scholarly journals Nature and Properties of the Chandler Motion and Mechanism of its Damping and Excitation

2000 ◽  
Vol 178 ◽  
pp. 447-453 ◽  
Author(s):  
J.M. Ferrándiz ◽  
Yu. V. Barkin
Keyword(s):  
Analytical Solution ◽  
Polar Motion ◽  
The Body ◽  
Lower Envelope ◽  
Meridian Plane ◽  
The Earth ◽  
Deformable Bodies ◽  
Characteristic Behaviour ◽  
Special Approach ◽  
Chandler Period

AbstractThe analytical studies of the Chandler motion of the Earth’s pole on the basis of the special approach to the problem, using the canonical and noncanonical equations in the Andoyer elastic variables (Barkin, et al. 1995; Barkin, 1996; in press) have been fulfilled. The Earth is considered as an isolated celestial body with the anelastic (in general case) external envelope (the mantle) and an invariant central part (the core).The interpretation of the Chandler motion of the body, deformed by its own rotation, was given in the case of an elastic envelope. It was shown that the body rotates as a fictitious rigid body with different moments of inertia. The analytical solution of the problem let us explain the next properties of the motion of the deformable bodies: 1) observed period of the Earth’s polar motion; 2) ellipticity of the pole trajectory and difference of the eccentricities of the Chandler and Euler motions; 3) nonuniform velocity of the counter-clockwise polar motion along the Chandler ellipse; 4) orientation of this ellipse (its minor axis is located in the meridian plane, at 14.5 W degrees).The influence of the dissipation on the damping of the Chandler polar motion was studied. The analytical solution of the problem was obtained for the simplest treatment of the delay of the tides caused by the Earth’s rotation (Getino & Ferrándiz 1991; Kubo, 1991). This model explains the characteristic behaviour of the amplitude of the Chandler motion in the periods 1905–1920, 1943–1960 (Vondrák, & Cyril, 1966). The excitation of the Chandler motion can be explained by the upper and lower envelope displacements (Barkin, 1999) with Moon-Sun forced attraction with a period of 412 days, close to the Chandler period.

Theories of Polar Motion from Tisserand to Poincaré (1890 – 1910)

2000 ◽  
Vol 178 ◽  
pp. 41-66 ◽  
Author(s):  
P. Melchior
Keyword(s):  
Polar Motion ◽  
Scientific Community ◽  
Circular Motion ◽  
Computing Power ◽  
The Earth ◽  
Fixed Pole ◽  
One Year ◽  
Elliptical Motion ◽  
The Impact ◽  
Chandler Period

AbstractThe discovery by Seth C. Chandler (1891) that the motion of the pole (the reality of which had been established by K.F. Küstner and by the simultaneous latitude observations at Honolulu and Berlin by German astronomers) resulted from two components i.e. a free circular motion with a period of 427 days and a forced elliptical motion with a period of 365.25 days, raised considerable interest in the scientific community of astronomers and geophysicists.The celebrated Mécanique Céleste of Tisserand (1890) had been published just one year before at a time when doubts still persisted and arguments could be presented in favor of the fixed pole. Starting with Tisserand’s arguments, we describe in this paper the impact of the successive contributions by A. Greenhill, S. Newcomb, Th. Sloudsky, S. Hough, G. Herglotz, A. Love, J. Larmor and H. Poincaré to the solution of the problems raised by the Chandler period.The lines of reasoning taken by these eminent scientists were rigorously correct so that, after about one hundred years, contemporary researchers, who benefit from a far better knowledge of the inner structure of the Earth and are able to take advantage of modern computing power, do not contradict any of their conclusions and instead refine them with an accuracy which was not imaginable one century ago.

scholarly journals Excitation of the Chandler Wobble

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.

scholarly journals On the Chandler periodicity (Polar Motion, LOD and Climate)

2000 ◽  
Vol 178 ◽  
pp. 397-402
Author(s):  
F. Buffa ◽  
A. Poma
Keyword(s):  
Time Series ◽  
Polar Motion ◽  
Superconducting Gravimeter ◽  
Spin Axis ◽  
Rainfall Time Series ◽  
Observation Level ◽  
Motion Data ◽  
The Earth ◽  
Chandler Period ◽  
Free Nutation

AbstractThe 14-month Chandler period is associated with the free nutation of the Earth about its spin axis. The observed value of the Chandler period comes usually from the analysis of astronomical series of polar motion data as well as from superconducting gravimeter measurements. At the observation level a periodicity of about 420–440 days also was noticed in microseismic activities. Recently we found evidence of a signal with period similar to the Chandler one in the Sardinia rainfall time series.

