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介绍了地球自动力学中的两个目前正在研究的问题，1．Chandler摆动的随机激发，在分析Chandler摆动各种激发的可能性后，认为随机运动是最可能的激发源，在此基础,提出了一个Chandler摆动激发的动力学模型，并从理论和数值模拟两方面对此模型做了统计分析研究，描述了今后对此问题的研究思路，2．地球内部动力学是目前国际地球动力学界的一个热点研究课题，介绍了它的现状和最近的发展动态以及准备在这方面开展研究工作的打算。 相似文献
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用 198 4～ 1999年期间的地极坐标序列和两个大气角动量序列 ,分析了不同Chandler周期和品质因子Q的取值对Chandler摆动观测激发的功率谱密度 ,以及观测激发与大气激发之间的相干系数和相干相位的影响。结果表明 ,不同Chandler周期和品质因子Q的取值对观测激发的功率谱密度 ,以及观测激发与大气激发之间的相干系数有很大影响。因此 ,在分析Chandler摆动的观测激发与地球物理激发的关系时 ,不能仅以观测激发与某个地球物理激发序列 (如大气激发 )的更好逼近来选择Chandler摆动的最佳周期 ,因为Chandler摆动是多种地球物理激发共同作用的结果 相似文献
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应用日本气象厅(JMA)最近发表的以美国大气与环境预测中心(NCEP)修正前、后的reanalysis数据计算出的全球和南、北半球风角动量资料,估计了风对Chandler摆动的平均激发能量,以及风的激发与观测激发之间的相干系数和相干相位．结果表明, 1980-1993(1980-2003)年期间,全球对流层风和(对流层 平流层)风对Chandler摆动的激发能量可分别解释观测激发的68％和72％(58％和51％),对流层风起着主导作用;它们与观测激发的相干系数分别达到0．49和0．32(0．50和0．39),而且具有接近于零的相干相位．这些结果充分说明风在Chandler摆动激发中的重要作用．分析结果也展示了分别应用NCEP修正前,后的reanalysis数据、从实际表面和海平面开始积分的风角动量对Chandler摆动激发的不同影响． 相似文献
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除大气外,海洋对Chandler摆动具有重要的激发作用.利用Estimating the Circulation and Climate of the Ocean(ECCO)的海洋环流模式提供的流速场和洋底压力场资料,首次系统地研究了1980-2005年期间,太平洋、印度洋和大西洋对Chandler摆动激发的贡献.研究表明三大洋对Chandler摆动激发的贡献各不相同.太平洋激发能量约占观测激发能量的22.2%,在三大洋中最高,印度洋约占12.7%,大西洋最低,占7.1%左右.太平洋对Chandler摆动的激发能量可能受1982-1983年强ENSO事件的影响而显著提高. 相似文献
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Chandler摆动的非线性分岔耗散 总被引：3，自引：0，他引：3
在已有的Ｃｈａｎｄｌｅｒ摆动非线性共振激发模型的基础上,引入微小的非线性项,得到不可忽略的非线性分岔解。实际上,Ｃｈａｎｄｌｅｒ摆动方程是可用线性阻尼非线性平面单摆来逼近的,由Ｄｕｆｆｉｎｇ方程可以求得方程的解。 相似文献
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固体地球、海洋(以及大气)构成一个动力学整体,它们各自的运动相互牵制,相互激发。近年来,一个新的课题:海洋-固体地球耦合系统动力学,正逐步受到人们的普遍关注。借助这种耦合系统的动力学理论,有可能解释极潮观测与理论之间的不一致,探讨Chandler摆动的耗散机制,进一步可估计出液核对地幔摆动的耗散量级。 本文总结了耦合系统研究的最新进展,介绍了各种耦合理论的内容,对这一课题中所存在的问题也进行了讨论。 相似文献
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弱磁化相对论电子束注入等离子体时，由非共振波粒相互作用激发的束－等离子体不稳定性可以直接放大电磁波，计算结果表明：在偏离共振条件的区域，电磁波仍可在较宽的频率范围被放大，并在每个共振峰下形成平台结构。随着谐波数的增高，增长率峰值逐渐变小，峰宽也变窄。本文还分析了电磁波的增长率随背景参数ω＿（ｐｅ）／Ω＿ｅ及高能电子的入射方向和辐射方向的变化规律，在典型的日冕条件下，此类不稳定性所放大的电磁波的增长率大小、带宽、方向性、偏振及谐波等性质，可以用来解释太阳Ⅲ型射电爆发现象，本文的研究亦可用来解释其他天体等离子体辐射。 相似文献
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不同频段上极移,日长变化与大气角动量变化激发结果的比较 总被引：1，自引：0，他引：1
本文用ＪＭＡ大气角动量序列计算了对极移和日长变化的激发量（ｍ＇１、ｍ＇２和ｍ＇３），并分三个频段与天文观测得到的地球自转参数序列（ｍ１、ｍ２和ｍ３）进行了比较．结果表明：在钱德勒和季节性频段上，大气运动确实是固体地球自转变化的主要激发源． 相似文献
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Zhang Huan-zhi 《Chinese Astronomy and Astrophysics》1981,5(4):460-468
This paper introduces the idea that there exists a nutation separation layer in the superficial zone of the Earth, thereby sets up a new model of nutation. The equations of motion are derived and solved. It is proved that the separation layer is “soft”, and is probably located at a depth of 300 km from the surface. Its allowable minimum thickness is less than 1 km and its viscosity is on the order of 1010 poise, like pitch at 15 °C. The results show that the main peak of the Chandler wobble (CW) is double, one being the nutational frequency of the inner main body, the other , the outer component. The beat between the two frequencies produces the 40-yr period in the amplitude of the CW. The two amplitudes interact so they do not differ greatly in size, their approximate ratio being 1 to 0.7. The famous amplitude-period relation of the CW is a direct result of this paper. The sudden changes in the polar trace and the 180° phase change in 1924–1926 are essentially the same phenomenon determined by relative changes in the two frequencies. The value of Q for the CW of between 30 and 60 deduced by previous workers from observations is a false Q, the true Q is around 200, in agreement with the value from seismic waves. This paper also predicts that apart from the two main frequencies, there is a series (more than one pair) of secondary frequencies symmetrically located on either side. The time constant of the CW is about 70 yr and it can be approximately maintained by excitation by earthquakes. Its unsmooth motion is one that zigzags about the mean trace. 相似文献
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Jin Ma Yong-Hong Zhou De-Chun Liao Jian-Li Chen Shanghai Astronomical Observatory Chinese Academy of Sciences Shanghai Graduate School of Chinese Academy of Sciences Beijing Center for Space Research University of Texas at Austin Austin TX USA 《中国天文和天体物理学报》2007,7(6):831-838
