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| Titel |
Parametric decay of beam-driven Langmuir wave and enhanced ion-acoustic fluctuations in the ionosphere: a weak turbulence approach |
| VerfasserIn |
F. R. E. Forme |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 17, no. 9 ; Nr. 17, no. 9, S.1172-1181 |
| Datensatznummer |
250013810
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| Publikation (Nr.) |
 copernicus.org/angeo-17-1172-1999.pdf |
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| Zusammenfassung |
We present a model that describes the decay
of beam generated Langmuir waves into ion-acoustic waves in the topside
ionosphere. This calculation is done within the frame of the weak turbulence
approximation. We study the spectral signature of such a process as seen by a
VHF incoherent scatter radar. An incoherent scatter (IS) spectrum is
characterized by two maxima at kradar and -kradar,
the right and left ion lines respectively. It is shown that, for reasonable beam
parameters, the parametric decay of beam-generated Langmuir waves can enhance
either the right, the left or both ion lines simultaneously. The shape of the
spectrum can change drastically on time scale of about 0.1 to 1 s. The role of
the beam parameter as well as the ionospheric parameters is also investigated.
For a given beam number density, the beam energy or the background density are
important to trigger either the left or the right ion line. A large energy
spread of the beam or low electron collision frequencies can explain the
simultaneous observations of the left and the right ion line. The importance of
the electron collision frequency can explain the altitude distribution of the
coherent echoes observed by incoherent scatter radars.
Key words. Ionosphere (plasma waves and instabilities)
· Space plasma physics (waves and instabilities; wave-wave interactions) |
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