Paleointensity variations of Earth's magnetic field and their relationshipwith polarity reversals

Power-spectral analyses of the intensity of Earth's magnetic field inferred from ocean sediment cores and archeomagnetic data from time scales of 100 yr to 10 Myr have been carried out. The power spectrum is proportional to 1 /f where f is the frequency. These analyses compliment previous work which has established a 1/f(2) spectrum for variations at time scales less than 1 00 yr. We test the hypothesis that reversals are the result of variations i n field intensity with a 1/f spectrum which occasionally are large enough t o cross the zero intensity value. Synthetic binormal time series with a 1/f power spectrum representing variations in Earth's dipole moment are constr ucted. Synthetic reversals from these time series exhibit statistics in goo d agreement with the reversal record, suggesting that polarity reversals ma y be the end result of autocyclic intensity variations with a 1/f power spe ctrum. (C) 1999 Elsevier Science B.V. All rights reserved.