The effects of attachment rate on the evolution of electron depletions produced during ionospheric electron attachment chemical releases are studied by using a numerical simulation model. Varying the attachment rate is observed to have important effects on small-scale processes in the depletion boundary layer as well as the large-scale evolution of the depletion. Increasing the attachment rate is observed to increase the amplitude of electrostatic waves in the depletion boundary. The increase in amplitude of these waves is accompanied by an increase in heating of negative ions produced by the electron attachment. Also, the wavelength of waves in the boundary layer is seen to decrease as the attachment rate increases, since steeper density gradients and more highly sheared electron flows are produced. This result indicates that the attachment rate and the size of the release are important factors in setting the scale size of irregularities during the experiments.¿ 1997 American Geophysical Union