Evidence of a role for modulated atmospheric tides in the dependence of sporadic E layers on planetary waves
Pancheva, D., Haldoupis, C., Meek, C. E., Manson, A. H. and Mitchell, N. J., 2003. Evidence of a role for modulated atmospheric tides in the dependence of sporadic E layers on planetary waves. Journal of Geophysical Research, 108 (A5).
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 A large amplitude, 7-day period westward propagating S = 1 planetary wave (PW) of global response has been reported from ground radar and satellite wind measurements in the mesosphere-lower thermosphere (MLT) during the second half of August and well into September 1993. Following recent suggestions that PW might play a role in the formation of midlatitude sporadic E layers (E-s), Haldoupis and Pancheva  found a strong 7-day periodicity present in all stations concurrently with the 7-day planetary wave reported elsewhere, by analyzing sporadic E critical frequency (foEs) time series from eight midlatitude ionosonde stations covering a longitudinal zone from about 58 degreesE to 157 degreesW. This study provided the first direct proof in favor of a PW role on E-s formation. In the present paper we further investigate this role by considering the same PW event and correlating the 7-day periodicity in foEs directly with concurrent variations in the mesospheric neutral wind measured with atmospheric radars in Saskatoon, Canada, and in Sheffield, United Kingdom. Although our analysis cannot exclude a direct PW role on E-s formation, it shows clearly that E-s is affected indirectly by the PW through the action of the diurnal and semidiurnal tides which are strongly modulated by the same PW, apparently through a nonlinear interaction process at altitudes below 100 km. This 7-day PW modulation was found to be clearly present simultaneously in the amplitude of the zonal 12-hour tidal wind, the meridional 24-hour tidal wind, and in both, the 12-hour and 24-hour periodicities which existed in the foEs time series. The results here provide a new physical explanation for the observed relation between sporadic E layers and planetary waves.
|Creators||Pancheva, D., Haldoupis, C., Meek, C. E., Manson, A. H. and Mitchell, N. J.|
|Departments||Faculty of Engineering & Design > Electronic & Electrical Engineering|
|Additional Information||ID number: ISI:000183108300007|
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