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| Titel |
Phenomena induced by powerful HF pumping towards magnetic zenith with a frequency near the F-region critical frequency and the third electron gyro harmonic frequency |
| VerfasserIn |
N. F. Blagoveshchenskaya, H. C. Carlson, V. A. Kornienko, T. D. Borisova, M. T. Rietveld, T. K. Yeoman, A. Brekke |
| 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 ; 27, no. 1 ; Nr. 27, no. 1 (2009-01-08), S.131-145 |
| Datensatznummer |
250016362
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| Publikation (Nr.) |
 copernicus.org/angeo-27-131-2009.pdf |
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| Zusammenfassung |
| Multi-instrument observational data from an experiment on
13 October 2006 at the EISCAT/HEATING facility at Tromsø, Norway are
analysed. The experiment was carried out in the evening hours when the
electron density in the F-region dropped, and the HF pump frequency fH
was near and then above the critical frequency of the F2 layer. The
distinctive feature of this experiment is that the pump frequency was just
below the third electron gyro harmonic frequency, while both the HF pump
beam and UHF radar beam were directed towards the magnetic zenith (MZ). The
HF pump-induced phenomena were diagnosed with several instruments: the
bi-static HF radio scatter on the London-Tromsø-St. Petersburg path,
the CUTLASS radar in Hankasalmi (Finland), the European Incoherent Scatter
(EISCAT) UHF radar at Tromsø and the Tromsø ionosonde (dynasonde). The
results show thermal electron excitation of the HF-induced striations seen
simultaneously from HF bi-static scatter and CUTLASS radar observations,
accompanied by increases of electron temperature when the heater frequency
was near and then above the critical frequency of the F2 layer by up to 0.4 MHz.
An increase of the electron density up to 25% accompanied by strong
HF-induced electron heating was observed, only when the heater frequency was
near the critical frequency and just below the third electron gyro harmonic
frequency. It is concluded that the combined effect of upper hybrid
resonance and gyro resonance at the same altitude gives rise to strong
electron heating, the excitation of striations, HF ray trapping and
extension of HF waves to altitudes where they can excite Langmuir turbulence
and fluxes of electrons accelerated to energies that produce ionization. |
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