DTU candidate field models for IGRF-12 and the CHAOS-5 geomagnetic field model

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Abstract

We present DTU’s candidate field models for IGRF-12 and the parent field model from which they were derived,CHAOS-5. Ten months of magnetic field observations from ESA’s Swarm mission, together with up-to-date ground observatory monthly means, were used to supplement the data sources previously used to construct CHAOS-4. Theinternal field part of CHAOS-5, from which our IGRF-12 candidate models were extracted, is time-dependent up to spherical harmonic degree 20 and involves sixth-order splines with a 0.5 year knot spacing. In CHAOS-5, comparedwith CHAOS-4, we update only the low-degree internal field model (degrees 1 to 24) and the associated external field model. The high-degree internal field (degrees 25 to 90) is taken from the same model CHAOS-4h, based onlow-altitude CHAMP data, which was used in CHAOS-4.We find that CHAOS-5 is able to consistently fit magnetic field data from six independent low Earth orbit satellites:Ørsted, CHAMP, SAC-C and the three Swarm satellites (A, B and C). It also adequately describes the secular variationmeasured at ground observatories. CHAOS-5 thus contributes to an initial validation of the quality of the Swarmmagnetic data, in particular demonstrating that Huber weighted rms model residuals to Swarm vector field data arelower than those to Ørsted and CHAMP vector data (when either one or two star cameras were operating). CHAOS-5shows three pulses of secular acceleration at the core surface over the past decade; the 2006 and 2009 pulses have previously been documented, but the 2013 pulse has only recently been identified. The spatial signature of the 2013pulse at the core surface, under the Atlantic sector where it is strongest, is well correlated with the 2006 pulse, but anti-correlated with the 2009 pulse.
Original languageEnglish
JournalEarth, Planets and Space
Volume67
Issue number114
Number of pages17
ISSN1343-8832
DOIs
Publication statusPublished - 2015

Bibliographical note

© 2015 Finlay et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

Keywords

  • Geomagnetism
  • Field modelling
  • IGRF
  • Swarm

Cite this

@article{04a7d23ca77c4e588c5c9efcd772851a,
title = "DTU candidate field models for IGRF-12 and the CHAOS-5 geomagnetic field model",
abstract = "We present DTU’s candidate field models for IGRF-12 and the parent field model from which they were derived,CHAOS-5. Ten months of magnetic field observations from ESA’s Swarm mission, together with up-to-date ground observatory monthly means, were used to supplement the data sources previously used to construct CHAOS-4. Theinternal field part of CHAOS-5, from which our IGRF-12 candidate models were extracted, is time-dependent up to spherical harmonic degree 20 and involves sixth-order splines with a 0.5 year knot spacing. In CHAOS-5, comparedwith CHAOS-4, we update only the low-degree internal field model (degrees 1 to 24) and the associated external field model. The high-degree internal field (degrees 25 to 90) is taken from the same model CHAOS-4h, based onlow-altitude CHAMP data, which was used in CHAOS-4.We find that CHAOS-5 is able to consistently fit magnetic field data from six independent low Earth orbit satellites:{\O}rsted, CHAMP, SAC-C and the three Swarm satellites (A, B and C). It also adequately describes the secular variationmeasured at ground observatories. CHAOS-5 thus contributes to an initial validation of the quality of the Swarmmagnetic data, in particular demonstrating that Huber weighted rms model residuals to Swarm vector field data arelower than those to {\O}rsted and CHAMP vector data (when either one or two star cameras were operating). CHAOS-5shows three pulses of secular acceleration at the core surface over the past decade; the 2006 and 2009 pulses have previously been documented, but the 2013 pulse has only recently been identified. The spatial signature of the 2013pulse at the core surface, under the Atlantic sector where it is strongest, is well correlated with the 2006 pulse, but anti-correlated with the 2009 pulse.",
keywords = "Geomagnetism, Field modelling, IGRF, Swarm",
author = "Chris Finlay and Nils Olsen and Lars T{\o}ffner-Clausen",
note = "{\circledC} 2015 Finlay et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.",
year = "2015",
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language = "English",
volume = "67",
journal = "Earth, Planets and Space",
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DTU candidate field models for IGRF-12 and the CHAOS-5 geomagnetic field model. / Finlay, Chris; Olsen, Nils; Tøffner-Clausen, Lars.

