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Volume 58 Supplement 6

Special Issue: Ground Magnetic Observations: New technologies and the role in understanding the Earth System

Annual and semi-annual variations of the geomagnetic field components analysed by the multi-taper method


Monthly means of three geomagnetic components (X-northern, Y-eastern and Z-vertical downward) from 154 observatories over the interval 1960-2002 have been analysed to determine the annual and semi-annual variations. The method applied is a multi-taper analysis, which gives a robust estimate of the power spectral density of the temporal variation of the field components. The main objective is to investigate the geographic dependence of the annual and semi-annual variations. Surprisingly, these variations in the vertical downward component are not homogeneously distributed all over the globe, having mainly a longitudinal dependency. The results of the analysis are briefly discussed with regard to possible mechanisms responsible for these variations and to mantle conductivity.


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Correspondence to I. Wardinski.

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Wardinski, I., Mandea, M. Annual and semi-annual variations of the geomagnetic field components analysed by the multi-taper method. Earth Planet Sp 58, 785–791 (2006).

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Key words

  • Geomagnetic field variation
  • multi-taper method
  • time series analysis