HR: 1340h
AN: GP33A-0920    [Abstracts]
TI: Polarity Reversal Statistics in Geodynamo Simulations
AU: * Driscoll, P
EM: pdrisco4@jhu.edu
AF: Johns Hopkins University, Department of Earth & Planetary Sciences, 3400 N. Charles St., Baltimore, MD 21218, United States
AU: Olson, P
EM: olson@jhu.edu
AF: Johns Hopkins University, Department of Earth & Planetary Sciences, 3400 N. Charles St., Baltimore, MD 21218, United States
AB: We present 45 simulations of the geodynamo using a gravitational dynamo model driven by compositional convection in an electrically conducting 3-D fluid shell. By varying the relative effects of buoyancy and rotation these simulations span a range of dynamo behavior from strongly dipolar, non-reversing, superchron-like models to multi-polar, frequently reversing models. A transition region is found where the models have strongly dipolar fields and moderate (Earth-like) reversal frequencies of approximately 1 reversal per 12.5 dipole diffusion times. The shape of the transition region is non-monotonic as a function of the Rayleigh and Ekman input parameters. Secular changes in the relative effects of buoyancy and rotation in the Earth may be used to explain secular changes in the geodynamo reversal frequency. We investigate correlations between model statistics such as reversal frequency, dipolarity, time variations of dipole strength, local Rossby number, and magnetic and kinetic energies. We also investigate the dependence of these statistics on the Rayleigh and Ekman input parameters.
DE: 1507 Core processes (1213, 8115)
DE: 1510 Dynamo: theories and simulations
DE: 1535 Reversals: process, timescale, magnetostratigraphy
DE: 1560 Time variations: secular and longer
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting