Ionospheric propagation effects on spectral widths measured by SuperDARN HF radars

SuperDARN HF radars provide a global survey of the large-scale convection transversely to the Earth's mag- netic field in the high-latitude ionosphere. In addition to the mean plasma velocity, this network also provides measure- ments of spectral widths which are related to the level of tur- bulence of the sounded plasma. There is an increasing inter- est in using spectral widths in geophysical studies, since they are used to monitor the footprints of several magnetospheric regions. In the present paper, we show the effect of radio wave propagation through a typical turbulent ionosphere on spectral widths measured by SuperDARN radars. This effect has already been evidenced experimentally in a previous pa- per. Here, we model the effects of meso-scale structures on a radar wave front and study their impact on a typical measure- ment. Numerical simulations reproduce the effect evidenced experimentally and show the role of meso-scale structures (1-10 km) in the systematic bias that affects spectral width values. As in experimental data, this effect is shown to be increasing with decreasing radar frequency.

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