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Ann. Geophys., 25, 1103-1112, 2007
www.ann-geophys.net/25/1103/2007/
© European Geosciences Union 2007
The effect of subionospheric propagation on whistlers recorded by the DEMETER satellite – observation and modelling
O. E. Ferencz1, Cs. Ferencz1, P. Steinbach2, J. Lichtenberger1, D. Hamar1, M. Parrot3, F. Lefeuvre3, and J.-J. Berthelier4
1Space Research Group, Eötvös University, (Inst. of Geogr. and Earth Sci.), 1117 Budapest, Pázmány P.s. 1/A, Hungary
2MTA-ELTE Research Group for Geology, Geophysics and Space Sciences, 1117 Budapest, Pázmány P.s. 1/A, Hungary
3LPCE/CNRS 3A Avenue de la Recherche, 45071, Orléans, Cedex 2, France
4CETP/IPSL, Observatoire de Saint Maur, 4, Avenue de Neptune, Saint Maur des Fossés, 94107, France
Abstract. During a routine analysis of whistlers on the wide-band VLF recording of the
DEMETER satellite, a specific signal structure of numerous fractional-hop
whistlers, termed the "Spiky Whistler" (SpW) was identified. These signals
appear to be composed of a conventional whistler combined by the compound
mode-patterns of guided wave propagation, suggesting a whistler excited by a
lightning "tweek" spheric. Rigorous, full-wave modelling of tweeks, formed
by the long subionospheric guided spheric propagation and of the impulse
propagation across an arbitrarily inhomogeneous ionosphere, gave an accurate
description of the SpW signals. The electromagnetic impulses excited by
vertical, preferably CG lightning discharge, exhibited the effects of guided
behaviour and of the dispersive ionospheric plasma along their paths. This
modelling and interpretation provides a consistent way to determine the
generation and propagation characteristics of the recorded SpW signals, as
well as to describe the traversed medium.
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