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Solid Earth An interactive open-access journal of the European Geosciences Union

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© Author(s) 2017. This work is distributed under
the Creative Commons Attribution 4.0 License.
Research article
08 Nov 2017
Review status
This discussion paper is a preprint. A revision of the manuscript is under review for the journal Solid Earth (SE).
Geomagnetic field declination: from decadal to centennial scales
Venera Dobrica1, Crisan Demetrescu1, and Mioara Mandea2 1Institute of Geodynamics, Romanian Academy, Bucharest, Romania
2Centre National d’Etudes Spatiales, Paris, France
Abstract. Declination annual means time-series longer than a century provided by 24 geomagnetic observatories world-wide, together with 5 Western European reconstructed declination series over the last four centuries have been analyzed in terms of frequency constituents of the secular variation at inter-decadal and sub-centennial time-scales of 20–35 and, respectively, 70–90 years. Observatory and reconstructed time-series have been processed by several types of filtering, namely Hodrick-Prescott, running averages, and Butterworth. The Hodrick-Prescott filtering allows to separate a quasi-oscillation at decadal time scale, supposed to be related to external variations and called ’11-year constituent’, from a long-term trend. The latter has been decomposed in two other oscillations, called ‘inter-decadal’ and ‘sub-centennial’ constituents by applying a Butterworth filtering with cutoffs at 30 and 73 years, respectively. The analysis shows that the generally accepted geomagnetic jerks occur around extrema in the time derivative of the trend and coincide with extrema in the time derivative of the 11-year constituent. The sub-centennial constituent is traced back to 1600, in the five 400-year long time-series, and shows to be a major constituent of the secular variation, geomagnetic jerks included.

Citation: Dobrica, V., Demetrescu, C., and Mandea, M.: Geomagnetic field declination: from decadal to centennial scales, Solid Earth Discuss.,, in review, 2017.
Venera Dobrica et al.
Venera Dobrica et al.
Venera Dobrica et al.


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