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Ann. Geophys., 18, 1182-1196, 2000
www.ann-geophys.net/18/1182/2000/
© European Geosciences Union 2000

More evidence for a planetary wave link with midlatitude E region coherent backscatter and sporadic E layers

M. Voiculescu¹, C. Haldoupis², D. Pancheva³, M. Ignat⁴, K. Schlegel⁵, and S. Shalimov^6
1Physics Department, University of Galati, Galati, Romania
²Physics Department, University of Crete, Iraklion, Crete, Greece
³The Department of Physics, University of Wales, Aberystwyth, Wales, UK
⁴Physics Department, University of Iasi, Iasi, Romania
⁵Max-Planck Institut fur Aeronomie, Katlenburg-Lindau, Germany
⁶Institute of Physics of the Earth, Moscow, Russia

Abstract. Measurements of midlatitude E region coherent backscatter obtained during four summers with SESCAT, a 50 MHz Doppler system operating in Crete, Greece, and concurrent ionosonde recordings from the same ionospheric volume obtained with a CADI for one of these summers, are used to analyse the long-term variability in echo and E_s occurrence. Echo and E_s layer occurrences, computed in percent of time over a 12-h nighttime interval, take the form of time sequences. Linear power spectrum analysis shows that there are dominant spectral peaks in the range of 2–9 days, the most commonly observed periods appearing in two preferential bands, of 2–3 days and 4–7 days. No connection with geomagnetic activity was found. The characteristics of these periodicities compare well with similar properties of planetary waves, which suggests the possibility that planetary waves are responsible for the observed long-term periodicities. These findings indicate also a likely close relation between planetary wave (PW) activity and the well known but not well understood seasonal E_s dependence. To test the PW postulation, we used simultaneous neutral wind data from the mesopause region around 95 km, measured from Collm, Germany. Direct comparison of the long-term periodicities in echo and E_s layer occurrence with those in the neutral wind show some reasonable agreement. This new evidence, although not fully conclusive, is the first direct indication in favour of a planetary wave role on the unstable midlatitude E region ionosphere. Our results suggest that planetary waves observation is a viable option and a new element into the physics of midlatitude E_s layers that needs to be considered and investigated.

Key words: Ionosphere (ionosphere irregularities; mid-latitude ionosphere) – Meteorology and atmospheric dynamics (waves and tides)

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Citation: Voiculescu, M., Haldoupis, C., Pancheva, D., Ignat, M., Schlegel, K., and Shalimov, S.: More evidence for a planetary wave link with midlatitude E region coherent backscatter and sporadic E layers, Ann. Geophys., 18, 1182-1196, 2000.   Bibtex   EndNote   Reference Manager