IGRF candidate models at times of rapid changes in core field acceleration

Research areas:

• Intérieurs planétaires (2011 - 2016)

Year:

2010

Authors:

• Erwan Thébault
• Stefan Maus
• Arnaud Chulliat
• Gauthier Hulot
• Benoit Langlais
• Aude Chambodut
• Michel Menvielle

Journal:

Earth Planets Space

Volume:

62

Pages:

753-763

BibTex:

@article{theb2010eps, author = "Erwan Th{\'e}bault and Stefan Maus and Arnaud Chulliat and Gauthier Hulot and Benoit Langlais and Aude Chambodut and Michel Menvielle", abstract = "We submit three candidate models following the call for IGRF-11. We apply a simple modeling approach in spherical harmonics based on a quadratic Taylor expansion for the internal field time variations. We use the Dst magnetic index as a proxy for the external field variations. In order to compensate for the limitations incurred by such a conventional approach, we focus on the optimal selection of satellite data in space and time. We also show that some a priori knowledge about the core field state helps us to avoid the pitfall encountered in the case of rapid changes of core field accelerations. Indeed, various acceleration events of relevance for the IGRF 11th occurred between 2003 and 2010, one of them being a geomagnetic jerk. They could entail disagreements between IGRF candidate models for the secular variation (SV) if data prior to 2008 are used. Our SV and main field (MF) candidate models have a root mean square uncertainty less than 6 nT/yr and 8 nT, respectively, with respect to the modeled magnetic field contributions. These values correspond to the intrinsic error associated with truncating SV and MF models to spherical harmonic degree 8 and 13, respectively, as requested for IGRF models.", doi = "10.5047/eps.2010.05.004", extra = "PICL", journal = "Earth Planets Space", pages = "753-763", title = "{IGRF} candidate models at times of rapid changes in core field acceleration", volume = "62", year = "2010", }

Abstract:

We submit three candidate models following the call
for IGRF-11. We apply a simple modeling approach in
spherical harmonics based on a quadratic Taylor
expansion for the internal field time variations. We
use the Dst magnetic index as a proxy for the
external field variations. In order to compensate
for the limitations incurred by such a conventional
approach, we focus on the optimal selection of
satellite data in space and time. We also show that
some a priori knowledge about the core field state
helps us to avoid the pitfall encountered in the
case of rapid changes of core field
accelerations. Indeed, various acceleration events
of relevance for the IGRF 11th occurred between 2003
and 2010, one of them being a geomagnetic jerk. They
could entail disagreements between IGRF candidate
models for the secular variation (SV) if data prior
to 2008 are used. Our SV and main field (MF)
candidate models have a root mean square uncertainty
less than 6 nT/yr and 8 nT, respectively, with
respect to the modeled magnetic field
contributions. These values correspond to the
intrinsic error associated with truncating SV and MF
models to spherical harmonic degree 8 and 13,
respectively, as requested for IGRF models.