Vertical velocities and momentum fluxes derived from wind measurements in the dusk auroral oval

Abstract

On March 20, 1985, simultaneous E region neutral wind measurements were made using the chemical release technique at three separate locations over a triangular region with sides of ∼150 km in the dusk auroral oval. Combining the three wind profiles has allowed us to calculate the divergence and vorticity over the area. The mass continuity equation has been used to calculate the vertical velocity over the height range, and the combination of the horizontal wind measurements and calculated vertical velocities has been used to derive the instantaneous vertical momentum fluxes in the E region. These are the first measurements of these quantities that we are aware of covering the range between 100‐ and 160‐km altitude. The results show a vertical profile of the vertical velocities characterized by peak magnitudes of ∼1.5 m s−1. The direction is downward below 110 km and upward above. The instantaneous zonal momentum flux is downward throughout the region, and the meridional flux is upward. The vertical gradients in the instantaneous momentum flux imply accelerations of the order of 10–50 m s−1 h−1. The results indicate that there is strong coupling between the layers in the E region and that the momentum flux induced accelerations are at least comparable in magnitude to the pressure gradient and Coriolis force accelerations.