The global oceans play important roles in exciting the annual polar motion besides the atmosphere. However,it is still unclear about how large the regional oceans contribute to the annual polar motion. We investigate systemically the contributions of the Pacific,Atlantic and Indian Oceans to the excitation of the annual polar motion,based on the output data of ocean current velocity field and ocean bottom pressure field from "Estimating the Circulation and Climate of the Ocean (ECCO)" ocean circulation model over the period 1993-2005. The result shows that due to its particular location and shape,the Atlantic Ocean makes a less significant contribution to the x-component of the annual polar motion excitation than the Pacific and Indian Oceans,while all these three oceans contribute to the y-component of the annual polar motion excitation to some extent. 相似文献
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A. L. Kunitsyn 《Celestial Mechanics and Dynamical Astronomy》1974,9(4):471-481
The instability criterion of a nonlinear mechanical system neutral to the first approximation is formulated for the internal resonance case which is characterized by the existence of commensurabilities between the frequencies of the system.The criterion derived is used for determining the regions of instability of Laplace's constant triangular solutions of the unrestricted three-body problem. It is shown that in the region where necessary Routh-Joukovsky's stability conditions are satisfied there may exist eight resonanceunstable sets of the masses of the three bodies. These sets may be mechanically interpreted as follows: in the case of resonance instability the barycentre of the equilateral triangle formed by the three bodies is located on one of the eight circles constructed in the geometrical centre of this triangle. 相似文献
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Differential equations ruling the Earth’s polar motion are slightly asymmetric with respect to the pole coordinates. This is not only associated with the lack of axial symmetry around the Earth figure axis (triaxiality) but also with the longitude dependency of the pole tide (the main contribution). We propose a consistent handling of both asymmetric contributions, formulating a unique equation in the complex equatorial plane, of which we derive a general solution. Difference with respect to the usual symmetric solution is discussed and found significant in light of the present accuracy of the observed pole coordinates. For the same geophysical excitation, the prograde Chandler wobble is accompanied by a retrograde component up to 2 milliarcseconds (mas), transforming it in a slight elliptic motion. The asymmetric contribution is relatively larger in the geodetic excitation function, for Chandler wobble excitation mixes prograde and retrograde components of comparable level (1 mas). 相似文献
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Yu.V. Golikov V.V. Pustovalov A.B. Romanov V.P. Silin V.T. Tikhonchuk 《Planetary and Space Science》1977,25(10):899-906
A theory of VLF noise excitation by electron beams in the polar magnetosphere is proposed. Two modes of excited oscillations are considered: waves with frequencies in the vicinity of the lower hybrid resonance (LHR) from about 50 to 1000 kHz and whistler-mode waves in the frequency range of several kHz.The spectral distribution and the level of turbulent noise, having been excited by means of two counterstreaming electron beams, are deduced in magnetized plasma at the LHR frequency. It is also shown that the growth of noise up to the quasistationary level oscillates with time. Energy density of oscillations at the LHR frequency in the region of the dayside polar cusp agrees with the experimental data.The processes of whistler excitation by electron beams are discussed. The growth rate of excitation of whistler-mode by electrostatic oscillations at the LHR frequency is calculated. 相似文献
