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Time-dependent mapping of the magnetic field at the core-mantle boundaryWe consider the problem of constructing a time-dependent map of the magnetic field at the core-mantle boundary. We use almost all the available data from the last 300 years to produce two maps, one for the period 1690-1840 and the other for 1840-1990. We represent the spatial dependency of the field using spherical harmonics, the time dependency using a cubic B-spline basis, and seek the smoothest solutions compatible with the observations. We argue that, for observations from permanent magnetic observatories, the most efficient strategy is to use the first differences of annual means; for satellite data, the most efficient strategy is simply to limit the number of data used so as to minimize any tendency to map the crustal field into the core field. The resulting model fits the observatory data better than any previous model. The resulting time-dependent field map exhibits much of the same structure in the field and its secular variation identified in earlier studies.
Document ID
19930037355
Acquisition Source
Legacy CDMS
Document Type
Reprint (Version printed in journal)
Authors
Bloxham, Jeremy
(Harvard Univ. Cambridge, MA, United States)
Jackson, Andrew
(Oxford Univ. United Kingdom)
Date Acquired
August 16, 2013
Publication Date
December 10, 1992
Publication Information
Publication: Journal of Geophysical Research
Volume: 97
Issue: B13
ISSN: 0148-0227
Subject Category
Geophysics
Accession Number
93A21352
Funding Number(s)
CONTRACT_GRANT: NSF EAR-91-58298
CONTRACT_GRANT: NSF EAR-88-04618
CONTRACT_GRANT: NAG5-918
CONTRACT_GRANT: NSF EAR-90-18620
CONTRACT_GRANT: NAG5-1369
Distribution Limits
Public
Copyright
Other

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