Based on the occurrence frequency of wave-like structures in 23,691 individual measurements of thermospheric density, we demonstrate that there is no significant hemispherical correlation between satellite--measured thermospheric wave-like structures and the tropospheric vorticity area index in the epoch 1974--1976. However, in the northern polar zone, (60 ¿--90 ¿) N, wave occurrence frequency is greater for large values of the 500 mb vorticity area index.