Properties of Magnetic Viscosity

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Viscous remanent magnetization (VRM) is a remanent magnetization that is inexorably acquired during exposure to ambient magnetic fields. In nature, VRM is a secondary overprint resulting from the geomagnetic field. This VRM generally constitutes undesirable noise in paleomagnetism. Despite its ubiquity, VRM still presents great difficulty in paleomagnetic interpretation. In particular, properties of VRM vary substantially as experimental conditions change. As a result, it is dangerous to generalize the outcome of individual investigations in the laboratory to the NRM of paleomagnetic specimens. The investigators therefore propose a systematic experimental and theoretical approach that intends to explore fundamental behavior of VRM using well-defined natural and synthetic samples. Properties of pre-history, temperature, and time-dependence of VRM will be examined. They will monitor changes in the magnetic remanence vector as well as the demagnetization characteristics of VRM. In addition, experiments will be performed at elevated temperatures up to 300C to characterize properties of thermoviscous remanent magnetization (TVRM). Given the prevalence of TVRM/VRM in nature, these investigations will pave the way for a much more complete characterization of VRM and its affects on the determination of past geomagnetic field vectors.