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Ann. Geophys., 23, 1199-1206, 2005
www.ann-geophys.net/23/1199/2005/
© European Geosciences Union 2005
The dayside high-latitude trough under quiet geomagnetic conditions: Radio tomography and the CTIP model
S. E. Pryse1, K. L. Dewis1, R. L. Balthazor2, H. R. Middleton1, and M. H. Denton1,3
1Institute of Mathematical and Physical Sciences, University of Wales Aberystwyth, UK
2Department of Applied Mathematics, University of Sheffield, UK
3Now at: Los Alamos National Laboratory, USA
Abstract. The dayside high-latitude trough is a persistent feature of the post-noon
wintertime auroral ionosphere. Radio tomography observations have been used
to map its location and latitudinal structure under quiet geomagnetic
conditions (Kp≤2) near winter solstice. The trough is also a clear
feature in the ion density distribution of the Coupled
Thermosphere-Ionosphere-Plasmasphere model (CTIP) under similar geophysical
conditions. Comparisons of the measured and modelled distributions show that
the plasma production equatorward of the trough is mainly controlled by
solar radiation, but there are also other processes maintaining the
equatorward trough-wall that are open to debate. The poleward trough-wall is
produced by particle precipitation, but the densities are significantly
overestimated by the model. At the trough minimum the observed densities are
consistent with low nighttime densities convecting sunward to displace the
higher daytime densities, but this is not borne out by the CTIP model. The
study shows the potential of combining radio tomography and modelling to
interpret the balance of the physical processes responsible for large-scale
structuring of the high-latitude ionosphere, and highlights the role of
tomographic imaging in validating and developing physical models.
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