Does the Planetary Dynamo Go Cycling On? Re-examining the Evidence for Cycles in Magnetic Reversal Rate

TL;DR

This study investigates the periodicity of geomagnetic reversals over 375 million years, revealing potential cycles around 16 and 26 million years, which may relate to mantle and core-mantle dynamics.

Contribution

It provides a Fourier analysis-based re-examination of reversal periodicity, suggesting chaotic behavior with transient cycles linked to planetary interior processes.

Findings

Identified significant peaks in reversal power spectra within 16-40 Myr range.

Detected a transient 26 Myr periodicity in geomagnetic reversals.

Possible correlation of 16 Myr cycle with mantle plume pulsations.

Abstract

The record of reversals of the geomagnetic field has played an integral role in the development of plate tectonic theory. Statistical analyses of the reversal record are aimed at detailing patterns and linking those patterns to core-mantle processes. The geomagnetic polarity timescale is a dynamic record and new paleomagnetic and geochronologic data provide additional detail. In this paper, we examine the periodicity revealed in the reversal record back to 375 million years ago (Ma) using Fourier analysis. Four significant peaks were found in the reversal power spectra within the 16-40-million-year range (Myr). Plotting the function constructed from the sum of the frequencies of the proximal peaks yield a transient 26 Myr periodicity, suggesting chaotic motion with a periodic attractor. The possible 16 Myr periodicity, a previously recognized result, may be correlated with pulsation of mantle plumes and perhaps; more tentatively, with core-mantle dynamics originating near the large low shear velocity layers in the Pacific and Africa. Planetary magnetic fields shield against charged particles which can give rise to radiation at the surface and ionize the atmosphere, which is a loss mechanism particularly relevant to M stars. Understanding the origin and development of planetary magnetic fields can shed light on the habitable zone.