Earth's Magnetic Field: Its Source and Behavior

University Of California-San Diego Scripps Inst Of Oceanography, La Jolla CA

Investigators

Abstract

Constable 0000944 One of the most enduring issues in geophysics is concerned with understanding why the Earth has a magnetic field and why it displays such a variety of temporal variation. Fluid motion in the Earth's liquid-iron outer core is responsible for most of the magnetic field's secular variation, and it is also responsible for maintaining the main part of the field itself. The researchers will investigate reduced-dimensional solutions to the magneto-hydrodynamic equations describing the geodynamo. On account of their simplicity, and resulting savings in computer memory and time, a number of geophysically important issues can be addressed. In particular, the role of the Ekman number, which measures the relative importance of fluid viscosity and the Coriolis force, can be studied systematically. An unresolved issue, which they shall address is whether or not in the geophysically relevant limit of small Ekman number (low viscosity) the Earth's dynamo operates in a state that is independent of viscous core-mantle coupling. It is expected that the simulated magnetic field will exhibit highly time-dependent, and possibly chaotic, variation with vanishingly small Ekman number. In comparing these dynamo simulations with the paleomagnetic polarity timescale and paleosecular variation recorded in sedimentary and lava data, the investigators will analyze both the data and the simulated magnetic field with similar tools and methods, including: phase analysis, stationary and non-stationary statistical modelling, and multi-taper spectral techniques.