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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 21, issue 5
Ann. Geophys., 21, 1167–1176, 2003
https://doi.org/10.5194/angeo-21-1167-2003
© Author(s) 2003. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 21, 1167–1176, 2003
https://doi.org/10.5194/angeo-21-1167-2003
© Author(s) 2003. This work is distributed under
the Creative Commons Attribution 3.0 License.

  31 May 2003

31 May 2003

Long-term trends of foF2 independent of geomagnetic activity

A. D. Danilov A. D. Danilov
  • Institute of Applied Geophysics, Rostokinskaya 9, Moscow 129 128, Russia

Abstract. A detailed analysis of the foF2 data at a series of ionospheric stations is performed to reveal long-term trends independent of the long-term changes in geomagnetic activity during the recent decades (nongeomagnetic trends). The method developed by the author and published earlier is used. It is found that the results for 21 out of 23 stations considered agree well and give a relative nongeomagnetic trend of -0.0012 per year (or an absolute nongeomagnetic trend of about -0.012 MHz per year) for the period between 1958 and the mid-nineties. The trends derived show no dependence on geomagnetic latitude or local time, a fact confirming their independence of geomagnetic activity. The consideration of the earlier period (1948–1985) for a few stations for which the corresponding data are available provides significantly lower foF2 trends, the difference between the later and earlier periods being a factor of 1.6. This is a strong argument in favor of an anthropogenic nature of the trends derived.

Key words. Ionosphere (ionosphere-atmosphere interactions; ionospheric disturbances; mid-latitude ionosphere)

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