Comparison of short period TID morphologies in Antarctica during geomagnetically quiet and active intervals

Travelling ionospheric disturbances with periods in the range 10 < τ < 30 min were observed by an HF Doppier network on the Antarctic Peninsula. A distinction was made between TIDs associated with geomagnetically quiet and active intervals, in the expectation that their morphology might depend on the degree of magnetic activity. During quiet times the short period TIDs have speeds less than 300 m s−1 and may be classified as Medium Scale TIDs. An anticlockwise diurnal azimuth rotation is established, with waves tending to propagate in the (modelled) antiwindward direction. Waves associated with magnetically active intervals often have high speeds and do not generally conform to the simple azimuth variation described above. These differences are explained in terms of perturbed neutral wind patterns and the existence of different wave sources during active times. These observations are presented in the context of previous morphological wave studies. The geomagnetic dependence observed in Antarctica may explain some of the conflicting or ambiguous conclusions resulting from investigations at other locations.

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