Improved nutation series for the non–rigid earth with a precise adjustment of parameters with nonlinear dependence

In this paper, the previous nutation series corresponding to the rotation of a non‐rigid earth composed of a rigid mantle and a liquid core obtained by Getino and Ferrándiz in 1997 are notably improved by using a high performance data fitting method. This method can be applied to many other problems presenting a non‐linear dependence on the free parameters. This revised version was published online in July 2006 with corrections to the Cover Date.     

地球动力学扁率及其与岁差章动的关系

由岁差常数求得的日月岁差是天文学的重要参数之一,它和地球动力学扁率相联系。地球动力学扁率在章动理论的计算中也是一个重要的物理量。介绍了由不同的观测方法和模型给出的地球动力扁率值,并讨论了它也岁差的关系和对章动计算的影响。在刚体地球章动振幅的计算中,地球动力学扁率值起着尺度因子的作用,要改善刚体地球章动振幅的计算,需要修改目前的黄经总岁差值。非刚体地球章动的转换函数中所采用的简正模和常数都直接或间接地依赖地球动力学扁率值。在IAU1980章动理论中,计算刚体地球章动振幅所使用的地球动力学扁率值计算转换函数中简正模频率和常数所使用的地球动力学扁率值并不一致。随着观测和计算精度的提高,地球动力学扁率值的不一致将影响章动振幅的计算。在建立刚体地球章地动理论中,如何解释地球动力学扁率值的差异,如何选取地球动力学扁率值,还有待进一步的研究。     

超导重力技术在探讨核幔边界黏性特征中的初步应用

旋转椭球型地球的固体地幔与液态地核间相互作用而产生的逆向本征模通常称之为地球自由核章动,自由核章动的品质因子（Q值）能有效反映核幔边界层能量耗散特征,与核幔边界的黏滞度密切相关.本文首次利用全球地球动力学计划网络23个台站27组高密度采样的高精度超导重力仪器观测数据,采用迭积技术,确定了自由核章动参数Q值,进而计算了核幔边界的黏滞系数.数值结果说明获得的核幔边界动力学黏滞系数达到103 Pa·s量级,与加拿大科学家Smylie等利用VLBI观测资料获得的最新结果一致,这说明重力技术是有效应用于研究地球深内部结构的重要手段之一.     

内核的转速和倾角对ICW与FICN的影响:Mathews理论

研究了内核幌动(ICW)和自由内核章动(FICN)。为了给出解析结果,采纳了一个简单地球模型。与以往的研究相比,本文的新结果包括了内核相对地幔的转速和倾角的影响。     

弹性地球极移和章动的理论研究

通过引入章动坐标系,建立了弹性地球自转极移和章动的联合动力学方程,进而改进了对传统地球自转动力学理论的描述。研究表明改进后的方法具有综合性强、易于理解及可同时求解极移和章动的特点。在顾及到5阶岁差章动力矩的情况下,给出了弹性地球CIP轴的定义及其极移、岁差章动的表达式,并发现奇数阶引潮力位产生的外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),这是以往理想弹性地球自转理论中所没有涉及到的。     

Effects on the nutation of C4,m and S4,m Harmonics

In this paper, we make a study about the influence of the coefficients of the geopotential C_4,m and S_4,m, (m=1,2,3,4) on the nutation, starting from the Hamiltonian theory as developed by Kinoshita (1977).We obtain ten coefficients larger than 0.05 μ as for the nutation in longitude and six for the nutation in obliquity. The present results are included in the reconstruction of the theory of nutation (REN‐2000) at the level of truncation of 0.1 μ as (Souchay et al., 1997). This revised version was published online in July 2006 with corrections to the Cover Date.     

An Abridged Model of the Precession–Nutation of the Celestial Pole

Precise astrometric observations show that significant systematic differences of the order of 10 milliarcseconds (mas) exist between the observed position of the celestial pole in the International Celestial Reference Frame (ICRF) and the position determined using the International Astronomical Union (IAU) 1976 Precession (Lieske et al., 1977) and the IAU 1980 Nutation Theory (Seidelmann, 1982). The International Earth Rotation Service routinely publishes these 'celestial pole offsets', and the IERS Conventions (McCarthy, 1996) recommends a procedure to account for these errors. The IAU, at its General Assembly in 2000, adopted a new precession/nutation model (Mathews et al., 2002). This model, designated IAU2000A, which includes nearly 1400 terms, provides the direction of the celestial pole in the ICRF with an accuracy of ±0.1 mas. Users requiring accuracy no better than 1 mas, however, may not require the full model, particularly if computational time or storage are issues. Consequently, the IAU also adopted an abridged procedure designated IAU2000B to model the celestial pole motion with an accuracy that does not result in a difference greater than 1 mas with respect to that of the IAU2000A model. That IAU2000B model, presented here, is shown to have the required accuracy for a period of more than 50 years from 1995 to 2050.     

Influence Of The Atmosphere On Earth Rotation: What New Can Be Learned From The Recent Atmospheric Angular Momentum Estimates?

The interaction between the atmosphere and the underlying solid mantle is oneof the most important sources of changes in all three components of theEarth's rotation vector on different time scales. In this paper the NCEP/NCARreanalysis time series of four times daily atmospheric effective angularmomentum (EAM) estimates is used to investigate some selected aspects of theatmospheric influence on Earth rotation. Emphasis is placed on thecontroversial features which were difficult or impossible to study using theoperational EAM data, such as excitation of the free oscillations in polarmotion, the Chandler wobble (CW) and the free core nutation (FCN), or theroles of diurnal and semidiurnal atmospheric tides and atmospheric normalmodes in the rotational dynamics of the Earth.