Study of the Gravitational Potential Coefficient J2 for Earth and planets of the Solar System from Satellite Data

The following research is focused on the gravitational potential and the figure of the planets of the solar system. Particular attention is paid to the gravitational harmonic J2 coefficient. The study is aimed to investigate the relation between J2 and figures of the planets using Rado-Darwin and Clairaut equations. The second part of the work is dedicated to the analysis of time series of J2 coefficient of the Earth since 1976 till 2016 obtained by Satellite Laser Ranging (SLR). J2 time series was studied using Fourier analysis and singular spectrum analysis. The singular spectrum analysis has been applied for the first time to study of J2. This method allowed to separate six principal components in J2 time series. The plots of these processes and their spectra are presented. A component of the global trend is the most interesting feature. It could be a part of a long-term ~60-year oscillation with a minimum around 2005 yr. Such variations were also observed in the climate indexes, amplitude of Chandler wobble and the length of day [13]. Other components of J2 are quasi-periodic, with periods ranging from six months to 20 years. Some of them are related with the circulation processes in the ocean and the atmosphere, some of the components may be associated with the tidal influence of the moon. The results of this study may be useful for clarifying the issue of interrelation between the astronomical and geophysical processes, including the global climate change triggered by the rising temperature on our planet.