Reference Coordinate System Requirements for Geophysics

1975 ◽  
Vol 26 ◽  
pp. 87-92
Author(s):  
P. L. Bender
Keyword(s):  
Coordinate System ◽  
Polar Motion ◽  
Main Part ◽  
Measurement Techniques ◽  
Reference Points ◽  
Angular Motion ◽  
Coordinate Systems ◽  
Axis Of Rotation ◽  
The Earth ◽  
Fixed System

AbstractFive important geodynamical quantities which are closely linked are: 1) motions of points on the Earth’s surface; 2)polar motion; 3) changes in UT1-UTC; 4) nutation; and 5) motion of the geocenter. For each of these we expect to achieve measurements in the near future which have an accuracy of 1 to 3 cm or 0.3 to 1 milliarcsec.From a metrological point of view, one can say simply: “Measure each quantity against whichever coordinate system you can make the most accurate measurements with respect to”. I believe that this statement should serve as a guiding principle for the recommendations of the colloquium. However, it also is important that the coordinate systems help to provide a clear separation between the different phenomena of interest, and correspond closely to the conceptual definitions in terms of which geophysicists think about the phenomena.In any discussion of angular motion in space, both a “body-fixed” system and a “space-fixed” system are used. Some relevant types of coordinate systems, reference directions, or reference points which have been considered are: 1) celestial systems based on optical star catalogs, distant galaxies, radio source catalogs, or the Moon and inner planets; 2) the Earth’s axis of rotation, which defines a line through the Earth as well as a celestial reference direction; 3) the geocenter; and 4) “quasi-Earth-fixed” coordinate systems.When a geophysicists discusses UT1 and polar motion, he usually is thinking of the angular motion of the main part of the mantle with respect to an inertial frame and to the direction of the spin axis. Since the velocities of relative motion in most of the mantle are expectd to be extremely small, even if “substantial” deep convection is occurring, the conceptual “quasi-Earth-fixed” reference frame seems well defined. Methods for realizing a close approximation to this frame fortunately exist. Hopefully, this colloquium will recommend procedures for establishing and maintaining such a system for use in geodynamics. Motion of points on the Earth’s surface and of the geocenter can be measured against such a system with the full accuracy of the new techniques.The situation with respect to celestial reference frames is different. The various measurement techniques give changes in the orientation of the Earth, relative to different systems, so that we would like to know the relative motions of the systems in order to compare the results. However, there does not appear to be a need for defining any new system. Subjective figures of merit for the various system dependon both the accuracy with which measurements can be made against them and the degree to which they can be related to inertial systems.The main coordinate system requirement related to the 5 geodynamic quantities discussed in this talk is thus for the establishment and maintenance of a “quasi-Earth-fixed” coordinate system which closely approximates the motion of the main part of the mantle. Changes in the orientation of this system with respect to the various celestial systems can be determined by both the new and the conventional techniques, provided that some knowledge of changes in the local vertical is available. Changes in the axis of rotation and in the geocenter with respect to this system also can be obtained, as well as measurements of nutation.

‘Man Is Ill Because He Is Badly Constructed’: Artaud, Klossowski and Deleuze in Search for the Earth Inside

2011 ◽  
Vol 5 (1) ◽  
pp. 18-34 ◽  
Author(s):  
Rick Dolphijn
Keyword(s):  
Performance Art ◽  
Holy Spirit ◽  
The Body ◽  
Deleuze And Guattari ◽  
The Earth ◽  
The Holy Spirit ◽  
Life Itself ◽  
Body Without Organs ◽  
Ways Of Thinking ◽  
And Performance

Starting with Antonin Artaud's radio play To Have Done With The Judgement Of God, this article analyses the ways in which Artaud's idea of the body without organs links up with various of his writings on the body and bodily theatre and with Deleuze and Guattari's later development of his ideas. Using Klossowski (or Klossowski's Nietzsche) to explain how the dominance of dialogue equals the dominance of God, I go on to examine how the Son (the facialised body), the Father (Language) and the Holy Spirit (Subjectification), need to be warded off in order to revitalize the body, reuniting it with ‘the earth’ it has been separated from. Artaud's writings on Balinese dancing and the Tarahumaran people pave the way for the new body to appear. Reconstructing the body through bodily practices, through religion and above all through art, as Deleuze and Guattari suggest, we are introduced not only to new ways of thinking theatre and performance art, but to life itself.

