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The irregular variations of the external geomagnetic field from Intermagnet data


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.


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Correspondence to Eric Bellanger.

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Bellanger, E., Anad, F., Le Mouël, JL. et al. The irregular variations of the external geomagnetic field from Intermagnet data. Earth Planet Sp 55, 173–181 (2003).

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Key words

  • Geomagnetic field
  • irregular variations
  • absolute derivative