Study Of The Excitation Of The Chandler Wobble By Stochastic Motions

The dynamical theory of the Earth rotation and the progress on excitation of the Chandler wobble are introduced. For the Chandler wobble, a lot of researches have been done, especially for its excitation, many kinds of effects have been taken into account such as the atmosphere, ocean, continental water, even seismic, core-mantle coupling and so on.. But its exciting mechanism is still an open problem. Considering that the Chandler Wobble is a result of the excitation of stochastic motions, we analyse its dynamics by means of statistical methods. First, the trend, annual and semi-annual terms are removed by the least-square fitter from the SPACE98 time series which describes the polar motion of the Earth, the main component in the resulted new series is the Chandler Wobble. Then, for the new series, the corresponding stationary, periodic and random examinations are made for the new series. The results show that the Chandler Wobble may be regarded as a stationary stochastic process. The same thing is carried out for the NECP atmosphere and ocean angular momenta. The results also show that the two angular momenta have the same statistical characteristic as the Chandler Wobble. It can be concluded that the stochastic component in atmosphere and ocean may excite the Chandler Wobble, and the exciting quantity is about 72-76%. The theoretical analysis and numerical simulation for the Chandler wobble is the other work of this paper. The theoretical analysis shows that periodic forcing only excites the polar motion with the corresponding period, and stochastic motion is one exciting source with the best probability for the Chandler Wobble. Assuming that stochastic motion excites the Chandler Wobble, we construct a numerical simulation model for the dynamics of the Chandler Wobble. Based on the stochasticaLly exciting model, we simulate the dynamical process of the Chandler Wobble by using white noise as the exciting source. It shows clearly the two main characters of the Chandler Wobble amplitude: irregular and non-monotonous variation. On the other hand, using the NCEP atmosphere and ocean angular momenta (removed the components of regular variation) as the exciting source, we can simulate the Chandler Wobble. The result indicates that the simulated Chandler wobble seems to be the same as the observational one in the aspect of the above two main characteristics. But their specific magnitude and shape are very different due to the difficulty to determine one correct initial value in simulation and the length limitation of the NCEP atmosphere and ocean angular momenta. Finally, we point out some questions which need to study further in the future, such as the relation between various stochastic process and the Chandler wobble, how to separate the stochastic motions from the atmosphere and ocean, the relationship between the separated stochastic motion and observation error and so on. Whatever, the work of this paper is a new test for the investigation of the Chandler Wobbledynamics.