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dc.contributor.authorBrekke, Asgeir
dc.contributor.authorBlagoveshchenskaya, N. F.
dc.contributor.authorCarlson, H. C.
dc.contributor.authorKornienko, V. A.
dc.contributor.authorBorisova, T. D.
dc.contributor.authorRietveld, M. T.
dc.contributor.authorYeoman, T. K.
dc.date.accessioned2010-02-11T13:06:28Z
dc.date.available2010-02-11T13:06:28Z
dc.date.issued2009-01-08
dc.description.abstractMulti-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 ofstriations, 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.en
dc.descriptionThis is the publisher’s version/PDF (published in Annales Geophysicae, an open access journal of the European Geosciences Union)en
dc.format.extent1432592 bytes
dc.format.mimetypeapplication/pdf
dc.identifier.citationAnnales Geophysicae, 27, 131–145, 2009en
dc.identifier.issn0992-7689
dc.identifier.urihttps://hdl.handle.net/10037/2384
dc.identifier.urnURN:NBN:no-uit_munin_2134
dc.language.isoengen
dc.publisherCopernicus Publications on behalf of the European Geosciences Unionen
dc.rights.accessRightsopenAccess
dc.subjectVDP::Mathematics and natural science: 400::Physics: 430::Electronics: 435en
dc.subjectIonosphereen
dc.subjectActive experimentsen
dc.subjectRadio scienceen
dc.subjectNonlinear phenomenaen
dc.subjectVDP::Mathematics and natural science: 400::Physics: 430::Electromagnetism, acoustics, optics: 434en
dc.titlePhenomena induced by powerful HF pumping towards magnetic zenith with a frequency near the F-region critical frequency and the third electron gyro harmonic frequencyen
dc.typeJournal articleen
dc.typeTidsskriftartikkelen
dc.typePeer revieweden


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