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| Titel |
Enhanced ion acoustic lines due to strong ion cyclotron wave fields |
| VerfasserIn |
H. Bahcivan, R. Cosgrove |
| 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 ; 26, no. 8 ; Nr. 26, no. 8 (2008-07-31), S.2081-2095 |
| Datensatznummer |
250016171
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| Publikation (Nr.) |
 copernicus.org/angeo-26-2081-2008.pdf |
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| Zusammenfassung |
| The Fast Auroral Snapshot Explorer (FAST)
satellite detected intense and coherent 5–20 m electric field
structures in the high-latitude topside auroral ionosphere between
the altitudes of 350 km and 650 km. These electric fields
appear to belong to electrostatic ion cyclotron (EIC) waves in
terms of their frequency and wavelengths. Numerical simulations of
the response of an electron plasma to the parallel components of
these fields show that the waves are likely to excite a
wave-driven parallel ion acoustic (IA) instability, through the
creation of a highly non-Maxwellian electron distribution function,
which when combined with the (assumed) Maxwellian ion
distribution function provides inverse Landau damping. Because the
counter-streaming threshold for excitation of EIC waves is well
below that for excitation of IA waves (assuming Maxwellian
statistics) our results suggest a possible two step mechanism
for destabilization of IA waves. Combining this simulation result
with the observational fact that these EIC waves share a
common phenomenology with the naturally enhanced IA lines (NEIALS)
observed by incoherent scatter radars, especially that they both
occur near field-aligned currents, leads to the proposition that
this two-step mechanism is an alternative path to NEIALS. |
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