The correlation of long-term trends in the palaeointensity and reversal frequency variations

Abstract

The correlation of long-term trends in the geomagnetic field's strength and polarity stability is re-examined using all the available palaeointensity data. The Phanerozoic VDMs (virtual dipole moments) decrease systematically with age, whereas the Precambrian estimates are comparable to the present field. This is ascribed here to a steady low-temperature oxidation of titanomagnetites which reduces the NRM intensities in the initial stages. The observational record is also taken to favour Braginskii's (1976) model-Z geodynamo, over Busse's (1975) weak-field model, suggesting that a high reversal frequency implies a stronger toroidal field in the core than when reversals are infrequent. -from Author