The kinetic structure of a tangential discontinuity interface separating an outflowing unmagnetized plasma from an inflowing, magnetized plasma is studied using 1-D hybrid simulations (particle ions and fluid electrons). By including the effects of an ion-neutral collisional force and plasma loss due to recombination, we conclude that two scale lengths control the structure of the cometary ionopause. The first is related to the ion Larmor radius of the outflowing ions which encounter the magnetic barrier, and the second is related to the balance between the ion-neutral collisional force and the electromagnetic J¿B force. ¿ American Geophysical Union 1991