Frequency dependence of the polar motion resonance

SUMMARY The nutation of the Celestial Intermediate Pole can be considered as a retrograde diurnal polar motion. As the common polar motion, it presents a resonance, but with period TPM and quality factor QPM differing from the ones characterizing the Chandler wobble (TCW = 430.2−431.6 d, QCW in the interval (56 255) according to Nastula & Gross): according to the nutation analysis presented in a separate paper, this period is about TPM = 380 d and the quality factor becomes −10. In this study, we aim to revisit the geophysical interpretation of this result. Two complementary factors account for the observed values: the non-equilibrium response of the ocean to the pole tide potential in the diurnal band, and the resonance of the solid Earth tide at the free core nutation period. This leads to a resonance of TPM in the vicinity of the free core nutation period, confirmed by estimates derived from nutation analysis.

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Contribution of a joint Bayesian inversion of VLBI and gravimetric data to the estimation of the free inner core nutation and free core nutation resonance parameters

Geophysical Journal International ◽

10.1093/gji/ggaa181 ◽

2020 ◽

Vol 222 (2) ◽

pp. 845-860

Author(s):

Yann Ziegler ◽

Sébastien B Lambert ◽

Ibnu Nurul Huda ◽

Christian Bizouard ◽

Séverine Rosat

Keyword(s):

Quality Factor ◽

Inner Core ◽

Joint Inversion ◽

Chandler Wobble ◽

Bayesian Inversion ◽

Quality Factors ◽

Free Core Nutation ◽

Gravimetric Data ◽

Vlbi Data

SUMMARY The rotational motions of the internal Earth layers induce resonances in the Earth nutations and tidal gravimetric response to external luni-solar gravitational forcings. The characterization of these resonances is a mean of investigating the deep Earth properties since their amplitudes and frequencies depend on a few fundamental geophysical parameters. In this work, we focus on the determination of the free core nutation and free inner core nutation periods and quality factors from the Bayesian inversion of VLBI and gravimetric data. We make a joint inversion of data from both techniques and show that, even if the results are only slightly different from the inversion of VLBI data alone, such approach may be valuable in the future if the accuracy of gravimetric data increases. We also briefly discuss the polar motion resonance, which is related to the Chandler Wobble as seen from the diurnal frequency band. Our overall estimates of the FCN period and quality factor, TFCN = (−430.2, −429.8) solar days and QFCN = (15 700, 16 700), respectively, are in good agreement with other studies, albeit slightly different for unclear reasons. Despite some concerns about the detection and characterization of the FICN, it seems that we could also successfully estimate its period, TFICN = (+600, +1300) solar days, and give a loose estimate of the upper bound on its quality factor.

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Is Chandler frequency constant?

Symposium - International Astronomical Union ◽

10.1017/s0074180900119734 ◽

1988 ◽

Vol 128 ◽

pp. 359-364 ◽

Cited By ~ 2

Author(s):

Jan Vondrák

Keyword(s):

Polar Motion ◽

Phase Changes ◽

Negative Phase ◽

Chandler Wobble ◽

Probable Explanation ◽

Equilibrium Response ◽

Rapid Changes ◽

Chandler Frequency ◽

Most Probable Explanation ◽

Annual Wobble

The observed polar motion in the period 1860–1985 is analyzed in order to decide whether Chandler frequency was constant. It is shown that while the phase of annual wobble was very stable throughout the interval in question, Chandler wobble phase was subject to sometimes very rapid changes. The most pronounced negative phase changes were always accompanied by extremely low amplitudes, and a significant correlation was found between Chandler wobble phase and its integrated amplitude. The most probable explanation is that the frequency of Chandler wobble is variable and amplitude-dependent, which might be caused by non-equilibrium response of the ocean.

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Dissipation and Ellipticity of the Chandler Wobble

International Astronomical Union Colloquium ◽

10.1017/s0252921100061625 ◽

2000 ◽

Vol 178 ◽

pp. 473-480

Author(s):

Yaozhong Zhu ◽

Buxi Gao

Keyword(s):

Energy Dissipation ◽

Opposite Direction ◽

Polar Motion ◽

Semimajor Axis ◽

Liquid Core ◽

Chandler Wobble ◽

Motion Data ◽

Pole Tide ◽

Chandler Period ◽

Theoretical Results

AbstractThe Chandler wobble, one of the main feature of the Earth’s polar motion, is related to the properties of the mantle and liquid core as well as the mobility of the oceans. The equilibrium pole tide and mantle anelasticity both lengthen the Chandler period, moreover, the former imposes a slight ellipticity on the pole path, and the latter is responsible for the wobble energy dissipation. On the basis of the perturbation principles, we derive the theoretical Qω of the Chandler wobble, assuming that the wobble energy is totally dissipated within the mantle. The theoretical ellipticity and orientation of the semimajor axis of the Chandler wobble path for an anelastic Earth are given. Compared with the results for the elastic Earth, the effect of mantle anelasticity does not change the wobble ellipticity significantly, but slightly changes the orientation of the semimajor axis in the opposite direction. This paper has also proved that the effect of the Earth’s 3-axis feature on the wobble ellipticity is only about 19% of that of the equilibrium pole tide. Analysis of the polar motion data obtained by using modern geodetic techniques shows that the observed ellipticity and orientation of the semimajor axis agree with the theoretical results. We can deduce that the pole tide in the globe should be close to equilibrium.

