Nocturnal F-region vertical drifts over Waltair

327-332The typical features of the low altitude ionospheric F-region nocturnal vertical drifts over Waltair (17.7°N, 83.3°E) obtained from phase path technique have been explained on the basis of the combined effect of the equatorial electrodynamic drifts and neutral winds. It is felt that the post-sunset vertical drifts are mainly due to electrodynamic effect whereas the drifts during the midnight periods are mainly controlled by neutral winds. This explanation has been substantiated with the support of the existing electrodynamic and neutral wind models available in the literature. The comprehensive annual picture the variation of nocturnal vertical drifts over Waltair has been reported