Mesospheric wind observations derived from Super Dual Auroral Radar Network (SuperDARN) HF radar meteor echoes at Halley, Antarctica: Preliminary results

The implementation of a technique to derive mesospheric winds from HF radar observations of meteor echoes at Halley (76°S, 27°W), Antarctica, is described. The meteor echoes are observed at near ranges (less than 400 km) and have characteristics distinctly different from echoes backscattered from plasma irregularities in the E and F regions of the ionosphere. A Lorentzian model is used to fit the echo spectrum. The echo occurrence rate has the diurnal variation expected of meteors with a minimum in the afternoon. There also appears to be an annual variation which may be related to seasonal changes in the atmosphere. At present, results are confined to a single beam; that directed toward the south geographic pole is presented here, as this will give the meridional component of the wind and can be compared with other studies. The meridional wind is found to be dominated by the semidiurnal tide most of the year, with maxima in spring and autumn. Data for May 1996 show that the semidiurnal tide is dominant, but there are significant contributions from the 24-hour and 8-hour tides. A moving window spectral analysis technique allows the temporal behavior of the waves over a 10-day period to be studied. A quasi 2-day wave is observed during this interval, and slight changes of period with time can be observed. Planetary waves with periods of 5 and 10 days are observed during the winter of 1996. The radar has been operating since 1988, and so these data form a substantial and valuable database of mesospheric observations in the high-latitude southern hemisphere.

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