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1.
Arantxa Luzón Angel González Arsenio Muñoz Belén Sánchez-Valverde 《Journal of Paleolimnology》2002,28(4):441-456
The lacustrine facies from two sections (Candasnos and Fraga) ofthe Oligocene-Miocene Torrente de Cinca lithostratigraphic Unit in thecentral part of the Ebro Basin (Spain) have been analysed to determine theinfluence of orbital parameters in lacustrine sedimentation. The unit ispredominantly composed of limestones and marls, and represents a shallowlacustrine freshwater system. The sedimentological features of the faciesstudied demonstrate that the lower part of the Candasnos section representsoffshore lacustrine subenvironments whereas the upper part, and the whole ofthe Fraga section, characterise marginal lacustrine areas. Series of stratalthickness variations of limestone, marl, and limestone/marl couplets fromboth sections have been analysed using spectral analysis. This shows thatinformation corresponding to periodic cycles only appears in the offshorefacies, that is to say, in the lower part of Candasnos section, and disappearsin the marginal facies where non-periodic cycles exist. Furthermore, thespectral analysis of the offshore facies highlights the existence of a peak inthe power spectrum with a period of around 7 (6.8 to 7.8) that can berecognised in the field as shallowing-upward lacustrine sequences.Magnetostratigraphic data from the Candasnos section allow us to establish atime span of 2,808 years for the limestone/marl couplet from the lower partof this section, and between 19,000 and 22,000 years for the periodic cycleidentified, thus representing the climatic precession cycle. Shallowingsequences from marginal areas do not correspond with any periodiccycle. 相似文献
2.
分析了１９７９年８月至１９９６年１月之间由ＭａｒｋⅢＶＬＢＩ时延资料得到的ＩＡＵ１９８０章动模型在经度（δψ）和交角（δε）方向的偏移序列,得到了对ＩＡＵ１９８０章动模型中主项系数的改正,并检测了自由地核章动。计算步骤依照常规资料处理方法设计,并采用了一些分析技巧以便充分利用资料的整个时段和减小端部效应对参数解的影响。对拟合残差序列的进一步分析表明,自由地核章动是统计显著的,但其参数尤其是其振幅可能具有时变性质,表现为在经度和交角方向自１９８６至１９９５年的持续减弱。 相似文献
3.
We perform a complete reconstruction of the series of the nutation for a rigid Earth model with the use of the very accurate
theories ELP2000 and VSOP82 for the motion of the Moon and the planets respectively, in such a way that all the individual
contributions up to 0.005 mas should be taken. This implies the introduction of the planetary effects, of the influence of
second-order parts of the potential of the Earth (J3, triaxiality), and some improvements due to an extension of the theory
at the second order. All this increase notably the number of coefficients to be taken in account, and modifies also in a significant
way the value of some of them. 相似文献
4.
O. Goepfert 《地球物理与天体物理流体动力学》2019,113(1-2):222-234
ABSTRACTIt is shown that flows in precessing cubes develop at certain parameters large axisymmetric components in the velocity field which are large enough to either generate magnetic fields by themselves, or to contribute to the dynamo effect if inertial modes are already excited and acting as a dynamo. This effect disappears at small Ekman numbers. The critical magnetic Reynolds number also increases at low Ekman numbers because of turbulence and small-scale structures. 相似文献
5.
河外射电源光学对应体的“自行”和岁差常数 总被引：1，自引：0，他引：1
本文用有较长观测间隔的射电源光学对应体的光学观测结果，再次讨论了岁差常数值。由于现用岁差值的不精确，需把这些射电源光学对应体在不同历元的观测结果统一归化到共同参考系统Ｊ２０００．０，并对它们各自的参考星表都归化到ＦＫ５系统，即可得到这些源在ＦＫ５系统中的所谓“自行”．由所得“自行”对岁差常数的改正作了估计。本文还分别对４４颗源和２５颗源作了估算，其相应的岁差改正为－２．６７±１．３３ｍａｓ／年和－３．３１±１．６２ｍａｓ／年，将这些值和由新技术观测所得结果作了比较，两者之间符合得相当好。 相似文献
6.
In this article an approximate analytical integration is performed of the Hamiltonian corresponding to the rotational motion
of an Earth whose elastic mantle is deformed by rotation and lunisolar attraction, using Deprit's perturbation method for
the first order. Besides the usual terms, this Hamiltonian includes the perturbation of the kinetic energy and the elastic
energy produced with the deformation, as well as their causes, the tidal and the centrifugal potential; these new terms have
already been studied for the tidal deformation in previous articles (Getino and Ferrándiz, 1990a, 1990b). The effects of the
deformation due to the centrifugal potential are studied in this article, following the same method as that used for the tidal
deformation. Numerical tables of the periodic perturbations corresponding to the nutation in obliquity and longitude are obtained.
As for the secular effects, a theoretical value of 457 days is obtained for Chandler's period. 相似文献
7.
