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| Titel |
Artificial optical emissions at HAARP for pump frequencies near the third and second electron gyro-harmonic |
| VerfasserIn |
M. J. Kosch, T. Pedersen, J. Hughes, R. Marshall, E. Gerken, A. Senior, D. Sentman, M. McCarrick, F. T. Djuth |
| 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 ; 23, no. 5 ; Nr. 23, no. 5 (2005-07-27), S.1585-1592 |
| Datensatznummer |
250015248
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| Publikation (Nr.) |
 copernicus.org/angeo-23-1585-2005.pdf |
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| Zusammenfassung |
| High-power high-frequency radio waves beamed into the ionosphere cause
plasma turbulence, which can accelerate electrons. These electrons collide
with the F-layer neutral oxygen causing artificial optical emissions
identical to natural aurora. Pumping at electron gyro-harmonic frequencies
has special significance as many phenomena change their character. In
particular, artificial optical emissions become strongly reduced for the
third and higher gyro-harmonics. The High frequency Active Auroral Research
Program (HAARP) facility is unique in that it can select a frequency near
the second gyro-harmonic. On 25 February 2004, HAARP was operated near the
third and passed through the second gyro-harmonic for the first time in a
weakening ionosphere. Two novel observations are: firstly, a strong
enhancement of the artificial optical emission intensity near the second
gyro-harmonic, which is opposite to higher gyro-harmonics; secondly, the
optical enhancement maximum occurs for frequencies just above the second
gyro-harmonic. We provide the first experimental evidence for these effects,
which have been predicted theoretically. In addition, irregular optical
structures were created when the pump frequency was above the ionospheric
critical frequency. Keywords. Active experiments – Auroral ionosphere –
Wave-particle interactions |
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