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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 17, issue 9
Ann. Geophys., 17, 1239-1243, 1999
https://doi.org/10.1007/s00585-999-1239-2
© European Geosciences Union 1999
Ann. Geophys., 17, 1239-1243, 1999
https://doi.org/10.1007/s00585-999-1239-2
© European Geosciences Union 1999

  30 Sep 1999

30 Sep 1999

Letter to the Editor: Spatial and seasonal variations of the foF2 long-term trends

A. D. Danilov1 and A. V. Mikhailov2 A. D. Danilov and A. V. Mikhailov
  • 1Institute of Applied Geophysics, Rostokinskaya 9, Moscow 129128, Russia
  • 2Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Troitsk, Moscow Region 142092, Russia
  • Correspondence to: A. D. Danilov, e-mail: avm71@orc.rue

Abstract. Using a method suggested by the authors earlier, the long-term trends of the F2-layer critical frequency, foF2 are derived for a set of ionospheric stations with a wide latitudinal and longitudinal coverage. All the trends are found to be negative. A pronounced dependence on geomagnetic latitude is found, the trend magnitude increasing with the latter. No globe scale longitudinal effect in trends is detected. For the majority of the stations there is also a pronounced seasonal effect, the trend magnitude being higher in summer than in winter.

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

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