Spherical harmonic analysis of the geomagnetic field of the Brunhes epoch

Ádám, Norbert; Ben'kova, N. P.; Chramo, A. N.; Cherevko, T. N.; Bucha, Václav

doi:10.1007/bf01635422

Cited by 8 publications

(5 citation statements)

References 2 publications

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“…However, in order to minimize this possibility, Creer et al (1973) took care to group the palaeomagnetic data into 20 regional control points which were well distributed over the surface of the globe and, as comparison of lines 3 and 4 of Table 2 shows, the methods they used to analyse the Brunhes field successfully recover the coordinates of the geomagnetic centre when applied to the 1965 IGRF. The distribution of control points utilizing palaeomagnetic inclination only adopted by Adam et al (1975), however, yields smaller z and larger x displacements (line 6) than the accepted values for the 1965 IGRF (line 4) and this systematic error is reflected when the displacements calculated for the Brunhes field (line 5) are compared with those given in lines 1 and 2.…”

Section: Mathematical Representation Of the Fieldmentioning

confidence: 97%

“…It is invariably assumed in palaeomagnetic studies that the time-averaged geomagnetic field possessed axial dipole symmetry (the ADF hypothesis) and while this is undoubtedly true to the first order, it is not strictly true as evidenced by the non-zero values of the quadrupole components calculated for the Brunhes field (Creer et al 1973;Georgi 1974;Adam et al 1975). Although the equatorial dipole components average down to little more than 10 per cent of the annual-mean magnitudes for 1965 and 1975, the g o 2 axial quadrupole term is very nearly equal to its present epoch value and the g: and h: terms are respectively 38 and 16 per cent of the present epoch values ( Table 1).…”

Section: Mathematical Representation Of the Fieldmentioning

confidence: 99%

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Geomagnetic secular variations during the last 25 000 years: an interpretation of data obtained from rapidly deposited sediments

Creel

1977

Geophysical Journal International

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Secular variations of geomagnetic declination and inclination recorded by lacustrine and cave sediments from North-west Europe, the Great Lakes region of North America and the Black Sea through the last 25 000 yr have a regional character and therefore cannot be attributed primarily to westward drift which is one of the main features associated with historic secular variations. A geomagnetic model in which the non-dipole field originates from stationary oscillating or pulsating sources situated in the outer core is favoured and the origin of geomagnetic excursions is discussed. 50O.4 4 O . 5 97O.O 3 O . 2 Notes.n labels the A-H dipole source (Fig. 1); AD is the amplitude of SV in declination produced by this source; \Ir is the great circle distance, measured in degrees of arc on the geosurface, between source and observing station. To fiid the combined effect of all A-H RD, the individual x, y and z field components must be added, taking into account the frequency and phase of each source.

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Section: Mathematical Representation Of the Fieldmentioning

confidence: 97%

Section: Mathematical Representation Of the Fieldmentioning

confidence: 99%

Geomagnetic secular variations during the last 25 000 years: an interpretation of data obtained from rapidly deposited sediments

Creel

1977

Geophysical Journal International

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“…Willie ADAM et al (1975), BARRACLOUGH (1974, CHEREVKO (1972), CREER et al (1973) and GEORGi (1974) used the relations…”

Section: Discussionmentioning

confidence: 99%

Uniqueness probems in the spherical harmonic analysis of the geomagnetic field direction data.

Kono

1976

J. geomagn. geoelec

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It is shown that if the field directions (inclination and declination, or other combination of two independent angles) are completely known on the surface of the earth, the geomagnetic potential can be determined uniquely except an arbitrary multiplicative constant. On the other hand, when declinations only are specified on the surface there are infinitely many potentials which satisfy exactly the same boundary conditions. Such non-uniqueness seems also to be present for the cases of other incomplete data set composed of one angle only. The uniqueness theorem serves as the basis for spherical harmonic analyses of the paleomagnetic field.

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“…Yet, first, the scale of the compression structural features produced after the Late Hercynian orogeny corresponds to the maximum compression of a few hundred meters which is incomparable with the compression estimate of hundreds of kilometers. Secondly, the Mz-Kz tectonic activity was marked mainly by longitudinal faults [Bachmanov et al, 2001].…”

Section: Tectonicsmentioning

confidence: 99%

“…[6] Khramov et al [1982] suggested the possibility of some displacement of the dipole relative to the Earth's center (which is equivalent to the presence of some unzoned members in the spherical harmonic decomposition of the paleomagnetic field (TAF)), proceeding from the papers of Adam et al [1975] and Benkova et al [1973]. In their papers these authors used the nonspherical harmonic representation of the averaged field, assuming obviously that the model they used, although being highly idealized, had a greater physical content than any spherical model.…”

mentioning

confidence: 99%

New paleomagnetic data for the Permian-Triassic Trap rocks of Siberia and the problem of a non-dipole geomagnetic field at the Paleozoic-Mesozoic boundary

Veselovskiy¹,

Павлов²

2006

Russ. J. Earth Sci.

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1] The thorough analysis of the available Permian-Triassic paleomagnetic data for the Siberian Platform and "Stable" Europe was carried out. Paleomagnetic poles, meeting to modern reliability criteria, were used to calculate the mean Permian-Triassic paleomagnetic poles of Siberia and Europe. The comparison of the resulting poles showed significant differences between them. Discussed in this paper are four potential factors that had caused the observed differences between the paleomagnetic poles of Siberia and Europe: (1) the large-scale relative movements of these cratons in post-Paleozoic time, (2) the different ages of the compared paleomagnetic poles, (3) the substantial contribution of non-dipole components to the geomagnetic field at the Paleozoic-Mesozoic boundary, and (4) the shallowing of the magnetic inclination in the European sedimentary rocks. Also discussed is the adequacy of the data selection. Arguments are advanced to prove that the possibility of the post-Paleozoic large-scale relative displacements of the cratonic blocks discussed as well as considerable age difference of their mean poles is unlikely. Also estimated were the input quadrupolar and octupolar sources in the total time-average geomagnetic field and also values of the inclination shallowing factor, which might have explained the observed discordance of the Siberian and European poles. The best agreement of the European and Siberian paleomagnetic data was achieved for the octupolar coefficient g 3 = −10% or for the inclination shallowing factor f = 0.62. Our calculations showed that the statistically significant difference between the Siberian and European average poles can be removed assuming a very small value of the inclination shallowing corresponding to the f values of 0.9 to 0.95, potentially associated with some compaction of the studied sedimentary rocks. This gives grounds for interpreting the low inclinations in the European objects as the most probable source of the observed disagreement between the European and Siberian paleomagnetic data. INDEX TERMS: 1520 Geomagnetism and Paleomagnetism: Magnetostratigraphy; 1525 Citation: Veselovskiy, R. V., and V. E. Pavlov (2006), New paleomagnetic data for the Permian-Triassic Trap rocks of Siberia and the problem of a non-dipole geomagnetic field at the Paleozoic-Mesozoic boundary, Russ.

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Spherical harmonic analysis of the geomagnetic field of the Brunhes epoch

Cited by 8 publications

References 2 publications

Geomagnetic secular variations during the last 25 000 years: an interpretation of data obtained from rapidly deposited sediments

Geomagnetic secular variations during the last 25 000 years: an interpretation of data obtained from rapidly deposited sediments

Uniqueness probems in the spherical harmonic analysis of the geomagnetic field direction data.

New paleomagnetic data for the Permian-Triassic Trap rocks of Siberia and the problem of a non-dipole geomagnetic field at the Paleozoic-Mesozoic boundary

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