MULTIRADAR OBSERVATIONS OF MEDIUM-SCALE ACOUSTIC-GRAVITY WAVES USING THE SUPER DUAL AURORAL RADAR NETWORK

Observations of medium-scale acoustic gravity waves in the thermospher e, using multiple HF radars, are presented. Examples of waves from a m agnetically quiet interval and a more magnetically active interval are examined along with statistics of gravity wave occurrence. It is show n that during quiet intervals gravity wave phase fronts may extend lon gitudinally for more than 3400 km. During the more active interval, th e level of wave activity is elevated to the point that it is difficult to distinguish individual wave packets. Also, power spectra from the active period showed evidence of a harmonic sequence, indicating the p ossibility of some nonlinear process acting as the gravity waves propa gate. Statistics of occurrence showed that high-latitude medium-scale gravity waves are more likely in the winter than in the summer and tha t the probability of observing waves on multiple radars is essentially the same as observing waves on any one radar.