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  • Article
  • Open Access

The irregular variations of the external geomagnetic field from Intermagnet data

  • 1Email author,
  • 1,
  • 1 and
  • 1
Earth, Planets and Space201455:BF03351746

  • Received: 15 April 2002
  • Accepted: 31 March 2003
  • Published:


The Intermagnet program publishes each year a cd-rom containing homogeneous series from a number of magnetic observatories (76 in 1999). These series are definitive one-minute values of the three components of the geomagnetic field. We transform these series using a simple nonlinear analysis tool able to characterize the activity of a signal, and we obtain a remarkably simple activity field, whose space and time variables separate over a large part of the Earth. The time function is almost identical for all observatories, and might be interpreted as an activity index. The—almost stationary—field geometry exhibits a dipole-like structure everywhere except in high latitudes.

Key words

  • Geomagnetic field
  • irregular variations
  • absolute derivative