Earth’s Magnetic Field Is Decaying Steadily—with a Little Rhythm


D. Russell Humphreys*

A new curve fit to a new compilation of data shows with new clarity that from 1900 to 2010, the main “dipole” part of the earth’s magnetic field decayed exponentially (constant percent loss per year) with a small sine-wave variation. The time constant of the exponential part is 1611 (± 10) years. The sinusoidal part has a period of 66.1 (± 1.3) years and an amplitude of 0.29 (± 0.02) % of the main part today. The fit is very good, with most points within 0.05% of the curve. The distinctness of the exponential part gives new strength to the creationary model of the field, that losses in the earth’s core today are steadily decreasing the electric current producing the dipole field, thus supporting a young earth. A simple electric circuit clarifies the decay model. The small sine-wave part, apparently not noticed in the dipole moment data before now, may be due to an east-west torsional oscillation between core and mantle. This corresponds to an approximately 60-year cycle observed in the rate of earth’s rotation.