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Masato Furuya
Hokkaido University
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Abstract

The Chandler Wobble (CW) period is considered a single time-invariable constant, ~1.2 years, but the possible time-variability has not been examined using modern space-geodetic data. We first examined whether the Chandler period could vary with time on the assumption of minimum excitation power. Unexpectedly, the estimated Chandler period has been shortened by more than 60 days since about 2005. Moreover, by simple least-squares modeling, we found that CW started to be weaker in 2005 and almost disappeared in 2015. We interpret these results in both excitation and wobble domains as caused by the absence of CW for the first time in the observation history. Assuming no excitations of CW since 2005, the rather abrupt damping suggests the Q-value is below 25. Meanwhile, the analyses of the available atmospheric and oceanic angular momentum (AAM/OAM) functions indicate the significant amplitude of CW even after 2005, implying that the AAM/OAM functions are incomplete.