著者

E. DAWSON L. R. NEWITT

出版者

Society of Geomagnetism and Earth, Planetary and Space Sciences

雑誌

Journal of geomagnetism and geoelectricity (ISSN:00221392)

巻号頁・発行日

vol.34, no.4, pp.225-240, 1982 (Released:2010-03-12)

参考文献数

36

被引用文献数

9 14

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The motions of the Earth's magnetic dip poles and geomagnetic poles over the past 400 years are investigated. In addition, relations are sought between geomagnetic and virtual geomagnetic poles over historic times.Since 1750, the secular motion of the dip poles along their paths has been counterclockwise. During this century this secular motion has been directed in a northwest direction with an average velocity of -11km per year for the north dip pole and -10km per year for the south dip pole. In 1980, the north dip pole was located at 77.3°N and 101.8°W in the Canadian Archipelago, and the south dip pole at 65.6°S and 139.4°E just off mainland Antarctica.In addition to its secular motion, each dip pole undergoes a diurnal motion caused by ionospheric current systems. This motion, which is clockwise in the north and anticlockwise in the south, may result in a displacement from the unperturbed position of 65km and 30km respectively, on an average disturbed day.The average velocity of the north geomagnetic pole during this century is -1km per year in a northwest direction. It is about a magnitude less for the virtual geomagnetic pole. Both the geomagnetic and virtual geomagnetic pole paths display a clockwise rotation.There is a great deal of uncertainty in our attempt to use virtual geomagnetic poles to extend the geomagnetic pole path back in time to -7500 B. C. Much of this uncertainty is due to the sparse distribution of archeomagnetic measurements at a given epoch.