HR: 0800h
AN: GP31A-0085    [Abstracts]
TI: A role for the time-varying interplanetary magnetic field in the origin of the geodynamo
AU: * Mukherjee, S
EM: smukherjee@geo.tamu.edu
AF: Texas A&M University, Dept. of Geology and Geophysics, College Station, TX 77845 United States
AU: Everett, M E
EM: everett@geo.tamu.edu
AF: Texas A&M University, Dept. of Geology and Geophysics, College Station, TX 77845 United States
AB: Current theories explain the origin and maintenance of the geodynamo in terms of convection in the fluid outer core and its differential rotation with respect to the inner core. The existence of the geomagnetic field prior to formation of the inner core has long been a difficulty in geodynamo theory. New solar and astrophysical observations have re-opened the possibility that an external source established and maintained a strong magnetic field deep within the planet prior to the formation of the inner core. We present simple 1-D time-domain calculations of electromagnetic induction which suggest that a decaying interplanetary magnetic field (IMF) associated with the secular spin down in solar rotation can generate enough electromotive force in the deep interior to drive and sustain an internal magnetic field over billions of years. The external, time-varying IMF is capable of generating a stable, sizeable magnetic field in Earth's core during and after planetary differentiation and up to the time of formation of the inner core, at which time we presume that convection mechanisms begin to assume a dominant role in kick-starting the geodynamo proper. The geodynamo need not have required the amplication of a tiny seed field to get started; instead, an externally generated, stable and sizeable magnetic field was already in place and capable of driving fluid motions.
DE: 1510 Dynamo: theories and simulations
DE: 1515 Geomagnetic induction
SC: Geomagnetism and Paleomagnetism [GP]
MN: Fall Meeting 2005