共查询到20条相似文献，搜索用时 31 毫秒
1.
Perturbed, rotational-oscillational motions of the Earth induced by the gravitational torques exerted by the Sun and Moon are studied using a linear mechanical model for a viscoelastic rigid body. A tidal mechanism is identified for the excitation of polar oscillations, i.e., for oscillations of the angular-velocity vector specified in a fixed coordinate frame, attributed to the rotational-progressive motion of the barycenter of the Earth-Moon “binary planet” about the Sun. The main features of the oscillations remain stable and do not change considerably over time intervals significantly exceeding the precessional period of the Earth’s axis. A simple mathematical model containing two frequencies, namely, the Chandler and annual frequencies, is constructed using the methods of celestial mechanics. This model is adequate to the astrometric measurements performed by the International Earth Rotation Service (IERS). The parameters of the model are identified via least-squares fitting and a spectral analysis of the IERS data. Statistically valid interpolations of the data for time intervals covering from several months to 15–20 yr are obtained. High-accuracy forecasting of the polar motions for 0.5–1 yr and reasonably trustworthy forecasting for 1–3 yr demonstrated by observations over the last few years are presented for the first time. The results obtained are of theoretical interest for dynamical astronomy, geodynamics, and celestial mechanics, and are also important for astrometrical, navigational, and geophysical applications. 相似文献
2.
A numerical–analytical approach is used to investigate irregular effects in oscillations of the Earth’s pole related to variations in the Chandler and annual components. An approach to studying oscillations in the motion of the Earth’s pole based on a joint analysis of the Chandler and annual components of this motion is proposed. A transformation to a new coordinate system in which the motion of the pole is synchronous with the precession of the lunar orbit can be found in this approach. Estimates of the precision of predictions of the coordinates of the Earth’s pole taking into account additional terms due to lunar perturbations are presented.
相似文献3.
L. D. Akulenko Yu. G. Markov V. V. Perepelkin L. V. Rykhlova A. S. Filippova 《Astronomy Reports》2013,57(5):391-399
A mathematical model for rotational-oscillatory motions of the Earth is constructed by applying celestial mechanics to the spatial problem of the Earth-Moon system subject to the Sun’s gravitation. Some basic phenomena associated with tidal irregularity in the Earth’s axial rotation and the polar oscillations are studied. It is shown that the perturbing component of the gravitational-tidal forces orthogonal to the plane of the lunar orbit is responsible for some short-term perturbations in the Moon’s motion. The constructed model for the rotational-oscillatory motions of the deformable Earth includes both the main high-amplitude perturbations and more complex small-scale motions attributed to short-term lunar perturbations with combinational frequencies. Numerical modeling (interpolation and forecasting) of the Earth rotation parameters within various time intervals based on astrometric data obtained by the International Earth Rotation Service is presented. 相似文献
4.
Yu. G. Markov V. V. Perepelkin L. V. Rykhlova A. S. Filippova Nguen Le Zung 《Astronomy Reports》2014,58(3):194-203
An amplitude-frequency analysis of a few-parameter model for intraday oscillations of the Earth’s pole induced by gravitational-tidal torques exerted by the Sun and the Moon is presented. The characteristic features of the intraday oscillations in the polar coordinates are found using the dynamical Euler-Liouville equations, taking into account irregular perturbations. The modeling results for the polar motion are compared with high-accuracy VLBI observations over short time intervals. An amplitude-frequency analysis of the polar oscillations and the second zonal harmonic c 20 of the geopotential is presented. 相似文献
5.
A differential correlation model for oscillations of the Earth’s pole is constructed. The model has gravitational-tidal, additive and parametric, slowly varying, harmonic (at the Chandler frequency and double this frequency), and random Gaussian, broadband perturbations. Special attention is paid to the analysis of trends and the amplitude-frequency characteristics of stochastic oscillations of the Earth’s pole. Numerical simulations show that first-approximation equations can be used to estimate the correlation characteristics of oscillations of the Earth’s pole to within 10%. The results of the model are compared with the results of statistical modeling of oscillations at the Chandler frequency. The model represents a base of informational resources for analytical modeling of the motion of the Earth’s pole over intervals of three to five years. 相似文献
6.
Refined analytical expressions for the frequencies corresponding to the Chandler motion of the pole and the diurnal rotation of the deformable Earth are derived. Numerical estimates of the period and amplitude of the polar oscillations are presented. The trajectory of the Chandler polar motion derived via numerical modeling is in qualitative and quantitative agreement with experimental data from the International Earth Rotation Service (IERS). An evolutionary model describing slow variations in the Earth’s rotation parameters under the action of the dissipative moments of the tidal gravitational forces on time scales considerably longer than the precession period of the Earth’s axis is constructed. The axis of the Earth’s figure tends to approach the angular momentum vector of the proper rotation. 相似文献
7.
The main force and parametric actions on oscillations in the Earth-Moon system are compared. Parametric excitations due to external periodic changes in the distance between the Earth’s and Moon’s centers of mass occur in a limited number of frequency intervals. We demonstrate the role of a nonlinear parameter that limits the oscillation amplitudes, and compute the frequency interval for excitations near the Chandler frequency. 相似文献
8.
