Revisiting Recent Amplitude and Phase Variations of the Chandler Wobble and Free Core Nutation

Abstract

The paper is devoted to the analysis of two components of the Earth’s rotation, Chandler wobble (CW) and free core nutation (FCN). They are oscillations with near-constant periods but variable amplitude and phase. The variations of the amplitude and phase of the CW and FCN have already been considered in the literature, and both showed similar behavior such as a recent significant decrease of the amplitude and large phase change. However, the CW and FCN amplitude and phase variations are, to a large extent, predicted for the current epochs, and their today’s variations need regular updates with obtaining new observations. In this work, the CW and FCN parameters have been re-computed using the latest data and compared with the data published earlier. It was found that the currently obtained amplitude and phase variations generally agreed with the data published earlier. The main difference is that the epochs of the current minimum of amplitude and phase jump or both CW and FCN happened somewhat later than was predicted in previous publications. The delay is about two years for the CW relative to the prediction made in 2010 and about one year for the FCN with respect to the prediction made in 2022.

Continental and oceanic AAM contributions to Chandler Wobble with the amplitude attenuation from 2012 to 2022

“…Previous investigations have identified anomalies of the CW in the 2010s, with changes in atmospheric excitation suggested to be the likely reason (Wang et al 2016;Zotov et al 2022;Malkin 2023;Yamaguchi and Furuya 2024). In this study, we explored deeper into the factors contributing to the reduction in the CW amplitude.…”