Magnetic signals from the core of the earth and secular variation.
Journal of Geophysical Research
By: L.R. Alldredge
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Abstract
An oscillating, radial magnetic dipole source was assumed to exist in the core of the earth, 100 km beneath the core-mantle boundary. As an approximation, electromagnetic propagation was assumed in the core in lieu of hydromagnetic propagation, which could not be used because of unknown internal fields. Using Debye potentials, the radial and horizontal components of the surface fields were calculated using various assumed conductivity parameters in the core and in the mantle. It is concluded that most spherical harmonic models of the earth's magnetic field do not include enough terms to describe properly the field of core sources with periods of tens of years. These short-period variations are especially important in describing the secular variation. Because of this, a proper description of the secular variation requires more spherical harmonic terms than are required for the field itself. Inadequate representation of short-period variations in spherical harmonic models may contribute to the rapid deterioration of predictive models. Alternatives to spherical harmonic analysis for secular variation should be investigated; regardlesss of the method used, a much greater spatial distribution of high quality secular variation data is needed. -Author
| Publication type | Article |
|---|---|
| Publication Subtype | Journal Article |
| Title | Magnetic signals from the core of the earth and secular variation. |
| Series title | Journal of Geophysical Research |
| Volume | 86 |
| Issue | B9 |
| Year Published | 1981 |
| Language | English |
| Larger Work Type | Article |
| Larger Work Subtype | Journal Article |
| Larger Work Title | Journal of Geophysical Research |
| First page | 7957 |
| Last page | 7965 |
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