Analysis of Geomagnetic Field Geometry Technique Consistency Using Geodynamo Simulations

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Most applications of geomagnetism operate under the assumption that the time-averaged geomagnetic field behaves closely to a geocentric axial dipole (GAD; Hospers, 1955). While there have been numerous investigations over the validity of this assumption using both numerical simulations and paleomagnetic data, the results have yielded varying, and sometimes conflicting, interpretations about the dipolarity of a time-averaged geomagnetic field (e.g. Evans, 1976; Kent & Smethurst, 1998; Evans 2006; Panzik & Evans 2014).

We address the reliability of methods used to determine geomagnetic field behavior used to interpret paleomagnetic data using a time-averaged geodynamo simulation. The produced field model from the simulations is analyzed for field morphology with two methods used to approach paleomagnetic field geometries: 1) a percent-based histogram using the final time-averaged model inclination data at all grid points along the surface, and 2) a percent-based inclination histogram determined by the best-fit Gaussian coefficients based on the dipole, quadrupole, and octupole field strength. These two methods describe the same geomagnetic field model, but may yield different morphologies which would force a change in the way paleomagnetic data is interpreted.

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Presented at the AGU Fall Meeting on December 13, 2018 in Washignton, D.C.