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Excitation thresholds of field-aligned irregularities and associated ionospheric hysteresis at very high latitudes observed using SPEAR-induced HF radar backscatter
journal contribution
posted on 2010-07-14, 13:47 authored by D. M. Wright, R. S. Dhillon, Tim K. Yeoman, T. R. Robinson, E. C. Thomas, L. J. Baddeley, S. ImberOn 10 October 2006 the SPEAR high power radar facility was operated in a power-stepping mode where both CUTLASS radars were detecting backscatter from the SPEAR-induced field-aligned irregularities (FAIs). The effective radiated power of SPEAR was varied from 1–10 MW. The aim of the experiment was to investigate the power thresholds for excitation (Pt) and collapse (Pc) of artificially-induced FAIs in the ionosphere over Svalbard. It was demonstrated that FAI could be excited by a SPEAR ERP of only 1 MW, representing only 1/30th of SPEAR's total capability, and that once created the irregularities could be maintained for even lower powers. The experiment also demonstrated that the very high latitude ionosphere exhibits hysteresis, where the down-going part of the power cycle provided a higher density of irregularities than for the equivalent part of the up-going cycle. Although this second result is similar to that observed previously by CUTLASS in conjunction with the Tromsø heater, the same is not true for the equivalent incoherent scatter measurements. The EISCAT Svalbard Radar (ESR) failed to detect any hysteresis in the plasma parameters over Svalbard in stark contract with the measurements made using the Tromsø UHF.
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Citation
Annales Geophysicae, 2009, 27 (7), pp. 2623-2631.Published in
Annales GeophysicaePublisher
Copernicus Publications on behalf of the European Geosciences Union (EGU)issn
0992-7689Copyright date
2009Available date
2010-07-14Publisher DOI
Publisher version
http://www.ann-geophys.net/27/2623/2009/Language
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