The BGS magnetic field candidate models for the 12th generation IGRF

Hamilton, Brian; Ridley, Victoria A.; Beggan, Ciaran D.; Macmillan, Susan. 2015 The BGS magnetic field candidate models for the 12th generation IGRF. Earth, Planets and Space, 67 (69). 10.1186/s40623-015-0227-x

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Official URL: http://www.earth-planets-space.com/content/67/1/69

Abstract/Summary

We describe the candidate models submitted by the British Geological Survey for the 12th generation International Geomagnetic Reference Field. These models are extracted from a spherical harmonic ‘parent model’ derived from vector and scalar magnetic field data from satellite and observatory sources. These data cover the period 2009.0 to 2014.7 and include measurements from the recently launched European Space Agency (ESA) Swarm satellite constellation. The parent model’s internal field time dependence for degrees 1 to 13 is represented by order 6 B-splines with knots at yearly intervals. The parent model’s degree 1 external field time dependence is described by periodic functions for the annual and semi-annual signals and by dependence on the 20-min Vector Magnetic Disturbance index. Signals induced by these external fields are also parameterized. Satellite data are weighted by spatial density and by two different noise estimators: (a) by standard deviation along segments of the satellite track and (b) a larger-scale noise estimator defined in terms of a measure of vector activity at the geographically closest magnetic observatories to the sample point. Forecasting of the magnetic field secular variation beyond the span of data is by advection of the main field using core surface flows.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	10.1186/s40623-015-0227-x
ISSN:	1343-8832
NORA Subject Terms:	Earth Sciences
Date made live:	06 Jul 2015 12:57 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/510947

Item Type:

Publication - Article

Digital Object Identifier (DOI):

10.1186/s40623-015-0227-x

ISSN:

1343-8832

NORA Subject Terms:

Earth Sciences

Date made live:

06 Jul 2015 12:57 +0 (UTC)

URI:

https://nora.nerc.ac.uk/id/eprint/510947