A model of the geomagnetic field for 1975

Peddie, Norman W.; Fabiano, E. B.

doi:10.1029/jb081i014p02539

Cited by 51 publications

(10 citation statements)

References 5 publications

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“…If they did, the required rate of change in direction would be as high as 1.5 o per year. This figure is one and a half orders of magnitude higher than the maximum observed rate of change at mid-latitudes for the present field (Peddie and Fabiano, 1976). In addition it is inconsistent with our present information concerning the rate at which energy can be partitioned among the spherical harmonic coefficients (Verosub and Cox, 1971).…”

Section: Intra-site and Inter-site Variabilitycontrasting

confidence: 56%

Paleomagnetism of varved sediments from western New England: Variability of the paleomagnetic recorder

Verosub¹

1979

Geophysical Research Letters

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Comparison of the paleomagnetic directions recorded by varved sediments in western New England has provided a means of determining the inherent variability of the paleomagnetic recorder of depositional detrital remanent magnetism. Although a given varve has a stable, well‐defined direction of magnetization, successive sampling horizons at the same site as well as the same sampling horizon at different sites may show variations of as much as 8° in inclination and 15° in declination. This variability is attributed not to the secular variation of the geomagnetic field but rather to the physical factors which can influence the magnetic direction recorded by a sediment. Since the time scale for changes in these factors is comparable to the time scale for changes of the geomagnetic field, it may not always be possible to distinguish the true variation of the geomagnetic field from the variability of the paleomagnetic recorder. In certain circumstances correlation of sedimentary sequences on the basis of apparent secular variation will thus be impossible.

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Section: Intra-site and Inter-site Variabilitycontrasting

confidence: 56%

Paleomagnetism of varved sediments from western New England: Variability of the paleomagnetic recorder

Verosub¹

1979

Geophysical Research Letters

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“…2. The anomaly data ( X R , Y R , Z R ) are the residuals obtained by subtracting values synthesized from the 12th order and degree spherical harmonic model of Peddie & Fabiano (1976) from X, Y and Z ; they, too, are given in Table 1 of Alldredge (1981).…”

Section: Datamentioning

confidence: 99%

Assessment of regional geomagnetic field modelling methods using a standard data set: spherical cap harmonic analysis

Düzgit

Malin

2000

Geophysical Journal International

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Various methods that take account of the potential nature of the field have been proposed for modelling geomagnetic data on a regional scale. Several of these have been applied to a standard data set based on annual mean values from observatories in Europe. Here, we examine some of the properties of spherical cap harmonic analysis when applied to this data set, and compare the quality of fit with that of the other models. It is found that, for this data set, rectangular polynomial analysis provides a compact fit to main field data, but that in most other cases, for both main field and anomaly data, spherical cap harmonic analysis provides the better fit. Although relatively insensitive to chosen cap size, spherical cap harmonic analysis deteriorates more rapidly than the other methods when the number of coefficients is reduced.

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“…That is, the application of his method did not eliminate any of the lower order terms, and the number of coefficients matched quite well what others had used previously. When the coefficients in a geomagnetic spherical harmonic analysis are greatly overdetermined, the RMS residual for all three components is normally about 200 nT (PEDDIE and FABIANO, 1976), which is attributed mainly Table 1). The annual average sunspot numbers are also shown.…”

Section: Number Coefficients Determinedmentioning

confidence: 99%

Solar cycle variation in geomagnetic external spherical harmonic coefficients.

Alldredge

Stearns

Sugiura

1979

J. geomagn. geoelec

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The first degree external spherical harmonic coefficients are obtained for each year of a 12-year period centered at 1958.5, using annual mean values of X, Y, and Z components from 54 magnetic observatories. Values of the coefficient g0e of the zonal first degree harmonic clearly show a solar cycle variation. The peak-to-peak amplitude of the variation is approximately 29 nT, which is consistent with values obtained earlier by first filtering data to retain only those variations having periods near the solar cycle and then subjecting the filtered data to a spherical harmonic analysis. The variation in g0e is found to correlate extremely well with the annual mean Ds, index and with the annual number of days having Ap>60. Based on statistics of the mean square successive difference, an explanation is presented why the obtained solar cycle variation in g0e, which is very much smaller in magnitude than the standard deviations calculated by the conventional method, is statistically meaningful. The determined absolute (not relative) values of gie are in agreement, within several nanotesla, with the expectation from a theoretical model of solar wind compression of the magnetosphere and an analysis of the Dst index.

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A model of the geomagnetic field for 1975

Cited by 51 publications

References 5 publications

Paleomagnetism of varved sediments from western New England: Variability of the paleomagnetic recorder

Paleomagnetism of varved sediments from western New England: Variability of the paleomagnetic recorder

Assessment of regional geomagnetic field modelling methods using a standard data set: spherical cap harmonic analysis

Solar cycle variation in geomagnetic external spherical harmonic coefficients.

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