VLBI-based offsets of the Celestial Pole positions, as well as the variations of UT (series of Goddard Space Flight Center, 1984–2005) are processed applying the Earth’s rotation theory (ERA) 2005 constructed by the numerical integration of the differential equations of rotation of the deformable Earth. The equations were published earlier (Krasinsky 2006) as the first part of the work. The resulting weighted root mean square (WRMS) errors of the residuals , for the angles of nutation and precession are 0.136 and 0.129 mas, respectively. They are significantly less than the corresponding values 0.172 and 0.165 mas for the IAU 2000 model adopted as the international standard. In ERA 2005, the angles , are related to the inertial ecliptical frame J2000, the angle including the precessional secular motion. As the published observational data are theory-dependent being related to IAU 2000, a procedure to confront the numerical theory to the observed Celestial Pole offsets and UT variations is developed. Processing the VLBI data has shown that beside the well known 435-day FCN mode of the free core nutation, there exits a second mode, FICN, caused by the inner part of the fluid core, with the period of 420 day close to that of the FCN mode. Beatings between the two modes are responsible for the apparent damping and excitation of the free oscillations, and are implicitly modeled by ERA 2005. The nutational and precessional motions in ERA 2005 are proved to be mutually consistent but only in case the relativistic correction for the geodetic precession is applied. Otherwise, the overall WRMS error of the residuals would increase by 35%. Thus, the effect of the geodetic precession in the Earth rotation is confirmed experimentally. The other finding is the reliable estimation δc = 3.844 ± 0.028° of the phase lag δc of the tides in the fluid core. When processing the UT variations, a simple model of the elastic interaction between the mantle and fluid core at their common boundary made it possible to satisfactory describe the largest observed oscillations of UT with the period of 18.6 year, reducing the WRMS error of the UT residuals to the value 0.18 ms (after removing the secular, annual and semi-annual terms). 相似文献
8.
Sandrine D’Hoedt Anne Lemaitre Nicolas Rambaux 《Celestial Mechanics and Dynamical Astronomy》2006,96(3-4):253-258
Mercury is observed in a stable Cassini’s state, close to a 3:2 spin-orbit resonance, and a 1:1 node resonance. This present situation is not the only possible mathematical stable state, as it is shown here through a simple model limited to the second-order in harmonics and where Mercury is considered as a rigid body. In this framework, using a Hamiltonian formalism, four different sets of resonant angles are computed from the differential Hamiltonian equations, and each of them corresponds to four values of the obliquity; thanks to the calculation of the corresponding eigenvalues, their linear stability is analyzed. In this simplified model, two equilibria (one of which corresponding to the present state of Mercury) are stable, one is unstable, and the fourth one is degenerate. This degenerate status disappears with the introduction of the orbit (node and pericenter) precessions. The influence of these precession rates on the proper frequencies of the rotation is also analyzed and quantified, for different planetary models. 相似文献
9.
David J. Mallinson Benjamin Flower Albert Hine Gregg Brooks Roberto Molina Garza 《Global and Planetary Change》2003,39(3-4):257-269
Sediments from ODP Site 1128 in the Great Australian Bight record isotopic and mineralogic variations corresponding to orbital parameters and regional climate change during the early Oligocene climate transition and Oi1 glacial event. Bulk carbonate stable isotope analyses reveal prominent positive oxygen and carbon isotope shifts related to the inferred major increase in glaciation at approximately 33.6 to 33.48 Ma. The oxygen isotope excursion corresponds to a prolonged period of low eccentricity, suggesting ice-sheet growth during low seasonality conditions. The clay mineralogy is dominated by smectite throughout. The exclusive occurrence of highly crystalline smectite from 33.6 to 33.5 Ma suggests the occurrence of explosive volcanism that correlates with the positive oxygen isotope shift. The dominance of mixed-layer smectite from 33.5 to 33.4 Ma and an increase in illite following 33.4 Ma indicates a transition from cool, wet conditions to cool, dry conditions over Australia during the Oi1 glaciation. Clay mineralogy and carbonate percentages reveal precession-scale oscillations during the Oi1 event. Kaolinite varies inversely with smectite and percent carbonate. Variations in precipitation and runoff, and wind velocities during southern hemisphere summer perihelion and high eccentricity intervals may account for the precession-scale oscillations. 相似文献
10.
通过对Melchior P.潮汐与章动理论的改进，给出了高阶日月引潮力位引起的岁差章动力矩，建立了刚体地球极移和章动的联合动力学方程，由此对天球中间极（CIP）进行了严格的理论定义. 在各阶潮汐力矩的作用下，得到CIP轴岁差章动的表达式. 通过推导发现，奇数阶引潮力位产生的岁差章动力矩使得黄经章动和交角章动出现了异向项（即：黄经章动出现了cos项，交角章动出现了sin项）. 最后利用郗钦文精密引潮力位展开，建立了737项刚体地球章动序列. 新的章动序列是IERS2003采用的刚体地球章动序列REN2000（包含678个日月章动项）的一个补充. 相似文献