The role of the equatorial electrojet in the evening ionosphere

The role of the equatorial E region in the electrodynamics of the evening ionosphere is examined. It is proposed that the equatorial electrojet current near sunset has a significant role in the determination of the post sunset enhancement of the horizontal electric field. The electrojet region provides the best avenue for current to be channeled from the dayside to meet the vertical current demands of the F region neutral wind dynamo after sunset. The conductivity reduction in the E region due to the recombination of ionization and the plasma uplift enhances the horizontal (eastward) electric field and thereby increases the speed of the uplift. Thus, the dynamic adjustment of ionization has an unstable, feedback relationship with the electrical fields which may explain the night to night variability of the horizontal electric field enhancement.