The CHAOS-4 Geomagnetic Field Model

Nils Olsen, Chris Finlay, H. Lühr, T. J. Sabaka, I. Michaelis, J. Rauberg, Lars Tøffner-Clausen

Research output: Contribution to conferenceConference abstract for conferenceResearchpeer-review

Abstract

We present CHAOS-4, a new version in the CHAOS model series, which aims at describing the Earth's magnetic field with high spatial resolution (terms up to spherical degree n=90 for the crustal field, and up to n=16 for the time-varying core field are robustly determined) and high temporal resolution (allowing for investigations of sub-annual core field changes). More than 14 years of data from the satellites Ørsted (March 1999 to June 2013), CHAMP (July 2000 to September 2010) and SAC-C (2000 to 2004), augmented with ground observatory revised monthly mean values (1997 to 2013) have been used for this model. Maximum spherical harmonic degree of the static (crustal) field is n=100. The core field time changes are expressed by spherical harmonic expansion coefficients up to n=20, described by order 6 splines (with 6-month knot spacing) spanning the time interval 1997.0 to 2013.5. The third time derivative of the squared magnetic field intensity is regularized at the core-mantle boundary. No spatial regularization is applied for the core field, but the high-degree crustal field is regularized for n>85. As part of the modeling effort we co-estimate a model of the large-scale magnetospheric field (with expansions in the GSM and SM coordinate system up to degree n = 2 and parameterization of the time dependence using the decomposition of Dst into external (Est) and induced (Ist) parts) and perform an in-flight alignment of the vector data (co-estimation of the Euler describing the rotation between the coordinate systems of the vector magnetometer and of the star sensor providing attitude information). The final CHAOS-4 model is derived by merging two sub-models: its low-degree part has been obtained using similar model parameterization and data sets as used for previous CHAOS models (but of course including newer satellite observations), while its high-degree crustal field part is solely determined from low-altitude CHAMP satellite observations between January 2009 and September 2010.
Original languageEnglish
Publication date2013
Number of pages1
Publication statusPublished - 2013
EventAGU Fall Meeting 2013 - San Francisco, United States
Duration: 9 Dec 201313 Dec 2013

Conference

ConferenceAGU Fall Meeting 2013
CountryUnited States
CitySan Francisco
Period09/12/201313/12/2013

Cite this

Olsen, N., Finlay, C., Lühr, H., Sabaka, T. J., Michaelis, I., Rauberg, J., & Tøffner-Clausen, L. (2013). The CHAOS-4 Geomagnetic Field Model. Abstract from AGU Fall Meeting 2013, San Francisco, United States.
Olsen, Nils ; Finlay, Chris ; Lühr, H. ; Sabaka, T. J. ; Michaelis, I. ; Rauberg, J. ; Tøffner-Clausen, Lars. / The CHAOS-4 Geomagnetic Field Model. Abstract from AGU Fall Meeting 2013, San Francisco, United States.1 p.
@conference{e3a17c8742ca45109de1171581e24132,
title = "The CHAOS-4 Geomagnetic Field Model",
abstract = "We present CHAOS-4, a new version in the CHAOS model series, which aims at describing the Earth's magnetic field with high spatial resolution (terms up to spherical degree n=90 for the crustal field, and up to n=16 for the time-varying core field are robustly determined) and high temporal resolution (allowing for investigations of sub-annual core field changes). More than 14 years of data from the satellites {\O}rsted (March 1999 to June 2013), CHAMP (July 2000 to September 2010) and SAC-C (2000 to 2004), augmented with ground observatory revised monthly mean values (1997 to 2013) have been used for this model. Maximum spherical harmonic degree of the static (crustal) field is n=100. The core field time changes are expressed by spherical harmonic expansion coefficients up to n=20, described by order 6 splines (with 6-month knot spacing) spanning the time interval 1997.0 to 2013.5. The third time derivative of the squared magnetic field intensity is regularized at the core-mantle boundary. No spatial regularization is applied for the core field, but the high-degree crustal field is regularized for n>85. As part of the modeling effort we co-estimate a model of the large-scale magnetospheric field (with expansions in the GSM and SM coordinate system up to degree n = 2 and parameterization of the time dependence using the decomposition of Dst into external (Est) and induced (Ist) parts) and perform an in-flight alignment of the vector data (co-estimation of the Euler describing the rotation between the coordinate systems of the vector magnetometer and of the star sensor providing attitude information). The final CHAOS-4 model is derived by merging two sub-models: its low-degree part has been obtained using similar model parameterization and data sets as used for previous CHAOS models (but of course including newer satellite observations), while its high-degree crustal field part is solely determined from low-altitude CHAMP satellite observations between January 2009 and September 2010.",
author = "Nils Olsen and Chris Finlay and H. L{\"u}hr and Sabaka, {T. J.} and I. Michaelis and J. Rauberg and Lars T{\o}ffner-Clausen",
year = "2013",
language = "English",
note = "AGU Fall Meeting 2013 ; Conference date: 09-12-2013 Through 13-12-2013",

}

Olsen, N, Finlay, C, Lühr, H, Sabaka, TJ, Michaelis, I, Rauberg, J & Tøffner-Clausen, L 2013, 'The CHAOS-4 Geomagnetic Field Model', AGU Fall Meeting 2013, San Francisco, United States, 09/12/2013 - 13/12/2013.

