The Naval Research Laboratory (NRL) has developed a new three-dimensional code to study equatorial spread F (ESF). The code is based on the comprehensive NRL 3D ionosphere model SAMI3 and includes a potential equation to self-consistently solve for the electric field. The model assumes equipotential field lines so a 2D electrodynamic problem is considered. In this study a narrow wedge of the post-sunset ionosphere is simulated. It is found that (1) bubbles can rise to ∼1600 km, (2) extremely steep ion density gradients can develop in both longitude and latitude, (3) upward plasma velocities approach 1 km/s, and (4) the growth time of the instability is ≃15 min. These results are shown to be consistent with radar and satellite observations.