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On the frequency spectra of the core magnetic field Gauss coefficients
- From monthly mean observatory data spanning 1957-2014, geomagnetic field secular variation values were calculated by annual differences. Estimates of the spherical harmonic Gauss coefficients of the core field secular variation were then derived by applying a correlation based modelling. Finally, a Fourier transform was applied to the time series of the Gauss coefficients. This process led to reliable temporal spectra of the Gauss coefficients up to spherical harmonic degree 5 or 6, and down to periods as short as 1 or 2 years depending on the coefficient. We observed that a k(-2) slope, where k is the frequency, is an acceptable approximation for these spectra, with possibly an exception for the dipole field. The monthly estimates of the core field secular variation at the observatory sites also show that large and rapid variations of the latter happen. This is an indication that geomagnetic jerks are frequent phenomena and that significant secular variation signals at short time scales - i.e. less than 2 years, could still beFrom monthly mean observatory data spanning 1957-2014, geomagnetic field secular variation values were calculated by annual differences. Estimates of the spherical harmonic Gauss coefficients of the core field secular variation were then derived by applying a correlation based modelling. Finally, a Fourier transform was applied to the time series of the Gauss coefficients. This process led to reliable temporal spectra of the Gauss coefficients up to spherical harmonic degree 5 or 6, and down to periods as short as 1 or 2 years depending on the coefficient. We observed that a k(-2) slope, where k is the frequency, is an acceptable approximation for these spectra, with possibly an exception for the dipole field. The monthly estimates of the core field secular variation at the observatory sites also show that large and rapid variations of the latter happen. This is an indication that geomagnetic jerks are frequent phenomena and that significant secular variation signals at short time scales - i.e. less than 2 years, could still be extracted from data to reveal an unexplored part of the core dynamics.…
Verfasserangaben: | Vincent LesurORCiD, Ingo WardinskiORCiD, Julien BärenzungORCiD, Matthias HolschneiderORCiDGND |
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DOI: | https://doi.org/10.1016/j.pepi.2017.05.017 |
ISSN: | 0031-9201 |
ISSN: | 1872-7395 |
Titel des übergeordneten Werks (Englisch): | Physics of the earth and planetary interiors |
Verlag: | Elsevier |
Verlagsort: | Amsterdam |
Publikationstyp: | Wissenschaftlicher Artikel |
Sprache: | Englisch |
Datum der Erstveröffentlichung: | 26.05.2017 |
Erscheinungsjahr: | 2017 |
Datum der Freischaltung: | 17.01.2022 |
Freies Schlagwort / Tag: | Core field; Correlation based modelling; Geomagnetic jerks; Geomagnetism; Secular variation rate of change |
Band: | 276 |
Seitenanzahl: | 14 |
Erste Seite: | 145 |
Letzte Seite: | 158 |
Fördernde Institution: | DFGGerman Research Foundation (DFG) [SPP1788]; Centre National des |
Organisationseinheiten: | Mathematisch-Naturwissenschaftliche Fakultät / Institut für Mathematik |
DDC-Klassifikation: | 5 Naturwissenschaften und Mathematik / 51 Mathematik / 510 Mathematik |
Peer Review: | Referiert |