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Pole-strength of the earth from Magsat and magnetic determination of the core radiusA model based on two days of Magsat data is used to numerically evaluate the unsigned magnetic flux linking the earth's surface, and a comparison of the 16.054 GWb value calculated with values from earlier geomagnetic field models reveals a smooth, monotonic, and recently-accelerating decrease in the earth's pole strength at a 50-year average rate of 8.3 MWb, or 0.052%/year. Hide's (1978) magnetic technique for determining the radius of the earth's electrically-conducting core is tested by (1) extrapolating main field models for 1960 and 1965 downward through the nearly-insulating mantle, and then separately comparing them to equivalent, extrapolated models of Magsat data. The two unsigned fluxes are found to equal the Magsat values at a radius which is within 2% of the core radius; and (2) the 1960 main field and secular variation and acceleration coefficients are used to derive models of 1930, 1940 and 1950. The same core magnetic radius value, within 2% of the seismic value, is obtained. It is concluded that the mantle is a nearly-perfect insulator, while the core is a perfect conductor, on the decade time scale.
Document ID
19820047246
Document Type
Reprint (Version printed in journal)
Authors
Voorhies, G. V. (Colspan, Inc. Boulder, CO, United States)
Benton, E. R. (Colorado, University Boulder, CO, United States)
Date Acquired
August 10, 2013
Publication Date
April 1, 1982
Publication Information
Publication: Geophysical Research Letters
Volume: 9
Subject Category
GEOPHYSICS
Funding Number(s)
CONTRACT_GRANT: NSF EAR-79-26120
CONTRACT_GRANT: NAS5-25957
Distribution Limits
Public
Copyright
Other