Rectangular harmonic analysis applied to the geomagnetic field

Alldredge, Leroy R.

doi:10.1029/jb086ib04p03021

Cited by 68 publications

(41 citation statements)

References 4 publications

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“…Common techniques, like polynomial modelling in latitude and longitude, rectangular harmonic analysis (Alldredge 1981), or spherical cap harmonics (Haines 1985) often used in the past (Torta et al 2006), should not be used when data are available at different altitudes (Mandea and Purucker 2005;Thébault and Gaya-Piqué 2008;Schott and Thébault 2010). The Revised Spherical Cap Harmonic Analysis, R-SCHA (Thébault et al 2004(Thébault et al , 2006aThébault 2008), is a regional method specifically derived for modelling magnetic data collected at various altitudes.…”

Section: Reconciling Ground and Satellite Datamentioning

confidence: 99%

The Magnetic Field of the Earth’s Lithosphere

et al. 2010

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The lithospheric contribution to the Earth's magnetic field is concealed in magnetic field data that have now been measured over several decades from ground to satellite altitudes. The lithospheric field results from the superposition of induced and remanent magnetisations. It therefore brings an essential constraint on the magnetic properties of rocks of the Earth's sub-surface that would otherwise be difficult to characterize. Measuring, extracting, interpreting and even defining the magnetic field of the Earth's lithosphere is however challenging. In this paper, we review the difficulties encountered. We briefly summarize the various contributions to the Earth's magnetic field that hamper the correct identification of the lithospheric component. Such difficulties could be partially alleviated with the joint analysis of multi-level magnetic field observations, even though one cannot avoid making compromises in building models and maps of the magnetic field of the Earth's lithosphere E. Thébault ( ) 96 E. Thébault et al.at various altitudes. Keeping in mind these compromises is crucial when lithospheric field models are interpreted and correlated with other geophysical information. We illustrate this discussion with recent advances and results that were exploited to infer statistical properties of the Earth's lithosphere. The lessons learned in measuring and processing Earth's magnetic field data may prove fruitful in planetary exploration, where magnetism is one of the few remotely accessible internal properties.

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Section: Reconciling Ground and Satellite Datamentioning

confidence: 99%

The Magnetic Field of the Earth’s Lithosphere

et al. 2010

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“…The basis functions are thus essentially the periodic ones discussed in this paper, except that the coordinates x, y, and z have been introduced as additional basis functions (ALLDREDGE, 1981). (These additional basis functions not only destroy the orthogonality but also violate the boundary condition of zero potential at infinite z.)…”

Section: Analytical Example For F (X)=xmentioning

confidence: 99%

Modelling by series expansions: A discussion.

Haines

1990

J. geomagn. geoelec

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“…Common techniques, like polynomial modeling in latitude and longitude or rectangular harmonic analysis (Alldredge, 1981), have been successfully applied before the new satellite era. The data for this technique are provided by aeromagnetic and ship-borne magnetic surveys (obtained at different times with varied flight elevations, flight-line or track spacing, and data-reduction procedures) or for repeat station networks (obtained at different times and with a network more or less dense).…”

Section: Polynomial Modelingmentioning

confidence: 99%

Observing, Modeling, and Interpreting Magnetic Fields of the Solid Earth

Mandea

Purucker

2005

Surv Geophys

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Many Earth system processes generate magnetic fields, either primary magnetic fields or in response to other magnetic fields. The largest of these magnetic fields is due to the dynamo in the Earth's core, and can be approximated by a geocentric axial dipole that has decayed by nearly 10% during the last 150 years. This is an order of magnitude faster than its natural decay time, a reflection of the growth of patches of reverse flux at the core-mantle boundary. The velocity of the North magnetic pole reached some 40 km/yr in 2001. This velocity is the highest recorded so far in the last two centuries. The second largest magnetic field in the solid Earth is caused by induced and remanent magnetization within the crust. Controlled in part by the thermo-mechanical properties of the crust, these fields contain signatures of tectonic processes currently active, and those active in the distant past. Recent work has included an estimate of the surface heat flux under the Antarctic ice cap. In order to understand the recent changes in the Earth's magnetic field, new high-quality measurements are needed to continue those being made by Ørsted (launched in 1999), CHAMP and the Ørsted-2 experiment onboard SAC-C (both launched in 2000). The present paper is motivated by the advent of space surveys of the geomagnetic field, and illustrates how our way of observing, modeling, and interpreting the Earth's magnetic field has changed in recent years due to the new magnetic satellite measurements.

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Rectangular harmonic analysis applied to the geomagnetic field

Cited by 68 publications

References 4 publications

The Magnetic Field of the Earth’s Lithosphere

The Magnetic Field of the Earth’s Lithosphere

Modelling by series expansions: A discussion.

Observing, Modeling, and Interpreting Magnetic Fields of the Solid Earth

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