Ask A Scientist© Physics Archive

Question:  According to Trinklein in  somewhere around Akron,
Ohio the magnetic declination is 0 .  Also according to Trinklein the magnetic
north pole is at 100 longitude (& 73 latitude) which, according to my globe
makes Topeka, Kansas the point with 0  declination, not Akron...
Any insights? Thanks
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Answer:  The earth's magnetic field is not a perfect dipole...
far from it, in fact: there are many deviations due to localized
concentrations of ferro-magnetic ores in the earth's crust, for example.
John Hawley
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Earth's magnetic field is constantly changing, both in space
(geographically) and in time.  The current (2003) declination for Akron,
OH is about 8 degrees west of north (based on the International
Geomagnetic Reference Field, 2000 http://www.ngdc.noaa.gov/).  Because the
field is constantly changing, the "0 degree line" and the location of the
north and south geomagnetic poles also change.  Currently, the 0
declination line runs roughly from New Orleans through Duluth, MN up
through Churchill in Canada.  The current approximate location of the
north and south magnetic poles (surveyed) are 78.5 N, 103.4 W near Ellef
Ringnes Island and 65 S, 139 E in Commonwealth Bay.

Susan McLean, National Geophysical Data Center, Geomagnetism Group
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