A combined stochastic correlation model for the pole’s motion of a deformable Earth is constructed using the data of the International Earth Rotation Service and dynamical Euler equations taking into account tidal deformations. The deterministic component of the model describes the main regular dynamical effects, while its stochastic component describes irregular effects obeying statistical laws. Linear differential (requiring solutions of ordinary differential equations), and finite (assuming integrated characteristics) correlation models are constructed for both Gaussian and non-Gaussian random parameters. The stochastic oscillations and trend of the Earth’s proper angular velocity are analyzed, as well as nonlinear stochastic oscillations and the trend of the pole. This approach can be considered quite novel. 相似文献
9.
Forecasting the polar motions of the deformable Earth 总被引：1，自引：0，他引：1
A mathematical model for the complicated phenomenon of the polar oscillations of the deformable Earth that adequately describes the astrometric data of the International Earth Rotation Service is constructed using celestial mechanics and asymptotic techniques. This model enables us to describe the observed phenomena (free nutation, annual oscillations, and trends) simply and with statistical reliability. The model contains a small number of parameters determined via a least-squares solution using well-known basis functions. Interpolations of the polar trajectory for intervals of 6 and 12 yrs and forecasts for 1–3 yrs are obtained using the theoretical curve. The calculated coordinates demonstrate a higher accuracy than those known earlier. 相似文献
10.
Astronomy Reports - We found an oscillatory process of the Earth’s pole associated with the precession motion of the Moon’s orbit using numerical processing a series C01 of... 相似文献
11.
When the coupled Earth-Moon system is considered rather than a closed terrestrial system (the Earth's atmosphere, ocean, inner and outer cores, and mantle), an eigenfrequency of free oscillations of the Earth is transformed into an eigenfrequency of the Earth-Moon system, making it possible to understand the increase in the Chandler period in a natural way. The eigenmodes of the coupled Earth-Moon system are determined by solving a linear, homogeneous set of equations with two degrees of freedom. 相似文献
12.
研究Winkler地基上材料非线性矩形薄板的参数共振-主共振问题。建立Winkler地基上材料非线性矩形薄板的动力学方程。利用Galerkin方法将其转化为非线性振动方程。应用非线性振动的多尺度法求得系统满足主参数共振-主共振条件的近似解,并进行数值计算。分析激励、调谐值、阻尼系数、非线性参数、几何参数对共振响应曲线的影响。 相似文献
13.
Effects of instability of the Earth and celestial coordinate systems on Earth orientation parameters
Unknown secular and long-term changes in the Earth orientation parameters attributed to instability (possible rotation) of both the Earth and celestial coordinate systems (ECS and CCS) are studied. Rotation of the CCS due to changes in the coordinates of extragalactic sources resulting from gravitational lensing can lead to errors of the order of several microarcseconds in the orientation parameters. The rotation of the ECS due to the crust pressing on the mantle diminishes the tidal retardation of the Earth's rotation and produces long-term variations in the duration of the day (with a period of about 1500 years) and in the motion of the pole relative to the Earth's surface. 相似文献
14.
V. M. Fedorov 《Moscow University Geology Bulletin》2007,62(4):234-243
An attempt has been undertaken to examine time series of volcanic and seismic events in a multidimensional reference system related to the parameters of the Earth’s orbital motion. Volcanic eruptions and strong (M > 5) earthquakes (a sample from the USGS/NEIC seismological database: Significant Worldwide Earthquakes) [18] were analyzed within the fields of the JPL Planetary and Lunar Ephemerides, (DE-406) astronomical indicators [19]: the Earth-Moon distance, Earth-Sun distance, ecliptic latitude of the Moon, and the differences between the geocentric longitudes of the Moon and Sun, Venus and Sun, and Mars and Sun. Distribution spectra were obtained and normalization was performed taking the nonuniform motion of celestial bodies into consideration, and the values of multidimensional diurnal probability were calculated. As a result, the statistically reliable drift in the distribution of geoevents was calculated relative to the duration of the intervals of multidimensional diurnal probability, which indicates distribution regions where more geoevents can take place during shorter intervals (and vice versa). Linear relationships between the multidimensional diurnal probability and diurnal probability of geoevents were found. All these results and the astronomic ephemerides were used as a base for computing the probabilities of volcanic and seismic activity of the Earth for the period of 2005–2007. The spatial structure of volcanic and seismic processes was examined, which allowed the revelation of probabilistic parameters of the spatiotemporal structure of Earth’s geodynamic activity and outlining an approximate algorithm for its monitoring. 相似文献
15.
Chandler oscillations of the Earth’s pole in the presence of fluctuational dissipative perturbations
Effects of fluctuational dissipative perturbations on the Earth’s polar motion due to random components of the centrifugal potential are studied using a numerical-analytical approach. A combined model for the polar fluctuations is used to take into account stochastic components of the polar tides. Fluctuations excited at frequencies close to the Chandler frequency are analyzed using observations of sea level and the gravitional acceleration. Equations describing the correlation characteristics of the polar motions are presented. 相似文献
16.
