Periodical characteristics of the geomagnetic secular variation and length-of-day variation

Based on the historical geomagnetic model GUFM1 and the 10th International Geomagnetic Reference Field models (IGRF10) and the length-of-day data series, the secular variation of some parameters, including geomagnetic moment and its energy and westward drift etc, are analyzed with the wavelet transform method, in addition to the periodical components and time-varying characteristics of decadal length-of-day variation. As the results suggest that, during the period of 1800 similar to 2005, the 82-year and 48-year quasi-periodic components are available for the secular variation of dipole magnetic field, which are not directly related to the periodicity of the length-of-day variation. And both the 66-year and 32-year quasi-periodic components can be found for the secular variation of non-dipole magnetic field parameters and length-of-day variation, and the 66-year quasi-periodicity is stronger than the 32-year one. As far as the 66-year quasi-periodic component is concerned, the western drift exceeds the length-of-day 8.8 years; and the non-dipole magnetic field energy lags behind the length-of-day 15.6 years. We consider that the causality between the origins of the decadal length-of-day fluctuation and the geomagnetic secular variation can not be found.