2011 SuperDARN Workshop       

Coincident multi-point observations of the E- and F-region decametre-scale plasma waves at high latitudes

B.A. Carter (1,2), R.A. Makarevich (1,3) and J.C. Devlin (1)
(1) School of Engineering and Statistical Mathematics, La Trobe University, Bundoora, Victoria 3086, Australia
(2) now at: School of Mathematical and Geospatial Sciences, RMIT University, Melbourne, Victoria 3000, Australia
(3) now at: Geophysical Institute, University of Alaska Fairbanks, Faibanks AK 99775-7320, USA

abstract. Presented is a detailed analysis of the E-region backscatter observed by the PolarDARN component of the Super Dual Auroral Radar Network (SuperDARN). The statistical occurrence characteristics of the short-range echoes reveal significant differences from those of the auroral and sub-auroral SuperDARN radars. In particular, most backscatter is detected in the midnight sector in the closest range gates where the geometric aspect angles are quite large. One explanation offered is that layers of intense plasma density significantly refract the radar waves allowing the regular detection of plasma waves in the very short ranges. An analysis of the statistical echo types within the PolarDARN dataset showed similarities with the other SuperDARN radars, with the low-velocity echoes dominating both PolarDARN radar datasets. The high-velocity echoes were observed rather sporadically throughout the morning sector, during which the flow and aspect angles are expected to be small enough for routine backscatter to occur. The locations of the PolarDARN radars relative to the more-equatorward SuperDARN radars results in a new experimental setup that has coincident and simultaneous HF radar coverage of the E and F regions along connecting magnetic field lines. In this radar configuration, the SuperDARN plasma flow measurements are employed to investigate the E-region phase velocity dependence on the electric field strength and the flow angle at multiple locations. By employing elevation angle estimates, a marked decrease in the observed phase velocity with decreasing altitude is observed and is attributed to an increased number of collisions between the charged particles and the neutrals. It is also shown that the measured phase velocity normalised to the background plasma flow is smaller for higher electric fields, compared to that for smaller electric fields. This result is interpreted as being due to a change in the contribution of the convective effects on the plasma wave growth.

Sakaguchi KaoriNICT Japan