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Reducing the Backus Effect given some knowledge of the dip‐equator
Author(s) -
UltréGuérard P.,
Hamoudi M.,
Hulot G.
Publication year - 1998
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/98gl02211
Subject(s) - equator , magnetic dip , earth's magnetic field , uniqueness , geology , geophysics , field (mathematics) , geodesy , ideal (ethics) , latitude , magnetic field , physics , mathematics , mathematical analysis , philosophy , epistemology , quantum mechanics , pure mathematics
Geomagnetic field models computed from intensity measurements on or near the Earth's surface are plagued with strong errors known as the “Backus effect”. These errors are related to the mathematical non‐uniqueness of the solution which can be theoretically removed by the knowledge of the dip‐equator location. Here, we present a new method for computing models using intensity data and additional information about the location of the dip‐equator. We first give a numerical validation of this approach in an ideal case in which the dip‐equator can be assumed to be perfectly located. We then show that in practice, updating a good past model of the field with a model of secular variation can constrain the location of the dip‐equator sufficiently for our method to be useful. Implications for the planning of future satellite missions are briefly discussed.