HR: 13:55h
AN: GP33E-02 INVITED    [Abstracts]
TI: Influence of the Earth's Magnetic Field on Ellipsoidal Particle Alignment in Viscous Media
AU: * Gilder, S
EM: gilder@lmu.de
AF: Ludwig Maximilians University, Department of Earth and Environmental Sciences, Theresienstrasse 41, Munich, 80333, Germany
AU: Jezek, J
EM: jezek@natur.cuni.cz
AF: Charles University, Department of Applied Mathematics and Computer Science, Albertov 6, Prague 2, 128 43, Czech Republic
AB: We present a model that describes the rotation of ellipsoidal magnetic particles in a viscous fluid under the influence of hydrodynamic and magnetic forces, with an aim to better understand how sediments acquire their remanent magnetizations. Analyses of the governing equations elucidate how magnetic particles rotate for different values of leading parameters including particle shape, remanent and induced magnetic intensity, magnetic field intensity and direction, strain rate, shear direction, and viscosity. Numerical solution of the governing equations makes it possible to visualize the rotation path and the magnetic direction of a particle through time. Thus, the model can discern the time scales and trajectories of magnetic particles rotating due to torque of the magnetic field couple while simultaneously entrained in a velocity gradient. When applied to laboratory experiments, the viscous model successfully matches the observed data, particularly after accounting for mechanical interaction and flocculation effects. Magnetic anisotropies calculated from multiparticle systems of hematite yield typical sedimentary fabrics with relatively low percentages of anisotropy (<5%) and maximum principal axes that lie in the sedimentation plane.
DE: 1518 Magnetic fabrics and anisotropy
DE: 1522 Paleomagnetic secular variation
DE: 1535 Reversals: process, timescale, magnetostratigraphy
DE: 1540 Rock and mineral magnetism
DE: 1594 Instruments and techniques
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2007 Fall Meeting