The NRL three‐dimensional ionospheric simulation code SAMI3 is used to model the onset and evolution of equatorial spread F (ESF). SAMI3 is a comprehensive ionosphere model that has been modified to self‐consistently solve for the global neutral wind driven dynamo electric field as well as the gravity driven electric field associated with plasma bubbles. The latter is achieved with a high resolution longitudinal grid in the pre‐ to post‐sunset sector (i.e., 1630 MLT–2230 MLT). Initial results from the new simulation model are presented. It is shown that ESF can be triggered by pre‐sunset ionospheric density perturbations, and that an existing ESF bubble can trigger a new bubble.