‘A pinch of unseen, unguarded dust’: The World and Self in Thomas Hardy's Poems

2018 ◽  
Vol 8 (1) ◽  
pp. 49-66
Author(s):  
Monika Szuba
Keyword(s):  
The Body ◽  
The Self ◽  
Phenomenological Philosophy ◽  
The Earth ◽  
The World ◽  
The Universe ◽  
Recurrent Theme ◽  
Body Subject

The essay discusses selected poems from Thomas Hardy's vast body of poetry, focusing on representations of the self and the world. Employing Maurice Merleau-Ponty's concepts such as the body-subject, wild being, flesh, and reversibility, the essay offers an analysis of Hardy's poems in the light of phenomenological philosophy. It argues that far from demonstrating ‘cosmic indifference’, Hardy's poetry offers a sympathetic vision of interrelations governing the universe. The attunement with voices of the Earth foregrounded in the poems enables the self's entanglement in the flesh of the world, a chiasmatic intertwining of beings inserted between the leaves of the world. The relation of the self with the world is established through the act of perception, mainly visual and aural, when the body becomes intertwined with the world, thus resulting in a powerful welding. Such moments of vision are brief and elusive, which enhances a sense of transitoriness, and, yet, they are also timeless as the self becomes immersed in the experience. As time is a recurrent theme in Hardy's poetry, this essay discusses it in the context of dwelling, the provisionality of which is demonstrated in the prevalent sense of temporality, marked by seasons and birdsong, which underline the rhythms of the world.

Magneto-inertial waves and planetary rotation

2021 ◽  
Author(s):  
Jérémy Rekier ◽  
Santiago Triana ◽  
Véronique Dehant
Keyword(s):  
Magnetic Field ◽  
Polar Motion ◽  
Density Stratification ◽  
Length Of Day ◽  
Inertial Waves ◽  
Torsional Oscillations ◽  
The Core ◽  
The Earth ◽  
Planetary Rotation ◽  
The Magnetic Field

<p>Magnetic fields inside planetary objects can influence their rotation. This is true, in particular, of terrestrial objects with a metallic liquid core and a self-sustained dynamo such as the Earth, Mercury, Ganymede, etc. and also, to a lesser extent, of objects that don’t have a dynamo but are embedded in the magnetic field of their parent body like Jupiter’s moon, Io.<br>In these objects, angular momentum is transfered through the electromagnetic torques at the Core-Mantle Boundary (CMB) [1]. In the Earth, these have the potential to produce a strong modulation in the length of day at the decadal and interannual timescales [2]. They also affect the periods and amplitudes of nutation [3] and polar motion [4]. <br>The intensity of these torques depends primarily on the value of the electric conductivity at the base of the mantle, a close study and detailed modelling of their role in planetary rotation can thus teach us a lot about the physical processes taking place near the CMB.</p><p>In the study of the Earth’s length of day variations, the interplay between rotation and the internal magnetic field arrises from the excitation of torsional oscillations inside the Earth’s core [5]. These oscillations are traditionally modelled based on a series of assumptions such as that of Quasi-Geostrophicity (QG) of the flow inside the core [6]. On the other hand, the effect of the magnetic field on nutations and polar motion is traditionally treated as an additional coupling at the CMB [1]. In such model, the core flow is assumed to have a uniform vorticity and its pattern is kept unaffected by the magnetic field. </p><p>In the present work, we follow a different approach based on the study of magneto-inertial waves. When coupled to gravity through the effect of density stratification, these waves are known to play a crucial role in the oscillations of stars known as magneto-gravito-inertial modes [7]. The same kind of coupling inside the Earth’s core gives rise to the so-called MAC waves which are directly and conceptually related to the aforementioned torsional oscillations [8]. </p><p>We present our preliminary results on the computation of magneto-inertial waves in a freely rotating planetary model with a partially conducting mantle. We show how these waves can alter the frequencies of the free rotational modes identified as the Free Core Nutation (FCN) and Chandler Wobble (CW). We analyse how these results compare to those based on the QG hypothesis and how these are modified when viscosity and density stratification are taken into account. </p><p>[1] Dehant, V. et al. Geodesy and Geodynamics 8, 389–395 (2017). doi:10.1016/j.geog.2017.04.005<br>[2] Holme, R. et al. Nature 499, 202–204 (2013). doi:10.1038/nature12282<br>[3] Dumberry, M. et al. Geophys. J. Int. 191, 530–544 (2012). doi:10.1111/j.1365-246X.2012.05625.x<br>[4] Kuang, W. et al. Geod. Geodyn. 10, 356–362 (2019). doi:10.1016/j.geog.2019.06.003<br>[5] Jault, D. et al. Nature 333, 353–356 (1988). doi:10.1038/333353a0<br>[6] Gerick, F. et al. Geophys. Res. Lett. (2020). doi:10.1029/2020gl090803<br>[7] Mathis, S. et al. EAS Publications Series 62 323-362 (2013). doi: 10.1051/eas/1362010<br>[8] Buffett, B. et al. Geophys. J. Int. 204, 1789–1800 (2016). doi:10.1093/gji/ggv552</p>

