Multi-decadal to centennial secular variation of the main geomagnetic field
主磁场长期变化十年至百年尺度的周期

In this paper, the technique of wavelet transform is applied to analyze the gufm1 models during 1590~1990 A.D., for detecting the periodicities in the secular variations of the main geomagnetic field. Our analysis suggests that there are three principal periodic components in the total Pole-strength of B field: a stable 30-year periodic component which is mainly seen in the equatorial component g11 of the dipole field, and it is also generally seen in the non-dipole field; second, a dispersive quasi 50-year periodic component, typically contributed by the axial component of the dipole field g01, and the quadrupole also has a definite contribution; the last one is an intensity varying 110-year periodic component on centennial time scale, which seems to be from the equatorial component of the dipole field, and the octupole field also has a contribution.