An Equivalent Source Method for Modelling the Global Lithospheric Magnetic Field

Research output: Contribution to journalConference abstract in journalResearchpeer-review

181 Downloads (Pure)

Abstract

We present a new technique for modelling the global lithospheric magnetic field at Earth's surface based on the estimation of equivalent potential field sources. As a demonstration we show an application to magnetic field measurements made by the CHAMP satellite during the period 2009-2010 when it was at its lowest altitude and solar activity was also remarkably quiet. Both scalar and three component vector field data are utilized. Estimates of core and large-scale magnetospheric sources are removed from the measurements using the CHAOS-4 model. Quiet-time and night-side data selection criteria are also employed to minimize the influence of the ionospheric field. The model for the remaining lithospheric magnetic field consists of magnetic point sources (monopoles) arranged in an icosahedron grid. The corresponding source values are estimated using an iteratively reweighted least squares algorithm that includes model regularization and Huber weighting. Data error covariance matrices are implemented, including both the latitude dependence of data error variances and covariances between the vector field components due to unmodelled sources. Results show good consistency with the field structures obtained in the CHAOS-4 and MF7 models using more conventional spherical harmonic based approaches. Advantages of the equivalent source method include its local nature, allowing e.g. for regional grid refinement, and the ease of transforming to spherical harmonics when needed. Future applications will make use of Swarm data in combination with high resolution aeromagnetic measurements.
Original languageEnglish
Article numberEGU2014-6673
JournalGeophysical Research Abstracts
Volume16
Number of pages1
ISSN1607-7962
Publication statusPublished - 2014
EventEuropean Geosciences Union General Assembly 2014 - Vienna, Austria
Duration: 27 Apr 20142 May 2014

Conference

ConferenceEuropean Geosciences Union General Assembly 2014
CountryAustria
CityVienna
Period27/04/201402/05/2014

Cite this

@article{d7885cc3e1aa4aaa80a18853cfd4ce5e,
title = "An Equivalent Source Method for Modelling the Global Lithospheric Magnetic Field",
abstract = "We present a new technique for modelling the global lithospheric magnetic field at Earth's surface based on the estimation of equivalent potential field sources. As a demonstration we show an application to magnetic field measurements made by the CHAMP satellite during the period 2009-2010 when it was at its lowest altitude and solar activity was also remarkably quiet. Both scalar and three component vector field data are utilized. Estimates of core and large-scale magnetospheric sources are removed from the measurements using the CHAOS-4 model. Quiet-time and night-side data selection criteria are also employed to minimize the influence of the ionospheric field. The model for the remaining lithospheric magnetic field consists of magnetic point sources (monopoles) arranged in an icosahedron grid. The corresponding source values are estimated using an iteratively reweighted least squares algorithm that includes model regularization and Huber weighting. Data error covariance matrices are implemented, including both the latitude dependence of data error variances and covariances between the vector field components due to unmodelled sources. Results show good consistency with the field structures obtained in the CHAOS-4 and MF7 models using more conventional spherical harmonic based approaches. Advantages of the equivalent source method include its local nature, allowing e.g. for regional grid refinement, and the ease of transforming to spherical harmonics when needed. Future applications will make use of Swarm data in combination with high resolution aeromagnetic measurements.",
author = "Kother, {Livia Kathleen} and Hammer, {Magnus Danel} and Chris Finlay and Nils Olsen",
year = "2014",
language = "English",
volume = "16",
journal = "Geophysical Research Abstracts",
issn = "1607-7962",
publisher = "Copernicus GmbH",

}

An Equivalent Source Method for Modelling the Global Lithospheric Magnetic Field. / Kother, Livia Kathleen; Hammer, Magnus Danel; Finlay, Chris; Olsen, Nils.

In: Geophysical Research Abstracts, Vol. 16, EGU2014-6673, 2014.

Research output: Contribution to journalConference abstract in journalResearchpeer-review

TY - ABST

T1 - An Equivalent Source Method for Modelling the Global Lithospheric Magnetic Field

AU - Kother, Livia Kathleen

AU - Hammer, Magnus Danel

AU - Finlay, Chris

AU - Olsen, Nils

PY - 2014

Y1 - 2014

N2 - We present a new technique for modelling the global lithospheric magnetic field at Earth's surface based on the estimation of equivalent potential field sources. As a demonstration we show an application to magnetic field measurements made by the CHAMP satellite during the period 2009-2010 when it was at its lowest altitude and solar activity was also remarkably quiet. Both scalar and three component vector field data are utilized. Estimates of core and large-scale magnetospheric sources are removed from the measurements using the CHAOS-4 model. Quiet-time and night-side data selection criteria are also employed to minimize the influence of the ionospheric field. The model for the remaining lithospheric magnetic field consists of magnetic point sources (monopoles) arranged in an icosahedron grid. The corresponding source values are estimated using an iteratively reweighted least squares algorithm that includes model regularization and Huber weighting. Data error covariance matrices are implemented, including both the latitude dependence of data error variances and covariances between the vector field components due to unmodelled sources. Results show good consistency with the field structures obtained in the CHAOS-4 and MF7 models using more conventional spherical harmonic based approaches. Advantages of the equivalent source method include its local nature, allowing e.g. for regional grid refinement, and the ease of transforming to spherical harmonics when needed. Future applications will make use of Swarm data in combination with high resolution aeromagnetic measurements.

AB - We present a new technique for modelling the global lithospheric magnetic field at Earth's surface based on the estimation of equivalent potential field sources. As a demonstration we show an application to magnetic field measurements made by the CHAMP satellite during the period 2009-2010 when it was at its lowest altitude and solar activity was also remarkably quiet. Both scalar and three component vector field data are utilized. Estimates of core and large-scale magnetospheric sources are removed from the measurements using the CHAOS-4 model. Quiet-time and night-side data selection criteria are also employed to minimize the influence of the ionospheric field. The model for the remaining lithospheric magnetic field consists of magnetic point sources (monopoles) arranged in an icosahedron grid. The corresponding source values are estimated using an iteratively reweighted least squares algorithm that includes model regularization and Huber weighting. Data error covariance matrices are implemented, including both the latitude dependence of data error variances and covariances between the vector field components due to unmodelled sources. Results show good consistency with the field structures obtained in the CHAOS-4 and MF7 models using more conventional spherical harmonic based approaches. Advantages of the equivalent source method include its local nature, allowing e.g. for regional grid refinement, and the ease of transforming to spherical harmonics when needed. Future applications will make use of Swarm data in combination with high resolution aeromagnetic measurements.

M3 - Conference abstract in journal

VL - 16

JO - Geophysical Research Abstracts

JF - Geophysical Research Abstracts

SN - 1607-7962

M1 - EGU2014-6673

ER -