  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.
