HR: 15:25h
AN: GP33A-08    [Abstracts]
TI: On the Resolution of the Magnetic Field at the Core-Mantle Boundary
AU: * Bloxham, J
EM: jeremy\_bloxham@harvard.edu
AF: Harvard University, 20 Oxford Street, Cambridge, MA 02138 United States
AU: Dumberry, M
EM: dumberry@geophysics.harvard.edu
AF: Harvard University, 20 Oxford Street, Cambridge, MA 02138 United States
AB: A fundamental difficulty in mapping the magnetic field at the core-mantle boundary is the uncertain spatial resolution of the field there from surface and satellite data. Since Magsat in 1980, and quite possibly for earlier times too, spatial resolution has been limited not by data quality but instead by the presence of the crustal field which obscures the field from the core above some spherical harmonic degree. Unfortunately, where this switch-over occurs is poorly understood, but is most probably somewhere in the range from degree 12 to 16. Magnetic field maps with power only to degree 12 look very different from maps with power to degree 16. Here we discuss possible approaches to understanding where this switch-over occurs. Two possible approaches are first to attempt to understand the crustal field by forward modelling; a second is to test the consistency of core field maps with a simple, physical model of core dynamics. Using the second approach we argue that maps of the field at the core-mantle boundary produced over the last two decades are overly conservative, and that it is probable that we can resolve more detail in the core field than previously supposed.
DE: 1510 Dynamo theories
DE: 1545 Spatial variations (all harmonics and anomalies)
DE: 1560 Time variations--secular and long term
SC: Geomagnetism and Paleomagnetism [GP]
MN: 2004 AGU Fall Meeting