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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 20, issue 10
Ann. Geophys., 20, 1663–1675, 2002
https://doi.org/10.5194/angeo-20-1663-2002
© Author(s) 2002. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 20, 1663–1675, 2002
https://doi.org/10.5194/angeo-20-1663-2002
© Author(s) 2002. This work is distributed under
the Creative Commons Attribution 3.0 License.

  31 Oct 2002

31 Oct 2002

A revised approach to the ƒoF2 long-term trends analysis

A. V. Mikhailov1, D. Marin2, T. Yu. Leschinskaya1, and M. Herraiz3 A. V. Mikhailov et al.
  • 1Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Troitsk, Moscow Region 142190, Russia
  • 2Atmospheric Sounding Station “El Arenosillo", INTA, Spain
  • 3Faculty of Physics, Complutense University, Spain
  • Correspondence to: A. V. Mikhailov (avm71@orc.ru)

Abstract. A new approach to extract foF2 long-term trends, which are free to a great extent from solar and geomagnetic activity effects, has been proposed. These trends are insensitive to the phase (increasing/decreasing) of geomagnetic activity, with long-term variations being small and insignificant for such relatively short time periods. A small but significant residual foF2 trend, with the slope Kr = - 2.2 × 10-4 per year, was obtained over a 55-year period (the longest avail-able) of observations at Slough. Such small trends have no practical importance. On the other hand, negative (although insignificant) residual trends obtained at 10 ionosonde stations for shorter periods (31 years) may be considered as a manifestation of a very long-term geomagnetic activity increase which did take place during the 20th century. All of the revealed foF2 long-term variations (trends) are shown to have a natural origin related to long-term variations in solar and geomagnetic activity. There is no indication of any manmade foF2 trends. 

Key words. Ionosphere (ionosphere-atmosphere interactions, ionospheric disturbances)

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