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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 18, issue 6
Ann. Geophys., 18, 653-665, 2000
https://doi.org/10.1007/s00585-000-0653-2
© European Geosciences Union 2000
Ann. Geophys., 18, 653-665, 2000
https://doi.org/10.1007/s00585-000-0653-2
© European Geosciences Union 2000

  30 Jun 2000

30 Jun 2000

Geomagnetic control of the foF2 long-term trends

A. V. Mikhailov1 and D. Marin2 A. V. Mikhailov and D. Marin
  • 1Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Troitsk, Moscow Region 142092, Russia
  • 2National Institute of Aerospace Technology, El Arenosillo, 21130 Mazagon-Moguer (Huelva), Spain
  • Correspondence to: A. V. Mikhailov
  • e-mail: avm71@orc.ru

Abstract. Further development of the method proposed by Danilov and Mikhailov is presented. The method is applied to reveal the foF2 long-term trends on 30 Northern Hemisphere ionosonde stations. Most of them show significant foF2 trends. A pronounced dependence of trend magnitude on geomagnetic (invariant) latitude is confirmed. Periods of negative/positive foF2 trends corresponding to the periods of long-term increasing/decreasing geomagnetic activity are revealed for the first time. Pronounced diurnal variations of the foF2 trend magnitude are found. Strong positive foF2 trends in the post-midnight-early-morning LT sector and strong negative trends during daytime hours are found on the sub-auroral stations for the period with increasing geomagnetic activity. On the contrary middle and lower latitude stations demonstrate negative trends in the early-morning LT sector and small negative or positive trends during daytime hours for the same period. All the morphological features revealed of the foF2 trends may be explained in the framework of contemporary F2-region storm mechanisms. This newly proposed F2-layer geomagnetic storm concept casts serious doubts on the hypothesis relating the F2-layer parameter long-term trends to the thermosphere cooling due to the greenhouse effect.

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

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