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Annales Geophysicae An open-access journal of the European Geosciences Union
Ann. Geophys., 25, 1801-1814, 2007
https://doi.org/10.5194/angeo-25-1801-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.
 
29 Aug 2007
EISCAT Svalbard radar observations of SPEAR-induced E- and F-region spectral enhancements in the polar cap ionosphere
R. S. Dhillon, T. R. Robinson, and T. K. Yeoman Department of Physics and Astronomy, University of Leicester, University Road, Leicester, LEI 7RH, UK
Abstract. The Space Plasma Exploration by Active Radar (SPEAR) facility has successfully operated in the high-power heater and low-power radar modes and has returned its first results. The high-power results include observations of SPEAR-induced ion and plasma line spectral enhancements recorded by the EISCAT Svalbard UHF incoherent scatter radar system (ESR), which is collocated with SPEAR. These SPEAR-enhanced spectra possess features that are consistent with excitation of both the purely growing mode and the parametric decay instability. In this paper, we present observations of upper and lower E-region SPEAR-induced ion and plasma line enhancements, together with F-region spectral enhancements, which indicate excitation of both instabilities and which are consistent with previous theoretical treatments of instability excitation in sporadic E-layers. In agreement with previous observations, spectra from the lower E-region have the single-peaked form characteristic of collisional plasma. Our observations of the SPEAR-enhanced E-region spectra suggest the presence of variable drifting regions of patchy overdense plasma, which is a finding also consistent with previous results.

Citation: Dhillon, R. S., Robinson, T. R., and Yeoman, T. K.: EISCAT Svalbard radar observations of SPEAR-induced E- and F-region spectral enhancements in the polar cap ionosphere, Ann. Geophys., 25, 1801-1814, https://doi.org/10.5194/angeo-25-1801-2007, 2007.
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