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A theoretical study is made of the whistler mode cyclotron instability both in linear and nonlinear regimes in conjunction with the generation of VLF emissions in the magnetosphere. For the nonlinear treatment, a well-established quasilinear method is used and some physical processes of the cyclotron instability viz. energy conservation, mechanism of instability and frequency change of the excited emissions are clarified. The results are applied to some types of the triggered VLF emissions; whistler triggered emissions and artificially stimulated emissions (ASE). It is found that whistler triggered emissions excited around the upper cutoff frequencies of whistlers may be explained by the whistler mode cyclotron instability by a model distribution function inferred from satellite data. In order to see a nonlinear evolution of the whistler mode cyclotron instability, computer simulations were carried out and it is shown that the change of frequency with time of whistler triggered emissions as well as characteristics of ASE are well explained by resonant nonlinear behaviour of whistler mode cyclotron instability considered in the present paper. 相似文献
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A reasonable and quantitative result on the variation of polar wobble excited by the oceans is not available at present. Numerous researches have shown that atmospheric motion is the greatest excitation source for the seasonal variations in the polar wobble and that oceanic motion is one of the main remaining excitation sources. The excitation of variation in the annual polar wobble caused by oceans from 1992 to 2004 both globally and in latitude dependence, have been studied in depth by means of the new generation of SODA oceanic data assimilation (SODA-1.4.2 and SODA-1.4.3) and the ECCO oceanic data assimilation. The result shows that the variation in the seasonal polar wobble excited by the SODA oceans is very close to that of the residual after the action of the atmosphere and land water is deducted from the geodesic excitation function for a large part of the investigated time interval, and that there is overall agreement between the two as regards the annual amplitude and phase. In addition, in comparison with the result of early SODA-Bata 7, the new generation of SODA oceanic excitation has achieved obvious improvements. The latitude distributions of the excitations of the annual polar wobble by the SODA and ECCO oceans are consistent in the Greenwich direction, while having obvious differences in the direction of 90° E. 相似文献
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Using new data of atmospheric angular momentum for the period 1975–1995, the contributions of the atmosphere to the changes in LCD and polar motion on the seasonal time scale are investigated. The results show that, when the effects of wind and atmospheric pressure are considered, the atmosphere's contribution on the annual and semi-annual time scales may reach, respectively, 95% and 88%. We also give some quantitative results of the atmosphere's excitation of polar motion. On the annual time scale, the contribution to the X-component of polar motion is 16% and that to the Y-component is 43%. On the semi-annual time scale, the contributions to the X- and Y-components are, respectively, 9% and 30%. From the above results, it is clear that the contribution of the ocean should also be included in a more complete solution of the problem of excitation of the earth's rotation. 相似文献
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Pulkovo astrometric observations began in the 1840s using the Repsold transit instrument in the prime vertical and Ertel vertical
circle. The first observers on these instruments were W.I. Struve, 1840–1856, and Kh.I. Peters, 1842–1849. In the present
work, we collected and analyzed different series of latitude variations from observations made by M.O. Nuren, B. Wanach, A.A.
Ivanov, I.N. Bonsdorf, and A.Ya. Orlov. In addition, results are given of investigations of a specific behavior of the Chandler
polar motion in this interval, obtained by C. Chandler, Ivanov, Kh. Kimura, Orlov, and N. Sekiguchi. The aim of this paper
is to search for and analyze the earliest series of Pulkovo latitudes, in order to evaluate the possibility of their use to
study the motion of the pole at the maximum available range of observations. Different methods were used to isolate and analyze
the sum of Chandler and annual latitude variations. The annex provides a series of Pulkovo latitude variations for 1840–1848,
which may be used to extend latitude variation back to 1840. 相似文献