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Ann. Geophys., 26, 843-852, 2008
www.ann-geophys.net/26/843/2008/
© European Geosciences Union 2008
Mapping ionospheric backscatter measured by the SuperDARN HF radars – Part 2: Assessing SuperDARN virtual height models
T. K. Yeoman1, G. Chisham2, L. J. Baddeley1, R. S. Dhillon1, T. J. T. Karhunen1, T. R. Robinson1, A. Senior3, and D. M. Wright1
1Dept. of Physics and Astronomy, University of Leicester, University Road, Leicester, LE1 7RH, UK
2British Antarctic Survey, Natural Environment Research Council, High Cross, Madingley Road, Cambridge, CB3 0ET, UK
3Department of Communication Systems, Lancaster University, Lancaster, LA1 4WA, UK
Abstract. The Super Dual Auroral Radar Network (SuperDARN) network
of HF coherent backscatter radars form a unique global diagnostic of
large-scale ionospheric and magnetospheric dynamics in the Northern and
Southern Hemispheres. Currently the ground projections of the HF radar
returns are routinely determined by a simple rangefinding algorithm, which
takes no account of the prevailing, or indeed the average, HF propagation
conditions. This is in spite of the fact that both direct E- and F-region
backscatter and 1½-hop E- and F-region
backscatter are commonly used in geophysical interpretation of the data. In
a companion paper, Chisham et al. (2008) have suggested a new virtual height
model for SuperDARN, based on average measured propagation paths. Over
shorter propagation paths the existing rangefinding algorithm is adequate,
but mapping errors become significant for longer paths where the roundness
of the Earth becomes important, and a correct assumption of virtual height
becomes more difficult. The SuperDARN radar at Hankasalmi has a propagation
path to high power HF ionospheric modification facilities at both Tromsø
on a ½-hop path and SPEAR on a
1½-hop path. The SuperDARN
radar at Þykkvibǽr has propagation paths to both facilities over
1½-hop paths. These paths
provide an opportunity to quantitatively test the available SuperDARN
virtual height models. It is also possible to use HF radar backscatter which
has been artificially induced by the ionospheric heaters as an accurate
calibration point for the Hankasalmi elevation angle of arrival data,
providing a range correction algorithm for the SuperDARN radars which
directly uses elevation angle. These developments enable the accurate
mappings of the SuperDARN electric field measurements which are required for
the growing number of multi-instrument studies of the Earth's ionosphere and
magnetosphere.
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