Viscous demagnetization and the longevity of paleomagnetic polarity messages

Abstract

Viscous decay of magnetic polarity messages in rocks is slowed 3- to-6 fold by the reversing nature of the geomagnetic field, compared with the effect expected in a field that is constantly polarized oppositely to the original remanence. The process is studied analytically and numerically for the known geomagnetic polarity sequence, as well as for simulated sequences having constant-length and Poisson-distributed lengths of polarity intervals. For equal average-interval lengths, the random Poisson reversing process causes more rapid decay than does the periodic reversing process.