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Is the Chandler Period Stable?

Symposium - International Astronomical Union ◽

10.1017/s0074180900173383 ◽

1993 ◽

Vol 156 ◽

pp. 303-308

Author(s):

Gao Buxi

Keyword(s):

Fourier Transform ◽

Polar Motion ◽

Chandler Wobble ◽

Deconvolution Method ◽

Motion Data ◽

Probable Explanation ◽

Equilibrium Response ◽

Chandler Period ◽

Non Equilibrium

The problem on Chandler period is an unsolved one. Several authors suggested a hypothesis that the Chandler wobble is only one free period which slightly changes in time and is amplitude-dependent. In this paper we shall make the hypothesis more rigorous than that has been carried yet. A new deconvolution method for Fourier transform is suggested. Using this method the polar motion data are analysed. The analysis results are shown; the Chandler period is not stable and is indeed amplitude-dependent. The probable explanation for the amplitude-dependent of Chandler period is that, which might be caused by non-equilibrium response of the ocean.

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Excitation of the Chandler Wobble

International Astronomical Union Colloquium ◽

10.1017/s0252921100061601 ◽

2000 ◽

Vol 178 ◽

pp. 455-462

Author(s):

N.S. Sidorenkov

Keyword(s):

Polar Motion ◽

Southern Oscillation ◽

World Ocean ◽

Noise Spectrum ◽

Chandler Wobble ◽

The Earth ◽

The Pacific ◽

And Shifts ◽

Chandler Period ◽

Earth’S Inertia Tensor

AbstractThe redistribution of air and water masses between the Pacific and Indian oceans during the El Niño/Southern oscillation (ENSO) changes the components of the Earth’s inertia tensor and shifts the position of the pole of the Earth’s rotation. The spectrum of the ENSO has components with periods of about 6, 3.6, 2.8, and 2.4 years. These periods are all the multiples of the Chandler period T = 1.2 yr. and the principal period of nutation 18.6 yr. A nonlinear model for the Chandler polar motion has been constructed based on this empirical fact. In this model, the ENSO excites the Chandler polar motion by acting on the Earth at the frequencies of combinative resonance. At the same time, the Chandler polar motion induces a polar tide in the atmosphere and the World Ocean, which orders the ENSO. As a result, the dominant components in the noise spectrum of the ENSO are those with the periods indicated above.

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Spin rotation, Chandler wobble and free core nutation of isolated multi-layer pulsars

Proceedings of the International Astronomical Union ◽

10.1017/s1743921312024246 ◽

2012 ◽

Vol 8 (S291) ◽

pp. 392-392

Author(s):

Alexander Gusev ◽

Irina Kitiashvili

Keyword(s):

Neutron Star ◽

Differential Rotation ◽

Heat Dissipation ◽

Inner Core ◽

Outer Core ◽

Chandler Wobble ◽

Time Of Arrival ◽

Layer Model ◽

Free Core Nutation ◽

Rotation Pole

AbstractAt present time there are investigations of precession and nutation for very different celestial multi-layer bodies: the Earth (Getino 1995), Moon (Gusev 2010), planets of Solar system (Gusev 2010) and pulsars (Link et al. 2007). The long-periodic precession phenomenon was detected for few pulsars: PSR B1828-11, PSR B1557-50, PSR 2217+47, PSR 0531+21, PSR B0833-45, and PSR B1642-03. Stairs, Lyne & Shemar (2000) have found that the arrival-time residuals from PSR B1828-11 vary periodically with a different periods. According to our model, the neutron star has the rigid crust (RC), the fluid outer core (FOC) and the solid inner core (SIC). The model explains generation of four modes in the rotation of the pulsar: two modes of Chandler wobble (CW, ICW) and two modes connecting with free core nutation (FCN, FICN) (Gusev & Kitiashvili 2008). We are propose the explanation for all harmonics of Time of Arrival (TOA) pulses variations as precession of a neutron star owing to differential rotation of RC, FOC and crystal SIC of the pulsar PSR B1828-11: 250, 500, 1000 days. We used canonical method for interpretation TOA variations by Chandler Wobble (CW) and Free Core Nutation (FCN) of pulsar.The two - layer model can explain occurrence twin additional fashions in rotation pole motion of a NS: CW and FCN. In the frame of the three-layer model we investigate the free rotation of dynamically-symmetrical PSR by Hamilton methods. Correctly extending theory of SIC-FOC-RC differential rotation for neutron star, we investigated dependence CW, ICW, FCN and FICN periods from flatness of different layers of pulsar.Our investigation showed that interaction between rigid crust, RIC and LOC can be characterized by four modes of periodic variations of rotation pole: CW, retrograde Free Core Nutation (FCN), prograde Free Inner Core Nutation (FICN) and Inner Core Wobble (ICW). In the frame of the three-layer model we proposed the explanation for all pulse fluctuations by differential rotation crust, outer core and inner core of the neutron star and received estimations of dynamical flattening of the pulsar inner and outer cores, including the heat dissipation. We have offered the realistic model of the dynamical pulsar structure and two explanations of the feature of flattened of the crust, the outer core and the inner core of the pulsar.

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