Chelyabinsk Meteorite

2021 ◽  
Author(s):  
Olga Popova
Keyword(s):  
Energy Deposition ◽  
Seismic Waves ◽  
The Body ◽  
Structure And Properties ◽  
Ural Mountains ◽  
Asteroid Impact ◽  
Unusual Event ◽  
The Earth ◽  
First Time

The asteroid impact near the Russian city of Chelyabinsk on February 15, 2013, was the largest airburst on Earth since the 1908 Tunguska event, causing a natural disaster in an area with a population exceeding 1 million. On clear morning at 9:20 a.m. local time, an asteroid about 19 m in size entered the Earth atmosphere near southern Ural Mountains (Russia) and, with its bright illumination, attracted the attention of hundreds of thousands of people. Dust trail in the atmosphere after the bolide was tens of kilometers long and was visible for several hours. Thousands of different size meteorites were found in the areas south-southwest of Chelyabinsk. A powerful airburst, which was formed due to meteoroid energy deposition, shattered thousands of windows and doors in Chelyabinsk and wide surroundings, with flying glass injuring many residents. The entrance and destruction of the 500-kt Chelyabinsk asteroid produced a number of observable effects, including light and thermal radiation; acoustic, infrasound, blast, and seismic waves; and release of interplanetary substance. This unexpected and unusual event is the most well-documented bolide airburst, and it attracted worldwide attention. The airburst was observed globally by multiple instruments. Analyses of the observational data allowed determination of the size of the body that caused the superbolide, its velocity, its trajectory, its behavior in the atmosphere, the strength of the blast wave, and other characteristics. The entry of the 19-m-diameter Chelyabinsk asteroid provides a unique opportunity to calibrate the different approaches used to model meteoroid entry and to calculate the damaging effects. The recovered meteorite material was characterized as brecciated LL5 ordinary chondrite, in which three different lithologies can be distinguished (light-colored, dark-colored, and impact-melt). The structure and properties of meteorites demonstrate that before encountering Earth, the Chelyabinsk asteroid had experienced a very complex history involving at least a few impacts with other bodies and thermal metamorphism. The Chelyabinsk airburst of February 15, 2013, was exceptional because of the large kinetic energy of the impacting body and the damaging airburst that was generated. Before the event, decameter-sized objects were considered to be safe. With the Chelyabinsk event, it is possible, for the first time, to link the damage from an impact event to a well-determined impact energy in order to assess the future hazards of asteroids to lives and property.

Overview and Proposition for a Modern Definition of the CEP

2000 ◽  
Vol 178 ◽  
pp. 571-584
Author(s):  
Nicole Capitaine
Keyword(s):  
Working Group ◽  
Polar Motion ◽  
Earth Orientation Parameters ◽  
Earth Orientation ◽  
The Earth ◽  
Conventional Models ◽  
Definition Of ◽  
Orientation Parameters ◽  
Observational Procedure

AbstractThe current IAU conventional models for precession and nutation are referred to the Celestial Ephemeris Pole (CEP). However, the concept corresponding to the CEP is not clear and cannot easily be extended to the most recent models and observations. Its realization is actually dependent both on the model used for precession, nutation and polar motion and on the observational procedure for estimating the Earth orientation parameters. A new definition of the CEP should therefore be given in order to be in agreement with modern models and observations at a microarsecond level. This paper reviews the various realizations of the pole according to the models and observations and discusses the proposals for a modern definition of the CEP that are under consideration within the work of the subgroup T5 entitled “Computational Consequences” of the “ICRS” IAU Working Group.

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