Theory for modeling the equatorial evening ionosphere and the origin of the shear in the horizontal plasma flow

Equations describing the time evolution of the equatorial ionosphere are developed using flux tube integrated and flux tube weighted quantities which model the chemistry, dynamics and electrodynamics of the equatorial ionosphere. The resulting two dimensional set of equations can be used to investigate equatorial electric fields neglecting small scale phenomena. An immediate result derived from the integrated current equations is an equation describing the physics of the shear in the horizontal flow of the equatorial plasma during the evening hours. The profile of the horizontal flow has three imortant contributing terms relating to the neutral wind dynamo, Hall conduction, and the equatorial electrojet current divergence. Using a one dimensional model of the velocity shear equation and the integrated ionospheric transport equations, a time history of the development of the shear feature during post sunset hours is presented. The one dimensional model results are compared to the velocity shear measurements from the colored bubbles experiments.