Multi-decadal to centennial secular variation of the main geomagnetic field

In this paper, the technique of wavelet transform is applied to analyze the gufml models during 1590 similar to 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) over dot field: a stable 30-year periodic component which is mainly seen in the equatorial component (g) over dot broken vertical bar 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 (g) over dot(1)(0), 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.