Chandler Wobble and Free Core Nutation: Theory and Features

Being a torque free motion of the rotating Earth, Chandler wobble is the major component in the Earth's polar motion with amplitude about 0.05-0.2 arcsec and period about 430-435 days. Free core nutation, also called nearly diurnal free wobble, exists due to the elliptical core-mantle boundary...

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Published inJournal of astronomy and space sciences Vol. 36; no. 1; pp. 11 - 20
Main Authors Na, Sung-Ho, Roh, Kyoung-Min, Cho, Jungho, Yoo, Sung-Moon, Choi, Byungkyu, Yoon, Hasu
Format Journal Article
LanguageKorean
Published 2019
Subjects
Chandler wobble
free core nutation
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Summary:Being a torque free motion of the rotating Earth, Chandler wobble is the major component in the Earth's polar motion with amplitude about 0.05-0.2 arcsec and period about 430-435 days. Free core nutation, also called nearly diurnal free wobble, exists due to the elliptical core-mantle boundary in the Earth and takes almost the whole part of un-modelled variation of the Earth's pole in the celestial sphere beside precession and nutation. We hereby present a brief summary of their theories and report their recent features acquired from updated datasets (EOP C04 and ECMWF) by using Fourier transform, modelling, and wavelet analysis. Our new findings include (1) period-instability of free core nutation between 420 and 450 days as well as its large amplitude-variation, (2) re-determined Chandler period and its quality factor, (3) fast decrease in Chandler amplitude after 2010.
Bibliography:KISTI1.1003/JNL.JAKO201912761598715
ISSN:2093-5587
2093-1409