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| Titel |
Enhanced ion acoustic fluctuations and ion outflows |
| VerfasserIn |
F. R. E. Forme, D. Fontaine |
| 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. 2 ; Nr. 17, no. 2, S.182-189 |
| Datensatznummer |
250013671
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| Publikation (Nr.) |
 copernicus.org/angeo-17-182-1999.pdf |
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| Zusammenfassung |
A number of observations showing enhanced ion
acoustic echoes observed by means of incoherent scatter radars have been
reported in the literature. The received power is extremely enhanced by up to 1
or 2 orders of magnitude above usual values, and it is mostly contained in one
of the two ion acoustic lines. This spectral asymmetry and the intensity of the
received signal cannot be resolved by the standard analysis procedure and often
causes its failure. As a result, and in spite of a very clear spectral
signature, the analysis is unable to fit the plasma parameters inside the
regions of ion acoustic turbulence. We present European Incoherent Scatter radar
(EISCAT) observations of large ion outflows associated with the simultaneous
occurrence of enhanced ion acoustic echoes. The ion fluxes can reach 1014
m-2 s-1 at 800 km altitude. From the very clear spectral
signatures of these echoes, a method is presented to extract estimates of the
electron temperature and the ion drift within the turbulent regions. It is shown
that the electron gas is strongly heated up to 11 000 K. Also electron
temperature gradients of about 0.02 K/m exist. Finally, the estimates of the
electron temperature and of the ion drift are used to study the possible
implications for the plasma transport inside turbulent regions. It is shown that
strong electron temperature gradients cause enhancement of the ambipolar
electric field and can account for the observed ion outflows.
Key words. Ionosphere (auroral ionosphere; ionosphere
· magnetosphere interactions; plasma waves and instabilities). |
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