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Ann. Geophys., 20, 1795-1806, 2002
www.ann-geophys.net/20/1795/2002/
© European Geosciences Union 2002
Global morphology of night-time NmF2 enhancements
A. F. Farelo1, M. Herraiz1, and A. V. Mikhailov2
1Department of Geophysics and Meteorology, Faculty of Physics, Complutense University, E-28040 Madrid, Spain
2Institute of Terrestrial Magnetism, Ionosphere and Radio Wave Propagation, Russian Academy of Sciences, Troitsk, Moscow Region, Russia
Correspondence to: M. Herraiz (mherraiz@fis.ucm.es)
Abstract. An overall statistical
study of night-time enhancements of NmF2 has been carried out. All
available foF2 observations since 1955 at 53 ionosonde stations
distributed worldwide in the latitude range fgeom
= 15° - 60° were used in the analysis. More than 200 000 station-nights of
data were analysed. This large data base allowed us to study seasonal, solar
cycle and spatial variations of the NmF2 nighttime enhancements. Both
pre-midnight and post-midnight NmF2 peaks demonstrate distinct
variations with geophysical conditions, indicating different physical
mechanisms responsible for their formation.
Key words. Ionosphere (mid-latitude ionosphere,
ionosphere-magnetosphere interactions) Radio science (ionospheric
physics)
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