The CHAOS-4 Geomagnetic Field Model. / Olsen, Nils; Finlay, Chris; Lühr, H.; Sabaka, T. J.; Michaelis, I.; Rauberg, J.; Tøffner-Clausen, Lars.

2013. Abstract from AGU Fall Meeting 2013, San Francisco, United States.

Research output: Contribution to conferenceConference abstract for conferenceResearchpeer-review

TY - ABST

T1 - The CHAOS-4 Geomagnetic Field Model

AU - Olsen, Nils

AU - Finlay, Chris

AU - Lühr, H.

AU - Sabaka, T. J.

AU - Michaelis, I.

AU - Rauberg, J.

AU - Tøffner-Clausen, Lars

PY - 2013

Y1 - 2013

N2 - We present CHAOS-4, a new version in the CHAOS model series, which aims at describing the Earth's magnetic field with high spatial resolution (terms up to spherical degree n=90 for the crustal field, and up to n=16 for the time-varying core field are robustly determined) and high temporal resolution (allowing for investigations of sub-annual core field changes). More than 14 years of data from the satellites Ørsted (March 1999 to June 2013), CHAMP (July 2000 to September 2010) and SAC-C (2000 to 2004), augmented with ground observatory revised monthly mean values (1997 to 2013) have been used for this model. Maximum spherical harmonic degree of the static (crustal) field is n=100. The core field time changes are expressed by spherical harmonic expansion coefficients up to n=20, described by order 6 splines (with 6-month knot spacing) spanning the time interval 1997.0 to 2013.5. The third time derivative of the squared magnetic field intensity is regularized at the core-mantle boundary. No spatial regularization is applied for the core field, but the high-degree crustal field is regularized for n>85. As part of the modeling effort we co-estimate a model of the large-scale magnetospheric field (with expansions in the GSM and SM coordinate system up to degree n = 2 and parameterization of the time dependence using the decomposition of Dst into external (Est) and induced (Ist) parts) and perform an in-flight alignment of the vector data (co-estimation of the Euler describing the rotation between the coordinate systems of the vector magnetometer and of the star sensor providing attitude information). The final CHAOS-4 model is derived by merging two sub-models: its low-degree part has been obtained using similar model parameterization and data sets as used for previous CHAOS models (but of course including newer satellite observations), while its high-degree crustal field part is solely determined from low-altitude CHAMP satellite observations between January 2009 and September 2010.

AB - We present CHAOS-4, a new version in the CHAOS model series, which aims at describing the Earth's magnetic field with high spatial resolution (terms up to spherical degree n=90 for the crustal field, and up to n=16 for the time-varying core field are robustly determined) and high temporal resolution (allowing for investigations of sub-annual core field changes). More than 14 years of data from the satellites Ørsted (March 1999 to June 2013), CHAMP (July 2000 to September 2010) and SAC-C (2000 to 2004), augmented with ground observatory revised monthly mean values (1997 to 2013) have been used for this model. Maximum spherical harmonic degree of the static (crustal) field is n=100. The core field time changes are expressed by spherical harmonic expansion coefficients up to n=20, described by order 6 splines (with 6-month knot spacing) spanning the time interval 1997.0 to 2013.5. The third time derivative of the squared magnetic field intensity is regularized at the core-mantle boundary. No spatial regularization is applied for the core field, but the high-degree crustal field is regularized for n>85. As part of the modeling effort we co-estimate a model of the large-scale magnetospheric field (with expansions in the GSM and SM coordinate system up to degree n = 2 and parameterization of the time dependence using the decomposition of Dst into external (Est) and induced (Ist) parts) and perform an in-flight alignment of the vector data (co-estimation of the Euler describing the rotation between the coordinate systems of the vector magnetometer and of the star sensor providing attitude information). The final CHAOS-4 model is derived by merging two sub-models: its low-degree part has been obtained using similar model parameterization and data sets as used for previous CHAOS models (but of course including newer satellite observations), while its high-degree crustal field part is solely determined from low-altitude CHAMP satellite observations between January 2009 and September 2010.

M3 - Conference abstract for conference

ER -

Olsen N, Finlay C, Lühr H, Sabaka TJ, Michaelis I, Rauberg J et al. The CHAOS-4 Geomagnetic Field Model. 2013. Abstract from AGU Fall Meeting 2013, San Francisco, United States.