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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 21, issue 3
Ann. Geophys., 21, 751–760, 2003
https://doi.org/10.5194/angeo-21-751-2003
© Author(s) 2003. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 21, 751–760, 2003
https://doi.org/10.5194/angeo-21-751-2003
© Author(s) 2003. This work is distributed under
the Creative Commons Attribution 3.0 License.

  31 Mar 2003

31 Mar 2003

Long-term trends of foE and geomagnetic activity variations

A. V. Mikhailov1 and B. A. de la Morena2 A. V. Mikhailov and B. A. de la Morena
  • 1Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Troitsk, Moscow Region 142190, Russia
  • 2National Institute of Aerospace Technology, Atmospheric Sounding Station El Arenosillo, 21130 Mazagon-Moguerssia (Huelva), Spain

Abstract. A relationship between foE trends and geomagnetic activity long-term variations has been revealed for the first time. By analogy with earlier obtained results on the foF2 trends it is possible to speak about the geomagnetic control of the foE long-term trends as well. Periods of increasing geomagnetic activity correspond to negative foE trends, while these trends are positive for the decreasing phase of geomagnetic activity. This "natural" relationship breaks down around 1970 (on some stations later) when pronounced positive foE trends have appeared on most of the stations considered. The dependence of foE trends on geomagnetic activity can be related with nitric oxide variations at the E-layer heights. The positive foE trends that appeared after the "break down" effect may also be explained by the [NO] decrease which is not related to geomagnetic activity variations. But negative trends or irregular foE variations on some stations for the same time period require some different mechanism. Chemical pollution of the lower thermosphere due to the anthropogenic activity may be responsible for such abnormal foE behavior after the end of the 1960s.

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

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