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Localized sudden changes in the geomagnetic secular variation. Localized sudden changes in the geomagnetic secular variation.

There is much debate as to whether there was a worldwide geomagnetic jerk in 1969 or 1970. It is agreed that there was an unusual sharp change in the secular variation in the east component, Y, in Europe at that time. This note points out how a localized sudden change in the secular variation pattern of one component in Europe can occur without having any large worldwide effects in any...
Authors
L.R. Alldredge

A model of geomagnetic secular variation for 1980-1983 A model of geomagnetic secular variation for 1980-1983

We developed an updated model of the secular variation of the main geomagnetic field during 1980 through 1983 based on annual mean values for that interval from 148 worldwide magnetic observatories. The model consists of a series of 80 spherical harmonics, up to and including those of degree and order 8. We used it to form a proposal for the 1985 revision of the International Geomagnetic...
Authors
N.W. Peddie, A.K. Zunde

Geophysics: A reversal of geomagnetic polarity Geophysics: A reversal of geomagnetic polarity

The detailed behaviour of the geomagnetic field during reversals is documented by palaeomagnetists to constrain models of the geomagnetic dynamo. Reversals are studied by measuring the magnetic remanence preserved in rocks to obtain both the direction and intensity of the ancient magnetic field.
Authors
Edward A. Mankinen

Comments on 'Remarks on the secular change in the energy density spectrum of the geomagnetic field' by Joachim Meyer. Comments on 'Remarks on the secular change in the energy density spectrum of the geomagnetic field' by Joachim Meyer.

Meyer has discussed only the Rn aspect of the Alldredge (1984) paper he is criticising. He has ignored the pictorial demonstration of the need for higher harmonics to properly describe the secular variation field than the main field as demonstrated. This more or less independent demonstration supports the general conclusion of that paper.
Authors
L.R. Alldredge

Some Techniques for Reducing Landslide Hazards Some Techniques for Reducing Landslide Hazards

Many techniques are available for reducing landslide hazards; 27 are described in this paper. Prerequisites for the successful use of these techniques are hazard information understandable to nongeologists and adequate communication of this information to those who will, or are required to, use it. It is concluded that certain factors needed to ensure the lasting effectiveness of these...
Authors
William J. Kockelman
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