The fundamental astrometrical problem of high-accuracy interpolation of the trajectory of the Earth’s pole and construction of an adequate theoretical model for associated complex multifrequency oscillations are considered. Measurements of the Earth-rotation parameters demonstrate the possibility of adjusting the filtering algorithm to make it suitable for practical navigational applications associated with a need for reliable high-accuracy predictions over the required time scales (short-and medium-terms). Numerical simulations and tests of the procedure used to optimize the adjustment parameters are presented. 相似文献
17.
L. D. Akulenko Yu. G. Markov V. V. Perepelkin L. V. Rykhlova 《Astronomy Reports》2009,53(11):1070-1077
The fundamental astrometric problem of high-accuracy interpolation and forecasting of the Earth’s polar motion on short time
scales from 1–2 to 10–30 days is studied. Hierarchies of interval length and parameter accuracy are established using appropriate
models for the process. Filtering algorithms are adjusted using a weighted least squares fit of measurements of the International
Earth Rotation Service (IERS). Best-fit estimates for the main features of the motion are obtained for various time intervals;
interpolations and forecasts are compared with the IERS measurements. 相似文献
18.
《Gondwana Research》2014,25(1):159-169
The Ediacaran–Early Ordovician interval is of great interest to paleogeographer's due to the vast evolutionary changes that occurred during this interval as well as other global changes in the marine, atmospheric and terrestrial systems. It is; however, precisely this time period where there are often wildly contradictory paleomagnetic results from similar-age rocks. These contradictions are often explained with a variety of innovative (and non-uniformitarian) scenarios such as intertial interchange true polar wander, true polar wander and/or non-dipolar magnetic fields. While these novel explanations may be the cause of the seemingly contradictory data, it is important to examine the paleomagnetic database for other potential issues.This review takes a careful and critical look at the paleomagnetic database from Baltica. Based on some new data and a re-evaluation of older data, the relationships between Baltica and Laurentia are examined for ~ 600–500 Ma interval. The new data from the Hedmark Group (Norway) confirms suspicions about possible remagnetization of the Fen Complex pole. For other Baltica results, data from sedimentary units were evaluated for the effects of inclination shallowing. In this review, a small correction was applied to sedimentary paleomagnetic data from Baltica. The filtered dataset does not demand extreme rates of latitudinal drift or apparent polar wander, but it does require complex gyrations of Baltica over the pole. In particular, average rates of APW range from 1.5° to 2.0°/Myr. This range of APW rates is consistent with ‘normal’ plate motion although the total path length (and its oscillatory nature) may indicate a component of true polar wander. In the TPW scenario, the motion of Baltica results in a back and forth path over the south pole between 600 and 550 Ma and again between 550 and 500 Ma. The rapid motion of Baltica over the pole is consistent with the extant database, but other explanations are possible given the relative paucity of high-quality paleomagnetic data during the Ediacaran–Cambrian interval from Baltica and other continental blocks.A sequence of three paleogeographic maps for Laurentia and Baltica is presented. Given the caveats involved in these reconstructions (polarity ambiguity, longitudinal uncertainty and errors), the data are consistent with geological models that posit the opening of the Iapetus Ocean around 600 Ma and subsequent evolution of the Baltica–Laurentia margin in the Late Ediacaran to Early Ordovician, but the complexity of the motion implied by the APWP remains enigmatic. 相似文献
19.
Lin-Sen Li 《Astronomy Reports》2017,61(8):702-708
The differential equation and its solution for indirect influence of the planetary perturbation on the variation of the rotational angular velocity of the rigid Earth in the lunar-solar gravitational field are obtained by using Euler’s dynamic equations. The theoretical results show that the angular velocity of the Earth varies with the periodic and mixed periodic variation under the lunar and solar gravitational field due to the planetary perturbation on the Earth orbit. The numerical results for the amplitudes of the periodic terms and the coefficient of the mixed periodic terms are presented. 相似文献
20.
A theoretical and quantitative analysis of the earth's polar motion, the Chandler wobble and the polar wandering was made under a triaxial, quasi-rigid and rotationally imbalanced earth model and the assumption that the polar excitation was due to the episodic energy perturbation in the earth's upper layers. The Chandler wobble was found to have two frequency components and was quasi-permanent; whereas the polar wandering linked dynamically with the secular tectonic movements in the earth's upper layers. The attempt of the earth to damp its products of inertia for rotation stability maintained the polar motion, while the polar wandering would produce a system of Coriolis torques that provided driving mechanisms to the continental drift, sea-floor spreading and related phenomena, as well as inducing viscous flows in the interior. The secondary deformation due to the earth's non-rigidity was not analyzed in the paper, but the probable connections between the dynamics of polar wandering and the thermal convection in the interior were briefly discussed. The analysis presents the attempt for an integral interpretation of the earth's dynamic evolution or an interpretation of the polar motion, plate tectonics, and the earth's generation and dissipation of excess energy under a unified dynamic theory. 相似文献