Evolution of the Virtual Dipole Moment in Earth’s Geological History

Resumo

Data of the International Bank of Digital Information on the time distribution of the virtual dipole moment (VDM), supplemented by data of more recent studies (a total of 5645 values), were used as the basis for analyzing the distribution of VDM values for Earth’s history using the concept of the Earth’s magnetic dipole field. The VDM behavior is characterized by a positive linear trend from 4.2 × 10 ²² Am² (4.2 GA ago) to 5.15 × 10²² Am² today. Against a linear increase in the field, VDM undulations nonuniformly distributed over time have been recorded, varying in magnitude from 1.7 to 3.7 × 10²² Am² wavelength from 220 to 920 Ma. The average wavelength of such undulations is estimated at 570 Ma, which in order of magnitude approaches the period of the Wilson cycle. It has been revealed for the first time that the magnitudes of magnetic field undulations over time are oscillatory in nature and increase toward present day.