The neutral winds in the E and F regions are the drivers of the low-latitude ionospheric current system and observed electric field structure. A flux-tube-integrated model of ionospheric electrodynamics is used to examine three proposed causes of the prereversal enhancement of the zonal electric field. All three mechanisms try to define the obscure relationship between the F region dynamo and the evening prereversal enhancement. The results show that the original mechanism proposed by Rishbeth [1971> is the fundamental mechanism. The rapid change in the vertical polarization electric field near local sunset, which is due to the accelerating neutral wind dynamo, produces a corresponding change in the zonal electric field through curl-free requirements. The other two mechanisms do not produce the evening enhancement but alter the enhancement shape and magnitude. ¿ 1998 American Geophysical Union