TY  - JOUR
A1  - Lesur, Vincent
A1  - Wardinski, Ingo
A1  - Bärenzung, Julien
A1  - Holschneider, Matthias
T1  - On the frequency spectra of the core magnetic field Gauss coefficients
JF  - Physics of the earth and planetary interiors
N2  - 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 be extracted from data to reveal an unexplored part of the core dynamics.
KW  - Geomagnetism
KW  - Core field
KW  - Secular variation rate of change
KW  - Geomagnetic jerks
KW  - Correlation based modelling
Y1  - 2017
U6  - https://doi.org/10.1016/j.pepi.2017.05.017
SN  - 0031-9201
SN  - 1872-7395
VL  - 276
SP  - 145
EP  - 158
PB  - Elsevier
CY  - Amsterdam
ER  -