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Ann. Geophys., 24, 2347-2361, 2006
www.ann-geophys.net/24/2347/2006/
© European Geosciences Union 2006
Effects of high-latitude atmospheric gravity wave disturbances on artificial HF radar backscatter
A. Senior1, M. J. Kosch1, T. K. Yeoman2, M. T. Rietveld3, and I. W. McCrea4
1Dept. of Communication Systems, Lancaster University, Lancaster, LA1 4WA, UK
2Dept. of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK
3EISCAT Scientific Association, Ramfjordmoen, 9027 Ramfjordbotn, Norway
4Space Science and Technology Division, Rutherford Appleton Laboratory, Chilton, OX11 0QX, UK
Abstract. Observations of HF radar backscatter from artificial field-aligned
irregularities in an ionosphere perturbed by travelling disturbances due to
atmospheric gravity waves are presented. Some features of the spatio-temporal
structure of the artificial radar backscatter can be explained in terms of
the distortion of the ionosphere resulting from the travelling disturbances.
The distorted ionosphere can allow the HF pump wave to access upper-hybrid
resonance at larger distances from the transmitter than are normally observed
and can also prevent the pump wave reaching this resonance at close
distances. The variation in altitude of the irregularities sometimes results
in a significant variation in the elevation angle of arrival of the
backscattered signal at the radar implying that the radar "sees" a target
moving in altitude. We suggest that this may be evidence of off-orthogonal
scattering from the irregularities.
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