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| Titel |
The role played by thermal feedback in heated Farley-Buneman waves at high latitudes |
| VerfasserIn |
J.-P. St.-Maurice, R. S. Kissack |
| 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 ; 18, no. 5 ; Nr. 18, no. 5, S.532-546 |
| Datensatznummer |
250013987
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| Publikation (Nr.) |
 copernicus.org/angeo-18-532-2000.pdf |
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| Zusammenfassung |
It is becoming increasingly clear that
electron thermal effects have to be taken into account when dealing with the
theory of ionospheric instabilities in the high-latitude ionosphere.
Unfortunately, the mathematical complexity often hides the physical processes at
work. We follow the limiting cases of a complex but systematic generalized fluid
approach to get to the heart of the thermal processes that affect the stability
of E region waves during electron heating events. We try to show as
simply as possible under what conditions thermal effects contribute to the
destabilization of strongly field-aligned (zero aspect angle) Farley-Buneman
modes. We show that destabilization can arise from a combination of (1) a
reduction in pressure gradients associated with temperature fluctuations that
are out of phase with density fluctuations, and (2) thermal diffusion, which
takes the electrons from regions of enhanced temperatures to regions of negative
temperature fluctuations, and therefore enhanced densities. However, we also
show that, contrary to what has been suggested in the past, for modes excited
along the E0×B direction thermal feedback decreases
the growth rate and raises the threshold speed of the Farley-Buneman
instability. The increase in threshold speed appears to be important enough to
explain the generation of `Type IV' waves in the high-latitude ionosphere.
Key words: Ionosphere (auroral ionosphere; iono-
spheric irregularities; plasma waves and instabilities) |
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