Dipole fluctuations and the duration of geomagnetic polarity transitions

• Published in: Geophysical research letters Vol. 42; no. 18; pp. 7444 - 7451
• Main Author: Buffett, Bruce
• Format: Journal Article
• Language: English
• Published: Washington Blackwell Publishing Ltd 28.09.2015; John Wiley & Sons, Inc
• Subjects: Dipole moment; Dipole moments; Dipoles; Direction; Duration; Efficiency; Fluctuation; Fluctuations; geomagnetic reversals; Geomagnetism; Geophysics; Magnetic fields; Magnetic intensity; Magnetism; Mathematical models; Nonlinearity; Paleomagnetism; Polarity; Probability theory; Recovery; Recovery time; stochastic model; Stochastic models; Stochasticity; Trends
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1002/2015GL065700

Geomagnetic polarity transitions are often accompanied by a decrease in magnetic intensity. The time required to reestablish the magnetic intensity after a transition is usually longer than the duration based on magnetic direction. Analysis of the paleomagnetic axial dipole moment from the PADM2M model shows a return to the time‐averaged intensity after 42 kyr. A shorter time is required to recover a fraction of the time‐averaged moment, but the correspondence between recovery time and fraction of recovery is nonlinear. Predictions of a stochastic model reproduce the general trends in recovery time and suggest that fluctuations in dipole generation increase substantially during polarity transitions relative to times of stable polarity. These large fluctuations could reflect larger convective velocities in the core or represent a change in the efficiency of dipole generation. In either case, large fluctuations during polarity transitions can flip the sign of the axial dipole field several times before a polarity transition is completed. Key Points Reversal duration predicted using stochastic model Fluctuations in dipole generation increase during polarity transition Axial dipole may flip several times during a reversal