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1.
同时采用4个台站的国际超导重力仪长期连续重力观测资料和国际地球自转服务中心提供的同步地球自转参数,研究了极移引起的地球重力场变化特征。利用自回归模型估计了各序列的功率谱密度和积谱密度,结果表明极移导致的重力效应的主要能量集中在Chandler摆动和周年项附近,叠积后实际重力观测与极移重力信号理论值之间的差异分别为0.4%和3.9%,说明超导重力仪可有效监测极移导致的重力变化。 相似文献
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基于简正模扰动理论和勒夫数扰动方法,采用Zschau 的地幔流变模型,在假设Chandler摆动的能量全部耗散于地幔滞弹性摩擦的条件下,导出Chandler 摆动Q(Q_w)的理论值.还考虑了滞弹地球的平衡极潮对摆动的影响,所得结果与绝大部分天文实测值非常一致.分析表明.平衡部分的影响大,地幔滞弹性很可能是Chandler 摆动最主要的能量耗散源,Q_w 的理论值约为71.还推算了吸收带模型参数α,研究了该模型的适用性,并讨论了Q_w 与地幔Q(Q_m)的关系. 相似文献
4.
Two long time series were analysed: the C01 series of the International Earth Rotation Service and the pole series obtained
by re-analysis of the classical astronomical observations using the HIPPARCOS reference frame. The linear drift of the pole
was determined to be 3.31 ± 0.05 milliarcseconds/year towards 76.1 ± 0.80° west longitude. For the least-squares fit the a priori correlations between simultaneous pole coordinates x
p
, y
p
were taken into account, and the weighting function was calculated by estimating empirical variance components. The decadal
variations of the pole path were investigated by Fourier and wavelet analysis. Using sliding windows, the periods and amplitudes
of the Chandler wobble and annual wobble were determined. Typical periods in the variable Chandler wobble and annual wobble
parameters were obtained from wavelet analyses.
Received: 21 January 2000 / Accepted: 28 August 2000 相似文献
5.
The coupled rotation of the inner core 总被引:1,自引:0,他引:1
The rotation of the inner core (IC) is influenced by the rest of the Earth through a number of coupling mechanisms. Among four possible coupling mechanisms, gravitational, pressure, viscous and electromagnetic, the first two torques are dominant. Numerous existing IC gravitational torque estimates have been shown to agree very well with one another Xu & Szeto 1996 ). It is shown in this paper that different estimates of the IC pressure torque are also in good agreement.
The coupled rotation of the IC has been investigated in the frequency domain by several research groups (Mathews et al. 1991a,b; De Vries & Wahr 1991 ; Dehant et al. 1993; Jiang 1993 ). Not all of these efforts obtained two IC-related rotational modes, the inner-core wobble (ICW) and the free-inner-core nutation (FICN). We investigate this problem in the time domain and confirm the existence of the two modes. The periods of ICW and FICN are in good agreement with those obtained by other researchers. In studying the effects of coupling torques on the IC rotational modes we have found that depending on whether the IC net torque is 'restoring' or otherwise, an increased torque magnitude will respectively shorten or lengthen the ICW period. We have also found that the sense of FICN is determined by the orientation of the net coupling torque on the IC. 相似文献
The coupled rotation of the IC has been investigated in the frequency domain by several research groups (Mathews et al. 1991a,b; De Vries & Wahr 1991 ; Dehant et al. 1993; Jiang 1993 ). Not all of these efforts obtained two IC-related rotational modes, the inner-core wobble (ICW) and the free-inner-core nutation (FICN). We investigate this problem in the time domain and confirm the existence of the two modes. The periods of ICW and FICN are in good agreement with those obtained by other researchers. In studying the effects of coupling torques on the IC rotational modes we have found that depending on whether the IC net torque is 'restoring' or otherwise, an increased torque magnitude will respectively shorten or lengthen the ICW period. We have also found that the sense of FICN is determined by the orientation of the net coupling torque on the IC. 相似文献
6.
极移中Chandler摆动出现的双频现象,一直以来为许多学者所关注。推导了基于Chandler摆动双频的极移确定项模型,并采用该模型对极移确定项进行了拟合。与仅采用单频进行确定项拟合的对比表明,利用双频能取得更理想的结果。 相似文献
7.
用1985~1995年期间海洋角动量变化序列和大气角动量变化序列,分析它们对Chandler摆动的激发能量以及它们与天文观测激发的相干性. 结果表明,在Chandler摆动频带内,海洋角动量变化提供的激发能量大约占观测激发的64髎,其中洋底压力变化起主导作用;NCEP/NCAR(美国国家环境预测中心/国家大气研究中心)和JMA(日本气象厅)大气角动量变化提供的激发能量分别为观测激发的23髎和214髎. 海洋激发与观测激发的相干系数约为0.52,接近99髎置信度下限(0.54),海洋激发的相位滞后观测激发约19°;NCEP/NCAR和JMA的大气激发与观测激发的相干系数分别为0.32和0.37,大气激发的相位超前观测激发分别约47°和19°. 用更短期间(9年、6年)的海洋和大气角动量序列与更长期间(16、39年)的大气角动量序列作分析表明,在Chandler摆动频带内,无论是它们的激发能量,还是它们与观测激发之间的相干系数都呈现很大的变化,而且这些变化具有某种程度的随机性. 相似文献
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10.
Earth’s free wobble is often referred to as the Euler wobble (for the rigid case) or the Chandler wobble for the real case.
In this study, we investigate the theory of the free wobble of the triaxial Earth and demonstrate that: (1) the Euler period
should actually be expressed by the complete elliptic integral of first kind, and (2) the trace of the free polar motion is
elliptic, with the orientations of its semi-minor and major axes being approximately parallel to the Earth’s principal axes
A and B, respectively. Numerical calculations show that, due to the triaxiality of the Earth, the spin rate ω
3 fluctuates with the semi-Euler/Chandler period, although its amplitude (about 10−19 rad/s) is rather small and beyond the present measurement accuracy; the tilt of the instantaneous spin axis (or the amplitude
of the free wobble), θ, has a fluctuation whose amplitude is around 0.34 milli-arcsecond (mas), which could be detected by present observations.
Thus, we conclude that the Earth’s triaxial nature has little impact on ω
3, but has an influence on the polar motion which should not be ignored. On the other hand, our study shows that there is a
mechanism of frequency–amplitude modulation in the Chandler wobble which might be a candidate to explain the correlation between
the amplitude and period of the Chandler wobble. We compare the theoretical polar parameters (m
1, m
2) with the observed values for the Chandler components obtained from the data EOP (IERS) C 04, and find that they coincide
with each other quite well, especially for recent years. In addition, a polar wander towards 76.7°W, which is in agreement
with previous results given by other scientists, is also obtained. 相似文献