In: Earth, Planets and Space, Vol. 67, No. 114, 2015.

Research output: Contribution to journalJournal articleResearchpeer-review

TY - JOUR

T1 - DTU candidate field models for IGRF-12 and the CHAOS-5 geomagnetic field model

AU - Finlay, Chris

AU - Olsen, Nils

AU - Tøffner-Clausen, Lars

N1 - © 2015 Finlay et al. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License http://creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made.

PY - 2015

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N2 - We present DTU’s candidate field models for IGRF-12 and the parent field model from which they were derived,CHAOS-5. Ten months of magnetic field observations from ESA’s Swarm mission, together with up-to-date ground observatory monthly means, were used to supplement the data sources previously used to construct CHAOS-4. Theinternal field part of CHAOS-5, from which our IGRF-12 candidate models were extracted, is time-dependent up to spherical harmonic degree 20 and involves sixth-order splines with a 0.5 year knot spacing. In CHAOS-5, comparedwith CHAOS-4, we update only the low-degree internal field model (degrees 1 to 24) and the associated external field model. The high-degree internal field (degrees 25 to 90) is taken from the same model CHAOS-4h, based onlow-altitude CHAMP data, which was used in CHAOS-4.We find that CHAOS-5 is able to consistently fit magnetic field data from six independent low Earth orbit satellites:Ørsted, CHAMP, SAC-C and the three Swarm satellites (A, B and C). It also adequately describes the secular variationmeasured at ground observatories. CHAOS-5 thus contributes to an initial validation of the quality of the Swarmmagnetic data, in particular demonstrating that Huber weighted rms model residuals to Swarm vector field data arelower than those to Ørsted and CHAMP vector data (when either one or two star cameras were operating). CHAOS-5shows three pulses of secular acceleration at the core surface over the past decade; the 2006 and 2009 pulses have previously been documented, but the 2013 pulse has only recently been identified. The spatial signature of the 2013pulse at the core surface, under the Atlantic sector where it is strongest, is well correlated with the 2006 pulse, but anti-correlated with the 2009 pulse.

AB - We present DTU’s candidate field models for IGRF-12 and the parent field model from which they were derived,CHAOS-5. Ten months of magnetic field observations from ESA’s Swarm mission, together with up-to-date ground observatory monthly means, were used to supplement the data sources previously used to construct CHAOS-4. Theinternal field part of CHAOS-5, from which our IGRF-12 candidate models were extracted, is time-dependent up to spherical harmonic degree 20 and involves sixth-order splines with a 0.5 year knot spacing. In CHAOS-5, comparedwith CHAOS-4, we update only the low-degree internal field model (degrees 1 to 24) and the associated external field model. The high-degree internal field (degrees 25 to 90) is taken from the same model CHAOS-4h, based onlow-altitude CHAMP data, which was used in CHAOS-4.We find that CHAOS-5 is able to consistently fit magnetic field data from six independent low Earth orbit satellites:Ørsted, CHAMP, SAC-C and the three Swarm satellites (A, B and C). It also adequately describes the secular variationmeasured at ground observatories. CHAOS-5 thus contributes to an initial validation of the quality of the Swarmmagnetic data, in particular demonstrating that Huber weighted rms model residuals to Swarm vector field data arelower than those to Ørsted and CHAMP vector data (when either one or two star cameras were operating). CHAOS-5shows three pulses of secular acceleration at the core surface over the past decade; the 2006 and 2009 pulses have previously been documented, but the 2013 pulse has only recently been identified. The spatial signature of the 2013pulse at the core surface, under the Atlantic sector where it is strongest, is well correlated with the 2006 pulse, but anti-correlated with the 2009 pulse.

KW - Geomagnetism

KW - Field modelling

KW - IGRF

KW - Swarm

U2 - 10.1186/s40623-015-0274-3

DO - 10.1186/s40623-015-0274-3

M3 - Journal article

VL - 67

JO - Earth, Planets and Space

JF - Earth, Planets and Space

SN - 1343-8832

IS - 114

ER -