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  • Article
  • Open Access

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

Earth, Planets and Space200658:BF03351982

  • Received: 10 June 2005
  • Accepted: 6 February 2006
  • Published:


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.

Key words

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