Equatorial plasma bubble zonal velocity height gradient from spaced VHF polarimeter and scanning 630 nm measurements

Abstract

Simultaneous measurements of equatorial ionosphere plasma bubble zonal velocities by two different techniques, namely, an east‐west spaced vhf electronic polarimeter system and an east‐west scan 630nm airglow photometer, carried out over Brazilian low latitude sites, yielded different velocities, but similar local time variation pattern; the polarimeters always measuring higher velocities than the photometer. Based on the difference in the height regions sensitive to the two techniques the results are interpreted as evidence of the presence of a vertical shear in the zonal plasma motion over our low latitude observing site. The results are compared with existing evidences on the velocity shears over the equator as measured by vhf radars and other different techniques. The implications of these results are briefly discussed.