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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 25, issue 7
Ann. Geophys., 25, 1465-1469, 2007
https://doi.org/10.5194/angeo-25-1465-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 25, 1465-1469, 2007
https://doi.org/10.5194/angeo-25-1465-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.

  30 Jul 2007

30 Jul 2007

ap-index solar wind driving function and its semiannual variations

A. A. Petrukovich and M. Y. Zakharov A. A. Petrukovich and M. Y. Zakharov
  • Space Research Institute, 84/32 Profsoyuznaya st., Moscow, 117997, Russia

Abstract. Semiannual variation of geomagnetic activity and ap-index in particular is supposed to consist of heliospheric factor (axial hypothesis and Russell-McPherron effect) and magnetospheric/ionospheric factor (equinoctical hypothesis). In our investigation we express ap-index as a magnetospheric response function to solar wind and IMF input. Seasonal variation in ap-index on average (1963–2003) is ~4 nT and consists of ~2.1–2.3 nT of magnetospheric/ionospheric part, 0.6–1.3 nT of heliospheric part (including 0.2–0.3 nT of R-M effect), 0.1–0.4 nT is due to the non-linear term. 90% confidence range of all estimates is ~0.1–0.25 nT. While autumn/spring magnetospheric response functions are almost identical, there is substantial difference between winter and summer functions. The increase of solar wind input in autumn and spring is also different by a factor of two.

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