AbstractOn 12 November 2001, artificial optical annuli were produced using the EISCAT high-frequency (HF) ionospheric heating facility. This unusual phenomenon was induced using O-mode transmissions at 5.423MHz with 550MW effective isotropic radiated power and the pump beam dipped 9° south of the zenith. The pump frequency corresponds to the fourth electron gyroharmonic frequency at 215km altitude. The EISCAT UHF radar observed a persistent pump-induced enhancement in the ion line backscatter power near the HF reflection altitude. The optical and radar signatures of HF pumping started at ∼230km and descended to ∼220km within ∼60s. This effect has been modelled using the solution to differential equations describing pump-induced electron temperature and density perturbations. The decrease in altitude of the ion line by ∼10km and changes in electron density have been modelled. The results show that a maximum electron temperature enhancement of up to ∼5700K can be achieved on average, which is not sufficient to explain the observed optical emissions.
Heater-induced altitude descent of the EISCAT UHF ion line enhancements: Observations and modelling
Advances in Space Research ; 38 , 11 ; 2645-2652
2005-06-23
8 pages
Aufsatz (Zeitschrift)
Elektronische Ressource
Englisch
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