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Ann. Geophys., 20, 1807-1819, 2002
www.ann-geophys.net/20/1807/2002/
© European Geosciences Union 2002
Variability in the maximum height of the ionospheric F2-layer over Millstone Hill (September 1998–March 2000); influence from below and above
D. Pancheva1,2, N. Mitchell2, R. R. Clark3, J. Drobjeva4,*, and J. Lastovicka4
1Physics Department, University of Wales, Aberystwyth, UK
2Department of Electronic & Electrical Engineering, University of Bath, Bath, UK
3Electrical and Computer Engineering Department, University of NH, USA
4Institute of Atmospheric Physics, Prague, Czech Republic
*present address: Institute of the Ionosphere, Almaty, Kazakhstan
Correspondence to: D. Pancheva (ddp@aber.ac.uk)
Abstract. The basic aim of this ‘case
study’ is to investigate the variability in the maximum height of the
ionospheric F2-layer, hmF2, with periods of planetary waves (2–30
days), and to make an attempt to determine their origin. The hourly data of hmF2
above Millstone Hill (42.6° N, 71.5° W) during 01 September 1998 - 31 March
2000 were used for analysis. Three types of disturbances are studied in detail:
(i) the 27- day oscillations observed in the hmF2 above Millstone Hill
are generated by the geomagnetic activity and by the global-scale 27-day wave
present in the zonal mesosphere/lower thermosphere (MLT) neutral wind. The time
delay between the 27-day oscillation in the zonal wind and that in the hmF2
is found to be 5–6 days, while between the 27-day oscillation in the
geomagnetic activity and that in the hmF2 is found to be 0.8–1 day;
(ii) the 16-day oscillation in the hmF2 observed during summer 1999 is
probably generated by the global scale 16-day modulation of the semidiurnal
tide observed in the MLT region during PSMOS campaign in June–August. We
found that if the modulated semidiurnal tide mediates the planetary wave
signature in the ionosphere, this planetary wave oscillation has to be best
expressed in the amplitude and in the phase of the 12-h periodicity of the
ionosphere; and (iii) the third type of disturbances studied is the quasi-2-
day activity in the hmF2 that increases during geomagnetic disturbances.
The strong pseudo diurnal periodicities generated during the geomagnetic storms
can interact between each other and produce the quasi-2-day oscillations in the
ionosphere.
Key words. Ionosphere (ionosphere-atmosphere
interactions; ionosphere-magnetoshpere interactions; wave propagation)
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