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  • Letter
  • Open Access

Local time variation of the amplitude of geomagnetic sudden commencements (SC) and SC-associated polar cap potential

Earth, Planets and Space200961:BF03353154

  • Received: 11 February 2009
  • Accepted: 21 March 2009
  • Published:


Local time (LT) variations of the averaged H-component amplitude of geomagnetic sudden commencements (SCs) observed at Memambetsu (geomagnetic latitude 35.4°) are derived separately for the summer and winter season. The amplitude was found to be higher at nighttime than daytime in both seasons, and the LT variations showed a good agreement with calculated LT variations of the resultant magnetic field due to a pair of fieldaligned currents (FACs) and ionospheric currents produced by the FACs. The DL- and DP-component of the disturbance field of SC can be separated based on a comparison of the observed and calculated LT variations. A method is introduced by which we can estimate the potential voltage difference associated with the FACs in the polar cap.

Key words

  • Geomagnetic sudden commencement (SC)
  • LT variation
  • field-aligned current
  • ionospheric current
  • interplanetary shock