Gravity wave observations at a southern hemisphere mid-latitude station using the total electron content technique

Abstract

The work reported here is based on the determination of the horizontal phase trace velocity of travelling ionospheric disturbances (TID's), by using observations recorded from December 1975 to October 1976 of the Faraday rotation of a VHF signal recorded on a spaced array of three receivers located at 37°S, 144°E. The speeds, azimuths, periods and times of occurrence of these disturbances were consistent with the observation of medium scale F-region TID's. Large numbers of daytime disturbances were seen moving zonally, suggesting the influence of the prevailing background winds. Directional filtering of TIDs caused by winds, which has been reported in the northern hemisphere, was observed for the southern hemisphere. As expected for southern hemispheric observations, the observed swing was anti-clockwise. This effect was maintained most obviously during the night, and was in evidence for individual seasons. TID's percentage and absolute amplitude were highly correlated with the disturbance period but had no significant relationship with either jetstream proximity or magnetic activity. Magnetic activity was however, positively correlated with TID speed. The wave periods observed tended to decrease with increasing distance from the jetstream. Disturbances observed when f{hook}oF2 was above its mean had larger amplitudes than TID's recorded under low f{hook}oF2 conditions. © 1978.