The westward drift of the Earth's magnetic field

1950 ◽  
Vol 243 (859) ◽  
pp. 67-92 ◽  
Keyword(s):  
Magnetic Field ◽  
Secular Variation ◽  
Outer Part ◽  
Earth’S Magnetic Field ◽  
Dynamo Theory ◽  
The Core ◽  
The Earth ◽  
Earth's Magnetic Field ◽  
Harmonic Analyses ◽  
Westward Drift

The westward drift of the non-dipole part of the earth’s magnetic field and of its secular variation is investigated for the period 1907-45 and the uncertainty of the results discussed. It is found that a real drift exists having an angular velocity which is independent of latitude. For the non-dipole field the rate of drift is 0.18 ± 0-015°/year, that for the secular variation is 0.32 ±0-067°/year. The results are confirmed by a study of harmonic analyses made between 1829 and 1945. The drift is explained as a consequence of the dynamo theory of the origin of the earth’s field. This theory required the outer part of the core to rotate less rapidly than the inner part. As a result of electromagnetic forces the solid mantle of the earth is coupled to the core as a whole, and the outer part of the core therefore travels westward relative to the mantle, carrying the minor features of the field with it.

Secular variation of the Earth's magnetic field revealed by Mexican Geomagnetic Repeat Stations during the last two centuries

2021 ◽  
pp. 103652
Author(s):  
Avto Goguitchaichvili ◽  
Esteban Hernández ◽  
Rafael García ◽  
Vadim Kravchinsky ◽  
Rubén Cejudo ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Secular Variation ◽  
Earth’S Magnetic Field ◽  
Earth's Magnetic Field

Partial Castastrophism and Pick & Choose Empiricism: The Science of “Creationist” Geology

1984 ◽  
Vol 1 ◽  
pp. 50-65
Author(s):  
William J. Frazier
Keyword(s):  
Magnetic Field ◽  
Sedimentary Rocks ◽  
Decay Rates ◽  
Igneous Rocks ◽  
Earth’S Magnetic Field ◽  
Organic Evolution ◽  
The Earth ◽  
Scientific Principles ◽  
Earth's Magnetic Field ◽  
Repeated Use

“Scientific creationists” have created their own version of geology in order to defend their axiomatic insistance on a young Earth. To “prove” the Earth's youth, they cite (among other things) measured decay-rates of Earth's magnetic field and concentrations of elements in seawater. They also state that all plutons are quick frozen, that plutonic igneous rocks bear no relation to modern volcanism, and that all sedimentary rocks must be interpreted in terms of a “global hydrologic singularity,” i.e. Noah's Flood.Having explicitly denied uniformitarianism and embraced catastrophism, “Creationists” renege by using uniformitarian reasoning over and again. They practice “pick & choose” empiricism by citing only those data which seem to support their case. “Creationists” even choose when and if to apply scientific principles, e.g. their use of thermodynamics to “disprove” organic evolution while ignoring thermodynamics' implications for magma cooling and metamorphism.The methods of “Creationism” are clearly intended not to increase knowledge of the Earth but to delude the scientifically unsophisticated. Thus, “Creationism” can hardly be considered a science. Further, its repeated use of fallacious thinking brands “Creationism” as hopelessly illogical and its disingenuous statements and tactics disqualify it from even the ranks of nonempirical epistemological systems.

Modelling the core magnetic field of the Earth

1982 ◽  
Vol 306 (1492) ◽  
pp. 179-191 ◽  
Keyword(s):  
Magnetic Field ◽  
Spherical Harmonics ◽  
Secular Variation ◽  
Long Wavelength ◽  
Core Field ◽  
The Core ◽  
The Earth ◽  
High Degree ◽  
Current Systems ◽  
The Magnetic Field

The magnetic field generated in the core of the Earth is often represented by spherical harmonics of the magnetic potential. It has been found from looking at the equations of spherical harmonics, and from studying the values of the spherical harmonic coefficients derived from data from Magsat, that this is an unsatisfactory way of representing the core field. Harmonics of high degree are characterized by generally shorter wavelength expressions on the surface of the Earth, but also contain very long wavelength features as well. Thus if it is thought that the higher degree harmonics are produced by magnetizations within the crust of the Earth, these magnetizations have to be capable of producing very long wavelength signals. Since it is impossible to produce very long wavelength signals of sufficient amplitude by using crustal magnetizations of reasonable intensity, the separation of core and crustal sources by using spherical harmonics is not ideal. We suggest that a better way is to use radial off-centre dipoles located within the core of the Earth. These have several advantages. Firstly, they can be thought of as modelling real physical current systems within the core of the Earth. Secondly, it can be shown that off-centred dipoles, if located deep within the core, are more effective at removing long wavelength signals of potential or field than can be achieved by using spherical harmonics. The disadvantage is that it is much more difficult to compute the positions and strengths of the off-centred dipole fields, and much less easy to manipulate their effects (such as upward and downward continuation). But we believe, along with Cox and Alldredge & Hurwitz, that the understanding that we might obtain of the Earth’s magnetic field by using physically reasonable models rather than mathematically convenient models is very important. We discuss some of the radial dipole models that have been proposed for the nondipole portion of the Earth’s field to arrive at a model that agrees with observations of secular variation and excursions.

scholarly journals Multipole Analysis. II. Geomagnetic Secular Variation

1969 ◽  
Vol 22 (4) ◽  
pp. 481 ◽  
Author(s):  
RW James
Keyword(s):  
Magnetic Field ◽  
Secular Variation ◽  
Time Trends ◽  
Earth’S Magnetic Field ◽  
Geomagnetic Secular Variation ◽  
Rates Of Change ◽  
Multipole Analysis ◽  
Earth's Magnetic Field

The method of multipole analysis described in Part I is applied to the Earth's magnetic field for various epochs between 1845 and 1965, allowing the geomagnetic secular variation to be illustrated by time trends in the multipole parameters. The rates of change of the multipole parameters are used to separate the secular variation into non.drifting, meridional drifting, and longitudinal drifting components, which are discussed in detail for the epoch 1965.

scholarly journals A theory of the Earth's magnetic field and of sunspots, based on a self-excited dynamo incorporating the Hall effect

2001 ◽  
Vol 8 (4/5) ◽  
pp. 265-279 ◽  
Author(s):  
A. de Paor
Keyword(s):  
Magnetic Field ◽  
Hall Effect ◽  
Energy Coupling ◽  
Order System ◽  
Sunspot Activity ◽  
Earth’S Magnetic Field ◽  
Dynamo Theory ◽  
Field Reversal ◽  
Geophysical Processes ◽  
Earth's Magnetic Field

Abstract. A new viewpoint on the generation and maintenance of the Earth's magnetic field is put forward, which integrates self-exciting dynamo theory with the possibility of energy coupling along orthogonal axes provided by the Hall effect. A nonlinear third-order system is derived, with a fourth equation serving as an observer of unspecified geophysical processes which could result in field reversal. Lyapunov analysis proves that chaos is not intrinsic to this system. Relative constancy of one of the variables produces pseudo equilibrium in a second order subsystem and allows for self-excitation of the geomagnetic field. Electromagnetic analysis yields expressions for key parameters. Models for secular variations recorded at London, Palermo and at the Cape of Good Hope over the past four hundred years are offered. Offset of the Earth's magnetic axis from the geographic axis is central to time-varying declination, but its causes have not yet been established. Applicability of the model to the explanation of sunspot activity is outlined. A corroborating experiment published by Peter Barlow in 1831 is appended.

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