HR: 1340h
AN: GP33A-0934    [Abstracts]
TI: Statistical Behavior of Reversing Gravitational Dynamos
AU: * Olson, P
EM: olson@jhu.edu
AF: Johns Hopkins University, EPS, Olin Hall 3400 North Charles St, Baltimore, MD 21218, United States
AB: Gravitational dynamo models powered by compositional convection show different regimes of magnetic field statistics with increasing Rayleigh number, including nearly steady fields, chaotic non-reversing dipole fields, and chaotic reversing dipole fields. The time average dipole strength and the dipolarity of the magnetic field decrease, while the dipole variability, the average dipole tilt angle, and the frequency of polarity reversals increase with Rayleigh number. Chaotic gravitational dynamos have large amplitude dipole secular variation with maximum power at frequencies of a few cycles per million years. Dipole statistics, low frequency power spectra, and polarity reversal frequency of some of these dynamos are comparable to the geomagnetic field. The low frequency variability is driven by the Lorentz force and is characterized by an inverse correlation between dynamo magnetic and kinetic energy. A constant energy dissipation model accounts most of the low frequency statistical behavior of these dynamos.
DE: 1507 Core processes (1213, 8115)
DE: 1510 Dynamo: theories and simulations
DE: 1521 Paleointensity
DE: 1522 Paleomagnetic secular variation
DE: 1530 Rapid time variations
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting